Trajectory generation for ankle rehabilitation: A biomechanical model based approach

Biomechanical information can be used in the design and control of rehabilitation robots to enhance the safety and performance of these devices. In this work, a trajectory generation routine has been developed whereby the rehabilitation trajectory is produced from constrained optimization of a cost function which is computed from the outputs of a biomechanical model. Specifically, a rigid body based biomechanical model for the human ankle has been constructed and used to estimate the tensions along ligaments and tendons, as well as the joint reaction moments at a given foot configuration. These quantities can then be used to define an objective function to be minimised. Simulations have shown that a 20% reduction in cost function can be achieved using this method. Inspection of the optimized trajectory shows that the shortest path between two foot configurations is not necessarily the most optimal, thus highlighting the applicability of the proposed method in rehabilitation robots.