• Journal of Institute of Control, Robotics and Systems
• /
• v.9 no.2
• /
• pp.124-130
• /
• 2003

The electro-hydraulic servo system with a servo valve is applied widely in force control. However, the composition of control system using a servo valve is difficult due to nonlinearities in the servo valve, such as square-root terms in flow equation. The electro-hydraulic servo system using a DDV(Direct Drive Valve) instead of a servo valve was proposed and it's characteristics was estimated. The DDV and whole system are modelled by parameter identification using the input-and-output data, then the models are verified by the comparison of simulation with experiment. Also, the state feedback controller has been designed based on this model, then the performance of the electro-hydraulic force servo system using a DDV is evaluated by simulation and experimental results.

• Journal of the Korean Society for Precision Engineering
• /
• v.17 no.2
• /
• pp.151-160
• /
• 2000

An experimental and theoretical analysis for the improvement of dynamic characteristics and design of electro-hydraulic flow control servo valve are performed. The theoretical results are compared with the experimental step responses, and the important design parameters of an electro-hydraulic flow control servo valve are derived by using the simulation program. Simulation parameters of nozzle jet coefficient and orifice and spool valve discharge coefficient are given through experiment. The theoretical and experimental step response curves show that the valve gain depends on the fixed orifice and nozzle $ratio(R_on)$ and is maximum at $R_on=1.$ And drain orifice in the flapper - nozzle return line creates a small back pressure, which improves the performance fur the valve.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.10a
• /
• pp.710-714
• /
• 2005

A dynamical analysis and PID control of a compressed gas expulsion system is performed. The purpose of this study is to develop a compressed gas discharging system and to verify the validity of the system. The electro-hydraulic servo valve is modeled as a 3th order transfer function to calculate flow force affecting expulsion valve is significantly considered. The friction force in the expulsion valve is considered as a nonliner model of stribeck effect. The dynamic characteristics of this system is examined by the computer simulation. The position control of the expulsion valve is performed by PID controller.

• International Journal of Fluid Machinery and Systems
• /
• v.8 no.4
• /
• pp.318-326
• /
• 2015

A valve-less electro-hydraulic servo steering device (short: VSSD) for ships was chosen as a study object, and its mathematic model of hydraulic shock was established on the basis of flow properties and force balance of each component. The influence of system structure parameters, changing rate of motor speed and external load on hydraulic shock strength was simulated by the method of numerical simulation. Experiment was designed to test the hydraulic shock mathematic model of VSSD. Experiment results verified the correctness of the model, and the model provided a correct theoretical method for the calculation and control of hydraulic shock of valve-less electro-hydraulic servo steering device.

• Transactions of The Korea Fluid Power Systems Society
• /
• v.1 no.3
• /
• pp.14-19
• /
• 2004

The Direct Drive Valve used in this study contains a pressure-feedback-loop in itself, then it can eliminate nonlinearity such as the square-root-term in flow rate calculation and the change of bulk modulus of hydraulic oil. In this study, assuming that the dynamic characteristic of the DDV is modelled as a first order lag system, an parameter identification method using the input data and the output data is applied to obtain DDV's mathematical model. Then, a state feedback controller was designed to implement the force control of hydraulic system, and the control performance was evaluated.

• 제어로봇시스템학회:학술대회논문집
• /
• 2001.10a
• /
• pp.169.1-169
• /
• 2001

In general, for high performance pressure control system, hydraulic system with electo hydraulic servo valve controls flow rate, it contains many nonlinear term like square-root and change of bulk modulus by flow rate. But, DDV(Direct Drive Valve) contains pressure control loop itself, then it can eliminate nonlinearity and achieve linearity for hydraulic system. In this paper, parameter identification method which uses input and ouput data is applied to obtain DDV's mathematical model and parameter assuming that dynamic characteristic of DDV is first order system. Then, the state feedback controller was designed to implement the force control of hydraulic system , and the control performance was evaluated.

• Journal of Institute of Control, Robotics and Systems
• /
• v.15 no.6
• /
• pp.567-572
• /
• 2009

The underwater launch system using an ATP consists of five parts: compressor tank, proportional flow control servo valve, expulsion spool valve, air turbine pump, and discharge tube. The purpose of this study is to develop an underwater launch system using an ATP and to verify the validity of the system. The proportional flow control servo valve is modeled as a 2nd order transfer function. The projectile is ejected by pressurized water through the air turbine pump, which is controlled by expulsion valve. The mathematical model is derived to estimate the dynamic characteristics of the system, and the important design parameters are derived by using simulations. The computer simulation results show the dynamic characteristics and the possibility of control for underwater launch system.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 1999.10a
• /
• pp.371-374
• /
• 1999

This paper present the nonlinear control and the Lyapunov analysis of the nonlinear electro-hydraulic system for steering control of UCT. Electro-hydraulic system itself has the high nonlinearities arisen from the nonlinear characteristics of the pressure-fluid flow in valve and friction in cylinder. These nonlinearities are unmodeled terms in the transfer function. This paper presents the system modeling, analysis of stability based on the Lyapunov function and simulation of the nonlinear hydraulic servo system.

• Journal of Advanced Marine Engineering and Technology
• /
• v.17 no.1
• /
• pp.26-32
• /
• 1993

The loads exerted on electro-hydraulic servo system are classified into inertial, viscous, and spring load. The additional load called disturbances is also exerted on system but is generally not modeled. To deal with these kinds of loads, it is necessary to maintain the continuous signal transfer, so we can construct compensator to satisfy control specifications using feedback signal such as displacement, velocity, acceleration and pressure known as state variables. In case of controlling the speed of hydraulic motor, we must keep up robust performance for the various loads and disturbances acted on the system. However, the load flow rate in the valve is characterized by nonlinearity so that traditional theory of linear control could not be expected to give the desired performance. In this paper, it is shown that speed controller of hydraulic motor gives a good command following and disturbance rejection performance by applying sliding mode theory as a way of robust control to the nonlinearity, variation of loads and disturbances.

• Journal of Biosystems Engineering
• /
• v.17 no.1
• /
• pp.18-26
• /
• 1992

A mechanical-hydraulic hitch control system has been adapted to most agricultural tractors. But it has various defects due to friction, inertia and hysteresis. Recently a number of electronic-hydraulic hitch control systems have been developed in several countries to improve control performance of the agricultural tractors equipped with a mechanical-hydraulic hitch control system. This study was conducted to develop a new electronic-hydraulic hitch control system using an electro-hydraulic servo valve instead of an on-off valve and to carry out computer simulation of the system. According to the result of computer simulation, the control system showed the best performance when the proportional constants were 9 and 4 for position and draft control respectively. The step and frequency responses were improved as flow rate increased.