Design, Dynamics Analysis, and Real-Time Stiffness Control of a Variable Stiffness Joint

Abstract

This paper proposes a variable stiffness joint based on a symmetrical crank slider mechanism (SCM-VSJ). Firstly, the mechanical design and the working principle of the variable stiffness joint is described, and its stiffness regulation characteristics are studied. Secondly, the dynamical model of variable stiffness joint including joint motor, harmonic reducer and stiffness adjustment motor is established, in addition, the transmission mechanism of the crank slider mechanism and the elastic deformation of the spring bar are considered in the dynamic modeling. Finally, in order to control the dynamic stiffness of the variable stiffness joint in real time, a kind of improved PID (proportional-integral-derivative) control algorithm based on feed-forward and feedback closed-loop is proposed on the basis of the existing dynamical model, and the simulation analysis of real-time tracking control of dynamic stiffness for sinusoidal wave expected stiffness signal and random expected stiffness signal is carried out respectively. The research shows that the real-time stiffness control of SCM-VSJ can be realized effectively, and during the stiffness adjustment process, the output torque of the stiffness adjustment motor will be affected by the elastic deformation of the spring bar.

Design and analysis of a novel variable stiffness joints with robots

“…The VSJ using leaf springs was proposed by Yang et al The effective length of the spring can be changed by a crank-slider mechanism to achieve a wide range of stiffness variatio. 13 Wu et al 14 combined cams and leaf springs to realize a VSJ that can be combined with one or more leaf springs, and the stiffness range of the joint is determined by the number of springs used.…”

Modeling and Analysis of the Stiffness Distribution of Host–Parasite Robots

“…He et al [17] proposed a new general stiffness model, which includes linear and nonlinear stiffness models, for serial mechanisms. Yu et al [18] calculated and analyzed the dynamic stiffness of a symmetrical crank slider mechanism with a variable-stiffness joint. Lu et al [19] suggested a new method for calculating the stiffness of bolted connectors and analyzed the effects of joint surface stiffness on the overall stiffness.…”