Model Of Hydraulic Servo System Research Articles

Trajectory Tracking and Control Algorithm for Precision Parallel Robot

When the state of the robot reaches the smooth sliding plane, the current algorithm will generate high-frequency chattering, resulting in larger tracking error and longer response time. To solve these problems, we have proposed a trajectory tracking and control algorithm based on exponential reaching rate. The coordinate system of parallel robot system is established, and the kinetic energy and potential energy of the system are calculated. The results are brought into the Lagarnge equation to find the dynamic model of the system. The power amplifier, electro-hydraulic servo valve, hydraulic cylinder and its load are taken as generalized controlled objects, and the hydraulic servo system model is established. The exponential approaching rate is introduced to design the dynamics model and the trajectory tracking sliding controller of the hydraulic servo system model. By adjusting the upper and lower bounds of the external disturbance of the controller, the control rate is changed, the buffeting occurrence is reduced, and the response time is shortened, to realize the low error tracking of any trajectory of the robot. The experimental results show that the trajectory of the robot can be adjusted quickly and the desired trajectory is better tracked by the end.

Modeling and identification of hydraulic servo systems

The goal of this research is to implement a nonlinear simulation model of hydraulic servo system (HSS).The model is based on physical laws as well as experimental identification of piston position. It also presents the tuning of PID/PI controller’s parameters using particle swarm optimization technique. The mathematical model includes the most nonlinear effects that are involved in the hydraulic system under study. The dynamics of hydraulic systems are highly nonlinear due to directional change of valve opening, friction forces, and oil compressibility. The model describes the behavior of a servo system BOSCH REXROTH servo valve (4WRSE). It has been developed using MATLAB/SIMULINK. The main objective of the simulation modeling and system identification for electro-hydraulic servo valve is to obtain good performance of its dynamic and nonlinear behavior. The identified model has been found to be a third-order continuous time model. The identification of HSS is performed by using System Identification Toolbox of MATLAB. The obtained results are promising and satisfactory. In addition, the simulation and experimental results have shown the superiority of using PID controller type for requirement of minimum settling time and the PI controller type for minimum value of percentage overshoot.

Practical behavior of advanced non-linear hydraulic servo system model for a mold oscillating mechanism depending on line volume

We studied a mold oscillating mechanism for continuous casting. An equivalent hydraulic servo system model was established including a non-linear property and line volume near the hydraulic cylinder. The analysis focused on a practical behavior of the system. To observe an oscillated object and dynamic responses, an equivalent stiffness, damping ratio and simple mass-damper-spring 1-DOF model were established by Karl-Erik Rydberg’s research, and showed hydraulic cylinder pressure and line volume near the hydraulic cylinder. Especially, hydraulic pressure including statue of a mechanical and hydraulic cylinder was analyzed in the time and frequency domain. The results were validated by comparing responses between the 1-DOF model and the nonlinear hydraulic servo system model. The line volume that connects the hydraulic cylinder and the hydraulic servo valve has great effect on damping ratio and natural frequency of the hydraulic servo system. When the line pipe has high volume compared to normal statue, the hydraulic cylinder pressure has sharp peak frequencies that are located on natural frequency and its duple-harmonic terms with sideband peaks; (±2×exciting frequency) space. Based on this fact, we investigated the model using sensitivity analysis, and explained an oscillating mechanism about the mold oscillator by applying additional spring. A design of robust control for the mold oscillator was suggested by Negative strip time criterion, and maximum additional spring stiffness was shown.

Simulation of Hydraulic Servo System Based on Dynamic Monitoring in Mechanical Engineering

Sensor system of the belt conveyor is designed, then corrective and alarm command is given. According to the signal of real-time monitoring, belt deviation state is determined, and roller axis position is adjusted in order to achieve the purpose of deviation – adjusting. Based on dynamic monitoring of the belt conveyor, corrective devices are constructed, and hydraulic servo system model is designed by Matlab software in this paper, then the stability of the system is analyzed.

Coupling Dynamic Model and Control of Chatter in Cold Rolling

The dynamic model of 4-h mill, which couples with the rolling process model, the mill roll stand structure model, and the hydraulic servo system model, is built by analyzing the vibration process of cold rolling. By linearization, the multiple input multiple output linear transfer function matrix model of single stand 4-h cold mill system is obtained. With the consideration of strip quality, the model of strip thickness control system is established in a simplified form. Meanwhile, the robust controller based on quantitative feedback theory is designed for the gauge control model. A comparison with PID controller shows that the controller has better disturbance attenuation performance for parameter uncertainty and external disturbance.

Coupling Dynamic Model of Chatter for Cold Rolling

Abstract In order to build high accuracy integral dynamic models of cold rolling mill system, by analyzing the vibration process of cold rolling, the dynamic model of 4-h mill, including the rolling process model, the mill roll stand structure model and the hydraulic servo system model is built. These three models are coupled and linearized, then the multiple input and multiple output (MIMO) linear transfer function model of single stand 4-h cold mill system is obtained. The model with the proposed data proves its validity, meanwhile the effects of different working conditions on the stability of cold rolling mill system have been discussed. Simulation resulsts show that the model accords with former models and has its own advancement. It contributes to the further study and supression of coupling vibraiton.

Dynamic model building of thickness control system for four-high rolling mill and HCO∞ robust controller design

In this paper, the integral dynamic model of four-high mill is built which includes the rolling process model, the dynamic model of mill stand-rolls and the dynamic model of hydraulic servo system. The three models are coupled and linearised, the MIMO transfer function of four-high mill system is obtained. Considering the quality of the product, the MIMO model is simplified and the thickness control system based on thickness gauge is derived. The H∞ robust controller is designed for the thickness control system based on the mixed sensitivity robust control theory. The weighting functions are selected based on genetic algorithm. Simulation results and comparison with the effect of PI controller show that the robust controller designed has better disturbance attenuation performance for parameter uncertainty and external disturbance. The dynamics performances and stability of the thickness control system based on thickness gauge are improved significantly.

Dynamic Modeling of Gauge Control System Based on Thickness Gauge and Design of H∞ Robust Controller

In order to build high accuracy integral dynamic models of rolling mill system, apply advanced control theory in the traditional rolling field and improve the quality and precision of strip, dynamic model of gauge control system of 4-h mill is built, including the rolling process model, the mill stand-rolls dynamic model and the hydraulic servo system model. The three models are coupled and linearized, then the multiple input multiple output (MIMO) linear transfer function model of 4-h mill system is obtained. Simplify the MIMO linear model, considering the quality of the product, the plate thickness control system based on thickness gauge monitoring is obtained. The H∞ robust controller is designed by using the H∞ mixed sensitivity robust control theory. The weight functions are selected based on genetic algorithm. Simulation results and comparison with the effect of proportional integral derivative (PID) control show that the H∞ robust controller designed has better disturbance attenuation performance for parameter uncertainty and external disturbance. The dynamic performances and stability of the thickness control system are improved significantly.