BMW 7 Series: System Functions

Fig. 82: Identifying Blind Spot Detection System Input/Output

BLIND SPOT DETECTION SYSTEM LEGENDS

1. Radar sensor (SWW2)
2. Radar sensor (master)
3. Not for US
4. Steering column switch cluster
5. Footwell module
6. Operating unit for driver assistance systems
7. Integrated Chassis Management
8. Steering wheel module and vibration actuator
9. Driver's door mirror
10. Front passenger door mirror
11. Instrument cluster
12. "Active Blind Spot Detection control unit function"
13. "Steering wheel vibration coordination" function

Detecting Road Users

Both (master and SWW2) radar sensors are used to detect road users. They operate independently of each other in their own respective areas of detection.

First, the position of the road users who have been detected is determined in a longitudinal and lateral direction.

Based on this, they are assigned a lane. In doing so a distinction is made between your own lane, the neighboring lanes on the right and left and other neighboring lanes that are further away.

If road users are in your "lane change zone", their approaching speeds to your own vehicle are recorded.

If, instead, a road user is in your blind spot, it is sufficient that you are aware of their presence. His exact position or speed in such cases is not critical for the warning to be issued.

Setting the Necessity for a Warning

The necessity for a warning is determined by the master radar sensor (SWW). To do this, it uses the data which it has collected about road users itself, as well as information from the SWW2 radar sensor.

For the blind spot detection system, only the road users on the immediately neighboring lanes on both sides are relevant. In contrast, road users in your own lane and on other more distant lanes do not pose a danger when you are making a lane change.

The distance and approaching speed of road users in your lane change zone, i.e. of vehicles immediately behind your own vehicle, is a decisive factor as to whether a warning is issued or not. The time remaining for cancelling a lane change maneuver is calculated using the distance (in a longitudinal direction) and their approaching speed. If this time drops below a threshold value for any one of the detected road users, the system decides that it is necessary to give a warning.

Road users in the blind spot lead to a minimal amount of time being calculated for cancelling a lane change.

This is why their exact position or speed relative to your own vehicle only has secondary importance. The mere presence of a road user in the blind spot therefore leads to the necessity for a warning.

The blind spot detection system must, of course, also be able to detect transitions from the lane change zone into the area of the blind spot and vice versa. A further challenge for the system is to determine the beginning and the end of the warning necessity when a vehicle in the neighboring lane is slowly overtaken by your own vehicle.

Vehicles that are overtaken very quickly cause the necessity for a warning to be suppressed or at least to end quickly.

In order to depict what the system is doing as reliably as possible to the driver, more than just the current measured values from the radar sensors are used, in particular in these special situations. In addition, the position and speed history of the other road users is taken into account. For example, based on a mathematical model, the system determines the point when an overtaking vehicle leaves the blind spot area and no longer poses a danger.

The master-radar sensor sends the result of the calculation as to whether the necessity for a warning is present or not, to the ICM control unit.

Switching the System On and Off

How the Active Blind Spot Detection system behaves with regard to the driver is ultimately controlled by the Integrated Chassis Management.

This includes:

• Switching it on and off
• Checking the operating conditions
• Checking for faults
• Distinguishing between information and a warning.

A button on the operating unit for the driver assistance systems is used to switch it on and off. The ICM control unit receives the signal by keystroke from the footwell module.

The ICM control unit permits it to be switched on only if no fault is present in the interconnected system and all operating conditions are satisfied.

If the ICM control unit carries out the driver's request to switch it on, the function illumination on the button is switched on as visual feedback. This is also controlled by the Integrated Chassis Management and is executed by the FRM.

If the request to switch it on cannot be carried out, the function illumination remains off. The status (switched on or off) remains key specific regardless of power cycles. If the Active Blind Spot Detection system is on in the current driving cycle, it will be on in the next driving cycle from the start.

If, after switching on the Active Blind Spot Detection, one of the operating conditions is infringed or a fault occurs, it is automatically deactivated. In such a case, the driver would not be able to tell if only the function illumination had switched off. Therefore, a Check Control message is issued (see the section entitled ).

Informing and Warning

The system can only generate information or a warning reliably, if the road speed is greater than 50 km/h (31 mph). The function will work at speeds under 50 km/h (31 mph), but not with the high quality and reliability required by BMW. In order not to compromise on the satisfaction of discerning BMW customers, no information or warnings are issued at speeds below 50 km/h (31 mph).

Information is the first stage of assistance that the driver receives from the Active Blind Spot Detection system.

The idea is to discreetly make the driver aware of a danger that could arise if he were to change lanes.

Information is produced by discreetly illuminating a yellow triangle-shaped warning light in the housing of the door mirror. The warning light is only activated on the side of the vehicle where the necessity for a warning has been detected by the master radar sensor.

Thanks to this concept, the system provides assistance to the driver as early as the preparation phase of a lane change maneuver. The driver can glance briefly in the direction of the door mirror at any to collect information from the Active Blind Spot Detection system as to whether or not a danger exists regarding a lane change.

The discreet manner of the information, on the other hand, does not cause annoyance if the driver wishes to continue to drive straight ahead without making a lane change.

The ICM control unit sends a bus signal that contains a warning request indicating in which door mirror the warning light should light up and with which intensity. In the process, the ICM control unit selects an intensity that is dependent on the surrounding brightness. To do this, it reads a bus signal from the rain/lights/solar/condensation sensor and evaluates it.

The warning request from the ICM control unit travels via the central gateway module to the footwell module, where the signal is routed to the door mirror(s) concerned.

The information is issued to the driver in all cases where all of the following conditions have been satisfied:

• The Active Blind Spot Detection system is switched on
• The road speed is above 50 km/h (31 mph)
• The master radar sensor has detected a necessity for a warning.

The second stage, the warning, should, in comparison, be significantly more prominent than the information. It should reach the driver quickly and directly, if he is still intending to make a lane change despite an impending dangerous situation.

The warning is issued, if the following conditions have been satisfied

• The conditions for information have been satisfied:
• The turn signal is switched on the side of the vehicle where the master radar sensor detected a necessity for a warning.

The steering column switch cluster issues the signal about the status of the turn signal via the FlexRay to the ICM control unit.

The only difference in the criteria for information and a warning is thus the status of the turn signal. The rear traffic situation or your own driving conditions do not influence it.

The visual aspect of the warning is generated by the respective warning light flashing with a high light intensity.

In addition, the steering wheel begins to vibrate.

NOTE: If the driver changes lanes without using the turn signal, he will only receive the information discreetly from the Active Blind Spot Detection system. The Active Blind Spot Detection system only sends out the more intensive warning, if the driver has switched on the turn signal when he intends to make a lane change.

Coordinating the Activation of the Vibration Actuator

Like the blind spot detection, the lane departure warning (KAFAS control unit) also uses the vibration actuator to produce a warning signal for the driver. For this, the systems use different amplitudes of vibration.

This is why these must be a coordinator function for controlling the vibration actuator. This is integrated into the ICM control unit.

Using the FlexRay bus system, the coordinated setpoint for the vibration is communicated to the steering column switch cluster and executed via the steering wheel module (LRE) and the vibration actuator in the steering wheel.

Blind Spot Detection from the Customer's Perspective

In this section, example situations are used to explain how the Active Blind Spot Detection system behaves in different traffic scenarios. The emphasis here is not on the technology, but rather on how the customer perceives the system. In all example situations it is assumed that the driver has switched on the Active Blind Spot Detection system and that the road speed of your own vehicle is above 50 km/h (31 mph).

Fig. 83: Traffic Scenario Without Need For Warning

BLIND SPOT DETECTION TRAFFIC SCENARIO WITHOUT WARNING REFERENCE CHART

1. Your own vehicle with blind spot detection
2. Faster vehicle in the left-side neighboring lane outside of the lane change zones

1. Lane change zone
2. Blind spot area

1. Turn signal OFF
2. Warning light in the driver's door mirror OFF
3. Warning light in the front passenger door mirror OFF
4. Steering wheel not vibrating

No Necessity for a Warning

Although another vehicle in the left-hand lane is approaching your own vehicle, neither information or a warning is generated. Even if the driver were to carry out a lane change with his own vehicle, this would not result in a dangerous situation. The time it would take for the other vehicle to reach your own vehicle is considerable.

A sufficient distance will be maintained by accelerating your own vehicle slightly or by a slight deceleration of the other vehicle. There is no necessity at all for the driver to be informed by the Active Blind Spot Detection system.

Information

Fig. 84: Traffic Scenario With Information From Blind Spot Detection System

BLIND SPOT DETECTION TRAFFIC SCENARIO REFERENCE CHART

1. Your own vehicle with blind spot detection
2. Faster vehicle in the left-side neighboring lane within the lane change zone
3. Equally fast vehicle as our own, in the right-side neighboring lane within the lane change zone

1. Lane change zone
2. Blind spot area

1. Turn signal OFF
2. Warning light in the driver's door mirror lights up with low intensity
3. Warning light in the front passenger door mirror OFF
4. Steering wheel not vibrating

The vehicle in the left-hand neighboring lane is already in the lane change zone. Because it is still approaching your own vehicle at a high speed, the time the driver would have to cancel a lane change maneuver is short. The blind spot detection system detects the necessity for a warning. Because the driver in his own vehicle does not show any specific intention of making a lane change, only the information and not the warning is issued.

The vehicle in the right-side neighboring lane is at a some what shorter distance from your own vehicle than the vehicle in the left side neighboring lane. It is travelling at the same speed as your own vehicle. The distance to your own vehicle is therefore not decreasing. Thus, there is no necessity for a warning on the right-hand side.

Only the warning light in the driver's door mirror lights up and it does this with low intensity.

Warning - Lane Change Zone

Fig. 85: Traffic Scenario With Warning From Blind Spot Detection System

BLIND SPOT DETECTION TRAFFIC SCENARIO WITH WARNING REFERENCE CHART

1. Your own vehicle with blind spot detection
2. Faster vehicle than our own, in the left-side neighboring lane within the lane change zone
3. Equally fast vehicle as vehicle B, in the right-side neighboring lane within the lane change zone

1. Lane change zone
2. Blind spot area

1. Left turn signal ON
2. Warning light in the driver's door mirror flashes with high intensity
3. Warning light in the front passenger door mirror lights up with low intensity
4. Steering wheel is vibrating

The vehicle in the left-hand neighboring lane is in the lane change zone and is approaching your own vehicle.

There is a necessity for a warning therefore on the left-hand side.

Because the driver intends to make a lane change to the left, he has switched on the left turn signal. A lane change maneuver is therefore imminent. In order to attract the attention of the driver quickly and directly, a leftside warning is produced. This means the warning light in the driver's door mirror flashes brightly and in addition the steering wheel vibrates.

The vehicle in the right-side neighboring lane is also approaching your own vehicle at this point. Therefore, the necessity for a warning also exists on the right-hand side. However, because the driver has not switched on the right turn signal, information is issued to this side, but no warning.

Warning - Blind Spot Area

Fig. 86: Traffic Scenario With Vehicles On Blind Spot Area

BLIND SPOT DETECTION TRAFFIC SCENARIO WITH VEHICLE REFERENCE CHART

1. Your own vehicle with blind spot detection
2. Vehicle in the left-side neighboring lane in the blind spot area
3. Vehicle in the right-side neighboring lane in the blind spot area

1. Lane change zone
2. Blind spot area

1. Right turn signal ON
2. Warning light in the driver's door mirror lights up with low intensity
3. Warning light in the front passenger door mirror flashes with high intensity
4. Steering wheel vibrates

Both the vehicle in the left-hand and the vehicle in the right-side neighboring lanes are in the blind spot area.

Therefore, the necessity for a warning exists on both sides, independently of how quickly they are travelling.

The driver intends to make a lane change to the right and therefore switches on the right turn signal. This causes the right-side warning to be produced. The warning light in the front passenger door mirror flashes brightly and the steering wheel vibrates.

Information is issued on the left-hand side, but no warning.

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