Modeling and analysis of hysteresis using the Maxwell-slip model for variable stiffness actuators

Abstract

Hysteresis non-linearity in variable stiffness actuators (VSAs) causes significant torque errors and reduces the stability of the actuators, leading to poor human–computer interaction performance. At present, fewer hysteresis compensation models have been developed for compliant drives, so it is necessary to establish a suitable hysteresis model for compliant actuators. In this work, a new model with a combination of the Maxwell-slip model and virtual deformation is proposed and applied to an elbow compliant actuator. The method divides the periodic variation of the actuator into three parts: an ascending phase, a descending phase, and a transition phase. Based on the concept of virtual deformation, the nonlinear hysteresis curve is transformed into a polyline, and the output torque is estimated using the revised Maxwell-slip model. The simulation results are compared with the experimental data. Its torque error is controlled within 0.2Nm, which validates the model. An inverse model is finally established to calculate the deformation deflection angle for hysteresis compensation. The results show that the inverse model has high accuracy, and the deformation deflection is less than 0.15 rad.

Keywords

• Nonlinear compliant actuators
• Elastomer
• Maxwell-slip model
• Hysteresis modeling