Sensor system

A sensor system comprising:

• a plurality of sensors positioned along a line and measuring data indicating a passing state of a workpiece being conveyed upon the line, wherein the passing state indicates whether a workpiece is within a detection range of the sensor;
• a plurality of slave units respectively connected to the plurality of sensors and acquiring the data measured by the plurality of sensors;
• and
• a master unit connected to the plurality of slave units, wherein the master unit has:
• a storage part for storing the data in association with information which relates to the timing at which the data was measured, and
• a determination part for comparing the data transmitted from two or more of the plurality of slave units using the information which relates to the timing, and determining a change in state of the workpiece,
• wherein the data is time series data including rising waveforms or falling waveforms in accordance with the passing states of the workpiece being conveyed upon the line, and
• wherein the master unit further includes a mapping part for mapping the rising waveforms or the falling waveforms acquired by two or more of the plurality of slave units regarding the same workpiece on the basis of intervals of the rising waveforms or intervals of the falling waveforms included in the time series data acquired by the two or more slave units,
• wherein the mapping part calculates differences between the intervals of the rising waveforms or the intervals of the falling waveforms acquired by the first slave unit and the intervals of the rising waveforms or the intervals of the falling waveforms acquired by the second slave unit, calculates an average value of the differences in each of a plurality of combinations of the differences, searches for the combination of the differences having the average value as the smallest, and performs mapping of rising waveforms or falling waveforms acquired by a first slave unit of the plurality of slave units and rising waveforms or falling waveforms acquired by a second slave unit of the plurality of slave units in accordance with the differences in the searched combination,
• wherein the determination part calculates timings at which the workpiece has to pass through detection ranges of the plurality of sensors on the basis of a conveyance speed of the line and positions of the plurality of sensors;
• compares the data measured by a sensor, of the plurality of sensors, positioned upstream in the line and the data measured at the timing at which the workpiece has to pass by with a sensor, of the plurality of sensors, positioned downstream in the line;
• and determines a positional deviation of the workpiece, and
• wherein the determination part determines a change in the conveyance speed of the workpiece on the basis of a difference between a time period during which the workpiece is detected by the sensor positioned upstream in the line and a time period during which the workpiece is detected by the sensor positioned downstream in the line.