Desing of self-locking planetary gear trains for reahbilitation engineering and mobility devices.

Abstract

Muscular weakness produced by different pathologies increases year after year. Numerous devices can be used by subjects to assist or rehabilitate gait, such as Stance-Control-Knee-Ankle-Foot-Orthoses (SCKAFOs). These devices permit control of the whole gait cycle, both during the swing phase and the stance phase of gait. The majority of these SCKAFOs use sensors or actuators for their functioning. This thesis presents the development of a new SCKAFO which can be used on any subject. The device is fully mechanical and can self-lock under any knee flexion angle. The main component of the system is a Planetary Gear train (PGT) with self-locking capability. This permits the movement of the orthosis during the swing phase, and the locking of the device during the stance phase of gait. Consequently, subjects control the gait cycle without using any sensor or actuator. Although wheelchairs have seen great technological improvements, the majority continue to be manually propelled because of their low prize, lightness, transportability and folding capacity. Ramp climbing requires great muscular effort and can be a major problem for wheelchair users, it often prevents such users from ascending ramps and can cause problems in their daily life. The use of a planetary gear train as a mechanical propulsion system to facilitate the ramp climbing and consequently reduce muscular effort is shown. This system consists of a planetary gear train with self-locking capability and thus permits the user to climb ramps when propelling the wheelchair and to self-lock when there is no power input. The system is a speed reducer, which means that when the user ascends ramps significantly less muscular effort is required. In addition to this, when using a self-locking PGT no external actuation is required to brake the wheelchair. In this work, two new applications of self-locking planetary gear trains in rehabilitation and assistive devices fields are presented. The first application, a new SCKAFO which assists gait in subjects with lower limb injuries, it uses a completely mechanical device suitable for any user. The second application, a propulsion system for manual wheelchairs, improves the mobility of manual wheelchair users using a system that can be adapted to any user and any manual wheelchair.