Antenna autotrack control system for precision spot beam pointing control
First Claim
1. A closed-loop system for improving spacecraft antenna pointing accuracy, comprising:
- an antenna pointing error detection module for detecting and measuring spacecraft antenna pointing error;
an adaptive feedforward estimator module for learning spacecraft antenna pointing error behavior from currently measured spacecraft antenna pointing error, and for concurrently generating predictive output of estimated future spacecraft antenna pointing error, the feedforward estimator module utilizing an autoregressive model given by φ
d[k]=a1φ
d[k−
1]+a2φ
d[k−
2]+ . . . +apφ
d[k−
p], where φ
d[k] is current distortion angle, and φ
d[k−
1], φ
d[k−
2], and φ
d[k−
p] are previously measured distortion angles, the autoregressive model being a discrete-time non-Fourier model; and
an antenna pointing error correction module for prospectively correcting spacecraft antenna pointing error based on the predictive output from the feedforward estimator module.
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Abstract
The present invention provides a system and a method for improving spacecraft antenna pointing accuracy utilizing feedforward estimation. The present invention takes advantage of the fact that spacecraft antenna pointing error has periodic behavior with a period of 24 hours. Thus, unlike the prior art feedback systems which blindly correct antenna pointing error continuously reacting only to presently sensed error, the present invention takes an intelligent approach and learns the periodic behavior of spacecraft antenna pointing error. Then, an estimate of antenna pointing error at a particular time going forward is predicted based on the learned model of the periodic behavior of the antenna pointing error. The predicted estimate is then used to correct or cancel out the antenna pointing error at a particular time in the future. The result is more accurate correction of spacecraft antenna pointing error by more than a factor of two.
40 Citations
12 Claims
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1. A closed-loop system for improving spacecraft antenna pointing accuracy, comprising:
-
an antenna pointing error detection module for detecting and measuring spacecraft antenna pointing error; an adaptive feedforward estimator module for learning spacecraft antenna pointing error behavior from currently measured spacecraft antenna pointing error, and for concurrently generating predictive output of estimated future spacecraft antenna pointing error, the feedforward estimator module utilizing an autoregressive model given by φ
d[k]=a1φ
d[k−
1]+a2φ
d[k−
2]+ . . . +apφ
d[k−
p], where φ
d[k] is current distortion angle, and φ
d[k−
1], φ
d[k−
2], and φ
d[k−
p] are previously measured distortion angles, the autoregressive model being a discrete-time non-Fourier model; andan antenna pointing error correction module for prospectively correcting spacecraft antenna pointing error based on the predictive output from the feedforward estimator module. - View Dependent Claims (2, 3, 4, 5)
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6. A method for improving spacecraft antenna pointing accuracy, comprising the steps of:
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detecting and measuring spacecraft antenna pointing error; providing the measured spacecraft antenna pointing error as input to an adaptive feedforward estimator module; the feedforward estimator module learning spacecraft antenna pointing error behavior from currently measured spacecraft antenna pointing error input, the feedforward estimator module utilizing an autoregressive model given by φ
d[k]=a1φ
d[k−
1]+a2φ
d[k−
2]+ . . . +apφ
d[k−
p], where φ
d[k] is current distortion angle, and φ
d[k−
1], φ
d[k−
2], and φ
d[k−
p] are previously measured distortion angles, the autoregressive model being a discrete-time non-Fourier model;the feedforward estimator module generating predictive output of estimated future spacecraft antenna pointing error based on the measured spacecraft antenna pointing error input and concurrently with the feedforward estimator module learning spacecraft antenna pointing error behavior; and prospectively correcting spacecraft antenna pointing error based on the predictive output from the feedforward estimator module. - View Dependent Claims (7, 8, 9, 10, 11)
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12. A closed-loop system for improving spacecraft antenna pointing accuracy, comprising:
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means for detecting and measuring spacecraft antenna pointing error; means for providing the measured spacecraft antenna pointing error as input to an adaptive feedforward estimator module; means for the feedforward estimator module learning spacecraft antenna pointing error behavior from currently measured spacecraft antenna pointing error input, the feedforward estimator module utilizing an autoregressive model given by φ
d[k]=a1φ
d[k−
1]+a2φ
d[k−
2]+ . . . +apφ
d[k−
p], where φ
d[k] is current distortion angle, and φ
d[k−
1], φ
d[k−
2], and φ
d[k−
p] are previously measured distortion angles, the autoregressive model being a discrete-time non-Fourier model;means for the feedforward estimator module generating predictive output of estimated future spacecraft antenna pointing error based on the measured spacecraft antenna pointing error input and concurrently with the feedforward estimator module learning spacecraft antenna pointing error behavior; and means for prospectively correcting spacecraft antenna pointing error based on the predictive output from the feedforward estimator module.
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Specification