Automobile body controller functions and strategies

The body controller is not very famous, but its management functions are spread throughout the car. It is mainly used to enhance the safety, comfort and convenience of the car, as well as to connect with the outside of the car.

The functions of the body controller mainly include lighting control, wiper control, door and window control, rearview mirror control, PEPS, seat control, etc. The figure below is a topological diagram of the body controller of a certain OEM, which shows the diversity of the body controller's functions more directly.

Functional topology diagram of the body controller

01.

Body controller functions and strategies

The software block diagram of the body controller is shown in the figure below. It is mainly written based on the AUTOSAR architecture, and most of the functional strategies of the body controller are implemented in ASW.

Body Controller Block Diagram

1 Internal and external lighting control

Internal and external lighting control mainly includes high and low beam control, turn signals, hazard warning lights, daytime running lights control, front and rear fog lights control, brake lights control, internal ceiling lights control, keyhole lighting control, etc.

The turn signal lamp mainly consists of the left turn signal lamp, the right turn signal lamp, the left turn indicator lamp, and the right turn indicator lamp. The turn signal lamp flashes at a frequency of 85±10 times per minute when working. The time of lighting and extinguishing is the same. The left turn indicator lamp and the right turn indicator lamp are sent to the instrument through the CAN network.

Its functions are summarized as follows:

1) When the key is in the ignition switch ON position, the corresponding turn signal light flashes or turns off when the turn switch is turned on or off, and at the same time triggers the turn signal light on the instrument panel to flash at the same frequency or turn off the indicator light;

2) When the turn signal switch is turned to the left or right, the BCM drives the corresponding turn signal to activate and flash at least 3 times

3) If the turn signal is turned off after being activated, the turn signal will turn off immediately after completing its initial minimum 3 flash cycle.

4) If the turn signal switch is moved from left to right after the left turn signal is activated, the left turn signal will immediately turn off and the right turn signal will immediately turn on.

5) If the turn signal switch is moved from right to left after the right turn signal is activated, the right turn signal will immediately turn off and the left turn signal will immediately turn on.

6) Hazard warning lights include all turn signals, which can be driven to sound the alarm when the key is in any gear. The hazard warning light switch is a self-locking switch.

7) When the ignition lock switch is ON, the working priority of the turn signal and warning light is post-operation priority, as follows: If the turn signal is in working state and the warning light switch is turned on, the warning light will replace the working of the turn signal until the warning light switch is turned off, and the system will return to the working state of the turn signal; If the warning light is in working state and the turn signal is turned to the left or right, the turn signal will replace the working of the warning light until the turn signal output is turned off or the ignition state changes from ON to OFF, and the system will return to the working state of the warning light.

8) If a collision signal is received, all lights will work in the warning light state for at least 5 seconds. After 5 seconds, pressing the warning light switch again will turn off the flashing of the warning light. This is to prevent the warning light switch from being pressed due to a collision. If the hazard warning light switch is not pressed, when it is detected that the ignition switch is turned from ON-OFF-ON; the collision is resolved, the warning light resumes normal operation.

9) When the turn signal lamp reports a fault due to a short circuit to ground or overload, the short circuit status will be recorded in the memory through the relevant DTC, and the high-side driver chip of the turn signal lamp on that side will be immediately turned off, and the turn signal lamp on the instrument cluster will also stop. If the turn signal lamp is turned on again during this ignition cycle and the corresponding operation is not performed, the ignition cycle must be restarted before the output can return to normal.

10) When working in the turn signal working mode, if a turn signal on one side reports a fault due to an open circuit or short circuit to the power supply, the open circuit state will be recorded in the memory through the relevant DTC, and the turn signal on that side will flash at double the frequency (170±20 times/min), and the combined instrument turn indicator will also flash at double the frequency. When the ignition key is turned from ON to OFF/ACC, and then from OFF/ACC to ON, the output returns to normal, or in this ignition cycle, when the open circuit fault is eliminated, it can also return to normal frequency flashing

Brake light control function:

1. When the brake switch is valid, or the brake request on the bus is valid, the brake light and the high-mounted brake light need to be turned on, and the brake light and the high-mounted brake light need to be controlled separately.

2. The brake light and high-mounted brake light have two control paths, namely hardware switch control and MCU control. Under normal circumstances, both can be triggered. In limp mode, the brake light and high-mounted brake light should be able to be controlled by the brake switch.

Keyhole lighting control function:

1. When the ignition signal is OFF, the keyhole light will light up when the driver's or passenger's door is opened. When the door is closed, the keyhole light will turn off after 10 seconds. If the door is not closed, it will stay on for 10 minutes.

2. When the ignition signal is ON or START, the key hole light goes out immediately.

Keyhole lighting timing

2 Wiper system

BCM controls the wiper motor and water spray pump by monitoring the status of the wiper switch and the combination switch to realize various working modes of the wiper system: front wiper low speed operation, front wiper high speed operation, front wiper intermittent operation, front wiper off, front windshield spraying, rear wiper operation, rear windshield spraying, etc.

Some of the wiper controls mentioned above are achieved by the driver manually turning on a switch with different gears, while others are achieved by using an optical rain sensor to automatically identify the rainfall to control different working modes of the wiper.

For different working modes, the wiper cycle is 600ms for the BCM drive motor and 1400ms for the wiper return time. For the non-intermittent gear, the only difference is the interval time between two wiper actions.

For the coordinated work of the wiper and the front water spray, if the current water spray action is less than a certain time, such as 700ms, the wiper will not work. After the current water spray time is greater than 700ms, the wiper will start working and wipe three more times after the water spray stops.

3. Vehicle anti-theft alarm system

The vehicle body alarm module realizes the alarm function of the vehicle under various abnormal conditions. Once the alarm module is activated, it starts the sound and light alarm and remotely notifies the user's mobile phone.

Its specific functions are as follows:

1. When all three doors and the hood are closed, when the car is locked using the remote control or key, the left and right turn signals flash for 1 second, the horn sounds for 10ms, and the car enters the armed warning state.

2. In the armed state, if the three doors or the hood are opened, or the key insertion signal is detected, the vehicle will alarm and the start inhibition relay output will be enabled to inhibit starting. The start inhibition relay will remain valid after the alarm 3 cycles are completed.

3. Use the remote control or the driver's side key to unlock/lock the door to disarm the alarm state, the four door locks will open, and the left and right turn signals will flash.

4. When the vehicle is in an armed state, open the three doors or the hood and the siren will sound.

5. In the armed state, after the remote unlocking is implemented, no door or hood is opened or the key is inserted into the ignition lock within 30 seconds, which requires re-arming.

4 Car lock function

The door locks are controlled by the internal relay of the BCM. After receiving a valid unlocking signal, the BCM controls the door lock motors. The output time of the unlocking action of the three door lock motors is 250ms.

Remote control locking

In the disarmed state, after the BCM receives a valid RKE locking signal, if all three doors and the hood are closed, the three doors will be locked, the turn signals on both sides will flash once, the flashing cycle is 1 second, of which 0.5 seconds are on and 0.5 seconds are off, and the horn will beep for 10ms. If the BCM receives an RKE unlock command during the flashing period, the light flashing will enter the unlocking flashing process; if any other door is not closed after the driver's side door is closed, the lock motor will be activated and the turn signal will not flash. Wait until all doors are closed, and re-execute the confirmation action, that is, the turn signals on both sides will flash once, the flashing cycle is 1 second, of which 0.5 seconds are on and 0.5 seconds are off, and the horn will beep for 10ms.

In the armed state, after receiving a valid RKE locking signal, BCM still performs the locking action and the confirmation action at the same time, that is, the lock motor is activated, the turn signals on both sides flash once, the flashing cycle is 1 second, of which 0.5 seconds are on and 0.5 seconds are off, and the horn sounds for 10ms.