Yuhong Dong

Bio: Yuhong Dong is an academic researcher from Harbin University of Science and Technology. The author has contributed to research in topics: Servo & Fuzzy control system. The author has an hindex of 3, co-authored 5 publications receiving 17 citations.

Hardware-in-the-loop simulation on controllable hydrostatic thrust bearing

Abstract: In the hydrostatic thrust bearing with open-loop quantity oil supply system for the heavy NC machine tool, the time-variable oil viscosity and the loads will cause the lubricant film thickness deviating from the optimum value, which reduce the bearing film rigidity and affect the machine tool precision. This paper proposed a controllable hydrostatic thrust bearing, which combined the constant flow chambers and the controllable flow chambers. The chamber flow can be adjusted automatically according to the load, the cutting force, and the thermal results of thrust bearing. The controllable chamber flow was adjusted by the electro-hydraulic servo variable mechanism. The oil film thickness error was measured in real time to maintain the most optimum film thickness. The models of controllable chamber flow and servo variable mechanism were established, and the model identification experiments for servo variable mechanism were carried on. The hardware-in-loop simulation results show that the controllable bearings assure the stability and rapidity of system, compensate effectively the effect of load parameter on oil film thickness, and improve the position tracking performance, and validate the creditability of the identification model.

Control Method of Heavy Hydrostatic Thrust Bearing

Abstract: A hybrid fuzzy control scheme was applied to improve the rigidity of hydrostatic thrust bearing. The bearing oil film control was realized by coupling oil film thickness of four controllable chambers. The chamber flow can be regulated by electro hydraulic servo valve-control variable pump according to the surface roughness, load, cutting force, and thermal effects of worktable. The nonlinear hybrid controller developed was composed of a classical PID controller and a fuzzy controller based on self-adjusting modifying factor, and feed-forward compensation was added. A fuzzy switching mode was employed to avoid the undesirable disturbances caused by the switchover between the two control methods. By simulations and experiments on an electro-hydraulic servo test bench the feasibility of the control scheme was validated by comparison with a PID and a conventional fuzzy control. The research results show that the hybrid fuzzy controller exhibit good dynamic and steady quality, eliminate oil film lubrication failure and be broadly applied in high precision heavy machine tool.

Model Identification and Control Method Study on Electro-Hydraulic Pressure Servo System

Abstract: Mathematic model of electro-hydraulic pressure servo test bench was obtained based on xPC technique. In order to improve the tracking performance of the pressure servo system a new nonlinear hybrid controller was developed according to the mathematic model, which composed of a classical PID controller and a fuzzy controller based on self-adjusting modifying factor. And interpolation method was used in the modifying factor fuzzy number model; a fuzzy switching mode was employed to avoid the undesirable disturbances caused by the switchover between the two control methods. The hardware-in-the-loop simulation results show that the problems of steady-state error for fuzzy control and rapidity for PID control are solved, and the comprehensive performance of electrohydraulic pressure servo is enhanced when load rigidity and mass changed.

Hardware-in-loop simulation on hydrostatic thrust bearing worktable pose

Abstract: A controllable hydrostatic thrust bearing was presented to improve rigidity. The bearing worktable poses were controlled by coupling oilfilm thickness of four controllable chambers. The chamber flow can be regulated by electro hydraulic servo valve-control variable pump according to the surface roughness, load, cutting force, and thermal effects of worktable. The mathematical models of the controllable chamber flow, servo variable mechanism and controller were built. The pose control model was established, which contained the kinematics positive and negative solution and control strategy of feedforward and hydraulic cylinder position feedback. Hardware-in-loop simulation experiment was carried out on the electro hydraulic servo test bench by means of the non-linear relation of film thickness and hydraulic cylinder displacement. Hardware-in-loop simulation experiment results show that the controllable bearings exhibit high oilfilm rigidity, the rising time is 0.24 s and the maximum overshoot is 2.23%, and can be applied in high precision heavy machine tool.

Hardware-in-the-loop Simulation of Electro-hydraulic Driving Force Servo System

Abstract: A hydraulic servo system has nonlinearity and uncertain dynamics, so its theoretical mathematical model can't sufficiently represent the practical system. The identification experiments were carried out in hardware-in-the-loop simulation environment and the identification model was acquired. In order to improve the tracking performance of the force servo system a new nonlinear hybrid controller was developed composed of a classical PID controller and a fuzzy controller based on self-adjusting modifying factor, which was added feedforward compensation. A fuzzy switching mode was employed to avoid the undesirable disturbances caused by the switchover between the two control methods. By simulations and experiments on an electro-hydraulic servo test bench the feasibility of the control scheme was validated by comparison with a PID and a conventional fuzzy control. The research results show that the hybrid PID controller improves stability and rapidity when load rigidity and mass changed, and has good performances in real time applications.

A hydraulic control system

Abstract: A hydraulic control system for controlling at least one load (1; 30, 40), the respective load pressure as a load-sensing signal via a respective load-sensing line (LS - that as a means for influencing a load-sensing signal, a compensator (10) is present, a corrected load sensing signal (LS - that the compensator (10) consists of a compensation valve (11) and a shut-off valve (12), - that the compensation valve (11) comprises a pressure applied to it load-sensing pressure (p - that the shut-off valve (12) shuts the compensator (10) when at the compensation valve (11) pending load-sensing pressure (p

Study of Fuzzy PID Controller for Industrial Steam Turbine Governing System

Abstract: Since the electric and the heat load of the stream turbine always have uncertain factors,the simple linear or nonlinear differential equations can not sufficiently represent corresponding practical system.And therefore many conventional control methods based on mathematical models are limited.The main purpose of this study attempts to develop a nonlinear fuzzy PID controller adopting fuzzy rule and inference to adjust PID parameters on-line.The proposed fuzzy controller improves dynamic performance of control system greatly and shows excellent robustness against variations of system parameters and external disturbances by comparison with a PID and a fixed fuzzy control.

Recess Design and Dynamic Control of an Active Compensating Hydrostatic Bearing

Abstract: This paper describes the optimum design of recess shape for the proposed hydrostatic bearing, and dynamic control of oil film thickness for an active compensating hydrostatic bearing by using a servo valve and a proposed controller. First of all, this study is theoretical study concerning static performance of a hydrostatic bearing having recess of optimal shape parameters. Because of the recess of the traditional hydrostatic bearing only has one oil outlet that is easy to concentrate the pressure of the recess at the outlet, leading to non-uniform pressure distribution. Hence, the objectives of this study are to design a hydrostatic bearing with high load capacity, high stiffness, low flow rate and uniform pressure distribution by using HTGA/Gray optimal approach. In addition, this study integrates servo control technology to compensate the pressure of the bearing with an intelligent nonlinear controller to maintain a constant oil film thickness. However, the hydrostatic bearing is a nonlinear system and is affected by numerous uncertainties; that is, the parameters can be changed by factors, such as temperature, leakage, and disturbance. Therefore, the proposed controller proposes a self-tuning mechanism to modify the output scaling factor, and adds a dead zone compensator to avoid the insensitive area of a servo valve. Finally, the experimental results are used to verify the feasibility and practicality of this study.

Guiados lubricados activos para máquinas herramienta de precisión basados en fluidos magnéticos y válvulas adaptativas

Abstract: El trabajo de investigacion que se presenta en esta memoria ha tenido como objetivo avanzar en el conocimiento de guiados lubricados presurizados, tanto hidrostaticos, hidrodinamicos como en regimen hibrido. Se ha trabajado con fluidos convencionales y con fluidos magneticos, lograndose en ambos casos prestaciones mejoradas con respecto a soluciones pasivas convencionales, y una respuesta activa avanzada.En el desarrollo de lubricacion basada aceites minerales convencionales, fluidos Newtonianos, se ha realizado una herramienta de calculo con la que predecir el comportamiento de cojinetes radiales, axiales y guiados lineales; todo ello orientado a su uso durante la fase de diseno de maquinas herramienta. Los modelos se han validado mediante un nuevo banco de ensayos donde analizar los prototipos de cojinetes radiales. El nuevo banco de ensayos ha servido para aislar el comportamiento del cojinete radial a analizar con respecto al resto del sistema, efecto que en los bancos de ensayos clasicos limita su caracterizacion. Para finalizar con las soluciones de lubricacion mediante fluidos convencionales se ha desarrollado una valvula adaptativa en base a diafragmas flexibles; y por otro lado, una solucion de lubricacion autocompensada basada en conductos internos en el propio guiado. Estos desarrollos han sido tanto teoricos, en base a modelos de fluidodinamica, como experimentales, con sendos bancos de ensayos.El siguiente gran bloque de la investigacion presentada en esta memoria se orienta al uso de fluidos magneticos para la obtencion de lubricacion activa. Se ha trabajado con fluidos magnetoreologicos y ferrofluidos, donde tras realizar una actividad de sintesis para adquirir un conocimiento basico sobre su composicion, se ha realizado una caracterizacion experimental en profundidad de dos fluidos comerciales; los dos fluidos que se han utilizado durante la investigacion. Se ha desarrollado un modelo teorico apoyado con su respectivo banco de ensayos para el estudio de cojinetes radiales, tanto hidrodinamicos como hidrostaticos. Para estos ultimos se han desarrollado tambien valvulas magnetoreologicas con las que controlar el caudal de alimentacion. En esta investigacion se ha comprobado la mejora de la linealidad en la lubricacion hidrodinamica, asi como la rigidez infinita con las valvulas magnetoreologicas controladas en lazo cerrado. Finalmente se ha desarrollado una junta de estanqueidad basada en fluidos magneticos, donde los ferrofluidos han demostrado un comportamiento compatible con los requerimientos de cabezales de maquinas herramienta de precision.

Preview Control of Hydrostatic Guideway for Ultraprecision CNC Machine Tools

Abstract: An active preview control strategy is presented to suppress the vibration of hydrostatic guideway under dynamic machining force. A state space model of closed hydrostatic guideway system is built, and the predictability of machining force during cutting process is analyzed. Numerical simulation model of preview compensation control systems is established. The displacements of slide carriage are compared under the condition of no control, optimal control and active preview control. The variations of oil recess pressure are observed when using the two latter control methods. The results show that maximum displacement of slide carriage by using active preview control method reduces 73.3% compared to the optimal control method, and reduces 94.1% compared to the method without any control. Besides, the compliance of the oil recess pressure to machining force is improved by 23%. Finally, an experiment evaluating the displacement of slide carriage and variation of oil recess pressure is carried out and the numerical predictions agree with the experimental results. It is effective to control machining vibration of hydrostatic guideway by using active preview control strategy.