Method and apparatus for determining the position of an armature of an electromagnetic actuator in response to the magnitude and time derivative of the actuator coil current

An apparatus for determining the position of an armature of an electromagnetic actuator having a coil, said armature being movable to and between first and second positions in response to a current flowing in the coil between first and second terminals, comprising:

• means for measuring the magnitude of current in the coil and producing a magnitude signal;
• means for measuring the rate of change of current in the coil and producing a rate of change signal;
• means for measuring the voltage between the first and second terminals;
• means for measuring a reactive component of the voltage between the first and second terminals;
• means for producing a flux linkage signal in response to the reactive component and said rate of change signal;
• and
• means for determining the position of the armature with respect to the coil in response to the magnitude and flux linkage signals.

A method for determining the position of an armature of an electromagnetic actuator having a coil having first and second terminals, the armature being movable to and between first and second positions in response to a current flowing in the coil, comprising the steps of:

• measuring the magnitude of current in the coil and producing a magnitude signal;
• measuring the rate of change of current in the coil and producing a rate of change signal;
• measuring the derivative of flux linkage versus current in the coil in response to said rate of change signal and producing a flux linkage signal;
• and
• determining the position of the armature with respect to the coil in response to said magnitude and flux linkage signals.