1 Introduction
The automotive PEPS system is rapidly becoming one of the most representative solutions in the wireless entry application of vehicles. The so-called PEPS is an abbreviation of Passive Entry & PassiveStart, which means a keyless entry and keyless start system, which uses advanced RFID wireless radio frequency. Technology and vehicle identification code recognition system have completely changed the development prospects of automobile security and anti-theft applications, and brought users a new convenient and comfortable driving experience.
The following will introduce and analyze this PEPS system that combines safety and comfort from the aspects of system function, working principle and system design and implementation.
2. Introduction to PEPS system
For a car equipped with a PEPS system, the driver can complete the operation of opening the door and starting the vehicle engine without pressing the remote control button on the smart key or inserting or removing the key into the lock cylinder, provided the smart is carried with you Press the key and press the trigger button on the handle or the one-button start button. In terms of anti-theft security of vehicles, the complex two-way identity authentication process between the smart key and the PEPS base station has also been substantially improved compared to the previous generation remote key entry (RKE) system.
3. Working principle and certification process of PEPS system
From the perspective of system functions, the PEPS system can be divided into two parts, the PE keyless entry part and the PS keyless start part, which represent the two stages of the driver before entering the vehicle and after entering the vehicle, respectively.
But from the perspective of the working principle of the system, the two are very similar. In simple terms, whether it is a PE or PS system, the relative position between the smart key and the body base station (ie PEPS ECU, hereinafter referred to as ECU) is detected by a low-frequency antenna, and high and low frequency signals (high frequency 433.92MHz, low frequency 125KHz) Establish effective two-way interactive communication between the ECU and the smart key, and decide whether to open the door lock (PE system) or start the vehicle engine (PS system) based on the ECU's identity verification result on the smart key.
In the above two-way identity verification process between the smart key and the ECU, low-frequency signal wake-up and high-frequency signal authentication are not only the key to determining the vehicle's anti-theft safety performance, but also one of the key elements that determine the performance of the PEPS system. The so-called low-frequency signal wake-up, taking the PE system as an example, means that when the driver gives the PEPS system a trigger signal, the ECU will switch from the sleep state to the working state, and send a key wake-up message to the smart key through the low-frequency antenna. After receiving this message through its own low-frequency antenna, it will verify the message through its own smart chip. If the verification result matches the data stored in the key, the smart key will be woken up; while high-frequency signal verification refers to After the smart key is woken up, it will send its own ID identification code to the ECU in the form of a high-frequency signal. If the ECU recognizes that this ID number matches the key code of its own system, it will send a verification to the smart key through a low-frequency signal Code, the smart key that received the verification code will encrypt the verification code through a specific jump code algorithm, and send the encryption result to the ECU through a high-frequency signal. The latter will send the received encrypted data to its own The calculation results are compared, if the two match, the corresponding operation command will be sent to the BCM through the CAN bus, after the latter completes unlocking the door lock or opening Operation box.
Although the above authentication process is very complicated, with the high-speed computing capability of the smart chip, the entire authentication process takes only a few tens of milliseconds in practical applications, so there is no feeling of delay for users. Figure 1 shows the working flow chart of the above authentication process.
4. Scheme design of PEPS system
The PEPS system designed this time includes the following components: PEPS ECU, BCM, smart key, electronic door handle, low-frequency antenna, one-button start button, electronic column lock and trunk button. The installation position of each component on the car body is shown in Figure 2. The basic functions and design principles of each component are briefly introduced below.
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