Method and system for planning predictive pre-compensation

Abstract

The present disclosure provides methods and systems for planning the demand of an inner loop of a process. A loop controller includes an inner loop control system configured to generate a control output signal for a controllable element and a plan demand module configured to receive parameter values of a controlled variable of a process from a parameter source and generate a plan demand output using a demand plan. The loop controller also includes a plan prediction module configured to predict future values of a plan parameter based on historical performance of the inner loop control system and dynamic characteristics of a current system and generate a plan rate output. The plan prediction module includes a rate of change of a plan parameter and a lead time input defining a look-ahead period used with the parameter rate signal to determine a future predicted value of the controlled variable.

Description

TECHNICAL FIELD

[0001] The field of the disclosure relates generally to process control loops, and more specifically to methods and systems for reducing ramp tracking error of a process control device. BACKGROUND

[0002] In designing inner loops of a control system to mitigate ramp tracking error of a process control device, the balance between transient tracking capability and steady state stability can be difficult to maintain. Damped inner loops provide predictable stable results. However, as the inner loop ramp rate increases, transient tracking error becomes increasingly evident. This can drive more aggressive tuning of the inner loop to meet transient performance requirements. Aggressive gain and traditional feed forward methods result in overshoot and undesirable stability challenges.

[0003] Transient tracking of scheduled engine parameters is typically a tradeoff between inner loop stability and inner loop frequency response. Designing an inner loop system with a frequency response characteristic that has low transient tracking can result in an under-damped response that is less stable with excessive overshoot during transients.

[0004] More stable inner loop designs are either damped or critically damped. While critically damped inner loops perform well, transient tracking error can be large for overall system design. Critically damped systems have a response that lags the demand input. This lag is typically associated with a deterministic amount of time delay. This time lag creates a transient tracking error that is proportional to the demand ramp rate. SUMMARY

[0005] In one embodiment, a loop controller includes an inner loop configured to generate a control output signal for a controllable element, and a schedule demand module configured to receive parameter values of a controlled variable of a system process from one or more parameter sources, and generate a scheduled demand output using a demand schedule. The loop controller also includes a schedule prediction module configured to predict future values of a scheduled parameter based on historical performance of the inner loop control system and dynamic characteristics of a current system, and generate a scheduled rate output using a rate of change of the scheduled parameter. The schedule prediction module includes a rate of change of a scheduling parameter and a lead time input that defines a look-ahead time period used with the parameter rate signal to determine a future predicted value of the controlled variable.

[0006] Optionally, the one or more parameter sources include physical sensors, virtual sensors, electronic model results, algorithm results, and combinations thereof. Also optionally, the one or more parameter sources include output from a computer system monitoring at least one controlled variable. The inner loop control system can have a damped response.

[0007] Optionally, the plan prediction module is configured to compensate for dynamic properties of an inner loop control system by anticipating a period of time into the future defined by the lead time input that will require a future value of the control output signal of the controllable member, such that the control output signal follows the plan demand output without significant transient tracking error. Also optionally, the inner loop control system includes a first summing junction configured to receive the plan rate output and the plan demand output and generate a first summing junction output. The inner loop control system can include a second summing junction configured to receive the first summing junction output and the plan demand output and generate an inner loop demand signal.

[0008] In another embodiment, a method of planning an inner loop demand of a process control system based on a rate of change of a planned parameter and a selectable future time period. The method includes receiving, by a sensing system, sensed values for controlled variables of the process from one or more sensors; using the sensed values, determining, for each of at least one controlled variable of the process, a value to be applied to the inner loop, each value of the at least one controlled variable being determined based on the rate of change of the planned parameter and the selectable time period.

[0009] Optionally, the method includes receiving values of controlled variables of the process from one or more of a physical sensor, a virtual sensor, an electronic model result, an algorithm result, and combinations thereof. Also optionally, the method includes combining a demand plan for the controlled variables with a prediction of a planned parameter based on a rate of change of the planned parameter. The method can also include determining a time shift of the inner loop. Optionally, the method includes receiving a speed value of a rotatable member of a rotatable machine, determining an acceleration of the rotatable machine using the received speed value, and applying an acceleration rate of change signal. Also optionally, the method includes receiving a pressure value of a process system, determining a rate of change of the pressure value using the received pressure value; and applying a pressure rate of change signal.

[0010] In yet another embodiment, a loop controller, comprising: an inner loop control system configured to generate a control output signal for a controllable element; and a plan demand module configured to receive parameter values of controlled variables of a system process from one or more parameter sources and generate a plan predicted demand output using: a demand plan; and a plan prediction module configured to predict future values of a plan parameter based on historical performance of the inner loop control system and dynamic characteristics of a current system and generate the plan predicted demand output using lead / lag compensation and the demand plan.

[0011] Optionally, the demand plan comprises at least one of: a lookup table, a model, an algorithm, or a combination thereof. Also optionally, the one or more parameter sources comprise outputs from a computer system monitoring at least one controlled variable. Optionally, the plan predicted demand output is generated using a demand plan and a plan prediction module. The plan prediction module provides lead compensation ahead of the demand plan. Optionally, the demand plan and the plan prediction module are configured to predict future values of the plan parameter based on historical performance of the inner loop control system and dynamic characteristics of a current system.

[0012] Technical Solution 1. A method of planning inner loop demand of a process control system based on a rate of change of a plan parameter and a selectable future time period, the method comprising:

[0013] receiving, by a sensing system, sensed values for controlled variables of the process from one or more sensors;

[0014] determining, using the sensed values, for each of at least one controlled variable of the process, a value to be applied to the inner loop, each value of the at least one controlled variable determined based on the rate of change of the plan parameter and the selectable time period;

[0015] applying the determined value to an input of the inner loop; and

[0016] generating, by the inner loop, a control output signal for a controllable element.

[0017] Technical Solution 2. The method of Technical Solution 1, wherein receiving, by a sensing system, values for controlled variables of the process from one or more sensors comprises receiving values for controlled variables of the process from one or more of: physical sensors, virtual sensors, electronic model results, algorithm results, and combinations thereof.

[0018] TECHNICAL SOLUTION 3. The method of technical solution 1, wherein determining, for each of the at least one controlled variable of the process, a value to apply to the inner loop includes combining a demand plan for the controlled variable with a prediction of a planned parameter based on a rate of change of the planned parameter.

[0019] TECHNICAL SOLUTION 4. The method of technical solution 1, further comprising determining a time shift for the inner loop.

[0020] TECHNICAL SOLUTION 5. The method of technical solution 1, wherein receiving, by the sensing system, sensed values of a controlled variable of the process from one or more sensors includes receiving a plurality of values of a speed of a rotatable member of a rotatable machine, the method further comprising:

[0021] determining, using the received plurality of speed values, an acceleration of the rotatable machine; and

[0022] applying a rate of change of acceleration plan.

[0023] TECHNICAL SOLUTION 6. The method of technical solution 1, wherein receiving, by the sensing system, sensed values of a controlled variable of the process from one or more sensors includes receiving a pressure value of a process system, the method further comprising:

[0024] determining, using the received pressure value, a rate of change of the pressure value; and

[0025] applying a rate of change of pressure plan.

[0026] TECHNICAL SOLUTION 7. A loop controller comprising:

[0027] an inner loop control system configured to generate a control output signal for a controllable member; and

[0028] a plan demand module configured to receive parameter values of a controlled variable of a system process from one or more parameter sources and generate a plan predicted demand output using:

[0029] a demand plan;

[0030] a rate of change of the planned parameter to generate a plan rate output; and

[0031] a plan prediction module configured to predict future values of the planned parameter based on historical performance of the inner loop control system, the plan rate output, and dynamic characteristics of a current system and generate the plan predicted demand output using lead / lag compensation and the demand plan.

[0032] TECHNICAL SOLUTION 8. The loop controller of TECHNICAL SOLUTION 7, wherein the demand plan comprises at least one of the following: a lookup table, a model, an algorithm, or a combination thereof.

[0033] TECHNICAL SOLUTION 9. The loop controller of TECHNICAL SOLUTION 7, wherein the one or more parameter sources comprise an output from a computer system monitoring at least one controlled variable.

[0034] TECHNICAL SOLUTION 10. The loop controller of TECHNICAL SOLUTION 7, wherein the inner loop control system has a damped response.

[0035] TECHNICAL SOLUTION 11. The loop controller of TECHNICAL SOLUTION 7, wherein the planned predicted demand output is generated using a demand plan and a planned prediction module.

[0036] TECHNICAL SOLUTION 12. The loop controller of TECHNICAL SOLUTION 11, wherein the planned prediction module provides lead compensation ahead of the demand plan.

[0037] TECHNICAL SOLUTION 13. The loop controller of TECHNICAL SOLUTION 11, wherein the demand plan and the planned prediction module are configured to predict future values of the planned parameter based on historical performance of the inner loop control system and dynamic characteristics of the current system. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figures 1 to 8 An example embodiment of the methods and apparatus described herein is shown.

[0039] Figure 1 is a schematic cross-sectional view of a gas turbine engine according to an example embodiment of the disclosure.

[0040] Figure 2 is a flowchart of a method of planning an inner loop demand of a process control system.

[0041] Figure 3 is a schematic diagram of a loop controller that can be used Figure 2 is a schematic diagram of a loop controller that can be used

[0042] Figure 4 is a schematic diagram of a loop controller that can be used Figure 2 is a schematic diagram of a loop controller that can be used

[0043] Figure 5 is an example actuator position plan for a relative control parameter (e.g., engine speed).

[0044] Figure 6 is a graph of actuator response for speed up and down using a simple proportional control method.

[0045] Figure 7 is a graph of the response of an actuator using feedforward lead compensation for speed increases and decreases.

[0046] Figure 8 is a graph of the response of an actuator using schedule predictive lead compensation (SPLC) for speed increases and decreases for example embodiments of the present disclosure.

[0047] Although specific features of various embodiments can be shown in some drawings and not in others, this is merely for convenience. Any feature as referenced and / or claimed in conjunction with any drawing can be referenced and / or claimed in conjunction with any other drawing.

[0048] The drawings provided herein are used to illustrate features of embodiments of the present application and are not intended to be all-inclusive of the features that would be required to practice the embodiments disclosed herein. Thus, the drawings are not intended to include all of the features that would be necessary to practice the embodiments disclosed herein. DETAILED DESCRIPTION

[0049] The following detailed description describes embodiments of the present disclosure by way of example and not by way of limitation. It is contemplated that the present disclosure has general application to the analysis and method embodiments of schedule predictive lead compensation for inner loops in industrial, commercial, and residential applications.

[0050] The schedule predictive lead compensation described herein differs from traditional feedforward techniques in that information from the schedule parameters is used in determining the demand lead.

[0051] Schedule predictive lead compensation allows the design of a damped inner loop control system to meet steady state targets while not sacrificing transient tracking performance. Schedule predictive lead compensation compensates for the dynamic characteristics of the inner loop by anticipating the demand that the control output should have in the future, so the control output can follow the actual schedule without significant transient tracking error.

[0052] Schedule predictive lead compensation preserves the stability of the damped system. Schedule predictive lead compensation responds to the inner loop as a black box with a first or second order damped response and compensates for the lag effect. Schedule predictive lead compensation compensates for the input demand by anticipating the amount of time lag defined by the inner loop response.

[0053] In some embodiments, schedule predictive lead compensation is designed to benefit from two assumptions; 1) the inner loop control system can be characterized as a first order damped response or a second order damped response, and 2) the schedule parameters have some inertia such that instantaneous changes are not possible. More specifically, the dynamic changes of the schedule parameters are typically slower than the dynamic response of the inner loop control system.

[0054] This plan prediction lead compensation method uses the knowledge of the plan parameter to "lead" the demand plan by using the rate of change of the plan parameter and a look-ahead of the expected inner loop response time lag. By using this method, plan prediction lead compensation can greatly improve transient tracking without causing the overshoot that can occur with traditional feedforward methods. Although described herein with reference to gas turbine engine plan inner loops such as fan variable geometry (FVG) and compressor variable geometry (CVG), it should be understood that plan prediction lead compensation can be adapted to other engine inner loops or industrial applications that use a plan parameter. For example, the rate of change of the plan parameter calculation can be performed by different methods for each of a number of different specific applications. Also, the threshold or saturation limit of the basic plan prediction lead compensation design can be modified to suit a specific application.

[0055] The following description refers to the accompanying drawings, wherein like reference numerals refer to like elements in the several Figures.

[0056] Figure 1 is a schematic illustration of a gas turbine engine 100 including a fan assembly 102, a high pressure compressor 104 including a plurality of circumferentially spaced compressor inlet guide vane (IVG) assemblies 105, and a combustion chamber 106. In one embodiment, the gas turbine engine 100 is an F-110 engine, which is commercially available from General Electric Company, Cincinnati, Ohio. The gas turbine engine 100 also includes a high pressure turbine 108 and a low pressure turbine 110, all arranged in serial axial flow relationship. The fan assembly 102 and turbines 110 are coupled by a first shaft 112, and the high pressure compressor 104 and high pressure turbine 108 are coupled by a second shaft 114.

[0057] The gas turbine engine 100 also includes an annular frame 116 that supports a bearing 118, which in turn supports an end of the first shaft 112 for rotation thereby. A plurality of circumferentially spaced fan inlet guide vane (IGV) assemblies 120 extend between an outer structural casing ring 122 and a central hub 124 to direct airflow into the gas turbine engine 100.

[0058] In operation, air flows through the fan IGV assembly 120 and through the fan assembly 102 such that compressed air is supplied from the fan assembly 102 to the high pressure compressor 104 to produce further highly compressed air. The highly compressed air is delivered to the combustion chamber 106. Combustion gases from the combustion chamber 106 drive the rotating turbines 108 and 110 and exit the gas turbine engine 100 through the exhaust nozzle 126. The gas turbine engine 100 is capable of operating over a range of operating conditions between design operating conditions and operating conditions outside of the design.

[0059] Generally, the gas turbine engine 100 includes a plurality of sensors and control system elements to position the variable geometry of the fan IGV assembly 120 and the compressor IGVs, among other functions. For example, in various embodiments, the gas turbine engine 100 includes an actuator ring 128 operably coupled to the fan IGV assembly 120. The position of the actuator ring 128 is controlled by an IGV actuator 130, which receives a control signal 132 from, for example, a computer system (e.g., an electronic controller 134). In some embodiments, the electronic controller 134 is implemented in, for example, an engine electronic control (EEC), an adaptive fault tolerant controller (AFTC), or other flight control computer. Sensors 136 (e.g., an inlet temperature sensor T2) generate output signals representative of measured parameters related to the gas turbine engine 100. In the example embodiment, the electronic controller 134 is programmed to adjust the position of the fan IGV assembly 120 using inputs from the sensors 136, which is described in detail below.

[0060] The gas turbine engine 100 is depicted in the figures merely as an example, and in other exemplary embodiments, the gas turbine engine 100 can have any other suitable configuration, including, for example, a turboprop engine, a turbojet engine, a military purpose engine, and a sea- or land-based converted engine.

[0061] Figure 2is a flowchart of a method 200 of inner loop demand of a planning process control system. The method 200 is based on a rate of change of a planned parameter of a controlled variable of a process and a selectable future time period. The controlled variable of the process can include a pressure parameter, a speed parameter, a temperature parameter, and the like. Thus, the rate of change of the planned parameter of these controller variables are referred to as a pressure rate of change plan, a speed rate of change plan, and a temperature rate of change plan, respectively. In the example embodiment, the method 200 includes generating 202 a look ahead time to offset a response delay expected by the inner loop control system, determining 204 future predicted values of the planned parameter using a trajectory / rate of change of the control parameter and the look ahead time, and applying 206 the determined predicted values to the plan to determine a predicted input of the inner loop control system. A sensing system, such as the sensor 136, can provide sensed values of the controlled variable of the process being controlled. The sensor 136 can include physical sensors, virtual sensors, electronic model results, algorithm results, and combinations thereof.

[0062] Figure 3 is a schematic diagram of a loop controller 300 that can be used in a gas turbine engine 100 Figure 1 shown in FIG. 1. In the example embodiment, the loop controller 300 includes an inner loop control system 302 configured to generate a control output signal 304 of a controllable member 306, such as but not limited to a modulating actuator 130 connected to a variable inlet vane assembly 105, 120. The loop controller 300 also includes a planning demand module 308 configured to receive parameter values 310 of a controlled variable 312 of a system process from one or more parameter sources 314 and generate a planned demand output 316 using a demand plan 318. In the example embodiment, the demand plan 318 represents an expected or future value of the inner loop demand given a value of a planned parameter 321. The demand plan 318 can be implemented as a lookup table, a model, an algorithm, or combinations thereof. In various embodiments, the one or more parameter sources 314 can be implemented as physical sensors, virtual sensors, electronic model results, algorithm results, and combinations thereof. In other embodiments, the one or more parameter sources 314 can be implemented from an output of another system, such as but not limited to an engine electronic control (EEC), a full authority digital electronic control (FADEC), a flight control computer, or combinations thereof.

[0063] The schedule prediction module 320 is configured to predict future values of the schedule parameter 321 based on a current rate of change of the schedule parameter 321 and a performance of the inner loop control system 302 expected based on dynamic characteristics of the system to generate a look-ahead schedule parameter bias signal 330. In one embodiment, the schedule parameter 321 can represent a core speed value of the gas turbine engine 100. In the described example embodiment, the schedule prediction module 320 includes a rate of change of schedule parameter 322 that is associated with a predetermined value for the controlled variable 312, a corresponding value for the controllable element 306, and a lead time input 326 that defines a look-ahead period to be used with the rate of change of schedule parameter 322 to determine the look-ahead schedule parameter bias signal 330 to be added to the schedule parameter 321 to produce a future predicted value of the schedule parameter 321.

[0064] The lead time input 326 is related to the capability of the inner loop control system 302 that is designed with a known damping frequency response. If the known damping frequency response is known, then a prediction of the time lead is determined. Thus, the lead time can be a function of certain parameters, such as a load on the actuator 130. The schedule prediction module 320 is configured to compensate for the dynamic characteristics of the inner loop control system 302 to cause the control output signal 304 to follow the schedule demand output 316 without significant transient tracking errors by anticipating the period of time that the future value of the inner loop demand signal 338 needs to be looked ahead to.

[0065] The predicted demand schedule 328 is the same as the demand schedule 318 in that it represents the ideal schedule demand. The inner loop demand signal 338 provides an expected or future value of the inner loop given the current value and rate of change of the schedule parameter 321. In this case, the predicted future value of the schedule parameter 321 is its input and the output of the predicted demand module 328 is the look-ahead schedule output 324 for the inner loop control system 302.

[0066] The schedule prediction module 320 includes a first summing node 332 that is configured to receive the look-ahead schedule output 324 and the schedule demand output 316 and generate a first summing node output 334 that provides a look-ahead bias to the primary inner loop schedule demand output 316. The schedule prediction module 320 also includes a second summing node 336 that is configured to receive the first summing node output 334 and the schedule demand output 316 and generate the inner loop demand signal 338 that is an input to the inner loop control system 302.

[0067] The schedule parameter 321 is the primary parameter used to determine how the inner loop control system 302 should respond. The rate of change of the schedule parameter 322 provides a current rate of change of the schedule parameter 321. In the example, the schedule parameter 321 represents rotor speed, which cannot change too rapidly due to system inertia. Thus, this rate provides a good prediction of future behavior of the schedule parameter 321. The schedule prediction lead compensation enables the inner loop control system 302 to react to impending changes in the schedule demand output 316 using the inner loop demand signal 338 before the regular schedule demand output 316 is reacted to, minimizing tracking error and overshoot.

[0068] Figure 4 is a schematic diagram of a loop controller 400 according to another example embodiment of the disclosure. The loop controller 400 includes an inner loop control system 402 configured to generate a control output signal 404 for a controllable element 406, and a schedule demand module 408 configured to receive schedule parameter values 410 for a controlled variable 412 of a system process from one or more parameter sources 414, and generate a predicted schedule demand output 415. The predicted schedule demand output 415 is generated using a demand schedule 416 and a schedule prediction module 417, which includes regular lead / lag compensation features to provide lead compensation for the schedule parameter 321, 419 ahead of the demand schedule 416. The demand schedule 416 and the schedule prediction module 417 are configured to predict future values of the schedule parameter 419 based on historical performance of the inner loop control system 402 and dynamic characteristics of the current system, and generate the predicted schedule demand output 415 using the schedule prediction module 417 and the demand schedule 416.

[0069] Figure 5 is a graph 500 of an example demand schedule that can be used in the loop controllers 300, 400 (shown in Figure 3 and Figure 4 respectively). The graph 500 includes an x-axis 502, which is scaled in units of the schedule parameter, such as but not limited to speed, temperature, pressure, etc. The graph 500 also includes a y-axis 504, which is scaled in units of actuator position, such as but not limited to position of the fan IGV assembly 120. The graph 500 includes a trace 506, which illustrates values of the example demand schedule 318, 416. In the example embodiment, between approximately x-axis units zero and x-axis units 3 on the x-axis 502, the trace 506 remains at a constant value, with a rate of change of zero. At x-axis unit 3, the trace 506 exhibits a significant positive rate of change. This rate of change continues to be positive, while the actuator position increases to approximately y-axis unit 5 at approximately x-axis unit 8. At x-axis unit 8, the rate of change of the trace 506 returns to approximately zero.

[0070] Figure 6is a graph 600 showing the response of a simple proportional-integral (PI) control system. The graph 600 illustrates the significant transient tracking error 601 caused by the lag in the response of the inner loop control system. The graph 600 includes an x-axis 602 scaled in units of time. The graph 600 also includes a y-axis 604 scaled in units of response, such as but not limited to the position of the fan IGV assembly 120. The graph 600 includes a trace 606 and a trace 608, the former showing the value of the real plan parameter versus time, and the latter showing the relationship of the real plan demand versus time. The graph 600 includes a trace 610 of the proportional-integral (PI) control response without compensation. The trace 610 lags the trace 608 significantly, continuing to track the trace 608 incorrectly during the transient, at transient points 612, 614.

[0071] Figure 7 is a graph 700 showing the response of a control system with traditional lead compensation. The graph 700 includes an x-axis 702 scaled in units of time and a y-axis 704 scaled in units of response, such as but not limited to the position of the fan IGV assembly 120. The graph 700 includes a trace 706 and a trace 708, the former showing the value of the real plan parameter versus time, and the latter showing the relationship of the real plan demand versus time. The graph 700 includes a trace 710 of the feedforward demand and a trace 712 of the feedforward response. The real plan demand trace 708 is the trace that the real plan demand trace 708 experiences of any transients or disturbances that the electronic controller 134 attempts to track. The feedforward response trace 712 is the trace that should coincide with the real plan demand trace 708. The feedforward demand trace 710 injects a control signal that is more aggressive than the proportional-integral (PI) control shown in the graph 600. Figure 6 The feedforward demand trace 710 improves the tracking error, however, it also increases the control overshoot at the beginning of the transient, and even more so at the end of the transient. For example, when the real plan demand trace 708 increases at time 2, the feedforward demand trace 710 spikes by a predetermined amount to turn the feedforward response trace 712 as quickly as possible, attempting to catch up to the feedforward response trace 712 to track the real plan demand trace 708. However, because the change in the real plan demand trace 708 was not anticipated, the feedforward response trace 712 overshoots the real plan demand trace 708 at time 2. Similar overshoots of the feedforward response trace 712 over the real plan demand trace 708 occur at times 5, 8, and 11. The lead compensation of the inner loop demand, the real plan demand trace 708, provides improved transient tracking error, but also causes significant error and overshoot due to the rapid changes in the plan position.

[0072] Figure 8is a graph illustrating the response of a control system with plan forecast lead compensation as described herein. Graph 800 includes an x-axis 802 scaled in units of time and a y-axis 804 scaled in units of response, such as, but not limited to, the position of the fan IGV assembly 120. Graph 800 includes a trace 806 showing the value of the actual plan parameter trace 806 versus time and a trace 808 showing the relationship of the actual plan demand trace 708 versus time. Graph 800 includes a trace 810 of the forecast plan parameter and a trace 812 of the forecast demand. Graph 800 includes a trace 814 of the forecast response. It is not like Figure 7 In this embodiment, the electronic controller 134 applies a predetermined plan forecast lead compensation scheme to the actual plan parameter trajectory 806, as described in the previous embodiment. The plan forecast lead compensation scheme provides the benefit of applying a lead compensation to the actual plan parameter trajectory 806 before the actual plan demand trajectory 808 turns. The plan forecast lead compensation provides improved error tracking without significant overshoot at transient points in the inner loop control system 302, 402. The predicted movement of the actual plan parameter trajectory 706 results in improved transient tracking, with substantially no errors or overshoots due to rapid changes in the planned position.

[0073] The aforementioned plan-predictive-lead compensation system provides an efficient method for improving transient tracking error while maintaining the desired characteristics of the damped inner-loop control system 302, 402. Specifically, the aforementioned plan-predictive-lead compensation anticipates a predetermined time value and applies the plan change upstream of the inner loop. Plan-predictive-lead compensation is applicable to, but not limited to, planning parameters against inertia-limited parameters, such as fan speed or core speed. Some examples include fan inlet guide vanes or core variable stator vanes (VSVs). Reducing transient tracking error allows the engine to operate closer to its stability limit, resulting in performance gains. The inner-loop design can focus more on steady-state stability performance rather than adjusting transient performance.

[0074] Exemplary technical effects of the methods, systems, and apparatus described herein include at least one of the following: (a) improved transient tracking error while maintaining a desired damped inner loop response characteristic, (b) applicable to parameters that are planned against inertia-limited parameters (e.g., fan speed or core speed), (c) applying lead compensation to the relatively low frequency response of the planned parameter captures transient effects while also capturing high frequency planned ramp changes, (d) achieving a lead compensation feature without many drawbacks (e.g., overshoot) by using additional information from the planned and engine parameters, (e) compensating for input demands by looking ahead with a lag time amount defined by the inner loop control system response, and (f) enabling inner loop control design to focus more on steady-state stability performance rather than adjusting for transient performance.

[0075] The above embodiments of the method and system for plan prediction feed forward compensation provide a cost effective and reliable means for stabilizing the operation of the inner loop of damping in very fast applications. More specifically, the methods and systems described herein facilitate anticipating control changes and responding to these changes with predictive plan changes. As a result, the methods and systems described herein facilitate improving the performance of an engine in a cost effective and reliable manner.

[0076] Although specific features of various embodiments of the present application can be shown in some of the figures and not in others, this is for convenience only. In accordance with the principles of the present application, any of the features of any of the figures can be referenced and / or claimed in combination with any of the other figures.

[0077] This written description uses examples to disclose the embodiments, including the best mode, and also to enable any person skilled in the art to practice the embodiments, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the application is defined by the claims, and can include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

Claims

1. A method for planning inner loop requirements of a process control system based on a rate of change of a planned parameter of the process and a selectable future time period, the method comprising: receiving, by a sensing system, sensed values ​​of controlled variables for the process from one or more sensors; using the sensed values, determining, for each of at least one controlled variable of the process, a value to be applied to the inner loop; applying a determined value to an input of the inner loop; as well as generating a control output signal for a controllable component by the inner loop; The method further includes determining a future predicted value of the plan parameter using the rate of change of the plan parameter and the associated look-ahead time, and applying the determined predicted value to the plan to determine a predicted input to an inner loop control system.

2. The method according to claim 1, wherein Receiving, by the sensing system, values ​​of controlled variables for the process from one or more sensors includes receiving values ​​of controlled variables for the process from one or more of physical sensors, virtual sensors, electronic model results, algorithm results, and combinations thereof.

3. The method according to claim 1, wherein For each of at least one controlled variable of the process, determining a value to apply to the inner loop includes combining a demand plan for the controlled variable with a forecast of a plan parameter based on a rate of change of the plan parameter. The method of claim 1 , further comprising determining a time shift of the inner loop.

5. The method according to claim 1, wherein Receiving, by a sensing system, sensed values ​​of a controlled variable of the process from one or more sensors includes receiving a plurality of values ​​of a speed of a rotatable component of a rotatable machine, the method further comprising: determining an acceleration of the rotatable machine using the received plurality of velocity values; and Apply a speed change rate schedule.

6. The method according to claim 1, wherein Receiving, by the sensing system, a sensed value of a controlled variable of the process from one or more sensors includes receiving a pressure value of the process system, the method further comprising: determining a rate of change of the pressure value using the received pressure value; and Apply a pressure rate schedule.

7. A loop controller for performing the method according to any one of claims 1 to 6, comprising: an inner loop control system configured to generate a control output signal for a controllable component; as well as A planned demand module configured to receive parameter values ​​of controlled variables of a system process from one or more parameter sources and generate a planned forecast demand output using: Demand planning; a rate of change of the planning parameter used to generate a planning rate output; as well as A plan prediction module is configured to predict future values ​​of plan parameters based on the historical performance of the inner-loop control system, the plan rate output, and the dynamic characteristics of the current system, and to generate the plan predicted demand output using lead / lag compensation and the demand plan.

8. The loop controller according to claim 7, wherein: The demand plan includes at least one of: a lookup table, a model, an algorithm, or a combination thereof.

9. The loop controller according to claim 7, wherein: The one or more parameter sources include output from a computer system that monitors at least one controlled variable.

10. The loop controller according to claim 7, wherein: The inner loop control system has a damped response.

11. The loop controller according to claim 7, wherein: The demand planning and forecasting modules are used to generate the planned forecast demand output.

12. The loop controller according to claim 11, wherein: The plan forecasting module provides lead compensation ahead of the demand plan.

13. The loop controller according to claim 11, wherein: The demand planning and the plan prediction modules are configured to predict future values ​​of the plan parameters based on historical performance of the inner loop control system and current system dynamics.

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