Assisting control for attendant propelled wheelchair based on force velocity relationship.

There is a need to develop an assisting device which can be adapted to the individual capabilities of elderly attendants, which would allow them to maintain a level of fitness when pushing a wheelchair, while minimising the risk of injury to them. Furthermore there is a need to reduce the overall energy consumption of the device in keeping with the current trends of reducing carbon emissions. The control system for attendants pushing wheelchairs that reduces the energy needed by the assisting device is an increasing trend of optimisation of assistive technology devices to individual capabilities to ensure less energy expenditure of the attendant. The control parameters for existing assisting systems for attendant wheelchair propulsion are difficult to optimise for individual capabilities. We focus on the individual propelling performance, and propose an assisting control method based on the force velocity relationship of the individual. Our proposed assisting controller generates an assisting force when the attendant's propelling force exceeds an assisting boundary defined by the force velocity relationship. In this paper, we tested the performance of the assisting controller based on force velocity (FV) relationship using simulation. The simulation used an attendant wheelchair model with parameters determined from experiments. From the simulated results of the assisting force trajectories, the FV assisting system worked as we defined. The FV assisting system used less energy consumption than the existing proportional assisting systems. Also the FV assisting system would have a limit of maximum attendant propelling power, so the distribution between the attendant force and the assisting force can be easily adjusted to the individual's force velocity relationship. Our proposed FV assisting system would be useful as it would allow an optimised system based on individual capabilities to be created for rehabilitation/training systems, which would allow optimum energy consumption when propelling a wheelchair.