BMW 7 Series: Functions

Technical Networking Overview

Fig. 141: ACC Stop&Go Input/Output Diagram

INDEX REFERENCE CHART

Cruise Control with Braking Function

Fig. 142: Overview Of Cruise Control

The cruise control with braking function has already featured in the BMW 3 Series (E9x). It is also referred to as "Dynamic Cruise Control" (DCC).

It relieves the burden on the driver on quiet roads by maintaining a constant speed regardless of the resistance to vehicle motion (gradient, payload).

It also offers the driver the opportunity to adjust the set speed in small or large increments, which is then set and maintained by the system by controlling power output and braking. The brakes are also controlled during steep downhill driving if sufficient deceleration is not achieved by engine drag-torque alone.

Dynamic Cruise Control in the F01/F02 is not computed in the DSC control unit as it is in other vehicles.

Instead, it has been integrated into the ICM control unit.

The function has, of course, been newly configured for optimum compatibility with the F01/F02. Due to the new vehicle interior, there are differences in how the function is operated and how information is displayed by comparison with the function implemented in other vehicles. These are described here.

Operation and display

In the F01/F02, Dynamic Cruise Control is no longer operated by means of an operating lever. Instead, the driver can operate the function conveniently using a button pad on the multifunction steering wheel.

Fig. 143: Identifying Set, I/O And RSE Buttons With Rocker Switch

INDEX REFERENCE CHART

1. SET button to activate
2. Rocker switch to change the set speed
3. I/0 button to switch on and off
4. RES button to resume a stored set speed

To prevent accidental activation, the function remains inoperable until the I/0 button has been pressed after the vehicle has started. This switches the function to standby. This state is acknowledged in the instrument cluster by a green indicator light lighting up.

With the function in standby, the driver is now able to activate cruise control. To do this, the driver can press the SET button used to store the vehicle's current road speed as the set speed. An active state is indicated by a green indicator light in the circumference of the speedometer dial lighting up.

There is an alternative way to activate the function if a set speed has already been stored. This is indicated by an orange indicator light in the circumference of the speedometer dial. If the driver wants to use this speed value as the set speed, he simply has to press the RES button. Dynamic Cruise Control then accelerates or decelerates the vehicle to this speed value automatically.

While the function is active, the driver is able to increase or decrease the set speed at any time. There are two adjustment increments available. The rocker switch offers two different increments in either direction. First, the set speed is altered in increments of 1 km/h each time the rocker switch is pressed; second, it is altered in increments of 10 km/h.

NOTE: In the F01/F02, the adjustment range for the set speed is 30 km/h (18 mph) to 230 km/h (142mph).

If the rocker switch is pressed and held, the system will accelerate/decelerate the vehicle until the rocker switch is released. This is known as a "comfort dynamics" function as featured in the E9x and E6x LCI.

To deactivate the system, the driver can simply operate the brake pedal like before. Or, the driver can deactivate the system by pressing the I/0 button. The system is then returned to standby and keeps the set speed last used stored in its memory.

If the driver then presses the I/0 button once more, the system is completely switched off and the green indicator light in the instrument cluster goes out.

There follows a summary of the most important displays for Dynamic Cruise Control.

Fig. 144: Display Indicator For Dynamic Cruise Control

INDEX REFERENCE CHART

1. "Standby" state
2. "Active" state

1. Orange LED: set speed of 130 km/h (81 mph) stored
2. Indicator light for Dynamic Cruise Control
3. Green LED: actively maintaining a set speed of 130 km/h (81 mph)
4. Set speed displayed numerically: briefly displayed at the time of function activation or whenever the set speed is changed

In the event of particular operating states, the displays shown here are supplemented by information messages displayed below the speedometer. This is the case, for instance, if the driver attempts to activate the system even though not all the activation criteria have been fulfilled (e. g. speed less than 18 mph).

In the F01/F02, a difference in the way Dynamic Stability Control interacts with Dynamic Cruise Control has been introduced. This is explained by the following example: Using the "Dynamic Performance Control", the driver has selected a mode in which DSC is inactive (e. g. "Sport+" mode). If the driver now activates cruise control, DSC will be activated automatically. This is accompanied by an automatic changeover from "Dynamic Performance Control" to "Normal" mode. In previous vehicles, the driver was unable to activate cruise control without activating DSC manually first.

Active Cruise Control with Stop&Go Function

Fig. 145: Traffic Jam Situation

The ACC Stop&Go function in the F01/F02 is largely identical to that in the E6x LCI.

ACC Stop&Go extends the operating range of the former ACC system to include low speeds down to a standstill. In other words, speed and distance from the vehicle in front are automatically controlled at those speeds as well.

ACC Stop&Go will automatically stop the car if necessary and then indicate to the driver as soon as it detects that it is possible to start moving again. To pull away again, the driver has to acknowledge this message. The pulling-away process is controlled fully automatically by ACC Stop&Go only if the duration of the standstill is very short.

Thus, ACC Stop&Go provides optimum assistance for the driver not only in moving traffic but also in traffic jams such as are more and more frequently encountered on highways. However, this system (in common with ACC) is not intended for use in urban areas for negotiating junctions or traffic lights.

The functions of ACC Stop&Go in the F01/F02 differ from those in the E6x LCI in the following areas:

• Operation and display
• Behavior in response to driver's intention to get out.

Operation and display

ACC Stop&Go and DCC are activated/deactivated in a very similar way. The driver is able to activate ACC Stop&Go not only while the vehicle is in motion, but also when the vehicle is stationary, provided the system has detected another vehicle in front. To activate ACC Stop&Go at a standstill, the driver has to depress the brake pedal and press the SET or RES button at the same time. The activation conditions that applied to the E6x LCI similarly apply here:

• Brake pedal must not be depressed
• Automatic transmission must be in Drive
• Parking brake must not be activated
• Radar sensors must be operational and not dirty
• There must be no system fault present.

Fig. 146: Identifying Buttons And Switches Of Active Cruise Control System

INDEX REFERENCE CHART

1. SET button to activate
2. Button for reducing the distance
3. Rocker switch to change the set speed
4. Button for increasing the distance
5. I/0 button to switch on and off
6. RES button to resume a stored set speed

If Dynamic Stability Control was inactive before, in the F01/F02 it is activated as soon as ACC Stop&Go is activated. At the same time, the "Dynamic Performance Control" automatically changes to "Normal" mode (same behavior as for DCC).

Similarly, ACC Stop&Go cannot be deactivated by means of the I/0 button while the vehicle is stationary unless the brake pedal is depressed at the same time.

NOTE: In the F01/F02, the adjustment range for the set speed is 30 km/h (18 mph) to 230 km/h (142mph).

By comparison with DCC, a vehicle with ACC Stop&Go has an MFL button pad that additionally features two buttons for making distance adjustments.

Each (short) button stroke to change the distance increases the desired distance used by ACC Stop&Go for its control process by one increment at a time. A total of four increments are available to the driver.

The most important display functions of ACC Stop&Go in the F01/F02 are illustrated below.

As with DCC, the display symbols for ACC Stop&Go are supplemented by messages displayed below the speedometer as and when necessary.

If the vehicle is equipped with the head-up display option, the ACC displays also appear there, provided the driver has configured them to do so.

Fig. 147: Display Indicator For ACC Stop & Go

INDEX REFERENCE CHART

1. "Standby" state
2. "Active" state

1. Orange LED: set speed of 130 km/h (81 mph) stored
2. Lines that indicate "standby" mode
3. Green LED: set speed of 130 km/h (81 mph) selected by the driver (the speedometer needle is not pointing at the LED here because the vehicle in front is travelling slower than the set speed)
4. Car symbol: vehicle ahead detected by ACC Stop&Go
5. Bars: represent the distance increment selected by the driver
6. Set speed displayed numerically: briefly displayed at the time of function activation or whenever the set speed is changed

Behavior in response to the driver's intention to get out

ACC Stop&Go uses the DSC hydraulics to reliably slow the vehicle to a halt and keep it stationary.

Without a supply of electricity, the DSC hydraulics are, however, unable to indefinitely maintain the braking force necessary to keep the vehicle stationary.

Fig. 148: Driver's Intention

INDEX REFERENCE CHART

1. State of driver's seat belt and driver's door
2. Displays of ACC Stop&Go and parking brake in the instrument cluster
3. Road traffic situation or perceptible response of vehicle with ACC Stop&Go

1. ACC Stop&Go is active and has automatically braked the vehicle to a halt behind a vehicle in front.

   The DSC hydraulics hold the vehicle stationary (and are monitored by the DSC control unit).

2. The driver has undone the seatbelt and opened the driver's door. This is evaluated as an unequivocal signal for the driver's intention to get out. DSC detects this state and activates the parking brake function. As a result, the vehicle can be held stationary for any length of time, even if the driver gets out. The parking brake indicator light indicates that the parking brake has been applied. ACC Stop&Go detects that the parking brake has been applied and switches off automatically.

By contrast with the E6x LCI, the F01/F02 is equipped with an electromechanical parking brake (EMF). This is able to assume the function of holding the vehicle stationary if

• DSC is no longer able to maintain the hold function due to a fault or overload,
• the driver gets out or
• the engine is switched off.

Thanks to the EMF, therefore, ACC Stop&Go also benefits from improvements designed to enhance comfort while the vehicle is stationary. Drivers of an E6x LCI had to be issued with a warning if they were about to get out with ACC Stop&Go still active. They were reminded to secure the vehicle against rolling away. They had to apply the parking brake manually.

In the F01/F02, however, the parking brake function of the EMF is activated automatically whenever the driver is about to get out of the vehicle with ACC Stop&Go still active.

The driver's intention to get out of the F01/F02 is detected by the signals of the seat belt buckle contact (driver's) and door contact (driver's door). A signal from the seat occupancy detection (driver's seat) is not used in the F01/F02.

While the vehicle is being held stationary by ACC Stop&Go, the DSC unit takes over all monitoring and control processes. The DSC also controls the system's behavior in response to the driver's intention to get out of the vehicle. For ACC Stop&Go, this is absolutely identical to that implemented for the DSC-internal Automatic Hold function (the "see F01/F02 LONGITUDINAL DYNAMICS SYSTEMS" Product Information).

ACC Stop&Go is deactivated automatically if, from the bus signals it receives, it detects that the parking brake function has been activated. Now the vehicle is still held stationary but by the parking brake function instead.

Adaptive Brake Assistant with Warning Function

Fig. 149: Operating Range Of Adaptive Braking Assistant (Panic Braking Situation)

As Featured in the E6x LCI

The Adaptive Brake Assistant has been carried over from the E6x LCI. This function is included automatically if the customer orders the ACC Stop&Go option, or in some countries, the ACC option.

Adaptive Braking Assistance offers the greatest benefit in situations where the vehicle is following another vehicle. If the vehicle in front brakes hard, it is detected by the long-range radar sensor. The two subfunctions of

• precharging the brake system (also known as the "brake readiness" function) and
• lowering the threshold for the hydraulic Brake Assistant

assist the driver to perform the braking operation to best effect and thus in the best case to avoid a rear-end collision with the vehicle in front.

In the F01/F02, this function is no different from the function implemented in the E6x LCI. The long-range radar sensor gathers data on the road users ahead of the vehicle. The data are supplemented by data relating to the driving status of the customer's vehicle, and both types of data are used as a basis for calculating a collision avoidance rate of deceleration. This is the rate of deceleration at which the driver would have to brake in order to avoid a collision with the vehicle in front. If the calculated collision avoidance deceleration is above a stored threshold value, the brake system begins to precharge and the activation threshold for the hydraulic Brake Assistant is reduced.

All sensor-related and processing functions of Adaptive Braking Assistance are computed in the long-range radar sensor. However, the computed output variables have to be transmitted to the DSC control unit because that is where they are put into action. To make this possible, the ICM control unit acts as a gateway between the local CAN and the FlexRay.

In the DSC control unit, there are still more conditions that need to be fulfilled before these two subfunctions can be carried out. (Example: road speed must be higher than a defined minimum speed.) However, the Adaptive Braking Assistance technology also has limits and cannot react fast enough in situations such as other road users cutting in right in front of the vehicle. Driving with care and anticipation remains the fundamental imperative even with Adaptive Braking Assistance!

NOTE: The Adaptive Brake Assistant and its subfunctions, precharging the brake system and lowering the threshold for the hydraulic Brake Assistant are always active and does not have to be switched on separately by the driver.

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