A speed compensation algorithm for a head tilts controller used for wheelchairs and rehabilitation applications

As quadriplegia patients lost the ability to control the upper and lower limbs due to upper spinal cord injury, they need an intelligent control system to use a traditional electric wheelchair, which is driven normally by a joystick controller. One of the successful control systems for this kind of user is the use of head tilts as a controller. It allows the quadriplegia patient to drive the rehabilitation wheelchair with the head tilt or motion around x, y and z-axes. In this paper, the design and realization of a speed compensation algorithm are proposed. The speed compensation algorithm enhances the head tilts controller performance in case of non-straight roads and passing ramps. It is designed to compensate the lost speed in one or both of the wheelchair motors depending on the value of the road slope angle and the user weight. The algorithm uses a closed loop control by receiving speed feedback from two magnetic encoders fixed at the wheelchair motors. The speed of each motor is calculated by counting the number of wheels rotating per time. The wheelchair position and slope information acquisition are realized using a sophisticated Bosch BNO055 orientation sensor fixed on the wheelchair chassis. The practical tests showed excellent performance for the system enhancing both the control and the safety of the user.