Design Methodology for the Development of Variable Stiffness Devices based on Layer Jamming Transition

Purpose The purpose of this paper is to present a method which enables a robot to learn both motion skills and stiffness profiles from humans through kinesthetic human-robot cooperation. Design Methodology Approach Admittance control is applied to allow robot-compliant behaviors when following the reference trajectories. By extending the dynamical movement primitives (DMP) model, a new concept of DMP and stiffness primitives is introduced to encode a kinesthetic demonstration as a combination of trajectories and stiffness profiles, which are subsequently transferred to the robot. Electromyographic signals are extracted from a human’s upper limbs to obtain target stiffness profiles. By monitoring vibrations of the end-effector velocities, a stability observer is developed. The virtual damping coefficient of admittance controller is adjusted accordingly to eliminate the vibrations. Findings The performance of the proposed methods is evaluated experimentally. The result shows that the robot can perform tasks in a variable stiffness mode as like the human dose in the teaching phase. Originality Value DMP has been widely used as a teaching by demonstration method to represent movements of humans and robots. The proposed method extends the DMP framework to allow a robot to learn not only motion skills but also stiffness profiles. Additionally, the authors proposed a stability observer to eliminate vibrations when the robot is disturbed by environment.

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A new variable stiffness robot joint

Industrial Robot the international journal of robotics research and application ◽

10.1108/ir-11-2014-0422 ◽

2015 ◽

Vol 42 (4) ◽

pp. 371-378 ◽

Cited By ~ 13

Author(s):

Yong Tao ◽

Tianmiao Wang ◽

Yunqing Wang ◽

Long Guo ◽

Hegen Xiong ◽

...

Keyword(s):

Design Methodology ◽

Dynamic Stiffness ◽

Variable Stiffness ◽

System Behavior ◽

Pivot Point ◽

Content Type ◽

Wide Range ◽

Variable Stiffness Actuators ◽

Stiffness Adjustment ◽

Elastic Elements

Purpose – This study aims to propose a new variable stiffness robot joint (VSR-joint) for operating safely. More and more variable stiffness actuators are being designed and implemented because of their ability to minimize large forces due to shocks, to safely interact with the user and their ability to store and release energy in passive elastic elements. Design/methodology/approach – The design of VSR-joint is compact and integrated highly and the operating is simply. The mechanics, the principle of operation and the model of the VSR-joint are proposed. The principle of operation of VSR-joint is based on a lever arm mechanism with a continuously regulated pivot point. The VSR-joint features a highly dynamic stiffness adjustment along with a mechanically programmable system behavior. This allows an easy adaption to a big variety of tasks. Findings – Preliminary results are presented to demonstrate the fast stiffness regulation response and the wide range of stiffness achieved by the proposed VSR-joint design. Originality/value – In this paper, a new variable stiffness joint is proposed through changing the cantilever arm to change the performance of the elastic element, which is compact, small size and simple adjustment.

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Development of a Gripper with Variable Stiffness for a CT-Guided Needle Insertion Robot

Journal of Robotics and Mechatronics ◽

10.20965/jrm.2020.p0692 ◽

2020 ◽

Vol 32 (3) ◽

pp. 692-700

Author(s):

Kento Yokouchi ◽

Tetsushi Kamegawa ◽

Takayuki Matsuno ◽

Takao Hiraki ◽

Takuya Yamaguchi ◽

...

Keyword(s):

Computed Tomography ◽

Interventional Radiology ◽

Interventional Procedures ◽

Variable Stiffness ◽

Needle Insertion ◽

Medical Procedure ◽

Needle Holder ◽

Ct Guided ◽

Jamming Transition ◽

Ct Radiation

In recent years, interventional radiology (IR) as a medical procedure has attracted considerable attention. Among the various IR techniques, computed tomography (CT)-guided IR is performed by inserting a specific needle into a lesion under CT guidance, leading to this medical procedure being less invasive. However, as the procedure requires the doctor to be positioned near the CT, radiation exposure may be a major concern. To overcome this problem, we developed a remote-controlled robotic system for needle insertion during CT-guided interventional procedures. The current needle holder for the robot is risky in that it might hurt a patient since a needle is always held firmly even when the patient moves. To solve this problem, we designed and fabricated a gripper with variable stiffness through jamming transition. Subsequently, we conducted experiments to investigate the effect of elements constituting the gripper to improve its performance.

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Design methodology of a novel variable stiffness actuator based on antagonistic-driven mechanism

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/0954406219869968 ◽

2019 ◽

Vol 233 (19-20) ◽

pp. 6967-6984

Author(s):

Yinghao Ning ◽

Wenfu Xu ◽

Hailin Huang ◽

Bing Li ◽

Fei Liu

Keyword(s):

Sensitivity Analysis ◽

Design Methodology ◽

Design Method ◽

Structural Parameters ◽

Variable Stiffness ◽

Compact Structure ◽

Constant Stiffness ◽

Return Journey ◽

Variable Stiffness Actuator ◽

Spring Mechanism

This paper concerns the construction of a novel variable stiffness actuator with antagonistic-driven mechanism (ADM-VSA). The ADM-VSA consists of two cam mechanisms and two constant stiffness spring mechanisms establishing the antagonistic structure to eliminate the empty return journey. The former with symmetrical cam profiles are designed for the movement of actuator, while the latter are explored substituting traditional springs of generating compliance for compact structure. To obtain desired performance of the actuator, the design methodology is developed for constructing the ADM-VSA, integrating the constant stiffness spring mechanism design method from four-bar mechanism to multi-bar mechanism, the comprehensive optimization of cam profiles and sensitivity analysis of structural parameters. The comprehensive optimization is conducted with different-order Bezier splines considering the torque, stiffness, and energy by friction simultaneously. The sensitivity analysis is performed to investigate the influence of structural errors on the performance of actuator, with new indexes decreasing the workload of calculation, and several guidelines for the design and manufacturing are achieved. Finally, a prototype is developed to verify the reliability of ADM-VSA and, further, proves the validity of proposed design methods.

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ARES, a variable stiffness actuator with embedded force sensor for the ATLAS exoskeleton

Industrial Robot the international journal of robotics research and application ◽

10.1108/ir-06-2014-0350 ◽

2014 ◽

Vol 41 (6) ◽

pp. 518-526 ◽

Cited By ~ 19

Author(s):

M. Cestari ◽

D. Sanz-Merodio ◽

J.C. Arevalo ◽

E. Garcia

Keyword(s):

Design Methodology ◽

Variable Stiffness ◽

Force Sensor ◽

Content Type ◽

Torque Measurements ◽

Variable Stiffness Actuator ◽

Compact Design ◽

Intrinsic Dynamic

Purpose – The purpose of this study is to present a variable stiffness actuator, one of whose main features is that the compliant elements simultaneously allow measuring of the torque exerted by the joint. Conceived as a force-controlled actuator, this actuator with Adjustable Rigidity and Embedded Sensor (ARES) is intended to be implemented in the knee of the ATLAS exoskeleton for children to allow the exploitation of the intrinsic dynamic during the locomotion cycle. Design/methodology/approach – A set of simulations were performed to evaluate the behavior of the actuator mechanism and a prototype of the variable impedance actuator was incorporated into the exoskeleton’s knee and evaluations of the torque measurements capabilities along with the rigidity adjustments were made. Findings – Mass and inertia of the actuator are minimized by the compact design and the utilization of the different component for more than one utility. By a proper match of the compliance of the joint and the performed task, good torque measurements can be achieved and no bandwidth saturation is expected. Originality/value – In the actuator, the compliant elements simultaneously allow measuring of the torque exerted by the join. By a proper match of the compliance of the joint and the performed task, good torque measurements can be achieved and no bandwidth saturation is expected.

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