Upper-Limb Force Estimation in Rehabilitation Robotics via Sliding Mode Based Observers

In this paper, an estimation scheme based on Adaptive Integral Sliding Mode Unknown Input Observers (AISM-UIOs) is proposed to provide an estimate of the cartesian force applied by the patients on the robot end-effector during rehabilitation exercises. In particular, the robot joints are decoupled leveraging the inverse dynamics control, and the acceleration perturbation caused by the external force is estimated using the observers. Such an estimate is then employed to reconstruct the original force applied by the patient. The proposal is analyzed from the theoretical point of view and assessed both in simulation and experimentally on a Franka Emika Panda robot manipulator.