Servo loop control for a coriolis rate sensor dither drive
First Claim
1. A dither drive controller for a Coriolis rate sensor, comprising:
- (a) position sensing means for sensing a dither position of the Coriolis rate sensor as it is driven to vibrate by the dither drive, and for producing a signal indicative of the dither position;
(b) means for determining a dither velocity of the Coriolis rate sensor from the signal produced by the position sensing means and for producing a signal indicative of said dither velocity;
(c) means for providing a dither drive signal at a predetermined frequency;
(d) means for producing dither velocity aiding and acceleration aiding signals;
(e) control means, connected to receive and add the dither position and velocity signals, the dither drive signal, and the dither velocity aiding and acceleration aiding signals, for producing an output signal for energizing the dither drive to vibrate the Coriolis rate sensor at said predetermined frequency, and at a constant, stable amplitude, as a function of the sum of all these signals.
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Accused Products
Abstract
A servo loop control for the dither drive of a Coriolis rate sensor is provided. The dither drive includes a pair of electromagnetic coils (70), which are alternately energized to dither a parallelogram frame (50), on which first and second accelerometers (20 and 22) are mounted with their sensitive axes antiparallel to each other. An LVDT position sensor (106) provides a feedback signal indicating the relative position of the two accelerometers or displacement of the parallelogram frame as it is dithered back and forth. The position signal is summed with a driving signal, amplified and summed with a velocity aiding signal and a velocity signal derived by differentiating the position signal. The resulting sum is amplified and again summed with an acceleration aiding input that includes compensation for a phase shift in the motion of the parallelogram frame relative to the driving force applied by the electromagnet coils, and for (I2 and 1/D2) nonlinearities where I is the current and D is the pole gap dimension (114). The sum of these signals is used to energize the electromagnetic coils, driving the parallelogram frame with a signal that causes it to dither in a pure sinusoidal fashion. Each of the critical frequencies used in the servo loop is phase locked to a common stable crystal reference frequency, and all components of the servo loop are powered by a common power supply. The servo loop provides improved frequency and phase stability and insensitivity to voltage fluctuations.
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Citations
27 Claims
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1. A dither drive controller for a Coriolis rate sensor, comprising:
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(a) position sensing means for sensing a dither position of the Coriolis rate sensor as it is driven to vibrate by the dither drive, and for producing a signal indicative of the dither position; (b) means for determining a dither velocity of the Coriolis rate sensor from the signal produced by the position sensing means and for producing a signal indicative of said dither velocity; (c) means for providing a dither drive signal at a predetermined frequency; (d) means for producing dither velocity aiding and acceleration aiding signals; (e) control means, connected to receive and add the dither position and velocity signals, the dither drive signal, and the dither velocity aiding and acceleration aiding signals, for producing an output signal for energizing the dither drive to vibrate the Coriolis rate sensor at said predetermined frequency, and at a constant, stable amplitude, as a function of the sum of all these signals. - View Dependent Claims (2, 3, 4, 5)
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6. A servo loop for use in controlling a Coriolis rate sensor dither drive, comprising:
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(a) feedback means for producing a signal indicative of a displacement of the coriolis rate due to the dither drive; (b) differentiating means, connected to receive the signal from the feedback means, for differentiating said signal and providing a velocity signal indicative of the velocity of said coriolis rate sensor due to the dither drive; (c) driver means for producing (i) a dither drive signal at a predetermined frequency; (ii) a rate aiding signal; (iii) an acceleration aiding signal; and (d) summing means for summing the signals produced by the feedback means, the differentiating means, and the driver means, and for producing an output signal that energizes the dither drive at a stable, fixed amplitude as a function as said signals. - View Dependent Claims (7, 8, 9, 10)
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11. A dither drive controller for an attractor motor used to provide a force to dither a Coriolis rate sensor, causing the Coriolis rate sensor to move in a dither motion, comprising:
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(a) means for providing a sinusoidally varying dither drive signal at a predetermined frequency; (b) means for producing an acceleration aiding signal corresponding to a second order derivative of the dither drive signal; (c) means for modifying the acceleration aiding signal to compensate for a nonlinearity in the attractor motor driving force; and (d) means for summing the modified acceleration aiding signal and the dither drive signal to produce an output signal for energizing the attractor motor. - View Dependent Claims (12, 13, 14, 15, 16, 17)
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18. A method of controlling a dither drive for a Coriolis rate sensor, comprising the steps of:
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(a) sensing a dither position of the Coriolis rate sensor; (b) producing a signal indicative of the dither position; (c) determining a dither velocity of the Coriolis rate sensor; (d) producing a signal indicative of the dither velocity; (e) providing a dither drive signal at a predetermined frequency; (f) producing dither velocity aiding and acceleration aiding signals; (g) summing the dither position, velocity, velocity aiding, and acceleration aiding signals; and (h) controlling the Coriolis rate sensor so that it vibrates at a constant, stable amplitude, as a function of the sum of the dither position and velocity signals, the dither drive signal, and the dither velocity aiding and acceleration aiding signals. - View Dependent Claims (19, 20, 21)
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22. A method for controlling a dither drive that includes an attractor motor used to provide a dither driving force to a Coriolis rate sensor, comprising the steps of:
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(a) generating a sinusoidally varying dither drive signal at a predetermined frequency; (b) generating a sinusoidally varying acceleration aiding signal; (c) modifying the acceleration aiding signal to compensate for a nonlinearity of the dither driving force; (d) summing the modified acceleration aiding signal and the dither drive signal to produce a drive current for the attractor motor; and (e) energizing the attractor motor with the drive current. - View Dependent Claims (23, 24, 25, 26, 27)
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Specification