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Multi-axis force sensors: A state-of-the-art review
Abstract
A multi-axis force sensor measures forces and moments occurring in more than one spatial direction. In this way, a single multi-axis sensor can perform what is essentially a three-dimensional measurement of physical quantities. This feature makes multi-axis sensors popular in a wide range of engineering research including automation, machining processes, aerospace, medical applications and civil engineering. Measurement of multi-directional forces and moments is typically achieved using multiple strain-sensitive elements mounted on an elastic structure. Both the sensitive elements and the elastic structure require careful consideration to design a force sensor for accuracy, reliability and robustness. While the development of multi-axis sensors has been considered extensively in the literature over the past seven decades, a collective resource which collates and examines this information does not exist. This review explores multi-axis force sensor developments across a broad range of disciplines. The salient fundamental strain sensing techniques adopted for the strain-sensitive elements reported in the literature are discussed and a critical review of elastic structure designs that have featured in the literature is also presented.
... Multi-component force and moment transducers are widely used in both industrial and research settings including within the fields of robotics, healthcare, automotive, aerospace, and energy [1][2][3][4][5]. These sensors typically utilize elastic deformation to measure force and moment components precisely [1,2]. ...
... Multi-component force and moment transducers are widely used in both industrial and research settings including within the fields of robotics, healthcare, automotive, aerospace, and energy [1][2][3][4][5]. These sensors typically utilize elastic deformation to measure force and moment components precisely [1,2]. Multicomponent force transducers are commercially produced and off the shelf options generally satisfy customer requirements. ...
... Since study 1 has two gauges on the same XY coordinate (as shown in figure 4(a)), the single gauge readings on the 2D half-bridge for gauges 1 and 2 are duplicated for gauges 3 and 4 to simulate a full bridge output. Study 2 has four independent locations for each gauge and the outputs are directly represented in table 7. The last column in table 7 (full bridge strain reading) uses the output of gauges 1 to 4 using the summation expression in equation (2). In review of this last column from each study, both designs show satisfactory strain response under the axial load. ...
This paper proposes an innovative design framework for a multi-component force transducer subject to reversible load direction using topology optimization. Multi-component force transducers are used widely in industries ranging from robotics to healthcare. In this work, the proposed design framework is applied to a specific force transducer, a wind tunnel balance used within aeronautic ground testing. The axial component is one of the six components of the wind tunnel balance, and this component is difficult to design because the axial force is typically much smaller than other force components. This paper uses topology optimization to obtain a non-intuitive axial component design. To realize the design requirements, a new design formulation is suggested to amplify the gauge reading under a small axial loading and to suppress the gauge reading under nonaxial loadings. Prototypes are manufactured and their performances are experimentally verified. The proposed framework can be applied to any type of force transducer that needs to amplify a response from a certain force and to suppress the other responses.
... The crosstalks caused by torques Mx and My in the detection of force Fz are caused by the higherorder nonlinear terms of u 4 with Mx and My, which are ignored in Eq. (2). The complete analytical formulas are expressed by Taylor expansion, as shown in Eq. (4). ...
... By analyzing the theoretical model of the crosstalk terms, the crosstalk caused by the eccentricity D in Eq. (2) and that caused by nonlinearity in Eq. (6) can be compensated for by the decoupling operation, as shown in Eq. (7). Figure 2k shows the changes in the new decoupling outputs U 1 -U 6 under six-axis force/torque, which have better decoupling ability in theory than u 1 -u 6 . ...
... The firstorder linear displacement/angle sensitivity s ii (i = 1-6) in Eqs. (2) and (7) can be obtained using the Taylor expansions in Eq. (4), as in Eq. (8). ...
Miniaturized six-axis force/torque sensors have potential applications in robotic tactile sensing, minimally invasive surgery, and other narrow operating spaces, where currently available commercial sensors cannot meet the requirements because of their large size. In this study, a silicon-based capacitive six-axis force/torque sensing chip with a small size of 9.3 × 9.3 × 0.98 mm was designed, fabricated, and tested. A sandwich decoupling structure with a symmetrical layered arrangement of S-shaped beams, comb capacitors, and parallel capacitors was employed. A decoupling theory considering eccentricity and nonlinear effects was derived to realize low axial crosstalk. The proposed S-shaped beams achieved a large measurement range through stress optimization. The results of a coupled multiphysics field finite-element simulation agreed well with those of theoretical analyses. The test results show that the proposed sensing chip can detect six-axis force/torque separately, with all crosstalk errors less than 2.59%FS. Its force and torque measurement ranges can reach as much as 2.5 N and 12.5 N·mm, respectively. The sensing chip also has high sensitivities of 0.52 pF/N and 0.27 pF/(N·mm) for force and torque detection, respectively.
... These sensors find applications across diverse fields, including robotics [1,2,3], biomedical applications [4,5,6], medical devices [7,8], manufacturing [9], automotive [10,11], aerospace [12], and beyond [13]. Given that force is an intensity property that cannot be directly measured [14], force sensors typically acquire external force information by assessing the deformation or displacement of the elastic-sensitive elements within them. Consequently, elastic-sensitive elements play a pivotal role in multi-axis force sensors, with their design significantly influencing key characteristics such as cross-axis coupling, measuring range and sensitivity [15]. ...
... Recently, there has been a growing focus on hardware decoupling [36,37,38,39,40,41,42]. Some researchers have chosen compliant mechanisms to replace the traditional elastic-sensitive elements, resulting in reduced cross-axis coupling errors and improved sensitivity [14,43]. ...
... In the equations, represents the force along the X-axis acting on node ji of si, represents the moment around the X-axis at node ji of si, represents the translational displacement along the X-axis at node ji of si, and represents the angular displacement around the x-axis at node ji of si and so on. The nodal force fi and nodal displacement di satisfy (14). (14) where Kbeam-i is the stiffness matrix for the unit si, and its matrix elements are given by Li in 2022 [67]. ...
Multi-axis force sensors are integral to a wide range of high-tech applications, including robotics and machine monitoring. However, a significant challenge in their use is the high cross-axis coupling, which detrimentally affects measurement accuracy. To address this critical issue, this paper presents a comprehensive design method for multi-axis force sensors. This approach utilizes compliant parallel mechanisms, effectively decoupling the measured forces on multiple axes and enabling precise and independent measurement of each component force within the multi-axis system. Focusing on three-axis force sensors as a case study, this paper elucidates the proposed design principle. The comprehensive study covers system configuration, mechanical design, analytical modeling, numerical simulation, prototype development, and experimental evaluation. The resultant three-axis force sensor, prior to calibration, exhibits an average coupling error of just about 1.5%, underscoring its superior decoupling capability. The design concept and methodologies outlined here offer valuable insights for the development of self-decoupling multi-axis force sensors, advancing the field significantly.
... The majority of commercially available 6-axis F/T sensors are comprised of miniature strain gauges applied to precise micro-machined metal flexures [1][2][3]. This method generates very accurate sensors, but comes at a very high cost of fabrication and specialized circuitry for amplification and signal conditioning. ...
... The process consists of moving the robot end effector along each axis and collecting magnetic field readings at a total of thirty discrete points. To determine the mapping in the Z-axis, the robot moved the magnet away in 0.2mm increments withing the range [1,3]mm of distance between the magnet and the chip. Similarly, in the X and Y dimensions, the data is collected in the range [−1, 1]mm with 0.2mm increments in their respective axes. ...
Haptic devices have shown to be valuable in supplementing surgical training, especially when providing haptic feedback based on user performance metrics such as wrench applied by the user on the tool. However, current 6-axis force/torque sensors are prohibitively expensive. This paper presents the design and calibration of a low-cost, six-axis force/torque sensor specially designed for laparoscopic haptic training applications. The proposed design uses Hall-effect sensors to measure the change in the position of magnets embedded in a silicone layer that results from an applied wrench to the device. Preliminary experimental validation demonstrates that these sensors can achieve an accuracy of 0.45 N and 0.014 Nm, and a theoretical XY range of +/-50N, Z range of +/-20N, and torque range of +/-0.2Nm. This study indicates that the proposed low-cost 6-axis force/torque sensor can accurately measure user force and provide useful feedback during laparoscopic training on a haptic device.
... Both factors play an e role in the performance of 3D force sensors. The cross-structure configuration, w ing elements distributed on their four structural beams, is widely implemented i ent industrial 3D force sensors [44]. In this study, a flexible 3D force sensor was p utilizing the cross-structure configuration's sensor placements and fixable host ma terial, as shown in Figure 1. ...
... Both factors play an essential role in the performance of 3D force sensors. The cross-structure configuration, with sensing elements distributed on their four structural beams, is widely implemented in different industrial 3D force sensors [44]. In this study, a flexible 3D force sensor was proposed utilizing the cross-structure configuration's sensor placements and fixable host matrix material, as shown in Figure 1. ...
The three-dimensional (3D) force sensor has become essential in industrial and medical applications. The existing conventional 3D force sensors quantify the three-direction force components at a point of interest or extended contact area. However, they are typically made of rigid, complex structures and expensive materials, making them hard to implement in different soft or fixable industrial and medical applications. In this work, a new flexible 3D force sensor based on polymer nanocomposite (PNC) sensing elements was proposed and tested for its sensitivity to forces in the 3D space. Multi-walled carbon nanotube/polyvinylidene fluoride (MWCNT/PVDF) sensing element films were fabricated using the spray coating technique. The MWCNTs play an essential role in strain sensitivity in the sensing elements. They have been utilized for internal strain measurements of the fixable 3D force sensor’s structure in response to 3D forces. The MWCNT/PVDF was selected for its high sensitivity and capability to measure high and low-frequency forces. Four sensing elements were distributed into a cross-beam structure configuration, the most typically used solid 3D force sensor. Then, the sensing elements were inserted between two silicone rubber layers to enhance the sensor’s flexibility. The developed sensor was tested under different static and dynamic loading scenarios and exhibited excellent sensitivity and ability to distinguish between tension and compression force directions. The proposed sensor can be implemented in vast applications, including soft robotics and prostheses’ internal forces of patients with limb amputations.
... Further advancements in sensor technology are needed to simplify integration and improve monitoring accuracy. For instance, multi-axis force sensors show potential by measuring multiple axial forces and moments within a single setup, reducing the need for complex sensor arrays and enhancing system integration [207]. Vibration sensors also offer an alternative approach to tool wear detection without requiring force sensors to be embedded directly into the dies [151]. ...
... To achieve interaction force or tactile sensing technique, various methods have been developed based on the principles of magnetics 19 , resistance [20][21][22] , capacitance [23][24][25][26] , piezoelectricity [27][28][29] , vision [30][31][32] , and optics [33][34][35] , etc. Among them, force sensors based on the fiber Bragg grating (FBG) sensors exhibit high adaptability to robotic assisted surgery because of their advantages of small size, high sensitivity, and good stability 36 . On the millimeter-scale instruments for ophthalmic microsurgery, the FBG force sensors with sub-millinewton resolution were integrated 37,38 , which can surpass the force-sensing sensitivity and accuracy of the human hand. ...
Delicate manual microsurgeries rely on sufficient hands-on experience for safe manipulations. Automated surgical devices can enhance the effectiveness, but developing high-resolution, multi-axis force-sensing devices for micro operations remains challenging. In this study, a 6-axis force-sensing pneumatic forceps with a serial-parallel robotic platform for cochlear implantation is developed. The forceps features a curved body shape embedded with parallel and inclined fiber Bragg grating sensors for 6-axis force sensing, and a pneumatic gripper with decoupled actuation is located at its end for actively grasping and releasing the electrode array. The robotic platform comprises a customized spherical parallel mechanism and a robotic arm, which can provide independent 3-DOF rotations and 3-DOF translations. The feasibility of the developed robotic forceps is validated through cadaveric studies on a temporal bone and a human cadaveric head. In summary, the robotic forceps provides a decoupled mechanism for pneumatic actuation and force sensing, further demonstrating its potential for force interaction and stable operation during robotic microsurgery.
... Force is an important parameter that has a direct effect on our daily life. Force application is relevant in various fields, including home appliances, consumer electronics, healthcare and fitness devices, machining, and construction [1][2][3]. Force measurement is a fundamental aspect in numerous scientific and engineering disciplines, including mechanics, robotics, biomedical engineering and industrial automation [1,4]. Accurate and reliable force-measuring sensors play a pivotal role in preventing overload and system damage. ...
This study proposes a non-contact force-measuring sensor design that utilizes a polymer optical fiber. The sensor design uses two separate fibers (i.e. sensor input and sensor output fibers). The sensor input fiber is helically wound around a supportive circular pipe, with aim of creating bend losses at every bend loop. The sensor output fiber gains advantages by coupling the variable optical power from different bend loops of the sensor input fiber. The variable amount of optical power coupling is directly associated with the applied force on the spring, which serves as an intermediary in transferring force to the sensor. Further, for variable ranges of forces, three different springs are used, which sustain variable force ranges (0–20, 0–40 and 0–60 N), respectively. The proposed sensor design addresses the critical need for force sensors capable of effectively measuring force across a wide dynamic range. The results of this study support the sensor design, which has a wide range of force-measuring capabilities, from low to high, with a close and repeatable response. The low-range force measurement (0–20 N) indicates the sensor’s high sensitivity of 0.567 µW N⁻¹. Further, the sensor is also capable of a large force measuring range (0–60 N) with sensitivity of 0.189 µW N⁻¹.
... Achieving the required measurement accuracy-at least 25 g for regolith sampling devices (RSDs)-is difficult under these conditions. Furthermore, the accuracy of force sensors is influenced by factors like nonlinearity, hysteresis, and inter-channel coupling [29]. These factors typically introduce uncertainty levels starting at 0.01% of the full measurement range and can reach as high as 3%, depending on the application and design. ...
This paper presents the concept of a radiofrequency (RF) sensor designed to estimate the mass of the regolith acquired by a sampling device or excavator in planetary environments. The sensor utilizes a microstrip line with an open end as the sensing element, with the mass estimation based on measurements of the phase of the reflection coefficient (S11 of the scattering matrix) for the line immersed in the regolith. The Rotary Clamshell Excavator (RCE) was employed for the experimental evaluation of the sensor’s performance. The RCE successfully passed an environmental test campaign, demonstrating its suitability for future lunar missions. The test results indicate that the RF sensor can estimate the mass of the acquired regolith with reasonable accuracy, approximately 15%, making it a viable solution for rough mass estimation in sampling devices and excavators.
... The need to measure efforts in six axes induced the development of transducers [1] specifically applied to several areas of engineering, such as wind tunnels [2 -4], structures [5,6], robotics [7 -9], biomechanics [10,11], haptic interaction [12], driver-vehicle interaction [13][14], wheel [15][16][17] and others. Six-axle wheel force load cells (WLC) are used for dimensioning and experimentally verifying cars' suspension design. ...
The accurate measurement of forces and torques acting on a vehicle’s chassis, originating from wheel-pavement interactions, is essential for optimizing suspension systems, axles, and other structural components. A critical challenge in optimizing wheel load cell (WLC) design is to enhance sensitivity without compromising mechanical robustness. To address this question, this study developed a six-axis load cell designed to decouple force and torque measurements, achieving high sensitivity and reliability. The objective was to design an optimized WLC for multi-axis force measurement by maximizing sensitivity through a metamodel-based hybrid optimization framework. The methodology began with a fractional factorial Design of Experiments (DOE) to identify key parameters affecting load cell sensitivity and to define the optimization search space. This was followed by a dual-step parametric optimization process, utilizing the finite element method (FEM) to evaluate load cell performance and an inner-point optimization algorithm for convergence. After completing the DOE and FEM stages, the load cell was physically constructed and calibrated using a universal testing machine MTS 810, where experimental data closely matched simulation results, validating the design’s effectiveness. The main findings indicate that the optimized load cell can reliably measure six components, with a sensitivity increase of 14% compared to conventional designs. Numerical results from FEM analyses showed stress levels at 215 MPa, displacements around 0.16 mm, and a first-mode vibration frequency of 1351 Hz, meeting all structural integrity and performance requirements. Calibration confirmed minimal cross-talk effects, supporting the robustness of the final design. The developed load cell met optimal design criteria, showing substantial improvements in sensitivity and accuracy over existing designs, with potential applications in automotive, aerospace, and engineering testing.
... This makes it difficult to achieve the desired measurement accuracy, set for the RSD to be at least 25 g. Secondly, in the context of force sensors, accuracy is affected by several factors, including nonlinearity, hysteresis, and inter-channel coupling [7]. These sources of error generally contribute to an overall uncertainty level of at least 0.01% of the full measurement scale, with some configurations reaching up to 3%, depending on the application and sensor design. ...
This paper presents the design, implementation, and laboratory validation of an optoelectronic-based mass estimation sensor for regolith sampling devices. The sensor integrates multiple photoresistors into the walls of a shovel of a sampling device, where the sensors detect varying levels of light occlusion caused by the deposited regolith. By analyzing the output signals from these photoresistors, the sensor estimates the mass of the sampled regolith. The device is designed to handle a typical sample mass range of 100–300 g. Laboratory tests demonstrated that the sensor can estimate the regolith mass with a relative error of approximately 23%, which is suitable for early-stage applications where rapid, non-invasive mass estimation is essential. The shown level of accuracy underscores the potential for further refining the calibration process, enhancing sensor sensitivity, and integrating multi-sensor approaches to improve performance. This conceptual study highlights the feasibility of using optoelectronic sensors for regolith mass estimation, paving the way for future innovations in ISRU missions and other granular material sampling applications. Future work will focus on the optimization of photoresistor placements, refining the calibration process, and enhancing sensor sensitivity to improve the accuracy of mass estimation.
... The primary challenge in multi-axis tactile sensing is not merely producing sensor outputs for both normal and shear loads but also efficiently decoupling-or independently measuring-the normal and shear force components. Considering that the majority of today's multi-axis force sensors have a rigid structure 19,20 , thereby limiting their applicability in various fields, researchers have developed many soft multi-axis tactile sensors based on a variety of transduction principles, including capacitance [21][22][23][24][25][26] , resistance [27][28][29] , optics [30][31][32][33][34][35][36][37][38] and magnetics [39][40][41][42][43][44][45][46] . The strategies for force decoupling in these sensors can be broadly categorized into two: (1) at the hardware level, which separates mechanically distinct sensing units that are sensitive to stimuli in single directions; and (2) at the software level, which employs data fitting methods to decouple raw sensor readings. ...
Electronic skins integrating both normal and shear force per taxel have a wide range of applications across diverse fields, including robotics, haptics and health monitoring. Current multi-axis tactile sensors often present complexities in structure and fabrication or require an extensive calibration process, limiting their widespread applications. Here we report an electronic soft magnetic skin capable of self-decoupling three-axis forces at each taxel. We use a simple sensor structure with customizable sensitivity and measurement range, reducing the calibration complexity from known quadratic (N²) or cubic (N³) scales down to a linear (3N) scale. The three-axis self-decoupling property of the sensor is achieved by overlaying two sinusoidally magnetized flexible magnetic films with orthogonal magnetization patterns. Leveraging the self-decoupling feature and its simple structure, we demonstrate that our sensor can facilitate a diverse range of applications, such as measuring the three-dimensional force distribution in artificial knee joints, teaching robots by touch demonstration and monitoring the interaction forces between knee braces and human skin during various activities.
... Finally, the main conclusion of this paper is summarized in section VI. Fig. 1. 3D 6-axis force/torque coordinate system [14]. Fig. 1 illustrates a multi-axis force/torque sensor. ...
The recent advancement of artificial intelligence, especially the Large Language Model and multimodal robot learning, promoted robotics development. The force/torque sensor is one of the essential components of robotics application since it is used to give the force feedback under operation. With accurate force measurement, robots can perform delicate manipulation control and safe interaction with humans. This review paper provides a comprehensive examination of force/torque sensor technologies. It highlights an in-depth analysis of sensing principles and calibration principles. In addition, the integration of the force/torque sensor and its fusion with other sensors for disturbance observer and collision detection is discussed. Some practical applications of force/torque sensors in robotics are thoroughly reviewed, illustrating their pivotal role in enhancing the functionality and interaction of robots in industrial automation, medical assistance, humanoid robotics, teleoperation, and embodied AI. Finally, the paper explores future sensor development directions.
... To achieve a sufficient sensitivity of the force measurement, the steel base of the MD head has a T-shaped beam for stress concentration (16) . The dimensions of the T-shaped beam are determined such that a high measurement sensitivity is achieved with a sufficient safety factor to prevent damage by using finite element analysis (FEA) (ANSYS workbench, Ansys, Inc., Canonsburg, US) (17) (18) . ...
To monitor processes of a tire changer that demounts a tire from a wheel, this paper proposes an end-effector with internally integrated force sensors and a process monitoring algorithm using its output. In the tire demounting processes, the tip of the proposed end-effector interacts with the tire and wheel rim. To measure the interaction force efficiently, the proposed end-effector is designed with a T-shaped beam for stress concentration, and the resulting strains along three orthogonal axes are detected by strain gauges. The sensor outputs are amplified and calibrated to decrease crosstalk and to improve accuracy. As a result, the proposed end-effector achieves high accuracy with a linearity of less than 1 % FS. To utilize the proposed end-effector for process monitoring, an algorithm is developed and experimentally validated on a tire changer. The experimental results show that the proposed end-effector can correctly monitor and detect errors in the tire demounting processes using the proposed algorithm with a high success rate of 97 %.
... Multi-axis force/moment sensors have been an area of research since the 70s, and various sensor designs have been developed. Over the years, the cross-beam structure has become one of the most preferred designs for multi-axis force/moment sensors in robotics and automation (Cao, Laws, and Baena 2021;Templeman, Sheil, and Sun 2020). Its popularity comes from the orthogonality between the force/moment and beam axes, which allows for easier sensor design compared to other sensor structures (Song and Fu 2019). ...
This study introduces a novel approximate model (AM) aimed at optimizing the design of cross-beam multi-axis force/moment sensor. It considers the characteristics of flexure hinges in elastic beams and the flexibility of beam joints, resulting in improved accuracy and broader solutions for equivalent stresses and natural frequencies compared to existing approximate models in the literature. Model validation is carried out by comparing the results with the finite element model in different cases that each case contains 1000 simulations. Validation cases combine different sensor dimensions with different forces, moments, material properties, and center hub shapes. Each validation case typically requires approximately 19 h using the finite element method (FEM) and just 1 sec with the AM. Furthermore, by using the Gaussian process and partial dependence plots, the sensitivity of the model accuracy on normalized sensor dimensions is investigated. The evaluation of model linearity and dimension normalization allows for the utilization of the novel approximate model beyond the provided dimension range, while still adhering to the normalized parameters. The implementation of AM in the design optimization problem demonstrates its suitability and advantages compared to existing literature and FEM results. When compared to finite element solutions within the sensor workspace, the approximate model exhibits a stiffness error of 5%, a strain error of 2%, a fundamental frequency error of 3%, and an equivalent stress error of 8%, while maintaining correlations of axial sensor properties above 98%.
... Based on the operating principles, force sensors can be divided into: resistive [10]- [11], piezoelectric [12]- [13], capacitive [14]- [15], pneumatic [16], hydraulic [17], inductive [18] and optical types [19]. Regarding DoF, sensors are either single-axis, detecting unidirectional forces, or three-dimensional, for multidirectional force measurement [20]. In multi-directional force measurement, the modeling of the elastic structure is important and can classified as: (a) three degrees-of-freedom (DOF) cross-beam [21]- [22], (b) six DOF cross-beam [23], (c) column-type [24], beam-column type [25] and (e) Stewart platform [26]. ...
This work introduces an advanced gripping force detection mechanism tailored for a 50kN electromechanical actuator. Central to this design is an intelligent chuck jaw, integrated with a novel compression force sensor. Employing finite element analysis (FEA), the properties of the chuck jaw were evaluated, guiding precise mechanical modifications. Additionally, a sophisticated compression force sensor and data acquisition system were developed. Rigorous testing of the prototype, which includes the drive motor and electromechanical actuator, was conducted under static and dynamic conditions. The static evaluation, against a standard force gauge, revealed a minimal deviation of about 1kN. Dynamic tests involved a force compensation mechanism to mitigate centrifugal force effects at high speeds, maintaining force stability with a 3.8% root mean square deviation, demonstrating the system effectiveness.
... These sensors are adept at discerning forces either generated by or exerted on a device. Their readings influence whether an operation should proceed, thus providing a vital safeguard for both the device and its user [68]. Force sensors are thus used for diverse purposes, such as quantifying the forces applied to robotic arm joints, guiding automated floor sweepers to alter their direction upon encountering walls, enabling tactile light controls, and notifying passengers of unsecured seat belts [69][70][71][72]. ...
Lower-limb rehabilitation exoskeletons offer a transformative approach to enhancing recovery in patients with movement disorders affecting the lower extremities. This comprehensive systematic review delves into the literature on sensor technologies and the control strategies integrated into these exoskeletons, evaluating their capacity to address user needs and scrutinizing their structural designs regarding sensor distribution as well as control algorithms. The review examines various sensing modalities, including electromyography (EMG), force, displacement, and other innovative sensor types, employed in these devices to facilitate accurate and responsive motion control. Furthermore, the review explores the strengths and limitations of a diverse array of lower-limb rehabilitation-exoskeleton designs, highlighting areas of improvement and potential avenues for further development. In addition, the review investigates the latest control algorithms and analysis methods that have been utilized in conjunction with these sensor systems to optimize exoskeleton performance and ensure safe and effective user interactions. By building a deeper understanding of the diverse sensor technologies and monitoring systems, this review aims to contribute to the ongoing advancement of lower-limb rehabilitation exoskeletons, ultimately improving the quality of life for patients with mobility impairments.
... Multiple six-axis force/moment (F/M) sensor designs exist [4,13,14,18,[23][24][25][26][27]. However, it is challenging to create a six-axis F/M-sensor that can resolve, at the same time, high load levels in some directions but small loads in other directions. ...
Background:
Rolling resistance and aerodynamic losses cause a significant part of a truck's energy consumption. Therefore there is an interest from both vehicle manufacturers and regulators to measure these losses to understand, quantify and reduce the energy consumption of vehicles. On-road measurements are particularly interesting because it enables testing in various ambient conditions and road surfaces with vehicles in service.
Objective:
Common driving loss measurement devices require unique instrumented measurement wheels, which hinders effective measurements of multiple tyre sets or measurements of vehicles in service. For this purpose, the objective is to develop a novel load-sensing device for measuring braking or driving torque.
Methods:
The strength of the measurement device is calculated using finite element methods, and the output signal is simulated using virtual strain gauge simulations. In addition to the signal simulation, the device is calibrated using a torsional test rig.
Results:
The simulation results confirm that the device fulfils the strength requirements and is able to resolve low torque levels. The output signal is simulated for the novel cascaded multi-Wheatstone bridge using the strains extracted from the finite element analysis. The simulations and measurements show that the measurement signal is linear and not sensitive to other load directions. The device is tested on a truck, and the effort of mounting the device is comparable to a regular tyre change.
Conclusions:
A novel driving loss measurement device design is presented with an innovative positioning of strain gauges decoupling the parasitic loads from the driving loss measurements. The design allows on-road testing using conventional wheels without requiring special measurement wheels or instrumentation of drive shafts, enabling more affordable and accurate measurements.
... ensors and encoders that can measure displacement or vibration, velocity, angle and force/torque are crucial for robotics and intelligent equipment to be aware of their own states and to perceive information about the environment. In particular, multiaxis force/torque sensors (MFSs) that can measure the force/torque of multiple axes simultaneously have wide applications in robotics and automatic machine systems [1,2]. MFS is a key component of robotic end-effectors for providing force and tactile sensing to achieve dexterous manipulation [3], delicate object handling and object recognition [4]. ...
Multiaxis force sensors (MFSs) are crucial for robotic manipulation and interaction in unstructured environments. Existing strain sensing-based MFSs usually have fixed functions and sensitivities, and are typically expensive, fragile, requiring complex fabrication and assembly. It is challenging to develop MFSs to meet the requirements of application scenarios. This paper presents a fully integrated, reconfigurable MFS (RMFS), which utilizes an array of PCB coils to detect the multiaxis displacement/rotation of a metal target at high resolution without mechanical or electrical connections. The RMFS design requires simple fabrication at very low cost and can be assembled in a few minutes. Basic characteristics, design criteria and calibration method of the RMFS were investigated. The RMFS prototype achieved an ultrahigh resolution of 1 mN for triaxial force sensing (0.005%), with a maximum error of 1.9% for 20 N loading, a maximum cross-talk error of 5.7%, and extremely small drifts, over 10 hours. Experiments show that the RMFS can respond rapidly and accurately to single and multiaxis force loadings. A reconfigured RMFS for
z
-axis force and
x/y
-axis torque sensing was realized by simply changing the metal target configuration. The RMFS shows promising features to be implemented in diverse applications from robotics, human-machine-interaction, and biomedical systems.
... To fabricate a 3-axis force sensor with this constitute, the conventional method typically involves using a machine tool to shape the raw metal material into a Maltese cross structure. Afterward, metal strain gauges are assembled through manually glue [22]. As a consequence, this approach presents shortcomings including complex fabrication process and high cost, with unwieldy structures. ...
Identification of magnitude and orientation for spatially applied loading is highly desired in the fields of not only the machinery components but also human-machine interaction. Despite the fact that the 3-axis force sensor with different structures has been proposed to measure the spatial force, there are still some common limitations including the multi-step manufacturing-assembly processes and complicated testing of decoupling calibration. Here, we propose a rapid fabrication strategy with low-cost to achieve high-precision 3-axis force sensors. The sensor is designed to compose of structural Maltese cross base and sensing units. It is directly fabricated within one step by a hybrid 3D printing technology combining deposition modeling (FDM) with direct-ink-writing (DIW). In particular, a machine learning (ML) model is used to convert the strain signal to the force components. Instead of a mount of calibration tests, this ML model is trained by sufficient simulation data based on programmed batch finite element modeling. This sensor is capable of continuously identifying a spatial force with varying magnitude and orientation, which successfully quantify the applied force of traditional Chinese medicine physiotherapy including Gua Sha and massage. This work provides insight for design and rapid fabrication of multi-axis force sensors, as well as potential applications.
... We thus undertook to design a low-cost, low-profile, easyto-fabricate and use sensing solution for manual tools to enable force feedback and control in remote guidance or robotic teleoperation, as well as the many other applications. There are multiple potential modalities for force/torque sensing, reviewed in [23], [24]. These include strain gauges [25], fibre Bragg gratings [26], elastomeric transducers [27], piezoresistive pads [28], optical deflection sensing [29], and capacitive sensing [23]. ...
p>Force/torque sensing on hand-held tools enables control of applied forces, which is often essential in both tele-robotics and remote guidance of people. However, existing force sensors are either bulky, complex, or have insufficient load rating. This paper presents a novel force sensing modality based on differential magnetic field readings in a collection of sensor modules placed around a tool or device. The instrumentation is easy to install and low profile, but nonetheless achieves good performance. A detailed mathematical model and optimization-based design procedure are also introduced. The modeling, simulation, and optimization of the force sensor are described and then used in the electrical and mechanical design and integration of the sensor into an ultrasound probe. Through a neural network-based nonlinear calibration, the sensor achieves average root-mean-square test errors of 0.41 N and 0.027 Nm compared to an off-the-shelf ATI Nano25 sensor, which are 0.80% and 1.16% of the full-scale range respectively. The sensor has an average noise power spectral density of less than 0.0001 N/sqrt(Hz), and a 95% confidence interval resolution of 0.063 N and 0.0086 Nm. The practical readout rate is 1.3 kHz over USB serial and it can also operate over Bluetooth or Wi-Fi. This sensor can enable instrumentation of manual tools to improve the performance and transparency of teleoperated or autonomous systems.</p
... We thus undertook to design a low-cost, low-profile, easyto-fabricate and use sensing solution for manual tools to enable force feedback and control in remote guidance or robotic teleoperation, as well as the many other applications. There are multiple potential modalities for force/torque sensing, reviewed in [23], [24]. These include strain gauges [25], fibre Bragg gratings [26], elastomeric transducers [27], piezoresistive pads [28], optical deflection sensing [29], and capacitive sensing [23]. ...
p>Force/torque sensing on hand-held tools enables control of applied forces, which is often essential in both tele-robotics and remote guidance of people. However, existing force sensors are either bulky, complex, or have insufficient load rating. This paper presents a novel force sensing modality based on differential magnetic field readings in a collection of sensor modules placed around a tool or device. The instrumentation is easy to install and low profile, but nonetheless achieves good performance. A detailed mathematical model and optimization-based design procedure are also introduced. The modeling, simulation, and optimization of the force sensor are described and then used in the electrical and mechanical design and integration of the sensor into an ultrasound probe. Through a neural network-based nonlinear calibration, the sensor achieves average root-mean-square test errors of 0.41 N and 0.027 Nm compared to an off-the-shelf ATI Nano25 sensor, which are 0.80% and 1.16% of the full-scale range respectively. The sensor has an average noise power spectral density of less than 0.0001 N/sqrt(Hz), and a 95% confidence interval resolution of 0.063 N and 0.0086 Nm. The practical readout rate is 1.3 kHz over USB serial and it can also operate over Bluetooth or Wi-Fi. This sensor can enable instrumentation of manual tools to improve the performance and transparency of teleoperated or autonomous systems.</p
... Resistance strain load cell is a kind of mechanical measurement sensor which is wildly used in various field such as industrial robotics [1,2], agriculture [3][4][5], medicine [6][7][8][9], sports industry [10,11], and many high-precision weighing applications [12][13][14][15][16][17]. It is a sensitive component that converts the deformation of the strain gage under force into an electrical signal [18]. ...
The return-to-zero error of the resistance strain load cell is most obvious in the first zero-return process during loading and unloading. To improve the accuracy of the load cell, it is necessary to figure out the cause of the error. The influence of the temperature, material, and weld cup were analyzed in this paper. It was concluded that the hysteresis is the main factor affecting the return-to-zero error after the first load. The relationship between hysteresis and zero-return error after first load was obtained by a data fitting algorithm. A method to improve the return-to-zero error after the first load was proposed.
... To address the issue of multi-directional strain detection, researchers have proposed various solutions [12][13][14][15][16]. Among them, color-tuning based on surface reflection is a mainstream approach for designing flexible multi-directional strain sensors [17][18][19]. ...
Strain sensors capable of recognizing the direction of strain are crucial in applications such as robot attitude adjustment and detection of strain states in complex structures. In this study, a sandwich-structured flexible biaxial strain sensor was developed using polydimethylsiloxane as the substrate, mechanoluminescent materials as the luminescent elements, and rubber-ink as the light-blocking layer. By correlating the emitted light color with the stretching state, precise identification of the applied strain direction is achieved. Additionally, the mechanoluminescence of the sensor is collected by a photodiode, generating photocurrent that can be analyzed. This provides a solution for practical applications of sensor.
... There are the cross-coupling interferences affecting the sensor precision much. The current techniques covering from the linear least-square model [8] to the nonlinear neural network [9], [10], support vector machine [11], and dynamic compensating networks [12], have been applied to the different MFS e.g. the robot wrist and medical applications [13], [14], [15], [16], [17]. ...
The multi-dimensional force/torque decoupling and calibration is extremely crucial to increase the accuracy of the Wheel Force Transducer/Sensor (WFT). A novel interpretable nonlinear decoupling and calibration approach to WFT is presented. A physical interpretable prime-error framework is developed such that the linear prime part accounts for most force-voltage responses while the nonlinear error part accounts for the gross error deviation. The conventional least-square decoupling is improved with the delicate nonlinear error modeling using a polynomial base module and a hyperbolic activation function. The developed framework is proved to be mathematically solvable and physically feasible by a two-step calibration scheme. A two-axis WFT is tested and compared with the proposed interpretable nonlinear decoupling model (IND), the least-square-based method (LSM), and the error-based neural network model (eNN). Results demonstrate that the proposed IND provides an accurate, practical, and effective scheme for modeling and calibrating WFTs and maintains a good balance among accuracy, generalization ability, and computational efficiency for real applications.
Purpose
Capacitive six-axis force/torque (F/T) sensors require various configurations to fulfill diverse performance requirements; however, a systematic method to assess the feasibility of any new configuration is lacking. This study aims to propose three criteria for evaluating the rationality of these configurations, enabling a quick determination of the feasibility of the initial structure of the sensor.
Design/methodology/approach
This study used sensitivity isotropy as a performance metric. By examining the signal conversion process from F/T to displacement using the compliance transformation matrix, the authors identified Criterion 1: the symmetry condition. By analyzing the decoupling process of the sensor, the authors discovered Criterion 2: the capacitor arrangement condition. Through the optimization of analog sensors, this study derived Criterion 3: the range and structural parameters conditions. Ultimately, this study designed and fabricated a sensor that fulfills these criteria, thereby demonstrating the feasibility of the approach through its performance.
Findings
By analogy with capacitive six-axis F/T sensors that have demonstrated exceptional performance in recent years, the authors have found that they all meet the criteria proposed in this paper. Furthermore, the sensor designed and fabricated in this study achieves an accuracy of 0.64% FS, surpassing both the accuracy and sensitivity of the commercially available high-performance ATI industrial automation (Gamma) sensor. This underscores the feasibility of this study’s criteria.
Originality/value
By following the configuration guidelines presented in this paper, designers can quickly assess whether a new configuration will perform well at the early stages of the design process. This makes it easier to consider other requirements while meeting the basic performance needs, thereby significantly enhancing design efficiency.
We designed a sophisticated smart soft tissue material that simulates the properties of biological soft tissue and detects three-dimensional force. Inspired by electronic skin, this material uses capacitive pressure sensors and multi-layer sensor packaging. Finite element analysis and multi-field simulation were employed for structural design and verification. The study evaluated the theory and practicality of a flexible capacitive 3D force sensor for detecting pressure and shear force. Mechanical and electrical properties were confirmed through force and electric field simulations. The 3D force detection method proved feasible, achieving sensitivity levels of 10 ⁻⁴ kPa ⁻¹ in the X and Y directions, and 10 ⁻³ kPa ⁻¹ in the Z direction, demonstrating the effectiveness of our design.
Miniaturized six-axis force/torque sensors have potential applications in robotic tactile sensing, minimally invasive surgery, and other narrow operating spaces, where currently available commercial sensors cannot meet the requirements because of their large size. In this study, a silicon-based capacitive six-axis force/torque sensing chip with a small size of 9.3 × 9.3 × 0.98 mm was designed, fabricated, and tested. A sandwich decoupling structure with a symmetrical layered arrangement of S-shaped beams, comb capacitors, and parallel capacitors was employed. A decoupling theory considering eccentricity and nonlinear effects was derived to realize low axial crosstalk. The proposed S-shaped beams achieved a large measurement range through stress optimization. The results of a coupled multiphysics field finite-element simulation agreed well with those of theoretical analyses. The test results show that the proposed sensing chip can detect six-axis force/torque separately, with almost all crosstalk errors less than 6%FS. Its force and torque measurement ranges can reach as much as 2.5 N and 12.5 N·mm, respectively. The sensing chip also has high sensitivities of 0.52 pF/N and 0.27 pF/(N·mm) for force and torque detection, respectively.
Measuring interaction forces between robots and humans is a major challenge in physical human–robot interactions. Nowadays, conventional force/torque sensors suffer from bulkiness, high cost, and stiffness, which limit their use in soft robotics. Thus, we introduce a novel torque sensor manufactured with material extrusion technology. Our approach relies on capacitive structures, which are at the same time the deformable and sensing parts of the sensor, making it very compact. These structures are made in one single print, simplifying the manufacturing process compared to traditional torque sensors. The sensor characteristics can be modulated thanks to material extrusion technology. We conduct experiments in a dedicated test bench to characterize the proposed torque sensor. From the characterization results, we implement a torque estimator based on the deformation angle estimate calculated from capacitance changes. The proposed torque sensor is able to measure torques within a
2.5 N
m range with a maximum error of 6% up to a deformation angle velocity of
. It is also able to measure its deformation angle with a maximum error of
. The accuracy of our sensor makes it suitable to ensure fine control in physical human–robot interaction applications.
This paper describes the design, development, calibration and validation of a novel soil-structure contact stress sensor. The new sensor design combines a novel operating principle, fibre Bragg grating (FBG) strain sensing and data-driven mapping techniques to create a multi-axis contact stress sensor that is both economical and suitably robust for deployment in underground construction applications. The instrumentation process is informed using a ‘virtual twin’ of the sensor in which synthetic data is generated by extracting and interpolating virtual FBG strains obtained from a large number of 3D finite element calculations. A physical prototype is subsequently developed to demonstrate proof of concept. Results from laboratory validation tests give confidence in the sensor's ability to provide accurate contact stress measurements in typical soil-structure interface shear applications. In particular, the novel sensor structure and operating principle was shown to achieve excellent measurement of effective normal stress. The new sensor design harnesses many of the inherent benefits of FBGs including immunity to electromagnetic noise and water ingress, and the use a single lightweight cable and connector, which significantly simplifies installation on site compared to electrical multi-axis sensors.
A profound insight into fundamental principle, historical perspective, recent attempts (state of the art) and future research opportunities concerned with development of drawbar dynamometer for tractor platforms (vehicles and robots) are conducted within framework of present review research. The research systematically reviews and analyses 934 official documents published over past one century (1924–2024). Descriptions in accordance with advantages and disadvantages of six conventional types of the dynamometer (portable spring, portable hydraulic, mountable electrical, portable electrical, portable load cell, and portable vehicle dynamometer) with various transducers (spring, pressure gauge, and strain gauge) and fixtures (hydraulic cylinder, drawbar hinge, circular ring, extended octagonal ring, double extended octagonal ring, rectangular frame, shaped frame, and load pin) are expounded from different points of view. Salient results of the research elucidate that development of portable electrical dynamometer was notably higher than other ones. Howbeit, application of portable load cell dynamometer has been generally accepted by research community. Future researches must be oriented toward development of novel type of transducers for smart contact and noncontact measuring (fiber Bragg grating, vibration, self-inductance eddy current, radiated acoustic, microwave interferometric radar, three-dimensional laser scanning, and vision system method) of drawbar pull. The transducers of these measuring methods should be developed based on the ISO 11783 and IEEE 1451 standards. Meanwhile, the transducers and data acquisition unit can be linked by means of fifth or sixth generation of communication technology of Internet of Things. Overall, it can be strongly asserted that the research results are not only applicable for drawbar pull measuring of manned and unmanned tractor platforms, but also profitable for sensor development associated with measuring of axial pulling force.
Force/torque sensing on hand-held tools enables control of applied forces, which is often essential in both tele-robotics and remote guidance of people. However, existing force sensors are either bulky, complex, or have insufficient load rating. This paper presents a novel 6 axis force-torque sensor based on differential magnetic field readings in a collection of low-profile sensor modules placed around a tool or device. The instrumentation is easy to install but nonetheless achieves good performance. A detailed mathematical model and optimization-based design procedure are also introduced. The modeling, simulation, and optimization of the force sensor are described and then used in the electrical and mechanical design and integration of the sensor into an ultrasound probe. Through a neural network-based nonlinear calibration, the sensor achieves average root-mean-square test errors of 0.41 N and 0.027 Nm compared to an off-the-shelf ATI Nano25 sensor, which are 0.80% and 1.16% of the full-scale range respectively. The sensor has an average noise power spectral density of less than 0.0001 N/
, and a 95% confidence interval resolution of 0.0086 N and 0.063 Nmm. The practical readout rate is 1.3 kHz over USB serial and it can also operate over Bluetooth or Wi-Fi. This sensor can enable instrumentation of manual tools to improve the performance and transparency of teleoperated or autonomous systems.
Torque sensors find utility across diverse domains, such as drive and conveyor technology, robotics, and research and development. Multiple sensing principles are applicable for torque measurement. Notably, the resistive effect, utilizing strain gauges, is a prevalent method. In recent years, 3D printing technology has experienced significant growth, facilitating the production of physical objects and functional structures through a number of 3D printing processes and materials. As a result, 3D printing has attracted attention in the field of printed electronics and sensors, leading to various sensor developments in research projects using 3D printing techniques. This review offers an overview of the current state of research concerning 3D-printed torque sensors. In terms of transparency, this review adheres to the PRISMA method, a systematic literature review approach. The identified sensors undergo analysis based on sensing principles, 3D printing processes, printing materials, and the extent of 3D printing application. Furthermore, prospective research directions are delineated.
Purpose
The six-axis force/torque sensor based on a Y-type structure has the advantages of simple structure, small space volume, low cost and wide application prospects. To meet the overall structural stiffness requirements and sensor performance requirements in robot engineering applications, this paper aims to propose a Y-type six-axis force/torque sensor.
Design/methodology/approach
The performance indicators such as each component sensitivities and stiffnesses of the sensor were selected as optimization objectives. The multiobjective optimization equations were established. A multiple quadratic response surface in ANSYS Workbench was modeled by using the central composite design experimental method. The optimal manufacturing structural parameters were obtained by using multiobjective genetic algorithm.
Findings
The sensor was optimized and the simulation results show that the overload resistance of the sensor is 200%F.S., and the axial stiffness, radial stiffness, bending stiffness and torsional stiffness are 14.981 kN/mm, 16.855 kN/mm, 2.0939 kN m/rad and 6.4432 kN m/rad, respectively, which meet the design requirements, and the sensitivities of each component of the optimized sensor have been well increased to be 2.969, 2.762, 4.010, 2.762, 2.653 and 2.760 times as those of the sensor with initial structural parameters. The sensor prototype with optimized parameters was produced. According to the calibration experiment of the sensor, the maximum Class I and II errors and measurement uncertainty of each force/torque component of the sensor are 1.835%F.S., 1.018%F.S. and 1.606%F.S., respectively. All of them are below the required 2%F.S.
Originality/value
Hence, the conclusion can be drawn that the sensor has excellent comprehensive performance and meets the expected practical engineering requirements.
The integration of advanced sensor technologies has significantly propelled the dynamic development of robotics, thus inaugurating a new era in automation and artificial intelligence. Given the rapid advancements in robotics technology, its core area—robot control technology—has attracted increasing attention. Notably, sensors and sensor fusion technologies, which are considered essential for enhancing robot control technologies, have been widely and successfully applied in the field of robotics. Therefore, the integration of sensors and sensor fusion techniques with robot control technologies, which enables adaptation to various tasks in new situations, is emerging as a promising approach. This review seeks to delineate how sensors and sensor fusion technologies are combined with robot control technologies. It presents nine types of sensors used in robot control, discusses representative control methods, and summarizes their applications across various domains. Finally, this survey discusses existing challenges and potential future directions.
The measurement accuracy of capacitive six-axis force/torque (F/T) sensors is difficult to predict and determine during the design process, which leads to the uncertainty of the actual measurement accuracy of the sensor. In this paper, a sensor accuracy prediction method based on an error analysis model is proposed. A mathematical model for mapping the six-axis F/T to changes in capacitance is established by computing the overall flexibility matrix of the elastic structure. The influence mechanism of various errors on the measurement accuracy of the six-axis F/T sensor system is deeply analyzed, and a mathematical model for error prediction and a comprehensive performance evaluation index function is established. The comprehensive performance evaluation index function is proposed, coupled with applying a nonlinear programming genetic algorithm for parameter optimization. A prototype was fabricated using the optimization results and calibration experiments were conducted to verify its accuracy. The experimental results demonstrate that the nonlinearity error of the prototype is 0.280% Full Scale (FS), and the calibration measurement accuracy is 0.601%FS. The design method proposed in this paper effectively enables the development of high-precision capacitive six-axis F/T sensors.
Multi-dimensional force sensors are extensively utilized in industrial milling machining for measuring cutting force and in intelligent robot applications for measuring joint force. These sensors offer several advantages, including improved static characteristics, well-established static calibration techniques, and temperature compensation technology. However, with the increasing demand for measuring dynamic forces in various applications, force sensors need to possess enhanced dynamic characteristics. Unfortunately, strain force sensors typically exhibit low intrinsic frequency and damping ratio, resulting in slower dynamic response of the sensor.To address this issue and enhance the dynamic performance of multidimensional force sensors, this study proposes a dynamic compensation method based on an improved sparrow search algorithm.Chebyshev chaotic mapping was implemented to increase randomness and ergodicity in the initial population. An adaptive weight factor was incorporated to improve the position update formula of finders and the ratio of vigilantes. These changes enhanced the algorithm’s ability to conduct early global searches and late local depth mining. Subsequently,
t
-distribution changes and Chebyshev chaotic perturbations were introduced to expand the local search capability.The enhanced sparrow search algorithm improves the optimization capabilities of the original algorithm. By utilizing dynamic calibration experimental data from three-dimensional force sensors, the algorithm’s effectiveness was verified. The results indicate that the method successfully reduces the overshooting amount in each channel of the sensors and shortens the regulation time. Consequently, the dynamic performance of the three-dimensional force sensors is improved, and the algorithm proves to be effective, practical, and robust in compensating for the sensors’ dynamic behavior.
Although the potential demand for force sensors in both robotics and automation is high, the complexity of their structure increases the number of manufacturing processes. As a result, the rising cost of sensors has hindered the practical application of force measurement and force control. In this study, a flexure element is proposed, consisting of a structure that is easier to cut and process than conventional ones. Additionally, holes through the side of a cuboid are incorporated to simplify the manufacturing of force sensors. To ensure the safety of the proposed sensor design, an approximate equation is derived to predict the maximum von Mises stress on the flexure element using design parameters. Subsequently, we clarified a way to attach the strain gauge in a position that improves sensitivity. The results of the actual prototype sensor based on the proposed method show that the maximum nonlinearity error and decoupling error in the other axes are 0.442 %R.O. and 0.660 %R.O., respectively, and the performance is comparable to that of conventional force sensors. Because the prototype has a difference in resolution between the axes, a method for improving the resolution isotropy without changing the difficulty of machining is also proposed. In addition, the validity of the proposed method is demonstrated using experiments. Consequently, a force sensor with the same level of performance was developed using the proposed method, and the cutting process was made easier compared to that of conventional methods. This research is expected to lead to lower cost force sensors in the future.
Flexible three-dimensional (3D) force sensors have been extensively investigated in the field of robotics due to their ability to provide feedback information from multiple directions. However, the development of flexible 3D force sensors with high sensitivity and decoupling capabilities remains a significant challenge, hindering the ability of robots to perceive their external environment. In this letter, we present a novel flexible 3D force iontronic sensor (FTIS) that utilizes ionic materials with micro-pyramidal structures and a backpropagation (BP) neural network method based on deep learning. The FTIS exhibits outstanding sensitivity, with over 8000
in the normal direction and over 4000
in the shear direction, and has a rapid response time of 27-ms. Additionally, it demonstrated stable working durability, with over 8000 cycles without signal delay. To validate the utility of the sensor, we integrated it as a machine-sensing interface on a mechanical claw to measure changes in forces in the triaxial direction. Our design concept has the potential to advance the development of multidimensional force sensors in the future.
Soft multi-axis force sensors are essential in automation and robotic manipulations for dexterous applications. Carbon-based composites are quality candidates for sensing elements of soft multi-axis force sensors due to its piezoresistivity originated from electron tunneling effect. However, low cost and fast-prototyped soft multi-axis force sensors based on tunneling effect of carbon-based composites are still in their infant. This work investigated a soft multi-axis forces sensor utilizing Velostat film strips as the core sensing elements. A unique serpentine structure of Velostat strips has been designed and implemented as piezoresistors for the soft force sensor. The sensitivity of the proposed multi-axis force sensor has been characterized in x, y and z directions. Experimental results show that the sensor can achieve 2.1%/N and 2.2%/N in x and y axis, and 4.2%/N in z axis, respectively. The force sensor has been implemented in dexterous manipulations with a robotic gripper as the proof-of-concept, which demonstrates great potential for multi-axis force sensing applications.
In this work we present the design process, the characterization and testing of a novel three-axis mechanical force sensor. This sensor is optimized for use in closed-loop force control of haptic devices with three degrees of freedom. In particular the sensor has been conceived for integration with a dual finger haptic interface that aims at simulating forces that occur during grasping and surface exploration. The sensing spring structure has been purposely designed in order to match force and layout specifications for the application. In this paper the design of the sensor is presented, starting from an analytic model that describes the characteristic matrix of the sensor. A procedure for designing an optimal overload protection mechanism is proposed. In the last part of the paper the authors describe the experimental characterization and the integrated test on a haptic hand exoskeleton showing the improvements in the controller performances provided by the inclusion of the force sensor.
This paper presents a three-dimensional force sensor based on fiber Bragg grating (FBG) for robot plantar force measuring. A classical Maltese-cross beam with multiplexed FBGs has been designed for three-dimensional force sensing. Strain distribution characteristics and dynamic performance of the Maltese-cross elastomer have been investigated by using finite element analysis (FEA). Through ingenious design, three-dimensional forces of Fx, Fy, and Fz have been measured by only five sensitive elements of FBG, meanwhile, decoupling and temperature compensation have also been realized, which greatly reduces the number of sensitive element compared with the traditional resistance strain gauge based multi-axis force sensor. Comprehensive performance test has been carried out, and the experimental results demonstrate that the sensor possesses good linearity, weak coupling, and creep resistance.
Interest in low-cost force-torque sensors with high performance will continue to increase in the next years, as robot control needs to rely on more sensors to move into the human environment. Existing force-torque sensors still suffer from some shortcomings such as noise sensitivity, low resolution and high cost. This limits their use in some emerging applications. Through an advanced systematic design method based on a symbolic formulation of the wrench-displacement relationship, we designed compact and cost-effective three-axis capacitance-based force sensor. Despite its relative simplicity, our sensor exhibits a very good sensitivity thanks to the electronic components selected, but also to a special soft silicone layer filled with nanoparticles of ferroelectric ceramic. This composite we made has a relatively high dielectric constant. This paper presents the design process that led to the sensor including the structure, the capacitance measurement circuit and the fabrication of the soft dielectric. Characterization tests have also been carried out on a prototype of the sensor
This document presents the design of a 6-degree of
freedom fiberoptic force-torque-sensor for integration in instruments for minimally invasive robotic surgery. The measuring system based on fiber Bragg gratings as well as the calibration procedure are explained. Measurement properties of the sensor are verified in a test setup.
A three-axial silicon based force sensor with a volume less than 7mm3, developed for biomechanical measurements, has been characterized. Results obtained with two different experimental test benches are reported in this paper. High linearity and low hysteresis during sensor normal loading have been obtained by using a preliminary test bench. A second improved test bench, based on a six-components load cell, has been employed to perform a reliable sensor calibration. A sensitivity matrix has been evaluated from experimental data and an estimation of force accuracy has been determined. The experimental sensitivity in the shear directions is 0.054N−1 and in the normal direction is 0.026N−1. A method for comparing the device characteristics with similar state of the art three-axial force sensors has been provided.
The use of piezoresistivematerials as strain gauges and in the measurement of displacement, force, and torque is discussed generally. A torsional transducer which has been constructed from n‐type germanium is described, and the experimentally obtained voltage‐torque characteristic given.
The reduced access conditions of minimally invasive surgery and therapy (MIST) impair or completely eliminate the feel of tool—tissue interaction forces. Many researchers have been working actively on the development of force sensors and sensing techniques to address this problem. The goal of this survey article is to summarize the state of the art in force sensing techniques for medical interventions in order to identify existing limitations and future directions. A literature search was performed from January to July 2009 using a combination of keywords relevant to the area, including force, sensor, sensing, haptics, and minimally invasive surgery.
The literature search resulted in 126 articles with valuable content. This article presents a summary of the force sensing technologies, design specifications for force sensors in clinical applications, force sensors and sensing instruments that have been developed for MIST, and the experiments performed to determine the need for force information. Open areas of research include force sensor design, development of alternative methods of sensing, assessment of the impact of force information on performance, determination of the benefits of haptic information, and evaluation of the human factors involved in the processing and use of force information.
A sensing element of column type was devised as a multi-component force/moment sensor by attaching strain gages. The ratio of length over diameter (L/D) for the sensing element was designed analytically and verified by finite element analysis. In order to reduce the interference error of each loading component, this paper proposed a decoupling method with the addition and subtraction processes using signals of strain gages. Finally the calibration showed that the interference error of Fx component was less than 7.3% FS, and in case of other components, 5.0% FS.
Robotic control and force-feedback applications require multi-axial force and torque sensing. One possible implementation of future sensors is seen in fiber optic force torque sensors, since the signal demodulation may be located in some distance to the actual sensor and they also do not have to include any magnetic material. This article presents a fiber Bragg grating-based force and torque sensor with six degrees of freedom. The general setup resembles a Stewart platform. Its connecting beams are formed by the fiber used to measure the deformation of the transducer. The element creating stiffness may be of arbitrary form. We demonstrate how the sensor is realized and show results of all six force and torque measurements. We present a theoretical model of the sensor. The results in this work demonstrate the feasibility of a fiber-optic force-torque sensor.
This paper describes the development of a six-axis force/moment sensor and its control system for an intelligent robot's gripper. An intelligent robot's gripper should detect the forces Fx (x-direction force), Fy and Fz in the gripping direction and in the gravitational direction, and be controlled by the measured forces and the gripper's control system to safely grasp an unknown object. Also, it should detect the moments Mx (x-direction moment), My and Mz to accurately perceive the position of the object in the grippers. Therefore, an intelligent robot's gripper should be composed of a six-axis force/moment sensor which can measure the forces Fx, Fy and Fz, and the moments Mx, My and Mz simultaneously. It is required that each component sensor of the six-axis force/moment sensor generally has the same rated output, and the same capacity (e.g. Fx = Fy = Fz = 50 N, Mx = My = Mz = 5 N m) or different capacity (e.g. Fx = 40 N, Fy = 50 N, Fz = 60 N, Mx = 4 N m, My = 3 N m, Mz = 5 N m) in each force component and moment component in the gripper, depending on the particular application. The control system should have a fast processing speed for measuring the signals of the sensors and controlling the gripper without much delay time, and should be of small size. The grippers are made with a force sensor which can detect force in only one direction. The control system consists of a personal computer and an A/D, D/A converter board.
In this paper, a six-axis force/moment sensor using parallel-plate beams is designed and fabricated to make an intelligent robot's gripper; the gripper's control system is designed and manufactured using a digital signal processor.
Stroke is a common condition resulting in 30,000 people per annum left with significant disability. In patients with severe arm paresis after stroke, functional recovery in the affected arm is poor. Inadequate intensity of treatment is cited as one factor accounting for the lack of arm recovery found in some studies. Given that physical therapy resource is limited, strategies to enhance the physiotherapists' efforts are needed. One approach is to use robotic techniques to augment movement therapy.
A three degree-of-freedom pneumatic robot has been developed to apply physiotherapy to the upper limb. The robot has been designed with a workspace encompassing the reach-retrieve range of the average male. Control experiments have applied force and then position only controllers to the pneumatic robot. These controllers are combined to form a position-based impedance control strategy on all degrees of freedom of the robot. The impedance controller performance was found to be dependent upon the specified impedance parameters. Initial experiments attaching the device to human subjects have indicated great potential for the device.
Haptic perception plays a very important role in surgery. It enables the surgeon to feel organic tissue hardness, measure tissue properties, evaluate anatomical structures, and allows him/her to commit appropriate force control actions for safe tissue manipulation. However, in minimally invasive surgery, the surgeon's ability of perceiving valuable haptic information through surgical instruments is severely impaired. Performing the surgery without such sensory information could lead to increase of tissue trauma and vital organic tissue damage. In order to restore the surgeon's perceptual capability, methods of force and tactile sensing have been applied with attempts to develop instruments that can be used to detect tissue contact forces and generate haptic feedback to the surgeon. This paper reviews the state-of-the-art in force and tactile sensing technologies applied in minimally invasive surgery. Several sensing strategies including displacement-based, current-based, pressure-based, resistive-based, capacitive-based, piezoelectric-based, vibration-based, and optical-based sensing are discussed.
- Force Displacement
Displacement, Force, and Torque, J. Acoust. Soc. Am. 29 (1957) 1096-1101.
Force and Tactile Sensing for Minimally Invasive Surgery
Force and Tactile Sensing for Minimally Invasive Surgery, IEEE Sens. J. 8 (2008) 371-381.
force/moment sensor using plate-beams
force/moment sensor using plate-beams, Meas. Sci. Technol. 10 (1999) 295-301.
Sensor with Six Degrees of Freedom
Sensor with Six Degrees of Freedom, Int. J. Optomechatronics. 3 (2009) 201-214.
A Three-Axis Force Sensor for Dual 446
- M Fontana
- S Marcheschi
- F Salsedo
- M Bergamasco
M. Fontana, S. Marcheschi, F. Salsedo, M. Bergamasco, A Three-Axis Force Sensor for Dual
446