| The hydraulic legged robot has excellent carrying capacity,high working stability and strong environmental adaptability.It has great application value in material handling,emergency rescue and disaster relief and military special operations.In order to realize these applications,it is necessary to carry out good motion control of the robot.The driving performance of the joint drive unit determines the motion performance of the whole machine,and the hydraulic drive of the joint has many unfavorable factors such as strong nonlinearity,time-varying parameters and load variability.Therefore,if a control method with wide range and strong adaptability can be proposed for the hydraulic drive unit of the robot joint,it will be beneficial for the hydraulic legged robot to speed up out of the laboratory and accelerate the development process of industrial application.This paper aims to solve the problem of poor position control accuracy of robot joint hydraulic drive unit,and focuses on the following research work:(1)The time domain performance index and correction method of general third-order system are given.Because this paper simplifies the hydraulic system into a third-order system when studying the hydraulic system,and it is more convenient and intuitive to use the time-domain analysis method in engineering,but there are few time-domain analytical expressions for the third-order system in traditional teaching books,engineering manuals and academic papers.Therefore,this paper first converts the general third-order system from the frequency domain to the time domain,derives the time-domain performance index formula and verifies the accuracy.Finally,the corresponding correction methods are given for the two different working conditions of the system under no-load and interference.(2)A multi-loop fusion high-precision position control method for linear hydraulic system is established.On the basis of the linear hydraulic system,the feedback control(feedback loop),the position feed-forward control(position feed-forward loop)and the force feed-forward control(force feed-forward loop)are added to optimize the transient performance,position tracking accuracy and anti-interference performance of the system respectively,and the multi-loop fusion high-precision position control theory method of the joint hydraulic drive unit is formed.Finally,the problem of inconsistency between the linear hydraulic system and the experimental system is found.(3)Application of optimal control method in nonlinear hydraulic system.Through experiments,it is found that the variation law of the maximum overshoot in the linear hydraulic system is inconsistent with that in the experimental system.In view of this phenomenon,the reasons are analyzed and the feedback control adjustment method is proposed.Then,the applicability of feedforward control and feedforward control in nonlinear model is verified,and the application of multi-loop fusion control method in practical engineering is optimized.(4)The experimental verification of multi-loop fusion high-precision position control algorithm is carried out.In the case of the top cylinder test bench,the correctness and practicality of the theory of multi-loop fusion position control method of joint hydraulic drive unit under no-load and load-loaded working conditions are verified. |
