Angermann L. (ed.). Numerical Simulations - Applications, Examples and Theory

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a) b)

Fig. 25. a) Variation of rotational speed of hydraulic motor within the secondary sector to a

ramp type excitation signal of flow adjustment systems within the primary sector, b)

Variation of pressure along the primary circuit to a ramp type excitation signal of flow

adjustment systems within the primary sector

We have recorded the pressures within the circuit, fig.26 (blue- variation of rotational speed

of hydraulic motor; brown- variation of the supply voltage of hydraulic motor in an energy-

efficient system; red- variation of the supply voltage of hydraulic motor in an energy-

inefficient system).

In fig.27, after calculation of hydraulic power used by the pump within the primary sector

(P=Q*p), we have traced evolution over time of this power for the two flow adjustment

systems, without (brown) and with (blue) energy efficiency.

The obtained data were integrated numerically in order to result the evolution of the

consumed energy, fig.28 (brown- energy-inefficient system, blue- energy-efficient system).

Area of the surface defined by the two curves represents the energy savings.

Fig. 26. Variation of pressure along the primary circuit of hydraulic transmission, at control

signal with preset profile for rotational speed of the motor within the secondary sector

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Fig. 27. Variation of the hydraulic power used by the pump within the primary sector of

transmission, at control signal with preset profile for rotational speed of the motor within

the secondary sector

Fig. 28. Variation of energy used by the pump within the primary sector of transmission, at

control signal with preset profile for rotational speed of the motor within the secondary

sector

3.5 Optimization of the adjustment model of a hydraulic transmission with secondary

adjustment

We aimed to optimize the adjustment model of a hydraulic transmission with secondary

adjustment, derived from the hydraulic transmission with mixed adjustment. Optimization

is performed in view of two goals: to reduce the variation range of rotational speed of the

motor within the secondary sector, caused by variation of its load, and to reduce the extra

flow discharged through the valve of the pump within the primary sector of transmission.

A pre-step in optimizing the adjustment model of hydrostatic transmission is represented by

optimization of the simulation model in AMESim of transmission. In order to achive this,

three variants of simulation models were developed:

variant (a), according to fig.29: hydraulic transmission with secondary adjustment, with

fixed pump and variable motor, with compensator type P (proportional) in the

adjustment loop of rotational speed;

variant (b), according to fig.30: hydraulic transmission with secondary adjustment, with

fixed pump and variable motor, with compensator type PID (proportional, integrative,

derivative) in the adjustment loop of rotational speed;

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- variant (c), according to fig.31: hydraulic transmission with secondary adjustment, with

adjustable pump equipped with pressure regulator and variable motor, with

compensator type P (proportional) in the adjustment loop of rotational speed.

Fig. 29. Simulation model in AMESim – hydrostatic transmission with secondary

adjustment:

variant (a)

Fig. 30. Simulation model in AMESim – hydrostatic transmission with secondary

adjustment:

variant (b)

Fig. 31. Simulation model in AMESim – hydrostatic transmission with secondary

adjustment: variant (c)

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For the three simulation models the proportional pressure valve, associated with the fixed

pump for simulation of the load of the servo motor witin the secondary sector of hydrostatic

transmission, is excited with a rectangular signal. We traced variation over time of the

rotational speed of hydraulic servo motor, caused by variation of its load. Simulation model

– variant (c) is run simultaneously for three maximum values of the capacity of hydraulic

servo motor. Obtained results are presented in fig.32, fig.33 and fig.34.

Fig. 32. Variation of rotational speed of hydraulic motor-

variant (a)

Fig. 33. Variation of rotational speed of hydraulic motor-

variant (b)

Fig. 34. Variation of rotational speed of hydraulic motor-

variant (c)

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4. Conclusions

Obtaining mathematical models, as close as possible to physical phenomena which are

intended to be replicated or improved, help us in deciding how to optimize them. The

introduction of computers in monitoring and controlling processes caused changes in

technological systems. With support from the methods for identification of processes and

from the power of numerical computing equipment, researchers and designers can shorten

the period for development of applications in various fields by generating a solution as close

as possible to reality, since the design stage.

4.1 Conclusions

As you can see from the diagrams of the transfer locus of servo mechanism (fig.7), its

stability reserve increases along with decreasing amplification factor in flow of directional

control valve around the null.

It can be noted that the amplification margin increases by about 15 percent when using

directional control valve with variable area gradient, approaching the value 0.75, which is

considered optimal in the literature (Vasiliu & Vasiliu, 2005).

Authors of this paper consider interesting the approach to simulate the method of enlarging

the stability reserve by reducing the amplification factor around null and conditioning the

control signal of distributing electromagnet to "trace" area profile of a slide valve

"geometrically" shaped.

The advantages of using this method are: reduced cost of execution of slide valves,

possibility to upgrade for systems without variable area gradient, improvement of

performance of servo systems.

4.2 Conclusions

The adjustment model of a hydrostatic transmission, developed through technique of co-

simulation AMESim/ LabVIEW, enables virtual and experimental analysis of phenomena

specific to fluid power installations.

The web adjustment model of the hydrostatic transmission enables access to the drives and

results of tests carried upon the physical laboratory model also for the persons outside the

laboratory.

The adjustment model of a hydrostatic transmission with mixed adjustment enables remote

control upon the parameters of hydraulic motor, depending on the actuation on hydraulic

servomechanisms that adjust capacities of adjustable volumetric machines within the

primary and secondary sectors.

The developed adjustment model highlights the advantages in terms of energy of hydraulic

transmissions with servopumps within their primary sector over transmissions with fixed

pumps within their primary sector.

By means of successive simulations in AMESim, on three simulation models equivalent to

the physic laboratory model, a hydraulic transmission with secodary adjustment was

optimized, in terms of energy consumption and functional performances.

Optimal version of the simulation model, variant (c), represents the basis for optimization of

the adjustment model for hydraulic transmissions with secodary adjustment, derived from

the hydraulic transmission with mixed adjustment. In this variant of simulation the

variation range of rotational speed of the hydraulic motor within the secondary sector, in

conditions of variation of its load after a rectangular signal, is minimum, while through the

pressure valve of the pump within the primary sector the extra flow is null.

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5. References

Bosch Rexroth Group - www.boschrexroth.com

Calinoiu, C., Vasiliu, N. & Vasiliu, D. (1998). Modeling, Simulation and experimental

Identification of the Hydraulic Servomechanisms, Technical Publishing House,

Bucharest, Romania, 222 p., ISBN 973-31-1315-8

Catana, I.; Vasiliu, D. & Vasiliu, N. (1996). Servomecanisme electrohidraulice, Technical

Publishing House, POLITEHNICA University, Bucharest

a. Drumea, P.; Popescu, T.C.; Blejan, M. & Rotaru, D. (2010). Research Activities Regarding

Secondary and Primary Adjustment in Fluid Power Systems, 7th International Fluid

Power Conference Aachen Efficiency through Fluid Power, Scientific Poster Session,

Aachen, Germany, 22-24 March 2010

b. Drumea, P.; Popescu, T.C. & Ion Guta, D.D. (2010). Research activities regarding energetic

and functional advantages of hydraulic transmissions, Proceedings of SGEM 2010,

10th International Multidisciplinary Scientific Geo-Conference & EXPO Modern

Management of Mine Producing, Geology and Environmental Protection, Albena

Resort-Bulgaria, 20 June - 25 June 2010

a. Ion Guta, D.D.; Lepadatu, I.; Popescu, T.C. & Dumitrescu, C.(2010). Research on the

stability of electrohydraulic servomechanisms developed with electrohydraulic

amplifiers of variable area gradient, Proceedings of 2010 International Conference on

Optimisation of the Robots and Manipulators, Calimanesti, Romania, 28-30 May, 2010

b. Ion Guta,D.D.; Popescu,T.C. & Dumitrescu,C.(2010). Optimization of hydrostatic

transmissions by means of virtual instrumentation technique, Proceedings of

ATOM-n 2010, The 5

edition of the International Conference "Advanced Topics in

Optoelectronics, Microelectronics and Nanotechnologies", 26-29 August 2010,

Constanta, Romania

LMS IMAGINE SA (2009). Advanced Modelling And Simulation Environment, Release

8.2.b., User Manual, Roanne, France

National Instruments (2009). User Manual, NI USB-621x

Popescu, T.C.; Ion Guta, D.D. & Marin, A. (2010). Adjustment of hydrostatic transmissions

through virtual instrumentation technique, ENERG_02, Proceedings of ISC 2010,

June 7-9, 2010, Budapest, Hungary

Popescu, T.C.; Lepadatu,I. & Ion Guta,D.D. (2009). Experimental research activies regarding

the reduction of energy compsuntion at endurance test stands of rotary voliumetric

machines, Proceedings of International Scientific Technical Conference Hydraulics

and Pneumatics 2009, Wroclaw, 7-9 October, ISBN 978-83-87982-34-8, pp. 303-310.

Vasiliu, N. & Vasiliu, D. (2005). Fluid Power Systems, Vol.I., Technical Publishing House,

Bucharest, Romania, ISBN 973-31-2249-1

Applications of

the Electrohydraulic Servomechanisms in

Management of Water Resources

Popescu T. C.

, Vasiliu D.

, Vasiliu N.

and Calinoiu

National Institute for Optoelectronics, INOE 2000-IHP Bucharest,

University „Politehnica” of Bucharest

Romania

1. Introduction

Water and energy are key component of almost all human activities. Water supply is vital to

feeding the growing world population, to production of mat natural systems on which life

on earth relies. In the context of erial goods which cause rising of living standards and to

maintaining the integrity of world water crisis, more and more governments have begun to

develop new policies for future, aiming at rationalization and efficiency of water

consumption.

Maximum reduction of waste and undue loss of water is an important objective in the

management of water resources. In this sense any valuable technical solution that helps

achieve these goals, especially at the large water consumers, deserves to be implemented.

To illustrate this, we propose the use of the automated land leveling systems, tracing a laser

reference plane, as a method of reducing water losses in two activity areas: crop irrigation

and construction of earth dams in hydropower stations. In the last decade, these works are

performed with leveling machines equipped with laser modular systems manufactured by

companies like TOPCON from Japan or APACHE and SPECTRA PRECISION from USA.

In the first kind of activity, the solution ensures equal conditions, in terms of water

consumption, for all plants on agricultural land, watered by natural way - rainfalls, or

artificially - by irrigation systems. This solution prevents areas of "pools" of water on

agricultural land, and providing deviations from the reference plane of max. ± 2 cm by only

2 passes of the leveling machine (rough, and smoothing leveling) eliminates soil loosening

works, which are necessary after conventional leveling.

In the second case, the method ensures optimal thickness, depending on the type of

compression equipment, of the earth layers deposited when constructing dam body, with

maximum deviations of ± 2 cm over the entire surface of the deposited layer. This type of

smoothing performed before the compaction of each layer of soil deposited in the dam

body, ensures a uniform degree of compaction of the dam, fig.1. Homogeneity of dam

compaction is a measure for reducing seepage through the dam and pronounced

settlements of the top, causing possible overflowing of water above the top of the dam, fig.2.

Laser modulation systems are not included in the standard facilities, not even in the latest

modern leveling machines, fig.3. They can be installed on any hydraulically actuated

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leveling machine, regardless of its wear or origin. The laser modular system includes a laser

emission module, a laser receiver module, an electronic block and an electro hydraulic servo

system (distribution block). Starting in 2008, the mounting on leveling equipment and the

service of TOPCON laser modular equipment is performed in Europe by the representatives

of Geodis Brno, Geodis Slovakia, Geodis Geodis Ro and Geodis Austria. These distributors

are companies that get the laser and electronic modules from TOPCON, and the electro-

hydraulic components from different suppliers.

Fig. 1. Main section through an earth dam

Fig. 2. Example of water flood over a dam January the 1

2006 Sherman Island

Fig. 3. Laser controlled electro hydraulic leveling machine (courtesy New Holland)

The wide diversity of the fluid power systems used on leveling machinery, supplied by

various manufacturers, and with different degree of wear, represents factors that leads to

extension of mounting period of a modular laser system type TOPCON on a leveling

machine.

This chapter presents the structure, performance, and the optimal synthesis by numerical

simulation of a testing bench designed for TOPCON laser modular systems, which

reproduce the operating conditions of the systems set up on the real leveling machines. The

device was developed by the aid of a numerical simulation model built in AMESim, is an

electro hydraulic servomechanism of position control with feedback by laser. This

servomechanism contains two internal control loops for position control: the first loop

appears at the level of a servomechanism that simulates the profile of uneven soil, and the

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449

second control loop appears at the level of a tracing servomechanism with laser reference.

Dynamic performance obtained by numerical simulation and experimental identification of

a TOPCON laser modular system, are in good agreement with those obtained by

comparative testing of the same system mounted on a motor grader, in actual operation

(Popescu et al., 2008, 2009).

The testing bench developed by INOE 2000-IHP Bucharest, allows the laboratory tuning

always needed to be made in order to fit the parameters of laser modular system with the

parameters of machine on which are to be mounted. If some malfunction occurs in operation

of the machine equipped with a laser modular system, using the testing device one can

detect which component of the system no longer provides the functional parameters (laser

emitter, laser receiver, electrohydraulic block or electronic block).

2. Laser modular systems made for equipping the ground leveling

installations

The leveling technology which uses laser, fig.4, implies a leveling performed by a complex

installation, equipped with laser controlled modular system, which is able to perform work

from 2 passes, a rough leveling and a fine one at finish, with deviations from the reference

plane of max. 2,5 cm on the entire leveled surface with a significant reduction of the

tracking, transposition and materialization process during the leveling work.

The modular mechatronic system with laser, electronic and electrohydraulic components,

which allows reaching this leveling technology may be mounted on any land leveling

equipment whose work bodies, scoops or blades are hydraulically powered. It is conceived

as an additional option of the land leveling equipment, which offers to it the possibility of

leveling land automatically, without any human error occurrence in what regards precision.

Fig. 4. The laser leveling technology: a) mounting the laser modules transmitter and

receiver; b) automatic leveling after an optical leveling plan PON performed

simultaneously by 6 land leveling equipments UTN

In the classic acception land leveling controlled by laser systems implies a modular system

with the following structure.

a. The laser transmitter placed in the center of the surface to be leveled above a point with

a known quote mark, on a tripod which may be adjusted vertically, emitting a laser

beam in its rotation movement. This generates the laser reference plane or the optical

refence plane (with programming options for the longitudinal and transversal slope in

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450

the forward direction) which the work body of the equipment will follow during

leveling. After setting the slope needed at leveling, the laser transmitter positions itself

automatically.

b. The laser receiver, whose support is connected to the work body of the land leveling

equipment, intercepts the laser fascicle generated by the laser transmitter and sends

altimetric information, namely the position of the work body accountable to the laser

reference plane, to an electronic control and monitoring module, placed in the cabin of

the land leveling equipment.

c. The electronic monitoring and control module which conects and amplifies the laser

information received, compares it with a prescribed dimension specific for the leveling

quote value, finds the error and emits a prompt for cancelling error, towards an

electrohydraulic drive system.

d. The electrohydraulic system controlled by the electronic module has the role of driving

the hydraulic cylinders of the blade for maintaining the work body in the leveling plane

set by the leveling project, plane which is parallel with the laser reference plane. In fig.5.

are presented two types of land leveling machines equipped with modular systems.

a) b) c)

Fig. 5. Leveller (a) and autograder (b) equipped with laser controlled modular systems (c)

3. Simulating the real operational conditions of the laser module by an

original test bench

In fig.6-a is shown the laboratory test bench which simulates the real behavior of the

TOPCON laser controlled modular system purposefully created for equipping the

automatic land leveling machines in horizontal plane (Popescu et al., 2008). Fig.6-b shows

the mode of equalization of the device with the simulation model from AMESim.

On the rod of the upper hydraulic cylinder is fixed the laser receiver which may move by

the action of the upper cylinder or of the bottom cylinder or of both.

The device for testing the laser controlled equipment includes 2 electro hydraulic

servomechanisms that simulate the real behavior of the upward downward hydraulic

cylinders of the blade of the land leveling machine, and the second - the profile of the land

to be levelled.

The first servomechanism contains a hydraulic cylinder similar with that mounted on the

machine, supplied from the hydraulic delivery block TOPCON depending on the level of

detection of the laser reference plane, generated by a rotary laser transmitter TOPCON.

The second servomechanism consists of a hydraulic servocylinder controlled by a

proportional valve with integrated electronics, by means of a data aquisiton board, a PC and

the data aquisition software TEST POINT produced by Capital Corporation from USA.