Process flow computer control system

• US 4,328,549 A
• Filed: 01/11/1980
• Issued: 05/04/1982
• Est. Priority Date: 01/11/1980
• Status: Expired due to Term

• Current Assignee: Arch Chemicals Incorporated (Lonza Group AG)
• Original Assignee: OLIN Corporation
• Inventors: Avery, Cecil T.
• Primary Examiner(s): Ruggiero, Joseph F.
• Application Number:
  US06/111,457
• Time in Patent Office: 844 Days
• Field of Search: 364/476, 364/468, 364/469, 364/118, 364/119, 364/120, 364/510, 364/473, 364/551, 364/552, 364/115, 364/200 MS File, 364/900 MS File, 264/321, 264/41, 264/46.4, 264/45.8, 264/40.1, 264/40.7, 264/40.4, 425/145, 425/135, 425/136, 425/162, 425/169, 521/918
• US Class Current: 700/122
• CPC Class Codes: B29C 44/60 Measuring, controlling or regulating
• CPC Class Codes: G05B 15/02 electric
• CPC Class Codes: G05D 7/00 Control of flow level control G05D9/00; control of flow ratio G05D11/00
• CPC Class Codes: Y10S 521/918 Physical aftertreatment of a cellular product

Abstract

An improved method for automatically controlling the rate of mass flow in a system having a mass mover powered by a power supply which is attenuated by a control device for transferring mass through a conduit, wherein a signal proportional to said mass flow is transmitted to an automatic control unit, characterized by the improvement among others, whereby the improved automatic control unit is provided with a process control mode in which new operating conditions are entered into the program, and the automatic control unit determines the correct mode of control for the new process conditions.

Claims

1. An improved method for automatically controlling the rate of mass flow in a system having a mass mover powered by a power supply which is attenuated by a control device for transferring mass through a conduit, wherein a signal proportional to said mass flow is transmitted to an automatic control unit, characterized by the improvement which comprises, in combination;

(a) entering in said automatic control unit a standard signal, S_a, representative of a desired rate of mass flow in said conduit,

(b) entering in said automatic control unit a rate of mass flow deviation range, K₁ -K₂,

(c) entering in said automatic control unit an initial operating voltage, V, and transferring a signal proportional to said V to said control device to operate said mass mover while in automatic control mode to attenuate said power supply to said mass mover, and to produce a rate of mass flow in said conduit at said initial operating voltage, V,

(d) obtaining a first signal, S₁, proportional to the actual rate of mass flow in said conduit, and conveying said first signal, S₁, to said automatic control unit,

(e) comparing said S_a with said S₁ in said automatic control unit and calculating a difference, D, between said S_a and said S₁, and comparing said difference, D, with said mass flow deviation range, K₁ -K₂,

(f) when said difference, D, exceeds said mass flow deviation range, K₁ -K₂, switching said automatic control unit to a mode of fixed value, and thereafter transmitting a signal proportional to said initial operating voltage, V, to said control device to operate said mass mover at a fixed signal value.

2. The method of claim 1, characterized by the further improved step in which,

(g) when said difference, D, is found to be a number within said mass flow deviation range, K₁ -K₂, while said automatic control unit is in automatic control mode, calculating a voltage increment signal, Δ

V, proportional to the value of said difference, D, adding said Δ

V to said V to obtain a resulting voltage, V_r, and transmitting a signal proportional to said V_r to said control unit as a new operating voltage, whereby said attenuated power supply to said mass mover is adjusted to provide a rate of mass flow closer to said S₁.

3. The method of claim 2, characterized by the further improved step in which,

(h) while said automatic control unit is in automatic control mode, after a predetermined time interval, X, obtaining a second signal, S₂, which is proportional to the actual rate of mass flow in said conduit, conveying said signal, S₂, to said automatic control unit, repeating step (e) upon receipt of said second signal, S₂, by said automatic control unit, and thereafter repeating step (f) or step (g).

10. The method of claim 3 or 8 wherein said automatic control unit receives signals from frequency counter cards, and the system is switched to mode of fixed value when no signal is received from said frequency counter cards during a predetermined period of time X.

12. The method of claim 10 wherein said control device is a speed control device.

14. The process of claim 12 wherein said computer is comprised of an arithmetic and control unit, a read only memory, a read-write memory, and a code producing device.

16. The method of claim 14 which further comprises

(a) supplying a separate electrical power supply to said microprocessor and said interface unit, and

(b) transmitting a fixed voltage from said interface unit to said speed control device upon loss of said electric power supply to said microprocessor.

18. The method of claim 16 wherein said mass is a compound capable of forming a curable polyurethane foam composition selected from the group consisting of polyol, blowing agent, chain extending agent, water, catalyst, lubricant, organic isocyanate, fluorinated hydrocarbon, and mixtures thereof.

20. The method of claim 18 wherein said conduit is a pipe.

22. The method of claim 20 wherein said actual process variable measurement is pressure.

32. The method of claim 16 wherein said mass is a compound capable of forming a curable reaction injection molding composition or semi-liquid injection molding composition selected from the group consisting of polyol, blowing agent, chain extending agent, water, catalyst, lubricant, and organic isocyanate.

33. The method of claims 3 or 8, characterized by the improved step comprising incrementally increasing the controller generated interface voltage during a preselected time interval in the range from about 0.05 to about 10,000 seconds.

34. The method of claim 32 wherein said preselected time is in the range from about 10 to about 120 seconds.

35. The method of claim 32 wherein said controller generated interface voltage is increased linearly with time.

36. The method of claims 3 or 8 wherein in said control mode of fixed value, the voltage signal supplied to said mass mover is maintained at the present value of voltage supplied to said control device to operate said mass mover at the time said automatic control unit was operating said mass mover and was switched to said control mode of fixed value.

37. The method of claims 3 or 8 wherein a second mass mover is employed, and wherein said operating voltage signal is attenuated to only said second mass mover by said control device.

38. The method of claim 36 wherein said second mass mover is a flow control device.

39. The method of claims 3 or 8 wherein in said mode of fixed value, the voltage signal supplied to said control device to operate said mass mover is nonzero.

40. The method of claims 1 or 4, wherein said automatic control unit includes an arithmetic and control unit and there is a code producing unit electrically connected to said arithmetic and control unit and there is a memory unit electrically connected to and communicative with said automatic control unit, said code producing unit having a keyboard with singular keys, thereon capable of being depressed to produce a unique code, said arithmetic and control unit being capable of receiving and storing said unique code in said memory unit, said method characterized by the further step of entering sequentially allowable keyboard entries comprised of operative command entries and data entries from said code producing unit to said arithmetic and control unit, said step comprising:

(a) depressing a select key on said keyboard to produce a unique code corresponding to the depressed key,

(b) transmitting said unique code to said memory unit,

(c) maintaining in said memory unit a first assemblage of acceptable code values from among all values of said code, and

(d) comparing said unique code with said acceptable code values and determining whether said unique code is acceptable.

41. The method of claim 39, characterized by the further steps of:

(e) maintaining in said memory unit

(1) a second assemblage of acceptable codes corresponding to data on said keyboard, and

(2) a third assemblage of acceptable codes of corresponding operative command entries on said keyboard,

(f) determining if said unique code is acceptable in said second assemblage, and if so, entering said unique code into said memory unit as a numerical entry for further utilization, and

(g) if said unique code is not acceptable to said second assemblage and is acceptable to said third assemblage, then entering said unique code into said memory unit as a command entry for further utilization.

42. The process of claim 40 wherein said acceptable unique codes are directed by alterable directives in said memory unit and further utilized in said memory unit when it is sequentially allowable.

43. The process of claim 41 wherein said alterable directives are flags.

44. The method of claim 42 wherein said memory unit is read-write memory.

45. The method of claim 42 wherein said unique code is ASCII code.

46. The method of claim 42 wherein said code reading unit is a teletypewriter.

47. The method of claim 3 or 8, characterized by the further improvement of employing the improved method of claim 42.

48. The method of claims 39, 40, or 41 characterized by the further improved step which comprises:

(a) depressing a select singular key on said code producing unit thereby producing a single unit of code corresponding to the depressed key,

(b) transmitting said singular unit of code to said memory unit, and

(c) employing said singular unit of said binary code to represent an operative command in the program logic.

49. The method of claim 47 wherein said code is binary code.

50. The method of claim 48 wherein said operative command comprises supply interface voltage to pump.

4. An improved method for automatically controlling the rate of mass flow in a system having a mass mover powered by a power supply which is attenuated by a control device for transferring mass through a conduit, wherein a signal proportional to said mass flow is transmitted to an automatic control unit, characterized by the improvement which comprises, in combination:

(a) entering in said automatic control unit a standard signal, S_a, representative of a desired rate of mass flow in said conduit,

(b) entering in said automatic control unit a rate of mass flow deviation range, K₁ -K₂,

(c) entering in said automatic control unit an initial operating voltage, V, and transferring a signal proportional to said V to said control device to operate said mass mover under automatic control mode, to attenuate said power supply to said mass mover, and to produce a rate of mass flow in said conduit at said initial operating voltage, V,

(d) entering in said automatic control unit a standard signal T₁ representative of another process variable in said conduit, S, and a standard deviation range, G₁ -G₂, for said T₁,

(e) obtaining a first signal, S₁, proportional to the actual rate of mass flow in said conduit, obtaining a signal corresponding to T₂ at a point in said conduit other than where said S₁ is obtained, and conveying said first signal, S₁, and said T₂ to said automatic control unit,

(f) comparing said S_a with said S₁ in said automatic control unit, and calculating a difference, D, between said S_a and said S₁, and comparing said difference, D, with said mass flow deviation range, K₁ -K₂,

(g) when said difference, D, exceeds said mass flow deviation range, K₁ -K₂, comparing T₂ with T₁ to obtain a difference G, comparing G with deviation range G₁ -G₂, and thereafter determining whether said mass mover is controlled by a mode selected from the group consisting of an automatic control mode and a mode of fixed value.

5. The method of claim 4 wherein said comparison shows that G is within said range, G₁ -G₂, switching said automatic control unit to a mode of fixed value, and thereafter transmitting a signal proportional to said initial operating voltage, V, to said control device to operate said mass mover at a fixed position.

6. The method of claim 4 wherein, when said comparison shows that said G is outside said range, G₁ -G₂, while said automatic control unit is controlled by an automatic control mode, calculating a voltage increment signal, Δ

V, proportional to the value of said difference, D, adding Δ

V to said V to obtain a resulting voltage, V_r, and transmitting a signal proportional to said V_r to said control unit as a new operating voltage, whereby said attenuated power supply to said mass mover is adjusted to provide a rate of mass flow closer to said S₁.

7. The method of claim 6, characterized by the further improvement, after completion of step (g) or step (h), if said automatic control unit is in said automatic control mode, the steps comprising:

9. The method of claim 7, characterized by the further improvement,

(o) in the event said D₃ exceeds said mass flow deviation range, K₁ -K₂, obtaining after a predetermined time interval, t_o +X, a fourth electrical signal, S₄, proportional to actual mass flow in said conduit,

(p) comparing said fourth electrical signal, S₄, with said second standard signal, S_b, to obtain a fourth difference, D₄,

(q) comparing said fourth difference, D₄, with said mass flow deviation range, K₁ -K₂,

(r) in the event D₄ is outside said mass flow deviation range, K₁ -K₂, repeating steps (o), (p), and (q) for R times in increments of X seconds, where R a number is in the range from about 1 to about 100, and where X is in the range from about 1 to about 100 seconds,

(s) in the event said fourth difference, D₄, is within said mass flow deviation range, K₁ -K₂, switching said automatic control unit to a mode of fixed value, and repeating steps (e) and (f),

(t) in the event said difference, D₄, during the time up to about t_o +R X seconds does not fall within said mass flow deviation range, K₁ -K₂, then switching said automatic control unit to said mode of fixed value and transmitting a signal proportional to said V_r to said speed control device, and

(u) removing the value of said S_b from said automatic control unit.

11. The method of claim 9 wherein said power supply is an electric power supply.

13. The method of claim 11 wherein said automatic control unit is selected from a group consisting of a computer, minicomputer, microcomputer, and microprocessor.

15. The method of claim 13 wherein said code producing device is a teletypewriter, and said automatic control unit is a microprocessor.

17. The method of claim 15 which further comprises

(a) transmitting a fixed voltage from said interface unit to said speed control device upon receipt by said interface unit of an electrical signal from said microprocessor representative of a mechanical failure of said microprocessor.

19. The method of claim 17 wherein said mass mover is a pump.

21. The method of claim 19 wherein said actual process variable measurement is temperature.

23. The method of claim 19 wherein said actual process variable measurement is mass flow.

25. The apparatus of claim 23 wherein said automatic control unit is comprised of a computer, an interface unit, and a code producing unit.

27. The apparatus of claim 25 wherein a separate power supply is provided for said microprocessor and for said interface unit.

29. The apparatus of claim 27 wherein said conduit is a pipe.

31. The apparatus of claim 29 wherein said control device is a speed control device.

8. (i) entering in said automatic control unit a second standard signal, S_b, representative of the next desired rate of mass flow through said conduit, switching said automatic control unit to a process change control mode, and beginning a real time measurement, t_o,

(j) calculating an adjusted operating voltage, V_a, according to the formula ##EQU3## (k) transmitting a signal corresponding to said V to said speed control device, whereby said attenuated main electric supply voltage to said mass mover is adjusted to provide a rate of mass flow closer to said S_b, and

(l) obtaining a third electrical signal, S₃, proportional to said rate of mass flow and comparing said third electrical signal, S₃, with said S_b, and obtaining a difference D₃,

(m) comparing said difference, D₃, with said deviation range, K₁ -K₂,

(n) switching said automatic control unit to said automatic control mode and repeating steps (e) and (f) when said difference is within said mass flow deviation range, K₁ -K₂.

24. In an apparatus for automatically controlling the rate of mass flow in a system having a mass mover powered by a power supply which is attenuated by a control device for transferring mass through a conduit, wherein a signal proportional to said mass flow is transmitted to an automatic control unit, characterized by the improvement which comprises in combination:

(a) an automatic control unit programmed with predetermined standard signals and signal ranges for mass flow,

(b) means for entering in said automatic control unit a standard signal, S_a, representative of a desired rate of mass flow in said conduit,

(c) means for entering in said automatic control unit a rate of mass flow deviation range, K₁ -K₂,

(d) means for enterining in said automatic control unit an initial operating voltage, V, and transferring a signal proportional to said V to said speed control device to operate said mass mover under automatic control mode, to attenuate said main electric power supply to said mass mover, and to produce a rate of mass flow in said conduit at said initial operating voltage, V,

(e) means for obtaining a first electrical signal, S₁, proportional to the actual rate of mass flow in said conduit, and another electrical signal TG₁ proportional to a measurable process variable and independent of said S₁, and conveying said TG₁ and said S₁ to said automatic control unit,

(f) means for comparing said S_a with said S₁ in said automatic control unit, and calculating a difference, D, between said S_a and said S₁, and comparing said difference, D, with said mass flow deviation range, K₁ -K₂, and

(g) when said difference, D, exceeds said mass flow deviation range, K₁ -K₂, means for switching said automatic control unit to a mode of fixed value, and thereafter transmitting a signal proportional to said initial operating voltage, V, to said speed control device to operate said mass mover at a fixed signal value.

26. The apparatus of claim 24 wherein said computer is a microprocessor, and said code producing unit is a teletypewriter.

28. The apparatus of claim 26 wherein said mass mover is a pump.

30. The apparatus of claim 28 wherein said power supply is electric.