Method and apparatus for evaluating quadrature encoders

A method for evaluating the performance of a quadrature encoder which generates two electrical wave train signals indicative of the movement of a mechanical component, each wave train signal varying between first and second states and the two wave train signals normally being out of phase one with the other, the method comprising the steps of:

• receiving the two wave train signals at a processor,
• distinguishing, from the succession of changes of the signals between respective first and second states, sets of four types of change of phase relation between the two signals,
• timing and recording a time interval required for each type of phase change in each set,
• accumulating a plurality of sets of records of timed intervals for phase changes,
• computing from the accumulated plurality of sets of records the mean time interval for a phase change,
• comparing the computed mean time interval with the accumulated sets of records of timed intervals and determining the type of phase change for which the difference from the mean time interval is the greatest,
• deriving from the record of timed intervals which has the greatest difference from the mean time interval and the computed mean time interval an encoder quality signal representative of the performance of the quadrature encoder generating the wave train signals, and
• displaying the encoder quality signal.

A method for evaluating the performance of a quadrature encoder which generates two electrical wave train signals indicative of the rotation of a shaft, each wave train signal varying between first and second states and the two wave train signals normally being out of phase one with the other, the method comprising the steps of:

• distinguishing, from a succession of changes of the two wave train signals between respective first and second states, four types of change of phase relation between the two wave train signals;
• timing and recording a time interval required for each type of phase change;
• accumulating a predetermined plurality of sets of records of timed intervals for each of the four types of change of phase relation between the two wave train signals;
• sensing the presence of each of the two wave train signals;
• responding to the absence of the sensed presence of one wave train signal by interrupting the accumulation of sets of records and generating and displaying an error signal;
• sensing the occurrence of simultaneous changes in state in the two wave train signals;
• responding to a sensed occurrence of such changes by interrupting the accumulation of sets of records and generating and displaying an error signal;
• sensing the sequence of changes in state in the two wave train signals;
• responding to a sensed occurrence of a reversal in such sequence by interrupting the accumulation of sets of records;
• sensing the accumulation of the predetermined plurality of sets of records;
• computing from the accumulated plurality of sets of records the mean time interval for a change of phase relation between the two wave train signals;
• comparing the computed mean time interval with the accumulated sets of records of timed intervals and determining the one type of phase change for which the difference from the mean time interval is the greatest;
• computing a number indicative of the phase duration of that type of change of phase which has the greatest difference from the mean time interval and deriving, from the record of timed intervals which has the greatest difference from the mean time interval and the computed mean time interval, an encoder quality signal representative of the performance of the quadrature encoder generating the wave train signals;
• and displaying the encoder quality signal.

An apparatus for evaluating the performance of a device which generates two electrical wave train signals, each wave train signal varying between first and second states and the two wave train signals normally being out of phase one with the other, the apparatus comprising:

• processor means for receiving the wave train signals generated by the first mentioned device and for distinguishing, from a succession of changes of the two wave train signals between respective first and second states, four types of change of phase relation between the two wave train signals;
• gate and register means operatively connected with said processor means for timing and recording the interval required for each type of phase change and for accumulating a plurality of sets of records of timed intervals for each of the four types of change of phase relation between the two wave train signals;
• said processor means computing from the accumulated plurality of sets of records the mean time interval for a change of phase relation between the two wave train signals, comparing the computed mean time interval with the accumulated sets of records of timed intervals and determining the one type of phase change for which the difference from the mean time interval is the greatest, and deriving, from the record of timed intervals which has the greatest difference from the mean time interval and the computed mean time interval, a quality signal representative of the performance of the device generating the wave train signals;
• and
• means operatively connected with said processor means for displaying the quality signal.

An apparatus for evaluating the performance of a quadrature encoder which generates two electrical wave train signals indicative of the movement of a mechanical component, each wave train signal varying between first and second states and the two wave train signals normally being out of phase one with the other, the apparatus comprising:

• processor means for receiving the two wave train signals and for distinguishing, from the succession of changes of the signals between respective first and second states, sets of four types of change of phase relation between the two signals,
• gate and register means operatively connected with said processor means for timing and recording the interval required for each type of phase change in each set and for accumulating a plurality of sets of records of timed intervals for phase changes,
• said processor means functioning for computing from the accumulated plurality of sets of records the mean time interval for a phase change;
• for comparing the computed mean time interval with the accumulated sets of records of timed intervals and determining the type of phase change for which the difference from the mean time interval is the greatest;
• and for deriving from the record of timed intervals which has the greatest difference from the mean time interval and the computed mean time interval an encoder quality signal representative of the performance of the quadrature encoder generating the wave train signals, and
• means operatively connected with said processor means for displaying the encoder quality signal.