Gravity Balancing of a Human Leg using an External Orthosis

Gravity balancing is often used in industrial machines to decrease the required actuator efforts during motion. In this paper, we present a new design for gravity balancing of the human leg using an external orthosis. This external orthosis is connected to the human leg on the shank and its other end is fixed to a walking frame. The major issues addressed in this paper are: (i) design for gravity balancing of the human leg and the orthosis, (ii) kinematic compatibility of the human leg and the external orthosis during walking, (iii) comparison of the joint torque trajectories of the human leg with and without external orthosis, and (iv) effects of variation of the link lengths and masses of the human leg on the inertia of the external orthosis. We illustrate feasible 2D and 3D designs of the external orthosis through computer simulations. Fabrication of this design will be the subject of future work.