Patent ID: 7377480

Claim:
A method by which a servomechanism operates an electrohydraulic valve, the method comprising: receiving a current setpoint which designates a desired level of electric current to be applied to a coil of the electrohydraulic valve; sensing an actual level of electric current flowing through the coil to produce a coil current value; producing a current error value based on the current setpoint and the coil current value; using the coil current value to produce an error value denoting a change in the resistance of the coil; deriving a coil resistance value by using the coil current value to produce a resistance error value denoting a change in the resistance of the coil, and using the resistance error value to produce the coil resistance value; deriving a desired voltage level for the coil in response to the coil resistance value and the current error value; and generating a PWM signal for driving the coil based on the desired voltage level.