Adaptive Motion Control of Nonholonomic Intelligent Walker-Human Systems

This paper focuses on motion control of active intelligent walkers robust to system parameter variations and uncertainties. It presents a new realistic control-oriented model and, based on this model, an adaptive motion control design to generate appropriate torques to keep the i-walker in front of the user at the desired distance. Our control design utilizes inverse kinematics equations derived horn a two-body kinematic model and to adaptively generate the reference velocities for maintaining ideal relative position of i-walker with respect to the user. The torques to track the reference velocities are generated using an adaptive proportional-integral-derivative Control scheme, which is robust to unknown torque disturbances, combined with a computed torque based feedback linearization unit and a high gain observer to estimate the wheel velocities. The designed control scheme is formally analyzed and simulation tested for both symmetric and asymmetric gait patterns. (C) 2016, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.