Research On Deformable Exoskeleton Robot Combined With Wheelchair

With the aggravation of the aging population,people pay more and more attention to medical rehabilitation.As a wearable and intelligent device to improve human motion ability,exoskeleton robots are gradually applied in the field of helping the elderly and the paraplegic.This paper developed a lower limb exoskeleton robot for people who are disabled or weak in their lower limbs.It can not only help users recover walking ability and provide assistance,but also can deform into an electric wheelchair when users are tired,so as to save their physical energy and make it more convenient to travel.According to the application requirements of exoskeleton robots,this paper discussed the design of electromechanical system,system modeling and analysis,control strategy and related experimental tests.Exoskeleton robot is a typical mechatronics equipment.Reasonable mechanical structure and stable electrical system are the basis of its function realization.Based on four-bar linkage,the deformation mechanism between exoskeleton and wheelchair was designed and ensured the safety and convenience of the deformation process.The exoskeleton knee joint and hip joint with high integration and high torque output were designed by using hypoid gear transmission.Electrical system needs to assist mechanical structure to realize the control method and function of the robot.A distributed control system based on ARM+CAN was designed.In order to improve the system integration,a high precision joint angle sensor based on magnetic encoder and a wireless intelligent crutch sensor system were designed to ensure the collection of real-time state information of the system with IMU module.Exoskeleton modeling and analysis are the premise of exoskeleton control.In this paper,kinematics modeling,dynamics modeling and stability analysis of exoskeleton robot were carried out.Through kinematics analysis,the relationship between the posture of each joint and the joint angle is determined.The dynamic model of exoskeleton was established by Lagrange method,which unifies the swing phase and stance phase of the human-machine system with crutches.The correctness of the dynamic model was verified by dynamic simulation through ADAMS.Due to the low-speed motion characteristics of the system,the stability of exoskeleton is judged by static stability criterion,based on which the stabilities of walking,deformation and wheelchair mode were analyzed by simulation.Considering that the application population of exoskeleton are the disabled,the exoskeleton adopts passive control method.Based on the principle of "safety first",in the walking mode,according to the support point of the system and the basic gait trajectory,the quadratic programming was carried out to ensure that the system has sufficient stability margin at all times.The deformation trajectory was planned with the gradient descent method to make the CoG point as far as possible in the expected range to ensure the safety and reduce the burden on the upper limbs of the human body.In wheelchair mode,the gradient of the ground is identified by measuring the back attitude,and chang the shape of the four-bar linkage to place the CoG of the system in the stable support plane.Finally,the exoskeleton system was integrated tested.Based on the joint basic experiments,wearing experiments were carried out on human body and the functions and practicability of exoskeleton were verified through walking on the flat ground,deforming and wheelchair driving experiments.