ABS Control
When the wheel speed is significantly reduced from the estimated vehicle speed, the VSA modulator-control unit closes the inlet valve and opens the outlet valve momentarily to reduce brake fluid pressure and the pump motor starts to run. As wheel speed increases, the VSA modulator-control unit maintains brake fluid pressure by keeping the inlet valve closed. Brake fluid pressure is increased when wheel speed matches the estimated speed of the vehicle. The VSA modulator-control unit repeats this valve control operation to control the ABS function.
Split Control
When one drive tire is on a low traction surface like a gravel shoulder, while the other drive tire is on a high traction surface like a paved highway, applying the brakes causes increased driving force on the high traction surface. This increased driving force on the high traction surface results in vehicle instability. To maintain vehicle stability during this scenario, the VSA modulator unit actively controls the driving force by adjusting the hydraulic fluid pressure, as needed, for each wheel.