Control system

• US 7,016,779 B2
• Filed: 01/31/2003
• Issued: 03/21/2006
• Est. Priority Date: 01/31/2002
• Status: Expired due to Fees

• Current Assignee: Cambridge Solutions Limited (DXC Technology Company)
• Original Assignee: Cambridge Solutions Limited (DXC Technology Company)
• Inventors: Bowyer, Robert Owen
• Primary Examiner(s): Vo, Hieu T.
• Application Number:
  US10/502,904
• Publication Number:
  US 20050131620A1
• Time in Patent Office: 1,145 Days
• Field of Search: 701/108, 701/109, 701/102, 701/115, 123/674, 123/680, 123/675, 602/74
• US Class Current: 701/108
• CPC Class Codes: F02D 2041/1412 using a predictive controller
• CPC Class Codes: F02D 2041/1433 using a model or simulation of the system
• CPC Class Codes: F02D 41/0007 for control of turbo-charged or super-charged engines control of the pumps per se F02B37/12
• CPC Class Codes: F02D 41/005 according to engine operating conditions
• CPC Class Codes: F02D 41/0072 Estimating, calculating or determining the EGR rate, amount or flow sensors in EGR systems F02M26/45
• CPC Class Codes: F02D 41/1401 characterised by the control or regulation method F02D41/1473, F02D41/1477 take precedence
• CPC Class Codes: F02D 41/1406 with use of a optimisation method, e.g. iteration
• CPC Class Codes: G05B 13/048 using a predictor
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

There is described a method for controlling a system, for example a Diesel engine, that is subject to transient changes of target outputs. The target outputs specify outputs required from the system. “Steady state” information is used to give optimum inputs for the system when the target outputs are substantially constant. A model of the system is used to predict the outputs of the system in response to candidate new values for the inputs of the system. The method combines the steady state information with the predicted response of the system to determine inputs to the system which will cause the system outputs to match the target outputs as closely as possible. For each candidate (in one embodiment), the method calculates the difference between the steady state inputs and a candidate, and the difference between the target outputs and the predicted outputs that would result from the adoption of that candidate, to determine an optimum candidate which is then used to update the inputs to the system.

Claims

1. An apparatus for controlling a system having a first number of system inputs and a second number of system outputs, by outputting, at intervals, signals for updating the system inputs, the apparatus comprising:

means for receiving one or more signals indicative of target values for the system outputs;

mapping means for using steady state information that relates the system outputs to the system inputs under steady state conditions, to determine a number, equal to the first number, of steady state values for the system inputs on the basis of the target output values;

means for receiving a number, equal to the second number, of signals indicative of the system outputs;

initial value means for producing at least one set of initial values, wherein each set consists of a number, equal to the first number, of values for use as a basis for determining a set of update values, wherein the set of update values consists of a number, equal to the first number, of values for updating the system inputs;

prediction means for using a model of the system to predict, for each set of initial values, a set of future values of the system outputs on the basis of past system input values, past system output values and a respective set of initial values;

first differencing means for determining differences between the steady state values and each set of initial values to give first difference information;

second differencing means for determining differences between the target values and each set of predicted future values of the system outputs to give second difference information;

combining means for combining the first difference information with the second difference information to give combined difference information;

determining means for determining the set of update values on the basis of the combined difference information and each set of initial values; and

output means for outputting signals, indicative of the set of update values, for updating the system inputs.

2. The apparatus according to claim 1, further comprising one or more sensors for producing signals indicative of the target values.

3. The apparatus according to claim 1, wherein the means for receiving signals indicative of target values comprises means for deducing the target values from the signals indicative of the target values.

4. The apparatus according to claim 1, wherein the mapping means comprises the steady state information.

5. The apparatus according to claim 1, wherein the mapping means comprises means for receiving the steady state information.

6. The apparatus according to claim 1, wherein the mapping means is operable to use a look-up table comprising the steady state information.

7. The apparatus according to claim 1, wherein the mapping means comprises means for receiving a first signal and wherein the mapping means is operable, in response to the first signal, to change the basis on which the mapping means determines steady state values.

8. The apparatus according to claim 7, wherein the mapping means is operable to change the basis by selecting, in response to the first signal, one of a plurality of sets of steady state information.

9. The apparatus according to claim 7, further comprising a sensor for producing the first signal.

10. The apparatus according to claim 1, further comprising a number, equal to the second number, of sensors for producing signals indicative of the system outputs.

11. The apparatus according to claim 1, wherein the prediction means is operable to use an auto regressive integrated moving average model to predict each set of future values.

12. The apparatus according to claim 1, wherein the prediction means comprises information specifying the type of model to be used.

13. The apparatus according to claim 12, wherein the prediction means comprises information specifying parameters of the model.

14. The apparatus according to claim 1, wherein the prediction means comprises means for receiving information specifying the type of model to be used.

15. The apparatus according to claim 14, wherein the prediction means comprises means for receiving a second signal and wherein the prediction means is operable to select the type of model to be used in response to the second signal.

16. The apparatus according to claim 15, wherein the second signal is indicative of a system output.

17. The apparatus according to claim 15, further comprising a sensor for producing the second signal.

18. The apparatus according to claim 1, wherein the prediction means comprises means for receiving information specifying parameters of the model.

19. The apparatus according to claim 1, wherein the prediction means comprises means for receiving a third signal and wherein the prediction means is operable, in response to the third signal, to alter a parameter of the model being used.

20. The apparatus according to claim 19, wherein the third signal is indicative of a system output.

21. The apparatus according to claim 19, further comprising a sensor for producing the third signal.

22. The apparatus according to claim 1, further comprising third differencing means for determining differences between the values of the most recently used set of update values and the values of each set of initial values to give third difference information, and

wherein the combining means is operable to combine the third difference information with the first difference information and the second difference information to give the combined difference information.

23. The apparatus according to claim 1, wherein the combining means comprises means for changing the relative significance in the combined difference information of the first difference information and the second difference information, in response to a fourth signal.

24. The apparatus according to claim 23, wherein the fourth signal is the rate of change of a signal indicative of a target value.

25. The apparatus according to claim 23, wherein the apparatus comprises a sensor for producing the fourth signal.

26. The apparatus according to claim 1, wherein the initial value means is operable to produce one set of initial values and to use the most recently used set of update values as the set of initial values.

27. The apparatus according to claim 1, wherein the initial value means is operable to produce a plurality of sets of initial values, the prediction means is operable to produce a plurality of respective sets of predicted future values, the first differencing means is operable to determine the first difference information by determining a respective first difference value for each of the sets of initial values, the second differencing means is operable to determine the second difference information by determining a respective second difference value for each of the sets of predicted future values so that for each of the first difference values there is a second difference value determined on the basis of the same set of initial values, the combining means is operable to combine each of the first difference values with its respective second difference value to give a plurality of combined difference values wherein each of the combined difference values is associated with a respective set of initial values, and the determining means is operable to select one or more sets of initial values on the basis of their associated combined difference values for use in determining the set of update values.

28. The apparatus according to claim 27, wherein the determining means is operable to select one of the sets of initial values and to use the selected set of initial values as the set of update values.

29. The apparatus according to claim 27, wherein the determining means is operable to select two or more of the sets of initial values and wherein the determining means comprises interpolation means operable to produce the set of update values by interpolating the two or more selected sets of initial values.

30. The apparatus according to claim 27, wherein the combining means is operable to combine the first difference values with their respective second difference values by addition.

31. The apparatus according to claim 27, wherein the initial value means is operable to produce at least one set of further initial values, wherein each set of further initial values consists of a number, equal to the first number, of values for use as a basis for determining a set of further update values for updating the system inputs at the beginning of an interval subsequent to the interval for which the system inputs are to be updated by the set of update values;

wherein each set of further initial values is associated with a respective set of initial values;

wherein, for each set of initial values, the prediction means is further operable to predict each set of future values of the system outputs on the basis of a respective set of further initial values as well as on the basis of past system input values, past system output values and a respective set of initial values; and

wherein the determining means is operable to consider the influence of each set of further initial values on the second difference information during the selection of one or more sets of initial values.

32. The apparatus according to claim 1, wherein the combination means comprises means for using matrix operations to combine the first difference information with the second difference information.

33. The apparatus according to claim 32, wherein the combining means and the determining means are operable to use the mixed weights least squares method to determine the set of update values by using information relating the response of the system outputs to a change of the system inputs.

34. The apparatus according to claim 33, wherein the combining means and the determining means are operable to determine a set of further update values, for updating the system inputs at the beginning of an interval subsequent to the interval for which the system inputs are to be updated by the set of update values, and wherein the combining means and the determining means are operable to determine the set of update values and the set of further update values on the basis of the information relating the response of the system outputs to a change of the system inputs.

35. The apparatus according to claim 1, further comprising an actuator for modifying a system input in response to a signal indicative of an update value.

36. The apparatus according to claim 1, wherein the apparatus is operable to output the signals for updating the system inputs at intervals of 60 milliseconds.

37. The apparatus according to claim 1, wherein the prediction means is operable to predict future values of the system outputs for the next ten intervals.

38. The apparatus according to claim 37, wherein the second differencing means is operable to determine differences for intervals from the third to the tenth intervals subsequent to the current interval.

39. The apparatus according to claim 1, wherein the apparatus comprises a processor and memory storing a sequence of instructions for execution by the processor.

40. The combination according to claim 1, wherein the system is a compression-ignition engine.

41. The combination according to claim 40, wherein the first number is two and the second number is two.

42. The combination according to claim 41, wherein the system comprises a variable geometry turbocharger and a variable exhaust gas recirculator and wherein the system inputs are the settings of the variable geometry turbocharger and of the variable exhaust gas recirculator and the system outputs are mass airflow and mass exhaust gas recirculation flow.

43. A computer program product comprising processor executable instructions defining a program for use in a processor based apparatus for controlling a system having a first number of system inputs and a second number of system outputs, by outputting, at intervals, signals for updating the system inputs, the program defining:

means for receiving one or more signals indicative of target values for the system outputs;

mapping means for using steady state information that relates the system outputs to the system inputs under steady state conditions, to determine a number, equal to the first number, of steady state values for the system inputs on the basis of the target output values;

means for receiving a number, equal to the second number, of signals indicative of the system outputs;

initial value means for producing at least one set of initial values, wherein each set consists of a number, equal to the first number, of values for use as a basis for determining a set of update values, wherein the set of update values consists of a number, equal to the first number, of values for updating the system inputs;

prediction means for using a model of the system to predict, for each set of initial values, a set of future values of the system outputs on the basis of past system input values, past system output values and a respective set of initial values;

first differencing means for determining differences between the steady state values and each set of initial values to give first difference information;

second differencing means for determining differences between the target values and each set of predicted future values of the system outputs to give second difference information;

combining means for combining the first difference information with the second difference information to give combined difference information;

determining means for determining the set of update values on the basis of the combined difference information and each set of initial values; and

output means for outputting signals, indicative of the set of update values, for updating the system inputs.

44. The product according to claim 43, wherein the product is a programmed memory device.

45. The product according to claim 44, wherein the product is a signal suitable for transfer from a first processor based apparatus to a second processor based apparatus.

46. The product according to claim 45, wherein the second processor based apparatus is an apparatus comprising a processor and memory storing a sequence of instructions for execution by the processor.

47. A method of controlling a system having a first number of system inputs and a second number of system outputs, by outputting, at intervals, signals for updating the system inputs, the method comprising the steps of:

receiving one or more signals indicative of target values for the system outputs;

determining, on the basis of steady state information that relates the system outputs to the system inputs under steady state conditions, a first number of steady state values for the system inputs on the basis of the target output values;

receiving a number, equal to the second number, of signals indicative of the system outputs;

producing at least one set of initial values, wherein each set consists of a number, equal to the first number, of values for use as a basis for determining a set of update values, wherein the set of update values consists of a number, equal to the first number, of values for updating the system inputs;

using a model of the system to predict, for for each set of initial values, a set of future values of the system outputs on the basis of past system input values, past system output values and a respective set of initial values;

determining differences between the steady state values and each set of initial values to give first difference information;

determining differences between the target values and each set of predicted future values of the system outputs to give second difference information;

combining the first difference information with the second difference information to give combined difference information;

determining the set of update values on the basis of the combined difference information and each set of initial values; and

outputting signals, indicative of the set of update values, for updating the system inputs.