Servo mechanism with differential phase shift feedback

Claim 1

An apparatus for sensing the position of a movable object such as an actuator member in an industrial processing facility, comprising: a mechanical sensor element; an oscillator for generating an oscillating reference signal; first phase shifting means for shifting the phase of said reference signal in response to movement of said sensor element to create a first phase-shifted signal, said first phase shifting means being constructed so that the magnitude of phase shift between said reference signal and said first phase-shifted signal increases upon movement of said sensor element in a first direction; second phase shifting means for shifting the phase of said reference signal in response to movement of said sensor element to create a second phase-shifted signal, said second phase shifting means being constructed so that the magnitude of phase shift between said reference signal and said second phase-shifted signal increases upon movement of said sensor element in a second direction which is opposite to the first direction; and processing means for processing said first and second phase-shifted signals into first and second processed signals which, together, are representative of the position of said sensor element, said processing means being constructed and arranged so that said first processed signal is steady while said second processed signal pulses when said sensor element is to one side of a threshold position, and said first processed signal is pulsed while said second processed signal is steady when said sensor element is positioned to a second, opposite side of the threshold position, the use of said first and second phase-shifting means permitting position detection with minimal interference from component wear and the various environmental factors that tend to affect resistance-bases sensors.

Claim 2

An apparatus for sensing the position of a movable object such as an actuator member in an industrial processing facility, comprising: a mechanical sensor element; an oscillator for generating an oscillating reference signal; first phase shifting means for shifting the phase of said reference signal in response to movement of said sensor element to create a first phase-shifted signal, said first phase shifting means being constructed so that the magnitude of phase shift between said reference signal and said first phase-shifted signal increases upon movement of said sensor element in a first direction; second phase shifting means for shifting the phase of said reference signal in response to movement of said sensor element to create a second phase-shifted signal, said second phase shifting means being constructed so that the magnitude of phase shift between said reference signal and said second phase-shifted signal increases upon movement of said sensor element in a second direction which is opposite to the first direction; and processing means for processing said first and second phase-shifted signals into first and second processed signals which, together, are representative of the position of said sensor element, said processing means being constructed and arranged so that said first processed signal is steady while said second processed signal pulses when said sensor element is to one side of a threshold position, and said first processed signal is pulsed while said second processed signal is steady when said sensor element is positioned to a second, opposite side of the threshold position, the use of said first and second phase-shifting means permitting position detection with minimal interference from component wear and the various environmental factors that tend to affect resistance-bases sensors.

Claim 12

An apparatus for sensing the position of a movable object such as an actuator member in an industrial processing facility, comprising: a mechanical sensor element; an oscillator for generating an oscillating reference signal; a first phase shifter for shifting the phase of said reference signal in response to movement of said sensor element to create a first phase-shifted signal, said first phase shifter being constructed so that the magnitude of phase shift between said reference signal and said first phase-shifted signal increases upon movement of said sensor element in a first direction; a second phase shifter for shifting the phase of said reference signal in response to movement of said sensor element to create a second phase-shifted signal, said second phase shifting means being constructed so that the magnitude of phase shift between said reference signal and said second phase-shifted signal increases upon movement of said sensor element in a second direction which is opposite to the first direction; and a processor for processing said first and second phase-shifted signals into first and second processed signals which, together, are representative of the position of said sensor element, said processor being constructed and arranged so that said first processed signal is steady while said second processed signal pulses when said sensor element is to one side of a threshold position, and said first processed signal is pulsed while said second processed signal is steady when said sensor element is positioned to a second, opposite side of the threshold position, the use of said first and second phase-shifters permitting position detection with minimal interference from component wear and the various environmental factors that tend to affect resistance-based sensors.

Claim 13

An apparatus for sensing the position of a movable object such as an actuator member in an industrial processing facility, comprising: a mechanical sensor element; an oscillator for generating an oscillating reference signal; a first phase shifter for shifting the phase of said reference signal in response to movement of said sensor element to create a first phase-shifted signal, said first phase shifter being constructed so that the magnitude of phase shift between said reference signal and said first phase-shifted signal increases upon movement of said sensor element in a first direction; a second phase shifter for shifting the phase of said reference signal in response to movement of said sensor element to create a second phase-shifted signal, said second phase shifting means being constructed so that the magnitude of phase shift between said reference signal and said second phase-shifted signal increases upon movement of said sensor element in a second direction which is opposite to the first direction; and a processor for processing said first and second phase-shifted signals into first and second processed signals which, together, are representative of the position of said sensor element, said processor being constructed and arranged so that said first processed signal is steady while said second processed signal pulses when said sensor element is to one side of a threshold position, and said first processed signal is pulsed while said second processed signal is steady when said sensor element is positioned to a second, opposite side of the threshold position, the use of said first and second phase-shifters permitting position detection with minimal interference from component wear and the various environmental factors that tend to affect resistance-based sensors.