Design Of Control System For The Automotive Shift

With the development of Automatic Transmission, the shift mechanism suitablefor which is replaced by electronic gearshift gradually. Electronic control can makeproducts simpler, more standardization,more modular and friendly. Automotive Shifttechnology has emerged in the development trend of automotive electronics.Compared with the traditional mechanical shift, electronic gearshift has manyadvantages such as more safe and reliable, convenient and efficient, and the shiftmechanism is also more agile, what’s more, it’s able to reduce shift mechanism’sattrition caused by the traditional mechanical structure and drivers’ misoperation so asto prolong its service life and save economic cost.The theory of Automotive Shift based on electromagnetic induction is thatpermanent magnets are installed under the gear lever or in their profile, meanwhile,inductive sensors on some hardware circuit board are equipped permanent magnets’opposite side. Positions of the permanent magnets are changed when shift lever moves,because of which, magnetic field produced by permanent magnets is also changed ona circuit board. That results in different outputs of the Hall sensors’, whichcorrespond to different gears. According to the requirements of some communicationprotocol, these gears signals are transferred to the transmission to deal with by CANbus or hard-wires so that they can reflect the driver’s shift gear intention correctly.Using the principle, the automotive shift with Automation/Manual seven gears isdesigned in this paper, including hardware circuit and software. Aiming at thefunctional requirements and technical indicators of the electronic shift system, itscontrol system adopts Freescale microcontroller MC9S12XDG128MALL as primarycontroller, as whose interior has many kinds of rich resources. The main task of themicrocontroller is responsible for handling gear signals inducted by switch Hallsensors, which are sent by CAN controller inside to intelligent fault chipUJA1065,then in accordance with communication protocol utilizing CAN bustransmits them to gearbox to process. In order to improve the property of the controlsystem, which adds three functions as follows. First, the system designselectromagnetic valve to limit the shift lever moves to the wrong direction, as resultof which decreases the wastage caused by misoperation. The system choosesBTS7700G and BTS428L2as electromagnetic valve’s drive chips, applying their lowpower consumption. Then selecting buttons as auxiliary gear shift to promote safety of Automotive Shift. At last, designing a set of light emitting diode(LED) devicedisplays gears to make drivers operate shift more conveniently. Considering thecontrol system must has high margin of safety,both during laying hardware circuitand programming software take some measures to prevent interference,thereforethe stability of the whole system has improved greatly.Finally, we carries out loading test about the Automotive Shift. The experimentresults show the control system is effective, complying with design requirements.