Sliding Guide System Concept for 3D Motion of the Hip Joint in Walking Assist Robots

The human hip joint has three degrees of freedom: flexion and extension, abduction and adduction, and external rotation and internal rotation. However, most current walking assist robots only support flexion–extension of the hip joint and may restrict the unassisted passive movements of other motions. This would cause major problems when used in daily life for such actions as changing direction, recovering from a stumble, and toileting. To solve these issues, the sliding guide system is conceptualized, a very simple and configurable joint mechanism that allows for 3D movement of the hip joint in walking assist robots. As the human femoral head is almost a perfect sphere, the sliding guide system employs two guide plates that contour spherical surfaces projected from the center of the femoral head. The motor unit assisting flexion–extension is configured with these guide plates to passively slide according to the movements of the assist device wearer and enable unobstructed abduction–adduction and external rotation–internal rotation of the hip joint. While systems of various complexities allowing 3D movement are proposed, the sliding guide system concept represents the simplest and most practical approach for implementation in both conventional and future walking assist robot hip joints.