Individuals with severe physical impairments have difficulties operating electric wheelchairs (EWs), especially in situations where fine steering abilities are required. Automatic driving partly solves the problem, although excessive reliance on automatic driving is not conducive to maintaining their residual physical functions and may cause more serious diseases in the future. The objective of this study was to develop a shared control system that can be adapted to different environments by completely utilizing the operating ability of the user while maintaining the motivation of the user to drive. The operating characteristics of individuals with severe physical impairments were first analyzed to understand their difficulties when operating EWs. Subsequently, a novel reinforcement learning-based shared control method was proposed to adjust the control weight between the user and the machine to meet the requirements of fully exploiting the operating abilities of the users while assisting them when necessary. Experimental results showed that the proposed shared control system gradually adjusted the control weights between the user and the machine, providing safe operation of the EW while ensuring full use of the control signals from the user. It was also found that the shared control results were deeply affected by the types of users.

Persons with Duchenne Muscular Dystrophy (DMD) usually have difficult in operating electric wheelchairs (EWs) using standard input device due to the lack of muscular power and the deformation of their hands. To solve this problem, various kinds of input devices are developed considering their physical limits. However, as the disease progresses, persons with severe DMD will gradually lose the ability to operate the developed input devices. In this study, we first made an investigation of physical functions for persons with severe DMD and found that functions of upper limb, especially functions of the fingers, tended to remain better in at least one-dimensional direction. A novel one-dimensional input device (1DID) was developed for persons with severe DMD based on a quantitative evaluation of the hand functions. Thus, this device can be operated using slight force and one-dimensional movement of a finger. Therefore, persons with severe DMD can adjust the straight and turning motion of an EW using two 1DIDs with the cooperative operation by two fingers. The validity of this device was demonstrated by evaluation experiments of 10 persons with severe DMD including those who do not have a proper input device. The evaluation results also show that the developed 1DID has the possibility to be widely used as a generic input device with computers for persons with severe disabilities.