Slide 1 G. Grossschmidt, M. Harf, P. Grigorenko

TALLINN UNIVERSITY OF TECHNOLOGY

Modelling and Simulation of a Hydraulic-Mechanical Load-Sensing System in

CoCoViLa environment

Gunnar Grossschmidt Mait Harf

Pavel Grigorenko

Tallinn University of TechnologyInstitute of Machinery and Institute of Cybernetics

Slide 2 G. Grossschmidt, M. Harf, P. Grigorenko

TALLINN UNIVERSITY OF TECHNOLOGY

Introduction

Fluid power systems, in which working pressure (pressure in pump output) is kept proportional to load, are called hydraulic load-sensing systems. Such systems are mainly used with the purpose to save energy.

Hydraulic load-sensing systems are automatically regulating systems with a number of components and several feedbacks. Feedbacks make the system very sensitive and unstable for performance and simulation. A very precise parameter setting, especially for resistances of hydraulic valve spools and for spring characteristics, is required to make the system function.

Steady state conditions and dynamic behavior of the hydraulic load-sensing system are simulated.

Slide 3 G. Grossschmidt, M. Harf, P. Grigorenko

TALLINN UNIVERSITY OF TECHNOLOGY

Pump with regulator: • Variable displacement axial piston pump • Electric motor • Control valves • Control cylinder

Hydraulic motor feeding chain: • Tube RL-zu • Pressure compen- sator Ridw • Measuring valve Rwv • Check valve • Meter-in throttle edge Rsk-zu

Hydraulic motor Rverb

Hydraulic motor output chain: • Meter-out throttle edge Rsk-r • Tube RL-ab

p0 = const

RIDVW

Scheme of the hydraulic-mechanical load-sensing system

Slide 4 G. Grossschmidt, M. Harf, P. Grigorenko

TALLINN UNIVERSITY OF TECHNOLOGY

Components • Spool valve• Spool valve inflow slot• Spool valve outflow slot• Constant resistor • Positioning cylinder • Swash plate with spring

Throttle edges• Measuring throttle edge Rvw• Pressure compensator throttle edge Ridw• Meter-in throttle edge Rsk-zu• Meter-out throttle edge Rsk-r

Controller Valve block

Slide 5 G. Grossschmidt, M. Harf, P. Grigorenko

TALLINN UNIVERSITY OF TECHNOLOGY

Object-oriented modelling based on multi-pole models with oriented causality is used for fluid power systems.

A1 Q1 xp,vp Q2 A2 x,v v

p1 Fp p2 F

m, h

Q1 p1

H h Q2 p2 v F

G h Q1 p1

Q2 p2 v

F

Q1

p1

Y g Q2 p2 v

F

Q1 p1

Y h Q2 p2 v

F

Four forms (causalities) of six-pole models for a

hydraulic cylinder

The hydraulic cylinder has three pairs of variables: p1, Q1; p2, Q2; x (or v), F; where p1, p2 – pressures in the cylinder chambers, Q1, Q2 – volume flow rates in cylinder chambers, x, v – position and velocity of the piston rod,F – force on the piston rod.

For composing a model for the fluid power system, it is necessary to build multi-pole models of components and connect them between themselves.

Multi-pole models

Slide 6 G. Grossschmidt, M. Harf, P. Grigorenko

TALLINN UNIVERSITY OF TECHNOLOGY

Composing the model

Component modelsVP - control valve RVP - meter-in throttle

edge of control valveZV - positioning cylinder REL - constant resistor RVT - meter-out throttle

edge of control valvePV - variable displacement

pumpME - electric motor RIDVWlin - linear measu-

ring valve with pres- sure compensator

RSKZ, RSKA - meter-in and meter-out throttle edge for hydraulic

motor MH - hydraulic motorIEH - hydraulic interface

element RtuHS - tubes

Multi-pole model of the hydraulic-mechanical load-sensing system for steady-state conditions

Slide 7 G. Grossschmidt, M. Harf, P. Grigorenko

TALLINN UNIVERSITY OF TECHNOLOGY

Simulation steps

First, the hydraulic motor, hydraulic pump, electric motor and fluid

parameters must be chosen.

Second, initial approximate values of pressures, pressure differences for pump control, maximum displacements of the valves, parameters of springs, geometry of valves working slots, etc. must be set up.   

Third, all the models of components must be tested separately. For this purpose, for every component the simulation problem must be composed, approximate input signals must be chosen and finally, action of the component must be simulated.

Fourth, the separately tested component models must be connected into more complicated subsystems and finally into whole system and tested in behavior. 

Fifth, components models must be revised and parameters values of the system must be adjusted as a result of solving simulation tasks.

Slide 8 G. Grossschmidt, M. Harf, P. Grigorenko

TALLINN UNIVERSITY OF TECHNOLOGY

Meter-out throttle edge for hydraulic motor

Fig. 9 - Simulated pressure drop in measuring valve with pressure compensator depending on the displacement of the directional valve

Slide 9 G. Grossschmidt, M. Harf, P. Grigorenko

TALLINN UNIVERSITY OF TECHNOLOGY

Clutch with inertia

Fig. 9 - Simulated pressure drop in measuring valve with pressure compensator depending on the displacement of the directional valve

Slide 10

G. Grossschmidt, M. Harf, P. Grigorenko

TALLINN UNIVERSITY OF TECHNOLOGY

Hydraulic motor subsystem

Slide 11

G. Grossschmidt, M. Harf, P. Grigorenko

TALLINN UNIVERSITY OF TECHNOLOGY

Simulation of steady state conditions

Slide 12

G. Grossschmidt, M. Harf, P. Grigorenko

TALLINN UNIVERSITY OF TECHNOLOGY

Simulation of dynamics

Simulation characteristics

Initial displacement of the directional valve 0.0045 m.Initial load moment of the drive mechanism

65 Nm.

Step change (during 0.01 s) is applied to:- the initial load moment- the initial displacement of the

directional valve.

Time step 5 µs.

Simulated time 0.5 s (results are calculated for 100 000 points).

Slide 13

G. Grossschmidt, M. Harf, P. Grigorenko

TALLINN UNIVERSITY OF TECHNOLOGY

Initial displacement of the directional valve 0.0045 m Load moment of the drive mechanism 65 NmStep change 0.001 m (during 0.01 s) applied to the initial displacement Time step is 5 µsSimulated time is 0.5 s (results have been calculated for 100 000 points). Simulation time 17.1 s

Slide 14

G. Grossschmidt, M. Harf, P. Grigorenko

TALLINN UNIVERSITY OF TECHNOLOGY

Initial load moment of the drive mechanism 65 Nm. Displacement of the directional valve 0.0045 mStep change 45 Nm (during 0.01 s) applied to the initial load moment. Time step is 5 µsSimulated time is 0.5 s (results have been calculated for 100 000 points). Simulation time 18.8 s

Slide 15

G. Grossschmidt, M. Harf, P. Grigorenko

TALLINN UNIVERSITY OF TECHNOLOGY

Size and complexity

The package for modelling and simulation of the load-sensing system contains:

- 42 classes, including 27 component classes;

- more than 1000 variables;

- 17 variables that have to be iterated during the computations;

- 73 links between system components.

The automatically constructed Java code for solving the simulation

task of the dynamics of the load-sensing system contains 4124 lines

and involves 5 algorithms for solving subtasks.

Slide 16

G. Grossschmidt, M. Harf, P. Grigorenko

TALLINN UNIVERSITY OF TECHNOLOGY

3D simulation

3D simulation of steadystate conditions

Calculated

1000 x 1000 points

Calculation time

119 s

Slide 17

G. Grossschmidt, M. Harf, P. Grigorenko

TALLINN UNIVERSITY OF TECHNOLOGY

Thank you for attention