Design and analysis of spring parallel variable stiffness actuator based on antagonistic principle

Abstract Human-machine collaboration is an inevitable development trend of robots, and the variable stiffness joints of robots has been increasingly investigated by researchers. The variable stiffness joint based on the antagonism principle has received extensive attention, where its variable stiffness actuator mainly including nonlinear elastic components and antagonistic force pairs are the research hotspots. In this paper, a spring parallel variable stiffness actuator (SPVSA) based on a novel variable stiffness principle is proposed, in which the linear spring is arranged in parallel with the antagonistic force, so that the elastic components are no longer involved in the antagonism. The variable stiffness actuator effectively eliminates the antagonistic effect of the elastic components and improves the shock absorption and energy storage capacity. And based on the passive and active stiffness adjustment modes, the variable stiffness speed can be effectively improved. Meanwhile, the use of extremely ultralight springs and wire ropes simplifies the structure of the actuator and reduces the quality and size of the joints. In this paper the model design, related theoretical analysis and simulation analysis of SPVSA are carried out. And the effectiveness and advancement of SPVSA are verified by experiments.