Dynamic Modeling and Control of Antagonistic Variable Stiffness Joint Actuator

Ming Zhang,Pengfei Ma,Junjie Jin,Xingwei Sun,Lijin Fang,Fangchao Xu,Feng Sun

doi:10.3390/act10060116

Ming Zhang, Pengfei Ma + Show 5 more

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https://doi.org/10.3390/act10060116

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Abstract

This study aims to develop a novel decoupling method for the independent control of the position and stiffness of a variable stiffness joint actuator (VSJA), which has been proven to be able to vary its stiffness in a larger range than other variable stiffness actuators. Using static analysis and the Jacobian matrix, we obtained the model of the stiffness of the robot joint actuator and dynamics. Based on the hybrid dynamic model of position and stiffness, it is possible to compensate for the torque of the variable stiffness joint actuator (VSJA) to enhance position control. Finally, after describing the actuator prototype, the established compliance control method is verified using simulation and experimental analysis.

Highlights

Dynamic Modeling and Control of Variable stiffness robot joints (VSJs) are a class of joints that differ from traditional rigid robot joints in the sense that they are flexible and can adjust their flexibility
Aiming at the stability and safety of the interaction between users and robots, this study proposed a decoupling control method for the position and stiffness for the wiredriven variable stiffness robot joint actuator, realizing compliance control and position control
The nonlinear equations composed of the mechanical model of the variable stiffness mechanism and the joint stiffness model were solved using the optimization method to realize a nonlinear decoupling of stiffness and position

Summary

Introduction

Dynamic Modeling and Control of Variable stiffness robot joints (VSJs) are a class of joints that differ from traditional rigid robot joints in the sense that they are flexible and can adjust their flexibility. Owing to their adjustable stiffness, they can ensure stable contact and safe operation. Such separation can significantly reduce the mass and inertia of the output link It is well-known from the literature [11,12] that the variable stiffness capability of antagonistic structures is directly related to the output torque of the drive units. We use a novel permanent magnet mechanism, already presented in [8], which increases the variable stiffness range without increasing the driving torque requirements

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