Method and apparatus for controlling a physical parameter

• US 6,091,887 A
• Filed: 06/02/1998
• Issued: 07/18/2000
• Est. Priority Date: 12/04/1995
• Status: Expired due to Term

• Current Assignee: Ebm-Papst St Georgen GmbH & Company KG (Ebm-Papst Mulfingen GmbH & Company KG)
• Original Assignee: Papst-Motoren GmbH & Company KG
• Inventors: Karwath, Arno, Dieterle, Roland, Rappenecker, Herman
• Primary Examiner(s): MARTIN, DAVID S
• Application Number:
  US09/077,650
• Time in Patent Office: 777 Days
• Field of Search: 388/800-811, 312/432, 312/434, 312/811, 312/599, 375/238, 702/79
• US Class Current: 388/811
• CPC Class Codes: G05B 11/28 using pulse-height modulation; using pulse-width modulation
• CPC Class Codes: H02P 6/08 Arrangements for controlling the speed or torque of a single motor H02P6/10, H02P6/28 take precedence
• CPC Class Codes: H02P 7/2913 whereby the speed is regulated by measuring the motor speed and comparing it with a given physical value

Abstract

The invention relates to a method for adjusting a real value (actual value) of a physical quantity to a preset value (target value) with the following steps:

(a) the difference between the target value and the actual value (referred to below as the control deviation) and its sign (referred to below as the control sign) is determined repeatedly at interval; (b) the control deviation is converted into at least one electrical signal during or after each measurement, and the duration thereof (referred to below as the control deviation duration) is proportional to the absolute value of the control deviation at least in the range of the target value, and the value thereof is a function of the control sign; (c) the charge of an analog electrical memory arrangement is affected by this at least one electrical signal during the control deviation duration; (d) depending on the value of the charge of the memory arrangement, the physical quantity is directly or indirectly affected to keep it in the range of the target value. Said control method, which is partially based on analog and partially on digital components produces, for a motor which uses a microprocessor for commutating or controlling, a rotation speed controller with a very simple structure.

Claims

1. A method of controlling an actual value of a physical parameter to a target value, comprising the steps of:

a) repetitively measuring, at time intervals, the deviation or difference of the actual value from the target value, hereinafter referred to as control deviation, and the sign of said difference, hereinafter referred to as control sign;

b) during or after each measurement, converting said control deviation into at least one electrical signal whose duration, referred to hereinafter as control deviation duration, is proportional to the absolute value of the control deviation, at least in a range near the target value and whose value is a function of the control sign;

c) controlling a charge on an analog electrical memory element as a function of said at least one electrical signal, during the control deviation duration; and

d) controlling said physical parameter as a function of said charge of said electrical memory element, thereby keeping the physical parameter within a predetermined desired range adjacent said target value.

2. A method according to claim 1, further comprising

performing said converting of the control deviation into an electrical signal in a microprocessor (20;

20'"'"') and

generating said electrical signal at at least one output of the microprocessor as a digital or ternary signal, during or after a measurement, during the control deviation duration or during a time proportional to the control deviation duration.

3. A method according to claim 1, wherein said memory element is a capacitor, and said controlling of charge on said analog electrical memory element is performed via a resistor arrangement, by controlling a current flow to or from the capacitor when the electrical signal is present, during the control deviation duration or during a time proportional to the control deviation duration.

4. A method according to claim 1, wherein said step of controlling said physical parameter is performed by controlling the pulse duty cycle (TV) of a Pulse Width Modulation (PWM) control device according to the amount of charge of the memory element, and using the output signal of the PWM control device to directly or indirectly control the physical parameter.

5. A method according to claim 1, further comprising

performing said measuring and converting steps digitally.

6. A method according to claim 1, wherein said charge-controlling step is executed in an analog fashion.

7. Method according to claim 1, wherein the control deviation (DIFF) is converted into the at least one electrical signal at the same time the control deviation is measured.

8. Method according to claim 1, wherein the control deviation (RGL-DIFF;

RGL-DIFF'"'"') is converted into the at least one electrical signal subsequent to measurement of the control deviation.

9. Method according to claim 8, wherein the control deviation, before being converted into the at least one electrical signal, is multiplied by a predetermined factor (C_g ;

F).

10. Method according to claim 1, wherein each of the control deviation and the control sign from a measurement preceding the current values are temporarily stored as moving average values and are converted, in addition to the current control deviation (RGL-DIFF), into at least one electrical additional signal whose duration is proportional to the absolute value of this temporarily stored control deviation (RGL-DIFF-Old), at least in a range near the target value, and whose value is a function of the temporarily stored control sign (VZ-S), and wherein the charge of the analog electrical memory element is furthermore affected by this at least one electrical additional signal.

11. Method according to claim 10, wherein an inverse value of temporarily stored control sign (VZ-S) with respect to the sign (VZ) of the current control deviation (RGL-DIFF) is used.

12. Method of controlling a physical parameter to a target value, comprising the following steps:

a) determining the absolute value and the sign or direction (positive or negative) of the control deviation (ε

) of the physical parameter measured by taking the deviation between the actual value and the target value of the physical parameter;

b) converting said control deviation according to a predetermined computing rule into binary or ternary electrical signals;

c) processing said binary or ternary electrical signals to control currents, to and from an analog electrical memory element; and

d) controlling said physical parameter as a function of a charge state of said analog electrical memory element, thereby keeping the physical parameter within a predetermined desired range adjacent said target value.

13. Method according to claim 12, wherein said step of controlling currents to and from the analog electrical memory element includes directing said currents through resistors of a predetermined value.

14. Method of controlling the rotation speed of a motor having a rotor and a stator, comprising the steps of,

a) at a predetermined first angular position (FIG. 10:

α

₁) of the rotor relative to the stator, starting a change, in the charge of a first memory element (34), as a function of time;

b) determining a measurement instant (FIG. 8;

t1;

FIG. 10;

t7) at which the charge (u₃₄) of the first memory element (34) reaches a predetermined value ("target value");

c) if the measurement instant (FIG. 8;

t1) occurs before a second measurement point (FIG. 8;

t2) at which the rotor during operation has covered a predetermined angular interval (FIG. 10;

β

) relative to the first angular position (FIG. 10;

α

₁), changing the charge of a second memory element (84), as a function of time in a time interval (FIG. 8;

t1 to t2) from the measurement instant to the second measurement point, in a predetermined direction;

d) if the measurement point (FIG. 10;

t7) occurs later than the second measurement instant (FIG. 10;

t6), changing the charge of a second memory element (84), as a function of time during the time interval between the two measurement instants (FIG. 10;

t6 to t7), in a direction opposite to the predetermined direction; and

e) controlling the amount of energy supplied to the motor per unit time (FIG. 1;

FIG.

     15) as a function of the value of the charge of the second memory element (84).

15. Method according to claim 14, wherein the energy supplied to the motor comprises a pulsed electrical current (i) and said energy-controlling step is performed using pulse width modulation (PWM) by changing the pulse duty cycle (TV) as a function of the amount of charge on the second memory element (84).

16. Method according to claim 14 wherein the first angular position (FIG. 10:

α

₁) is determined by the change in potential of the output signal of a Hall sensor (FIG. 15;

     234) provided on the motor, wherein the change in potential is generated by the transition from a North pole to a South pole or vice versa.

17. Method according to claim 16, wherein the predetermined angular interval (β

) is defined by an essentially constant range of the output voltage of the Hall sensor (234) which follows the first angular position (α

₁).

18. Method according to claim 15 further comprising controlling current in the motor using a PWM control device (60) capable of adjusting the pulse duty cycle (TV) of the output signal as a function of a control voltage supplied to its input (62), and wherein the control voltage for a pulse duty cycle of 0% is different from zero and has the same sign as control voltages required for non-zero pulse duty cycles.

19. Method according to claim 14, wherein if the measurement instant (FIG. 8:

t₁) occurs before the second measurement instant (FIG. 8;

t₂), then the change in charge on the second memory element (84) in the predetermined direction occurs at a first time-dependent rate whose absolute value is larger than the absolute value of a second time-dependent rate at which the changes in the charge occurs, if the measurement instant (t₇) occurs after the second measurement instant (t₆).

20. Method according to claim 14, further comprising controlling charging and discharging of said first memory element (34) by a microprocessor (20).

21. Method according to claim 20, further comprising controlling charging and discharging of said first memory element (34) and said second memory element (84) by executing in said microprocessor (20) a computer program having a binary decision tree structure.

22. Method according to claim 21, wherein the program, for controlling the charging and discharging of the first and the second memory elements (34,84), has the form of repetitive loops with a short duration which have substantially the same duration, independent of the current branch path of executing the loop.

23. Method according to claim 22, wherein there are provided, in the path of a loop, testing or polling points for polling the charge state of the first memory element (34), which points cause different portions of the program loop to be executed, depending upon the charge state.

24. Method according to claim 20, wherein at least one electrical signal having a duration which is proportional to the absolute value of the control deviation (ε

), is generated essentially in parallel with determination of the control deviation.

25. Method according to claim 20, wherein the actual value of the parameter to be controlled is obtained, and the value and the sign of the control deviation (ε

) are determined by comparison with a target value, and wherein subsequently the at least one electrical signal, whose duration is proportional to the absolute value of the control deviation (ε

), is generated in parallel with determination of the subsequent value of the actual value.

26. Arrangement for carrying out a method of controlling a physical parameter to a predetermined target value by repetitively measuring, at time intervals, the deviation or difference of the actual value from the target value and the sign of said difference, hereinafter "control sign," converting said control deviation into an electrical signal whose duration, hereinafter referred to as control deviation duration, is proportional to the absolute value of said control deviation and whose value is a function of the control sign, controlling, during said control signal deviation, a charge on an analog electrical memory element as a function of said electrical signal, and controlling said physical parameter as a function of said charge on said electrical memory element, comprising

a microprocessor (20, 20'"'"'), wherein, during operation, there is executed in the microprocessor (20, 20'"'"') a program for converting a control deviation (ε

) with a given value and sign into at least one electrical signal at at least one output (B1, B2;

B31, B32) of said microprocessor, the duration of the electrical signal being proportional to the absolute value and wherein the magnitude of the electrical signal has a discrete electrical value which depends on the sign.

27. Arrangement according to claim 26, wherein the at least one output of said microprocessor is connected via an ohmic resistor (FIG. 43:

R0, R1, R2), to a memory element (84;

     504).

28. Arrangement according to claim 27, wherein several outputs (FIGS. 31 and 43:

B31, B32, B33) are provided, each associated with a separate ohmic resistor (R0, R1, R2), for connection to the memory element (84;

     504).

29. Arrangement according claim 27, wherein the ohmic resistors (FIG. 21:

90", 94", 318", 322") are at least partially adjustable.

30. Arrangement according to claim 28, wherein the resistors (R0, R1, R2) which are connected to a plurality of outputs, are connected to each other and via a common resistor (FIG. 43:

R_g) to the memory element (84;

     504).

31. Arrangement according to claim 30, wherein the common resistor (FIG. 43:

R_g) is adjustable for adjusting several control parameters simultaneously.

32. Arrangement according to claim 26, wherein the microprocessor (20;

20'"'"') comprises two outputs (FIG. 3;

B1, B2) which can be switched by the program between LOW and HIGH impedance, and wherein both outputs are connected to the memory element (84;

     504) via a diode (88,

     92) connected in series with an impedance (90,

     94), the diodes (88,92) being polarized in opposite directions and one of the outputs being connected to a voltage source via an impedance (95).

33. Arrangement according to claim 32, wherein the impedances (90, 94) have different values for generating different time constants for charging and discharging the memory element (84;

504).

34. Arrangement according to claim 32, wherein the memory element is an integrator (504).

35. Arrangement according to claim 34, wherein the integrator (504) comprises an operational amplifier (508) and wherein a capacitor (512) is disposed between the output (510) and an input (506) of the operational amplifier (508).

36. Arrangement according to claim 26, wherein the impedance is a constant current device (FIG. 46:

500,

     502).

37. Motor for carrying out a method of controlling a physical parameter to a predetermined target value by repetitively measuring, at time intervals, the difference between the target value and the actual value, hereinafter "control deviation," and the sign of said difference, hereinafter "control sign," converting said control deviation into an electrical signal whose duration, hereinafter referred to as control deviation duration, is proportional to the absolute value of said control deviation and whose value is a function of the control sign, controlling, during said control signal deviation, a charge on an analog electrical memory element as a function of said electrical signal, and controlling said physical parameter as a function of said charge on said electrical memory element, comprising a microprocessor (20;

20'"'"'), wherein the output signals (B1, B2) of the microprocessor (20;

20'"'"') control the change in the charge of a second memory element (84;

     504).

38. Motor according to claim 37, wherein the microprocessor (20;

20'"'"') comprises two outputs (B1, B2) and each of the outputs is switchable between the logical values "1" and "0".

39. Motor according to claim 38, wherein to each output (B1, B2) there are connected, in series, a resistor and a diode (94, 92;

and 90, 88, respectively), each of the respective resistors and diodes connected in series being connected to the second memory element (84;

     504) and the forward directions of the two diodes (88,

     92) being opposite.

40. Motor according to claim 39, wherein the resistors (90,94) have different values.

41. Motor according to claim 40, further comprising a circuit controlling the rotation speed, wherein a first one (94) of said resistors which is associated with the change in the charge of the second memory element (84;

504) when the rotation speed is too low, is smaller than the other (90) of said resistors.

42. Motor according to claim 37, wherein the second memory element is a capacitor (84) and wherein the voltage of the capacitor (84) is supplied to the input (62) of a pulse width modulation (PWM) controller (60) via an adjustable high impedance resistor (80), said input (62) being connected via a resistor (72, 70, 66) variable as a function of the motor current (i;

i1, i2) to a potential which causes the pulse duty cycle (TV) of the PWM control device (60) to decrease, when a current flows from the input (62) of the PWM control device (60) via the variable resistor (66, 70,

     72) to this potential.

43. Motor according to claim 42, wherein the PWM controller (60) comprises a sawtooth generator (180) and a comparator (182), wherein a sawtooth voltage (208) is supplied by the sawtooth generator (180) to one input of the comparator (182), and an input signal is supplied to the other input of the comparator (182) by the second memory element (84;

504).

44. Motor according to claim 43, wherein the sawtooth signal (208) of the sawtooth generator (180) oscillates between a minimum value which is different from zero, and a maximum value which is different from zero.

45. Motor according to claim 43, wherein the sawtooth generator (180) comprises a comparator (186), the output (188) of the comparator (186) being connected to the negative input (196) via a negative feedback (194) and to the positive input (192) via a positive feedback (190), and wherein a storage capacitor (198) is associated with the negative input (196).

46. Motor according to claim 42, wherein there is provided at least one filter (70, 72, 76) between a current measurement device (58) for the motor current (i) and the input (62) of the PWM controller (60).

47. Motor according to claim 46, wherein the at least one filter is a T-filter (70, 72, 76).