A model-based dynamic anti-saturation method and device for aviation engine fuel control system

Abstract

This invention provides a model-based dynamic anti-windup method and device for an aircraft engine fuel control system. The method comprises establishing a nonlinear component-level model of the aircraft engine and obtaining a state-space model of the aircraft engine using a Taylor series expansion method; establishing a linear dynamic controller based on the aircraft engine state-space model; and designing a dynamic anti-windup compensator for the aircraft engine's fuel supply actuator. The device includes a personal computer terminal, input and output ports for digital-to-analog conversion, an electronic engine control unit designed based on a digital signal processor in the personal computer terminal, and a data bus converter. This invention can improve aircraft engine control performance throughout the entire flight envelope.

Description

Technical Field

[0001] The present invention belongs to the field of control, and in particular relates to a model-based dynamic anti-saturation method and device for an aviation engine fuel control system. Background Art

[0002] In the design of aircraft engine control systems, in addition to ensuring the engine operates within a wide range of maneuvers and flight envelopes, achieving optimal performance, engine safety must also be considered. To ensure that the engine does not exceed its maximum mechanical, thermal, airflow, and pressure limits during operation, and to ensure the proper acceleration and deceleration of the compression components (fan and compressor), surge protection, and stall protection, the actual controller design process often employs the method of adding fuel control limits to ensure safe and stable engine operation.

[0003] Adding restrictions to fuel control can lead to saturation of the fuel supply actuator. Fuel supply actuator saturation can increase the system's output error, reduce tracking performance, increase adjustment time, and even make the closed-loop system unstable. Therefore, for actual aircraft engines, the fuel supply actuator needs to be compensated to increase system stability. There are two common treatment methods, namely direct and indirect methods. The idea of ​​the direct method is to consider actuator saturation when designing the controller and directly incorporate saturation processing into the controller design. The indirect method is also called anti-saturation compensation method. Its idea is to separate the controller design and saturation processing processes. That is, one part of the controller is used to achieve nominal performance, and the other part is used to eliminate the negative effects of actuator saturation as much as possible.

[0004] In the anti-windup compensation method, the linear controller design approach is used to design a linear nominal controller. Saturation constraints are first considered, and then an anti-windup compensator is designed to address these constraints. The purpose of the anti-windup compensator is to ensure stability while minimizing the degradation in control performance compared to a non-saturation state. Since no constraints are imposed during the design of the linear nominal controller, this controller determines the closed-loop system's behavior when saturation is not triggered. Only when the actuator saturates does the anti-windup compensator take effect and correct the closed-loop behavior, making the system's response to saturation more stable.

[0005] Existing anti-windup compensation methods fail to account for reasonable transient variations in the presence of constraints and, more importantly, fail to account for the uncompensated tracking of the closed-loop system output relative to the setpoint due to input constraints. Furthermore, due to limited onboard resources and high real-time requirements, aircraft engine anti-windup compensation algorithms require low computational complexity. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention provides a model-based dynamic anti-saturation method and device for aircraft engine fuel control systems to address the issue of fuel supply actuator saturation. Furthermore, given the limited onboard resources and high real-time requirements of aircraft engines, the present invention proposes a hardware architecture to implement this strategy.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A model-based dynamic anti-saturation method for an aircraft engine fuel control system includes the following steps:

[0009] Step 1: Establish a nonlinear component-level model of the aircraft engine and use the Taylor series expansion method to obtain the state space model of the aircraft engine:

[0010]

[0011] In the above formula, A p , B p , C p , D p is the coefficient matrix of the state space model, x p (t)=[n H (t) n L (t)] T is the state quantity of the system, where n H (t) is the high pressure compressor rotor speed, n L (t) is the low-pressure compressor rotor speed; u(t) = m f (t) is the control quantity of the system, where m f (t) is the fuel flow rate; y p (t)=[n H (t) n L (t)] T is the measurable output of the system, where n H (t) is the high pressure compressor rotor speed, n L (t) is the low-pressure compressor rotor speed, and t is time;

[0012] Step 2: Based on the state-space model of the aircraft engine obtained in step 1, establish a linear dynamic controller:

[0013]

[0014] In the above formula, A c , B c , C c , D cis the coefficient matrix of the linear dynamic controller of appropriate dimension. In the absence of actuator saturation, the closed-loop system composed of the state space model obtained in step 1 and the linear dynamic control is stable and has the desired closed-loop system performance. c (t) is the state of the controller. When the fuel supply actuator of the aircraft engine is not saturated, u c (t) = y p (t) is the measurable output of the aircraft engine, y c (t) = u(t) is the output signal of the linear dynamic controller, y c (t) is also the actuator input signal when the fuel supply actuator of the aircraft engine is not saturated, y r (t) is the high-pressure compressor rotor speed command;

[0015] Step 3: Design the dynamic anti-saturation compensator for the aircraft engine fuel supply actuator:

[0016] When the fuel supply actuator of the aircraft engine is not saturated, a linear dynamic controller is used; when the fuel supply actuator is saturated, a dynamic anti-saturation compensator is activated.

[0017]

[0018] y aw (t) = C p x aw (t)+D p (sat(u(t))-y c (t))

[0019] In the above formula, x aw (t) is the state of the anti-saturation compensator, y aw (t) is the output of the anti-saturation compensator, where u min is the lower limit of the output of the fuel supply actuator, u max The output upper limit of the fuel supply execution structure; A p , B p , C p , D p is the coefficient matrix of the anti-saturation compensator of appropriate dimension.

[0020] The present invention also provides an apparatus for implementing a model-based dynamic anti-saturation method for an aviation engine fuel control system, comprising a personal computer terminal, input and output ports for digital-to-analog conversion, a power supply, an electronic engine control unit designed based on a digital signal processor, and a data bus converter;

[0021] The personal computer terminal is used to input command signals in a MATLAB / Simulink environment and to run a component-level aircraft engine model and a mathematical model of a fuel supply actuator as a controlled object;

[0022] The input and output ports of the digital-to-analog conversion are used to convert the received digital signal into analog signal and vice versa;

[0023] An electronic engine control unit designed based on a digital signal processor is used to run the model-based dynamic anti-saturation method for the aviation engine fuel control system;

[0024] The data bus converter is used for signal transmission between the electronic engine control unit designed based on the digital signal processor and the input and output ports of the digital-to-analog converter;

[0025] The power supply is used to power the electronic engine control unit which is designed based on a digital signal processor.

[0026] Beneficial effects:

[0027] The model-based dynamic anti-saturation method and device for an aircraft engine fuel control system proposed in this invention offer superior resistance to fuel input saturation compared to static anti-saturation compensation methods. Furthermore, the use of a dynamic compensator ensures the transient performance of the closed-loop system. Under constraints, the transient response of the proposed method surpasses that of a static compensator. Furthermore, the proposed model-based dynamic anti-saturation compensation strategy can further improve aircraft engine control performance throughout the entire flight envelope.

[0028] In view of the limited onboard computing resources and high real-time requirements, the hardware architecture proposed in this invention realizes the hardware-in-the-loop simulation of the dynamic anti-saturation compensation strategy of the aviation engine fuel control system based on the model. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is an architectural diagram of the model-based dynamic anti-saturation method for an aviation engine fuel control system of the present invention.

[0030] Figure 2 This is a hardware architecture diagram of the model-based dynamic anti-saturation method for aviation engine fuel control systems proposed in this invention.

[0031] Figure 3 The high-pressure compressor rotor speed response diagram corresponding to various controllers under a given high-pressure compressor rotor speed instruction.

[0032] Figure 4 The fuel flow input diagram corresponding to various controllers under a given high-pressure compressor rotor speed command.

[0033] Figure 5 The compressor surge margin response diagram corresponding to various controllers under a given high-pressure compressor rotor speed command. DETAILED DESCRIPTION

[0034] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0035] The model-based dynamic anti-saturation method for an aviation engine fuel control system of the present invention is implemented by software and hardware.

[0036] The software includes: a digital model of the engine as the controlled object, a dynamic anti-saturation compensator, and a linear dynamic controller. The dynamic anti-saturation compensator is activated only when the actuator is saturated. When the actuator is not saturated, the closed-loop system is in an unrestricted linear state and needs to meet the expected performance requirements. When the actuator is saturated, the dynamic anti-saturation compensator will take effect, making the response of the closed-loop system as close as possible to the response of the unrestricted system. The specific structure is as follows: Figure 1 shown.

[0037] The hardware includes: an electronic engine control unit based on a digital signal processor, a power supply, a data bus converter, multiple input and output ports for digital-to-analog conversion, and a personal computer terminal. The specific model of the digital signal processor is DSPTMS320F28035, and the CPU of the personal computer terminal is i7-8700. The specific structure is as follows Figure 2 shown.

[0038] Specifically, if Figure 1 As shown, this paper proposes a model-based dynamic anti-windup method for aircraft engine fuel control systems. The dynamic anti-windup compensator designed based on this strategy effectively addresses the impact of fuel supply actuator saturation on the system's closed-loop performance. This method primarily consists of three components: a digital model of the aircraft engine (including a nonlinear component-level model and a state-space model), a dynamic anti-windup compensator, and a linear dynamic controller.

[0039] Step 1: A nonlinear component-level model of the aircraft engine is established based on torque balance, flow balance, and power balance, and the state space model of the aircraft engine is obtained using the Taylor series expansion method.

[0040]

[0041] In the above formula, A p , B p , C p , D p is the coefficient matrix of the state space model, x p (t)=[n H (t) n L (t)] T is the state quantity of the system, where n H (t) is the high pressure compressor rotor speed, n L (t) is the low-pressure compressor rotor speed; u(t) = m f (t) is the control quantity of the system, where m f (t) is the fuel flow rate; y p (t)=[n H (t) n L (t)] T is the measurable output of the system, where n H (t) is the high pressure compressor rotor speed, n L (t) is the low-pressure compressor rotor speed, and t is time.

[0042] Step 2: Based on the state space model obtained in step 1, establish a linear dynamic controller.

[0043]

[0044] In the above formula, A c , B c , C c , D c is the coefficient matrix of the linear dynamic controller of appropriate dimension. In the absence of fuel supply actuator saturation, the closed-loop system composed of the state space model obtained in step 1 and the linear dynamic control is stable and has the desired closed-loop system performance. c (t) is the state of the controller. When the fuel supply actuator of the aircraft engine is not saturated, u c (t) = y p (t) is the measurable output of the aircraft engine, y c (t) = u(t) is the output signal of the linear dynamic controller, y c (t) is also the actuator input signal when the fuel supply actuator of the aircraft engine is not saturated, y r (t) is the high pressure compressor rotor speed command.

[0045] Step 3: Design a dynamic anti-saturation compensator for the aircraft engine fuel supply actuator. When the fuel supply actuator is saturated, the dynamic anti-saturation compensator is activated. Based on the state-space model obtained in Step 1, the following dynamic anti-saturation compensator is established with zero initial values.

[0046]

[0047] In the above formula, x aw (t) is the state of the anti-saturation compensator, y aw (t) is the output of the anti-saturation compensator, where u min is the lower limit of the output of the fuel supply actuator, u max It is the upper limit of the output of the fuel supply execution structure. p , B p , C p , D p is the coefficient matrix of the anti-saturation compensator of appropriate dimension.

[0048] At this time c (t) is the saturation of the fuel supply actuator u c (t) = y p (t)-y aw (t) is the output signal of the linear dynamic controller, so that the feedback signal received by the linear dynamic controller is the same as the ideal feedback signal, and the input of the anti-saturation compensator is sat(u(t))-y c (t) is the difference between the control signal before and after the saturation nonlinearity, and it will play a compensation role only when saturation occurs.

[0049] like Figure 1 As shown, the dynamic anti-saturation compensator of the present invention adopts the following interconnection method:

[0050] u(t)=y c (t)+v1(t)u c (t) = y p (t)+v2(t) (4)

[0051] Where v2 = -y aw (t), v1 is obtained through the following analysis.

[0052] When actuator saturation occurs, the dynamic anti-saturation compensator will affect the output y of the linear dynamic controller c (t), so that the response of the closed-loop system is as close as possible to the response of the unconstrained system, and the output of the linear dynamic controller at this time is defined as u un (t). At this time, the dynamic anti-saturation compensator will control the input u of the linear dynamic controller c (t) = y p (t)-y aw (t), improve the performance of the entire closed-loop system, and define the input of the linear dynamic controller at this time as y un(t). At the same time, define the state quantity at this time as x un (t) = x p (t)-x aw (t), Figure 1 The closed-loop system shown can be written as:

[0053]

[0054] If you select x aw When (0)=0, there is x un (0) = x p (0). And when x aw When (t) = 0, v1(t) = 0. If u(t) ≡ sat(u un (t)), x aw (0)≡0, and v1(t)≡0, v2(t)≡0, x aw (t) is the state of the dynamic anti-saturation compensator, v2(t) is the negative number of the dynamic anti-saturation compensator output, and v1(t) is the compensation value of the dynamic anti-saturation compensator to the output control quantity of the linear dynamic controller. At this time, the system with saturated actuators will regain the response performance of the system without saturation. According to the definition and Figure 1 ,y un (t) = y p (t)-y aw (t), y aw (t) reflects the mismatch between the saturated system and the non-saturated system. In order to make the dynamic response performance of the saturated system as close as possible to the dynamic response performance of the non-saturated system, y should be aw (t) is as small as possible.

[0055] Depend on Figure 1 It can be seen that u(t)≡sat(v1(t)+y c (t)), and y is known c (t)≡u un (t), so y aw (t) can be expressed as:

[0056]

[0057] According to existing literature, we select v1(t)=K(x aw (t)), where K(·) is an appropriate static function that can make y aw (t) is as small as possible and can well handle the problem of actuator saturation. Therefore, the present invention proposes a v1(t) design method based on linear function.

[0058] v1(t)=Kx aw(t)+L(sat(v1(t)+y c (t))-y c (t)) (7)

[0059] Among them, K and L are used to determine the asymptotic stability of the dynamic anti-saturation compensator (3) and v1(t). K and L are derived from a suitable matrix inequality, theorem is as follows:

[0060] Considering the state space model of the aircraft engine (1) and the linear dynamic controller (2), let Q j With R j Meet the LQ performance indicators, including:

[0061]

[0062] In formula (8), J is the LQ performance index corresponding to the dynamic anti-saturation compensator, Q j With R j is a symmetric positive definite matrix of appropriate dimension.

[0063] If there exists a matrix P = P T >0, Q=Q T >0, and the following linear matrix inequalities are satisfied, then the closed-loop system composed of equations (1), (2), (3), and (7) is globally stable.

[0064]

[0065]

[0066]

[0067] In formula (9), the Z matrix is ​​the inverse matrix of the P matrix, the W matrix is ​​the inverse matrix of the Q matrix, and S and T are the matrices generated by solving formula (9). The specific mathematical relationship is: Z = P -1 , W=Q -1 , S=KU,T=LW。

[0068] The linear matrix inequality package in MATALB is used to solve the above linear matrix inequality to obtain K and L, and complete the design of the dynamic anti-saturation compensator.

[0069] like Figure 2As shown, the present invention comprises an electronic engine control unit (ECU) designed based on a digital signal processor, a power supply, a data bus converter, multiple digital-to-analog converter input and output ports, and a personal computer terminal. First, the power supply is connected to the ECU. Then, the input port of the digital-to-analog converter is connected to the output port of the high-pressure compressor rotor speed command in the computer. The output port of the digital-to-analog converter is connected to the ECU. The ECU is connected to the data bus converter. The data bus converter is connected to the input port of the digital-to-analog converter. The output port of the digital-to-analog converter is connected to the input port of a fuel supply actuator in the computer. Finally, within the MATLAB / Simulink environment in the computer, the fuel supply actuator is connected to an aircraft engine model, and feedback of the aircraft engine high-pressure compressor rotor speed to the command input port is implemented.

[0070] like Figure 3 As shown in the figure, when there is a saturation limit on the fuel flow, the high-pressure compressor rotor speed response of the dynamic anti-saturation compensator exits the saturation of the fuel supply actuator earlier than the high-pressure compressor rotor speed response of the static anti-saturation compensator.

[0071] like Figure 4 As shown in the figure, when there is a saturation limit on the fuel flow, the fuel flow input generated by the dynamic anti-saturation compensator exits the saturation of the fuel supply actuator earlier than the fuel flow input generated by the static anti-saturation compensator, and the fuel flow input generated by the controller without the fuel flow saturation limit exceeds the saturation limit of the fuel flow.

[0072] like Figure 5 As shown in the figure, when there is a saturation limit on the fuel flow, the compressor surge margin response of the dynamic anti-saturation compensator is near the set limit value, the compressor surge margin response of the static anti-saturation compensator greatly exceeds the set limit value, and the compressor surge margin response of the controller without fuel flow saturation limit greatly exceeds the set limit value.

[0073] A component-level model of the aircraft engine is run within the MATLAB / Simulink environment on a personal computing terminal, and a high-pressure rotor speed command is input. The high-pressure rotor speed command and speed at each sampling moment are transmitted to the electronic engine control unit via the input and output ports of the digital-to-analog converter. After receiving this data, the electronic engine control unit calculates the fuel flow information at that moment using the method proposed in this invention. This fuel flow information is then input to the fuel supply actuator within the MATLAB / Simulink environment via the data bus and the input and output ports of the digital-to-analog converter. The fuel supply actuator then inputs the value of the fuel quantity to be supplied into the aircraft engine component model. All hardware modules then sequentially perform the above operations at each sampling moment until the hardware-in-the-loop simulation concludes.

[0074] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A model-based dynamic anti-saturation method for an aviation engine fuel control system, characterized in that: The steps include: Step 1: Establish a nonlinear component-level model of the aircraft engine and use the Taylor series expansion method to obtain the state space model of the aircraft engine: In the above formula, A p ,B p ,C p ,D p is the coefficient matrix of the state space model, x p (t)=[n H (t) n L (t)] T is the state quantity of the system, where n H (t) is the high pressure compressor rotor speed, n L (t) is the low-pressure compressor rotor speed; u(t) = m f (t) is the control quantity of the system, where m f (t) is the fuel flow rate; y p (t)=[n H (t) n L (t)] T is the measurable output of the system, where n H (t) is the high pressure compressor rotor speed, n L (t) is the low-pressure compressor rotor speed, and t is time; Step 2: Based on the state-space model of the aircraft engine obtained in step 1, establish a linear dynamic controller: In the above formula, A c ,B c ,C c ,D c is the coefficient matrix of the linear dynamic controller of appropriate dimension. In the absence of actuator saturation, the closed-loop system composed of the state space model obtained in step 1 and the linear dynamic control is stable and has the desired closed-loop system performance. c (t) is the state of the controller; when the fuel supply actuator of the aircraft engine is not saturated, u c (t) = y p (t) is the measurable output of the aircraft engine, y c (t) = u(t) is the output signal of the linear dynamic controller, y c (t) is also the actuator input signal when there is no actuator saturation, y t (t) is the high-pressure compressor rotor speed command; Step 3: Design the dynamic anti-saturation compensator for the aircraft engine fuel supply actuator: When the fuel supply actuator of the aircraft engine is not saturated, the linear dynamic controller is used; when the fuel supply actuator is saturated, the dynamic anti-saturation compensator is activated; In the above formula, x aw (t) is the state of the anti-saturation compensator, y aw (t) is the output of the anti-saturation compensator, where u min is the lower limit of the output of the fuel supply actuator, u max The output upper limit of the fuel supply execution structure; A p ,B p ,C p ,D p is the coefficient matrix of the anti-saturation compensator of appropriate dimension.

2. The device of the model-based dynamic anti-saturation method for an aviation engine fuel control system according to claim 1, characterized in that: It includes a personal computer terminal, input and output ports for digital-to-analog conversion, an electronic engine control unit designed based on a digital signal processor for the personal computer terminal, and a data bus converter; The personal computer terminal is used to input command signals in a MATLAB / Simulink environment and to run a component-level aircraft engine model and a mathematical model of a fuel supply actuator as a controlled object; The input and output ports of the digital-to-analog conversion are used to convert the received digital signal into analog signal and vice versa; An electronic engine control unit designed based on a digital signal processor is used to run the model-based dynamic anti-saturation method for the aviation engine fuel control system; The data bus converter is used for signal transmission between the electronic engine control unit designed based on the digital signal processor and the input and output ports of the digital-to-analog converter.

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