Gait Control Of Lower Limb Exoskeleton In Passive Mode Based On Active Disturbance Rejection Technology

As a new type of human-machine integrated device,the wearable lower limb exoskeleton combines the powerful mechanical power of the robot with human intelligence,and can also provide additional power to the body while enhancing human function.With superior auxiliary characteristics,lower extremity exoskeleton has been widely used in medical,military and other fields,and has become a research hotspot in the field of robotics in recent years.In this paper,passive exoskeleton exoskeleton system is taken as the research object.Based on the analysis of human lower extremity mechanism and walking mode,the research on gait planning and trajectory control is focused on the system structure design and the exoskeleton movement characteristics in passive mode.The main work of the study is as follows:1 Assumption of the structure of exoskeleton system of lower limbs.Summarize the research results of the existing literature,combine the human gait characteristics to determine the configuration of the exoskeleton system degrees of freedom and other relevant details,and complete the preliminary design of the whole machine structure.2 Kinematic analysis and dynamic modeling.According to the gait phase analysis,the gait characteristics of the system are obtained,and the improved D-H representation in robot kinematics is used to verify the correctness of forward and inverse kinematics.On this basis,the dynamic model is obtained by the Lagrange equation method,and the support stage and the swing stage are modeled separately.In order to provide a suitable application platform for the subsequent gait planning,the ADAMS dynamics simulation software is used to perform three-dimensional modeling of the extremity exoskeleton system.3 Parameterized gait trajectory planning.In the passive mode,the characteristic of the human-machine system is that the exoskeleton is dominant to drive the human body to walk.At this time,the rational planning of the humanoid gait of the exoskeleton is the key research content.The constraints of the walking process are determined according to the analysis of the human walking model,and cubic spline interpolation is used to ensure the continuity of the parameterized trajectory.The obtained parametric trajectories are inverse kinematics to obtain the expected joint trajectory,and then the ADAMS dynamics simulation is used to verify its rationality.4 Tracking control of planned trajectory.Due to the influence of the system model and the outside world,the planned trajectory often cannot achieve accurate tracking control.Aiming at this problem,an auto disturbance rejection control strategy is proposed based on the dynamic model obtained from the dynamic analysis.The unmodeled dynamics of the system,the dynamic coupling between the systems and the external disturbances are regarded as total interference.An expanded state observer is designed to estimate and feedforward compensation is used to suppress the influence of interference.Through the designed error feedback controller,the tracking control of the desired gait trajectory is achieved,and the proof of the bounded state of the extended state observer and the stability of the closed-loop system are given.Finally,the effectiveness of the proposed control strategy is verified in MATLAB/Simulink.