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International Journal of u- and e- Service, Science and Technology
Vol.8, No. 8 (2015), pp.103-110
http://dx.doi.org/10.14257/ijunesst.2015.8.8.11
ISSN: 2005-4246 IJUNESST
Copyright ⓒ 2015 SERSC
Research on the Electric Vehicle Control System
Haiying Wang, Tianjun Sun, Xingbo Zhou and Qi Fan
School of Automation, Harbin University of Science and Technology, Harbin,
China
E-mail: wanghy@hrbust.edu.cn
Abstract
With the development of electric vehicle electronic control unit (ECU) for vehicle
control technology and the key to raise the level of design electric vehicles the
optimization control of the vehicle performance as direction. In order to achieve the
rational, coordination of vehicles within the system of integrated control, based on the
modular thought, through constructing the distributed control network design overall
structure of the control system of pure electric vehicle, the vehicle controller is analyzed
on the working principle and its function realization degree, as a pure electric vehicle
control system provides the theory basis for performance evaluation.
Keywords: Electric vehicles, Vehicle control system, Vehicle controller
1. Introduction
Modern electric car research and development is based on the theory of modern control
technologies, including automotive technology, motor driver technology, power
electronics technology and energy storage technology, etc.
The design process of the electric car three major problems need to be solved, are
respectively the vehicle technology, electric drive technology and energy management
system. Among them, the vehicle technology includes two aspects: one is the vehicle
body technology, mainly by reducing electric car body weight, to realize the acceleration
and grade ability and effectively increase the limited driving distance; Secondly, the
vehicle control system integrated control technology, mainly for reasonable arrangement
and coordination of the electronic control unit (ECU) for electric vehicles, save material
and reduce cost, realize the system optimization of multiple factors in the process of
optimization, improve the vehicle performance [1].
In traditional fuel vehicle, the engine management system (EMS) to make car engine in
all under the condition of low pollutant emission control, improve fuel economy and
excellent driving performance; For pure electric vehicles, it shall replace the original
motor engine, with power battery instead of fuel oil ACTS as a source of power,
therefore, pure electric vehicles also need a travel distance to increase its vehicle
management system, optimizing the allocation of energy. And the vehicle control system
has a significant influence on vehicle driving performance, is the important content of
pure electric vehicle control technology research [2].
2. The Analysis of System Design Requirements
At home, the research of pure electric vehicle control technology is more preference
for engineering application; Abroad, the research towards more braking energy recycling,
of the electronic control unit (ECU) for the traction control and stability control.
Because of pure electric vehicle control system integration of electrical, electronic,
mechanical, chemical and other nonlinear dynamic system, complicated structure, which
includes motor, converters, power battery, transmission, and other electric control
International Journal of u- and e- Service, Science and Technology
Vol.8, No. 8 (2015)
104 Copyright ⓒ 2015 SERSC
equipment, so, no matter how electric cars other assembly performance in good condition,
once there was a problem in the vehicle controller, electric vehicles will not be able to run
normally, cannot achieve energy recovery control, or even an accident. On how to
coordinate all parts of function units, make it reasonable and efficient for work of pure
electric vehicle controller is a very thorny problem in the design process?
Based on the research status of the vehicle control system at home and abroad, in view
of some problems in the process of vehicle control technology, the paper builds the
vehicle control system overall frame, the vehicle controller is analyzed on the working
principle, ultimately determine its functions.
3. The Construction of Vehicle Control Network
Vehicle Controller as a pure Electric Vehicle Control Unit, through the electronic
Control Unit to collect real-time dynamic parameters of the controlled object and
feedback, and then through the CAN bus is passed to the core Controller for operation
analysis, and then by the VCU to ECU Control instruction, make the reasonable
coordination of efficient performance of ECU, realize the Control of the Vehicle drive
performance and energy management, optimization, to ensure the Electric performance.
In general, the realization of the function of the pure electric vehicle controller scheme
has two kinds: centralized control and distributed control, as shown in Table 1.
Table 1. The Realization of the Function of Electric Vehicle Controller
Scheme
control method
advantages
disadvantages
Centralized control
By the core
processor to
complete the
processing of signal,
energy data and
distribution of work
deal with
concentration
high implement
fast response
low cost
PCB complex
bad heat dissipation
Distributed control
By the core
controller through
field bus and
communication
electronic control
unit (ECU) for each
modular
low complexity
flexible
configuration
high cost
complicated structure
Because the CAN bus car traffic more and more used in distributed control system, and
combining the Table 1 provided two kinds of control scheme of the analysis, this study
adopts the distributed control system based on CAN bus, in the process of pure electric
vehicle controller control, for the ECU by CAN bus communication and control.
Distributed control system based on modular construction; improve the correlation
between each subsystem of the vehicle. The system can be divided into two layers: the
whole car controller and the secondary controller. As shown in Figure 1, among them, the
whole car controller (VCU) as the top processing information and publish the
instructions, the secondary controller in the Motor controller vehicle combination
Instrument and Battery Management System as the subsystem of the independent
Management and monitoring of the respective Control object. Real-time state parameter
subsystem at all levels will be collected by CAN bus to realize sharing information
exchange to VCU, then by VCU information comprehensive, at all levels to implement
the controller between the centralized and decentralized control, information interaction
function [3-4].
International Journal of u- and e- Service, Science and Technology
Vol.8, No. 8 (2015)
Copyright ⓒ 2015 SERSC 105
Figure 1. Hierarchical Control System Schematic Diagram of the Vehicle
4. The Summary of the Electric Vehicle Control System
As shown in Figure 2, pure electric vehicle dynamic control system can be divided into
three parts, respectively for the vehicle control system, motor drive system and power
supply system. The core of the whole vehicle control system is vehicle control
technology, the technology including vehicle structure design of control software, control
strategy and energy management. At the same time, the vehicle controller as an
objectively reflect the actual development of single chip micro control system for vehicle
control technology, electronic control unit as a measure of the core component of the
vehicle control system performance and function level, its function realization degree
directly affect the control effect of the control system of the vehicle, has become one of
the evaluation criteria of vehicle controller performance is good [5].
Figure 2. Pure Electric Vehicle Dynamic Control System Structure
Vehicle controller as a pure electric vehicle control system is the most important core
part, is responsible for the overall control, coordination and monitoring vehicle running
state, the operation of the pilot signal and the signal from the sensor via the control
strategy, inherent to the vehicle controller to the electronic control unit, energy
management, fault diagnosis and the vehicle running state control, monitoring, and other
functions, and through the LCD automotive instrument display. Therefore, to develop
fully functional vehicle controller, improve the design of the control system of electric
vehicle. The vehicle controller diagram is shown in Figure 3 [6-8].
International Journal of u- and e- Service, Science and Technology
Vol.8, No. 8 (2015)
106 Copyright ⓒ 2015 SERSC
Figure 3. Vehicle Controller
5. Working Principle of the Control System for Vehicle
Figure 4. Vehicle Controller Works
The vehicle control system is a closed-loop control system, artificial according to
perform a task hierarchy can be divided into three layers: policy makers, formed by the
driver itself; Coordination layer, based on the vehicle controller processing real-time
status information and control instructions for the operation attempt of driver is
reasonable judgment; Executive level, handle relevant control instruction made by vehicle
controller. In order to improve the safety of the vehicle control system stability, rely on
International Journal of u- and e- Service, Science and Technology
Vol.8, No. 8 (2015)
Copyright ⓒ 2015 SERSC 107
the system control error feedback correction. Working principle of the whole vehicle
controller is shown in Figure 4.
Pure electric vehicle charging is accomplished by charging equipment on the ground,
when the driver use the key to start switch, power battery to the signal through the
DC/DC converter, instrument and low voltage electrical equipment such as power supply
for lighting. At the same time, through the vehicle controller also supply power to the
motor controller, dc inverter motor controller as three-phase alternating current for the
motor running, and then through the transmission, the rotation axis, differential and rear
axle drive vehicle. The vehicle controller can be realized by controlling the motor of the
vehicle to realize forward or backward.
When the vehicle is started, the driver will first block a choice in the "forward" or
"backward" position, and then stepped on the accelerator pedal () on the accelerator.
When the accelerator pedal off after the initial position, the driver can be done by
changing the accelerator pedal opening of driving torque given value change, namely
when the accelerator pedal opening (exactly) the accelerator, the largest drive torque
given value most; When the opening of the accelerator pedal is minimum, throttle back in
situ, drive torque given minimum value. When the motor controller receives the control
signals and drive torque given value, the energy flow to the motor, the control of its
operation, and according to the control signal to determine motor rotation direction, at the
same time, according to the given value driving torque signal to determine the magnitude
of torque.
Pure electric vehicle braking mode is divided into two kinds: emergency braking and
emergency braking. The former generally rely on mechanical braking system for brake;
The latter usually by mechanical braking and regenerative braking of motor brake.
According to the scene environment condition, when need to use smaller braking
intensity, the braking system will be given priority to with regenerative braking,
mechanical brake is complementary; When with the secondary braking intensity, the
braking system will be given priority to with mechanical braking, regenerative braking is
complementary.
When the driver on the brake pedal brake (start), brake pedal deviates from the initial
position, motor controller will combine control signals, brake level and braking torque
values given three indicators to control the power of the motor brake state, and based on
the brake torque values given signal to determine the size of the motor output brake
torque, at the same time open the regenerative braking, to power the battery. When lift the
brake pedal brake (cancelled), braking state signal disappears, the braking torque given
value also recover (0), then the output of the motor controller to stop brake torque. When
vehicles run on deceleration mode, the motor ACTS as a generator converts kinetic
energy into mechanical energy to power the battery in order to realize the trip range of
pure electric vehicles increased [9].
6. The Main Function of Electric Vehicle Control System
Vehicle controller as the core of pure electric vehicles controllers, operation and
management of the vehicle and each relevant ECU control plays a vital role. As a result of
the different control function of the electronic control unit for each part, the original
complex control system can be decomposed into relatively simple single subsystem, and
then based on the modular thought clear a small part of each module can realize the
function.
On the one hand, it received by the sensor transmits data and instructions by the
driver's psychological intentions, and in accordance with the control strategy for
processing and analysis, then send control commands to the motor control unit, battery
management system and the car instrument cluster control unit, at the same time, the
vehicle running status real-time monitoring; On the other hand, in the process of pure
electric vehicle brake control of braking energy feedback, and then improve the travel
International Journal of u- and e- Service, Science and Technology
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108 Copyright ⓒ 2015 SERSC
distance of pure electric vehicles. Electronic control unit of vehicle controller use CAN
bus and other data information to transfer the control instructions. Vehicle controller is
regarded as the center of the vehicle communication network nodes, to improve data
transmission rate and improve the reliability.
The vehicle controller to realize the main functions are:
(l) Drive torque control
Driving moment of the control, as the most basic, the most important function of the
whole vehicle controller, the pedal through gathering information, and then parse the pilot
operation intention, to realize the transformation of the demand for motor output torque.
In this process, the driver by manipulating the accelerator or the brake pedal to realize
signal input, also is the purpose of the will be the driver's operation in the form of a signal
transmitted to the vehicle controller, then through analysis after processing by motor
vehicle controller according to the output driving moment or braking torque drivers
psychological intentions.
(2) The braking energy optimization control
Compared to pure electric vehicles and the traditional energy vehicles, the main
difference is that one of the braking energy recovery. Motor as the only power output and
has function of motor and generator two - when the driver steps on the gas pedal drive
vehicles, motor function is equivalent to the motor; On the contrary, when the driver on
the brake pedal to slow down when driving, the function of the motor is equivalent to the
generator, also is to take advantage of the electric car braking energy power generation
and storage to the energy storage device, when meet certain conditions, and the energy to
the battery pack. In this process, the vehicle controller based on the accelerator and brake
pedal opening and the current speed and power battery charged State (State of Charge,
SOC) to determine whether braking energy recovery at a certain moment, if you can, the
vehicle controller issue related to the motor controller instructions, recycling part of the
braking energy, improve energy utilization efficiency.
(3) The vehicle energy management
In the process of pure electric vehicles, electric supply system as the only power supply
unit in addition to the drive system power supply, but also to similar to the motor, air
conditioning and other automotive electronic control unit power supply. In order to
extend the range of pure electric vehicle, the vehicle controller can to reasonable
optimization of energy, when the battery power is low, the vehicle controller will send off
part of the supplementary electrical equipment control instruction, so as to ensure the
safety of electricity used in vehicles, thus improving the utilization ratio of energy,
(4) CAN the maintenance and management of the network
Vehicle controller as the master node of communication network, also manages the
vehicle network, the communication network based on CAN bus technology, has a
number of master-slave node, real-time vehicle network state regulation, and has the
priority of information dynamic allocation.
(5) Fault diagnosis and processing
Vehicle controller can continuous real-time monitoring of vehicle running status,
including the parts EUD working condition, once the malfunction of the electronic control
unit first timely alarm, security measures at the same time, then the fault diagnosis, store
and send the error code, provide the basis for the future maintenance and routine
inspection car, in the end to the problem of fault classification processing, and for those
who do not influence the operation of the vehicle glitches, to maintain the vehicle's
moving.
(6) The vehicle condition monitoring
Vehicle controller based on on-board instrumentation control to display the real-time
operation state of the vehicle information, to make drivers know vehicle state. Vehicle
condition monitoring technology based on CAN bus communication for motor speed,
speed, battery remaining power, running state parameters such as current, and the above
data through the car instrument cluster intuitive display, improved the car interactivity
International Journal of u- and e- Service, Science and Technology
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Copyright ⓒ 2015 SERSC 109
between drivers and vehicles, at the same time as the driver accurately grasp the overall
vehicle operation condition to provide convenient conditions [10].
7. Conclusion
Pure electric vehicle controller as the core component of the vehicle control system, the
moving car, driving moment control, optimization and control of braking energy, the
energy of the vehicle management, the CAN network maintenance and management, fault
diagnosis and treatment, the vehicle condition monitoring functions such as the
implementation of the degree plays a key role.
This paper firstly introduces the composition of pure electric vehicle control network,
and using distributed control system is determined, and then through the vehicle
controller schematic overview of its system structure, and then describes in detail the
working principle of the vehicle controller, finally put forward the vehicle controller can
realize the function, as to provide theoretical basis for the further research and
development and performance evaluation.
Acknowledgements
This paper is partially supported by Technological Innovation Foundation for Leaders
of Disciplines in Science of Harbin (2014RFXXJ032).
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