A Computational Biomechanical Model of the Human Ankle for Development of an Ankle Rehabilitation Robot

Biomechanical information of the human body can be used to improve the safety and performance of rehabilitation robots. This paper proposes a computational biomechanical model of the human ankle. Focus is placed on the hind foot where the ankle kinematics is described by a biaxial model and foot bones are modelled as rigid bodies. Ligaments and muscle-tendon units are represented as tension only force elements and their dynamics are combined with those of the foot bones to give a state space model to describe the ankle dynamics. Simulations of the resulting model have been used to compare the behaviour of the resulting model with both experimental results and data available from literature. It was found that the responses of the model are within the same order of magnitude of real world data. Sensitivity analysis of the model has also been carried out under static conditions and it was found that the model parameters which have the greatest influence on the interaction forces and moments are the rest lengths of ligaments and tendons. The developed model can be a useful tool in the development of an ankle rehabilitation robot by providing a means for controller simulation and trajectory generation.