With the growth of car ownership, the issue of car security and theft is becoming more and more important. Most cars now implement the anti-theft alarm (anTI thief alarm, abbreviated ATA) function, which is mainly to determine whether there is illegal entry [1] by ultrasonic detection, and then start the sound and light alarm. This method can effectively detect illegal entry, but there is also the possibility of false positives, which brings great trouble to the surrounding environment. In the integrated body controller designed by the author for a certain car model, it can comprehensively judge whether it is safe to lock the car, whether it is violently entered, and whether it is illegally ignited by detecting the unlocking action, ignition state, body state and anti-theft state, so as to achieve safe lock and anti-theft Alarm function, this article first introduces the working principle of the anti-theft alarm unit (hereinafter referred to as ATA) and the design of its state machine, and then introduces the mechanism of sound and light warning, safe lock of the car and its software implementation.
How ATA works:
An effective ATA unit needs to correctly trigger the alarm warning action, and at the same time avoid the inconvenience caused to the user by false triggering the alarm. This is achieved by judging whether it enters the vehicle normally and ignites normally.
First, when locking the car, the user is prompted to lock the car safely through the horn and turn signal, only when the four doors and two covers (four door switches, bonnet switch, trunk switch) are all closed and the ignition signal is invalid can it be safe Lock the car. Enter the anti-theft state after safety lock, monitor the status of the four doors and two covers and the ignition signal [2], if the door or trunk or engine cover is opened without unlocking action, it is considered to be illegal entry, if detected If the ignition signal is valid, it is considered to be illegal ignition. At this time, the audible and visual alarm is activated through the horn and the turn signal to perform the unlocking action or detect the ignition key ON / OFF switch twice within 5 seconds, and stop the alarm and return to the normal state. The ATA structure is shown in Figure 1:
Figure 1: Schematic diagram of ATA structure
Figure 1: ATA Structure SchemaTIc
The ATA unit performs the door lock control under the key lock and unlock action, and realizes the jump of the anti-theft alarm state in the form of a state machine. At the same time, it accompanied some warning actions to remind the user of the current body state. Analyze its jump, describe the process of state jump, and then describe the design of the body state warning action.
ATA state machine design:
According to the use of the car and the needs of security and anti-theft, the following states are designed: normal state NORMAL, anti-theft state SECURITY, waiting to exit the anti-theft state QUIT_SECURITY, alarm state ALARM, the normal state corresponds to the state of the car being used normally, and the anti-theft state corresponds to the safety lock car In the latter state, waiting to exit the anti-theft state is an intermediate transient state. Corresponding to the situation in which the user unlocks the car door without opening the anti-theft state, the alarm state corresponds to the state of illegal entry or illegal ignition. The following describes the jumps of these four ATA states in the form of state machines. The state diagram is shown in Figure 2:
Figure 2 ATA status diagram
Figure 2: ATA State diagram
Under the condition that the four doors and two covers are fully closed and the ignition signal is invalid, the key is remotely locked or the front door is locked, and the ATA enters the SECURITY state. At this time, the monitoring of the body state and the unlocking action is started; the four doors and two covers are detected to be open in the SECURITY state Or the ignition signal is valid, enter the ALARM state, then start the audible and visual alarm, unlock in the SECURITY state, enter the QUIT_SECURITY state; QUIT_SECURITY is an intermediate transient state, it lasts for up to 20s, and automatically locks out and enters the SECURITY state again when it times out. It can prevent the user from accidentally pressing the remote control to unlock the safety problem, if the door is opened during this period, it will enter the NORMAL state; in the ALARM state, after one cycle of alarm, the four doors and two covers are fully closed and the ignition signal is invalid, return The SECURITY state can also enter the normal state by unlocking or switching the ignition signal ON / OFF twice within 5S. The specific code design is not repeated here.
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