Anomaly detection apparatus, method, and program

1. An anomaly detection apparatus comprising at least one processing circuit configured to:

calculate a reconstruction error of an input signal being a time-series signal,

calculate cycle information indicating cyclic property of the reconstruction error, and

determine presence/absence of an anomaly signal in the input signal on the basis of the cycle information or the cycle information and the reconstruction error.

2. The anomaly detection apparatus according to claim 1 , wherein the at least one processing circuit is configured to acquire a reference signal synchronized with a cycle of the input signal, and calculates similarity between the reconstruction error and the reference signal as the cycle information.

3. The anomaly detection apparatus according to claim 1 , wherein the cycle information is a feature quantity generated by executing Fourier transform for a vector generated by arranging values of the reconstruction error.

4. The anomaly detection apparatus according to claim 1 , wherein the cycle information is a degree of dispersion of two or more times selected on the basis of magnitude of values of the reconstruction error.

5. The anomaly detection apparatus according to claim 1 , wherein the at least one processing circuit is configured to;

divide the input signal into two or more short-time signals on the basis of reference information,

calculate the reconstruction error for each of the short-time signals, and

calculate, as the cycle information, a degree of dispersion of timings in the respective short-time signals for the reconstruction errors selected in the respective short-time signals.

6. The anomaly detection apparatus according to claim 5 , wherein

the input signal is a voltage value of AC voltage,

the reference information is a voltage value of the AC voltage or the number of phases of the AC voltage,

each of the short-time signals includes the input signal of a phase for one cycle of the AC voltage, and

each of the timings in the respective short-time signals indicates a phase of the AC current.

7. The anomaly detection apparatus according to claim 1 , wherein the at least one processing circuit is configured to calculate a smoothed signal on the basis of the reconstruction error, and corrects the reconstruction error by subtracting the smoothed signal from the reconstruction error.

8. The anomaly detection apparatus according to claim 1 , wherein the at least one processing circuit is configured to execute weighting for the reconstruction error on the basis of the cycle information, and determine presence/absence of the anomaly signal on the basis of the cycle information and the weighted reconstruction error.

9. A method, implemented by at least one processing circuit of an anomaly detection apparatus, comprising:

calculating a reconstruction error of an input signal being a time-series signal;

calculating cycle information indicating cyclic property of the reconstruction error; and

determining presence/absence of an anomaly signal in the input signal on the basis of the cycle information or the cycle information and the reconstruction error.

10. A non-transitory computer-readable storage medium storing a program for causing a computer to execute:

a function of calculating cycle information indicating cyclic property of the reconstruction error; and

a function of determining presence/absence of an anomaly signal in the input signal on the basis of the cycle information or the cycle information and the reconstruction error.