Modelling and control strategies for a motorized wheelchair with hybrid locomotion systems

Several kinematic and dynamic models of conventional motorized wheelchairs in the literature presume the wheelchair movement only on flat surfaces, disregarding the effects of gravitational forces and rolling friction. In addition, there are no many studies clearly describing how the dynamic properties of a conventional wheelchair and stair-climbing wheelchair with a track mechanism are formulated. However, the design of a good controller generally involves the formulation of a comprehensive wheelchair model. This work contributes to the modelling of the motorized wheelchair with hybrid locomotion systems (MWHLSs), which have wheel and track mechanisms to move the wheelchair, regarding the formulation of kinematic and dynamic models for each locomotion system, considering the effects of gravitational forces and rolling friction, on flat and inclined surfaces and climbing stairs. From the mathematical model for each locomotion system, the gearmotor torque control is used, since the torque provides smooth and precise driving. Thus, the open-loop and closed-loop control techniques, such as control Lyapunov function, Backstepping control, and Proportional-Integral-Derivative controller, are designed due to their well-known characteristics. The robustness analysis of these controllers, taking into account the occurrence of external disturbances, indicates which one best assists wheelchair users, providing a safer and more efficient navigation with the MWHLS.