Development Of Wrist Rehabilitation Robot Based On Coaxial Spherical Parallel Mechanism

Stroke is a disease with a high disability rate,among which wrist function impairment is one of the common sequela after stroke.Postoperative rehabilitation training is necessary to improve the quality of life of patients.Compared with other medical methods,rehabilitation robots can feed back accurate treatment effects and ensure the accuracy and strength of rehabilitation,so the application is becoming more and more extensive.Aiming at the particularity of wrist rehabilitation training and the problems of incomplete freedom and poor pertinence of existing rehabilitation robots.In this research a wrist rehabilitation robot based on a coaxial 3R spherical parallel mechanism is proposed from the perspectives of overall mechanism design,kinematics analysis,controller design,prototype development,and experimental testing.In research the mechanical structure and controller design of the wrist rehabilitation robot are developed based on the physiological characteristics of the wrist and rehabilitation theory.After comparing and summarizing the existing rehabilitation robots,the coaxial 3R spherical parallel mechanism is finally determined as the end effector.The mechanical structure ensures that the motion trajectory of the mechanism fits the wrist trajectory,and a flexible rotating joint is designed to cope with possible impacts.Three-axis nesting design is adopted to solve the problem of coaxial transmission of multiple drive shafts.In the electrical system,with Lab VIEW as the core of the host computer,the wrist rehabilitation robot control system is developed,including sensor communication module,inverse kinematics solving module,motor control module,and user interface to realize real-time feedback of motion data.In the user interface,patients can customize rehabilitation-related parameters according to their own conditions and choose the degree of freedom of rehabilitation,which provides more options for rehabilitation..Aiming at the multi-solution problem of the inverse kinematics of the end effector,based on the kinematic analysis,a step-by-step calculation method is proposed.The rotation of the moving platform is divided into two steps:first around the X,Y axis,then around the Z axis.The optimal input angles θi*and φi required for the proximal link in the two-step rotation are calculated respectively,and add the last two parts to obtain the complete input angle θi.The multi-solution problem of inverse kinematics is solved,the unique solution of inverse kinematics can be obtained,and the unique corresponding relationship between the motor input angle and the pose of the end effector is determined,which provides a theoretical basis for the design of the control system.And the robot workspace is calculated to verify the rationality of the design.Finally,the physical prototype was processed,the experimental platform was built,and the experimental research of the wrist rehabilitation robot was carried out.The position control experiment and the function experiment were carried out respectively,and the performance of the rehabilitation robot was tested through a series of experimental curves of sensors.The research results prove that the mechanical structure design of the wrist rehabilitation robot designed by this institute is reasonable and full of freedom.The rotation angle of the end effector around the X axis is[-32°,32°],and the rotation angle around the Y axis is[-37°,37°].The Z axis rotates all around.The proposed step-by-step calculation method can obtain the unique solution of inverse kinematics,the control system is accurate and reliable,and the posture error is about 1°.the whole machine runs smoothly and can meet the needs of wrist rehabilitation for patients with carpal-foot cerebral apoplexy.