High power series elastic actuator development for torque-controlled exoskeletons

This paper presents the development procedures of a high power series elastic actuator that can be used in torque-controlled exoskeleton applications as a high-fidelity torque source. In order to provide a high torque output while containing its weight, the main objective was to satisfy dimensional and weight requirements within a compact structure. A three-fold design approach was implemented: (i) The torsional spring was designed using finite element analyses and its stiffness profile was experimentally tested via a torsional test machine, (ii) thermal behavior of the actuator was experimentally examined to ensure sufficient heat dissipation, (iii) the fatigue life of the spring was computed to be 9.5 years. Having manufactured the actuator, preliminary torque-control experiments were conducted. As the result, a high-fidelity torque control was achieved with a control bandwidth of up to 12 Hz.