| Calibration is the optimization of the system control parameters, but developers didn’t know the precise number of the control parameters at the beginning when an electric control system was developing, so initial values were set to ensure the normal function to come true; what’s more, there are many parameters need to be adjusted when the same electronic control system applied to different models or adapted to a variety of working conditions, so that a better performance can be achieved. Therefore, the process of calibration is indispensable in order to achieve the best performance of the electric control system. This paper offers an online calibration system based on the international calibration protocol CCP2.1, which has been successfully applied to the matching process of the ESP system. The results of vehicle tests show that this system can modify the parameters of the ECU in the RAM area in real time and update the calibration parameters from RAM area into the Flash memory area without loading the whole code each time. But most importantly, this calibration system greatly improved the ESP matching efficiency and shorten the development cycle.The following research jobs have been finished in this paper:Firstly, based on the profound understanding of CAN message 、 CCP command 、communication mechanism and data acquisition methods after an intensive study about CAN2.0 standard and CCP2.1 protocol, the overall realization method of this calibration system was worked out. The whole system was mainly composed of upper software CANape, USB-CAN conversion interface CANcase XL and ECU integrated with CAN drive and CCP drive, Infineon XC2365 A chip was used as ECU.Secondly, modular code design method was adopt in this paper in order to improve the portability of the program, so the bottom driver program was divided into CAN driver、CCP driver and Flash driver. CAN drive was configured in DAVE development environment according to the requirements of CAN2.0 standard, and executable C code was generated in the end. CCP driver model was established using Smulink/Stateflow based on CCP 2.1, and CAN drive interface function calls CAN send and receive function to realize the sending and receiving of CCP command. Finally CCP Driver C code was generated automatically by MATLAB RTW module. Flash drive was developed using flash module operation command sequence to achieve erasing and programming of data pages.Then, CAN driver, CCP driver and flash driver were integrated into the ECU step by step in order to avoid errors based on the TASKING development platform, and each module was tested with test cases, which shows the great advantages of the modular code design methods. The beginning 4kb flash area which begins with 0x C3F000 was settled as calibration parameters area, the 4kb area in the RAM which starts with 0x A000 was served as the mirror area. Copy the parameters of flash area into the RAM area before the main function is running, then use the CANape to change the values of parameters in the RAM, once the calibration parameters were certain, flash operation relevant functions will be called to copy these calibration parameters from the RAM into flash memory area.Finally, the proposed online calibration system was proved very useful and effective by ESP matching tests, such as ABS braking tests on the high/low adhesion road or split-u road and TCS acceleration test on the split-u road. Compared with these two groups of data before and after calibrating in each test, it’s easy to find that the successful development and application of calibration system greatly improved the efficiency of ESP matching process. |
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