Control strategy of slack enabling tendon actuator for the soft wearable robot using feedback linearization

Tendon driven mechanism has been widely used in mechanical systems because of its versatility to mechanical systems requiring complex transmission. This paper proposes a control strategy of slack enabling tendon actuator using feedback linearization. The slack enabling actuator is a newly developed tendon actuator that does not fail although the tendon slacks (non-positive tension) at the outlet of the actuator which is an essential operating phase when the tendon driven is applied to the soft wearable robots. To deal with the dynamic nonlinearities of the slack enabling actuator, input-output feedback linearization was adopted and linear disturbance observer was used to estimate the output tension of the wire and reject position following error due to the external load. The results show that the estimated tension coincide with the measured tension and a proposed method have proper characteristics to control the position of the tendon while estimating the tension of the output tendon.