In this paper, we present a vision-based control approach for autonomously docking a wheelchair onto a vehicle lift platform. This is a principle component of the automated transport and retrieval system (ATRS) - an alternate mobility solution for drivers with lower body disabilities. The ATRS employs robotics, automation, and machine vision technologies, and can be integrated into a standard minivan or sport utility vehicle (SUV). At the core of the 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 for the proof-of-concept ATRS. This was driven primarily by geometry constraints, which limited clearance between the chair wheels and the lift platform rails. We present significant simulation and experimental results for our approach. These indicate that the coupling of vision-based localization for feedback and input/output feedback linearization techniques for controller design can provide for accurate wheelchair navigation and reliable docking under a range of ambient illumination conditions