| 摘要 |
<p>A vehicle power steering system (5) derives a command speed signal from an input load signal, with the command speed signal being switched in a switching region of the input load signal between a low standby value and a high nominal value. The system is responsive to sensor apparatus (44) for providing a power steering load signal and filters (600) this power steering load signal to estimate the internal losses of the system. The filtered signal is used to compensate (610) the power steering load signal for these internal losses; and the compensated power steering load signal is provided as the input load signal from which the command speed signal is derived, with the derivation thus compensated and stabilized in the switching region. Preferably, the power steering load signal is a motor current signal from the motor (12) which drives the pump (14); and the filtering is performed by a low pass filter with a short finite time constant for decreasing input allowing tracking of the input to record its minimum value and a long finite time constant for increasing input to approximately hold the recorded minimum value as an estimate of internal system losses during an extended steering maneuver. The filter output may also be held constant when the power steering load signal exceeds a high reference value, varied inversely with the temperature of the power steering fluid, to maintain the loss estimate during a longer, extended period of high internal system losses, such as warm up in very cold weather. The power steering load signal may also be specifically compensated (132,134) in response to power steering fluid temperature and/or motor speed. <IMAGE></p> |
