Closed-loop control of FES supported standing up and sitting down using virtual reference feedback tuning

This work is focused on the design of closed-loop controllers for FES-supported standing up and sitting down. This task is a difficult one, due to the lack of stability of the considered system and to its nonlinear dynamic behaviour. In this paper, a control strategy based on two nested control loops is presented. The inner loop is based on a linear PID controller that stabilizes the system. The outer loop is designed using the Virtual Reference Feedback Tuning (VRFT) strategy, that allows a fast and easy tuning of the controller starting from a single I/O data set. Both linear and nonlinear control laws are implemented exploiting the VRFT algorithms. Simulation results show that the proposed technique is effective in controlling a paraplegic patient in FES-based standing up and sitting down.