Gravity balancing rehabilitative robot for the human legs

People with severe muscle weakness from neurological injury, such as hemiparesis from stroke, often have substantial limitations. The focus of rehabilitation after stroke is often on walking function, however, equipment available to facilitate walking function is severely limited. Most devices move patients through predetermined movements rather than allowing the patient to move under their control. This work presents the design of a gravity balancing rehabilitative robot to assist persons with both leg impairment to walk through elimination of the effects of gravity. The design of the machine is based on a hybrid method for gravity balancing, with two steps: (i) locate the center of mass of a machine using auxiliary parallelograms; (ii) select springs to connect from the center of mass such that the total potential energy of the system is invariant with configuration. The design of the machine considers all motions of the leg and the pelvis by assuming the center of mass of pelvis to be located on the line joining the two hip joints. Preliminary version of this machine, with limited features, is being fabricated.