Research On Position Control Of Hydraulic Servo System With Uncertain Dynamics

The hydraulic position servo control system is widely used in high-precision position tracking of automatic devices such as vehicle active suspension and rolling mill.However,due to the strong nonlinear characteristics of the hydraulic servo systems itself,and the existence of time-varying load disturbances,measurement noise,internal parameter perturbations,inevitable modeling errors and other uncertain dynamics,which seriously affect the position tracking accuracy and anti-interference performance of the closed-loop system.Therefore,it is of great significance to design control schemes for the hydraulic servo systems with strong anti-interference ability and easy to implement in engineering.In this paper,the hydraulic position servo systems with uncertain dynamics is analyzed and studied.All the research contents of this article can be collected as follows:(1)The electric control system of the hydraulic servo experimental platform with single actuator is developed,including the system of software,hardware and upper computer interaction.The working principle of the hydraulic position servo systems is described,the characteristics of the system components are analyzed and the mechanism modeling is carried out,and the state space equation in strict feedback form is constructed by selecting reasonable state variables.(2)An adaptive gain control scheme based on equivalent sliding mode control is proposed.Firstly,the hydraulic servo systems is converted into Brunovsky standard type through coordinate transformation.Then,the adaptive switching gain is designed to suppress the chattering easily caused by the application of traditional sliding mode control in the hydraulic servo systems,while ensuring the fast convergence of the switching gain,without knowing the upper bound of the uncertain dynamics of the servo systems.Finally,the feasibility of the adaptive strategy for suppressing chattering in hydraulic servo systems is indicated by theoretical analysis and comparative simulation.(3)A low complexity control scheme with output transient steady-state performances limited is proposed based on backstepping control.Firstly,the output transient steady-state performances of the strict feedback model of the hydraulic servo systems is prescribed to achieve the performances limitation.Then the uncertain dynamics and virtual quantities in the servo systems are estimated by an unknown dynamic estimator which is easy to implement in engineering to solve the "differential explosion" problem.Finally,the feasibility of the control strategy for hydraulic servo systems is indicated by theoretical analysis and simulation results.(4)An adaptive control scheme with integral is proposed based on global no-approximation prescribed performance control.Firstly,for the Brunovsky standard of the hydraulic servo systems,the fast sliding mode differentiator is used to estimate the system acceleration.Then,by designing adaptive gains,the tracking process of the systems is not affected by the convergence of the performance functions and errors fluctuation,so as to solve the problem that the traditional prescribed performance control systems is prone to oscillate in the stable tracking stage when the performance boundaries of the errors is small,and at the same time,the integration of the converted errors is introduced to improve the anti-interference ability of the system.Finally,the feasibility of the control strategy for hydraulic servo systems is demonstrated by comparing the outcomes of experiment and simulation with traditional methods.