Microprocessor based motor control

• US 4,628,233 A
• Filed: 10/04/1985
• Issued: 12/09/1986
• Est. Priority Date: 03/23/1984
• Status: Expired

• Current Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Original Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Inventors: Bradus, Robert
• Primary Examiner(s): Shoop, Jr., William M.
• Assistant Examiner(s): Ip, Shik Luen Paul
• Application Number:
  US06/784,702
• Time in Patent Office: 431 Days
• Field of Search: 318/306, 318/307, 318/308, 318/311, 318/326, 318/327, 318/332, 318/334, 318/336, 318/430, 318/432, 318/433, 318/434, 318/436, 318/438, 318/466, 318/469, 318/474, 318/476 , 318/563, 318/565, 318/566, 318/567, 318/568, 318/571, 318/611, 318/615, 318/685, 318/689, 318/696, 318/800, 318/799, 318/801, 318/802, 318/805, 318/811, 318/569 , 318/490, 318/806, 318/439
• US Class Current: 388/809
• CPC Class Codes: H02P 25/145 whereby the speed is regulated by measuring the motor speed and comparing it with a given physical value, speed feedback
• CPC Class Codes: Y10S 388/902 Compensation
• CPC Class Codes: Y10S 388/912 Pulse or frequency counter
• CPC Class Codes: Y10S 388/917 Thyristor or scr

Abstract

A microprocessor based motor controller which provides open loop speed control at low conduction angles, closed loop speed control at high conduction angles, and a smooth transition between open loop and closed loop zones. In open loop, the motor speed is selected and is permitted to vary with applied load. In closed loop, the motor speed is held constant, substantially irrespective of load. In the transition zone, the motor is operated in a hybrid open loop, closed loop fashion.

Anti-kickback protection is also provided based on a percentage change in the motor'"'"'s rotational period.

Claims

1. A method of controlling a motor operable over a range of conduction angles comprising the steps of,

defining a first operating zone corresponding to conduction angles below a predetermined first angle;

defining a second operating zone corresponding to conduction angles between said first angle and a predetermined second angle greater than said first angle;

defining a third operating zone corresponding to conduction angles greater than said second angle;

selecting one of said operating zones and operating said motor according to the following

(a) for said first zone, operating said motor in an open loop configuration,

(b) for said second zone, varying the conduction angle in relation to the load, but not exceeding said second angle, to maintain a predetermined speed for conduction angles below said second angle,

(c) for said third zone, operating said motor in a closed loop configuration.

2. The method of claim 1 further comprising storing said first and second angles, producing a value indicative of a desired operating point within said operating zones, and comparing said value with said first and second angles and selecting one of said operating zones in accordance with said comparison.

3. The method of claim 1 wherein said first angle is determined such that operation of said motor at said first angle produces a no load speed on the order of ten thousand revolutions per minute (10,000 R.P.M.).

4. The method of claim 1 wherein said first angle corresponds to a conduction angle of approximately seventy degrees (70°

).

5. The method of claim 1 wherein said second angle corresponds to a conduction angle of approximately eighty-eight degrees (88°

).

6. The method of claim 1 wherein the step of operating said motor in a closed loop configuration comprises producing a speed signal having a periodic waveform, the frequency of which being proportional to the speed of said motor, determining the period of said speed signal producing an error signal dependent on said period, and using said error signal to maintain a preselected speed.

7. A method of controlling a motor operable over a range of conduction angles comprising the steps of:

determining a full feedback conduction angle corresponding to a predetermined motor speed;

determining an operator selected conduction angle;

comparing said full feedback conduction angle with said operator selected conduction angle and performing a selected one of the following steps (a) and (b) depending on whether said operator selected conduction angle is greater than or not greater than said full feedback conduction angle;

(a) if said operator selected conduction angle is greater than said full feedback conduction angle, operating said motor at said full feedback conduction angle;

(b) if said operator selected conduction angle is not greater than said full feedback conduction angle, operating said motor at said operator selected conduction angle.

8. The method of claim 7 wherein said full feedback conduction angle is determined in accordance with said operator selected conduction angle.

9. The method of claim 7 wherein said full feedback conduction angle is determined by determining a desired speed and determining said full feedback conduction angle in accordance with said desired speed.

10. The method of claim 9 wherein said desired speed is determined in accordance with said operator selected conduction angle.

11. The method of claim 9 wherein said desired speed is determined by comparing said operator selected conduction angle with a predetermined value and performing a selected one of the following steps (c) and (d) depending on whether said operator selected conduction angle is less than or not less than said predetermined value:

(c) if said operator selected conduction angle is less than said predetermined value, determining said desired speed to be a predetermined constant speed;

(d) if said operator selected conduction angle is not less than said predetermined value, determining said desired speed to be variable in accordance with said operator selected conduction angle.

12. The method of claim 11 wherein said predetermined value is approximately eighty-eight degrees (88°

).

13. The method of claim 11 wherein said predetermined constant speed is approximately ten thousand revolutions per minute (10,000 R.P.M.).

14. The method of claim 11 wherein in step (d) said desired speed is determined as a linear function of said operator selected conduction angle.

15. A method of controlling a motor operable over a range of conduction angles comprising the steps of:

determining an operator selected conduction angle and a first conduction angle in accordance with said operator selected conduction angle;

comparing said operator selected conduction angle with a predetermined value and performing a selected one of the following steps (a) and (b) in accordance with whether said operator selected conduction angle is less than or not less than said predetermined value;

(a) if said operator selected conduction angle is less than said predetermined value and greater than said first conduction angle, operating said motor at said first conduction angle; and

if said operator selected conduction angle is less than said predetermined value and not greater than said first conduction angle, operating said motor at said operator selected conduction angle;

(b) if said operator selected conduction angle is not less than said predetermined value, operating said motor at said first conduction angle.

16. The method of claim 15 wherein said first conduction angle is a full feedback conduction angle corresponding to a predetermined motor speed.

17. The method of claim 15 wherein said first conduction angle is determined by determining a desired speed and determining said first conduction angle in accordance with said desired speed.

18. The method of claim 17 wherein said desired speed is determined in accordance with said operator selected conduction angle.

19. The method of claim 15 wherein said predetermined value is approximately eight-eight degrees (88°

).

20. The method of claim 15 wherein said first conduction angle is determined by comparing said operator selected conduction angle with said predetermined value and performing a selected one of the following steps (c) and (d) depending on whether said operator selected conduction angle is less than or not less than said predetermined value:

(c) if said operator selected conduction angle is less than said predetermined value, determining said desired speed to be a predetermined constant speed;

(d) if said operator selected conduction angle is not less than said predetermined value, determining said desired speed to be variable in accordance with said operator selected conduction angle.

21. The method of claim 20 wherein said predetermined constant speed is ten thousand revolutions per minute (10,000 R.P.M.).

22. A method of detecting an impending kickback condition in a motor driven tool comprising:

(a) determining a first value indicative of the rotational period of said motor during a first time interval;

(b) determining a first limit value based upon a predetermined percentage of said first value;

(c) determining a second value indicative of the rotational period of said motor during a second time interval; and

(d) producing a predetermined response if said second value exceeds said first value by at least said first limit value.

23. The method of claim 22 further comprising:

adding said first limit value to said first value to produce a first test value;

comparing said first test value with said second value; and

producing said predetermined response if said second value exceeds said first test value.

24. The method of claim 23 further comprising determining a second test value by determining a second limit value based upon said predetermined percentage of said second value and adding said second limit value to said second value.

25. The method of claim 24 further comprising determining a third value indicative of the rotational period of said motor during a third time interval;

comparing said second test value with said third value; and

producing said predetermined response if said third value exceeds said second test value.

26. The method of claim 22 further comprising comparing said first value with a predetermined sensor limit value and disabling said predetermining response if said first value exceeds said sensor limit value.

27. The method of claim 22 further comprising delivering an alternating current to said motor in a succession of half cycles of alternating polarity;

and wherein said first value is determined during a first half cycle and said second value is determined during a later half cycle.

28. The method of claim 27 wherein said step of producing a predetermined response is performed at least once during each successive half cycle.

29. The method of claim 22 further comprising determining a kickback sensitivity value and wherein said first value is determined in proportion to said kickback sensitivity value.

30. The method of claim 29 wherein said kickback sensitivity value is determined in accordance with at least one preset conductive path.

31. The method of claim 22 wherein said step of producing a predetermined response includes interrupting the delivery of power to said motor.

32. The method of claim 31 wherein said step of producing a predetermined response further includes waiting for an instruction from the operator of said tool and continuing to interrupt the delivery of power to said motor until said instruction is received.

33. The method of controlling the speed of the motor in a power tool having variable speed selection means that is selectively operable by the operator of the tool, including:

a first condition wherein said motor is operated in an open loop configuration when said variable speed selection means is below a first predetermined setting which corresponds to a first power level;

a second condition wherein said motor is operated in a closed loop configuration when said variable speed selection means is above a second predetermined setting which corresponds to a second power level greater than said first power level; and

a third condition wherein said motor is operated at a power level between said first and second power levels when said variable speed selection means is above said first predetermined setting and below said second predetermined setting.

34. The method of claim 33 wherein in said third condition, the power level of the motor is varied between said first power level to a maximum of said second power level in accordance with variations in the load applied to the motor in order to maintain the speed of the motor substantially at a predetermined speed approximately equal to the no load speed of the motor at said first power level.

35. The method of controlling the speed of the motor in a power tool having a variable speed selection means that is selectively operable by the operator of the tool, including:

operating said motor in a first condition in an open loop configuration when said variable speed selection means is below a first setting corresponding to a first power level; and

operating said motor in a second condition when said variable speed selection means is above said first setting by varying the power level of the motor between said first power level to a maximum of a second power level greater than said first power level in accordance with variations in the load applied to the motor to maintain the speed of the motor substantially at a predetermined speed approximately equal to the no load speed of the motor at said first power level.

36. The method of claim 35 wherein in said second condition, the setting of said variable speed selection means corresponds to said second power level.

37. The method of controlling the speed of the motor in a power tool having variable speed selection means that is selectively operable by the operator of the tool, including:

operating said motor in an open loop configuration when said variable speed selection means is below a first setting corresponding to a first power level; and

operating said motor in a closed loop configuration when said variable speed selection means is at a second setting corresponding to a second power level greater than said first power level.

38. The method of claim 37 further including operating said motor so as to maintain the speed of said motor substantially constant at the speed corresponding approximately to the no load speed of the motor at said first power level when said variable speed selection means is between said first and second settings by varying the power of the motor between said first and second power levels in accordance with the load applied to the motor.

39. The method of controlling the speed of the motor in a power tool having variable speed selection means that is selectively operable by the operator of the tool, including:

operating said motor in an open loop configuration when said variable speed selection means is below a first setting corresponding to a first power level; and

operating said motor in a closed loop configuration wherein the setting of said variable speed selection means corresponds to a desired motor speed greater than the approximate no load speed of the motor at said first power level such that the power level of the motor is varied in accordance with the load applied to the motor to substantially maintain said desired speed.