Study On Knock Control Module Based On Embedded Real-time Operating System

With the development of automotive industry, measures have been taken to improve the dynamic performance and fuel economy of automobile, now more and more attention has been paid to the security, stability and drivability of passenger cars, and at the same time, exhaust emission pollution, shortage of energy sources and other problems have been presented to the road of automotive industry during its development. Conventional control mode, based on mechanism system, is difficult to satisfy the requirements of the new control system, so electronic control system is introduced to solve these complex problems. After scores of years growing, electronic control technology has experienced a rapid progressing and has a broadly application in automotive, making cars seem like intelligent electronic control systems.In the aspect of vehicle engine control, it has been the trend for the new engine control technology to improve the engine performances, saving energy sources and meet the requirement of the more strictly emission regulations by using electronic control technology. At present, engine management system (EMS) has been a standard component of modern vehicle engine, but as the domestic automobile electronics industry is still at the beginning stage now, there is no our national companies command the core technologies and form our own brands. So it is necessary to strengthen the study of EMS, which is the kernel and linchpin of the automotive electronics control systems, for this can advance our level in this field rapidly.This paper aims at studying the real-time operation system and knock control module in EMS. There are three type of real-time operation system: background/foreground system, non-preemptive real-time operation system and preemptive real-time operation system. In this paper, we analyze the characteristics of these three kinds of operation system and the advantages and disadvantages of involving operation system in the control system. For the less control items and poor functions, there is no operation system in the early EMS and all the processes are performed by interrupts, so it is called background/foreground system. As there are more control variants and more complex function, the operation systems using by EMS smoothly move from background/foreground system to non-preemptive type, then to the preemptive ones with the more strong real-time performance.uC/OS-II is an open source code, high performance preemptive real-time operation system kernel, which acquired the security certification from American Federal Aviation Administration (FAA) and could be used in these control system, such as airplanes, spaceflight machines and so on. In this paper, we ported it to XC167CI, the main micro-controller of the EMS developed by ourselves, and then we finished compiling works with the help of tasking embedded development environment (EDE) from TASKING company, programmed a test program and verified that the whole system could running correctly on the evaluation board fromPHYTEC company.For EMS works on a special environment, the reliability of power module becomes especially important. Processing of the crank signal correctly is the fundament EMS working smoothly. So we also refer to these two questions in this paper. We take the powerful chip TLE4471 from INFINEON Company as the IC of battery module and get a solution for the module's overheat.Knock control module is one of the most important modules in EMS. It is the precondition of achieving closed-loop ignition angle control and can make the ignition angle as close as to the most optimization IGA, with which engine could release its total potential and get the best economic and dynamic performances. In this paper, we take HIP9011 as the knock IC, design the hardware structure of knock control module and realize the communication between knock control module and the main microcontroller through the serial peripheral interface (SPI). This module is controlled by five programmable command words, so it is very easy and convenient to program and it is could be used on all types of reciprocating engines.Following, we measure the knock signal on engine test bench and calculate the signal noise ratio (SNR) by analyze the output signals of knock sensor during knock cycles and without knock cycles, proving that it is possible to detect knock correctly (SNR>1.2) with non-resonance piezoelectricity knock sensor and the center frequency of knock signal is at 7-8 kHz.Then, we study knock control on test bench and analyze how to define knock control window, determine knock center frequency, adjust noise level without knock cycles and knock detection threshold, recognize knock cycle and correct ignition angle. The results prove that it is a good idea to choose HIP9011 as knock IC.Through studying knock control module, a conclusion is drawn for calibration knock module with an IC like HIP9011 and it could be taken as a reference when calibrate other modules. Of course, the calibration work of knock control module should only be done after calibration of some other modules have finished, such as intake air calculation, working condition determination and so on. Main steps as follow:(1) Verification of knock sensor position, ensure that the system knock sensor is sensing any incipient knock in all the engine's cylinders(2) Calibration of knock window to eliminate noises like valve noise, piston slap, etc.(3) Determining the knock input stage by defining the mid-band frequency and amplification required(4) Calibration of digital amplification(5) Calibration of digital filtering factors(6) Calibration of knock detection straight lines (threshold)(7) Calibration of ignition timing corrections(8) Other calibration works, as R/F correction, failure diagnosis(9) Verification of antiknock calibration...