1 Introduction
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The automotive PEPS system is rapidly becoming one of the most representative solutions in the wireless access application of vehicles. The so-called PEPS is the abbreviation of Passive Entry & PassiveStart, which means keyless entry and keyless start system, which uses advanced RFID radio frequency. The technology and vehicle identity code recognition system has completely changed the development prospects of the car security anti-theft application field, and brought a new and convenient driving experience to the user.
In the following, we will introduce the PEPS system that analyzes the safety and comfort of this system from the aspects of system function, working principle and system design.
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 the key into the lock cylinder. Key and press the trigger button on the handle or a button to activate the button. In terms of vehicle anti-theft security, 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 of the remote key entry (RKE) system.
3. The working principle and certification process of PEPS system
From the perspective of system function, the PEPS system can be divided into two parts, which are divided into PE keyless entry part and PS keyless start part, which represent the two stages of the driver before entering the vehicle and entering the vehicle.
But from the perspective of the working principle of the system, the two are extremely similar. Simply put, whether it is PE or PS system, the relative position between the smart key and the body base station (PEPS ECU, hereinafter referred to as ECU) is detected by the low frequency antenna, and the high and low frequency signals (high frequency 433.92MHz, low frequency) are adopted. 125KHz) Establish an effective two-way interactive communication between the ECU and the smart key. Determine whether to open the door lock (PE system) or start the vehicle engine (PS system) according to the ECU's identity verification result on the smart key.
In the two-way authentication process between the above-mentioned smart key and ECU, low-frequency signal wake-up and high-frequency signal authentication are not only the key to determining the anti-theft security performance of the vehicle, but also one of the key elements determining 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 a trigger signal to the PEPS system, the ECU will switch from the sleep state to the working state, and send a key to wake up the message through the low-frequency antenna to the smart key, when the key After receiving the message through its own low-frequency antenna, the message will be verified by its own smart chip. If the verification result matches the data stored in the key, the smart key is awakened; and the high-frequency signal verification refers to After the smart key is awakened, it will send its ID ID code to the ECU as a high-frequency signal. If the ECU recognizes that the ID number matches the key code of its own system, it will send a verification to the smart key through the low-frequency signal. Code, the smart key that receives the verification code will encrypt the verification code through a specific jump code algorithm, and send the encryption result back to the ECU through the high frequency signal. The latter will receive the encrypted data with 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, and the latter can unlock the door lock or open the backup.
Although the above authentication process is very complicated, with the high-speed computing capability of the smart chip, the entire authentication process takes only tens of milliseconds in practical applications, so there is no feeling of delay for the user.
4.PEPS system design
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 following is a brief introduction to the basic functions and design principles of each component.
4.1 PEPS ECU
PEPS ECU is the abbreviation of Electronic ControlUnit, which means electronic control unit. It is the core component of PEPS system. Its function is to identify the smart key. If the key is legal, the corresponding operation command is sent to BCM or EMS through CAN bus. Both perform subsequent operations; if the key is illegal, the ECU enters sleep mode and rejects subsequent requests sent by the key.
4.2 BCM
BCM is the abbreviation of Body Control Module, which means the body control unit, which is a control module that integrates body lights, doors, windows and anti-theft functions. In the PEPS system, the BCM is connected to the ECU through the CAN bus, and the control of the doors, windows and lights is completed according to the instructions provided by the latter.
4.3 Smart Key
The smart key establishes high and low frequency two-way communication with the ECU during work. After passing a series of identity authentication, the door can be unlocked or the engine can be started. Throughout the process, the driver does not need to do anything with the key and just carry it with him, which is also the name of the keyless system.
4.4 Electronic door handle
The electronic door handle has a built-in low frequency antenna and a jog (or induction) switch. The antenna is used to detect the key position. The switch is used to wake up the PEPS system and switch it from sleep mode to working mode.
4.5 Low frequency antenna
The low-frequency antenna can transmit a low-frequency signal of 125KHz to a spherical space with a radius of 1.5m, which is used to detect the relative position between the smart key and each low-frequency antenna, and transmit the measured key coordinates to the ECU. Based on the current coordinate value of the key, it is determined whether to perform the operation of opening the door and starting the vehicle engine.
4.6 One button start button
The ignition device is cycled between ACC, ON, START and OFF by the key action and the current working state of the brake (automatic gear) or clutch (manual gear). The one-button start button eliminates the need for the driver to insert the key into the ignition lock cylinder and then reverses the key to activate the engine, greatly simplifying the driver's operation.
4.7 Electronic column lock
The electronic column lock realizes the locking/unlocking function of the steering column by the telescopic movement of the built-in small motor drive bolt. Since the small motor that controls the movement of the bolt is controlled by the PEPS system, the electronic column lock is safer and more reliable than the traditional mechanical column lock in terms of safety.
4.8 trunk button
Pressing the trunk button, the low-frequency antenna mounted on the rear bumper position will detect the current position of the smart key. If the unlock condition is met, the PEPS ECU will command the BCM to unlock the trunk, simplifying the driver's insertion and unlocking of the key.
5. Implementation of area detection and key location technology for PEPS system
The PEPS system has three detection and judgment areas, which are gray exterior areas, red interior areas, and gray-white main driving areas.
The gray exterior area has three sections, which are divided into main driving, auxiliary driving and trunk detection areas. When the driver carries the smart key to enter these areas and gives a trigger signal, the ECU will establish high and low frequency two-way communication with the smart key, determine the current position of the smart key through the field strength detection of the low frequency signal, and then pass the high frequency of the key feedback. The signal verifies the identity of the key to determine whether to unlock the door or the trunk; the red in-vehicle detection area is the focus and difficulty of the entire PEPS system design. This is because the PEPS system needs to accurately determine whether the smart key is in the car. Whether the locking state of the door is correct and whether the engine can be started, both of which are closely related to driving safety, so the performance of the area will directly affect the performance of the PEPS system; In the model, the PEPS system also detects the gray-white main driving area, redundantly determines whether the key is valid, and whether the main driving position is there to avoid potential safety hazards such as child misoperation.
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