Research On Control Strategy Of 7-DOF Exoskeleton Manipulator

Cerebral stroke,also known as"stroke"or cerebrovascular accident,is a kind of brain tissue injury caused by sudden rupture of cerebrovascular or abnormal flow of blood into the brain due to vascular obstruction.Research shows that stroke is an important cause of disability and death worldwide,accompanied by a trend of younger patients.Aiming at the problem that the patient's brain nerve can't control the limb movement effectively,helping the patient to stimulate the repeated limb movement to re-establish the relationship between the injured nerve and the patient's limb is the mainstream treatment at present.Seven-degree-of-freedom(DOF)upper extremity exoskeleton manipulator is a wearable device attached to human upper limb.Its movement mode is consistent with human real arm movement.It is more and more used in medical rehabilitation equipment.Therefore,the research on control strategy of seven-degree-of-freedom upper extremity exoskeleton manipulator has broad application prospects and scientific research value in rehabilitation engineering.By analyzing the motion characteristics of 7-DOF upper extremity exoskeleton manipulator,this paper studies two control strategies of servo-assisted control and active control for patients with different degrees of illness,and builds a control system experimental platform of 7-DOF upper extremity exoskeleton manipulator.The main work is as follows:Firstly,the D-H parameter method is used to analyze the forward kinematics of the 7-DOF exoskeleton manipulator,and the kinematics model of the exoskeleton manipulator is established by MATLAB to verify the forward kinematics analysis.On the other hand,the dynamic analysis of the 7-DOF exoskeleton manipulator is carried out by Lagrangian dynamic analysis method,and the exoskeleton manipulator is established by MATLAB software.The dynamic model and the moment change of each joint during the manipulator movement are obtained by simulation.Finally,the dynamic analysis is verified by Adams.The workspace of the exoskeleton manipulator is limited to ensure that the Rehabilitation Exoskeleton manipulator meets the normal range of motion of human upper limb joints in the working process,and provides an effective theoretical basis for the setting of the follow-up force of the experimental verification part.Secondly,seven joints are connected in parallel and the same control method is used for the rehabilitation training of patients with mild symptoms in the workspace of 7-DOF exoskeleton.Through the real-time data acquisition by the moment sensor and encoder,the motional intention of seven upper limb joints of the patient is acquired by the exoskeleton,and the difference between the moment sensor of seven joints and the set assistant value in the direction of motion is taken as input.The output speed of seven joints is solved by PID control,and the set assistant force is realized to the patient according to the real-time rotational intention of each joint.Finally,the feasibility of the servo-assisted control strategy is preliminarily verified by a three-degree-of-freedom translational manipulator platform.Thirdly,for patients with severe illness,the upper limbs have been unable to generate the initiative to exercise,and can not provide their own motional intentions.Based on the control method of learning human strategy,using the same motion of the patient as a template in the servo-assisted control mode and the idea of dynamic time warping algorithm,the data sets of joint angles collected in multiple movements are regularized.Finally,the joint angle change function is fitted by the expression of Fourier series,and the reference motion track of active control mode is gradually constructed.Trace bank.According to the reference trajectory,the active control of exoskeleton manipulator is realized by position control of seven joints.Finally,according to the servo-assisted control mode and the active control mode,a seven-degree-of-freedom exoskeleton manipulator experimental platfor m is built to verify the feasibility of the control strategy.The circuit structure,software framework and communication system of the seven-degree-of-freedom exoskeleton manipulator system are designed and constructed.By analyzing the motion mechanism of human upper limbs,the experiments of seven-degree-of-freedom exoskeleton manipulator servo-assisted motion and the experiments of seven-degree-of-freedom exoskeleton manipulator active control are carried out respectively.The feasibility of the proposed servo-assisted control strategy and active control strategy is validated effectively.