Controle de Impedância e Admitância Unidimensional

Abstract

Neurorehabilitation is a form of therapy whereby the motor function impaired patient, due to conditions such as stroke, can recover part of the original motor skills. Some of the procedures involved in the rehabilitation process are based on repetitive activities, aiming to simulate an actual functional task. That is the case for gait rehabilitation, where activities simulating walking are usually employed. According to patient impairment level, more or less assistance is required, which is usually provided by therapists directly applying forces on the patient. The usage of robotic devices is thus of great value, since a great degree of repeatability, effort and flexibility is required in order to interact and to adapt to patient conditions. In the rehabilitation robotics field, interaction control (also termed impedance/admittance control), is a control method especially appealing. Instead of independently controlling variables such as position and force, interaction control enables the control of the interaction dynamics of both force and position. It is thus, possible to control the way and the amplitude of rehabilitation patient assistance. In this work, one dimensional impedance and admittance controllers are developed, to be used in rehabilitation robotic devices. The controllers are modelled, and its functionalities evaluated by the way of computer simulations. Test set-ups are built and experiments are carried out in order to evaluate the control method applicability. It is verified the extent to which impedance control is sensible to the mechanism inherent impedance, which requires the careful consideration with respect to low mechanical impedance robot design. On the other hand, the applicability of admittance control on robots with higher mechanical impedance is an appealing aspect. However, more complexity is associated with admittance control, considering the necessity of using load cells in order to measure force.