Study On Control System Of Lower Limb Rehabilitation Trainer

For patients with leg movement disorders caused by trauma,hemiplegia,cerebral thrombosis and so on,lower limb rehabilitation training is a necessary physical therapy,and the traditional treatment methods are generally completed with the assistance of the rehabilitation therapist or family members,which will consume greater manpower and physical strength,and the intensity and angle of training is not easy to control.Therefore,the research of rehabilitation training device can meet the actual needs of patients and conform to the scientific treatment,which has a high practical value for patients.Looking at the existing lower limb rehabilitation trainers,most of them are designed in terms of mechanical structure and driving device,but few are designed in terms of motor control strategy.In the selection of lower limb drive motor,most of them focus on DC brush motor,which limits its further application in high-performance medical instruments.On the control strategy,find that most of them adopt is the most common PID control of industrial robots,although the error in the control of motor output is small,after the transmission mechanism is connected,the single speed feedback can not cope with the problem of speed vibration caused by the patient’s legs,the initial error is large,easy to cause overshoot,and is not suitable for the actual rehabilitation training of patients.In order to solve the above problems,this paper,based on an improved pedal-type lower limb rehabilitation training mechanism,combined with advanced control technology and human-computer interaction means,completed the design and development of the control system hardware and software.Firstly,this paper describes the mathematical model of permanent magnet synchronous motor in the dq axis coordinate system,adopts coordinate transformation to realize the decoupling of motor control,so that the motor can achieve the control effect similar to that of DC motor,and establishes the speed regulating model of permanent magnet synchronous motor based on the vector control principle of id=0.Combined with the space voltage vector pulse width modulation technology,The Matlab/Simulink simulation model of permanent magnet synchronous motor vector control was built to verify the effectiveness of vector control strategy and SVPWM module,which laid a theoretical foundation for the control algorithm of the underlying motor of the controller.Secondly,for the passive training of lower extremity rehabilitation,the trainer with a constant speed driving the patient’s lower extremity to move in a circle was regarded as a single-input single-output position control system,with the target speed as the input and the actual speed as the output.In the process of rehabilitation training,the crank needs to maintain different target speed,and different users have different load interference due to the different length and weight of the leg.At the same time,because PMSM is a nonlinear system which is disturbed by various internal and external uncertainties,the system is required to have better robustness.There are inherent defects in the classical PID control,so this paper designs an active disturbance rejection controller which tracks and estimates the above interference factors in real time and compensates disturbance.The design scheme of transmission device,mechanical structure and control system is emphatically introduced.Firstly,the degree of freedom of lower limbs was reasonably simplified,and the rigid body dynamics model was established.The Lagrange energy method was used to establish the differential equation of lower limb dynamics,and the characteristics of lower limb acting torque and the maximum acting torque of lower limbs were solved.Aiming at the recovery training mode of the rehabilitation trainer,a constant speed control strategy based on the linear active disturbance rejection controller was proposed to effectively improve the system’s following performance to the instruction signal,and reduce the speed following error and speed fluctuation.Aiming at the exercise training mode of the rehabilitation trainer,an impedance control strategy based on intention recognition was proposed.The speed and pressure signals were collected to accurately identify the patient’s rehabilitation intention and ability,and the control instruction signals in line with the patient’s intention were output.Finally,the design and development of the hardware and software of the control system of the lower limb rehabilitation trainer are introduced.Using the C2000 series chip F28335 developed by TI company as the control center,the hardware circuit of the system is designed.According to the functional requirements of the control system of the lower limb rehabilitation trainer and the interruption mechanism of the control center,the motion control system,data acquisition system and communication system were designed respectively.The lower limb rehabilitation trainer experimental platform was built,and the recovery training mode experiment was completed by dynamometer-permanent magnet synchronous motor-lower limb rehabilitation trainer test system,so as to verify the feasibility,effectiveness and superiority of the control strategy proposed in this paper,as well as the effectiveness of each hardware and software functional module of the control system.