Quadrature current disturbance compensation for improved exoskeleton torque control

Active exoskeletons for elderly have very high demands on their actuators’ performances to not injure or irritate their wearer. One crucial aspect is the angle dependent torque of synchronous motors. Especially for a torque-controlled motor, ripples in the torque can lead to an actuator’s behavior that feels uncomfortable for the wearer. In this paper we present a new approach for online torque ripple compensation with the use of a disturbance observer. The disturbance compensation is based on a harmonic current injection and tested in a scenario with constant load and shows a significant reduction in torque ripple.