Study In Characteristics And Position Control Strategy Of Pneumatic Artificial Muscle

Pneumatic artificial muscle(PAM)is a new type of pneumatic driving element.Compared with traditional hydraulic cylinder,cylinder,motor and other drivers,it has advantages of high power/mass ratio,safety,environmental protection and good flexibility.It can be widely used in industry,agriculture,military,medical and other fields.Taking PAM-driven medical rehabilitation robot as an example,it can avoid secondary injury to patients in the process of rehabilitation treatment.Therefore,the study of PAM has very important social and economic value.Firstly,two main methods of PAM static characteristic modeling are analyzed,that is,theoretical modeling and experimental data fitting modeling.According to the thermodynamic theorem,the mass flow equation of PAM and the mathematical model of gas passing through the solenoid valve body in the process of inflating and exhausting are obtained.According to the variables needed to establish the static model,the PAM performance test platform was designed,including the selection of main components and the design of electrical control program.The isobaric characteristic experiment of PAM is carried out.The static mathematical model is obtained by non-linear fitting in OriginPro.Then the model is verified by isobaric experiment.High-speed on-off valve and pulse width modulation are used to control the position of PAM through the flow rate of the valve body.The PAM position control system is analyzed and the mathematical model of the system is established.The static and dynamic characteristics of PAM and the correctness of the system model are verified by comparing the step response experiment of the system with the simulation output curve.Finally,aiming at the non-linear characteristics of PAM position control system,the active disturbance rejection controller(ADRC)and PID controllers are designed on the experimental platform by programming,and a series of comparative experiments are carried out.The experimental results show that the ADRC established in this paper has better dynamic performance than the traditional PID controller.The response is smooth,fast,no overshoot,no obvious time delay,and the tracking accuracy of the dynamic signal meets the requirements of Engineering application.