Preliminary Evaluation of Disturbance Torque Estimation Approaches for Lower-limb Robotic Rehabilitation

In robotic rehabilitation, knowledge of human joint torques is very important to provide reliable data for clinical assessment and to provide feedback information about the user in order to design safe robotic control strategies. Nevertheless, their measurement can be complex and requires a high-cost implementation. Estimation approaches based on disturbance observers have been well studied for human joint torque estimation in robotic rehabilitation systems, most of them, for upper-limb devices. This paper represents our initial effort toward applying disturbance observer techniques for estimation of patient torque for lower-limb robotic rehabilitation. Three disturbance observer approaches for torque estimation are evaluated on a test scenario consisting of a robotic wearable device for ankle rehabilitation attached to a physical mock-up that replicates the ankle movement in the sagittal plane. The results obtained demonstrate the feasibility of the proposed methods and encourage us to test them with voluntary users.