Design of a passive overground body weight support system with forward force

Abstract

Gait rehabilitation attempts to alleviate gait and balance impairments caused by spinal cord injury. Conventional gait rehabilitation often includes unloading a portion of the user’s weight with a vertical force. This vertical force enables people to practice stepping but makes forward propulsion more difficult. Users will adopt a compensatory movement strategy during rehabilitation that may not completely transfer to unsupported walking. It is hypothesized that including a small forward force during vertical unloading makes gait rehabilitation more similar to unsupported locomotion.
This thesis presents and investigates a novel patent of a device that passively generates a forward to propel the user forward. The forward force is generated using the vertical oscillations that naturally occur during gait. This thesis quantifies the forward force, simulates the impact on human gait and details the construction of a prototype. The prototype is then used to validate the simulations of the device.
Analysis indicates that the ratio between the sprocket radius and the wheel radius is the key parameter for determining the amount of forward force. Simulations in which the device is coupled with the spring-loaded inverted pendulum model indicate that the device may generally deteriorate the walking velocity, step size and maximum height difference. Experiments with the prototype indicate that friction has a big effect on the functionality of the device, and that predictions from the simulation may be quantitatively off. The device may have a favorable interaction with the neurological control strategy of human gait, which was not modeled. Human trials will have to give a definite answer.