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5) Hydraulic Circuit of HBA
The above figure shows one front and one rear wheel and the same hydraulic circuit forms as in the
ESP operation. When HECU recognizes that it is an emergency and it is required for hard braking,
depending on the pressure value of the brake pressure sensor and pressure changes caused by the
pressure sensor timing, it operates the pump immediately to apply the brake pressure at the wheels.
Then, the pressure in the pump increases until just before the corresponding wheel gets locked. The
motor still keeps rotating and the outlet valve and the separation valve will stay closed. When the wheel
starts to lock, the HBA function cancels and switches to ABS operation.
