Transcript Slide

Modelling and Simulation of a
Hydraulic-Mechanical Load-Sensing System in
CoCoViLa environment
Gunnar Grossschmidt
Mait Harf
Pavel Grigorenko
Tallinn University of Technology
Institute of Machinery and Institute of Cybernetics
TALLINN UNIVERSITY OF TECHNOLOGY
G. Grossschmidt, M. Harf, P. Grigorenko
Slide 1
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 loadsensing system are simulated.
TALLINN UNIVERSITY OF TECHNOLOGY
G. Grossschmidt, M. Harf, P. Grigorenko
Slide 2
Scheme of the hydraulic-mechanical load-sensing system
Pump with
regulator:
RIDVW
p0 = const
• Variable displacement
axial piston pump
• Electric motor
• Control valves
• Control cylinder
Hydraulic motor
feeding chain:
• Tube RL-zu
• Pressure compensator 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
TALLINN UNIVERSITY OF TECHNOLOGY
G. Grossschmidt, M. Harf, P. Grigorenko
Slide 3
Controller
Components
• Spool valve
• Spool valve inflow slot
• Spool valve outflow slot
• Constant resistor
• Positioning cylinder
• Swash plate with spring
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Valve block
Throttle edges
• Measuring throttle edge Rvw
• Pressure compensator throttle edge Ridw
• Meter-in throttle edge Rsk-zu
• Meter-out throttle edge Rsk-r
G. Grossschmidt, M. Harf, P. Grigorenko
Slide 4
Multi-pole models
Object-oriented modelling based on multi-pole models with oriented
causality is used for fluid power systems.
Q1
A1 Q1 xp,vp Q2 A2
v
x,v
G h
p1
Q2
Q1
p2
v
F
p1
Q2
Q1
p2
v
F
p1
H h
p2
v
F
m, h
Q1
p1
p1 Fp p2
F
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.
Y g
Q2
Y h
Q2
p2
v
F
Four forms (causalities) of six-pole models for a
hydraulic cylinder
For composing a model for the fluid power system, it is necessary to build multi-pole
models of components and connect them between themselves.
TALLINN UNIVERSITY OF TECHNOLOGY
G. Grossschmidt, M. Harf, P. Grigorenko
Slide 5
Composing the model
Component models
Multi-pole model of the hydraulic-mechanical loadsensing system for steady-state conditions
TALLINN UNIVERSITY OF TECHNOLOGY
VP - control valve
RVP - meter-in throttle
edge of control valve
ZV - positioning cylinder
REL - constant resistor
RVT - meter-out throttle
edge of control valve
PV - variable displacement
pump
ME - electric motor
RIDVWlin - linear measuring valve with pressure compensator RSKZ,
RSKA - meter-in
and
meter-out throttle
edge
for hydraulic
motor
MH - hydraulic motor
IEH - hydraulic interface
element
RtuHS - tubes
G. Grossschmidt, M. Harf, P. Grigorenko
Slide 6
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.
TALLINN UNIVERSITY OF TECHNOLOGY
G. Grossschmidt, M. Harf, P. Grigorenko
Slide 7
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
TALLINN UNIVERSITY OF TECHNOLOGY
G. Grossschmidt, M. Harf, P. Grigorenko
Slide 8
Clutch with inertia
Fig. 9 - Simulated pressure drop in measuring
valve with pressure compensator depending
on the displacement of the directional valve
TALLINN UNIVERSITY OF TECHNOLOGY
G. Grossschmidt, M. Harf, P. Grigorenko
Slide 9
Hydraulic motor subsystem
TALLINN UNIVERSITY OF TECHNOLOGY
G. Grossschmidt, M. Harf, P. Grigorenko
Slide 10
Simulation of steady state conditions
TALLINN UNIVERSITY OF TECHNOLOGY
G. Grossschmidt, M. Harf, P. Grigorenko
Slide 11
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).
TALLINN UNIVERSITY OF TECHNOLOGY
G. Grossschmidt, M. Harf, P. Grigorenko
Slide 12
Initial displacement of the directional valve 0.0045 m
Load moment of the drive mechanism 65 Nm
Step change 0.001 m (during 0.01 s) applied to the initial displacement
Time step is 5 µs
Simulated time is 0.5 s (results have been calculated for 100 000 points).
Simulation time 17.1 s
TALLINN UNIVERSITY OF TECHNOLOGY
G. Grossschmidt, M. Harf, P. Grigorenko
Slide 13
Initial load moment of the drive mechanism 65 Nm.
Displacement of the directional valve 0.0045 m
Step change 45 Nm (during 0.01 s) applied to the initial load moment.
Time step is 5 µs
Simulated time is 0.5 s (results have been calculated for 100 000 points).
Simulation time 18.8 s
TALLINN UNIVERSITY OF TECHNOLOGY
G. Grossschmidt, M. Harf, P. Grigorenko
Slide 14
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.
TALLINN UNIVERSITY OF TECHNOLOGY
G. Grossschmidt, M. Harf, P. Grigorenko
Slide 15
3D simulation
3D simulation of steady
state conditions
Calculated
1000 x 1000 points
Calculation time
119 s
TALLINN UNIVERSITY OF TECHNOLOGY
G. Grossschmidt, M. Harf, P. Grigorenko
Slide 16
Thank you for attention
TALLINN UNIVERSITY OF TECHNOLOGY
G. Grossschmidt, M. Harf, P. Grigorenko
Slide 17