Modelling and control of a device for rehabilitation of paraplegic patients

This paper reports results about modelling and control of an experimental device, developed at the Fondazione Don Carlo Gnocchi Onlus, used in the rehabilitation of paraplegics patients. The device is like a seesaw: the patient sit at one edge and a counterweight is placed at the other edge. The patient is seated so that its posture can be fully known in real-time by continuously monitoring the knee joint angle. By means of functional electrical stimulation (FES) of the quadriceps muscle groups, muscle contraction can be induced and the patient can stand up and sit down. To this aim a feedback control law is needed, which decides in real-time the stimulation to be delivered to the muscles on the basis of the measured knee angle value. In this work, a complete biomechanical model of the patient-seesaw system is presented and a simulator of the system is developed in the Dymola/Modelica environment and experimentally tuned. Also, a control law is designed and tested during typical rehabilitation exercises.