Wheelchair virtual joystick interface

Video games can be used as a motivational tool to promote exercise among individuals with disabilities. The velocity of the wheels of a stationary wheelchair is used as a control interface for video games. This interface is implemented with an entirely digital system. An MC68HC11A1 microcontroller is used to perform quadrature on the input of two optical encoders and dynamically adjust two X9C104P digital potentiometers. The result is a virtual joystick which is controlled by the speed and direction of the wheelchair wheel rotation. This system can be mounted to any personal computer game port and used for virtual reality applications as well as games.