Active Yaw Control

S60 (11-)/V60 

Courtesy of VOLVO CARS CORPORATION

Other 

Courtesy of VOLVO CARS CORPORATION

The brake control module (BCM) with DSTC/ESC system continually uses information from various system sensors to calculate the position of the steering wheel and the vehicle. The Brake Control Module (BCM) calculates the driving style of the driver by measuring:

• steering angle
• steering angle speed
• engine torque
• the vehicle speed
• brake pressure.

The brake control module (BCM) also calculates vehicle behavior by monitoring the vehicle's:

• yaw angle speed
• lateral acceleration
• forward acceleration.

The brake control module (BCM) receives information on current steering angle from the steering wheel angle sensor module (SAS).

When the differences between the driver's intended direction of travel and the vehicle's behavior exceed a threshold, active yaw control (AYC) regulates engine torque (stability function) in order to maintain the vehicle's lateral stability during most driving conditions. The AYC function also activates the individual brake control to regulate the SV and ESV valves of the hydraulic unit as well as the intake and outlet valves. These correct the vehicle in the event of a skid.

For information on steering angle and steering angle speed, see Design and Function, Steering Wheel Angle Sensor Module (SAS).

Courtesy of VOLVO CARS CORPORATION

1	SV valve (separation valve), normally open	5	Intake valve, normally open
2	ESV valve (electronic shuttle valve), normally closed	6	Pressure equalizer
3	Hydraulic pump	7	By-pass valve
4	Outlet valve, normally closed	8	Non-return valve

During AYC, in other words when the vehicle is skidding, the hydraulic pump starts to build up brake pressure regardless of whether the driver is activating the brake pedal. The brake control module (BCM) then activates the valves in the hydraulic unit and checks individual wheel brake force. This is done by increasing, maintaining or lowering brake pressure individually to stabilize the vehicle. If the driver depresses the brake pedal during stability control, the control module will use the brake pressure sensor integrated in the hydraulic unit to incorporate the driver's brake actuation into stability control.

If the driver depresses the brake pedal during stability control, the brake control module (BCM) will use the brake pressure sensor integrated in the hydraulic unit to incorporate the driver's brake actuation into stability control.

The calculations performed by the control module include the driver's desired brake pressure and functions for:

• Active yaw control (AYC)
• ABS
• EBD
• Stability control