Huayong Yang

Self-tuning-parameter fuzzy PID temperature control in a large hydraulic system

Oil temperature control in a large hydraulic system is dealt with using the fuzzy logic control algorithm. Mathematic model of the control system characterized by large time delay is created based on law of thermodynamics. A self-tuning-parameter fuzzy PID controller is designed to regulate the cooling water flow rate through the triple proportional valve in order to control the oil temperature. The simulations and experiments are carried out, making a comparison with conventional PID control. The results suggest that fuzzy PID strategy can efficiently improve the performance of the hydraulic temperature control system, irrespective of time delay problem and parameter variations. It achieves higher control accuracy of temperature, faster response and stronger robustness than conventional PID control system.

Control of bulk modulus of oil in hydraulic systems

In view of requirements for better position accuracy, response time and stability of hydraulic system, it is more important than ever to pay attention to bulk modulus of hydraulic oil. In this paper, the effects of the bulk modulus of hydraulic oil on system performance and the entrapped air on bulk modulus have been analyzed. A method of online vacuum degassing in a sealed system has been used to increase the effective bulk modulus of hydraulic oil, and a device has been developed to measure oil bulk modulus online. The experimental results show that the bulk modulus of hydraulic oil can be controlled in real system effectively by the method mentioned above.

Modeling of separate meter in and Separate Meter out control system

The schematic of Separate Meter In and Separate Meter Out (SMISMO) Control system is introduced first, nonlinear simulation model is built for SMISMO Control system, parameters of simulation model are verified by experiment. The flow rate through the SMISMO valve at low pressure differential is not tested in detail before, through introducing extra variable area orifices to fit the measured valve flow rate and pressure differential data, the flow rate through SMISMO control valve at low pressure differential can be estimated more accurately. The cylinder friction indirectly measured by experiment is used to improve the friction model parameters. Comparison of simulation model with real system has been carried out in open loop test. The verified simulation model have captured the essential characteristics of real system, the whole model is used for testing the proposed controller of SMISMO control system, simulation shows the speed of piston in the cylinder and rod side pressure of the cylinder can be both controlled to achieve velocity control and energy saving characteristic of SMISMO control system. Its another way to realize cylinder speed control of SMISMO control system without using piston velocity transducer.

Simulation of Separate Meter In and Separate Meter Out Valve Arrangement used for synchronized control of two cylinders

Separate Meter In and Separate Meter Out Valve Arrangement (SMISMOVA) possesses more degree of freedom than the conventional Proportional Directional Valve (PDV) control system. So the controller can be designed to take the advantage of this extra characteristic. In this paper, the SMIMOVA configuration is introduced first, and the simulation model is then built, the two layer controller is also designed for giving the control signal to the selected valves in corresponding work mode. Two typical work modes are selected to compare control performance and energy saving characteristic of SMIMOVA control system with PDV control system in Synchronized motion control of the two cylinder. Simulation shows that SMIMOVA can achieve faster time response and better energy saving characteristic than the PDV control system with the proposed two layer flow rate and pressure controller.

Calculation force control based on linearization feedback model of separate meter in and separate meter out control system

The components and work principle of Separate Meter In and Separate Meter Out(SMISMO) load sensing control system are introduced. In the novel system, the traditional proportional valve is replaced by the Separate Meter In and Separate Meter Out valve element which is used to control velocity of piston in the asymmetric cylinder. Nonlinear simulation model of the novel system is built to study the trajectory tracking performance, Linearization Feedback technology is used to linearization the nonlinear system, Calculation Force Control strategies is used for trajectory tracking, simulation and experiment show the tracking performance is good, and the controller is better than pid control strategy, it is promising for industrial application.

Pressure and speed control of electro-hydraulic drive for shield tunneling machine

This paper presents an electro-hydraulic control system for shield thrust drive. The control model of thrust system is developed. A pressure and flow compound control approach is applied using the pressure and flow rate feedback to design an outer loop controller and an inner loop controller to address the control problem encountered in thrust, cooperating with the pressure relief valve and the flow control valve. Simulation and field application results are presented to verify the effectiveness and rationality of the proposed drive system and its control approach.

Piezoelectric actuators for screw-in cartridge valves

Research has been undertaken to explore the possibility of using smart materials for the actuation of screw-in cartridge valves. Four types were considered and a piezoelectric (PZT) stack was selected as the most appropriate actuator. The concept of a spool valve piloted by a PZT valve was chosen for investigation. A mathematical model of a hydraulic system with a spool valve piloted by a PZT valve is developed and the results obtained from simulation studies are assessed. Experimental tests were undertaken using a prototype PZT valve. The test results obtained confirm that the PZT valve was able to switch a high flow spool valve and the results show similar trends to those obtained from the simulations. Although effective, the current cost of the PZT valve is much higher than that of a conventional solenoid valve that it may one day replace. There are also issues to be addressed that relate top temperature dependence of the PZT valve operation. A solution is given to improve the response of the spool.

New strategy of nonlinear PD controller for hydraulic force system under large variation of load stiffness

A nonlinear PD controller is developed in new strategy to keep acceptable performance of an electro-hydraulic force system in the condition of large variation of stiffness and load. The controller uses two nonlinear tracking differentiators to obtain high quality differential signals. New approach is adopted to build the nonlinear gain functions and experiential formulas are given to determine the range of the gains. Simulation contrast shown that the performance of new functions is better than original. The experimental results indicate that high performance can be guaranteed and the control algorithm is simple to realize in engineering.

Research on Two Key Technologies of Improving Dynamic Quality of Hydraulic System With High Flow

The demand of hydraulic parallel motion system of space rendezvous and docking simulator to its hydraulic system is high flow and high performance. To achieve good motion simulation results and meet the requirements of precision control, a method of self-tuning parameters fuzzy PID control of proportional water valve opening has been employed to control oil temperature, a method of online vacuum degassing in a sealed system has been used to increase oil effective bulk modulus, and a device has been developed to measure oil bulk modulus online. Experimental research has been carried out on the hydraulic driving system of comprehensive test bed for docking mechanism. The experimental results show that precise control of oil temperature has been achieved and bulk modulus of oil has been increased obviously.Copyright