Design of a Cable-Suspended Robot for Early Stage Gait Rehabilitation

Practicing walking motions while supine might help accelerate recovery after neurologic injury. This paper presents the design, modeling, and initial testing of a novel cable-driven device called AirStep that compensates for the weight of the legs, facilitating air-stepping practice while supine. AirStep integrates multiple mass-spring counterbalancing mechanisms to minimize the effect of gravity throughout the entire gait cycle such that patients can perform active or passive stepping motions in a near-zero gravity environment. Handles allow a rehabilitation therapist to manually assist leg motion through the cables as needed. Data acquired from an optical motion capture system validated the mathematical model of the AirStep, showing that the leg trajectories in air-stepping resembled those from running. In pilot testing, two individuals with spinal cord injury (SCI) required manual assistance at the hips from a physical therapist to achieve step-like motions through the AirStep interface. AirStep can apply low-forces, allow stepping in the supine position, and can quantify changes in patient-generated force production. Compared to other rehabilitation robots, AirStep offers the advantages of a low-cost mechanical structure, high acceptability by the patient and easy transportability aside a hospital bed, making the AirStep a good candidate for adoption in the early-stage gait rehabilitation.