Autonomous docking of a smart wheelchair for the Automated Transport and Retrieval System (ATRS)

The Automated Transport and Retrieval System (ATRS) represents a technology-based alternative to van conversions for automobile drivers in wheelchairs. Rather than requiring dramatic, permanent, and expensive modifications to the host vehicle, ATRS employs robotics and automation technologies and can be integrated noninvasively into a standard minivan or sport utility vehicle. At the core of ATRS is a “smart” wheelchair system that autonomously navigates between the driver’s position and a powered lift at the rear of the vehicle, eliminating the need for an attendant. From an automation perspective, autonomously docking the wheelchair onto the lift platform presented the most significant technical challenge due to limited clearance between the chair wheels and the lift platform rails. To solve the docking task, we employed a light detection and ranging (LIDAR)–based approach for wheelchair localization coupled with a hybrid motion controller design. Extensive testing from the localization subsystem to the complete ATRSwas conducted under representative usage conditions. This included 3 days of public demonstrations indoors at the World Congress on Disabilities, where potential end users were able to evaluate the system. In this environment, ATRS performed more than 300 consecutive cycles without failure. During 2 days of outdoor reliability testing, 97.5% docking reliability was observed. The system is scheduled to enter the commercial market in 2008.