Design of a Semi-Autonomous Wheelchair with Obstacle Avoidance for Physically Challenged Persons in Anambra State

Limited access to affordable assistive mobility technology remains a significant barrier for physically challenged individuals in Anambra State, South East Nigeria, where commercially imported electric wheelchairs are prohibitively expensive for most users. This project presents the design of a semi-autonomous electric wheelchair incorporating ultrasonic obstacle avoidance and a joystick-based manual override control interface. The wheelchair platform uses two 24-volt brushless hub motors mounted on a modified steel wheelchair frame, controlled by a dual-channel motor driver interfaced with an Arduino Mega microcontroller. Three ultrasonic sensors mounted at the front and sides of the chair detect obstacles and trigger automatic deceleration or directional correction. The joystick provides intuitive directional control, while a mode-switching button enables transition between manual and assisted-navigation modes. The system was evaluated with 12 volunteer users with varying mobility impairments over two weeks of indoor and outdoor navigation trials. Users reported significant improvements in ease of navigation and confidence compared to manual wheelchair use. Obstacle detection performed reliably up to a range of 80 centimetres, with a false alarm rate of 4 percent attributed to irregular floor surfaces. The total fabrication cost was estimated at 185,000 Naira, far below the import price of equivalent foreign-made electric wheelchairs. This study demonstrates the feasibility of locally designed assistive robotics for improving the quality of life of physically challenged Nigerians. Keywords: electric wheelchair, obstacle avoidance, assistive technology, physical disability, Anambra State