ECU development and hardware in the loop test of A

  • Detail

ECU development of automotive ASR system and its hardware in the loop test

acceleration slip regulation system (ASR) is an active safety control system that prevents excessive wheel slip during vehicle starting and acceleration to obtain the best ground driving force and maintain directional stability. It is developed based on the promotion of the control principle of anti lock braking system (ABS) in driving conditions. With the gradual popularization of ABS system in automobiles, the application of ASR is also becoming more and more extensive. Therefore, the research on the control algorithm and controller development of ASR has become the current research hotspot []

asr requires a certain way to adjust the engine output torque. Due to the limitation of electronically controlled engine, most of the control theories of ASR system in China focus on the control method of braking control supplemented by engine control. In general, there is still a certain gap from commercialization [4]. Using engine output torque or electronic throttle adjustment is difficult to carry out experimental verification. In recent years, in order to further improve the accuracy of algorithm verification, semi physical simulation technology has been applied to a certain extent []

based on the in-depth study of ASR control requirements, this paper designs and develops ECU software and hardware. Using matlab/simulink software and dSPACE real-time simulation system, the hardware in the loop test of ECU is carried out, the ECU control parameters are calibrated, and the control effect is verified

1 ECU Hardware Circuit Design

asr ECU Hardware mainly realizes the functions of wheel speed signal acquisition and processing, storage and operation control software of steel plate less than 4mm thick after further cold rolling, driving electronic throttle motor and pressure regulator solenoid valve, and communicating with other ECUs or computers. Its hardware design framework is shown in Figure 1

ecu design also needs to comprehensively consider the following factors:

(1) real time of control program. The controller is required to run the program quickly and have high calculation speed

(2) controller reliability. To ensure that it has strong anti-interference performance in the harsh automotive electromagnetic environment, and the control program can run reliably and stably

(3) the volume and cost of the controller should have certain market competitiveness

1.1 selection of main and auxiliary MCU and minimum system design of single chip microcomputer

single chip microcomputer is the core of electronic control system ECU. It is responsible for data collection, processing and all logical operations, and directly affects the reliability of controller circuit operation, cost control and size of controller. In order to improve the reliability of ECU, this paper adopts dual MCU architecture. The main MCU is responsible for collecting the wheel speed signal, calculating and processing it, and then outputting the corresponding control command to the solenoid valve according to the control logic, so as to complete the expected function of ASR. Therefore, the safe and reliable operation of the main MCU is the guarantee of the reliability of the ASR controller. The main function of the auxiliary MCU is to monitor the main MCU and complete some fault diagnosis

the following factors are mainly considered for the selection of single chip microcomputer:

(1) the operation speed of single chip microcomputer: the abs/asr control logic needs to be converted in time from the reference speed estimation to the implementation of control algorithm, which involves many complex mathematical algorithms, so there are high requirements for the operation speed and operation ability of MCU

(2) sufficient storage space: complex abs/asr control logic, calculation and fitting of reference vehicle speed and gradually increasing fault diagnosis function will lead to the increase of software code, and a lot of memory space is also required when the program is running, which requires MCU to have sufficient storage space to meet the needs of the whole system. According to the previous experience of motorcycle abs/asr controller design, due to the limitations of on-chip integrated storage unit technology and cost, there is generally less storage space on-chip, which often requires users to expand through the address and data bus of MCU, which will lead to insufficient i/o interface of MCU, and external access will also affect the overall operation speed of MCU

(3) the number of i/o interfaces matching the system requirements: the abs/asr system designed in this paper needs to collect 4-channel wheel speed input signals, drive 4 groups (8-way) of solenoid valves of pressure control valves, and need to carry out a large number of fault diagnosis circuit design, so we must ensure a sufficient number of I/o ports

(4) the price factor, anti-interference performance of single chip microcomputer and the corresponding technical support of the chip manufacturer for this type of single chip microcomputer are also important considerations for the selection of single chip microcomputer

after considering the above factors, this design selects Freescale's HCS12 series 16 bit MCU mc9s12dp512 as the core control chip of the system. The main advantages of mc9s12dp512:

(1) it has strong computing power, rich i/o interfaces and abundant storage space. Its core operation speed can reach 50MHz and the bus speed can reach 25MHz, and the optimized instruction set is adopted, which greatly improves the operation speed of instructions [7]

(2) the phase-locked loop is used, and the industry discussion technology and internal frequency doubling technology are carried out, so that the internal bus speed is much higher than the frequency of the clock generator. At the same speed, the clock frequency used is much lower than that of Intel single chip microcomputer, so the high-frequency noise is low and the anti-interference ability is strong, which is more suitable for the harsh environment inside the car

(3) the internally integrated programmable filter function can effectively filter out the narrow pulse interference signal in the wheel speed pulse signal. The specific filtering principle is as follows: four buffered IC channels are integrated in mc9s12dp512, and each buffered IC channel has the function of delay filtering. When the delay function is started, an effective edge will be detected at the input pin (set as rising edge trigger in this paper), and then the delay counter starts to count P (clock module). When the preset count value is reached, the delay counter generates a pulse with opposite pin levels before and after the delay at its output end, so as to avoid reacting to narrow input pulses and effectively filter out this interference. In the filter function design, the delay time can be set and selected by inputting dly1 and dly0 of the delay control register dlyct

(4) it can work in BDM mode, which is convenient for program burning and debugging

after the single chip microcomputer is selected, the power circuit, clock circuit and reset circuit can be designed, which constitutes the minimum system of the single chip microcomputer

1.2 communication design between dual MCU

coordination can be completed only by communication between dual MCU. This paper designs SPI interface circuit to complete the communication function. SPI (serial peripheral interface) is a high-speed and efficient synchronous serial interface, which is mainly used to exchange data between MCU and external interface chips. By raising and lowering the slave selection (SS) pins respectively, set the master MCU as the master mode and the auxiliary MCU as the slave mode. SPI communication circuit is shown in Figure 2

1.3 design of wheel speed signal processing circuit

asr system has four wheel speed sensors. The sample vehicle is equipped with magnetoelectric sensors, and the output signal is a sine wave whose frequency is proportional to the wheel speed. In this paper, an enhanced capture timer is set to collect wheel speed signals. The wheel speed signal needs to be amplified, filtered and integer processed before it can be input into the single chip microcomputer. The amplifying and filtering circuit is shown in Figure 3. The sensor signal is input by in12, amplified by analog amplifier chip AD620, output, and then removed by RC filter circuit

after amplification and filtering, the signal must undergo level conversion (integer) to be effectively recognized by the single chip microcomputer. The signal conversion function circuit is completed by using the voltage comparison chip lm2901 produced by Philips company, and the circuit schematic diagram is shown in Figure 4. The amplified and filtered sinusoidal signal is generated by Lun_ Input comparators such as ch1 are compared with the corresponding port voltage, and finally converted into regular pulse signals that can be recognized and processed by ms9s12dp512, which are output by lun1

1.4 the rigidity of the executive liquid is relatively low. The design of the mechanism driving circuit

mcu analyzes and processes the input data of the wheel speed, and generates the corresponding output control signal according to a certain control logic judgment. The control signal must be driven and amplified before the executive mechanism can be controlled. The hydraulic ASR actuator consists of a pressure regulator with 12 solenoid valves and an electronic throttle DC motor. The operation of the DC motor is realized through the communication with the electronic throttle ECU, and the solenoid valve is driven by the ASR ECU

main functions of the driving circuit [8]:

(1) signal amplification: convert the TTL level output by MCU to the driving level required by the actuator, and amplify a small current, which is enough to drive the actuator

(2) electrical isolation: because most of the actuators are valves and motors, when they act, they need high current and the current changes quickly, which will also cause relatively large fluctuations in the power supply voltage and generate great interference. In order to protect other circuits and reduce the impact of these interferences on other circuits, the drive board should also achieve electrical isolation between the actuator and other circuits

(3) fault diagnosis: in order to be safe, the driving circuit should also monitor the working condition of the valve in real time. When there is a fault, it should be able to feed back the fault information to MCU in time, and then the MCU can identify and further deal with the fault

in this paper, the dual channel drive chip bts621 of Infineon company is selected to design the drive circuit. The specific work flow of the drive circuit is as follows: when the control signal pin ECU ch1 outputs a high level, the base of the triode 8050 is turned on, and chin1 is a high level output to the input terminal in1 of the drive chip; After being amplified by the driving chip, the signal is output by out1 to make the corresponding solenoid valve act. The solenoid valve drive circuit is shown in Figure 5

1.5 can bus interface circuit design

during ASR control, it is necessary to control the DC motor through the electronic throttle ECU to adjust the throttle opening, so as to achieve the purpose of adjusting the engine output torque. The control quantity is sent to the electronic throttle through the can[9] bus for control. Mc9s12dp512 is integrated with a can controller. In this paper, TJA1040 of Philips company is selected as the can transceiver. The specific can bus interface circuit is shown in Figure 6

2 ECU software design

ecu software mainly includes: system initialization module, system startup self-test module, wheel speed acquisition and processing module, reference speed calculation module, control decision-making module, solenoid valve drive module, fault diagnosis module. The overall process of the program is shown in Figure 7

system initialization mainly includes: MCU internal clock, wheel speed input channel port setting, actuator output channel port setting, watchdog timer setting, communication port initialization, system variables, etc., to ensure the normal operation of MCU

in order to ensure the safe operation of the system, the system should carry out self-test after reset and initialization, and carry out static detection on the key software and hardware parts of the system to judge whether the software and hardware of the system work normally

the wheel speed signal acquisition and processing module obtains the available wheel speed information through the wheel speed sensor

the reference vehicle speed calculation module calculates the current body speed and calculates the wheel slip rate together with the wheel speed, which is the main control basis of ASR control

the control decision module generates control instructions according to the vehicle state and the current control state. Control commands include throttle opening adjustment commands and solenoid valve operation commands. The throttle opening adjustment command is sent to the electronic throttle ECU through can to adjust the throttle opening. The operation instruction of the solenoid valve is output from the single chip microcomputer through the corresponding drive module, and drives the actuator after passing through the drive circuit

3 ECU Hardware in the loop test

in order to test the ECU developed, the first

Copyright © 2011 JIN SHI