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Home >> Volvo >> 2008 >> S80 AWD L6-3.0L Turbo VIN 99 B6304T2 >> Repair and Diagnosis >> Accessories and Optional Equipment >> Collision Avoidance and Parking Assist Systems >> Description and Operation >> Forward Sensing Module (FSM) >> Function

Function






Function

Controlling the adaptive cruise control




The function adaptive cruise control is an extension of the existing cruise control. If there is no vehicle ahead, the speed will remain unchanged as for conventional cruise control. Speed is set by the driver in a similar way as for conventional cruise control.
If there is a vehicle ahead travelling at a lower speed than set speed, the speed will adjust itself automatically so that the set time gap to the vehicle ahead is attained. In this case, the adaptive cruise control in Forward Sensing Module (FSM) controls the Engine control module (ECM) and , if necessary, also Brake control module (BCM) to maintain the set time gap.
The time gap to the vehicle ahead is set by the driver in five steps, in the interval 1 to 3 seconds. If no earlier setting has been made, then step 3 of 5 will be used as basic value.
When the system is activated the last selected time interval is used. The value of the time interval is connected to the remote key. In this way every driver maintains their own setting. To change the time interval the driver presses one of the buttons on the Steering wheel switch left (SWSL) to increase or reduce the time interval. The Steering wheel switch left (SWSL) transmits information via LIN communication to the Central electronic module (CEM) (4/56), for the button that is activated. The Central electronic module (CEM) forwards this information to the Forward Sensing Module (FSM) (4/80) via the CAN network.
The function adaptive cruise control is limited to a speed that is higher than approx. 30 km/h.

Controlling the cruise control
See Design and Function, Engine control module (ECM).

Brake assistance in the event of a possible collision




In the event of a possible collision the brake assistance function is designed to aid the driver to quickly achieve the necessary braking effect that he/she requires from the vehicle in situations where there is a risk of a collision. Vehicles equipped with Forward Sensing Module (FSM) (4/80) have a forward facing radar installed in the front section (behind the grille). The forward facing radar (7/203) measures the distance to the approaching vehicle within its range. The Forward Sensing Module (FSM) uses information from the sensor (the radar) to determine the threat of a collision with the vehicle ahead that is moving in the same direction. The Forward Sensing Module (FSM) uses the determined threat of a collision, together with the actions of the driver, to warn the driver via one or several different types of warnings and by engaging increased brake control.
In the event of an imminent collision the Forward Sensing Module (FSM) can carry out the following:
1. An audible warning and/or a visual warning.
2. A low level of self-controlled braking force before the driver has depressed the brake pedal.
3. A reduction of the force that is required to achieve the full braking capacity of the vehicle.
The required effect of the function is to maximize the braking effect for the driving conditions where there is a risk of a collision with the approaching vehicle. The brake system achieves maximum efficiency through an increase of braking torque. This reduces the total braking distance without negatively affecting the driver, passengers or the behavior of the vehicle. In the event of a possible collision the brake assistance function triggers braking to minimize delays in the braking system and increases the driver's ability to brake.
To activate the brakes the Forward Sensing Module (FSM) communicates with the Brake control module (BCM) (4/16), which in turn activates the hydraulic modulator.
The main component in the function is the hydraulic modulator, which is integrated with the Brake control module (BCM). The primary function of the hydraulic modulator is to create the required brake pressure, which is based on a control signal. The hydraulic modulator is an electromechanical component that receives control signals from the Brake control module (BCM). The Brake control module (BCM) supplies the hydraulic modulator with sufficient control signals based on the driver's actions, the vehicle's speed and the information from the Forward Sensing Module (FSM). The hydraulic modulator achieves the desired brake pressure/brake torque for each wheel, based on the requested brake effect set using necessary information.
The Forward Sensing Module (FSM) requires, except to be able to control the hydraulic modulator, information from the Brake control module (BCM).
Information that the Forward Sensing Module (FSM) requires:
- stoplamp switch
- brake pedal position switch
- speed
- calculated braking force.
For more information about the Brake control module (BCM), see Design and Function, Brake control module (BCM).

Collision warning




The collision warning function is designed to warn in case of high likelihood of collision with a vehicle ahead, moving in the same direction and which suddenly brakes.
The collision warning system makes calculations when a warning is to be activated. The calculation is based on the speed of the approaching vehicle and of the vehicle itself. Normal reaction time, that approximately 85% of all drivers have, is compensated for in the calculation, the system's response time is also compensated for. If the warning distance is greater than the measured distance to the approaching vehicle and the driver has not taken any action, a warning will be activated. The warning consists of a combination of light and sound. The combination is set by the user/driver.
The visual warning is generated by means of the indicator, visual collision warning (27/2) and the audible warning is generated by means of the Driver information module (DIM) )5/1). The Forward Sensing Module (FSM) (4/80) transmits a request via CAN to the Driver information module (DIM), which generates the audible warning. The Forward Sensing Module (FSM) also transmits a request to the Infotainment control module (ICM) (3/281) to lower the sound (stereo) to the speakers during the period that the audible warning is generated by the Driver information module (DIM).
The collision warning function shall activate a warning so that approx. 85% of all drivers have a chance of stopping or reducing a collision with a vehicle ahead in a situation where a collision is imminent, on the condition that you maintain a time distance of more than 2 seconds to the vehicle ahead.

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