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A micro-robot fish with embedded SMA wire actuated flexible biomimetic fin
Abstract
A flexible biomimetic fin propelled micro-robot fish is presented. Fish muscle and the musculature of squid/cuttlefish fin are analyzed firstly. Since the latter one is easier to be realized in the engineering field, it is emulated by biomimetic fin. Shape memory alloy (SMA) wire is selected as the most suitable actuator of biomimetic fin. Elastic energy storage and exchange mechanism is incorporated into the biomimetic fin for efficiency improvement. Furthermore the bending experiments of biomimetic fin were carried out to verify the original ideas and research concepts. Thermal analysis is also conducted to find a proper actuation strategy. Fish swimming mechanism is reviewed as the foundation of the robot fish. A radio frequency controlled micro-robot fish propelled by biomimetic fin was built. Experimental results show that the micro-robot fish can swim straight and turn at different duty ratios and frequencies. Subcarangiform- and carangiform-like swimming modes were realized. The maximum swimming speed and the minimum turning radius reached 112 mm/s and 136 mm, respectively.
... Inspired by the musculature of squid and cuttlefish fins, the design focuses on achieving flexible bending akin to fish and cuttlefish propulsion modes. The biomimetic fin, activated by SMA wires through resistance heating and cooling, exhibits flexible bending to both sides, resembling the caudal fin components of fish [34]. The integration of this biomimetic fin into a micro-robot fish design offers propulsion through flexible bending movements, showcasing efficient biomimicry in underwater locomotion. ...
... Labriform swimmers have poor endurance when using their pectoral fins alone. [34] • Fish microrobots driven by a biomimetic fin modeled after the muscular systems of squids and cuttlefish. • The fin is operated using shape memory alloy (SMA) wires with an elastic substrate and transverse SMA wires resembling muscles. ...
... (a) Squid and (b) cuttlefish. Reprinted from[34], Copyright (2008), with permission from Elsevier. ...
Over the past few years, the research community has witnessed a burgeoning interest in biomimetics, particularly within the marine sector. The study of biomimicry as a revolutionary remedy for numerous commercial and research-based marine businesses has been spurred by the difficulties presented by the harsh maritime environment. Biomimetic marine robots are at the forefront of this innovation by imitating various structures and behaviours of marine life and utilizing the evolutionary advantages and adaptations these marine organisms have developed over millennia to thrive in harsh conditions. This thorough examination explores current developments and research efforts in biomimetic marine robots based on their propulsion mechanisms. By examining these biomimetic designs, the review aims to solve the mysteries buried in the natural world and provide vital information for marine improvements. In addition to illuminating the complexities of these bio-inspired mechanisms, the investigation helps to steer future research directions and possible obstacles, spurring additional advancements in the field of biomimetic marine robotics. Considering the revolutionary potential of using nature's inventiveness to navigate and thrive in one of the most challenging environments on Earth, the conclusion of the current review urges a multidisciplinary approach by integrating robotics and biology. The field of biomimetic marine robotics not only represents a paradigm shift in our relationship with the oceans, it also opens previously unimaginable possibilities for sustainable exploration and use of marine resources by understanding and imitating nature's solutions.
... For example, Rossi et al proposed a new concept [96], using a Vshaped SMA wire actuator to form a curved continuous flexible structure to imitate the spine of a robotic fish (figure 10(a)) to drive an underwater fish-like swimming robot. Wang et al designed a micro robotic fish driven by a flexible-driven bionic fin (figure 10(b)) [97], in which SMA wire was selected as the bionic fin actuator. This bionic fin had soft bending characteristics similar to that of squid muscles. ...
... Swimming robots based on SMA artificial muscles. (a) Fish-like robot [96]; (b) Biomimetic fin [97] (c) Bionic turtle robot [98]; (d) Bionic starfish robot [100]; (e) Bionic jellyfish robot (Robojelly) [104]; (f) Bionic seal robot (SEALicone) [106]. ...
... All rights reserved. (b) Biomimetic fin [97]. Reprinted from [97], Copyright © 2008 Elsevier B.V. All rights reserved. ...
As an important part of soft robots, artificial muscles have received increasing attention. And since artificial muscles are developed by imitating the characteristics of biological muscles, they are naturally suitable for bionic applications. Shape memory alloys (SMAs) have been widely used in the field of artificial muscles due to their high energy density, biocompatibility, corrosion resistance, and self-sensing properties. In this review, the bionic applications of SMA artificial muscles are classified and summarized, and they are divided into two categories: bionic robotics (animal imitation) and biomedical (human imitation) applications. In the part of bionic robots, we summarize the applications of SMA artificial muscles in bionic robots such as flying, jumping, walking, crawling and swimming robots according to the motion characteristics. In the part of biomedical applications, we summarize the applications of SMA artificial muscles in various parts of the human body. In addition, this review also counts the proportion of SMA wires and springs used in applications, and provides a reference for the subsequent selection of SMA wires and springs. Finally, the challenges and opportunities of SMA artificial muscles are summarized and prospected.
... The model achieved a maximum speed of 0.026 m·s −1 . Manta ray robotic fish were developed by Wang et al. [18]. Here, stretched SMA wire (0.15 mm) was used to develop a flapping mechanism. ...
... Utilising Equation (18), the area (a f in ) of the fin can also be calculated if the other parameters are known. ...
Shape memory alloys (SMAs) have become the most common choice for the development of mini- and micro-type soft bio-inspired robots due to their high power-to-weight ratio, ability to be installed and operated in limited space, silent and vibration-free operation, biocompatibility, and corrosion resistance properties. Moreover, SMA spring-type actuators are used for developing different continuum robots, exhibiting high degrees of freedom and flexibility. Spring- or any elastic-material-based antagonistic or biasing force is mostly preferred among all other biasing techniques to generate periodic oscillation of SMA actuator-based robotic body parts. In this model-based study, SMA-based spring-type actuators were used to develop a carangiform-type robotic fishtail. Fin size optimization for the maximization of forward thrust was performed for the developed system by varying different parameters, such as caudal fin size, current through actuators, pulse-width modulation signal (PWM), and operating depth. A caudal fin with a mixed fin pattern between the Lunate and Fork “Lunafork” and a fin area of approximately 5000 mm2 was found to be the most effective for the developed system. The maximum forward thrust developed by this fin was recorded as 40 gmf at an operation depth of 12.5 cm in a body of still water.
... 32 The high transparency of flexible PIGs allows the transport of ions without hindering optical signals, expanding their use in flexible electric actuators or light-driven actuators. 33 The easily formed electronic double layer (EDL) and the excellent stretchability in flexible PIGs make them well-suited for applications in flexible power supplies with large deformation as well as in ionic skin. 15,16,34 As depicted in Figure 1, various novel flexible ionic devices have been well developed based on these unique flexible PIGs. ...
... 135 These actuators possess advantageous features such as high stability in air, flexibility, lightweight, ease of preparation, and low cost. Consequently, they hold significant potential for applications in soft robots, 33,[136][137][138] artificial muscles [139][140][141][142] and other related fields. [143][144][145] Based on their distinct working mechanisms, PIG-based actuators can be generally classified into electrically driven and optically driven actuators. ...
Polymer ionogel (PIG) is a new type of flexible, stretchable, and ion‐conductive material, which generally consists of two components (polymer matrix materials and ionic liquids/deep eutectic solvents). More and more attention has been received owing to its excellent properties, such as nonvolatility, good ionic conductivity, excellent thermal stability, high electrochemical stability, and transparency. In this review, the latest research and developments of PIGs are comprehensively reviewed according to different polymer matrices. Particularly, the development of novel structural designs, preparation methods, basic properties, and their advantages are respectively summarized. Furthermore, the typical applications of PIGs in flexible ionic skin, flexible electrochromic devices, flexible actuators, and flexible power supplies are reviewed. The novel working mechanism, device structure design strategies, and the unique functions of the PIG‐based flexible ionic devices are briefly introduced. Finally, the perspectives on the current challenges and future directions of PIGs and their application are discussed.
... Soft material robots include robots with a motor and a soft body [7], robots with a motor/wire mechanism and a soft body [8][9][10], and robots with a tensegrity mechanism that allows the rigidity of the body to be set to an arbitrary value at each body length position [11,12]. Meanwhile, robots have been developed using soft actuators such as pneumatic and hydrodynamic actuators that deform by fluid pressure [13,14]; shape memory alloys (SMA) that shorten by heating [15][16][17][18]; and piezoelectric composite fiber [19], dielectric elastomer actuators (DEA) [20,21], and hydraulically amplified self-healing electrostatic (HASEL) actuators [22] that deform by applying a voltage. ...
... Improved UEC Mackerel 0.11 (0.8 Hz) 0.14 (0.7 Hz) Prototype UEC Mackerel [23] 0.08 (1.3 Hz) 0.08 (0.7 Hz) SMA fish [15] 0.76 (2.5 Hz) 0.30 SMA fish [16] 0.1 (0.5 Hz) 0.20 SMA fish [17] 0.46 (2.25 Hz) 0.20 SMA fish [18] 0.10 (0.5 Hz) 0.20 DEA fish [20] ∼0.07 (3 Hz) 0.023 DEA fish [21] 0.22 (6 Hz) 0.037 FEA fish [13] 0.44 (1.67 Hz) 0.26 ...
Underwater robots are becoming increasingly important in various fields. Fish robots are attracting attention as an alternative to the screw-type robots currently in use. We developed a compact robot with a high swimming performance by mimicking the anatomical structure of fish. In this paper, we focus on the red muscles, tendons, and vertebrae used for steady swimming of fish. A robot was fabricated by replacing the red muscle structure with shape memory alloy wires and rigid body links. In our previous work, undulation motions with various phase differences and backward quadratically increasing inter-vertebral bending angles were confirmed in the air, while the swimming performance in insulating fluid was poor. To improve the swimming performance, an improved robot was designed that mimics the muscle contractions of mackerel using a pulley mechanism, with the robot named UEC Mackerel. In swimming experiments using the improved robot, a maximum swimming speed of 25.8 mm/s (0.11 BL/s) was recorded, which is comparable to that of other soft-swimming robots. In addition, the cost of transport (COT), representing the energy consumption required for robot movement, was calculated, and a minimum COT of 0.08 was recorded, which is comparable to that of an actual fish.
... There are many actuators developing in recent decades [18][19][20] but still there is a limitation for selecting actuators which does not have enough details to select the good actuator for soft grasping with different applications. The pneumatic [21][22][23], electrical [24], and chemical means [25] of actuation are utilized in the operation of these actuators. The primary benefits of SPAs are that it can quickly inflate its pneumatic structure, it is lightweight, and it is simple to control. ...
This study investigates the effects of actuator design parameters on the performance of developed trapezoidal shaped soft pneumatic actuator, optimizes its geometric structure using the finite element method and validates its performance experimentally. To optimize the soft pneumatic actuator, the effects of structural parameters such as wall thickness, gap between the adjacent chambers, passive layer thickness, width of inside chamber and the bending angle of the actuator were evaluated. Finite Element Analysis is used to determine the displacement variation of actuator with different levels of applied pressures. A Global Analysis of Variance was conducted to determine the influence of variables affecting the displacements of soft pneumatic actuator was determined. The ANOVA results, a geometric actuator with a wall thickness of 1.5 mm, gap between chambers of 4 mm, passive layer thickness of 2 mm and the width of inside chamber of 4 mm is recommended for the actuator to be achieve maximum bending angle. The proposed actuator model can be used to select the suitable actuator for grasping soft objects without deformation. In addition, experiment was conducted to correlate the results with finite element analysis data.
... These actuators can achieve large levels of deformation from the neutral (resting) configuration of the structure (Kennedy et al., 2023b). These morphing actuators have been used to replicate the motion of biological structures, such as aquatic animals (Villanueva et al., 2011;Wang et al., 2008Wang et al., , 2009, human fingers (Kim et al., 2016;Rodrigue et al., 2015;Yang and Gu, 2002), medical devices (Chen et al., 2022;Toews, 2004;Veeramani et al., 2008), and crawling robots (Tang et al., 2023). Additionally, bimorph SMA actuators have been shown to be able to increase the operational frequency range of SMA actuators by leveraging the resonance frequency of the passive layer (Kennedy et al., 2020;Song et al., 2016) as well as create micro-positioning systems (Rahbari et al., 2023). ...
Shape memory alloy morphing actuators are a type of composite soft actuator with many attractive properties such as large deformation, small form factor, self-sensing ability, and physical reservoir computing potential. These actuators are composed of active shape memory alloy wires and a passive material to magnify the overall deflection. However, the dynamic modeling of these actuators is difficult due to both shape memory alloy characteristics and the nonlinearity of the passive layer. Here, a hybrid dynamical model is proposed that couples the phase kinetics and thermal modeling for the shape memory alloy with a dynamic Cosserat beam model. This hybrid model is benchmarked against experimental linear and morphing actuators resulting in a root mean squared error of 0.87 mm for the linear actuator and root mean squared error of 1.34 and 1.42 mm for the two morphing actuator configurations evaluated in this work. This model applies continuous phase kinetic equations in a comprehensive hybrid dynamical model to accurately simulate the hysteretic transition of the alloy, which is then coupled to a high deformation beam model. This work can expand the capability and design of novel morphing actuators to achieve specified dynamic characteristics for increased application in robotic fields.
... However, they do have some drawbacks, such as the requirement of high input voltage and additional structures to amplify small deformations. Shape Memory Alloy (SMA) actuators are known for their simple structure and reasonable power output [18], [19], [20], [21], [22]. However, they do come with certain drawbacks, including limited speed and a delayed response. ...
This paper presents the design, modeling, and simulation of a compact Electromagnetic Linear Actuator (ELA) and its application to a linear motion mechanism. The proposed actuator consists of a coil and a permanent magnet and can generate a linear motion when an alternating current is applied to the coil. Its overall dimensions are 20 mm (W) ×15 mm (H) ×15 mm (D) while the weight is 7 g. The proposed actuator can be controlled in terms of position using an open-loop system. A mathematical model is created for the proposed actuator, and theoretical analysis is performed to examine the actuator dynamic model. The simulation results are validated experimentally by manufacturing a physical prototype. Therefore, the proposed actuator generates an electromagnetic force of 0.1 N at 10 V (0.07 A), then our actuator able to achieve a displacement of 0.2 mm. Moreover, the experimental resonance frequency is measured at 70 Hz and the bandwidth of 80 Hz. Finally, the overall system performance is evaluated by integrating the developed actuator into the linear motion mechanism. We investigate the stick-slip motion of the linear mechanism without feedback control, dedicating sufficient time to both the slip phase and the stick phase. The experimental results show that the linear motion mechanism travels with speed 6 mm s−1 with a frequency of 30 Hz.
... Many actuator concepts have been developed in the last two decades, involving SMA as the driving force in the field of soft robotics. Some interesting actuator concepts include crawler robots [13], jumper robots [14], flower robots [15], fish robots [16][17][18], locomotion robots [19], bio-mimetic robotic hand [20], soft robotic tendon grippers [12,21], etc. ...
The growing demand for intelligent systems with improved human-machine interactions has created an opportunity to develop adaptive bending structures. Interactive fibre rubber composites (IFRCs) are created using smart materials as actuators to obtain any desired application using fibre-reinforced elastomer. Shape memory alloys (SMAs) play a prominent role in the smart material family and are being used for various applications. Their diverse applications are intended for commercial and research purposes, and the need to model and analyse these application-based structures to achieve their maximum potential is of utmost importance. Many material models have been developed to characterise the behaviour of SMAs. However, there are very few commercially developed finite element models that can predict their behaviour. One such model is the Souza and Auricchio (SA) SMA material model incorporated in ANSYS, with the ability to solve for both shape memory effect (SME) and superelasticity (SE) but with a limitation of considering pre-stretch for irregularly shaped geometries. In order to address this gap, Woodworth and Kaliske (WK) developed a phenomenological constitutive SMA material model, offering the flexibility to apply pre-stretches for SMA wires with irregular profiles. This study investigates the WK SMA material model, utilizing deformations observed in IFRC structures as a reference and validating them against simulated models using the SA SMA material model. This validation process is crucial in ensuring the reliability and accuracy of the WK model, thus enhancing confidence in its application for predictive analysis in SMA-based systems.
... Electrical driven soft actuators were another big family of artificial muscles, including ionic polymer-metal composites (IPMCs) [8], and DEAs [9], [10], [11]. Heat-driven biomimetic fish with shape memory alloys (SMAs) embedded were also presented in previous works [12], [13]. Since most energy was lost during thermal-mechanical conversion, there is few attempts of SMA robots for long-term usage. ...
... Several soft robotic fishes have been developed in the last decade with smart-material-based actuators, such as ionic polymer-metal composites [12,13], dielectric elastomers [10,[14][15][16], fluidic elastomers [17,18] and Shape Memory Alloy (SMA) wires [19,20]. Compared to robotic fishes using traditional actuators, smart materials endow these soft robots with compactness, flexibility, light weight and multimode movement. ...
In this paper, we present the design, fabrication, locomotion and bionic analysis of a Soft Robotic Fish Actuated by Artificial Muscle (SoRoFAAM). As a carangiform swimmer, the most important part of SoRoFAAM-1, on the motion point of view, is its tail designed around a bidirectional flexible bending actuator by layered bonding technology. This actuator is made of two artificial muscle modules based on Shape Memory Alloy (SMA) wires. Each artificial muscle module has four independent SMA-wire channels and is therefore capable of producing four different actuations. This design allows us to implement an adaptive regulated control strategy based on resistance feedback of the SMA wires to prevent them from overheating. To improve the actuation frequency to 2 Hz and the heat-dissipation ratio by 60%, we developed a round-robin heating strategy. Furthermore, the thermomechanical model of actuator is built, and the thermal transformation is analysed. The relationships between the actuation parameters and SoRoFAAM-1’s kinematic parameters are analysed. The versatility of the actuator endows SoRoFAAM-1 with cruise straight and turning abilities. Moreover, SoRoFAAM-1 has a good bionic fidelity; in particular, a maneuverability of 0.15, a head swing factor of 0.38 and a Strouhal number of 0.61.
... They can exhibit continuum motion that the rigid-bodied robotic fish cannot achieve, all of which contribute to reducing power consumption and swimming efficiency (Dwivedy and Eberhard, 2006). Therefore, compliant robotic fish is an emerging field receiving progressively more attention (Wang et al., 2008;Chen et al., 2009;Masoomi et al., 2014;Zhong et al., 2017). ...
... SMA has a high power density ratio that enables a compact system size. Many researchers have presented various actuators based on SMA wires and used them in various applications [29][30][31][32][33][34][35][36][37][38]. To mimic the contraction-pulse propulsion mode of jellyfish, a novel artificial muscle based on SMA with new processes and parameters to implement reciprocal flapping motion was designed, which achieved a large bending deformation, as shown in Figure 3a. ...
This paper presented a flexible and easily fabricated untethered underwater robot inspired by Aurelia, which is named “Au-robot”. The Au-robot is actuated by six radial fins made of shape memory alloy (SMA) artificial muscle modules, which can realize pulse jet propulsion motion. The thrust model of the Au-robot’s underwater motion is developed and analyzed. To achieve a multimodal and smooth swimming transition for the Au-robot, a control method integrating a central pattern generator (CPG) and an adaptive regulation (AR) heating strategy is provided. The experimental results demonstrate that the Au-robot, with good bionic properties in structure and movement mode, can achieve a smooth transition from low-frequency swimming to high-frequency swimming with an average maximum instantaneous velocity of 12.61 cm/s. It shows that a robot designed and fabricated with artificial muscle can imitate biological structures and movement traits more realistically and has better motor performance.
... These research efforts use either experimental or computational fluid dynamics to measure or calculate the fluid field generated by the fish's body-fin motion and study the underlying vortex formation and dynamics. Inspired by fish locomotion, a variety of robotic fishes for novel underwater propulsion have been proposed, including those with single-joint design [15,16], multi-joint design [17,18] and smart-material-based design [19][20][21]. Fish swimming patterns can be classified into body and/or caudal fin (BCF) locomotion and median and/or paired fin (MPF) locomotion [22]. For BCF locomotion, caudal fins and bodies of fishes are the main thrust generator. ...
Thrust generation is a crucial aspect of fish locomotion that depends on a variety of morphological and kinematic parameters. In this work, the kinematics of caudal fin motion of a robotic fish are optimised experimentally. The robotic fish actuates its caudal fin with flapping and rotation motion, and also measures the fin hydrodynamic force and torque. Total nine designs of the caudal fins are investigated, with three different shapes (or inclination angles) and three stiffness. The optimisation is based on a policy search (PS) algorithm, which is used to maximise the thrust-generation efficiency of the caudal fins. The authors first parametrise fin spanwise-rotation as a sinusoidal function using rotation amplitude and phase delay and test whether it is beneficial to thrust-generation efficiency. The result shows that the rotation does not contribute to the efficiency, as the efficiency is maximised at zero amplitude. Next, the authors optimise flapping amplitude and trajectory profile without fin rotation. Results show that smaller flapping amplitude results in higher efficiency and linear flapping trajectories are preferred over sinusoidal ones. Fins that have the highest flexibility are more efficient in thrust generation although they generate less thrust, while an inclination angle of 30° yields the most efficient fin shape.
... The results in Figs. [8][9][10][11][12] show that this model has comparable predictive performance for all of these cases. ...
Shape memory alloys are metal alloys that have multiple crystalline states, which can be accessed through heating and cooling. These actuators have several attractive properties, such as a high strength-to-weight ratio, robustness, and compact structure. Added to this, shape memory alloys have a self-sensing property. However, shape memory alloy wires typically have a low contraction of only ∼4%-5%. To overcome this shortcoming, shape memory alloy actuators can use a passive base layer in a morphing configuration to amplify the deformation. By including voltage probes at the base of a unimorph shape memory alloy actuator, self-sensing of the actuator's configuration can be achieved, without encumbering the actuator with extra mass or wires. Due to the compact nature of this actuator, the voltage probes are necessarily close together, which drastically increases the errors of the estimated deformations. To correct these large errors, a machine learning approach is used to unlock this self-sensing ability for a compact shape memory alloy actuator. Of note, this approach, instead of being a black box method, builds on a self-sensing theory of shape memory alloys. This method of self-sensing with machine learning calibration is capable of predicting the location of the end of the actuator with less than 3% error, even for large deformations.
... Today Shape Memory Alloys (SMAs) are already commercially applied in many technical fields. SMAs have been developed since the early 1960s, and since then, they have been successfully used for medical [1,2,3], robotic [4,5,6], aerospace [7,8,9], and automobile applications [10,11]. ...
The paper aims to develop a model describing the shape memory deformation in the presence of ultrasonic impulses. The application of ultrasound can be of great importance, primarily when heating the shape memory alloy elements cannot be carried out for many applications. Experimental results record that acoustic waves induce the austenitic transformation, which manifests itself in a jump-wise increment in the deformation as ultrasound is On. The model presented here is constructed in terms of the synthetic theory of irrecoverable deformation. To catch the phenomena caused by acoustic energy, we enter into the basic equation a new term reflecting the effect of ultrasound on the processes governing the phase transformation. The analytical results fit good experimental data.
... In steering experiments, the frame rate of the high-speed camera was set as 1000 frames per second and the robot locations were obtained in every millisecond. 11,12,[19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] In the traces of the copebot's motions, there are steering and rotation motions, which are the results of the specific input parameter (i.e., gas amount and preinclined wing angles.). When the preinclined wing angles are relatively low (e.g., 7.5°-35, 45, and 55 s) or the input gas amount are relatively low (e.g., 35 s-7.5°, 15°, and 22.5°), the robots tend to operate steering motions that can fulfill propulsion requirements. ...
It has been a great challenge to develop robots that are able to perform complex movement patterns with high speed and, simultaneously, high accuracy. Copepods are animals found in freshwater and saltwater habitats that can have extremely fast escape responses when a predator is sensed by performing explosive curved jumps. In this study, we present a design and build prototypes of a combustion-driven underwater soft robot, the "copebot," which, similar to copepods, is able to accurately reach nearby predefined locations in space within a single curved jump. Because of an improved thrust force transmission unit, causing a large initial acceleration peak (850 body length·s-2), the copebot is eight times faster than previous combustion-driven underwater soft robots, while able to perform a complete 360° rotation during the jump. Thrusts generated by the copebot are tested to quantitatively determine the actuation performance, and parametric studies are conducted to investigate the sensitivity of the kinematic performance of the copebot to the input parameters. We demonstrate the utility of our design by building a prototype that rapidly jumps out of the water, accurately lands on its feet on a small platform, wirelessly transmits data, and jumps back into the water. Our copebot design opens the way toward high-performance biomimetic robots for multifunctional applications.
... The complexity of the required heating/cooling systems alongside slow response are additionally delimiting drawbacks of the SMA actuators 23,24 . The proper and expensive thermal control system is essential 25,26 . The heating requirement for SMA elements can limit the application of these actuators to manipulate heat-sensitive biospecimen and live tissues due to lateral thermal damage 27,28 . ...
We have developed a microscale hydraulic soft gripper and demonstrated the handling of an insect without damage. This gripper is built on Polydimethylsiloxane (PDMS) with the soft material casting technique to form three finger-like columns, which are placed on a circular membrane. The fingers have a length of 1.5 mm and a diameter of 300 µm each; the distance between the two fingers is 600 µm of center-to-center distance. A membrane as a 150 µm soft film is built on top of a cylindrical hollow space. Applying pressure to the interior space can bend the membrane. Bending the membrane causes the motion of opening/closing of the gripper, and as a result, the three fingers can grip an object or release it. The PDMS was characterized, and the experimental results were used later in Abaqus software to simulate the gripping motion. The range of deformation of the gripper was investigated by simulation and experiment. The result of the simulation agrees with the experiments. The maximum 543 µN force was measured for this microfluidic-compatible microgripper and it could lift a ball that weighs 168.4 mg and has a 0.5 mm diameter. Using this microgripper, an ant was manipulated successfully without any damage. Results showed fabricated device has great a potential as micro/bio manipulator.
... A significant amount of research has been put into the development of SMA-driven soft-bodied robotic fish. Wang et al. [24], [25] introduced a flexible biomimetic microrobot fish that was driven by its fins and had distinct SMA actuators. We created a swim motion simulator using a flexible silicone tail equipped with a straightforward SMA actuator mechanism and tested it at a number of different frequency levels [26]. ...
span lang="EN-US">In this study, we present the construction of a wireless bionic soft robotic fish that has a silicone tail and uses shape-memory alloys (SMAs) as actuators. Even though there have been a lot of recent advancements in the field of soft robotics, the use of SMAs as actuators for soft robots is still not something that is investigated very often. In the course of this research, we plan to work toward the creation of a realistic bionic fish robot that possesses a high level of mobility in the water, in addition to being light enough, strong enough, and flexible enough. The purpose of this study is to expound on the process of optimizing the morphologies of the fish body, as well as the optimization of the electromechanical behavior of the SMAs, in order to generate swimming motions in the fish. Our attention will be on the optimization of these two aspects. This report also outlines some preliminary but promising physical tests that were conducted to create a robotic fish with the similar shape.</span
... Many micromachines with various locomotion capabilities such as walking, swimming, and flying have been developed [1][2][3][4][5]. These small machines require an optimum design and force control according to their size because of the scale effect. ...
Insects exhibit excellent maneuvers such as running and flying despite their small bodies; therefore, their locomotion mechanism is expected to provide a design guideline for micromachines. Numerical simulations have been performed to elucidate this mechanism, whereby it is important to develop a model that is physically identical to the target insect’s parts to reproduce kinematic dynamics. In particular, in flight, the shape and mass of wings, which flap at high frequencies, are significant parameters. However, small insects such as fruit flies have small, thin, and light wings; thus, their mass cannot be easily measured. In this study, we proposed a high-resolution and simple force plate to measure the mass of each part of a tiny insect. The device consists of a circular plate supported by flat spiral springs made of polyimide film, and a laser displacement meter that detects the displacement of the center of the plate. The simple plate fabrication process requires only a couple of minutes. A fabricated force plate with a sub-N/m spring constant achieved a resolution of less than 2 µg. As a demonstration, the wing mass of the fruit flies was measured. The experimental results suggest that the wings accounted for approximately 0.4% of the body mass.
Biomimetic micro-robot technology based on non-contact and cable-free magnetic actuation has become one of the crucial focuses of future biomedical research and micro-industrial development. Inspired by the motion characteristics of ray fish, this article proposes a micro-robot with magnetic controlled bionic ray structure. The micro-robot is made of soft elastic materials such as poly dimethyl siloxane (PDMS), Ethylene-Propylene-Diene Monomer (EPDM), and magnetic material Neodymium Iron Boron (NdFeB) nanoparticles. The external driving magnetic field is a periodic oscillating magnetic field generated by a Helmholtz coil. In order to verify the feasibility of the ray-inspired micro-robot, the motion principle was analyzed and several experiments were carried out. Experimental results demonstrated that the ray-inspired micro-robot can excellently mimic the crucial swimming characteristics of rays under the driving force of a oscillating magnetic field with an intensity of 5 mT and a frequency of 5 Hz, the swimming speed of the biomimetic micro-robot can reach nearly 2 body lengths per second. Analysis shows that the speed and stability of the micro-robot primarily depends not only on the amplitude and frequency of the vertical oscillating magnetic field, but also on the magnitude of the horizontal uniform magnetic field. This article demonstrates that the designed biomimetic micro-robot has the potential application of remotely performing specialized tasks in confined, complex environments such as microchannel-based scenarios.
This study investigates the effects of actuator design parameters on the performance of developed trapezoidal shaped soft pneumatic actuator, optimizes its geometric structure using the finite element method and validates its performance experimentally. To optimize the soft pneumatic actuator, the effects of structural parameters such as wall thickness, gap between the adjacent chambers, passive layer thickness, width of inside chamber and the bending angle of the actuator were evaluated. Finite Element Analysis is used to determine the displacement variation of actuator with different levels of applied pressures. A Global Analysis of Variance was conducted to determine the influence of variables affecting the displacements of soft pneumatic actuator was determined. The ANOVA results, a geometric actuator with a wall thickness of 1.5 mm, gap between chambers of 4 mm, passive layer thickness of 2 mm and the width of inside chamber of 4 mm is recommended for the actuator to be achieve maximum bend angle. The proposed actuator model can be used to select the suitable actuator for grasping soft objects without deformation. In addition, experiment was conducted to correlate the results with finite element analysis data.
This letter presents the design, fabrication, and performance test of a fish-like underwater miniature robot directly driven by two piezoelectric actuators. Considering the different medium conditions and the ever-present challenge of waterproofing in underwater motion, the miniaturization of underwater robots is regarded as an innovative task. In this work, by mimicking the swing of fish caudal fins to generate thrust, a piezoelectric actuator is used to directly drive the artificial fins. This robot merely consists of six components, including two PZT actuators, a pair of caudal fins, and two glass fiber fixtures. Such a design serves to streamline the process of assembly. The total mass of prototype miniature robot is only 0.8 g and has a body length (BL) of 4 cm. The robot has demonstrated its capacity for flexible and swift underwater movement. It can perform straight and turning movements underwater, with a maximum forward speed of 8.01 BL/s (32.05 cm/s) at a driving voltage of 180 V. It has a maximum payload of 0.84 g and minimum turning radius of 7.9 cm.
Catheter-related biofilm infection remains the main problem for millions of people annually, affecting morbidity, mortality, and quality of life. Despite the recent advances in the prevention of biofilm formation, alternative methods for biofilm prevention or eradication still should be found to avoid traumatic and expensive removal or catheter replacement. Soft magnetic robots have drawn significant interest in favor of remote control, fast response, and wide space for design. In this work, we demonstrated magnetic soft robots as a minimally invasive, safe, and effective approach to eliminate biofilm from urethral catheters (20 Fr or 5.1 mm in diameter). Seven designs of the robot were fabricated (size 4.5 × 15 mm), characterized, and tested in the presence of a rotating magnetic field. As a proof-of-concept, we demonstrated the superior efficiency of biofilm removal on the model of a urethral catheter using a magnetic robot, reaching full eradication for the octagram-shaped robot (velocity 2.88 ± 0.6 mm/s) at a 15 Hz frequency and a 10 mT amplitude. These findings are helpful for the treatment of biofilm-associated catheter contamination, which allows an increase in the catheter wearing time without frequent replacement and treatment of catheter-associated infections.
Recent advances in soft robots have been achieved by using compliant materials and exploiting the advantages of the soft structural designs of living organisms. Living organisms (which have theoretically infinite degrees of freedom) are not only mechanically soft but are also capable of smooth harmonic motions, thanks to global coordination and the individual sensing and control of local tissues. Despite improvements in structural designs, few soft robot control frameworks for global object‐oriented behaviors are reported. Such a framework will require the use of multiple segments, with local sensing and independent control using coordinated policies. Here, a class of reinforcement learning based control frameworks for soft robots (with high degrees of freedom) is presented, and their ability to conduct global tasks is demonstrated. Coordinated control policies are formulated to control multiple segments with independently controllable embedded actuators, based on localized proprioceptive self‐sensing capabilities. The control frameworks are employed to develop soft physical robots. Demonstrations and experiments include the forward and backward locomotion of multichannel soft robotic flatworms. This approach is applicable to multifunctional, high degrees of freedom soft robots, as demonstrated by experiments with light‐sensitive locomotion.
Bionic robotic fish are of great importance in marine resource exploration, military applications and industrial production. However, existing bionic robotic fish often use motor-driven multi-link systems, which are complex and bulky. They are unable to perform narrow underwater operations and industrial pipeline exploration. Therefore, the miniaturization and simplification of bionic robotic fish have become an important research direction for underwater bionic robotic fish. This work reports a miniature robotic fish with a flexible tail fin based on a magnetic actuator (MAGFLE). The flexible tail fin dynamics model of MAGFLE was established and analyzed by numerical simulation to obtain the highest frequency of flexible tail fin propulsion efficiency. A unique magnetic actuator was designed to enable the flexible tail fin to achieve multi-mode motion under magnetic actuation. Thanks to the absence of transmission mechanisms or joints, the design of MAGFLE is notably simplified, resulting in a compact form factor measuring 76x37x40 mm³and weighing a mere 5.6 grams. It accelerates from a standstill and travels up to 181.05 mm s
-1
, which only needs 10 s (approximately 2.4 body lengths per second). The results indicate that the magnetically driven MAGFLE with a flexible tail fin has the advantage of a miniature structure, fast movement, and low noise, which has great potential for application in reconnaissance or exploration missions.
The efficient swimming performance of fish is a miracle of nature, and the bionic robot fish powered by smart materials can replicate the movement pattern of fish to a greater extent. To achieve a simple, flexible, and controllable underwater robot, a novel robot fish driven by piezoelectric bimorphs is proposed in this study, which has similar swimming patterns to the body and/or caudal fin propulsion (BCF) swimming mode and can achieve straight travel and steering underwater. The validity and feasibility of the principles were verified by wet mode simulation. A prototype is manufactured and tested for underwater vibration characteristics to confirm the motion pattern of the caudal fin of the robot fish. It has a weight of 13.3 g, a length of 150 mm. The maximum uniform speed of the robot fish prototype is 53 mm/s, and the thrust is 2.213 mN, and its maximum efficiency is 0.864%.
A self-sensing shape memory alloy actuator is harnessed as a computational resource by utilizing it as a physical reservoir computer. Physical reservoir computing is a machine learning technique that takes advantage of the dynamics of a physical system for computation. Compared to recurrent neural networks, this architecture can be both fast and efficient with a cheaper training procedure. A shape memory alloy actuator is designed, fabricated, and tested for processing information. Voltage variation along the shape memory alloy wire is used as the reservoir's nodes. The physical reservoir is then used to predict the future trajectory of the actuator's end effector under various driving signals. This self-prediction method is also reconfigurable, as demonstrated by training the reservoir for one waveform but testing it for a different one. A nonlinear autoregressive moving average prediction task was also used to highlight the physical reservoir computer's abilities. Following this methodology, the soft actuator can be used for actuation and computation at the same time without altering its design.
The design of soft actuators is often focused on achieving target trajectories or delivering specific forces and torques, rather than controlling the impedance of the actuator. This article outlines a new soft, tunable pneumatic impedance module based on an antagonistic actuator setup of textile-based pneumatic actuators intended to deliver bidirectional torques about a joint. Through mechanical programming of the actuators (select tuning of geometric parameters), the baseline torque to angle relationship of the module can be tuned. A high bandwidth fluidic controller that can rapidly modulate the pressure at up to 8 Hz in each antagonistic actuator was also developed to enable tunable impedance modulation. This high bandwidth was achieved through the characterization and modeling of the proportional valves used, derivation of a fluidic model, and derivation of control equations. The resulting impedance module was capable of modulating its stiffness from 0 to 100 Nm/rad, at velocities up to 120°/s and emulating asymmetric and nonlinear stiffness profiles, typical in wearable robotic applications.
Magnetic microrobots have tremendous potential applications due to their wireless actuation and fast response in confined spaces. Herein, inspired by fish, a magnetic microrobot working at liquid surfaces was proposed in order to transport microparts effectively. Different from other fish-like robots propelled by flexible caudal fins, the microrobot is designed as a simple sheet structure with a streamlined shape. It is fabricated monolithically utilizing polydimethylsiloxane doped with magnetic particles. The unequal thicknesses of different parts of the fish shape enable the microrobot to move faster via a liquid level difference around the body under an oscillating magnetic field. The propulsion mechanism is investigated through theoretical analysis and simulations. The motion performance characteristics are further characterized through experiments. It is interesting to find that the microrobot moves in a head-forward mode when the vertical magnetic field component is upward, whereas it moves in a tail-forward mode when the component is downward. Relying on the modulation of capillary forces, the microrobot is able to capture and deliver microballs along a given path. The maximum transporting speed can reach 1.2 mm s-1, which is about three times the microball diameter per second. It is also found that the transporting speed with the microball is much higher than that of the microrobot alone. The reason for this is that when the micropart and microrobot combine, the increased asymmetry of the liquid surfaces caused by the forward movement of the gravity center can increase the forward driving force. The proposed microrobot and the transporting method are expected to have more applications in micromanipulation fields.
Soft actuators have shown great potential in underwater applications due to diverse deformations, silent actuation mode, and waterproof features. To accomplish a versatile actuation approach with no environmental disturbances, this study demonstrates an electrically driven robotic piston that combines the advantages of soft robots with those of rigid mechanisms to provide adaptive and robust actuation. The robotic piston was actuated by multiple linearly stacked liquid pouch motors based on the liquid-vapor phase transition. The liquid pouch actuator is filled with low boiling fluid, which is capable of inflating several folds of its initial thickness by Joule heating to a temperature above the boiling point and contracting to the initial state by cooling. Based on the reversible liquid-vapor phase transition of the filled fluid, a series of linearly stacked pouch actuators can inflate and contract, which results in the reciprocating forward and backward movement of the piston rod in contact with them. The performance of liquid pouch actuators and soft robotic pistons was evaluated. The proposed soft robotic piston can be adapted as an electrical machine integrated with other different mechanisms, which was eventually demonstrated in robotic gripper systems and a legged walking robot in the underwater environment.
It has been a great challenge to develop robots that are able to perform complex movement patterns with high speed and, simultaneously, high accuracy. Copepods are animals found in freshwater and saltwater habitats that can have extremely fast escape responses when a predator is sensed by performing explosive curved jumps. Here, we present a design and build prototypes of a combustion-driven underwater soft robot, the "copebot", that, like copepods, is able to accurately reach nearby predefined locations in space within a single curved jump. Because of an improved thrust force transmission unit, causing a large initial acceleration peak (850 Bodylength*s-2), the copebot is 8 times faster than previous combustion-driven underwater soft robots, whilst able to perform a complete 360{\deg} rotation during the jump. Thrusts generated by the copebot are tested to quantitatively determine the actuation performance, and parametric studies are conducted to investigate the sensitivities of the input parameters to the kinematic performance of the copebot. We demonstrate the utility of our design by building a prototype that rapidly jumps out of the water, accurately lands on its feet on a small platform, wirelessly transmits data, and jumps back into the water. Our copebot design opens the way toward high-performance biomimetic robots for multifunctional applications.
Recent years in soft robotics development have witnessed rising innovations that draw inspiration from the natural world (i.e., biomimicry). By learning how various animals adapt to the environment, engineers can emulate them to tackle challenges in various fields such as automation and healthcare. In this study, an inflatable origami robot mimics the inflationary characteristics and motions of a pufferfish. The untethered robotic fish, PuffBot, can surge, yaw and heave motions in the water. The inflationary mechanism leveraged a chemical reaction between dilute acetic acid and sodium bicarbonate, producing carbon dioxide to inflate an in-built balloon beneath an origami exoskeleton. The inflation is controllable via incorporating a solenoid valve and is remotely operated using an app and Arduino board. For quantitative analysis, design verification tests were performed on its inflationary and motion capabilities, and the results highlighted PuffBot’s high level of mimicry to an actual pufferfish. These inflation and motion capabilities of PuffBot can serve as the foundation for specialized applications in various fields, such as water pool and underwater surveillance and obesity treatments.
Biomimetic aquatic robots are a promising solution for marine applications such as internal pipe inspection, beach safety, and animal observation because of their strong manoeuvrability and low environmental damage. As the application field of robots has changed from a structured known environment to an unstructured and unknown territory, the disadvantage of the low efficiency of the propeller propulsion has become more crucial. Among the various actuation methods of biomimetic robots, many researchers have utilised fluid actuation as fluid is clean, environmentally friendly, and easy to obtain. This paper presents a literature review of the locomotion mode, actuation method, and typical works on fluid-driven bionic aquatic robots. The actuator and structural material selection is then discussed, followed by research direction and application prospects of fluid-driven bionic aquatic robots.
Existing miniature underwater robots, which use electromagnetic actuators or soft actuators, function in shallow waters. However, in the deep sea, the robots face challenges, such as the miniaturization of the pressure protection unit and the driving method for rapid and agile motions. Herein, a jet‐driven method for a high‐pressure underwater environment is proposed by utilizing the high‐frequency vibration of a piezoelectric vibrator. Thereafter, an antihydropressure miniature robot with a body length of less than 5 cm is designed, which can perform the highly agile actions of floating, sinking, hovering, straight driving, and turning under a water pressure of 20 MPa (equal to the pressure under a water depth of 2000 m). A vertical velocity of 2.95 BH/s and a horizontal velocity of 3.22 BL/s are realized by the prototype, and it achieves faster motions than existing miniature underwater robots. Some potential applications have been realized, including small multicorner pipe exploration by carrying a camera, seaweed epidermal cell sampling in designated areas, and large object transportation by swarming, which proves the high maneuverability and agility of the developed robot. These merits make the robot ideal for multitasking operations in narrow environments with high water pressure, such as multiobstacle seabed. A 5 cm‐scale agile underwater robot based on the piezoelectric jetting method was proposed. This robot achieves a multi‐locomotion mode under a maximum pressure of 20 MPa, and its maximum speed reaches 3.22 BL/s. The successful exploration of multi‐corner pipes and large object transport by the cooperation of two robots demonstrates the extraordinary ability to work in deep‐sea narrow areas.
A fish-inspired underwater vehicle (FIUV) has advantages in many real-world applications. This study presents the design of a FIUV with a wire-driven flexible spine and a servo motor-driven rigid caudal fin to optimize the swimming performance of a FIUV. Kinematics and dynamics are conducted to optimize its swimming performance, and a swimming performance indicator (SPI) is proposed. Moreover, the relationship among the velocity, lateral force of the FIUV, and its SPI is established. This study examines the SPI based on different combinations of the cycle and the amplitude of the swing and finds the condition in which the swimming performance is optimized. Finally, the rationality of its structural design, the validity of kinematics, and the accuracy of the SPI are verified through simulations and experiments.
To satisfy the maneuverability requirements in a complicated environment, fish have evolved with special segmented muscle to produce undulatory locomotion. Herein, we developed a three-dimensional W-shaped model of musculo-tendinous system to mimic realistic segmented muscle of fish, and directly quantify the relationship between local muscle contraction and the corresponding flexion. By regulating the key parameters of model, the variation in local muscle strain producing prescribed set of kinematics is calculated. Furthermore, the morphological variations of the musculo-tendinous system located in fish caudal region and the distinctions between different swimmers are also discussed. It is found out that for a desired bending curvature, strain of the musculo-tendinous system can be reduced by lengthening the model longitudinally. Thus, if the muscle contraction is fixed, larger amplitude and flexion can be achieved by elongating the W-shaped model. This also explains the morphological diversities of segmented muscle within anguilliform, carangiform, and thunniform. Fish with better swimming ability are likely equipped with relatively longer myomere and shaper pointing cones. Therefore, the musculo-tendinous system amplifies the body curvature, it has functional benefits on fish kinematics. In additionally, this paper may provide some inspirations on the structural design of fish-inspired soft robots.
Untethered synthetic microrobots have significant potential to revolutionize biomedical interventions therapy in the future. However, the relatively slow speed of microrobots and viscosity biofluid environments are some of barriers standing in the way of microrobots’ biomedical applications. Herein, inspired by high‐speed biological escape propulsion, NIR‐driven microrobots with a high‐speed, unidirectional propulsion in the high‐viscosity liquid are proposed. The bubble's growth and ejection cause the proposed 3D‐printed microrobot to propel forward. The 3D‐printed claw‐like microrobot achieves motion average speed of 1.4 mm s−1 (three‐body length (bl) s−1) when driven by NIR light in a pure glycerol viscous (945 mPa s, 25 °C) environment, which has a viscosity that is more than 200 times the viscosity of blood and of 54 mm s−1 (120 bl s−1) when driven by NIR light in deionized (DI) water. This work provides more ideas for the design and propulsion of light‐driven microrobots in a high‐viscosity vivo environment, which may broaden the applications of microrobots in the biomedical field, such as propulsion and navigation in confined and hard‐to‐reach body location areas. A claw‐like asymmetric hydrogel microrobot undergoes ejection self‐propulsion upon NIR light irradiation at high speed. The “bomb‐like” behavior generates bubble streams under NIR light and drives the ejection propulsion of the microrobots. The microrobots also display efficient translational controllable propulsion in a high‐viscosity environment.
Jellyfish are one of the underwater creatures that have been imitated by underwater bionic robots, but a current challenge to create a bionic jellyfish is with the use of piezoelectric ceramic sheets as the driving element, due to their small output displacement. Here, a bionic robotic jellyfish with three tentacles is presented that is driven by three piezoelectric beams, and to transmit power, a large deformation composite flexure hinge is created which employs fishing line embedded in a 3D printed structure. In addition, the structure design and fabrication of the drive system are described. A dynamic model of the drive system is established to solve for the working mode, forced displacement responses, and swimming lift. A series of experiments are carried out to verify the theoretical analysis and validate the design of the robotic jellyfish. The proposed robotic jellyfish has a total mass of 29.4 g, tentacle spread of about 150 mm, and an overall height of 100 mm. The robotic jellyfish can exhibit swimming performance with drive frequencies of 0.7-1.1 Hz, and the best achieved swimming speed was 10 mm/s. These design, modeling, and fabrication methods may be beneficial and inspiring for the future development of the micro soft robot.
With the increase of the underwater operation requirements and the development of the soft robot technology, the underwater soft robot becomes one of the top choices in the underwater robots. The underwater soft robots with artificial muscles to realize the drive control and the bionic motion become a research hot spot. This paper introduces underwater soft robots in seven kinds of the existing drive modes, based on the artificial muscles. The underwater soft robots can have five bionic movement forms. At the end, the future applications of underwater robots in the underwater exploration are discussed.
The development of a wireless undulatory tadpole robot using ionic polymer–metal composite (IPMC) actuators is presented. In order to improve the thrust of the tadpole robot, a biomimetic undulatory motion of the fin tail is implemented. The overall size of the underwater microrobot prototype, shaped as a tadpole, is 96 mm in length, 24 mm in width, and 25 mm in thickness. It has one polymer fin tail driven by the cast IPMC actuator, an internal (wireless) power source, and an embedded controller. The motion of the tadpole microrobot is controlled by changing the frequency and duty ratio of the input voltage. Experimental results show that this technique can accurately control the steering and swimming speed of the proposed underwater tadpole robot.
This article describes research into the fluid mechanics of fish propulsion, with the ultimate aim of applying the results to ship and submarine propulsion. Simple foils that approximated the swish of a fish tail were constructed in the laboratory. Experiments revealed that the jet vortices in the wake of the flow play a central role in the generation of thrust. By analysing data from the flapping foils, it was found that thrust-induced vortices from optimally when the Strouhal number lay between 0.25 and 0.35. It was found that many fish swing their tails within this optimal range also. From these results, an artificial fish, known as RoboTuna, was constructed. -S.E.Brown
Summary The mechanics and kinematics of accelerational undulatory locomotion by the chaetognath Sagitta elegans (Verrill, 1873) are studied with a combination of high- speed cinematography (200framess~') and mathematical modeling. The model is constructed such that it predicts body velocity for an organism starting from rest and accelerating rapidly by swimming with prescribed wave kinematics. The speed of the undulatory propulsive waves and the number of these waves on the body is highly conserved across 11 individuals, while the wave amplitude is positively related to distance traveled in the first 65 ms of swimming. There is excellent agreement between these data and predictions of body translations that are based on a mathematical model for this mode of locomotion. The model also shows that instantaneous forces generated by the undulating body are much larger than average forces and consist of non-trivial inertial terms, even for such small organisms. The model also shows that the distance traveled over a fixed time interval is limited by the maximum muscle stress that can be physiologically generated. Peak instantaneous force represents a mechanical upper boundary to thrust production and, hence, a limit to performance.
This paper presents the design and the experimental result of the active position control of a shape memory alloy (SMA) wire actuated composite beam. The composite beam has a honeycomb structure with SMA wires embedded in one of its face sheets for the active actuation. The potential applications of this experiment include thermo-distortion compensation for precision space structure, stern shape control for submarines, and flap shape control for aeronautical applications. SMA wires are chosen as the actuating elements due to their high recovery stress ({>}500 MPa) and tolerance to high strain (up to 6%). However, SMA wires are inherently nonlinear and pose a challenge for control design. A robust controller is designed and implemented to actively control the tip position of the composite beam. The experiment set-up consists of the composite beam with embedded SMA wires, a programmable current/voltage amplifier to actuate the SMA wires, an infrared laser range sensor to detect the beam tip displacement, and a real-time data acquisition and control system. The experimental result demonstrates the effectiveness of the robust control.
This paper describes an electroactive polymer robot with ray-like pectoral fins. Electroactive polymers are materials that change their geometry in response to electric field and can be used to replace electromechanical devices. The aim of this study is to show that these materials can be used to build more complicated devices and the behaviour of these devices can be coordinated to some extent. Both of the pectoral fins are built of eight electroactive polymer muscles. The experiments show that the fins are able to generate undulating motion and propel the body forward. The speed of the device is considerably slower than that of ray-like fishes but the device also has a smaller muscle mass and total mass ratio compared to aquatic animals.
The development of a wireless undulatory tadpole robot using ionic polymer–metal composite (IPMC) actuators is presented. In order to improve the thrust of the tadpole robot, a biomimetic undulatory motion of the fin tail is implemented. The overall size of the underwater microrobot prototype, shaped as a tadpole, is 96 mm in length, 24 mm in width, and 25 mm in thickness. It has one polymer fin tail driven by the cast IPMC actuator, an internal (wireless) power source, and an embedded controller. The motion of the tadpole microrobot is controlled by changing the frequency and duty ratio of the input voltage. Experimental results show that this technique can accurately control the steering and swimming speed of the proposed underwater tadpole robot.
Recent advances in integrative studies of Locomotion have revealed several general principles. Energy storage and exchange mechanisms discovered in walking and running bipeds apply to multilegged Locomotion and even to flying and swimming. Nonpropulsive lateral forces can be sizable, but they may benefit stability, maneuverability, or other criteria that become apparent in natural environments. Locomotor control systems combine rapid mechanical preflexes with multimodal sensory feedback and feedforward commands. Muscles have a surprising variety of functions in locomotion, serving as motors, brakes, springs, and struts. Integrative approaches reveal not only how each component within a Locomotor system operates but how they function as a collective whole.
Recent advances in integrative studies of locomotion have revealed several general principles. Energy storage and exchange mechanisms discovered in walking and running bipeds apply to multilegged locomotion and even to flying and swimming. Nonpropulsive lateral forces can be sizable, but they may benefit stability, maneuverability, or other criteria that become apparent in natural environments. Locomotor control systems combine rapid mechanical preflexes with multimodal sensory feedback and feedforward commands. Muscles have a surprising variety of functions in locomotion, serving as motors, brakes, springs, and struts. Integrative approaches reveal not only how each component within a locomotor system operates but how they function as a collective whole.
Although squid are among the most versatile swimmers and rely on a unique locomotor system, little is known about the swimming mechanics and behavior of most squid, especially those that swim at low speeds in inshore waters. Shallow-water brief squid Lolliguncula brevis, ranging in size from 1.8 to 8.9 cm in dorsal mantle length (DML), were placed in flumes and videotaped, and the data were analyzed using motion-analysis equipment. Flow visualization and force measurement experiments were also performed in water tunnels. Mean critical swimming speeds (U(crit)) ranged from 15.3 to 22.8 cm s(-1), and mean transition speeds (U(t); the speed above which squid swim exclusively in a tail-first orientation) varied from 9.0 to 15.3 cm s(-1). At low speeds, negatively buoyant brief squid generated lift and/or improved stability by positioning the mantle and arms at high angles of attack, directing high-speed jets downwards (angles >50 degrees ) and using fin activity. To reduce drag at high speeds, the squid decreased angles of attack and swam tail-first. Fin motion, which could not be characterized exclusively as drag- or lift-based propulsion, was used over 50-95 % of the sustained speed range and provided as much as 83.8 % of the vertical and 55.1 % of the horizontal thrust. Small squid (<3.0 cm DML) used different swimming strategies from those of larger squid, possibly to maximize thrust benefits from vortex ring formation. Furthermore, brief squid employed various unsteady behaviors, such as manipulating funnel diameter during jetting, altering arm position and swimming in different orientations, to boost swimming performance. These results demonstrate that locomotion in slow-swimming squid is complex, involving intricate spatial and temporal interactions between the mantle, fins, arms and funnel.
This paper presents the design and experiment results of active position
control of a shape memory alloy (SMA) wires actuated composite beam. The
composite beam is honeycomb structured with shape memory alloy wires
embedded in one of its phase sheet for active actuation. The potential
applications of this experiment include thermo-distortion compensation
for precession space structure, stern shape control for submarines, and
flap shape control for aeronautical applications. Shape memory alloy
wires are chosen as actuating elements due to their high recovery stress
(maybe greater than 700 MPa) and tolerance to high strain (up to 8%).
However, shape memory alloy wires are inherently nonlinear and pose a
challenge for control design. A robust controller is designed and
implemented to active control the tip position of the composite beam.
The experiment setup consists of the composite beam with embedded SMA
wires, programmable current/voltage amplifier to actuate the SMA wires,
an infrared laser range sensor to detect the beam tip displacement, and
a real-time data acquisition and control system. Experiments
demonstrated the effectiveness of the robust control.
The bodies of coleoid cephalopods are characterized by a dense musculature consisting of tightly packed bundles of muscle fibers arranged in three mutually perpendicular planes. This arrangement of muscle, termed a 'muscular hydrostat', generates force and also provides skeletal support. Muscle function during movement and locomotion thus does not depend on rigid skeletal elements, even though many extant coleoids possess hard parts. In this review, we describe the arrangement and microanatomy of the musculature and connective tissues from a variety of coleoids and from a range of cephalopod organs and systems including the mantle, funnel, fins, arms, tentacles, and suckers. We analyze the muscle and connective tissues from the standpoint of biomechanics in order to describe their function in movement and locomotion. This analysis demonstrates that the same basic principles of support and movement are shared by all of these structures. In addition, the crucial role
The lateral fins of cuttlefish and squid consist of a tightly packed three-dimensional array of musculature that lacks bony skeletal support or fluid-filled cavities for hydrostatic skeletal support. During swimming and manoeuvring, the fins are bent upward and downward in undulatory waves. The fin musculature is arranged in three mutually perpendicular planes. Transverse muscle bundles extend parallel to the fin surface from the base of the fin to the fin margin. Dorso-ventral muscle bundles extend from dorsal and ventral connective tissue fasciae to a median connective tissue fascia. A layer of longitudinal muscle bundles is situated adjacent to both the dorsal and ventral surface of the median fascia. The muscle fibres are obliquely striated and include a core of mitochondria. A zone of muscle fibres with a more extensive core of mitochondria is present in both the dorsal and the ventral transverse muscle bundles. It is hypothesized that these muscle masses include two fibre types with different aerobic capacity. A network of connective tissue fibres is present in the transverse and dorso-ventral muscle masses. These fibres, probably collagen, are oriented at 45 to the long axes of the transverse and dorsoventral muscle fibres in transverse planes.
A biomechanicayl analysis of the morphology suggests that support for fin movements is provided by simultaneous contractile activity of muscles of specific orientations in a manner similar to that proposed for other ‘muscular-hydrostats’. The musculature therefore provides both the force and support for movement. Connective tissue fibres may aid in providing support and may also serve for elastic energy storage.
Shape memory alloy (SMA) has great potential for microminiature
actuators. The feasibility is discussed, and theoretical estimates based
on scale effect are presented. Control schemes for microminiature SMA
servoactuators are discussed, and a control scheme is proposed. Combined
with electric resistance feedback and position feedback, it enables the
author to control stiffness of SMA directly and to sense force without a
force sensor. Experimental verifications are reported. The application
of a miniature SMA actuator to a miniature clean gripper with
position-force hybrid control for microelectronics manufacture is
presented. Fabrication of a thin film micro SMA actuator is investigated
We have developed a biologically based underwater, autonomous vehicle modeled after a simple vertebrate, the sea lamprey. The robot consists of a cylindrical Plexiglas electronics bay with a polyurethane undulator actuated by shape memory alloy artificial muscles. Sensors include a compass, pitch and roll inclinometers and sonar rangers, the signals of which are quantized into a labeled line code. Behavioral parameters are reverse engineered from the behavior of the target organisms.
High-speed, high-resolution digital video recordings of swimming squid (Loligo pealei) were acquired. These recordings were used to determine very accurate swimming kinematics, body deformations and mantle cavity volume. The time-varying squid profile was digitized automatically from the acquired swimming sequences. Mantle cavity volume flow rates were determined under the assumption of axisymmetry and the condition of incompressibility. The data were then used to calculate jet velocity, jet thrust and intramantle pressure, including unsteady effects. Because of the accurate measurements of volume flow rate, the standard use of estimated discharge coefficients was avoided. Equations for jet and whole-cycle propulsive efficiency were developed, including a general equation incorporating unsteady effects. Squid were observed to eject up to 94 % of their intramantle working fluid at relatively high swimming speeds. As a result, the standard use of the so-called large-reservoir approximation in the determination of intramantle pressure by the Bernoulli equation leads to significant errors in calculating intramantle pressure from jet velocity and vice versa. The failure of this approximation in squid locomotion also implies that pressure variation throughout the mantle cannot be ignored. In addition, the unsteady terms of the Bernoulli equation and the momentum equation proved to be significant to the determination of intramantle pressure and jet thrust. Equations of propulsive efficiency derived for squid did not resemble Froude efficiency. Instead, they resembled the equation of rocket motor propulsive efficiency. The Froude equation was found to underestimate the propulsive efficiency of the jet period of the squid locomotory cycle and to overestimate whole-cycle propulsive efficiency when compared with efficiencies calculated from equations derived with the squid locomotory apparatus in mind. The equations for squid propulsive efficiency reveal that the refill period of squid plays a greater role, and the jet period a lesser role, in the low whole-cycle efficiencies predicted in squid and similar jet-propelled organisms. These findings offer new perspectives on locomotory hydrodynamics, intramantle pressure measurements and functional morphology with regard to squid and other jet-propelled organisms.
This paper deals with a micro mobile robot in water utilizing a
PZT(Pb(Zr,Ti)O3) as an actuator. A robot driven by a PZT
requires a magnification mechanism and the effect of the resonance
condition to enlarge the displacement of the PZT to some extent. We show
a structure for the magnification mechanism, which is made by the wire
cut method. The magnification ratio is 326 geometrically. We propose a
prototype micro mobile robot in water which possesses a pair of fins and
moves them symmetrically. Therefore, the momentum of this robot is
canceled and the tendency to move straight ahead is improved. The
mechanism and the principle of the robot that is devised considers the
problems in former research. We prove the effectiveness of the mechanism
and the propulsion principle by using a pair of fins both theoretically
and experimentally through computer simulations and swimming experiments
in fluid. The size of the robot is 50 mm in length and 6 mm in width.
This robot has many possible applications, such as small pipeline
inspections and use in bio medical fields
This paper deals with a micro mobile robot in water utilizing a
PZT(Pb(Zr,Ti)O3) as an actuator. A robot driven by a PZT
requires a magnification mechanism and the effects of the resonance to
enlarge the displacement of the PZT. In this paper, the authors propose
a prototype micro mobile robot which has a new steering mechanism. The
robot possesses a pair of legs and each leg has a pair of fins with some
angle, which is essential to the improvement of the robot performance. A
leg generates force both forward and backward according to frequency
because the offset angle between a pair of fins works properly.
Therefore, the robot can steer efficiently by combination of both modes.
The size of the robot is 32 mm in length and 19 mm in width. This robot
has many possible applications, such as small pipelines inspection and
use in biomedical fields
Recently, many micro robots have been proposed for various purposes due to the advances of the precise process technology, and further progress in this field is expected. In this paper, a prototype micro mobile robot in water which has a new steering mechanism with a pair of actuators is proposed. It is proved that the mechanism can generate force both forward and backward by each actuator theoretically and experimentally and that a combination of two modes improves the performance of the robot on the swimming experiment.
This paper presents a new prototype model of an underwater fish-like microrobot utilizing ionic conducting polymer film (ICPF) actuator as the servo actuator to realize swimming motion with three degrees of freedom. A biomimetic fish-like microrobot using ICPF actuator as a propulsion tail fin and a buoyancy adjuster for the swimming structure in water or aqueous medium is developed. The overall size of the underwater prototype fish shaped microrobot is 45 mm in length, 10 mm in width, and 4 mm in thickness. It has two tails with a fin driven respectively, a body posture adjuster, and a buoyancy adjuster. The moving characteristic of the underwater microrobot is measured by changing the frequency of input voltage from 0.1-5 Hz in water and the amplitude of input voltage from 0.5-10 V. The experimental results indicate that changing the amplitude and frequency of input voltage can control the swimming speed of proposed underwater microrobot.
This study investigates the potential for incorporating the elastic mechanisms found in fish propulsive systems into mechanical systems for the development of underwater propulsion. Physical and kinematic information associated with the steady swimming of the bonito and other scombrid species was used for the design. Several electroactive materials were examined for simulating muscle behavior and their relative suitability was compared. A dynamic analysis method adapted for muscle, which is a work-loop technique, would provide valuable information. However, the lack of such information on engineering materials made any direct comparison between the biological and mechanical systems difficult. Based on available information, nickel-titanium shape memory alloy (SMA) was better suited to produce relatively slow and powerful steady swimming of scombrid species. The simplified geometry of muscular systems and axial tendons was adapted. These arrangements alleviate the limited strain of the SMA by trading force for distance and provide an effective force transmission pathways to the backbone.
Turning Modes for a Fish Robot
- K Hirata
K. Hirata, Turning Modes for a Fish Robot, 2001, http://www.nmri.go.jp/
eng/khirata/fish/general/turn/index e.html.