A rotary encoder (12, fig.1) comprises an annular track with an alternating pattern of at least two different encoding regions. A first detector 16 produces a first alternating output signal as the track of encoding regions rotates about its axis past the detector. The state of the output signal depends on which encoding region is facing the first detector. A second detector 17, offset from the first detector, produces a second alternating output signal as the track rotates about its axis past the detector. The state of the output signal depends on which encoding region is facing the second detector. The combined values of the output signals assume a plurality of unique states, changing as the encoder rotates. Post-processing apparatus comprises a memory which stores first and second sets of compensation values, each associated with a possible state change. Each compensation value is indicative of an average error in the position at which the corresponding change of state occurs. A processing means is configured to generate a position signal that is updated when there is a change in the combined states of the output signals, the position signal being corrected based on a compensation value of one of the first set of compensation values associated with the latest change in state. The processing means compares the first set of compensation values with the second set of compensation values to determine a change in the sensor. The first and second set of compensation values is generated during and after an initial calibration respectively.
Improvements relating to rotary encoders
2023-05-03
Patent
Electronic Resource
English
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