Junpeng Shao

A compound control strategy combining velocity compensation with ADRC of electro-hydraulic position servo control system.

In order to enhance the anti-jamming ability of electro-hydraulic position servo control system at the same time improve the control precision of the system, a compound control strategy that combines velocity compensation with Active Disturbance Rejection Controller (ADRC) is proposed, and the working principle of the compound control strategy is given. ADRC controller is designed, and the extended state observer is used for observing internal parameters uncertainties and external disturbances, so that the disturbances of the system are suppressed effectively. Velocity compensation controller is designed and the compensation model is derived to further improve the positioning accuracy of the system and to achieve the velocity compensation without disturbance. The compound control strategy is verified by the simulation and experiment respectively, and the simulation and experimental results show that the electro-hydraulic position servo control system with ADRC controller can effectively inhibit the external disturbances, the precise positioning control is realized after introducing the velocity compensation controller, and verify that the compound control strategy is effective.

Model Identification and Control of Electro-hydraulic Position Servo System

In view of introduction of the composition and working principle of the electro-hydraulic position servo control system, the mathematical model of the system was built. In order to acquire more accuracy system mathematical model, System model identification and verification of electro-hydraulic position servo system were carried out based on hardware-in-the-loop simulation environment of Real-time Workshop (RTW) and system identification toolbox in MATLAB. A hybrid controller composed of a proportional controller, a fuzzy controller and a classical PID controller, for which the parameters of the PID controller can be adjusted online by using the fuzzy control rule, The zero position of fuzzy domain was regarded as the switching threshold, and stable switching is implemented between the proportional control and the proportion-fuzzy PID control. The simulation results show that the steady-state error of system is eliminated, the rapidity is enhanced by the hybrid control strategy, Moreover, and its ability of adapting to system parameter variation is superior to the other controllers.

Study of the electro-hydraulic load simulator based on double servo valve concurrent control

The superfluous force exists in the electro-hydraulic servo rudder load system, and seriously affects the dynamic load precision of the system. Meanwhile, the superfluous force makes the stability of the system bad, let frequency width dwindle, and reduces the load sensitivity of the system. Aiming at these questions and in order to improve the control performance of the load system of the electro-hydraulic load simulator, furthermore, for the sake of solving the superfluous force this technical problem caused by the forced flow, the author proposes the method of adopting the flow servo valve and the flow-press servo valve concurrent control the electro-hydraulic load simulator load system. This method makes the flow-press servo valve as a flow compensation tache, and changes the electro-hydraulic force servo system with strong position disturbance to the electro-hydraulic force servo system without disturbance. Then the author studies the electro-hydraulic force servo system on building its model, simulation and experiment and the result of the study shows that the superfluous force obviously decrease when the double valve concurrent control method adopted to the load system. At the same time, the dynamic load precision of the load system is obviously improved.

THE EFFECT OF OIL CAVITY DEPTH ON TEMPERATURE FIELD IN HEAVY HYDROSTATIC THRUST BEARING

For a heavy hydrostatic bearing with a high linear velocity, the results of numerical calculations often differ from practical conditions if the viscosity is considered as constant. In this article, the influence of the oil cavity depth on the temperature field in the heavy hydrostatic bearing is discussed in the context of variable viscosity. The viscosity-temperature relations for the gap oil film are first established by fitting B-Spline curves, then, numerical calculations for the temperature field in the heavy hydrostatic bearing of different oil cavity depths are carried out based on Finite Volume Method (FVM) under the same rotating speed, and the influence of the oil cavity depth on the temperature distribution in the gap oil film of the hydrostatic bearing is discussed. The results of numerical calculations provide the temperature distribution state inside the hydrostatic bearing, which would help the selection and the design of hydrostatic bearings in engineering practice.

Study of the Electro-hydraulic Load Simulator Based on Flow-Press Servo Valve and Flow Servo Valve Parallel Control

The superfluous force seriously affects the dynamic load precision of the electro-hydraulic load simulator. Aiming at this question, the work principle of the electro-hydraulic load simulator was analyzed, and the bond graph models of the flow servo valve, hydraulic cylinder and load were established. These models sufficiently contain the higher-order nonlinear dynamic character of the electro-hydraulic servo valve and describe the time variant character of the liquid capacitance of two cavities in hydraulic cylinder. Then the bond graph model of the electro-hydraulic load simulator system was established by combining the above bond graph models. In order to study the performance of the electro-hydraulic load simulator parallel controlled by the flow-press servo valve and the flow servo valve, and to study the effect of eliminating the superfluous force by this parallel control way, the structure and the working principle of the flow-press servo valve was analyzed, and the bond graph model of the electro-hydraulic load simulator parallel controlled by the flow-press servo valve and the flow servo valve was established. The simulation and experimentation study shows that the double servo valves parallel control method is very efficient to eliminate the superfluous force of the electro-hydraulic load simulator and is very obvious to improve the system performance of dynamic load. The study of simulation and experimentation also prove that the bond graph models are correct.

Hardware-in-the-loop simulation of electro-hydraulic pressure servo system

In order to improve the rigidity performance of the hydrostatic thrust bearing, an electro-hydraulic pressure servo system is proposed to adjust oil film pressure in real-time. A rapid prototyping method is adopted to identify the model of the pressure servo system. A non-linear hybrid controller is applied, which is composed of a classical PID controller and a fuzzy controller based on self-adjusting modifying factor and a fuzzy switching mode is employed to reject undesirable disturbances caused by the switchover between the two control methods. The identification model of the practical system and the feasibility of the control scheme are validated by hardware-in-the-loop simulation experiments. The experiments results show that the hybrid PID controller exhibits high bearing rigidity (the maximum overshoot is 0.07, while PID is 0.2), improves stability and rapidity when load changes. Further, the control performance can be enhanced through matching the load rigidity and mass reasonably; and it is feasible to apply electro-hydraulic pressure servo system to hydrostatic thrust bearing.

Research on the key technique of continuous rotary electro-hydraulic servo motor

The low speed performance is the most important indicators of the continuous rotary electro-hydraulic servo motor. The factors which influence the low speed performance consist of nonlinear characteristics such as structural pulsation, friction and leakage characteristic, oil distributing technique, pressure pulsation, servo valves distinguish ability and so on. In order to improve the low speed performance, the key technique of servo motor was studied. It is analyzed that velocity pulsation and torque pulsation was eliminated in the structure, the structure of blade and oil distributing plate was optimized for improving leakage and oil distributing characteristic, and friction torque was compensated in order to reducing the pulsation. These results can resolve the basic technique problem of the low speed performance and lay foundation for studying electro-hydraulic servo motor.

Research on the thermal deformation field of exhaust valve for high temperature steam booster pump based on ANSYS

Exhaust valve is a key component of the high temperature steam booster pump, whose structure has direct influence on the performances of the high temperature steam booster pump. In order to improve the performances of the pump from structural optimization design, a new type of exhaust valve is designed. The thermal deformation filed of the new type of exhaust valve is simulated by using ANSYS and compared with the thermal deformation field of the traditional exhaust valve. Simulation results show that the thermal deformation value of the new type of exhaust valve is smaller than the thermal deformation value of the traditional exhaust valve and satisfies the design requirement, which provides the valuable theoretical basis for the exhaust valve in the practical production and the performance improvement of the high temperature steam booster pump.

Influence of the Oil Cavity Depth on Dynamic Pressure Effect of Hydrostatic Thrust Bearing

The gap fluid of hydrostatic thrust bearing is studied in this dissertation. By applying computational fluid dynamics and theory of lubrication, and establishing three-dimensional solid model and mathematical model of the gap fluid of hydrostatic thrust bearing, analyzing synthetically three-dimensional pressure distribution of the gap fluid between hydrostatic guideway and the rotary table by using CFD software FLUENT, that reveals the law of the oil cavity depth affecting dynamic pressure effect of hydrostatic thrust bearing. The results show that dynamic pressure raises first and then declines with deepening of oil cavity when oil film thickness is given, dynamic pressure reaches extremely large value in some one oil cavity depth, and the value of oil cavity depth with the maximum bearing capacity is obtained. The results have an important directive significance for the optimization of hydrostatic bearing oil cavity.

Numerical Simulation of Integrated Deformation of Heavy Hydrostatic Thrust Bearing and Experimental Research

Aiming at the problem of deformation of heavy hydrostatic thrust bearing, finite element method (FEM) is used to conduct its numerical simulation, and the law of the influence of temperature and load on bearing deformation is revealed. Experiment of oil film thickness in different velocity is also made. The results demonstrate that: the free thermal deformation of workbench and base is significant. The thermal deformation can be counteracted by the pressure deformation partly in radial, which could improve deformation situation of workbench, the edge of deformed workbench becomes upper convex, the base becomes lower convex, and their whole deformation is a bugle-like from inside to outside., There is a nice coincidence between numerical simulation and experiment. Development cost can be economized significantly and the performance forecast of bearing can be realized. Furthermore, the theoretical basis and optimization direction for bearing design and calculation of its lubrication performance can be provided from this.