Trends in nonlicensed mobility aids.

The scope of nonlicensed vehicles includes electrically powered wheelchairs, golf-cart-type vehicles, a variety of multifunctional devices, and some gasoline-engine-powered vehicles . Until several years ago, the standard nonlicensed powered vehicle was the Everest & Jennings "34" Power Drive Wheelchair (Fig . 1) . This unit has been directed to institutions and general indoor environments where it has enjoyed considerable success. Several offshoots of the basic Power Drive include the Motorette, the Rolls Electric Wheelchair, and the Everest & Jennings "33" Power Drive . All of these powered wheelchairs, including the "34" Power Drive, are normally operated by hand-manipulated joy sticks. The Everest & Jennings "34" Power Drive and the Rolls Electric Wheelchair are essentially equivalent in performance . The former incorporates a belt drive while the latter uses a direct friction' drive . The Motorette (Fig . 2) is rather novel in that it is an "add-on" assembly, capable of converting virtually any conventional wheelchair into a powered unit . Both the Motorette and the Everest & Jennings "33" Power Drive incorporate proportional control joy sticks, exemplary of an introduction of electronics into physical rehabilitation . The more severe spinal-cord-injured quadriplegic and similarly paralyzed individual are generally unable to use manual joy-stick controls . Several years ago, Everest & Jennings introduced a chin-controlled joy stick (Fig . 3) . The aerospace industry generated considerable initial excitement with the Sight Switch (Fig . 4), that depended upon movement of both eye balls to effect wheelchair control via special optical switches . Breath controls have appeared in some clinics and other techniques are being investigated. It is interesting to note that the two common types of wheelchair drives, including belt and direct friction drives, have both been under attack from time to time for a variety of reasons . For instance, the direct friction drive generally exhibits excessive tire wear while the belt drive usually requires frequent adjustment and is difficult to push when