The Research About Motion Stability Of Lower-limb Rehabilitation Exoskeleton

The motion stability control is an essential requirement when researching a lower-limb rehabilitation exoskeleton.Due to the complexity and variability of the force condition of a bipedal walking exoskeleton,it is very difficult for paraplegics wearing an exoskeleton to control the stability by themselves,which could bring them a potential safety hazard.Therefore,for the sake of wearers' personal safety,this paper carried out a research about motion stability of the lower-limb rehabilitation exoskeleton.On the base of searching and reading large numbers of relevant academic literatures,the writer detailedly analyzed the ZMP motion stability theory.Then,derived from the theoretical basis above,control strategies of motion stability for exoskeleton was designed.Last but not least,software and hardware of a motion stability control system was realized.The main research work are summarized as follows:Firstly,taking the five-bar linkage mechanism model,which is frequently used in traditional research of robotics,for reference,the writer built a four-footed mechanism model for our exoskeleton,combining the characteristics of crutched walking in the application scenario of rehabilitation training.Then the kinematics and dynamics of the four-footed model were analyzed.Kinematics model based on D-H method was established,which explained the relationship between end effector position and joint angles.Dynamics model based on NewtonEuler method was also built,which worked out the driving torque of all joints in the movement of exoskeleton.They provided theoretical basis for both the optimization design of driving mechanism and the motion stability control below.Secondly,this paper used ZMP theory to analyze the condition of exoskeleton's motion stability.Then,in order to improve the insufficient of using traditional ZMP computing method in now available lab scenario,the writer proposed a ZMP detecting method based on the force information of supporting points.Subsequently,a control strategy for gait-trigger stability was designed,which depends on the detecting method above.Lastly,a gait planning method based on Jacobian was proposed.Finally,the implement of a motion stability control system was discussed.In the process of building the hardware platform for data acquisition,the hardware realization of the ZMP detecting method above deserves an emphatical discussion,which includes the design of foursupport-point sole structure and the realization of acquiring pressure and tilt angle data.Then,the software modules including the standing stability control and the gait-trigger stability control were programmed.Lastly,a series of experiments were conducted to verify the engineering application effect of the proposed stability control system.Practice had proven that the standing stability control of this system can effectively correct the unstable situation in which the ZMP deviates from the stable region.Besides,the bipedal gait realized by gait-trigger stability control and gait planning of this system has good performance in both coordination and stability.