Dynamics Of Lower Extremity Exoskeleton

Lower extremity exoskeleton (LEE) is a kind of bionic designed passive control wearable carrier whose movements coordinate with those of human while ideally working. Drive command of LEE comes from the expectation of human gait made by the onboard processor after real-time capture and treatment of human motion. With LEE highly linking with human motion, common gait research is necessary to support the mechanical and control system design. Properties of motion and loading also reflect the necessity of mechanic analysis and that it’s insufficient to do a simple static calculation under a single working condition. Exact expectation of the human motion is the essential work of building up the control system and research devoted to control parameter setting to meet the basic human movement would also be important. Motivated by the statement above, the author mainly did the following work:Fit gait curves of lower limb joints under conditions of different speed of walking, one knee on ground and squat while body carried different amount of loads up to60kg by making use of the three-dimensional coordinate change of the markers located on different human body parts. The fitted curves would be analyzed to gain insight into the general laws of human gait which help to guide the bionic design process such as the determination of the degrees of freedom and range change of joint rotation and translation.Based on the study of human components and gait movements, a five-link walking exoskeleton model was built with dynamics being described by Lagrange equations. System topology changes when the heel strikes, making the gait non-derivable. Joints of the model being droved by the fitted curves, the model is capable of calculating both the power compensation on stance phase and energy lost on heel strikes.Establish rigid dynamics and real-time finite elements model droved by fitted curves. Both timing of each joint force and timing of each component stress could be calculated. Such simulation dealing with real-times instead of static strength and stiff analysis of LEE under different kinds of working conditions provides a reference for the material selection, components dimension and optimized design in the whole design process.Achieve both the control calculation of the five-link model and joint control simulation in Adams and Matlab environment. The diversity of posture and grand range of joint movement necessities the control system to have strong robustness and PID control is characterized by such function. The control simulation helps to facilitate and quickly determine the PID control parameters.