Project

Continuum Manipulators Modeling and Control

Goal: Modelling, path planning, control of stiffness controllable continuum manipulators

Updates
0 new
1
Recommendations
0 new
0
Followers
0 new
47
Reads
0 new
411

Project log

S.M.Hadi Sadati
added 2 research items
The concept of continuum and soft robotics has opened new abilities that were previously unachievable by rigid robotics alone, such as squeezing, growing, and morphing to their environments. As an example, Concentric Tube Robots (CTR) are continuum robots made of a series of pre-curved, elastic tubes where each tube can individually be rotated, as well as extended and recalled; interactions between each tube allows for turns and twists, giving control over the length and configuration of the robot. CTRs can assist in minimally invasive surgery (MIS) to access difficult to reach areas, due to the intricate human anatomy, with advantages including single-site entry and their malleable nature [1]. However, utilizing CTRs, and continuum robots in general, are not without their own challenges. Due to the complex nature of a continuum structure, fast and accurate simulations are still in development and require specific skills to operate. These simulations are not usually accurate due to the complex behaviours of the materials used and their deformable nature. SOFA (Simulation Open Framework Architecture) was introduced as an open-source platform to address some of the challenges with real-time physics-based simulation of interaction with deformable tissue in medical applications and later for modelling soft robots. More specifically, a BeamAdapter plugin2 was developed based on interpolation of a continuous geometry over multiple consecutive Timoshenko beam segments to address the simulation challenges of neurovascular interventions using interleaved catheters and guidewires [2]. The BeamAdapter plugin has been also utilized for interactive planning of coil embolization in brain aneurysms [3] and interactive training system for interventional electrocardiology procedures [4]. We have recently developed a Reduced-Order dynamic model for CTRs based on the shape interpolation of the robot backbone and showcased its real-time performance, correct estimation of the path-dependent motions and snapping instances, accurate simulations of stable and post-snapping motions in an experimental comparative study [5]. In this paper, we outline the process and the code on how a CTR model can be implemented into an example scene provided as a part of the SOFA-framework ‘BeamAdapter’ plugin [2].
Yohan Noh
added a research item
The miniaturization of robotic applications such as flexible manipulators or robotic prosthetics while maintaining high-precision closed-loop position control faces the challenge of integrating all their mechanisms, sensors, and actuators within a limited space. For this reason, position sensors are usually installed outside the actuated joints, by for example using a wire (tendon)-driven system. In this case, high-precision position control may not be guaranteed due to wire slack or wire deformation caused by high tension. As such, this paper presents an optoelectronic based joint measurement sensor capable of not only being integrated directly within joints of a versatile range of robotic applications, but also enhancing further miniaturization of these robot applications. Using a variable thickness reflecting surface for proximity-based intensity modulation, the proposed sensing system is shown to be able to measure a larger angular range of [0-140°], with increased sensitivity (0-3.5 V) along with investigation of a light intensity model for estimation of sensor output.
Yohan Noh
added a research item
this paper presents the novel design of an optical shape sensing method using optoelectronic sensors, for integration into flexible soft robotic manipulators, to measure pose in two orientations. Shape sensing in soft robotic tools that allow stable and accurate position control in Minimally Invasive Surgery is critical, although innovations are yet to be explored in a simple, cost-effective sensing technique. Presented in this work is a continuation of the work of Koh et.al [1], with demonstration of the use of a designed 4-plate tendon-actuated flexible manipulator and optimised design parameters for the sensing principle. Developed calibration platform shows an increase in accuracy for shape sensing using linear and non-linear regression models. Further development is required on miniaturisation to refine accuracy and targeted application.
S.M.Hadi Sadati
added 3 research items
The direct relationship between early-stage breast cancer detection and survival rates has created the need for a simple, fast and cheap method to detect breast cancer at its earliest stages. Endoscopic evaluation of the mammary ducts known as ductoscopy has great potential to detect early breast cancers. Unfortunately, there are technical limitations, most notably lack of steerability and high tissue damage, limiting its practicality. A promising alternative to rigid endoscopy tools is the use of soft robots.
Continuum surgical robots can navigate anatom-ical pathways to reach pathological locations deep inside thehuman body. Their flexibility, however, generally comes with re-duced dexterity at their tip and limited workspace. Building onrecent work on eccentric tube robots, this paper proposes a newcontinuum robot architecture and theoretical framework thatcombines the flexibility of push/pull actuated snake robots andthe dexterity offered by concentric tube robotic end-effectors.We designed and present a prototype system as a proof-of-concept, and developed a tailored quasistatic mechanics-basedmodel that describes the shape and end-effector’s pose for thisnew type robotic architecture. The model can accommodate anarbitrary number of arms placed eccentrically with respect tothe backbone’s neutral axis. Our experiments show that theerror between model and experiment is on average 3.56% ofthe manipulator’s overall length. This is in agreement with stateof the art models of single type continuum architecture.
S.M.Hadi Sadati
added a research item
Continuum robots can traverse anatomical pathways to intervene in regions deep inside the human body. They are able to steer along 3D curves in confined spaces and dexterously handle tissues. Concentric tube robots (CTRs) are continuum robots that comprise a series of precurved elastic tubes that can be translated and rotated with respect to each other to control the shape of the robot and tip pose. CTRs are a rapidly maturing technology that has seen extensive research over the past decade. Today, they are being evaluated as tools for a variety of surgical applications, as they can offer precision and manipulability in tight workspaces. This review provides an exhaustive classification of research on CTRs based on their clinical applications and highlights approaches for modeling, control, design, and sensing. Competing approaches are critically presented, leading to a discussion of future directions to address the limitations of current research and its translation to clinical applications. Expected final online publication date for the Annual Review of Control, Robotics, and Autonomous Systems, Volume 5 is May 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
S.M.Hadi Sadati
added a research item
This letter presents MAMMOBOT, one of the first millimetre-scale steerable soft growing robots for medical applications. MAMMOBOT aims to access the breast through the nipple and navigate the mammary ducts to detect precursors of invasive breast cancers. Addressing limitations of the state-of-the-art, MAMMOBOT maintains a hollow inner lumen throughout its soft body, enabling the passing of instruments such as miniature endoscopes, biopsy needles, and optical probes for in situ histopathology. MAMMOBOT is developed by a novel manufacturing approach entailing dual LDPE sheet adhesion with localised heat treatment. MAMMOBOT's steerability is achieved through a sub-millimetre profiled tendon-driven catheter that passes through its inner lumen. A duty cycle controller governs steering versus growing to achieve navigation in complex environments within a human-in-the-loop framework. Benchtop experimental evaluation demonstrates the robot's capabilities and agreement with a Reduced-Order Mode (ROM) of its dynamics. Finally, experimental evaluation on a bespoke breast phantom developed for the purposes of this project demonstrates the clinical relevance and potential impact of MAMMOBOT.
S.M.Hadi Sadati
added a research item
This paper presents MAMMOBOT, one of the first millimetre-scale steerable soft growing robots for medical applications. MAMMOBOT aims to access the breast through the nipple and navigate the mammary ducts to detect precursors of invasive breast cancers. Addressing limitations of the state-of-the-art, MAMMOBOT maintains a hollow inner lumen throughout its soft body, enabling the passing of instruments such as miniature endoscopes, biopsy needles, and optical probes for in situ histopathology. MAMMOBOT is developed by a novel manufacturing approach entailing dual LDPE sheet adhesion with localised heat treatment. MAMMOBOT's steerability is achieved through a sub-millimetre profiled steerable catheter that passes through its inner lumen. A duty cycle controller governs steering versus growing to achieve navigation in complex environments within a human-in-the-loop framework. Benchtop experimental evaluation demonstrates the robot's capabilities and agreement with a Reduced Order Model (ROM) of its mechanics. Finally, experimental evaluation on a bespoke breast phantom developed for the purposes of this project demonstrates the clinical relevance and potential impact of MAMMOBOT.
S.M.Hadi Sadati
added a research item
Soft robots' natural dynamics calls for the development of tailored modeling techniques for control. However, the high-dimensional state space of the commonly practiced modeling approaches for soft robots, i.e. Cosserat rod and Finite Element Methods, has been identified as a key obstacle in controller design. To address this niche, Reduced-Order Modeling (ROM) and Model Order Reduction (MOR) have recently been extensively investigated. Although these techniques serve a similar purpose, they are radically different in their assumptions and implementation. This review paper provides the first in-depth comparison of ROM and MOR techniques to aid Soft Robotics researchers in selecting computationally efficient models.
S.M.Hadi Sadati
added a research item
Concentric tube robots (CTRs) are continuum robots that can navigate the lumen to reach surgical targets that are deep inside the body. While CTRs have been extensively studied in quasistatic conditions, limited work on their dynamic modeling exists. This paper presents the dynamic modelling of CTR using Reduced-Order Modeling (ROM) by Polynomial Shape (PS) parametrization of a continuum curve. We expand TMTDyn, our theoretical modeling software package, and showcase the capturing of snapping (sudden release of elastic energy) behaviour as well as hysteresis for the first time. Our methods are experimentally verified using a CTR.Results are extensively compared with state-of-the-art CTR models (curvature superposition, and differential curvature kinematics) showcasing clear advantages.
Ahmad Ataka Awwalur Rizqi
added a research item
In the last decade, soft robots have been at the forefront of a robotic revolution. Due to the flexibility of the soft materials employed, soft robots are equipped with a capability to execute new tasks in new application areas-beyond what can be achieved using classical rigid-link robots. Despite these promising properties, many soft robots nowadays lack the capability to exert sufficient force to perform various real-life tasks. This has led to the development of stiffness-controllable inflatable robots instilled with the ability to modify their stiffness during motion. This new capability, however, poses an even greater challenge for robot control. In this paper, we propose a model-based kinematic control strategy to guide the tip of an inflatable robot arm in its environment. The bending of the robot is modelled using an Euler-Bernoulli beam theory which takes into account the variation of the robot's structural stiffness. The parameters of the model are estimated online using an observer based on the Extended Kalman Filter (EKF). The parameters' estimates are used to approximate the Jacobian matrix online and used to control the robot's tip considering also variations in the robot's stiffness. Simulation results and experiments using a fabric-based planar 3-degree-of-freedom (DOF) inflatable manipulators demonstrate the promising performance of the proposed control algorithm.
S.M.Hadi Sadati
added a research item
This paper presents a medical robotic system for deep orbital interventions, with a focus on Optic Nerve Sheath Fenestration (ONSF). ONSF is a currently invasive ophthalmic surgical approach that can reduce potentially blinding elevated hydrostatic intracranial pressure on the optic disc via an incision on the optic nerve. The prototype is a multi-arm system capable of dexterous manipulation and visualization of the optic nerve area, allowing for a minimally invasive approach. Each arm is an independently controlled concentric tube robot collimated by a bespoke guide that is secured on the eye sclera via sutures. In this paper, we consider the robot's end-effector design in order to reach/navigate the optic nerve according to the clinical requirements of ONSF. A prototype of the robot was engineered, and its ability to penetrate the optic nerve was analysed by conducting ex vivo experiments on porcine optic nerves and comparing their stiffness to human ones. The robot was successfully deployed in a custom-made realistic eye phantom. Our simulation studies and experimental results demonstrate that the robot can successfully navigate to the operation site and carry out the intervention.
S.M.Hadi Sadati
added a research item
In this paper, we propose benefiting from load readings at the base of a continuum appendage for real-time forward integration of Cosserat rod model with application in configuration and tip load estimation. The application of this method is successfully tested for stiffness imaging of a soft tissue, using a 3-DOF hydraulically actuated braided continuum appendage. Multiple probing runs with different actuation pressures are used for mapping the tissue surface shape and directional linear stiffness, as well as detecting non-homogeneous regions, e.g. a hard nodule embedded in a soft silicon tissue phantom. Readings from a 6-axis force sensor at the tip is used for comparison and verification. As a result, the tip force is estimated with 0.016-0.037 N (7-20%) mean error in the probing and 0.02-0.1 N (6-12%) in the indentation direction, 0.17 mm (14%) mean error is achieved in estimating the surface profile, and 3.415 [N/m] (10-16%) mean error is observed in evaluating tissue directional stiffness, depending on the appendage actuation. We observed that if the appendage bends against the slider motion (toward the probing direction), it provides better horizontal stiffness estimation and better estimation in the perpendicular direction is achieved when it bends toward the slider motion (against the probing direction). In comparison with a rigid probe, ≈ 10 times smaller stiffness and ≈ 7 times larger mean standard deviation values were observed, suggesting the importance of a probe stiffness in estimation the tissue stiffness.
S.M.Hadi Sadati
added a research item
A reliable, accurate, and yet simple dynamic model is important to analyze, design and control hybrid rigid-continuum robots. Such models should be fast, as simple as possible and user-friendly to be widely accepted by the ever-growing robotics research community. In this study, we introduce two new modeling methods for continuum manipulators: a general reduced-order model (ROM) and a discretized model with absolute states and Euler-Bernoulli beam segments (EBA). Additionally, a new formulation is presented for a recently introduced discretized model based on Euler- Bernoulli beam segments and relative states (EBR). We implement these models to a Matlab software package, named T M T Dyn, to develop a modeling tool for hybrid rigid-continuum systems. The package features a new High-Level Language (HLL) text-based interface, a CAD-file import module, automatic formation of the system Equation of Motion (EOM) for different modeling and control tasks, implementing Matlab C-mex functionality for improved performance, and modules for static and linear modal analysis of a hybrid system. The underlying theory and software package are validated for modeling experimental results for (i) dynamics of a continuum appendage, and (ii) general deformation of a fabric sleeve worn by a rigid link pendulum. A comparison shows higher simulation accuracy (8-14% normalized error) and numerical robustness of the ROM model for a system with small number of states, and computational efficiency of the EBA model with near real-time performances that makes it suitable for large systems. The challenges and necessary modules to further automate the design and analysis of hybrid systems with a large number of states are briefly discussed in the end.
S.M.Hadi Sadati
added a research item
Hybrid rigid-continuum robot design addresses a range of challenges associated with using soft robots in application areas such as robotic surgery. Design of such robots poses challenges beyond standard rigid-body robots. A fast, reliable, accurate yet simple dynamic model is important to support the design, analysis, and control of hybrid rigid-continuum robots. In our previous work, we developed a modeling package for hybrid rigid-continuum systems, named TMTDyn. In this paper, we focus on how we developed an internal domain-specific language (DSL) using Matlab's OO capabilities and the concept of fluent interfaces to improve validation, understandability, and maintainability of the models constructed using TMTDyn. We present the language implementation, and discuss some of the benefits and challenges of building a Matlab-internal DSL.
S.M.Hadi Sadati
added 4 research items
Various methods based on hyperelastic assumptions have been developed to address the mathematical complexities of modeling motion and deformation of continuum manipulators. In this study, we propose a quasistatic approach for 3D modeling and real-time simulation of a pneumatically actuated soft continuum robotic appendage to estimate the contact force and overall pose. Our model can incorporate external load at any arbitrary point on the body and deliver positional and force propagation information along the entire backbone. In line with the proposed model, the effectiveness of elasticity versus hyperelasticity assumptions (neo-Hookean and Gent) is investigated and compared. Experiments are carried out with and without external load, and simulations are validated across a range of Young's moduli.
S.M.Hadi Sadati
added a research item
A reliable, accurate, and yet simple dynamic model is important to analyze, design and control continuum manip-ulators. Such models should be fast, as simple as possible and user-friendly to be widely accepted by the ever-growing robotics research community. In this study, we introduce two new mod-eling methods for continuum manipulators: a general reduced-order model (ROM) and a discretized model with absolute states and Euler-Bernoulli beam segments (EBA). Additionally, a new formulation is presented for a recently introduced discretized model based on Euler-Bernoulli beam segments and relative states (EBR). The models are validated in comparison to experimental results for dynamics of a STIFF-FLOP continuum appendage. Our comparison shows higher simulation accuracy (8-14% normalized error) and numerical robustness of the ROM model, and computational efficiency of the EBA model with near real-time performances that makes it suitable for large systems. The challenges with designing control and observation scenarios are briefly discussed in the end.
Ali Shiva
added a research item
Various methods based on hyperelastic assumptions have been developed to address the mathematical complexities of modeling motion and deformation of continuum manipulators. In this study, we propose a quasistatic approach for 3D modeling and real-time simulation of a pneumatically actuated soft continuum robotic appendage to estimate the contact force and overall pose. Our model can incorporate external load at any arbitrary point on the body and deliver positional and force propagation information along the entire backbone. In line with the proposed model, the effectiveness of elasticity versus hyperelasticity assumptions (neo-Hookean and Gent) is investigated and compared. Experiments are carried out with and without external load, and simulations are validated across a range of Young's moduli. Results show best conformity with Hooke's model for limited strains with about 6% average normalized error of position; and a mean absolute error of less than 0.08 N for force applied at the tip and on the body, demonstrating high accuracy in estimating the position and the contact force.
S.M.Hadi Sadati
added 2 research items
This thesis investigates how the problem of stiffness regulation of continuum manipulators can be simplified by inspiration from morphology of biological fish scales and experimental observation of manipulator geometry deformation. Soft continuum “trunk and tentacle” manipulators have high inherent dexterity and reconfigurability and have become an attractive candidate for safe manipulation and explorations in surgical and space robotic applications recently. The passive shape adaptation and large reachable configuration space features of this class of manipulators, due to their highly deformable nature, make them a perfect choice for minimally invasive insertion of surgical tools in the confined maze-like space in many robotic surgery sites. However, achieving accuracy in precise tasks is a challenge with these highly flexible structures, for which stiffness variable designs based on jamming, smart material, antagonistic actuation and morphing structures are introduced in the recent years. After a careful review and comparative study of current methods on modeling and stiffness modulation of continuum manipulators, an analytical model is presented based on the geometry deformation of continuum manipulators and the Rivlin’s work on continuum media and adopted the Ritz and Galerkin methods to solve the dynamics of continuum manipulators based on Cosserat beam theory and principle of virtual work. Our new approach reduces model and control space dimension while preserving the accuracy. This enabled us to solve the stiffness regulation actuation and computation problems in the morphological level which highly simplifies the central control design. Two novel integrable helical interfaces inspired by the shape and special arrangement of fish scales morphology is designed using tendon driven and thermoactive low melting point actuation mechanisms. High stiffness range, very low hysteresis and easy integration to different manipulator designs are the advantages of our design compared to the previous research. An analytical model is derived based on which the performance of the design is optimized. A comparison between the presented robotic interface designs and a real fish skin suggests that natural scales may contribute in stiffness modulation of the fish body through jamming, e.g. due to external stream and steady water pressure. Finally, a novel decentralized morphological approach is implemented to regulate the regional stiffness of the continuum manipulator integrated with the designed jamming interfaces to reject configuration disturbances and modulate the task space stiffness with possible application in soft tissue palpation.
Having a reliable accurate and at the same time simple dynamic model is important in analysis, design, path planning and control of robotic systems. Such models should be fast, convenient and simple to use to be accepted by the ever growing robotics research community. Among all the challenges, controlling complex systems with compound rigid and continuum body mechanisms with switching dynamical behavior, due to interaction with their environment in different applications, has attracted much research recently. To address these concerns, we have upgraded the AutoTMTDyn Matlab software package, a recently introduced tool for deriving La-grange Equations of Motion (EOM) in a vector formalism, with the ability to handle series continuum-link mechanisms, e.g. continuum manipulators, and introducing an easy to use high level language (HLL) as a new text-based user interface. The variable curvature kinematics and TMT Lagrange dynamics of a continuum beam is derived in differential and discrete forms. The HLL elements are described and showcased in modeling and analysis of three bioinspired dynamical systems; lumped-system model of a spider web, continuum model for a rat whisker, and modeling a continuum pneumatic module. The challenges with using the package for systems with large modeling states, and the necessary modules to further automate the analysis of the dynamic systems are briefly discussed.
S.M.Hadi Sadati
added a research item
We present a 3D-printable thermoactive scale jamming interface as a new way to control a continuum manipulator dexterity by taking inspiration from the helical arrangement of fish scales. A highly articulated helical interface is 3D-printed with thermoactive functionally graded joints using a conventional 3D printing device that utilizes UV curable acrylic plastic and hydroxylated wax as the primary and supporting material. The joint compliance is controlled by regulating wax temperature in phase transition. Empirical feed-forward control relations are identified through comprehensive study of the wax melting profile and actuation scenarios for different shaft designs to achieve desirable repeatability and response time. A decentralized control approach is employed by relating the mathematical terms of the Cosserat beam method to their morphological counterparts in which the manipulator local anisotropic stiffness is controlled based on the local stress and strain information. As a result, a minimalistic central controller is designed in which the joints' thermo-mechanical states are observed using a morphological observer, an external fully monitored replica of the observed system with the same inputs. Preliminary results for passive shape adaptation, geometrical disturbance rejection and task space anisotropic stiffness control are reported by integrating the interface on a continuum manipulator.
S.M.Hadi Sadati
added a research item
We present a 3D-printable thermoactive scale jamming interface as a new way to control a continuum manipulator dexterity by taking inspiration from the helical arrangement of fish scales. A highly articulated helical interface is 3D-printed with thermoactive functionally graded joints using a conventional 3D printing device that utilizes UV curable acrylic plastic and hydroxylated wax as the primary and supporting material. The joint compliance is controlled by regulating wax temperature in phase transition. Empirical feed-forward control relations are identified through comprehensive study of the wax melting profile and actuation scenarios for different shaft designs to achieve desirable repeatability and response time. A decentralized control approach is employed by relating the mathematical terms of the Cosserat beam method to their morphological counterparts in which the manipulator local anisotropic stiffness is controlled based on the local stress and strain information. As a result, a minimalistic central controller is designed in which the joints' thermo-mechanical states are observed using a morphological observer, an external fully monitored replica of the observed system with the same inputs. Preliminary results for passive shape adaptation, geometrical disturbance rejection and task space anisotropic stiffness control are reported by integrating the interface on a continuum manipulator.
S.M.Hadi Sadati
added a research item
To address the challenges with real-time accurate modeling of multi-segment continuum manipulators in the presence of significant external and body loads, we introduce a novel series solution for variable-curvature Cosserat rod static and Lagrangian dynamic method. By combining a modified Lagrange polynomial series solution, based on experimental observations, with Ritz and Ritz-Galerkin methods, the infinite modeling state space of a continuum manipulator is minimized to geometrical position of a handful of physical points (in our case two). As a result, a unified easy to implement vector formalism is proposed for the nonlinear impedance and configuration control. We showed that by considering the mechanical effects of highly elastic axial deformation, the model accuracy is increased up to 6%. The proposed model predicts experimental results with 6-8% (4-6 [mm]) mean error for the Ritz-Galerkin method in static cases and 16-20% (12-14 [mm]) mean error for the Ritz method in dynamic cases, in planar and general 3D motions. Comparing to five different models in the literature, our approximate solution is shown to be more accurate with the smallest possible number of modeling states and suitable for real-time modeling, observation and control applications.
Ali Shiva
added a research item
Investigations on control and optimization of continuum manipulators have resulted in a number of kinematic and dynamic modeling approaches each having their own advantages and limitations in various applications. In this paper, a comparative study of five main methods in the literature for kinematic, static and dynamic modeling of continuum manipulators is presented in a unified mathematical framework. The five widely used methods of Lumped system dynamic model, Constant curvature, two-step modified constant curvature, variable curvature Cosserat rod and beam theory approach, and series solution identification are reviewed here with derivation details in order to clarify their methodological differences. A comparison between computer simulations and experimental results using a STIFF-FLOP continuum manipulator is presented to study the advantages of each modeling method.
S.M.Hadi Sadati
added a research item
Continuum manipulators have gained significant attention in the robotic community due to their high dexterity, deformability, and reachability. Modeling of such manipulators has been shown to be very complex and challenging. Despite many research attempts, a general and comprehensive modeling method is yet to be established. In this paper, for the first time, we introduce the bending effect in the model of a braided extensile pneumatic actuator with both stiff and bendable threads. Then, the effect of the manipulator cross-section deformation on the constant curvature and variable curvature models is investigated using simple analytical results from a novel geometry deformation method and is compared to experimental results. We achieve 38% mean reference error simulation accuracy using our constant curvature model for a braided continuum manipulator in presence of body load and 10% using our variable curvature model in presence of extensive external loads. With proper model assumptions and taking to account the cross-section deformation, a 7–13% increase in the simulation mean error accuracy is achieved compared to a fixed cross-section model. The presented models can be used for the exact modeling and design optimization of compound continuum manipulators by providing an analytical tool for the sensitivity analysis of the manipulator performance. Our main aim is the application in minimal invasive manipulation with limited workspaces and manipulators with regional tunable stiffness in their cross section.
S.M.Hadi Sadati
added a research item
Investigations on control and optimization of continuum manipulators have resulted in a number of kinematic and dynamic modeling approaches each having their own advantages and limitations in various applications. In this paper, a comparative study of five main methods in the literature for kinematic, static and dynamic modeling of continuum manipulators is presented in a unified mathematical framework. The five widely used methods of Lumped system dynamic model, Constant curvature, two-step modified constant curvature, variable curvature Cosserat rod and beam theory approach, and series solution identification are reviewed here with derivation details in order to clarify their methodological differences. A comparison between computer simulations and experimental results using a STIFF-FLOP continuum manipulator is presented to study the advantages of each modeling method.
Ali Shiva
added a research item
There is an emerging trend toward soft robotics due to its extended manipulation capabilities compared to traditionally rigid robot links, showing promise for an extended applicability to new areas. However, as a result of the inherent property of soft robotics being less rigid, the ability to control/obtain higher overall stiffness when required is yet to be further explored. In this letter, an innovative design is introduced which allows varying the stiffness of a continuum silicon-based manipulator and proves to have potential for applications in Minimally Invasive Surgery. Inspired by muscular structures occurring in animals such as the octopus, we propose a hybrid and inherently antagonistic actuation scheme. In particular, the octopus makes use of this principle activating two sets of muscles-longitudinal and transverse muscles-thus, being capable of controlling the stiffness of parts of its arm in an antagonistic fashion. Our designed manipulator is pneumatically actuated employing chambers embedded within the robot's silicone structure. Tendons incorporated in the structure complement the pneumatic actuation placed inside the manipulator's wall to allow variation of overall stiffness. Experiments are carried out by applying an external force in different configurations while changing the stiffness by means of the two actuation mechanisms. Our test results show that dual, antagonistic actuation increases the load bearing capabilities for soft continuum manipulators and thus their range of applications.
Yohan Noh
added an update
Experiment software development
 
Ali Shiva
added 3 project references
Ali Shiva
added a project goal
Modelling, path planning, control of stiffness controllable continuum manipulators