Application area: automated testing
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Challenge: For the characteristics of hybrid vehicles, the NI CompactRIO-based hybrid vehicle calibration system was developed. In the stage of gantry and vehicle commissioning, the calibration parameters of the vehicle controller can be modified online. In order to achieve the purpose of optimizing the performance of the vehicle.
Application: Develop this automated test system using National Instruments' CompactRIO real-time controller, Labview Real-Time, Labview FPGA, Labview RIO, and Labview Real-Time Application tools.
Products used:
Labview 8.5 Software Development Platform
Labview Real-Time Module
Labview FPGA Module
Labview RIO module
NI CompactRIO-9014 with 128MB
DRAM real-time controller
NI CompactRIO-9104 8-slot reconfigurable
Embedded chassis
NI 9853 2-Port High-Speed ​​CAN Module
Introduction
Hybrid vehicles combine the advantages of traditional and electric vehicles, and they have been widely developed as a relatively mature new energy source. Its vehicle controller (VCU) is used to realize vehicle energy management and power system control, and is the control center of the hybrid vehicle. The control parameters in the VCU are one of the key factors to achieve the performance of the hybrid vehicle, and must be optimized and calibrated accordingly.
Calibration of the vehicle's electronic control unit is a very complicated process, on the one hand due to the complexity of the operating conditions of the controlled system; on the other hand, there are many control parameters. The optimization of the operating parameters and control parameters of the electronic control unit requires the use of special tools for analysis and modification, thus the calibration system of the electronic control unit was born. The selection of the calibration system is related to the calibration quality, calibration time and calibration cost. Therefore, the selection of a perfect and applicable electronic control unit calibration system is one of the key factors for the successful development of electronic control systems. Based on the above factors, the NI CompactRIO system was selected, and the hybrid vehicle calibration system was developed on this platform. Its compact shape can be placed in any spare position of the car without affecting the vehicle space. The sturdy design makes it possible to drive in the car. The working condition can still be stable under the harsh conditions; the anti-interference measures can eliminate the influence of various disturbances on the system during the driving process; Labview graphical programming language frees engineers from complicated programming work and greatly shortens the development cycle. Built-in signal conditioning hot-swappable I/O modules increase system openness and flexibility, and engineers have access to the underlying hardware resources.
Hybrid car design
The single-axis parallel hybrid scheme studied in this paper is a moderate hybrid of pre-precursor
. After a large number of program selection and design, integrated engine, ISG motor, super capacitor and dual clutch components. The disc-type integrated ISG motor is directly installed at the output end of the crankshaft of the internal combustion engine. The rotor of the motor is directly connected to the crankshaft of the engine. The stator is fixed on the engine body. The motor replaces the flywheel and the original starter and generator.
The power of the hybrid system of this solution is mainly driven by internal combustion engine and driven by motor. The dynamic response of the internal combustion engine is slow, the torque output control accuracy is poor, and the motor instantaneous power drive response is fast, the torque output control precision is high, and the energy recovery efficiency is high. Therefore, the engine working condition is used to optimize the engine working conditions, and the idle stop and fast are established. Hybrid control strategy for starting, deceleration and oil cut, acceleration assist, motor power generation and deceleration braking energy recovery.
Advantages of the NI CompactRIO System
NI CompactRIO is a compact and rugged industrial control and acquisition system that uses ultra-configurable I/O (reconfigurable I/O, abbreviated as RIO) and FPGA technology for ultra-high performance and customizable functionality. It includes a real-time controller and reconfigurable FPGA chip for reliable stand-alone embedded or distributed applications; it also includes hot-swappable industrial I/O modules with built-in signal conditioning for direct sensor/regulator connection . This design makes the low-cost architecture open and allows users to access the underlying hardware resources.
FPGA (Field Programmable Gate Array) is a product of further development of programmable devices such as PAL, GAL, and PLD. Its logic function is completed by an array of logic cells arranged internally. The logic cell array internally includes three parts: a configurable logic module, an input and output module, and an internal connection. Engineers can implement software logic to reconfigure logic modules and I/O modules within the FPGA to implement custom logic.
FPGA technology has many advantages, including custom I/O hardware timing and synchronization, high reliability, digital signal processing and analysis. These advantages provide a flexible, low-cost solution for fast-growing automotive electronic test technology. FPGAs can be directly connected to digital and analog I/O, and can define different sample rates and triggers for each channel. Advanced signal processing and analysis of any sensor signal using FPGA technology. In many signal processing systems, the underlying signal preprocessing algorithm has to process a large amount of data, which requires high processing speed, but the algorithm is relatively simple and can be implemented by FPGA. In addition, it can be conveniently implemented on the FPGA for digital signal processing, fast Fourier transform, windowing and other signal processing and analysis.
System design
Hybrid vehicle calibration is different from traditional engine calibration. Due to the more complicated working conditions and environment, the stability of the calibration system has higher requirements. The final calibration hardware environment is shown in Figure 1. The communication master is composed of a portable PC and the NI CompactRIO system, and communication is completed by TCP/IP; the communication slave is the msCAN of the vehicle controller. The calibration method adopts CCP, a CAN bus-based vehicle calibration protocol, so the NI CompactRIO system is connected to the vehicle controller through the CAN bus.
Figure 1 calibration system hardware architecture
Hybrid car CAN network consists of four control units, including VCU-Vehicle Control Unit, Engine Management System (EMS-Engine Manage System), Motor Controller (MCU-Motor Control Unit), and information status. Display controllers (DPLY), all of which communicate via the CAN bus. When designing the whole vehicle CAN network, a node is reserved for the whole vehicle CAN network monitoring in the development stage, and the calibration system is also connected to the CAN network through the node to establish a connection with the vehicle controller VCU. The main control PC is the uppermost layer of the calibration system. It can monitor the CAN network data of the whole vehicle online, and modify the calibration parameters of the whole vehicle controller online, so as to control and manage the system. The CAN communication module uses the NI 9853 two-channel high-speed CAN acquisition module to collect the CAN network signal of the whole vehicle with a resolution of 25ns and supports 11-bit and 29-bit arbitrary IDs. This solution has the characteristics of high integration, saving equipment investment and calibrating. The working environment of the personnel has been simplified.
System software design
The software design of the hybrid vehicle calibration system fully considers the hardware characteristics of the CompactRIO system. The software programming mainly includes the underlying FPGA program, the RT program and the Host program of the host computer.
The underlying FPGA program implements data acquisition of each board, transmission of correction coefficients for each IO channel, and DMA transfer of data and RT. The RT program is responsible for communication with the underlying FPGA, the blinking of the RT system, the control of the user switch, the TCP/IP network communication with the host Host, the FTP data transmission, and the calibration, interpretation, and recording of the test data. The Host computer program is responsible for configuring the overall test system channel, communicating with the RT, and monitoring the specific channel of the acquisition board in real time, and viewing the data saved on the RT.
The entire software supports different sampling rates, supports CAN frame recording and conversion, and TDMS file format storage. The controller's data record is flashed through the front panel indicator, and data logging can be paused through the front panel custom switch. The system has expanded the U disk, and the data will be automatically stored in the U disk. After power off, just copy the data in the U disk to the host computer.
After the program running on the FPGA target is developed using the Labview graphical language, the program is compiled and the compiled file is downloaded to the FPGA chip. The RT program can be downloaded to the NI CompactRIO real-time system via the Labview Real-Time Application tool, so that the RT program will run automatically as soon as the system is powered up.
According to the basic functions of the calibration system, the host computer software is divided into the following modules: CAN communication control module, vehicle controller calibration module, CAN network data monitoring module. The main function of the CAN communication configuration module is to configure the CAN channel related information to drive the NI 9853CAN card for CAN data transmission and reception; most of the calibration is done under the vehicle controller calibration module, which is to be executed by the module. There are two tasks in general: reading the RAM area data, displaying it on the PC, and downloading the data to the RAM area. Figure 2 shows the calibration interface. The instructions in the calibration process are displayed on the front panel in the form of controls. When the user clicks on an instruction, the module should be able to receive the user's calibration instructions and start managing the corresponding thread. The main function of the CAN network data monitoring module is to process the vehicle CAN network message obtained by the CAN card, and finally display it on the monitoring interface. The CAN message obtained from the CAN card is still in the form of a data frame. In order to provide a friendly interface for the tester, it is necessary to convert between the decimal data and the binary data used in the controller, and in the application, according to each control. The ID number of the CAN message sent by the device is parsed and displayed on the front panel as intuitively as possible, enabling the developer to know the working status of the vehicle, engine and motor in real time.
Figure 2 calibration interface
in conclusion
There are many sources of interference during driving, such as spark discharge caused by motor brushes, electromagnetic signals generated by pulse switch contact in some circuits, and interference generated by various electrical equipment during operation. These noises have serious interference with the signal under test and the test equipment, which can cause large data acquisition errors. Therefore, the anti-interference ability of the acquisition equipment is particularly important. Through long-term real vehicle road test, the anti-jamming measures of the equipment can eliminate the influence of various disturbances on the system during the driving process, ensure accurate and reliable collection of vehicle CAN network data, and online calibration of vehicle controller parameters. Its real-time and reliability have been verified, which fully meets the requirements of the calibration test of hybrid vehicles, and plays a very important role in the control strategy debugging of hybrid vehicles.
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