Machine process controller

• US 4,279,013 A
• Filed: 10/31/1979
• Issued: 07/14/1981
• Est. Priority Date: 10/31/1979
• Status: Expired due to Term

• Current Assignee: Gte Valeron Corp. (Verizon Communications Inc.)
• Original Assignee: Valeron Corp. (Sandvik AB)
• Inventors: Cook, Kenneth J., Neff, Vance E., Cameron, Larry E., Rowland, Keith L.
• Primary Examiner(s): Ruggiero, Joseph F.
• Application Number:
  US06/089,436
• Time in Patent Office: 622 Days
• Field of Search: 364/474, 364/475, 364/105, 364/119, 364/506, 364/511, 364/483, 364/550, 318/571, 318/563, 318/565, 318/650, 318/561, 318/39, 409/145, 409/148, 409/150, 409/151, 409/153, 409/154, 409/156, 409/80, 408/9, 408/10, 408/11, 408/12, 408/13, 408/16, 324/142, 73/104, 73/105, 73/117, 73/117.3, 73/117.4, 73/116
• US Class Current: 700/33
• CPC Class Codes: G05B 19/4163 Adaptive control of feed or cutting velocity without NC B23Q15/12
• CPC Class Codes: G05B 2219/34215 Microprocessor
• CPC Class Codes: G05B 2219/34465 Safety, control of correct operation, abnormal states
• CPC Class Codes: G05B 2219/34466 Bad circuits, watchdog, alarm, indication
• CPC Class Codes: G05B 2219/37285 Load, current taken by motor
• CPC Class Codes: G05B 2219/41027 Control signal exponentially to error
• CPC Class Codes: G05B 2219/43152 Feed in, transfer line, rapid traverse to work, grip speed
• CPC Class Codes: G05B 2219/43158 Feedrate override

Abstract

The controller includes a power sensing device which monitors the instantaneous power drawn by the machine and compares it with a predetermined limit level of desired power consumption. A user programmable timer is manually accessible for loading a selected time delay period therein. The controller provides an output capable of altering the machine operation when the machine power consumption has continuously exceeded the limit value for the selected time period. The controller outputs may be latched or nonlatched once an overlimit condition is detected in accordance with a user selectable programmed parameter. In an adaptive mode, the controller forces the feed rate to a programmable feed rate for a selected period of time upon initial impact between the workpiece and the machine tool. The controller then maintains a normal adaptive power level in which the feed rate response may be selectively altered as a percentage of an exponential function of the difference between the actual machine power consumption and the programmable desired adaptive power level. Provision is made for automatically referencing the feed rate control signal to the voltage rating of the feed rate drive motor in the machine.

Claims

1. A controller for a machine having a tool for removing material from a workpiece, said controller comprising:

sensing means for monitoring the power used by the machine;

limit setting means for supplying a first limit value defining a first extreme level of power consumption for the machine;

comparison means for comparing outputs of said sensing means and said limit setting means, operative to provide an output signal if the machine power consumption has exceeded the limit value;

firsrt programmable timer means capable of storing a selectively alterable time period;

manually actuable means for loading said timer means with a selected time period; and

output means capable of altering the machine operation when the machine power consumption has continuously exceeded the limit value for said selected time period whereby electrical noise and expected fluctuations peculiar to the machine operation may be accommodated without disturbing the optimum machine operating conditions.

2. The controller of claim 1 wherein said limit setting means further comprises:

means for supplying a second limit value whereby to define a machine operational power window in conjunction with said first limit value for machine power consumption.

3. The system of claim 2 which further comprises:

a memory; and

means for loading said first and second limit values into selected memory locations.

4. The controller of claim 3 which further comprises:

a microprocessor, operative for fetching said first and second machine power consumption limits from the memory and comparing said limits within the machine power consumption as sensed by the sensing means.

5. The controller of claim 1 which further comprises:

a memory;

a keyboard coupled to said memory, operative to load a count signal related to the selected time period into a particular memory location.

6. The controller of claim 5 which further comprises:

means for periodically decrementing the count signal in said timer means when the machine power consumption has exceeded said limit value; and

means for periodically reinitializing the count signal in said timer means when the machine power consumption is within said limit value.

7. The controller of claim 6 which further comprises:

a microprocessor program means having a block of instructions stored in said memory for operating said microprocessor, said block of instructions being periodically executed in a cyclical fashion; and

second programmable timer means controlling the cycle time for said block of instructions.

8. The controller of claim 7 wherein said program means instructs said microprocessor to compare the machine power consumption with said limit value, reinitialize the count signal in said first timer means if said machine power conconsumption is within limit, and decrement said first timer means if the machine power consumption has exceeded said limit value;

and

means for interrogating the contents of said timer means and providing a signal to said output means to alter the machine operation if said timer means has timed out.

9. The controller of claim 3 which further comprises:

a programmable surge delay timer stored in said memory, operative to disable said comparison means until a selected time period has elapsed after machine start up.

10. The controller of claim 9 which further comprises:

means for sensing power initially applied to said machine, operative to begin the timing of said programmable surge delay timer.

11. The controller of claim 1 wherein said output means includes at least one dedicated output line, and wherein said controller further comprises:

programmable means for latching or nonlatching the signal state of the output line once the machine power consumption has exceeded said limit value for the selected time period.

12. The controller of claim 11 which further comprises:

a memory;

a keyboard communicating with said memory for supplying a latch signal to the memory indicating whether the status of the dedicated output line should be latched or nonlatched once the limit value has been exceeded; and

means for checking the memory for the presence of said latch signal when the machine power consumption is within said limit value to thereby determine the state of the signal provided to the dedicated output line once the machine power consumption is again within said limit value.

13. A method of adaptively controlling an automated machine having a tool for machining a workpiece, said method comprising:

storing an air cut feed rate value in a memory for determining the machine feed rate when the tool is not in contact with the workpiece;

storing an impact feed rate in a memory for determining the machine feed rate upon initial impact between the machine tool and workpiece;

storing a selected adaptive power level in a memory for determining the desired machine power consumption during normal machine operation after impact;

sensing the power consumed by the machine;

comparing said machine power consumption with a preselected limit value;

driving said machine at the air cut feed rate until the machine power consumption exceeds said limit value;

driving said machine at said impact feed rate for a predetermined amount of time to stabilize machine operation once the power consumption has exceeded the limit value; and

thereafter, driving said machine at a feed rate necessary to maintain the machine power consumption at the adaptive power level.

14. The method of claim 13 wherein said impact feed rate is slower than the air cut rate.

15. The method of claim 13 which further comprises:

loading a timer with an impact feed rate hold time representative of the time necessary to stabilize machine operation upon impact of the machine tool with the workpiece;

activating said timer when the machine power consumption exceeds the limit value; and

maintaining the feed rate at the impact feed rate until the impact feed rate hold time has elapsed.

16. The method of claim 13 which further comprises:

continuously monitoring the error difference between the actual power consumed by the machine and the adaptive power level stored in the memory; and

generating a new adjusted feed rate level until the actual power consumption is substantially equivalent to the desired adaptive power level.

17. The method of claim 16 which further comprises:

comparing the actual power consumption with the desired adaptive power level;

providing a feed rate change value as a function of the error difference therebetween;

adding the feed rate change value to the current feed rate if the actual power consumption is below the desired adaptive power level; and

subtracting the feed rate change value from the current feed rate if the actual power consumption is above the desired adaptive power level.

18. The method of claim 17 wherein said feed rate change value varies exponentially with the error difference between the actual machine power consumption and the desired adaptive power level to thereby stabilize machine operation at low error levels and provide fast recovery at high error levels.

19. The method of claim 18 wherein said feed rate change value is generated according to the formula:

FEED RATE CHANGE=2.sup.(ERROR)

where ERROR is the difference between the actual machine power consumption and the desired adaptive power level.

20. The method of claim 19 wherein the feed rate change value is generated by a 2 step digital approximation which includes the summation of a feed rate segment value associated with a beginning point in a segment of values and a feed rate interpolative value derived from a linear interpolation to find a value within the segment associated with the ERROR.

21. The method of claim 20 wherein said feed rate segment value is calculated according to the formula:

2.sup.(INT(ERROR/N))

where N is a positive whole number.

22. The method of claim 21 wherein the feed rate interpolative value is calculated according to the formula:

##EQU3##

23. The method of claim 17 wherein the current feed rate is maintained unless the error difference between the actual machine power consumption and the desired adaptive power level exceeds a predetermined value thereby defining a nonreactive window.

24. The method of claim 23 wherein said predetermined value is a function of the selected adaptive power level.

25. The method of claim 24 wherein said nonreactive window is defined by the steps of:

reading the selected adaptive power level;

generating a programmed percentage of the adaptive power level;

subtracting the generated percentage from a maximum possible value for the window to arrive at a stabilization factor; and

thereafter, adding the stabilization factor to the error whereby the nonreactive window is adjusted.

26. The method of claim 17 further comprising:

storing a response factor value in a memory by selecting appropriate operator selectable commands; and

altering the feed rate change value according to the response factor stored in the memory.

27. The method of claim 26 wherein the feed rate change value is divided by a number which is a function of the response factor value when the response of the feed rate is desired to be decreased and multiplied by a second number which is a function of the response factor value when the feed rate is desired to be increased to thereby provide an adjusted feed rate change level.

28. The method of claim 16 which further comprises:

comparing the adjusted feed rate level with a preselected maximum feed rate; and

driving said machine at said preselected maximum feed rate if the adjusted feed rate level exceeds the maximum feed rate level.

29. The method of claim 16 which further comprises:

comparing the adjusted feed rate level with a preselected minimum feed rate level; and

driving said machine at said minimum feed rate level if the adjusted feed rate level is below the minimum feed rate level.

30. In a controller for a machine having a tool for machining a workpiece, said controller having at least one dedicated output line coupled to a switch for altering the machining operation upon occurrence of an alarm signal, the improvement comprising:

means responsive to both external manual and internal machine-generated requests to force the output line to a reset condition;

alarm means for generating an alarm signal when a machine parameter exceeds a predetermined limit; and

individually programmable means operative in a first programmed condition to place the output line in a switch activating state only for so long as the alarm signal persists, and operative in a second programmed condition to place the output line in the switch activating state upon occurrence of the alarm signal and until reset by the means to force, whereby an operator may selectively choose, via the individually programmable means, a latching or nonlatching switch activating state of said output line to control the machine operation.

31. The improvement of claim 30 which further comprises:

timer means for delaying the generation of said alarm signal until a preselected time period has elapsed in which the machine parameter has continuously exceeded the limit, and means for reinitializing the timer means whenever the limit is not exceeded.

32. The improvement of claim 31 which further comprises:

manually actuable means for selectively altering said time period.

33. In an adaptive process controller for a machine having a tool for machining a workpiece, said controller having means for continuously monitoring a machine parameter and adjusting machine operation so that said parameter is maintained at a preselected value, wherein the improvement comprises:

comparison means for providing a signal indicative of the error difference between the actual machine parameter and the preselected machine parameter; and

adjustment means for changing the machine feed rate as an exponential function of the error between the actual and preselected parameters wherein said machine is provided with stable, yet fast response.

34. The improvement of claim 33 wherein said adjustment means further comprises:

means for providing a digital word as an output, the contents of said digital word representing the new adjusted feed rate;

a digital to analog converter for providing an analog signal proportional to said contents of the digital word; and

means for coupling the output of said converter to a machine device for adjusting the actual machine feed rate.

35. The improvement of claim 33 wherein said exponential function generates a feed rate change value according to the formula:

FEED RATE CHANGE=2.sup.(ERROR)

where ERROR is the difference between the actual machine parameter and the preselected value of the machine parameter.

36. The improvement of claim 35 wherein the feed rate change value is generated by a 2 step digital approximation which includes the summation of a feed rate segment value associated with a beginning point in a segment of values and a feed rate interpolative value derived from a linear interpolation to find a value within the segment associated with the ERROR.

37. The improvement of claim 36 wherein said feed rate segment value is calculated according to the formula:

2.sup.(INT(ERROR/N)

where N is a positive whole number.

38. The improvement of claim 37 wherein the feed rate interpolative value is calculated according to the formula:

##EQU4##

39. In a machine controller for adaptively controlling the relative feed rate of the machine as a function of the error between a preselected value of a parameter and the actual parameter generated by the machine, the improvement comprising:

feed rate change means for generating a feed rate change value as a function of the error;

means defining a nonreactive window for disabling said feed rate change means when the error is below a preselected value; and

means for adjusting the nonreactive window to adapt the controller to different machining applications thereby insuring stability.

40. The improvement of claim 39 wherein the window is adjusted automatically by the controller as a function of the preselected value of the machine parameter.

41. The improvement of claim 40 wherein the machine parameter is the power consumption of the machine.

42. In a machine controller for adaptively controlling the relative feed rate of the machine as a function of error between a preselected value of a machine parameter and the actual value of the parameter generated by the machine, the improvement comprising:

feed rate change means for generating a feed rate change value as a function of error;

individually programmable means for selecting a response factor for affecting the controller response to the error;

adjustment means for adjusting the feed rate change value as a function of the response factor; and

means for altering the machine feed rate according to the value of the adjusted feed rate change value.

43. The improvement of claim 42 wherein said adjustment means further comprises:

means for multiplying the feed rate change value with a number which is a function of the response factor when the response is desired to be increased; and

means for dividing the feed rate change value with a number which is a function of the response factor when the response is desired to be decreased.

44. In a machine controller for controlling the relative feed rate of a machine having a motor for effecting the feed rate between a workpiece and a tool, the improvement comprising:

means for generating a digital output signal whose contents is a function of the desired feed rate;

means for sensing the maximum and minimum operating voltage levels of the motor;

buffer means having a plurality of inputs for receiving said digital signal, and a plurality of outputs, operative to provide signals on its outputs at voltage levels which are a function of the contents of the digital signal and the operating voltage levels of the motor;

wherein the output signals from the buffer are automatically referenced to the operating voltage levels of the motor so that they may be utilized to control the motor at the desired feed rate.

45. The improvement of claim 44 wherein said sensing means are coupled to reference inputs in said buffer means to determine the output voltage levels therefor.

46. The improvement of claim 45 wherein said sensing means are tapped on either side of a feed rate override potentiometer biased at the maximum voltage rating for the motor.

47. The improvement of claim 46 which further comprises:

digital to analog converter means coupled to the outputs of the buffer means, operative to provide an analog output signal to the feed rate override potentiometer as a function of the buffer output signals.

48. The improvement of claim 47 wherein said digital signal includes a plurality of bits at a logical high or low voltage level;

and wherein the buffer means assigns each bit at a logical high level to the maximum operating voltage level of the motor and each bit at a logical low level to the minimum operating voltage of the motor.

49. In a controller for an automated machine having the capability of performing a plurality of different machining operations, said controller having at least one dedicated output line coupled to the machine capable of altering the machining operation depending on the state of the output line, the improvement comprising:

manually selectable means for selecting section parameters associated with each machining operation, said section parameters including (a) a first limit value defining a first extreme level of machine power consumption;

(b) a second limit value defining a second extreme level of machine power consumption;

(c) a first timer value defining a first delay time period associated with said first limit value;

(d) a second timer value defining a second delay time period associated with said second limit value; and

(e) a status control selection for latching or nonlatching the state of the controller dedicated output line when overlimit conditions are detected;

manually selectable means for assigning each section with an identification tag;

memory means for storing a plurality of different sections along with their respective identification tags in a memory;

means in the machine for generating the appropriate section identification tag for each different machining operation such that the controller will utilize the identified section parameters for monitoring the particular machining operation to be performed;

means for monitoring the power consumed by the machine;

comparison means for comparing the machine power consumption with said first and second limit values, operative to change the state of the controller dedicated output line if either of said limit values have been continuously exceeded for their respective delay time periods; and

means for maintaining the changed state of the dedicated controller output line regardless of subsequent sensed levels of machine power consumption if the status control selection indicates that the output line is to be latched, and otherwise returning the state of the output line to its original state when machine power consumption is again below said first and second limit values if the status control selection indicates a desired nonlatched condition.

50. The improvement of claim 49 which further comprises two controller dedicated output lines each associated with said first and second limit values, respectfully.

51. The improvement of claim 49 wherein said controller further comprises, in addition to said section limit values, manually selectable means for defining a machine operational power window having selected upper and lower limit values;

a third controller output line coupled to the machine, operative to alter the machining operation if the machine power consumption violates said power window limits even though the currently utilized section first and second limit values may not have been exceeded.

52. The improvement of claim 51 which further comprises a manually selectable third time delay period associated with the machine operational power window, operative to delay the machine alteration via the third output line until the machine power consumption has continuously violated the operational power window for the third time delay period.

53. The improvement of claim 51 which further comprises manually selectable means for selectively disabling the lower limit value for a particular machining operation.

54. The improvement of claim 51 which further comprises:

a manually selectable surge delay timer stored in the memory means, operative to disable said comparison means until the selected surge time delay has elasped after machine start up.

55. The improvement of claim 54 which further comprises:

means for sensing power initially applied to the machine, operative to begin the timing of said surge delay timer.

56. The improvement of claim 49 wherein the machine is a numerically controlled machine having a BCD command bus coupled to machine components for control thereof, said machine providing said section identification tag to said controller over said BCD bus prior to initiating a particular machining operation so that the controller may utilize the appropriate section parameters for monitoring the particular machining operation.

57. The improvement of claim 56 wherein said controller further includes an adaptive control means for continuously adjusting machine feed rates to maintain machine power consumption at a manually selectable adaptive power level.

58. The improvement of claim 57 wherein said machine further comprises means for selecting adaptive control for a particular machining operation by placing a particular code on said BCD bus prior to beginning the machining operation.