Safe Movement Planning with DMP and CBF for Lower Limb Rehabilitation Exoskeleton

Abstract

Lower limb rehabilitation exoskeleton robot plays an important role in the auxiliary movement of people with lower limb movement disorders. It’s reasonable movement planning is the guarantee of efficient assistance and safe movement of patients. The existing method for movement planning mostly adopts the fixed track, which can not meet the characteristics of each patient, and is lack of pertinence. To improve the flexibility and the safety of the exoskeleton movement, this paper proposes a movement planning method based on the combination of Dynamic movement primitives (DMP) and control barrier function(CBF). The positional relationship between the crutch support point and the patient's foot is considered. The DMP method is used to simulate the human walking trajectory, the coupling term is added to ensure that the trajectory meets the control requirements. The CBF method is used to dynamically optimize the movement trajectory to ensure that the distance between the patient's foot and the crutch support point and the movement trajectory of sit to stand are always within the safe area respectively. The simulation results show that this method can adjust the step size according to the position of the patient's supporting foot and crutch, and restrict the movement trajectory within the safety set.