Sensing mechanical transitions from current of motor driving hydraulic pump or other mechanism
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United States of America Patent
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-
Nov 18, 2008
Grant Date -
Jul 6, 2006
app pub date -
Dec 28, 2005
filing date -
Dec 30, 2004
priority date (Note) -
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Abstract
A circuit and method for detecting an operating transition of a mechanical apparatus driven by a hydraulic prime mover comprising a hydraulic pump driven by an electric motor, the operating transition causing a change in the force applied by the mechanical apparatus on the prime mover. A motor current sensing circuit is connected in a motor power supply circuit to provide a motor current signal representing motor current. A bandpass filter receives the motor current signal and provides a filtered motor current signal consisting essentially of motor current signal components in the frequency range from a lower frequency boundary greater than zero Hz to an upper frequency boundary below substantially all the motor noise frequencies. A comparison circuit compares the filtered motor current signal to a first selected threshold level and outputs a signal representing the occurrence of the operating transition when the filtered motor current signal exceeds the selected threshold level. The circuit is preferably implemented with a digital controller programmed to perform these operations.
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