1. ANALIYSIS AND SYNTHESIS
OF AN ELECTROHYDRAULIC CLOSED LOOP CONTROL
SYSTEM FOR THE VIBRATIONAL TESTING MACHINE
TECHNICAL UNIVERSITY OF SOFIA
Department: Hydro-aero-dynamics and hydraulic machines
Prof. dr. Ilcho Angelov
Dipl. eng. Nikola Stanchev
Dipl. eng. Cvetozar Ivanov

2. INTRODUCTION
The article presents research and development of electro-hydraulic closed loop
system for vibration test unit for the needs of the Faculty of Industrial Technology (FIT) at
the Technical University of Sofia. The synthesis of the hydraulic system is accomplished
in accordance with pre-set technical requirements as follows:
- spatial direction of testing, 2 axes : horizontal and vertical;
- driven mass of the test object and design of the platform: m = 1500 kg;
- acceleration of the test object: a ≤ 30 m/s2;
- frequency range with acceleration a = 30 m/s2: f0 = 1 ÷ 30 Hz;
- maximum amplitude for both directions : X ≥ 3 mm;
- drive power: ≤ 30 kW;

3. OVERVIEW – HYDRAULIC TEST BENCHES
 Simulation of road conditions

4.  Realistic real-time simulation
 6 DOF (Degree Of Freedom)
 Big drive forces, up to 60 kN
 Big velocities, up to1,7 m/s
 Big accelerations, up to100 m/s2
 Very big frequencies with big
drive forces, up to 100 Hz
 Big stiffness of the drive with big
frequencies, independent
from the driven load
ADVANTAGES OF ELECTROHYDRAULIC TEST BENCHES

5. HYDRAULIC DRAFT OF THE ELECTROHYDRAULIC SYSTEM

6. HYDRAULIC DRAFT OF THE ELECTROHYDRAULIC SYSTEM

7. HYDRAULIC DRAFT OF THE ELECTROHYDRAULIC SYSTEM

8. CALCULATION OF THE BASIC WORK PARAMETERS
 Drive force of the cylinder…………….…………………………………………….
 Active area of the cylinder…..……………………………………………………..
 Work pressure of the cylinder………………………………..…………………….
 Velocity of the cylinder.…………………………………………………………….
 Acceleration of the cylinder…………………….…………………………………
 Maximum velocity of the cylinder………………………………………………..
 Maximum acceleration of the cylinder………………………………………….
 Maximum flow of the pump……...………………………………………………...
c c
F p .A 
 2 2
c P A
A D d
4

 
c W Е ХСК
p p p   
   v t x t
.
 a x t &&
v 2 fA 
2 2
a 4 f A 
q vA

9. CALCULATION AND SIMULATION OF THE WORK PARAMETERS

10. CALCULATION AND SIMULATION OF THE WORK PARAMETERS

11.  In sinusoidal input impact in
the frequency range from
1 to 12 Hz desired acceleration
of 3g can not be reached!
fi, Hz a, m/s2 х, mm q, l/min v, m/s P, kW
1 2 60 58 0,38 26
2 5 30 58 0,38 26
3 7 20 58 0,38 26
4 9 15 58 0,38 26
5 12 12 58 0,38 26
6 14 10 58 0,38 26
7 16 8,5 58 0,37 26
8 19 7,5 58 0,38 26
9 21 6,7 58 0,38 26
10 24 6 58 0,38 26
11 26 5,4 58 0,37 26
12 28 5 58 0,38 26
13 30 4,5 57 0,37 25
14 30 3,9 53 0,34 23
15 30 3,4 49 0,32 21
16 30 3 47 0,3 19
17 30 2,6 43 0,28 17
18 30 2,35 41 0,27 16
19 30 2,1 39 0,25 18
20 30 1,9 37 0,24 17
21 30 1,7 35 0,22 15
22 30 1,55 33 0,21 14
23 30 1,45 32 0,21 14
24 30 1,3 30 0,2 13
25 30 1,2 29 0,19 12
26 30 1,14 29 0,19 12
27 30 1,05 27 0,18 11
28 30 0,97 26 0,17 11
29 30 0,9 25 0,16 10
30 30 0,85 25 0,16 10
PHYSICAL PARAMETERS OF THE HORIZONTAL CYLINDER
3g

12.  Frequency 13 Hz and amplitude 4,5 mm
DYNAMIC BEHAVIOR OF THE HORIZONTAL CYLINDER
t, s0
S, mm
0,077 (13 Hz)
4,54,5
3g
3g

13. 0
S, mm
0,033 (30 Hz)
0,850,85
t, s
3g
3g
3g
3g
3g
 Frequency 30 Hz and amplitude 0,85 mm
3g ► 1 ÷ 12 Hz
DYNAMIC BEHAVIOR OF THE HORIZONTAL CYLINDER

14. DYNAMIC BEHAVIOR OF THE HORIZONTAL CYLINDER
 Frequency 12 Hz and amplitude 2,1 mm
t, s0
S, mm
2,12,1
0,0833 (12 Hz)
3g
0,012 tПР
2
a.t
A
2

2
2А
а
t


15.  Calculated physical parameters for horizontal cylinder in intermittent
treatment with transition process in the range 0,005 – 0,013 s and restriction
of the maximum flow that the servo valve can give (qmax = 60 l/min),
a, m/s2 tПР, s х, m v, m/s q, m3/s q, l/min fi,max Hz
30 0,005 0,00038 0,15 0,00038 23 50
30 0,006 0,00054 0,18 0,00046 27,6 41,6
30 0,007 0,00074 0,21 0,00054 32,2 35,7
30 0,008 0,00096 0,24 0,00061 37 31,2
30 0,009 0,00122 0,27 0,00069 41,5 27,7
30 0,01 0,0015 0,3 0,00077 46 25
30 0,011 0,00182 0,33 0,00084 50,7 22,7
30 0,012 0,00216 0,36 0,00092 55,3 20,8
30 0,013 0,00254 0,39 0,001 59,9 19,2
PHYSICAL PARAMETERS OF THE HORIZONTAL CYLINDER

16. Horizontal servocylinder
Vertical servocylinders
RESULTS- 3D MODEL OF THE TEST BENCH
 The design was tested with simulation at operating frequencies above 50 Hz,
there is no danger of resonance (3D CAD SolidWorks)

17. TU – SOFIA, Department: HAD and HM
THANK YOU FOR
THE ATTENTION!