Method and apparatus for controlling the rotation position of an object

• US 20030225484A1
• Filed: 12/17/2002
• Published: 12/04/2003
• Est. Priority Date: 06/04/2002
• Status: Active Grant

• Current Assignee: S-Printing Solution Co., Ltd. (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Chun, Young-Sun, Cho, Young-Wan
• Granted Patent: US 6,724,323 B2
• Time in Patent Office: Days
• US Class Current: 700/306
• CPC Class Codes: G05B 19/258 with a combination of feedback covered by G05B19/253 - G05B19/256
• CPC Class Codes: G05B 2219/42004 PD proportional derivative
• CPC Class Codes: G05B 2219/42237 Pwm pulse width modulation, pulse to position modulation ppm
• CPC Class Codes: G05B 2219/45187 Printer

Abstract

A method and an apparatus to control the rotation of an object. In the method, first and second actual control variables which vary as the object rotates are measured. It is determined whether the first actual control variable is smaller than a predetermined control variable. It is determined whether a period of time has elapsed if it is determined that the first actual control variable is smaller than the predetermined control variable. A difference between a physical quantity that is generated corresponding to the first actual control variable and the second actual control variable is obtained, and a control amount to control the object is determined by using the difference, if it is determined that the predetermined period of time has elapsed or the first actual control variable is larger than the predetermined control variable. Here, the predetermined control variable corresponds to a position to which the object should be rotated to stop the object at a desired position. The object stops precisely at the desired rotation position, thus enabling precise control of the amount of rotation of the object. The method and the apparatus may stop a roller precisely in a desired position when being used to control the rotation of the roller of an inkjet printer, thereby preventing the formation of black or white lines in a printed image.

Claims

1. A method of controlling a rotation position of an object, the method comprising:

measuring first and second actual control variables which vary as the object rotates;

determining whether the first actual control variable is smaller than a predetermined amount;

determining whether a period of time has elapsed in response to determining that the first actual control variable is smaller than the predetermined amount; and

obtaining a difference between a physical quantity that is generated corresponding to the first actual control variable and the second actual control variable, and determining a control amount to control the object using the obtained difference, in response to determining that the period of time has elapsed or the first actual control variable is larger than the predetermined amount,

wherein the predetermined amount corresponds to a position at which the object is rotated to stop the object at a desired position.

2. The method of claim 1, wherein the obtaining of the difference comprises:

generating the physical quantity corresponding to the first actual control variable in response to determining that the period of time has elapsed or the first actual control variable is larger than the predetermined amount;

subtracting the second actual control variable from the physical quantity corresponding to the first actual control variable and determining a result of the subtracting as the obtained difference; and

determining the control amount by proportionally integrating the obtained difference in response to determining that the period of time has elapsed, and determining the control amount by proportionally differentiating the obtained difference in response to determining that the first actual control variable is larger than the predetermined amount.

3. The method of claim 1, wherein the first actual control variable corresponds to a rotation angle of the object and the second actual control variable corresponds to a rotation speed of the object.

4. An apparatus to control a rotation position of an object, the apparatus comprising:

a control variable measuring unit which measures first and second actual control variables that vary as the object rotates;

a control signal generator which compares the first actual control variable input from the control variable measuring unit with a predetermined value and outputs the result of the comparison as a control signal; and

a control amount determiner which compares the second actual control variable with a physical quantity that is generated corresponding to the first actual control variable at regular intervals of a period of time or irregularly in response to the output control signal and determines a control amount from a result of the comparison,

wherein the object operates in response to the control amount.

5. The apparatus of claim 4, wherein the control variable measuring unit comprises:

an encoder which senses the rotation of the object and outputs the result of the sensing in the form of a square wave;

a first counter which counts a rising or a falling edge of the square wave and outputs the result of the counting as the first actual control variable; and

a distance measuring unit which measures a distance between the rising or the falling edges of the square wave and outputs the result of the measurement as the second actual control variable.

6. The apparatus of claim 5, wherein the distance measuring unit comprises a second counter which performs a counting operation starting from the falling edge of the square wave and ending at the next rising edge of the square wave, in response to a system clock signal, and outputs the result of the counting operation as the second actual control variable.

7. The apparatus of claim 5, wherein the control variable measuring unit further comprises:

a first storage unit which stores the first actual control variable output from the first counter; and

a second storage unit which stores the second actual control variable output from the distance measuring unit.

8. The apparatus of claim 4, wherein the control signal generator comprises:

a third storage unit which stores the predetermined value; and

a comparator which compares the first actual control variable measured by the control variable measuring unit with the predetermined value stored by the third storage unit and outputs a result of the comparison as the control signal.

9. The apparatus of claim 4, wherein the control amount determiner comprises:

a physical quantity generator which generates the physical quantity corresponding to the first actual control variable in response to a timing signal or the control signal;

a subtractor which subtracts the second actual control variable from the physical quantity and outputs a result of the subtraction as an error;

a control unit which determines a control voltage from the outputted error in response to the timing signal; and

a timer which generates the timing signal at the intervals of the predetermined period of time,

wherein the control amount is determined to correspond to the control voltage.

10. The apparatus of claim 9, wherein the control amount determiner comprises:

a pulse width modulator which outputs a pulse width-modulated signal having a duty that varies corresponding to the control voltage; and

a driver which generates the control amount in the form of a current corresponding to the pulse width-modulated signal and outputs the control amount to the object.

11. The apparatus of claim 9, wherein the control unit determines the control voltage from the error in response to the timing signal or the control signal.

12. The apparatus of claim 11, wherein the control unit comprises:

a first controller which determines the control voltage by proportionally integrating the error in response to the timing signal; and

a second controller which proportionally differentiates the error and determines the control voltage in response to the control signal.

13. The apparatus of claim 12, wherein the first controller comprises:

a first multiplier which multiplies a first weight and the error together and outputs a result of the multiplication;

an integrator which integrates the error and outputs a result of the integration;

a second multiplier which multiplies the result of the integration by a second weight and outputs a result of the multiplication; and

a first adder which adds the result of the multiplication in the first multiplier and the result of the multiplication in the second multiplier and outputs a result of the addition as the control voltage,

wherein the first and second multipliers, the integrator, and the first adder operate in response to the timing signal.

14. The apparatus of claim 12, wherein the second controller comprises:

a first multiplier which multiplies a first variable weight and the error together and outputs a result of the multiplication;

a differentiator which differentiates the error and outputs a result of the differentiation;

a second multiplier which multiplies the result of the differentiation of the differentiator by a second variable weight and outputs a result of the multiplication; and

a second adder which adds the result of the multiplication in the first multiplier and the result of the multiplication in the second multiplier and outputs a result of the addition as the control voltage,

wherein the first and second variable weights vary in response to the first actual control variable, and the first multiplier, the differentiator, the second multiplier, and the second adder operate in response to the control signal.

15. The apparatus of claim 5, wherein the encoder comprises:

a light-emitting unit to emit light;

a rotating circular plate having a plurality of holes to rotate with the object, the emitted light passing through the holes; and

a light-receiving unit to receive the passed light, and convert the received light to the square wave.

16. A method of controlling a rotating object, the method comprising:

measuring first and second control variables of the object;

generating a third control variable which corresponds to the first control variable;

obtaining a difference between the second and third control variables; and

determining a control amount to control the object using the obtained difference.

17. The method of claim 16, further comprising:

determining whether the first control variable is larger than a predetermined amount; and

determining whether a period of time has elapsed in response to determining that the first actual control variable is not larger than the predetermined amount,

wherein the obtaining of the difference occurs only in response to determining that the first control variable is larger than the predetermined amount, or the period of time has elapsed.

18. The method of claim 17, wherein the first and second control variables vary as the object rotates.

19. The method of claim 18, wherein the predetermined amount corresponds to a position to which the object is rotated to stop the object at a desired position.

20. The method of claim 19, wherein the first control variable is a position of the object, and the second control variable is a speed of the object.

21. The method of claim 18, wherein the predetermined amount corresponds to a position where a rotation speed of the object starts to change.

22. The method of claim 18, wherein the third control variable is regularly generated.

23. The method of claim 18, wherein the third control variable is irregularly generated.

24. An apparatus to control a rotating object, comprising:

a measuring unit to measure first and second control variables of the object;

a generator to generate a third control variable which corresponds to the first control variable; and

a control amount determiner to obtain a difference between the second and third control variables and determine a control amount to control the object using the obtained difference.

25. The apparatus of claim 24, wherein the generator determines whether the first control variable is larger than a predetermined amount, and determines whether a period of time has elapsed in response to determining that the first control variable is not larger than the predetermined amount, and the control amount determiner obtains the difference only in response to determining that the first control variable is larger than the predetermined amount, or the period of time has elapsed.

26. A printer comprising:

a rotating object; and

an apparatus to control the rotating object, comprising;

a measuring unit to measure first and second control variables of the rotating object;

a generator to generate a third control variable which corresponds to the first control variable; and

a control amount determiner to obtain a difference between the second and third control variables and determine a control amount to control the object using the obtained difference.