Method for rotating a printer paper-feed roller

1. A method for rotating a printer paper-feed roller wherein the roller is driven by a DC (direct current) motor and wherein the method comprises the steps of:

a) applying a feedback-control signal to the motor until the roller reaches a desired rotational position, wherein the feedback-control signal is a function of an error signal, and wherein the error signal represents the difference between the actual rotational position and the desired rotational position of the roller; and

b) when the roller reaches the desired rotational position, removing the applied feedback-control signal from the motor and applying a direct-control biasing signal to the motor to reduce or prevent rollback of the roller when the feedback-control signal is removed from the motor.

2. The method of claim 1 , also including the step of determining when the roller reaches the desired rotational position using a rotary encoder.

3. The method of claim 1 , also including the step of initiating a hardware interrupt signal when the roller reaches the desired rotational position.

4. The method of claim 1 , wherein the direct-control biasing signal is chosen to prevent rollback of the roller when the feedback-control signal is removed from the motor.

5. The method of claim 1 , wherein the direct-control biasing signal and the feedback-control signal are PWM (pulse-width-modulated) signals having substantially the same PWM amplitude and substantially the same PWM frequency.

6. The method of claim 1 , wherein step b) applies the direct-control biasing signal whether or not rollback of the roller occurs.

7. A method for rotating a printer paper-feed roller wherein the roller is driven by a DC (direct current) motor and wherein the method comprises the steps of:

a) applying a feedback-control signal to the motor until the roller reaches a desired rotational position, wherein the feedback-control signal is a function of an error signal, and wherein the error signal represents the difference between the actual rotational position and the desired rotational position of the roller;

b) when the roller reaches the desired rotational position, removing the applied feedback-control signal from the motor and applying a direct-control biasing signal to the motor to reduce or prevent rollback of the roller when the feedback-control signal is removed from the motor, wherein the direct-control biasing signal is chosen to prevent rollback of the roller when the feedback-control signal is removed from the motor, and

c) reducing the direct-control biasing signal if the roller overshoots the desired rotational position, by a predetermined amount.

8. The method of claim 7 , also including the step of initiating a hardware interrupt signal when the roller overshoots the desired rotational position by the predetermined amount.

9. The method of claim 7 , wherein the direct-control biasing signal is substantially constant when the roller is between the desired rotational position and a rotational position which overshoots the desired rotational position by the predetermined amount.

10. The method of claim 7 , wherein the direct-control biasing signal is reduced to zero if the roller overshoots the desired rotational position by the predetermined amount.

11. The method of claim 10 , also including the step of initiating a hardware interrupt signal when the roller overshoots the desired rotational position by the predetermined amount.

12. A method for rotating a printer paper-feed roller wherein the roller is driven by a DC (direct current) motor and wherein the method comprises the steps of:

a) applying a feedback-control signal to the motor until the roller reaches a desired rotational position, wherein the feedback-control signal is a function of an error signal, and wherein the error signal represents the difference between the actual rotational position and the desired rotational position of the roller;

b) when the roller reaches the desired rotational position, removing the applied feedback-control signal from the motor and applying a direct-control biasing signal to the motor to reduce or prevent rollback of the roller when the feedback-control signal is removed from the motor, wherein the direct-control biasing signal is chosen to prevent rollback of the roller when the feedback-control signal is removed from the motor, and

c) reducing the direct-control biasing signal each time the roller overshoots the desired rotational position by one of a plurality of predetermined amounts.

13. The method of claim 12 , also including the step of initiating a hardware interrupt signal when the roller overshoots the desired rotational position by each one of the plurality of predetermined amounts.

14. The method of claim 12 , wherein the plurality of predetermined amounts includes a first amount, a second amount which is twice the first amount, and up to a last amount which is equal to the plurality of predetermined amounts times the first amount.

15. The method of claim 14 , wherein the direct-control biasing signal is reduced in half each time it is reduced.

16. The method of claim 12 , wherein the direct-control biasing signal is reduced in half each time it is reduced.

17. The method of claim 12 , wherein the direct-control biasing signal is substantially constant when the roller is between a position equal to the desired rotational position and the first smallest one of the plurality of predetermined amounts and a position equal to the desired rotational position and the second smallest one of the plurality of predetermined amounts.

18. The method of claim 12 , wherein the direct-control biasing signal is reduced to zero when the roller overshoots the desired rotational position by the largest one of the plurality of predetermined amounts.

19. A method for rotating a printer paper-feed roller wherein the roller is driven by a DC (direct current) motor and wherein the method comprises the steps of:

a) applying a feedback-control signal to the motor until the roller reaches a desired rotational position, wherein the feedback-control signal is a function of an error signal, and wherein the error signal represents the difference between the actual rotational position and the desired rotational position of the roller; and

b) when the roller reaches the desired rotational position, removing the applied feedback-control signal from the motor and applying a direct-control biasing signal to the motor to reduce or prevent rollback of the roller when the feedback-control signal is removed from the motor, wherein the direct-control biasing signal and the feedback-control signal are PWM (pulse-width-modulated) signals having substantially the same PWM amplitude and substantially the same PWM frequency, and wherein the direct-control biasing signal has a duty cycle of five percent or less.

20. A method for rotating a printer paper-feed roller wherein the roller is driven by a DC (direct current) motor and wherein the method comprises the steps of:

a) applying a PWM (pulse-width-modulated) feedback-control voltage signal to the motor until the roller reaches a desired rotational position, wherein the feedback-control voltage signal has a substantially constant PWM amplitude and a substantially constant PWM frequency;

b) when the roller reaches the desired rotational position, removing the applied feedback-control voltage signal from the motor and applying a PWM direct-control biasing voltage signal to the motor to reduce or prevent rollback of the roller when the feedback-control voltage signal is removed from the motor, wherein the direct-control biasing voltage signal has substantially the same PWM amplitude and frequency as that of the feedback-control voltage signal, and wherein the direct-control biasing voltage signal has a substantially constant duty cycle; and

c) reducing the duty cycle of the direct-control biasing voltage signal to a new substantially constant value if the roller overshoots the desired rotational position. by a predetermined amount.

21. The method of claim 20 , also including the steps of determining when the roller reaches the desired rotational position using a rotary encoder and initiating a hardware interrupt signal when the roller reaches the desired rotational position.

22. The method of claim 20 , wherein a single PWM pulse generator is used to apply the feedback-control voltage signal and the direct-control biasing voltage signal to the motor.

23. A method for rotating a printer paper-feed roller wherein the roller is driven by a DC (direct current) motor and wherein the method comprises the steps of:

a) applying a PWM (pulse-width-modulated) feedback-control voltage signal to the motor until the roller reaches a desired rotational position, wherein the feedback-control voltage signal has a substantially constant PWM amplitude and a substantially constant PWM frequency;

b) when the roller reaches the desired rotational position, removing the applied feedback-control voltage signal from the motor and applying a PWM direct-control biasing voltage signal to the motor to reduce or prevent rollback of the roller when the feedback-control voltage signal is removed from the motor, wherein the direct-control biasing voltage signal has substantially the same PWM amplitude and frequency as that of the feedback-control voltage signal, and wherein the direct-control biasing voltage signal has a substantially constant duty cycle; and

c) removing the applied direct-control biasing voltage signal if the roller overshoots the desired rotational position. by a predetermined amount.

24. The method of claim 23 , also including the steps of determining when the roller reaches the desired rotational position using a rotary encoder and initiating a hardware interrupt signal when the roller reaches the desired rotational position.

25. The method of claim 23 , wherein a single PWM pulse generator is used to apply the feedback-control voltage signal and the direct-control biasing voltage signal to the motor.