Desgin Of Motor Servo System Based On Exoskeleton

Walking assisting exoskeleton is a rehabilitation robot used for helping patients with lower extremity paraplegia with recovering walking ability.Usually,brushless servo motor is used as its' power source.Because of the purchasing servo driver exists the lack of expansion,complicated communication,expensive and low control problems.This paper designs a motor servo system for the exoskeleton,which focused on the control mode needed in exoskeleton control.The main research contents are as follows:The servo control scheme of exoskeletal brushless motor based on vector control method is realized.The basic principle of vector control is analyzed,the mathematical model of brushless motor is simplified,and the realization method of digital space voltage vector modulation is studied.Combined with the principle of three feedback closed loop control,the servo control simulation model is set up in Simulink,which provides the theoretical basis for the research of key problems and the construction of the actual physical platform.This paper proposed a solution for the exoskeleton system using motor-driven key technology.For current control,the method of reducing the space vector modulation(SVPWM)period is implemented to solve the problem of phase current fluctuation due to the small inductance of the motor winding.For speed control,the phase-locked loop velocity estimation method based on M method is introduced.For the position follow control a simple trapezoidal position interpolation decision method is proposed to make the position interpolation of each point to point(PTP)can be re-planned,with respect to the multi-point interpolation problem,a method of position,velocity and time(PVT)interpolation based on Hermite cubic multi-segment is realized to solve the trajectory following problem of multi-point interpolation.In order to mantain the start position of exoskeleton,a Hall sensor assisted method was introduced to solve the out of sync problem when using the pre-positioning method.The physical drive platform and software platform had been setup.In the hardware desgin,power drive circuit,current sampling circuit,the multi-stage series buck circuit,overcurrent overvoltage detection circuit are analyzed and designed.In order to improve the safety level of exoskeleton,a three phase shrot lead cricuit is designed which can be protect the exoskeleton form falling off when power shut down by forcing the motor enter a high damping state.In the software desgin,the software framework of the servo drive system is decoupled,and the vector control program based on SVPWM is realized to decouple the excitation current and torque current.In communication,the object communication protocol based on CAN communication is designed,which makes the communication of exoskeleton and node more flexible.Compared with the the node controller composed of outsourcing controller in the weight,volume,positioning accuracy,response speed and test on the actual system of the exoskeleton,the outsourcing controller can be replaced by the servo controller designed by this paper.And because of the drive is designed for the exoskeleton,the control of the exoskeleton system is improved,development costs of exoskeleton is reduced,and the ability of independent research and development of exoskeleton is enhanced.