Shigeru Ikeo

Robust Control of Water Hydraulic Servo Motor System Using Sliding Mode Control with Disturbance Observer

With the recent increased concerns for global environmental problems, the water hydraulic technique using pure tap water as a pressure medium has become a new drive source comparable to electric, oil hydraulic and pneumatic drive systems. However, the main problems for precise control in a water hydraulic servo motor system are steady state errors and overshoot due to its large friction torque in the low velocity range of a motor. In this research, the sliding mode control combined with the disturbance observer is applied to control the rotational angle of a water hydraulic servo motor. We examined the rotational angle control performances with these methods for load fluctuations

The application of simple adaptive control for simulated water hydraulic servo motor system

Because of the serious situation of environmental pollution all over the world, the water hydraulic technique using pure tap water as a pressure medium has become new drive source comparable to electric, oil hydraulic, and pneumatic drive systems. Furthermore, water hydraulics is also preferred because of its high power density, clean, high safety against fire hazards, and easy availability. However, the main problems for precise control in water hydraulic systems are steady state errors and overshoot due to its large friction torque and considerable leakage flow. In this study, a simple adaptive control (SAC) algorithm that is appropriate for dealing with these problems will be applied to a water hydraulic servo motor system for both angle and velocity controls. SAC also has simple, lower order structure, and few adaptive parameters; thus, it is high feasibility in real applications. For both angle and velocity controls using SAC, the tracking performances are good in simulation: 0.08 degree and almost 0 revolution per minute (min-1) for angle and velocity controls, respectively. The controllers also can highly attenuate the effects of disturbances.

Application of Invariant Turbulence Modeling of the Density Gradient Correlation in the Phase Change Model for Steam Generators

Predictions of the amount of steam generated on evaporation plates are mostly done by empirical algebraic models or semi-algebraic one equation models. However, the accuracy of the methods fully depends on the equipment and the environment. A new method that directly installs the phase change model into the system of fluid dynamics equations is studied for improvement. First, a turbulence model for the phase field model below the boiling point or near the boiling point is constructed. The model consists of the density gradient correlations, which are shown in the set of the phase field equation (C-H equation). The density gradient correlation is obtained with the Reynolds decomposition from the compressible continuity equation. Second, to import the effect of viscosity, the pseudo stress tensor in the momentum equation is modified in a semi-direct simulation, which covers mainly large eddies on coarse grids. A steam generator is modeled with a three-layer problem: the water layer, the humid air layer, and the environmental boundary in nearly homogeneous turbulence with strong acoustical disturbances, which are common in the multi-phase flows in pipes. The density gradient correlation equation is closed by the invariant modeling technique with many unknown constants. In the present work, one constant appearing in the invariant model is determined theoretically. The set of equations allows stable computations during prediction for the steam generator.

PID control performance of a water hydraulic servomotor system

In recent years water has been increasing used as a working fluid again, due to the global environmental problems. In this paper we develop the water hydraulic servo system by combining a servo valve and a hydraulic motor, and study the control performance of rotational angle. The problem encountered in the system is the existence of unmodeled dynamics, e.g., a large starting torque and friction force of water hydraulic servomotor, which cause the significant performance degradation. We composed the gain scheduled PID-controller that improves the large steady state error and overshoot. We have succeeded, to large extent, in attenuating the steady state error of the water hydraulic servomotor.

Energy efficiency of water hydraulic FST, PMT, and servo motor system

Low energy efficiency and high installed cost are the two main problems that prevent water hydraulics to be popular in application. This research introduces two novel systems: water hydraulic fluid switching transmission (FST) and pump motor transmission (PMT) that only use cheap ON/OFF valves for lessening the initial cost and reducing the energy consumption; beside, this paper also introduces a conventional servo motor system (SMS) for comparison. Moreover, both FST and PMT systems can recover the kinetic energy of a flywheel in a deceleration process and store it into an accumulator for using in the next working cycle. The experimental results show that the FST system only need from 33.2 to 47.3% of total energy consumption of the SMS to complete a full cycle and even much reducing in PMT system with the reduction from 76.0 to 86.0%. A method to estimate the saved energy stored in the accumulator will be introduced in this study as well and found out that from 8.2 to 11.6% and from 8.7 to 13.7% of the total energy consumption of the FST and PMT systems were recovered. The SMS shows advantage in transient response with the shortest rise time and smallest overshoot while the steady state error is only slightly smaller than the PMT system. The steady state error of FST system is quite large, but it keeps almost same value for all reference velocity; thus, such system is appropriate for applying in high velocity systems. With acceptable velocity response and extremely improving in energy efficiency, the PMT system is promising to replace conventional water hydraulic system in many applications.© 2014 ASME