Operating principle: cruise control

Cruise control function

Performance

Cruise control is a function that allows the user to regulate the speed of the vehicle.

Cruise control uses the speed setpoint programmed by the user and the vehicle speed to control the engine torque.

In regulation mode, the engine ECU continuously compares the programmed speed with the instantaneous vehicle speed.

Cruise control is active only if the vehicle speed is between 40 and 200 km/h.

Block diagram of the cruise control function

Block diagram of the cruise control function

Key:

• Single arrow = wired link
• Triple arrow = multiplexed link

LINKS
LINK NO.	SIGNAL	SIGNAL TYPE
1	Cruise control switch status	VAN CAR 1
2	Main brake switch status	ON / OFF
3	Cruise control switch status. Driver request to activate / deactivate cruise control. Main brake switch status. Main brake switch information fault	CAN
4	Vehicle speed information	CAN
5	Accelerator pedal position	ANALOGUE
6	Electronic throttle control	ANALOGUE
7	Electronic throttle position	ANALOGUE
8	Gearbox ratio information. Selector lever position information	CAN
9	Cruise control status information	CAN
10	Clutch switch status	ON / OFF
11	Secondary brake switch status	ON / OFF
12	Cruise control status information. Cruise control fault information	CAN

Functional description

In regulation mode, the engine ECU continuously compares the programmed speed with the instantaneous vehicle speed.

The instantaneous speed information is transmitted by the ABS ECU.

STEP	DETAILS
1	Reading of the cruise control command status by the steering column switch module
	Transmission of the cruise control command status to the BSI via the VAN CAR 1 network.
2	Reading of the main brake pedal contact by the BSI.

The BSI transmits the cruise control status, its controls and the brake switch information to the engine ECU via the CAN network 3 Reading of the secondary brake pedal contact by the engine ECU.

Consistency check with the main brake contact 3 information broadcast by the BSI via the CAN network.

The engine ECU receives the vehicle speed information from the ABS ECU via the CAN network 4 The engine ECU commands an increase or decrease in engine speed according to the desired speed and the actual speed. The engine ECU broadcasts the cruise control status information via the CAN network

Note: The driver can exceed the programmed speed by using the accelerator pedal. As soon as the driver releases the accelerator pedal, speed control at the programmed speed is active again.

IMPACT OF THE AUTOMATIC GEARBOX

The automatic gearbox ECU broadcasts the following information on the network:

• the engaged gear ratio,
• the selector lever position.

This information is used by the engine ECU to enable or disable cruise control.

The automatic gearbox ECU receives the cruise control status (active or disabled) in order to disable its driver intent self-detection strategies.

CRUISE CONTROL EXIT MODES

The cruise control function is faulty in the following cases:

• main brake contact information ¹ secondary brake contact information,
• brake contact failure,
• cruise control switch fault.

DEGRADED MODES

If one of the networks (CAN or VAN CAR 1) or the brake contact fails, cruise control is disabled.