Motion planning and balance analysis of robotic exoskeleton with balance stabilizer mechanism

Abstract

Nowadays, in conventional gait rehabilitation, physiotherapist assistant (PTA) plays the main role in improving patient’s physical and mental functioning. Normally, several PTAs are required to assist one patient in guiding his/her limbs in rehabilitation training, which is considered as a highly labour intensive task. Therefore, to overcome the drawbacks of manually assisted gait rehabilitation, robotic assisted gait rehabilitation robot especially wearable exoskeleton type has been emerged to meet the history of destiny. It is implemented by experienced therapists to help the patient do stall-recovery exercise. However, most of the wearable exoskeleton robots require the user to use a crutch to balance themselves since most of the systems are under-actuated. This may cause a potential hazard and high energy-consumption if the user cannot use the crutch properly to coordinate with the exoskeleton device. This report focuses motion planning and balance analysis of a wearable lower-limb exoskeleton robot with a balanced stabilizing mechanism. The balance stabilizer mechanism can act as the role of “robotic crutch” and thus can help reduce the user-dependency on crutch while walking with the exoskeleton-type device. In this report, a background study on human gait pattern and gait rehabilitation robotic exoskeletons is conducted, which confines the scope and objectives of this project. Then an inverse kinematics model has been set up for the exoskeleton robot with a balance stabilizer mechanism. By providing the hip motion and ankle motion of the robot, the inverse kinematics can be used to calculate the joint angles to allow the exoskeleton to move synchronously with the balance stabilizer mechanism. At last, the stability of the system is analyzed by using the Zero Moment Point (ZMP) criteria. An unbalanced motion filtering method has been proposed based on the analysis which can generate a stable motion for the system. In the conclusion chapter, summary and recommendations for future improvements are included.