Design and control of a robotic lower extremity exoskeleton for gait rehabilitation

Abstract

Off-road operational conditions require large sus- pension displacements and a significant clearance between the ground and the main frame, yielding to an elevated position of the vehicle mass center. Consequently, this makes the vehicle more likely to turn over when cornering fast. This paper proposes a new design, and its associated control, of an active device which improves the stability of fast rover moving up to 10 m/s. The proposed design can be equipped on any off-road chassis which has independent suspensions. We propose the using of an active anti-roll system allowing the control of the roll angle and thus improving the vehicle stability, especially when turning or when moving on slopping ground. The proposed system increases the controllability of the vehicle, by giving access to the roll angle which is usually uncontrollable. We develop a model based predictive controller for the roll dynamics, which minimizes the load transfer during cornering and the energy consumed by the actuators. The control model is based on a dynamic model of the rover and on a stability criteria defined by the lateral load transfer. Dynamic simulation, carried out for different rover trajectories with different speeds, show the benefit of the proposed active system and the validity of the control approach.