Jerk Trajectory Planning for Assistive and Rehabilitative Mechatronic Devices

This paper presents an effective application of Jerk to plan trajectory and control undesirable effects (e.g. patient’s hesitations and tremors) in active rehabilitation training using some mechatronic devices. Jerk is the time derivative of acceleration, and it is associated to the rapidly changing of forces. It is more sensible than other parameters (e.g. speed or acceleration) to intercept undesirable conditions as the patient’s tremors or sub-movements. This study proposes an innovative regulator system based on Minimum Jerk trajectory planning and formulation. The trajectory planning strategy of limb rehabilitation is described considering the clinical therapy requirements and patients’ needs. A case study  based on a path shape that simulates a point-to-point motion is illustrated to demonstrate the effectiveness of the proposed solution. The study presents the kinematic analysis of the mechatronic device and the formulation of the objective function to minimize Jerk along the trajectory. A controller was developed to attenuate the micro sub-movements that recreated the patient hesitations. A set of simulations of the mechatronic model was performed highlighting the reduction of the jerk peak magnitude and the deviation from pre-determined trajectory when the controller was activated, improving the rehabilitation training.