Abnormality determination method, abnormality determination device, and abnormality determination system

An abnormality determination method for causing a processor to execute a process, the abnormality determination method comprising executing on the processor the steps of:

• creating a first unit space corresponding to a normal mode of an object while the object is in a normal state, the object being either a bridge, a building, or a mechanical device;
• creating an (i+1)-th unit space corresponding to an i-th abnormal mode of the object while the object is in an abnormal state for each integer i greater than or equal to 1 and less than or equal to N, N being an integer greater than or equal to 2;
• measuring a physical quantity of the object by a measuring instrument attached to the object, the physical quantity being either acceleration, angular velocity, velocity, displacement, pressure, current, or voltage so as to provide measurement data;
• calculating a first Mahalanobis distance in the first unit space based on the measurement data;
• calculating an (i+1)-th Mahalanobis distance in the (i+1)-th unit space for each integer i based on the measurement data;
• determining whether the object is in the normal mode based on the calculated first Mahalanobis distance wherein the processor determines that the object is in the normal state when the calculated first Mahalanobis distance is within a first threshold range;
• and
• determining whether the object is in which one of the first to N-th abnormal modes based on the calculated (i+1)-th Mahalanobis distances when the processor determines that the calculated first Mahalanobis distance is outside of the first threshold range,
• wherein the processor is configured to select a minimum Mahalanobis distance within the calculated (i+1)-th Mahalanobis distances as the one of the first to N-th abnormal modes for the object.