Design and Implementation of a Novel Variable Stiffness Actuator with Cam-Based Relocation Mechanism

2020 ◽  
pp. 1-22
Author(s):  
Yinghao Ning ◽  
Hailin Huang ◽  
Wenfu Xu ◽  
Weimin Zhang ◽  
Bing Li
Keyword(s):  
Variable Stiffness ◽  
Human Robot Interaction ◽  
Tracking Accuracy ◽  
Robot Interaction ◽  
Wide Range ◽  
Lever Mechanism ◽  
Point Control ◽  
Point To Point ◽  
Safe Performance ◽  
Variable Stiffness Actuators

Abstract Variable stiffness actuators (VSAs) are widely explored as they could improve the safe performance for human-robot interaction and make the system torque controllable based on the internal compliance. This paper presents a novel VSA based on the cam-based relocation mechanism (CRM-VSA), which is utilized to change the locations of pivot and spring of a lever mechanism simultaneously. Consequently, such structure makes the actuator compacted and the stiffness regulation designable which could help engineers to pursue different demands of stiffness regulation. The simultaneous relocations of the pivot and spring also permit a wide range of adjustable stiffness. By introducing linear guide pairs, the internal friction of the relocations of pivot and spring could be greatly reduced, thus enhancing the energy efficiency. To evaluate the performance of the proposed CRM-VSA, the point-to-point control strategy is developed which contributes to a higher tracking accuracy and oscillation attenuation at both the start and end points of the trajectory. Additionally, the performance of torque controllability is also verified through experiments. These excellent capabilities enable the proposed CRM-VSA to be qualified for constructing a robotic arm towards service applications.

scholarly journals Soft Robotics with Variable Stiffness Actuators: Tough Robots for Soft Human Robot Interaction

Soft Robotics ◽  
2015 ◽  
pp. 231-254 ◽  
Author(s):  
Sebastian Wolf ◽  
Thomas Bahls ◽  
Maxime Chalon ◽  
Werner Friedl ◽  
Markus Grebenstein ◽  
...  
Keyword(s):  
Variable Stiffness ◽  
Human Robot Interaction ◽  
Soft Robotics ◽  
Robot Interaction ◽  
Variable Stiffness Actuators

Design of a Variable Stiffness Actuator Based on Flexures

2011 ◽  
Vol 3 (3) ◽  
Author(s):  
Gianluca Palli ◽  
Giovanni Berselli ◽  
Claudio Melchiorri ◽  
Gabriele Vassura
Keyword(s):  
Compliant Mechanism ◽  
Variable Stiffness ◽  
Human Robot Interaction ◽  
Experimental Characterization ◽  
Robot Interaction ◽  
Trade Off ◽  
Variable Stiffness Actuator ◽  
Robotic Devices ◽  
Stiffness Profile ◽  
Variable Stiffness Actuators

Variable stiffness actuators can be used in order to achieve a suitable trade-off between performance and safety in robotic devices for physical human–robot interaction. With the aim of improving the compactness and the flexibility of existing mechanical solutions, a variable stiffness actuator based on the use of flexures is investigated. The proposed concept allows the implementation of a desired stiffness profile and range. In particular, this paper reports a procedure for the synthesis of a fully compliant mechanism used as a nonlinear transmission element, together with its experimental characterization. Finally, a preliminary prototype of the overall joint is depicted.

scholarly journals A Stiffness Variable Passive Compliance Device with Reconfigurable Elastic Inner Skeleton and Origami Shell

2020 ◽  
Vol 33 (1) ◽  
Author(s):  
Zhuang Zhang ◽  
Genliang Chen ◽  
Weicheng Fan ◽  
Wei Yan ◽  
Lingyu Kong ◽  
...  
Keyword(s):  
Variable Stiffness ◽  
Rehabilitation Robotics ◽  
Human Robot Interaction ◽  
Main Concept ◽  
Robot Interaction ◽  
Switching Speed ◽  
Leaf Springs ◽  
Stiffness Variation ◽  
Low Stiffness ◽  
Large Deflection Problem

Abstract Devices with variable stiffness are drawing more and more attention with the growing interests of human-robot interaction, wearable robotics, rehabilitation robotics, etc. In this paper, the authors report on the design, analysis and experiments of a stiffness variable passive compliant device whose structure is a combination of a reconfigurable elastic inner skeleton and an origami shell. The main concept of the reconfigurable skeleton is to have two elastic trapezoid four-bar linkages arranged in orthogonal. The stiffness variation generates from the passive deflection of the elastic limbs and is realized by actively switching the arrangement of the leaf springs and the passive joints in a fast, simple and straightforward manner. The kinetostatics and the compliance of the device are analyzed based on an efficient approach to the large deflection problem of the elastic links. A prototype is fabricated to conduct experiments for the assessment of the proposed concept. The results show that the prototype possesses relatively low stiffness under the compliant status and high stiffness under the stiff status with a status switching speed around 80 ms.

Determination of Variable Stiffness of a Human Elbow for Human-Robot Interaction

2014 ◽  
Author(s):  
Michael Boyarsky ◽  
Megan Heenan ◽  
Scott Beardsley ◽  
Philip Voglewede
Keyword(s):  
Experimental Data ◽  
Disturbance Rejection ◽  
Variable Stiffness ◽  
Important Variable ◽  
Human Motion ◽  
Human Robot Interaction ◽  
Robot Interaction ◽  
Constant Stiffness ◽  
Stiffness Model ◽  
Motor Model

This paper aims to emulate human motion with a robot for the purpose of improving human-robot interaction (HRI). In order to engineer a robot that demonstrates functionally similar motion to humans, aspects of human motion such as variable stiffness must be captured. This paper successfully determined the variable stiffness humans use in the context of a 1 DOF disturbance rejection task by optimizing a time-varying stiffness parameter to experimental data in the context of a neuro-motor Simulink model. The significant improved agreement between the model and the experimental data in the disturbance rejection task after the addition of variable stiffness demonstrates how important variable stiffness is to creating a model of human motion. To enable a robot to emulate this motion, a predictive stiffness model was developed that attempts to reproduce the stiffness that a human would use in a given situation. The predictive stiffness model successfully decreases the error between the neuro-motor model and the experimental data when compared to the neuro-motor model with a constant stiffness value.

Selection and implementation of optimal magnetorheological brake design for a variable impedance exoskeleton robot joint

2016 ◽  
Vol 231 (5) ◽  
pp. 941-960 ◽  
Author(s):  
Ozgur Baser ◽  
Mehmet Alper Demiray
Keyword(s):  
Volume Ratio ◽  
Variable Stiffness ◽  
Humanoid Robots ◽  
Performance Comparison ◽  
Analytical Models ◽  
Exoskeleton Robot ◽  
Wide Range ◽  
Braking Torque ◽  
Variable Damping ◽  
Variable Stiffness Actuators

Next-generation exoskeleton and humanoid robots are expected to behave similar to the human neuro-muscular system to perform stable, flexible, and biomimetic movements. To achieve this goal, the variable stiffness actuators have been widely used in various robots. Using variable damping actuators along with variable stiffness actuators will be extremely beneficial for wide range of stable movements. Magnetorheological (MR) brakes are one of the most promising electromagnetic structures that can provide such variable damping in a relatively small actuator volume. In this paper, we focused on the design, characterization, selection and implementation of T-shaped, inner coil and outer coil multi-pole MR brakes to the ankle of an exoskeleton robot. Analytical models are developed using the magnetic circuit analysis to determine the braking torque. Then, magnetic finite element models are developed and coupled with an optimization algorithm to determine the optimal set of parameters of each MR brake design. Prototypes are manufactured in same size and tested experimentally to characterize the actuators’ torque-to-volume ratio, transient response, hysteresis, torque tracking, energy consumption, and damping performances. The performance comparison of the brakes showed T-shaped multi-pole MR brake design has superior characteristics compared to two other designs. Therefore, T-shaped multi-pole MR brake design is coupled with a variable stiffness actuator and implemented in an ankle joint of an exoskeleton robot and experimentally tested. The results show that the developed new hybrid robot joint is capable of stable movement with a simple control algorithm by changing its stiffness and damping independently.

scholarly journals A Brief Review of Neural Networks Based Learning and Control and Their Applications for Robots

Complexity ◽  
2017 ◽  
Vol 2017 ◽  
pp. 1-14 ◽  
Author(s):  
Yiming Jiang ◽  
Chenguang Yang ◽  
Jing Na ◽  
Guang Li ◽  
Yanan Li ◽  
...  
Keyword(s):  
Neural Networks ◽  
Nonlinear Systems ◽  
Human Robot Interaction ◽  
Learning Tools ◽  
Robot Interaction ◽  
Practical Applications ◽  
Powerful Learning ◽  
Wide Range ◽  
Complex Nonlinear Systems ◽  
And Control

As an imitation of the biological nervous systems, neural networks (NNs), which have been characterized as powerful learning tools, are employed in a wide range of applications, such as control of complex nonlinear systems, optimization, system identification, and patterns recognition. This article aims to bring a brief review of the state-of-the-art NNs for the complex nonlinear systems by summarizing recent progress of NNs in both theory and practical applications. Specifically, this survey also reviews a number of NN based robot control algorithms, including NN based manipulator control, NN based human-robot interaction, and NN based cognitive control.

A Comparative Study on the Effect of Mechanical Compliance for a Safe Physical Human–Robot Interaction

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Yu She ◽  
Siyang Song ◽  
Hai-Jun Su ◽  
Junmin Wang
Keyword(s):  
Impact Force ◽  
Variable Stiffness ◽  
Human Robot Interaction ◽  
Design Parameters ◽  
Robot Dynamics ◽  
Robot Interaction ◽  
Promising Alternative ◽  
Mechanical Compliance ◽  
Maximum Impact Force ◽  
The Impact

Abstract In this paper, we study the effects of mechanical compliance on safety in physical human–robot interaction (pHRI). More specifically, we compare the effect of joint compliance and link compliance on the impact force assuming a contact occurred between a robot and a human head. We first establish pHRI system models that are composed of robot dynamics, an impact contact model, and head dynamics. These models are validated by Simscape simulation. By comparing impact results with a robotic arm made of a compliant link (CL) and compliant joint (CJ), we conclude that the CL design produces a smaller maximum impact force given the same lateral stiffness as well as other physical and geometric parameters. Furthermore, we compare the variable stiffness joint (VSJ) with the variable stiffness link (VSL) for various actuation parameters and design parameters. While decreasing stiffness of CJs cannot effectively reduce the maximum impact force, CL design is more effective in reducing impact force by varying the link stiffness. We conclude that the CL design potentially outperforms the CJ design in addressing safety in pHRI and can be used as a promising alternative solution to address the safety constraints in pHRI.

scholarly journals V2SOM: A Novel Safety Mechanism Dedicated to a Cobot’s Rotary Joints

Robotics ◽  
2019 ◽  
Vol 8 (1) ◽  
pp. 18 ◽  
Author(s):  
Younsse Ayoubi ◽  
Med Laribi ◽  
Said Zeghloul ◽  
Marc Arsicault
Keyword(s):  
Good Control ◽  
Variable Stiffness ◽  
Human Robot Interaction ◽  
Industrial Robots ◽  
Necessary Condition ◽  
Physical Interaction ◽  
Robot Interaction ◽  
Internal Damage ◽  
Low Stiffness ◽  
The Impact

Unlike “classical” industrial robots, collaborative robots, known as cobots, implement a compliant behavior. Cobots ensure a safe force control in a physical interaction scenario within unknown environments. In this paper, we propose to make serial robots intrinsically compliant to guarantee safe physical human–robot interaction (pHRI), via our novel designed device called V2SOM, which stands for Variable Stiffness Safety-Oriented Mechanism. As its name indicates, V2SOM aims at making physical human–robot interaction safe, thanks to its two basic functioning modes—high stiffness mode and low stiffness mode. The first mode is employed for normal operational routines. In contrast, the low stiffness mode is suitable for the safe absorption of any potential blunt shock with a human. The transition between the two modes is continuous to maintain a good control of the V2SOM-based cobot in the case of a fast collision. V2SOM presents a high inertia decoupling capacity which is a necessary condition for safe pHRI without compromising the robot’s dynamic performances. Two safety criteria of pHRI were considered for performance evaluations, namely, the impact force (ImpF) criterion and the head injury criterion (HIC) for, respectively, the external and internal damage evaluation during blunt shocks.

Variable Stiffness Mechanism for Tremor Suppression in Human-Robot Interaction

2018 ◽  
Author(s):  
Sri Sadhan Jujjavarapu ◽  
M. Amin Karami ◽  
Ehsan T. Esfahani
Keyword(s):  
Permanent Magnets ◽  
Involuntary Movement ◽  
Cutoff Frequency ◽  
Variable Stiffness ◽  
Rehabilitation Robotics ◽  
Human Robot Interaction ◽  
Limb Stiffness ◽  
Wide Range ◽  
Nonlinear Force ◽  
Human Limb

Variable stiffness mechanisms have a wide range of applications in the field of human-robot interactions such as rehabilitation robotics, prosthesis and industrial robotics due to their ability to comply with the human limb stiffness in an unstructured environment. This paper presents the analysis of a single degree of freedom variable stiffness actuator based on nonlinear force interactions between permanent magnets and its effect on the natural frequency of the system. In the proposed mechanism, variable stiffness is achieved by modifying the separation between magnets. The main goal here is to achieve a desired cutoff frequency by varying the stiffness of the system to filter out the involuntary movement of upper limb during physical human-robot interactions. Moreover, due to the spring-like non-contact force interactions between magnets, this mechanism can prevent the exchange of high impact forces between the robot and human.

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