An Extension of Computed-Torque Control for Parallel Robots in Ankle Reeducation

This paper extends the well-known computed-torque control technique for trajectory tracking in parallel robotic manipulators, which belong to the class of nonlinear systems under algebraic restrictions. The proposed methodology is based on Euler-Lagrange modelling which, once the closed-loop kinematic chain is taken into account, leads to a system of differential algebraic equations requiring proper initialisation while controlled. The control scheme is illustrated for an ankle therapy device known as the motoBOTTE, where post-stroke patients are subject to reeducation routines corresponding to different trajectories of the parallel manipulator.