| 摘要 |
Wheel brake pressures are controlled electrically in dependence upon at least driver actuation of the pedal 12 and the pressure of a high-pressure accumulator 44. In the event that the accumulator pressure sensor 46 is defective, the accumulator pressure is estimated according to a model and the estimated pressure is taken into account during operation of the brake system. For estimating the pressure, when there is no braking demand on the system, initially the pump 42 is energised, an inlet valve for one wheel is energised with 90% of its opening current, and isolating, relief, and balance valves (eg.MV_TVR, MV_EVA, MV_BVA) are closed so that pump pressure causes the inlet valve to slowly open. When the wheel pressure increases, that pressure is saved as the accumulator pressure reference value, and the estimated accumulator pressure is derived from that reference value and the accumulator input and output volumes.
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