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Electrohydraulicservos exhibit nonlinear behavior whenever subjected to dynamic inputs due to the presence of several significant nonlinearities in the servovalve and hydraulic motor. Some mechanical nonlinearities are often responsible for performance limitations as expressed by speed of response, accuracy and stability. This paper deal with the dynamic characteristics of electrohydraulic velocity servos in order to throw more light on the complicated role played by stick-slip friction of the actuator.

The use of gears for power transmission is conditioned by the strength as well as the accuracy. The employment of austempered ductile iron is examined from this view point. The test gears are made of ductile irons FCD45 and FCD60. They are austenized at 900°C then austempered at 300 to 400°C. In the austempering process, the bainitic transformation causes size expansion and a considerable tooth profile error of the gears. The profile error can be reduced by austempering at 400°C or employing the ferrite-bainite dual phase ductile iron. The bending fatigue tests are performed by using electro hydraulic servo controlled pulsators, and SN curves are obtained. The higher the austempering temperature, the higher the fatigue strength. The fatigue strength of gears austempered at 400°C is about 520MPa and it is higher than the strength of normalized S45C gears.

Steering gear mechanical efficiency was measured in drydock for USS KNOX (DE 1052) and found to be 72%. The associated gage readings were later used in sea trials, with inconclusive results. Efficiency of 70% for electro-hydraulic Rapson slide steering gear is now recommended, rather than the traditional values of 80% or 85%.

Static and dynamic characteristics of the deflection have been investigated on a multimorph bender element made with PMN-based electrostrictive ceramics. Using this multimorph, we have developed a high-speed electro-hydraulic servovalve responsive up to 2 kHz with a bandwidth of more than 1 kHz.

The paper reviews some specific aspects encountered in the design and optimisation of the particular software required by the automatic digital control of an electro-hydraulic system, which is used in an industrial robot. A direct digital control structure based upon a microprocessor hardware organisation of the control unit is found to be most profitable. The influence of certain time-delays, of inevitable approximation errors, and of the sampling rate on the overall system performance is then investigated by means of a computer-aided simulation method ; this one also offers the necessary background for the control software optimization. Also briefly discussed is the manner in which the microprocessor handles the potentially dangerous or damaging situations.

The paper describes the preparation of a dynamic model required for simulation of a 30 kW electro-hydraulic system used to induce controlled vibration of a wide range of components, machines or structures. The vibrator system is associated with a 28 tonne seismic block. The model is highly detailed to allow study of the system to its dynamic performance limits of around 300 Hz. The model consists of nearly eighty equations some of them nonlinear and discontinuous. The paper describes the orderly development of the model emanating from the bond graph approach. Some simulation results, with limited experimental correlation, are included.

In this paper, control characteristics of a shaking machine under the influences of an oscillatory test structure are discussed. In addition, it is shown that the influences of the oscillatory test structure can be compensated by feeding back the relative acceleration, velocity and displacement between the shaking table and the test structure with proper gain rate. The effect of this compensation method is confirmed experimentally with a shaking machine which has a one ton table.

In this paper, acceleration control of a shaking machine is investigated, and a control system with feedforward and feedback loop is discussed. It is shown that the response of the control system is improved without losing its stability by pole-zero cancellation when feedforward signals and feedback signals are added with proper rate. This method was confirmed experimentally on a shaking machine and has been applied to some actual shaking machines.

The frequency responses of an experimental electro-hydraulic position control system and a simulation of the system are compared. Three different valve models are used in the simulation in an attempt to highlight the important parameters of an electro-hydraulic servovalve. It is found that a second order compensated valve model based on steady-state considerations provides a good correlation with the experimental system up to 35Hz and can be used for stability calculations up to 80Hz.

The object of this study is to develop a simulation method which aims at calculating the time response of hydraulic control systems. The main feature of this method is that it is applicable to hydraulic systems with fluid line elements. In the previous papers, a fundamental investigation for simulating various kinds of fluid line systems was carried out. In the present paper, therefore, a hydraulic system in which the effect of fluid line dynamics can not be neglected is tackled from a practical point of view. An electro hydraulic servosystem is chosen as representative for such an application. In the simulation, response curves of output variables are calculated, together with pressure responses at arbitrary positions of the fluid line. The results are compared with the measured responses to confirm the validity of the method developed.

Atwo-row electro-hydraulic vegetable seedling block transplanter was designed and tested. The transplanter automatically depotted-cylindrical seedling soil blocks from a seedling tray and transplanted them onto a pre-formed seedling bed. The transplanter was carried on a semi-mounted frame pulled by a tractor. Results of field tests were satisfactory.

Continuously variable automatic transmissions can bring improved fuel economy benefits under good speed ratio changes for automobile propulsion systems in which engines can produce their power under optimum conditions. These systems require computer control for the calculation of optimum speed ratio. The paper presents design features of the electrohydraulic interface between micro-computer and cone-roller toroidal traction drive CVT, dynamic characteristics of cone roller motion, and test results of the practical computer control of CVT.

ELECTRO-HYDRAULIC controls are becoming more prominent for agricultural equipment automation. These control systems need to be designed to attain the desired response specifications while maintaining stability. Personal computers (PC), available to most engineers, can aid in the design of hydraulic control systems. This paper describes a relatively inexpensive software package (TUTSIM)* for continuous dynamic system simulation of hydrualic control system responses. The software package is able to simulate the non-linearities that exist in many electro-hydraulic control systems. A review of hydraulic control system simulation and an application example is included.

The dynamical behavior of an electro-hydraulic servovalve regarded as a combined electro-mechano-hydraulic system, which is especially subjected to external vibratory disturbance, is analysed. The theoretical results of frequency response concerned with the port opening versus input electric signal and also external vibratory displacement are found to agree well with the actual test results under standstill condition and also under external vibration. It is pointed out that the servovalve under test has a very good frequency response up to 500 Hz even in a vibrating accelerated field, provided that the magneto-mechano-hydraulic damping of the torque-motor in it is properly selected.

An electro hydraulic servo type loading system was incorporated into the conventional triaxial shear test apparatus so that any desired form of load pattern can be applied to soil specimens. In applying this system to the study of liquefaction of saturated sands, a difficulty was encountered in keeping the applied stress perfectly controlled even after the rigidity of the sample falls considerably due to the onset of liquefaction. The use of an elastic joint in the loading ram proved very useful to overcome this defect. The acceleration records obtained at the time of the Niigata earthquake of 1964 were used as input load patterns to be applied to saturated specimens of a Niigata sand. The investigation disclosed several features of interest concerning the behaviors of the sand when subjected to irregular exitation.

Summarizing results on recent experimental and analytical investigations for hydrospark forming reported hitherto, in this paper, mechanism of generation of output energy by hydrospark, process of increase of output for the same electrical discharge energy by using explosive powder between electrodes, method of increase of forming efficiency by utilizing powder explosion, etc., are described.

Apart from development testing and a few extreme conditions, a servo system spends most of its life dealing with small movements. These may be so small as to fall into the region of threshold conditions, where non-linearities become of the same order as command signals. In this paper an attempt is made to bring together some of the known facts associated with this region and the techniques used for improvement. It is hoped that this will stimulate further discussion in this interesting and rewarding topic.

Linearized analysis has already been used to demonstrate the de-stabilizing effect of valve flow forces. In this paper an analogue simulation of an electro-hydraulic servomechanism is described and flow force effects are discussed. The results are compared with the linearized analysis. Various types of load and damping are considered. When large accelerations are demanded, the pressure in the actuating cylinder falls to zero and cavitation occurs. During the time this condition exists cylinder pressures in excess of supply pressure occur. A digital computer is used to analyse the performance of a hydraulic servomotor when cavitation exists and the results are presented in dimensionless form. Experimental results are presented for comparison with the theoretical results.

A proportional integral derivative (PID) controller is designed and attached to electro-hydraulic servo actuator system (EHSAS) to control the angular position of the rotary actuator which control the movable surface of space vehicles. The PID gain parameters are optimized by the genetic algorithm (GA). The controller is verified on the new state-space model of servo-valves attached to the physical rotary actuator by SIMULINK program. The controller and the state-space model are verified experimentally. Simulation and experi-mental results verify the effectiveness of the PID controller adaptive by GA to control the angular position of the rotary actuator as com-pared with the classical PID controller and the compensator controller.

Differences were found in the behaviour of two concepts of feed drives when fitted to and tested on the same machine. A comparative study has therefore been made, and the necessary adaptive steps for the improvement of the drives will be discussed with the purpose of comparing the dynamic performances of both feed drives under dynamic disturbing torque loads (interrupted cutting forces), and of achieving the best possible behaviour of the feed drive under given conditions.

ABSTRACT The GRONDIN field offshore Gabon/West Africa is producing oil for ELFAQUITAINE through subsea wellheads controlled by an electrohydraulic control system supplied by MATRA. The installation completed in June 1979 and an experimental maintenance operation of a control pod, 6 months later, have been carried out without any diver assistance. The main features of the control system are: Multiplex Electrohydraulic Control, subsea hydraulic pumps, subsea diverless electrical conductive and hydraulic connections. Due to extensive quality control and test programmes, the Field operations have been achieved without any trouble and in accordance with the Foreseen Schedule. The present paper describes the control system, the development programme and the results of this experimentation. THE GRONDIN PROGRAMME: OBJECTIVES The French Company ELF AQUITAINE has undertaken in 1975 an experimental programme on the GRONDIN field, located 30 miles offshore Gabon, West Africa. The aim of the programme was the development and experimentation of a subsea production station involving a large number of new techniques, in order to prepare the future deepwater oil exploitation. The use of a diverless control system is probably one of the most advanced among these experimentations, as it includes:–Diverless installable and retrievable control pods,–Electro-hydraulic control,–Closed hydraulic circuit using subsea pumps,–Electronic multiplex transmission. After a comprehensive inhouse test programme, including pressure tests on all equipment, the control system has been installed on site in May-June 1979following a rigorous schedule and has since been in operation for over one year without any major failure.

The paper reviews some specific aspects encountered in the design and optimisation of the particular software required by the automatic digital control of an electro-hydraulic system, which is used in an industrial robot. A direct digital control structure based upon a microprocessor hardware organisation of the control unit is found to be most profitable. The influence of certain time-delays, of inevitable approximation errors, and of the sampling rate on the overall system performance is then investigated by means of a computer-aided simulation method; this one also offers the necessary background for the control software optimization. Also briefly discussed is the manner in which the microprocessor handles the potentially dangerous or damaging situations.

Commande electrohydraulique de la hauteur du collecteur de grain et de la vitesse du tambour d'une moissonneuse-batteuse

The requirement for reliable, precise positioning of functions with remote actuation promoted the development of a pressure-compensated electro-hydraulic proportional flow control valve. Lower horsepower consumption, contamination insensitivity, built-in position feedback, and manual operation in case of an emergency were the prime design criteria. The control valve consists of three major components; the first component is a compensator section and the other components are three or more electro-hydraulic proportional valve segments and an outlet section. Design criteria and advantages of using these concepts in typical, mobile hydraulic circuits are discussed. Attention is paid to the control valve's pressure compensation section, electro-hydraulic flow control segment, the control valve's driver stage or low-power electro-magnetic device, pilot stage features where contamination insensitivity and positional feedback are important, ease of over-ride operation and field flushing, operation of the control valve's electro-hydraulic segment, and typical mobile hydraulic circuits and calculations of horsepower loss.

The use of electro-hydraulic control of hydrostatic transmissions on mobile equipment has been limited by the high cost, marginal performance, marginal reliability and poor serviceability of previously available controls. Rapidly increasing usage of electronics on mobile equipment has created a strong need for an electro-hydraulic control without these limitations. A design program was established to develop an entirely new control which both overcomes previous limitations and meets future needs. This was accomplished by selecting the proper design concept to allow meeting all design goals, then carefully implementing and thoroughly qualifying the concept in hardware.

Optimisation des commandes electrohydrauliques utilisant un microprocesseur pour equipements mobiles