Modelling and Control of a Reconfigurable Multipurpose Wheelchair for Elderly/Disabled Mobility

This research is embarking on development of modelling and designing control strategies for a multi purpose wheelchair as a mobile transporter for elderly and disabled people to move in confined and domestic environments independently. The research is aimed at helping people who have physical weakness/disabilities in their upper and lower extremities to move on their own without human intervention. In this work, a novel reconfiguration which allows multi-task operations using the same wheelchair system with compact and simple mechanism is developed for use in confined domestic environment. It can perform manoeuvrability on flat surfaces, stairs climbing (ascending and descending), standing in the upright position on two wheels and transforms back to standard four wheels with reduced initial torque and reduced tilt angle. The wheelchair model is designed in Visual Nastran 4D (VN4D) software with standard specifications of stairs dimension and size. A humanoid model with approximate weight of 71kg is also developed in solid works and incorporated in VN4D to represent a disabled/elderly person. The wheelchair mechanism is based on the link/cluster rotation by lifting the other pair of wheels at the vertical upright position like an inverted pendulum. The completed model in VN4D is then integrated with Matlab/Simulink for control design and performance evaluation. The challenge resides in an appropriate design and implementation of robust controller for the system to guarantee stability of the overall wheelchair while performing multi-function tasks without falling over. A modular fuzzy logic control mechanism with integrated phases is introduced in this work for the two-wheeled stabilization as the main principle of the overall tasks. It is implemented in the stabilizing/landing for stair climbing and sit-to-stand/stand-to-sit transformation control system. Yaw and linear motions are considered in the stair climbing while seat height extension and suspension mechanism are incorporated during standing/sitting control. Moreover, systematic optimization approach is used for the fuzzy input output scaling parameters using spiral dynamic algorithm for performance comparison purposes with heuristic values. Unique rule bases are implemented in all fuzzy modules and controlled independently. The developed control approaches are evaluated through intensive visual simulation and quantitative assessment to verify the proposed control design.