Design methodology of a novel variable stiffness actuator based on antagonistic-driven mechanism

This paper concerns the construction of a novel variable stiffness actuator with antagonistic-driven mechanism (ADM-VSA). The ADM-VSA consists of two cam mechanisms and two constant stiffness spring mechanisms establishing the antagonistic structure to eliminate the empty return journey. The former with symmetrical cam profiles are designed for the movement of actuator, while the latter are explored substituting traditional springs of generating compliance for compact structure. To obtain desired performance of the actuator, the design methodology is developed for constructing the ADM-VSA, integrating the constant stiffness spring mechanism design method from four-bar mechanism to multi-bar mechanism, the comprehensive optimization of cam profiles and sensitivity analysis of structural parameters. The comprehensive optimization is conducted with different-order Bezier splines considering the torque, stiffness, and energy by friction simultaneously. The sensitivity analysis is performed to investigate the influence of structural errors on the performance of actuator, with new indexes decreasing the workload of calculation, and several guidelines for the design and manufacturing are achieved. Finally, a prototype is developed to verify the reliability of ADM-VSA and, further, proves the validity of proposed design methods.