Novel torsional spring with corrugated flexible units for series elastic actuators for cooperative robots

Reasonable robot joint stiffness is necessary to guarantee the safety and control accuracy of cooperative robots. In this study, a novel flat torsional spring with corrugated flexible units for a series elastic actuator (SEA) was developed to meet the requirements of cooperative robots. The torsional spring can absorb impact energy. The spring was optimized through the design of experiment method, and its theoretical stiffness was verified through numerical calculation and finite element analysis. Compared with other existing flat torsional springs in the simulation, the proposed torsional spring showed reasonable torsional stiffness and high radial and axial stiffness, which could guarantee safety and control accuracy. The proposed torsional spring was also evaluated through real experiments. Simulation and experimental results revealed that the proposed torsional spring has a linear torque versus angle characteristic.