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Research on Travel Control System of Hydrostatic Transmission Chassis

Authors:

Abstract

Aiming at the control problem of driving system of hydrostatic transmission chassis, the composition of the control system of hydrostatic transmission chassis is introduced and the control method of dual engine is solved. According to the number of driving axles in driving process, The external characteristic curve of the engine controls the variable hydraulic pump by one parameter, controls the rotational speed of the variable hydraulic motor according to the change of the vehicle speed, and introduces the control flow of the brake system. It provides a reference for the design of driving control system of multi-axis hydrostatic transmission chassis.
a Corresponding author: zhaoliangslg@163.com
Research on Travel Control System of Hydrostatic Transmission Chassis
Liang Zhao 1,2,a, Jin Wang 2 and Zhengwu Zhang 2
1 Changan University, School of Construction Machinery, 710064 Xian ,China
2 Shaanxi University of Technology, School of Machinery Engineering, 723001 Hanzhong , China
Abstract. Aiming at the control problem of driving system of hydrostatic transmission chassis, the composition of the
control system of hydrostatic transmission chassis is introduced and the control method of dual engine is solved.
According to the number of driving axles in driving process, The external characteristic curve of the engine controls
the variable hydraulic pump by one parameter, controls the rotational speed of the variable hydraulic motor according
to the change of the vehicle speed, and introduces the control flow of the brake system. It provides a reference for the
design of driving control system of multi-axis hydrostatic transmission chassis.
1 Introduction
With the development of the national economy, more and
more high-rise buildings in the city, and its
accompanying construction and fire-fighting machinery
and equipment are also toward large-scale development
in order to meet the construction and fire safety
requirements. For large-scale construction machinery and
equipment to develop high load capacity and through the
hydrostatic hydraulic chassis, in order to make it get
better power and economy, the study of multi-axis
hydrostatic drive chassis drive system in the control
Some methods can solve the problem of lack of theory in
the driving system of multi-axis hydrostatic drive chassis
and provide a solution for the speed control of the
hydraulically driven chassis at high speed.
Large-scale machinery and equipment need to have a
high carrying capacity of the chassis, and to be able to
facilitate the operation, to achieve the vehicle's micro-
driving and high-speed requirements. Hydrostatic
transmission technology has a compact structure, wide
speed range, easy to control, you can achieve the vehicle
stepless speed regulation and freestyle, in the
construction machinery walking system has been a lot of
applications. At present, hydrostatic transmission
technology is mainly used in low-speed operation of
engineering vehicles, in multi-axis drive and high-speed
vehicles in the application of research is still blank, speed
control problems in driving lack of theoretical support.
2 Composition and working principle
The hydrodynamic drive vehicle has four hydraulic
pumps and 14 drive motors, which are driven in a fully
driven manner. Hydraulic drive vehicle unilateral driving
hydraulic and control system works as shown in Figure 1,
including the controller, the engine 1, the variable
hydraulic pump 2, the pressure sensor 3, the accelerator
pedal 4, the handle 5, cartridge valve 6 , An
electromagnetic directional valve 7, a safety relief valve 8,
a variable hydraulic motor 9, a speed sensor 10, and a
wheel reducer 11.
M
Controller
pi
ni
1
2
34
5
6
6
7
8
8
9
10
11
12
13
Figure 1. Schematic diagram of single-sided driving hydraulic
system
The engine 1 and the variable hydraulic pump 2 are
connected. The controller controls the engine 1 to drive
the variable hydraulic pump by detecting the signal of the
accelerator pedal. The hydraulic system is supplied to the
travel system. The hydraulic motor 9 is driven by
hydrostatic pressure. The wheel is driven by the wheel
reducer. The electromagnetic directional control valve 7
controls the flow of the hydraulic oil to change the
steering of the variable hydraulic motor and realize the
function of advancing and retreating the vehicle. The
hydraulic pump uses constant power control with
pressure cut off, adjusts the displacement of the variable
hydraulic pump according to the external characteristic
curve of the engine. The variable hydraulic motor 9 is
controlled by the electric proportional control. The
controller detects the gear signal of the gear position and
MATEC Web of Conferences 139, 00212 (2017) DOI: 10.1051/matecconf/201713900212
ICMITE 2017
© The Authors, published by EDP Sciences. This is an open access article distributed under the terms of the Creative Commons Attribution
License 4.0 (http://creativecommons.org/licenses/by/4.0/).
The European Physical Journal Conferences
the pressure of the hydraulic system. The magnitude of
the hydraulic motor coil is controlled to control the
displacement of the variable hydraulic motor.
3 Driving principle
Control of the drive section of the multi-axis hydrostatic
drive chassis drive includes control of the engine,
variable displacement hydraulic pump, variable
displacement hydraulic motor and associated solenoid
valves. The control schematic shown in Figure 2. By
adjusting the accelerator pedal stroke to adjust the engine
throttle opening to adjust the engine speed, according to
the engine's external characteristics curve to determine
the maximum power of the engine at each speed,
combined with the hydraulic system to determine the
variable displacement hydraulic pump target
displacement. Through the gear lever gear signal and
hydraulic system pressure variable displacement
hydraulic motor displacement, change the variable speed
hydraulic motor to change the vehicle speed.
Accelerator
Engine speed
Engine external
characteristics
Maximum power
of the engine
Variable displacement
of the hydraulic pump
System
pressure
Gear signal Variable displacement
of the hydraulic motor
Variable
hydraulic
motor
speed
Vehicle
speed
Figure 2. Schematic diagram of the operation of the hydrostatic
transmission vehicle
3.1 Power control system
Power control system is mainly on the engine control, the
engine has two engines, when traveling need to use two
engines; in the operation of the load when the need to use
an engine, priority use of the main engine, if there is a
fault available from Engine; two engines can be a
separate start-up, downtime; two engines share a single
accelerator pedal while driving. As shown below. The
engine speed is directly controlled by the accelerator
pedal in the cab. Both the master and slave engines are
equipped with KSM, and the bodywork can separately
control the engine speed regulation.
Main engine
KSM module
Secondary engine
Button start/stop
Key switch
Button start/stop
Accelerator
Figure 3. Power control system schematic
3.2 Hydraulic pump control
The hydraulic pump is directly connected to the engine,
the input speed, torque and engine output speed, torque
and power of the hydraulic pump are equal. The
displacement of the hydraulic pump for a single
parameter control, according to the engine changes set
the pump displacement, pump displacement and the
engine speed
n
.
)(nfq
b
(1)
Where
b
q
is the displacement of the hydraulic pump;
n
is
the speed of the engine.
The relationship is determined by the following figure:
q
n
maxM
n
max
n
max
q
Figure 4. Relationship between the displacement of pump and
engine speed
Where
0
q
is the minimum displacement of the hydraulic
pump,
max
q
is the maximum displacement of the hydraulic
pump,
0
n
is the engine idling,
maxM
n
is the maximum
torque speed of the engine,
max
n
is the maximum engine
speed.
Hydraulic pump control strategy shown in Figure 5.
Figure 5. Hydraulic pump control strategy
3.3 Hydraulic motor control
Hydraulic motor displacement According to gear, speed
and system pressure to calculate the displacement of the
motor at any time, the speed and force into a hyperbola
similar to the current vehicle speed calculated according
to the target displacement is:
v
vq
qm
maxmin
(2)
Where
m
q
is the displacement of the hydraulic
motor
v
is the speed of the vehicle
max
v
is the
MATEC Web of Conferences 139, 00212 (2017) DOI: 10.1051/matecconf/201713900212
ICMITE 2017
2
Title of the conference
maximum speed per file
min
q
is the minimum
displacement corresponding to each gear of the motor.
First, the motor displacement opening to the maximum,
and then according to the highest speed of each file to
determine the motor displacement, the motor
displacement from the maximum transfer to the
maximum speed corresponding to the displacement, and
then automatically adjust the motor displacement
according to the system pressure.
Set the motor to
full displacement
Initialization
Collect the stall signal to
determine the minimum
displacement of the motor
Reduce motor
displacement
Automatic adjustment of
hydraulic motor displacement
according to system pressure
Y
Y
N
System pressure
judgment
P>Pmax
Hydraulic motor minimum
displacement judgment
Pm>=Pmmim
N
Figure 6. Control strategy for hydraulic motors
3.4 Division of travel vehicles
Multi-axis hydrostatic transmission vehicles in the
transmission system without gearbox, the gear design is
based on the number of drive axles to determine the
number. When the vehicle is moving forward, the number
of axles is changed from 7 to 3, and the number of axles
is divided into five gears according to the number of
drive axles. Can be manual and automatic gear switch,
when the need to drive the number of less when the
corresponding turn off the displacement of the hydraulic
motor, let it in a zero displacement state, to improve the
speed of other drive hydraulic motor3.
4 Hydraulic pump control strategy
Braking system can be divided into three brake: brake
brake, parking brake and emergency brake. Brake brake:
mining brake pedal, the valve is closed, brake relief valve
and motor displacement by the brake pedal travel, slope
determined. Parking Brake: On flat road or on the slope,
the detection speed is zero and the parking brake is
started. This button does not really work. Emergency
brake: press the stop button, the engine flameout, the
pump displacement minimum, maximum motor
displacement, the valve closed, the pressure relief valve
has been the largest, parking brake start. Control flow
chart is as follows:
Y
N
Depress the pedal
whether the motor
speed is zero
Braking proportional
valvePWM=0
Valve in the middle
Braking proportional
valvePWM=f(a);
motorPWM=f(a)
Figure 7. Brake control flow chart
5 Conclusion
Based on the composition and working principle of
hydrostatic transmission chassis, this paper introduces the
control methods of hydraulic pump, hydraulic motor and
brake system.
(1)According to the engine's external characteristics of
the variable displacement of the hydraulic pump control,
the engine fuel consumption is the best;
(2)According to the driving conditions of the vehicle to
control the displacement of the variable hydraulic motor,
the torque required at the time of starting is large, and the
variable hydraulic control of the variable hydraulic motor
is used to maximize the displacement of the hydraulic
motor. Constant power control, regulation of hydraulic
motor displacement;
(3) Depending on the number of axle of the gear we have
been divided.
Acknowledgement
The article was supported by Special research project
of Shaanxi Provincial Department of Education (Grant
No. 14JK1134 ),Shaanxi Province Natural Science Basic
Research Project(Grant No. 2017JM5087 ).
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MATEC Web of Conferences 139, 00212 (2017) DOI: 10.1051/matecconf/201713900212
ICMITE 2017
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... Вопросы математического моделирования работы гидростатических передач в трансмиссиях транспортных машин освещены в работах [15][16][17][18][19]. Моделирование движения промышленного трактора с БДМП опубликовано в работе авторов [20]. ...
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