Comparative study on compatible and incompatible configuration of a wearable lower-limb exoskeleton

Xia Zhang*, Shuai Lin, Sihan Tao

College of Mechatronics and Automobile Engineering, Chongqing Jiaotong University, Chongqing, China

Objective: To solve the problem of incompatibility of human-exoskeleton kinematics in the existing rigid lower-limb exoskeleton in the human-exoskeleton closed-chain environment, and to summarize the simulation results.

Methods: The advanced mechanism theory and method are used to calculate the number of passive DOFs in the lower-limb joints therein. Through configuration optimization, a novel human-exoskeleton compatible configuration scheme is established, and the overall structure design of the lower extremity wearable exoskeleton is further completed based on the human-exoskeleton configuration scheme. Secondly, exoskeleton kinematics research is conducted, the D-H method is employed to establish the lower extremity exoskeleton kinematics equation, and the exoskeleton ankle joint motion area is acquired through solving positive kinematics equations. The lower extremity trajectory of the human body during regular walking is obtained using Adams.

Results: Simulation results confirm that the exoskeleton ankle joint motion area is compatible with the human ankle joint motion area. Further using Adams to carry out exoskeleton walking motion simulation test, the results show that the exoskeleton and human ankle joint movement trajectories are similar. Finally, a simulation test of human-exoskeleton motion matching degree verification is conducted, and a human-exoskeleton joint simulation model is established using Adams to compare the human-exoskeleton motion matching degree between the compatible configuration scheme and another seven types of incompatible schemes.

Conclusion: The test results show that under the compatible configuration scheme, the deviation of the angular displacement of the human-exoskeleton joint is the smallest, which verifies the effectiveness of the exoskeleton compatible configuration.