Position Control For A Two-joint Robot Finger System Driven By Pneumatic Artificial Muscles

Pneumatic artificial muscles,a pneumatic product developed by biomimetic research,is getting more and more attention in automatic field,especially used for robotic actuator due to its properties of simple structure,clean and high power/mass ratio.It is shown in relevant researches that a dexterous robotic hands equipped with pneumatic artificial muscles are not as heavy as ones with electronic motors.Moreover,the flexibility of pneumatic artificial muscles effectively protects users form interconnection harm.However,when it comes to the control of dexterous robotic hand,the compression of air,the flexibility of pneumatic artificial muscle' bladder,the coupling problem caused by the routine of tendons and nonlinearities of manipulator carry high nonlinearities and strong coupling problems.In order to deal with the difficulties mentioned above,following methods are proposed in this paper.In chapter I,the author proves the meaning of works in this paper by comprehensively considering relevant researches from both domestic works and international outcomes.Meanwhile,this chapter states the advantages and weaknesses of relevant researches on mechanical structures,tendon transformations and control methods.In chapter II,the mechanical design of dexterous robotic hand is discussed according to the anatomy structure of humans' arm and hand.Furthermore,the work principle and mathematic model of pneumatic artificial muscle are introduced.Inspired by the function of tendons,cables transformation routines are also proposed in this chapter.The experiment platform and traditional proportional integral derivative control method are introduced as well.The proposed two-joint dexterous robotic hand finger and pneumatic artificial muscles are assembled in the experiment platform.Moreover,the components of experiment platform are introduced individually in terms of model,function and usage introduction,according to the information flow sequence of close-loop of experiment.Meanwhile,the classical proportional integral derivative controller is proposed for the position control of two-joint dexterous robotic hand.The proportional integral derivative control is proposed as a comparative method for the methods introduced in following chapters.In chapter III,in order to tackle the high nonlinearities and strong coupling occurred in the position control process of two-joint dexterous robotic hand finger,an active disturbance rejection controller based on back-stepping method is proposed for the close loop control system.Meanwhile,a tracking differentiator is introduced to curb the overshoot phenomenon and an extended state observer is designed to estimate nonlinearities and coupling items.The experiment results demonstrate that the controller proposed in this chapter achieves a precise control performance.In chapter IV,back-stepping method is used for the controller design for high order system,the back-stepping controller proposed in last chapter has the disadvantage in parameter tuning and a complex structure.In order to solve the difficulties mentioned above,this chapter introduces a sliding mode controller based on extended state observer.Experiment and simulation results show that this controller can improve the tiny overshoot problem of the first joint,meanwhile,the controller guarantee the same control precision as active disturbance rejection controller does.In chapter V,the sliding mode controller introduced in chapter IV have the property to cause chatter phenomenon.In this chapter,an active disturbance rejection controller based on extended state observer is designed to tackle the problem aforementioned.This controller is easy to be understood and be coded.