Counter based circuit for measuring movement of an object
An apparatus for measuring movement of an object has a quadrature incremental encoder for providing first and second phases of encoder pulses corresponding to incremental displacements of the object. A first counter counts edges of the encoder pulses according to the sense of the displacement. Clock pulse counts are also made. Acquiring movement data at periodic speed processing moments includes the decoder adjusting encoder pulse data from the first counter using a clock pulse count that is a function of a lapse of time between when the most recent edge of the encoder pulses and the speed processing moment. The clock pulse counts are reset by edges of the first and second phases of the encoder pulses when the decoder acquires the movement data.
1. A measuring apparatus for measuring movement of an object that has a quadrature incremental encoder for providing first and second phases of encoder pulses corresponding to incremental displacements of the object, the measuring apparatus comprising:
a first counter for providing encoder pulse counts according to a sense of the displacement;
a clock for providing clock pulses at a defined frequency;
a further counter connected to the clock for providing clock pulse counts;
a decoder for acquiring movement data at periodic speed processing moments as a function of the encoder pulse counts and the clock pulse counts,
wherein the decoder acquiring movement data includes adjusting encoder pulse data from the first counter using a clock pulse count that is a function of a lapse of time between a most recent edge of the encoder pulses and the speed processing moment when the decoder acquires the movement data, and
wherein the clock pulse counts are reset by the first and second phases of the encoder pulses when the decoder acquires the movement data, and
a control module for controlling a motor drivingly coupled to the object, wherein the control module controls the motor as a function of the movement data from the decoder.
2. The apparatus of claim 1 , wherein the further counter includes second and third counters for providing the clock pulse counts, wherein the second and third counters are reset by the first and second phases of the encoder pulses respectively.
3. The apparatus of claim 1 , wherein the further counter is a common counter providing the clock pulse counts, and is reset by the first and second phases of the encoder pulses when the decoder acquires the movement data.
4. The apparatus of claim 1 , wherein when an edge of an encoder pulse has occurred since a previous speed processing moment, the decoder acquiring movement data includes adjusting encoder pulse data from the first counter using a clock pulse count that is a function of a lapse of time between the most recent edge of the encoder pulses and the current processing moment.
5. The apparatus of claim 1 , wherein when an edge of an encoder pulse has occurred since a previous speed processing moment, the decoder adjusting encoder pulse data from the first counter increases a measured value of speed as a function of the lapse of time between the most recent edge of the encoder pulses and the current processing moment.
6. The apparatus of claim 1 , wherein the decoder adjusting encoder pulse data from the first counter decreases the value of speed measured as a function of the lapse of time between a most recent edge of the encoder pulses and a previous processing moment.
7. The apparatus of claim 6 , wherein when no edge of an encoder pulse has occurred since the previous speed processing moment, the decoder acquiring movement data includes using a count of the number of speed processing moments since the most recent edge of the encoder pulses.
8. The apparatus of claim 1 , wherein when a direction of movement has changed since a previous processing moment, the decoder adjusts the value of speed measured to zero.
9. The apparatus of claim 1 , wherein when no edge of an encoder pulse has occurred since a previous speed processing moment, and the time since the previous encoder pulse in a current processing moment is less than the time since a preceding encoder pulse and the previous processing moment, the decoder leaves the value of speed measured unchanged.
10. The apparatus of claim 1 , wherein when the number of speed processing periods with no edges of encoder pulses in a current processing moment exceeds a predetermined limit, the decoder adjusts the value of speed measured to zero.
11. A method of measuring movement of an object, wherein a quadrature incremental encoder provides first and second phases of encoder pulses corresponding to incremental displacements of the object, the method comprising:
providing encoder pulse counts from a first counter according to a sense of the displacement;
providing clock pulses at a defined frequency by a clock;
providing clock pulse counts with a further counter;
acquiring movement data at periodic speed processing moments as a function of the encoder pulse counts and the clock pulse counts using a decoder, including adjusting encoder pulse data from the first counter using a clock pulse count that is a function of a lapse of time between a most recent edge of the encoder pulses and the speed processing moment when the decoder acquires the movement data;
resetting the clock pulse counts by the first and second phases of the encoder pulses when the decoder acquires the movement data; and
controlling a motor with a control module, wherein the motor is drivingly coupled to the object, and wherein the control module controls the motor as a function of the movement data from the decoder.
12. The method of claim 11 , wherein second and third counters provide the clock pulse counts, wherein the second and third counters are reset by the first and second phases of the encoder pulses respectively.
13. The method of claim 11 , wherein when an edge of an encoder pulse has occurred since the previous speed processing moment, acquiring movement data includes adjusting encoder pulse data from the first counter using a clock pulse count that is a function of a lapse of time between a most recent edge of the encoder pulses and the current processing moment.
14. The method of claim 13 , wherein when an edge of an encoder pulse has occurred since the previous speed processing moment, adjusting encoder pulse data from the first counter increases the value of speed measured as a function of the lapse of time between the most recent edge of the encoder pulses and the current processing moment.
15. The apparatus of claim 11 , wherein adjusting encoder pulse data from the first counter decreases the value of speed measured as a function of the lapse of time between a most recent edge of the encoder pulses and a previous processing moment.
16. The method of claim 15 , wherein when no edge of an encoder pulse has occurred since the previous speed processing moment, acquiring movement data includes using a count of the number of speed processing moments since the most recent edge of the encoder pulses.
17. The method of claim 11 , wherein when the direction of movement has changed since the previous processing moment, the value of speed measured is adjusted to zero.
18. The method of claim 11 , wherein when no edge of an encoder pulse has occurred since the previous speed processing moment, and the time since the previous encoder pulse in a current processing moment is less than the time since a preceding encoder pulse and the previous processing moment, the value of speed measured is left unchanged.
19. The method of claim 11 , wherein when the time since the previous encoder pulse in a current processing moment exceeds a predetermined limit, the value of speed measured is adjusted to zero.