METHOD AND APPARATUS FOR DIGITAL MEASURMENT AND CONTROL OF A MATERIAL BLENDING OPERATION

• US 3,590,227 A
• Filed: 05/31/1968
• Issued: 06/29/1971
• Est. Priority Date: 01/30/1968
• Status: Expired due to Term

• Current Assignee: The Dow Chemical Company (Dow, Inc.)
• Original Assignee: Kenneth E. Graves, Lawrence C. Porter
• Inventors: Porter, Lawrence C., Graves, Kenneth E.
• Application Number:
  US04/733,712
• Time in Patent Office: 1,124 Days
• US Class Current: 700/74
• CPC Class Codes: G05B 21/02 electric
• CPC Class Codes: G05D 11/131 by measuring the values related to the quantity of the individual components G05D11/139 takes precedence
• CPC Class Codes: G05D 11/132 by controlling the flow of the individual components G05D11/133 takes precedence
• CPC Class Codes: G05D 11/135 by sensing at least one property of the mixture G05D11/139 takes precedence
• CPC Class Codes: G05D 7/0676 by action on flow sources G05D7/0688, G05D7/0694 take precedence

Abstract

This invention includes digital control methods and apparatus for measuring a plurality of different operating parameters of a system or process, and for adjusting each of these parameters according to a preselected formulation. A scanner circuit may be employed to sequentially sample each of a plurality of measurement frequencies, and a function of each sample may be compared with a predetermined value to derive a suitable correction.

Claims

1. Controller apparatus for maintaining a plurality of potentially unstable parameters according to a preselected functional relationship comprising indicating means for generally indicating the magnitude of each of said parameters, frequency means for deriving an input frequency each functionally related to a different one of said functionally indicated magnitudes, preset means for establishing a plurality of preset functions each representative of a preselected magnitude of a different one of said parameters according to said preselected relationship, comparison means for deriving the functional difference between correspOnding ones of said indicated and preset magnitudes, and adjustment means for deriving from said functional difference an output composed of digital units functionally related in terms to corresponding units of the corresponding parameter.

2. The controller apparatus described in claim 1, wherein said output from said adjustment means is composed of digital units functionally related in number to said derived functional difference.

3. The controller apparatus described in claim 2, wherein each of said input frequencies is representative in terms of rate units of preselected magnitude of the corresponding ones of said parameters, and wherein said output from said adjustment means is composed of digital units functionally related in number to the difference between said corresponding ones of said indicated and preset magnitudes as expressed in terms of said rate units.

4. The controller apparatus described in claim 3, wherein said input frequencies are generally representative in terms of units of mass transfer rate, and wherein said output from said adjustment means is composed of digital units functionally related in number to the difference in number of said mass transfer rate units between said indicated and preset magnitudes.

5. The controller apparatus described in claim 4, wherein each of said digital units of said output is functionally representative of one of said mass transfer rate units.

6. The controller apparatus described in claim 5, wherein said adjustment means includes a multiplier for multiplying a determined number of pulses by a function of one of said input frequencies.

7. The controller apparatus described in claim 6, wherein said multiplier comprises timing means for defining a discrete time interval, sampling means responsive to one of said input frequencies for determining the number of pulses occurring in said input frequency during said time interval, and multiplying means deriving the product of said number of input frequency pulses and said determined number of pulses.

8. The controller apparatus described in claim 7, wherein said product corresponds in number of pulses to the number of said mass transfer rate in said difference between said indicated and preset magnitudes.

9. The controller apparatus described in claim 8, wherein said indicating and frequency means comprise frequency conversion means including first generating means for generating a first input frequency generally indicating the magnitude of each of said parameters, timing means for establishing a time dependent signal functionally related to said first input frequency, control means generating a control signal functionally related to a preselected time interval, and second generating means for transmitting to said comparison means a second input frequency functionally related to the mass transfer rate of the corresponding one of said parameters.

10. The frequency conversion means described in claim 9, wherein said second input frequency has a period functionally corresponding to said preselected time interval.

11. The controller apparatus described in claim 10, wherein said comparison means includes scanning means for receiving and sorting the pulses in each of said second input frequencies functionally relating in terms of mass transfer units to one of said parameters.

12. The scanning means described in claim 11, comprising a plurality of input channels each connected to receive and hold the pulses in one of said second input frequencies independently of the occurrence of the pulses in the other of said input frequencies, and sampling means for selectively taking said held pulses from said channels.

13. The scanning means described in claim 12, wherein said sampling means takes said held pulses from said channels in a time dependent manner.

14. The scanning means described in claim 13, wherein said sampling means sequentially selects said channels and takes said held Pulses therefrom in a time dependent manner.

15. The scanning means described in claim 14, wherein each of said channels comprises a first holding for receiving and holding pulses in one of said second input frequencies, a second holding register for receiving and holding said pulses held by said holding register, and an output register for receiving and transmitting said pulses held by said second holding register in a time dependent manner.

16. The comparison means described in claim 15, further including a step signal generator for generating a step signal to select pulses transmitted by a preselected one of said output registers in said scanner.

17. The comparison means described in claim 16, wherein said step signal selects pulses transmitted by both said preselected output register and at least one of said other output registers.

18. The comparison means described in claim 17, further comprising comparing means for comparing a function of said selected pulses with respect to a corresponding one of said preset functions.

19. The comparison means described in claim 18, wherein said comparing means compares a function of said pulses transmitted by all of said output registers during a preselected time interval with respect to a preselected preset function.

20. The controller apparatus described in claim 19, wherein said product from said multiplying means corresponds in number of pulses to the number of mass transfer rate units in the difference between said preselected preset function and the mass transfer rate functionally represented by the frequency of the pulses received by a preselected first holding register.

21. A method of maintaining a plurality of potentially unstable parameters according to a preselected functional relationship, comprising generating a plurality of electrical pulse trains each generally representative of the magnitude of one of said parameters, generating a plurality of input electrical pulse trains each functionally related to one of said indicated magnitudes, providing a plurality of preset electrical functions each representative of a preselected magnitude of a different one of said parameters according to said preselected relationship, generating the functional difference between corresponding ones of said input electrical pulse trains and preset electrical functions, and generating from said functional difference an output electrical signal composed of digital units functionally related in terms to corresponding units of the corresponding parameter.

22. The method described in claim 21, wherein each of said input electrical pulse trains is representative in terms of rate units of preselected magnitude of the corresponding ones of said parameters, and wherein said output electrical signal derived from said functional difference is composed of digital units functionally related in number to the difference between corresponding ones of said input electrical pulse trains and preset electrical functions as expressed in terms of said rate units.

23. The method described in claim 22, wherein said method further includes the step of multiplying a determined number of said units by a function of one of said input electrical pulse trains.

24. The method described in claim 21, wherein said digital units correspond to units of mass transfer.

25. The method described in claim 21, and further including, after generating a plurality of electrical pulse trains, the step of receiving and sorting the pulses in each of said input electrical pulse trains.

26. The method described in claim 25, and further comprising the step of receiving said pulses in each of said input electrical pulse trains independently of the occurrence of the pulses in the other of said input electrical pulse trains.

27. A controller for a system having a plurality of input parameters, comprising input means for receiving pulses representative of units of said parameters of a syStem and for forming said received pulses into a plurality of pulse trains each representative in frequency to the said units for a selected one of said parameters, preset means for establishing a plurality of predetermined ratio values between a base parameter and the other parameters, and means for comparing each of said predetermined ratio values with the ratio of different selected ones of said pulse trains to a base parameter pulse train during a defined time interval and for deriving control pulses functionally related in number to any difference therebetween.

28. The apparatus of claim 27 wherein said defined time interval is defined by a preselected number of pulses of said base parameter and further including means for multiplying said control pulses by a function of said predetermined number of pulses.

29. The apparatus of claim 28 wherein said preset means also establishes a predetermined cumulative total of the pulses of said pulse trains for a preselected time interval and said comparing means compares the total number of pulses of said pulse trains from said received pulses to said predetermined total during a preselected time interval for deriving control pulses functionally related in number to any difference therebetween.

30. The apparatus of claim 29 and further including means for cyclically interrogating said input receiving means and said preset means during said defined time interval.

31. The apparatus of claim 27 and further including means for cyclically operating said input means, said preset means and said comparing means during said defined time interval.

32. A controller for a system having a plurality of dependent parameters which are independently subject to change comprising means for receiving input pulses representative of units of a measured parameter and for forming said received pulses into a plurality of pulse trains each representative in frequency to the units of the measured parameter, preset means for establishing predetermined desired values for each parameter, means for comparing each of said pulse trains to a corresponding value for a parameter over a defined period of time and for deriving error pulses functionally related in number to any difference between the number of pulses in a pulse train as related to an established predetermined value, and means responsive to said error pulses for selectively obtaining correction factor control pulses which are functionally related to the frequency of a measured parameter.

33. The apparatus of claim 32 and further including means for cyclically sampling said input receiving means and said preset means during said defined period of time.

34. The apparatus of claim 33 and further including means for totalizing said received pulses during a preselected time interval.

35. A controller for a system having a plurality of operating parameters, comprising means for receiving a plurality of pulse trains each representative of an actual measured magnitude of a parameter, means for establishing the ratios of selected ones of said pulse trains to at least one other preselected pulse train, means for establishing a functional correspondence to the ratio of a preselected magnitude for each of the parameters represented by said selected pulse trains to a preselected magnitude for the parameter represented by said one other preselected pulse train, means for comparing each established ratio to the functional correspondence related thereto during a determined time period, and means for deriving a train of control pulses functionally corresponding in number to the difference between the comparison of said established ratio and said related functional correspondence and the determined time period.

36. A controller for a system having a plurality of mass transfer parameters comprising means for generating a first frequency signal for each parameter which is indicative of the magnitude of the parameter;

means responsivE to said first frequency signals for generating pulse signals functionally related to the mass transfer rates of corresponding parameters, one of said pulse signals being representative of a base parameter;

means for determining the number of pulses in each pulse signal for a predetermined number of pulses representative of the measured base parameter relative to a preset number of pulses desired for a parameter relative to said predetermined number of pulses for said base parameter and for providing a pulse count output if there is a difference; and

means responsive to said pulse count output for developing correction pulses functionally related in number to the time period defined by said predetermined number of pulses for said base parameter.

37. A controller for receiving measurement signals of throughput parameters which signals have similar characteristics but represent different values of throughput and providing output control signals calibrated in terms of the respective throughput values comprising:

means for receiving pulse trains respectively representative of a throughput flow parameter where one of said pulse trains is representative of a base throughput flow parameter;

means for establishing predetermined throughput parameters for each of said throughput parameters and for a predetermined sum of said throughput parameters;

means for comparing each of said sampled pulse trains for a throughput parameter and said one pulse train with a corresponding predetermined throughput parameter for a given period of said one pulse train representative of a base throughput parameter and for deriving apparent error pulses, and means responsive to said error pulses for supplying control pulses calibrated in terms of said given period of said one pulse train, said comparing means also comparing for an interval of time the sum of throughput values represented by said sampled pulse trains to said predetermined throughput sum, and means for supplying total control pulses if there is a difference therebetween.

38. A controller for receiving measurement signals of throughput parameters which signals have similar characteristics but represent different values of throughput and providing output control signals calibrated in terms of the respective throughput values comprising:

means for receiving pulse trains respectively representative of a throughput flow parameter where one of said pulse trains is representative of a base throughput flow parameter;

means for sequentially sampling said receiving means to derive pulse trains representative of each of the other throughput parameters;

means for establishing predetermined throughput parameters for said other throughput parameters;

means for sequentially comparing each of said sampled pulse trains for a throughput parameter and said one pulse train with a corresponding predetermined throughput parameter for a given period of said one pulse train representative of a base throughput parameter and for deriving apparent error pulses, and means responsive to said error pulses for supplying control pulses calibrated in terms of said given period of said one pulse train.

39. The apparatus of claim 38 and also including in said establishing means a predetermined total throughput value and means to compare the cumulative total of throughputs represented by said sampled pulse trains to said predetermined total throughput for supplying control pulses representative of any error in total throughput.

40. A controller for a system having a plurality of parameters having common measurable units which are functionally interrelated and wherein the parameter units can vary independently of each other comprising:

means for separately receiving pulses representative of units of a measured parameter and for storing such pulses;

means for separately receiving pulses representative of units of a measured base parameter;

means for sequentially interrogating said storing means to obtain the number of stored pulses for each parameter;

means for determining the number of pulses in each storing means for a predetermined number of pulses representative of the measured base parameter relative to a preset number of pulses desired relative to said predetermined number of pulses for said base parameter which determine a period of time and for providing a pulse count output if there is a difference; and

means responsive to said pulse count output for developing correction pulses functionally related in number to the determined period of time.

41. A controller for a system having a plurality of dependent parameters wherein it is desired to maintain a predetermined relationship between such parameters comprising:

means for receiving a plurality of input pulse trains in which the pulses of each train are representative of the magnitude of a parameter for each such input and wherein the pulses of one of said input pulse trains is representative of the magnitude of a base parameter and the pulses of at least one other of said input pulse trains represents a multiple of the actual magnitude of at least one other parameter, means for predetermining a relationship of pulses of each pulse train to a selected number of pulses of the pulse train for the base parameter, means for comparing the relationship of received pulses of each pulse train to the pulses of the pulse train for the base parameter to the predetermined relationship established by said predetermining means and for producing error output pulses, and means responsive to error output pulses produced by comparison of said one other input pulse train for producing correction output pulses functionally related to the time period for said selected number of pulses.

42. The apparatus of claim 41 and further including means coupled to said receiving means for providing said input pulse trains in which the pulses of each train are representative of the magnitude of a parameter and are related to pulses of other trains by a factor of 10.

43. The apparatus of claim 41 and further including means for totaling the magnitudes represented by said input pulse trains for a preselected time period;

means for predetermining a relationship of the magnitudes in relation to the total number of pulses for said preselected time period;

means for comparing the magnitudes in relation to said total pulses of said input pulse trains to the predetermined relationship and for producing total correction output pulses.

44. A controller for a system having a plurality of input parameters, comprising means for generating pulses for each parameter at a rate related to a magnitude function of each of said parameters, thereby forming pulse trains for each of said parameters, input means for receiving and storing said generated pulses for each pulse train, preset means for establishing a plurality of predetermined ratio values between a base input parameter and said other input parameters, and means for comparing each of said predetermined ratio values with the ratio of different selected ones of said pulse trains to a base parameter pulse train during a defined time interval and for deriving control pulses functionally related in number to any difference therebetween.

45. The controller of claim 44 including means for cyclically interrogating said storing means and said comparing means.

46. The controller of claim 44 and including means for multiplying said control pulses by a function of said defined time interval.

47. A controller for a system having a plurality of parameters to be controlled comprising:

means for generating a first frequency signal for each parameter which is indicative of the magnitude of the parameter;

means responsive to said first frequency signals for generating pulse signals functionally related to the magnitude of the corresponding parameters, one of said pulse signals being representative of a base parameter;

meAns for determining the number of pulses in each pulse signal for a predetermined number of pulses representative of the measured base parameter relative to a preset number of pulses desired relative to said predetermined number of pulses for said base parameter and for providing a pulse count if there is a difference;

means for cyclically operating said pulse signal means and determining means for obtaining any such pulse counts for different parameters;

means responsive to at least one of said pulse counts for developing correction pulses functionally related in number to the time period defined by said predetermined number of pulses for said base parameter;

means for summing the pulse signals in relation to their magnitude; and

means for comparing said summed pulse signals to a predetermined magnitude value and deriving output pulses if there is a difference.

48. A method for maintaining a plurality of input parameters in accord with a preselected functional relationship, comprising:

generating a plurality of electrical pulse signals each generally representative of a value of one of said parameters;

generating a plurality of electrical input pulse trains each having a value functionally related to the value of said one of said parameters;

providing a plurality of preset functions each representative of a preselected value for each of said parameters according to a preselected relationship for a value of a selected base parameter;

generating electrical error pulse signals representative of the functional difference between corresponding ones of said input pulse trains and the pulse train for said selected base parameter, and corresponding ones of said preset functions, and generating from said error pulse signals electrical pulses functionally related in digital terms to the corresponding parameter and said base parameter.

49. A method of controlling measured input parameters which are dependent upon a preselected functional relationship comprising:

generating pulse trains for each of said parameters which indicate by number of pulses the magnitude of the parameter;

electrically comparing, for a predetermined number of a base parameter pulses, the number of pulses for a given parameter to a predetermined number of pulses for such parameter and deriving error output pulses for any difference therebetween, and generating, for any error output pulses, control pulses related in number to the time period for said predetermined number of base parameter pulses.

50. A method of controlling a plurality of measured parameters where it is desired to maintain a predetermined relationship between such parameters comprising:

generating a plurality of input pulse trains in which the pulses of each train are representative of the magnitude of a parameter for each such input;

generating at least one other input pulse train in which the pulses of the input train are representative of the magnitude of a base parameter;

electrically comparing, during a period of time as defined by a determined number of base parameter pulses, the relationship of one pulse train to said base parameter input pulse train to a predetermined desired relationship, and generating error pulses indicative of any difference therebetween.

51. The method of claim 48 and further including the step of sequentially sampling said input pulse trains relative to said preset functions during a time period defined by the value of said selected base parameter and multiplying said error pulse signals by a factor functionally related to the value of a parameter and said time period.

52. The method of claim 51 and further including the steps of totalizing the values of said input pulse trains and comparing said totalized values to a predetermined total value for a preselected time period and generating total control pulses if there is a difference therebetween.

53. The method according to claim 49 and further including the steps of electrically totaling the magnitude of the parameters by counting the pulse trains and comparing said total to a predetermined desired total and generating total control pulses if there is any difference therebetween.

54. A controller for a system having a plurality of input parameters comprising:

input means for receiving pulses representative of units of each of said parameters of a system in pulse trains, each pulse train being representative of one of said parameters, means for predetermining a total of said units as a function of the total number of pulses during a preselected time period, means for comparing the total count of said pulses in terms of said units for said preselected time period to said predetermined total and for deriving total error pulses, and means for selecting one of said pulse trains and for determining the ratio of the pulse count of said one pulse train relative to a predetermined total count of said pulses in terms of said units and for multiplying said error pulses by said ratio to provide correction pulses for the parameter corresponding to said one pulse train.

55. The apparatus of claim 54 and further including timing means for establishing said preselected time period, and means responsive to said timing means and said comparing means for determining the direction of any error from said total count.