Designing a User-Centred and Data-Driven Controller for Pushrim-Activated Power-Assisted Wheels: A Case Study

Pushrim-activated power-assisted wheels (PAPAWs) are power add-ons that can provide propulsion assistance to manual wheelchair users. These assistive devices operate based on a collaborative control scheme, in which the wheelchair user is an integral part of the control framework. In this work, we aimed to develop a user-centred PAPAW controller that can estimate implicit user intentions (i.e., states of wheelchair motion) and provide adaptive torque assistance accordingly. The proposed framework consists of a data-driven intention-inference module as well as a torque-based controller with adaptive gains. Experiments were conducted to collect kinetic and kinematic data for a variety of common wheelchair activities. Kinetic measurements were used with probabilistic algorithms to develop a user intention estimation model. After the user intent was determined from dynamic user-pushrim interactions, the assistance torque was regulated by adjusting the controller gain to reflect user intent. We evaluated the performance of the intention-based controller in simulation and compared its performance with previously developed PAPAW controllers. We used kinetic and kinematic data from experimental measurements and system identification methods to derive the dynamic model of the user-wheelchair system which was used for evaluation purposes. The outcome of our evaluations showed that using an intention-based controller can reduce unwanted wheelchair deviations from the desired path. User experiments should be conducted to validate these simulation outcomes and verify the clinical relevance of using this intention-based controller.