Mixed state-time dependent aero-engine limit protection switching control method

Abstract

The invention belongs to the technical field of aero-engine control, and discloses a mixed state-time dependent aero-engine limit protection switching control method.

Description

Technical Field

[0001] This invention belongs to the field of aero-engine control technology and relates to a hybrid state-time dependent constraint protection switching control method. Background Technology

[0002] As the core power plant of aircraft, the safety and stability of aero-engines directly affect the reliable execution of flight missions. To ensure the safe operation of engines in complex flight environments, modern aero-engines generally employ a limit-protection switching control architecture. For example... Figure 1 As shown, by designing multiple independent controllers for key parameters such as engine speed, turbine outlet temperature, and compressor outlet pressure, and by formulating switching rules between controllers, the engine speed tracking and safety protection functions of the aero-engine can be realized.

[0003] However, traditional switching logic based on Min and Max selection typically prioritizes the most conservative controller output to ensure sufficient safety margin. This strategy, however, can lead to premature controller activation, causing the aero-engine's operation to deviate too far from the designed safety boundaries and reducing its dynamic response performance. While this method can meet safety requirements under normal flight conditions, in emergency situations such as runway incursions or airframe damage, the response speed limitation can negatively impact the aircraft's maneuverability and safety.

[0004] To address the aforementioned issues, this invention proposes a hybrid state-time dependent aero-engine constraint protection switching control method, considering both switching rule design and controller design. This method optimizes switching logic and controller design to achieve smooth switching and efficient control of the engine under different operating modes, balancing safety and the dynamic performance of the control system. A constraint mechanism is introduced based on traditional state-dependent switching rules, ensuring that the control strategy triggers switching only when critical parameters approach safety boundaries, avoiding premature controller switching and reducing system conservatism. Simultaneously, a minimum dwell time switching constraint is innovatively introduced to avoid frequent switching caused by fluctuations in constraint quantities, further improving the engineering reliability of the aero-engine control system. Furthermore, by improving the controller response characteristics, the aero-engine can quickly achieve speed regulation and parameter stabilization under various operating conditions, ensuring safe and reliable operation even under sudden or extreme conditions. Compared with existing technologies, this invention significantly improves the dynamic response capability and safety of the aero-engine control system, reduces the conservatism of the control strategy, and achieves fast, stable, and reliable switching control, demonstrating significant engineering application value and promising prospects for widespread adoption. Summary of the Invention

[0005] To ensure the safety of aero-engine operation and reduce the conservatism of the control system, this invention proposes an improved limiting and protection control method, which is applied to the speed, temperature, and pressure control of aero-turbofan engines.

[0006] The technical solution of the present invention:

[0007] A hybrid state-time dependent control method for switching between limiting and protection functions of an aero-engine, comprising the following steps:

[0008] Step 1: Design of new switching rules;

[0009] The operating mode switching signal of an aero-engine is defined as The control strategy switching signal is defined as follows: and respectively the working mode switching signal and control strategy switching signal Design;

[0010] The operating mode of an aircraft engine depends primarily on the pilot's control of the throttle lever angle; therefore, the operating mode switching signal of an aircraft engine... The design is as follows:

[0011]

[0012] in, , Indicates the angle of the thrust rod. This represents the threshold value for the range of throttle lever angle changes in the i-th operating mode. This indicates the number of operating modes of an aircraft engine.

[0013] Aircraft engine control strategy switching signal The design is as follows:

[0014] 1) Considering the switching mechanism of the Min selector and Max selector in the aircraft engine limit protection control system, define... and ;in, This indicates the output of the speed controller. This indicates the output of a speed controller with an upper limit constraint. The number of speed controllers subject to upper limit constraints. This indicates the output of a speed controller with a lower limit constraint. The number of speed controllers with lower limit constraints; defined and The control strategy switching mechanism under the action of the Min selector and the Max selector is obtained:

[0015]

[0016] 2) To prevent premature activation of the speed limit controller, state-dependent switching constraints are introduced in both the Min and Max selectors. For the speed controller with an upper limit constraint, the following activation condition is designed based on the Min selector:

[0017]

[0018] in, This indicates engine parameters subject to upper limits. yes The corresponding upper limit, Given coefficients, Indicates the control cycle. express Regarding time rate of change, It is a given positive integer;

[0019] For a speed controller with a lower limit constraint, based on the Max selector, the following activation condition is designed:

[0020]

[0021] in, This represents engine parameters subject to lower limit constraints. yes The corresponding upper limit, Given coefficients, It is a given positive integer;

[0022] 3) In the state-dependent control strategy switching rules shown in equations (2)-(6), a dwell time switching constraint is introduced:

[0023]

[0024] in, and These represent control strategy switching signals. The two adjacent switching times, The minimum stay time is set.

[0025] From equations (2) to (7), the control strategy switching signal The final form of expression is:

[0026]

[0027] in, and They are defined as follows:

[0028]

[0029] Step 2: Improve controller design;

[0030] At multiple operating points within the entire operating envelope of the aero-engine, the system dynamics are linearized, and the following switched linear system model is established:

[0031]

[0032] in, Indicates the system status. express The derivative of and These represent the low-pressure rotor speeds, respectively. and high-voltage rotor speed The increment; Indicates the input to the control system. Indicates fuel flow signal The increment; Indicates the system's physical output. , , , All of these are dimension matrices obtained after linearizing the aero-engines;

[0033] Define augmented vectors From equation (11), we obtain the augmented control system:

[0034]

[0035] in, The derivative of the control signal. , and They are defined as follows: ,

[0036] ;

[0037] in, Let represent the identity matrix; based on this, the derivative of the control signal is designed as:

[0038]

[0039] in, Defined as: ;

[0040] and Defined as Represents a symbolic function. Indicates the controller gain. express and its steady-state value The error between them; from equation (11), we get Further, we obtained:

[0041]

[0042] in, Indicates system output The steady-state value; substituting equation (14) into equation (13), we obtain the designed control signal:

[0043]

[0044] in, This represents the control error of the system output. This represents the integrating factor.

[0045] The beneficial effects of this invention are as follows: By designing and optimizing the controller switching conditions, this invention narrows the scope of the limiting controller, reduces engine performance loss caused by premature activation of the limiting controller, introduces minimum dwell time switching constraints to solve the problem of frequent switching caused by fluctuations in the limiting quantity, and improves the dynamic response speed of the aero-engine control system by improving the controller response characteristics. This invention significantly enhances the dynamic response capability and safety of the aero-engine control system, reduces the conservatism of the control strategy, and achieves fast, stable, and reliable switching control. Attached Figure Description

[0046] Figure 1 This is a switching control system for limiting and protecting aircraft engines.

[0047] Figure 2 For switching signals between modes and control strategies (traditional control).

[0048] Figure 3 This is the high-voltage rotor speed curve (traditional control).

[0049] Figure 4 This is the turbine outlet temperature profile (conventional control).

[0050] Figure 5 This is the compressor outlet pressure curve (conventional control).

[0051] Figure 6 For switching signals between modes and control strategies (no dwell time).

[0052] Figure 7 This is the high-voltage rotor speed curve (without dwell time).

[0053] Figure 8 This is the turbine outlet temperature profile (without residence time).

[0054] Figure 9 This is the compressor outlet pressure curve (without residence time).

[0055] Figure 10 The mode and control strategy switching signal obtained by the method of this invention.

[0056] Figure 11 This is the high-voltage rotor speed curve obtained by the method of the present invention.

[0057] Figure 12 This is the turbine outlet temperature curve obtained by the method of the present invention.

[0058] Figure 13 This is the compressor outlet pressure curve obtained by the method of the present invention. Detailed Implementation

[0059] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0060] A hybrid state-time dependent control method for switching between limiting and protection functions of an aero-engine, comprising the following steps:

[0061] Step 1: Design of new switching rules;

[0062] The operating mode switching signal of an aero-engine is defined as The control strategy switching signal is defined as follows: and respectively the working mode switching signal and control strategy switching signal Design;

[0063] The operating mode of an aircraft engine depends primarily on the pilot's control of the throttle lever angle; therefore, the operating mode switching signal of an aircraft engine... The design is as follows:

[0064]

[0065] in, , Indicates the angle of the thrust rod. This represents the threshold value for the range of throttle lever angle changes in the i-th operating mode. This indicates the number of operating modes of an aircraft engine.

[0066] Aircraft engine control strategy switching signal The design is as follows:

[0067] 1) Considering the switching mechanism of the Min selector and Max selector in the aircraft engine limit protection control system, define... ;in, This indicates the output of the speed controller. This indicates the output of a speed controller with an upper limit constraint. The number of speed controllers subject to upper limit constraints. This indicates the output of a speed controller with a lower limit constraint. The number of speed controllers with lower limit constraints; defined and The control strategy switching mechanism under the action of the Min selector and the Max selector is obtained:

[0068]

[0069] 2) To prevent premature activation of the speed limit controller, state-dependent switching constraints are introduced in both the Min and Max selectors. For the speed controller with an upper limit constraint, the following activation condition is designed based on the Min selector:

[0070]

[0071] in, This indicates engine parameters subject to upper limits (such as turbine outlet temperature). yes The corresponding upper limit, Given coefficients, Indicates the control cycle. express Regarding time rate of change, It is a given positive integer;

[0072] For a speed controller with a lower limit constraint, based on the Max selector, the following activation condition is designed:

[0073]

[0074] in, This indicates engine parameters subject to lower limit constraints (such as compressor outlet pressure). yes The corresponding upper limit, Given coefficients, It is a given positive integer;

[0075] Equations (3) and (5) narrow the activation range of the aero-engine limit controller to a smaller area, making the trajectory of the limit quantity and the engine's operation process closer to the safety boundary, thus improving the efficiency of the control system. Based on this, equations (4) and (6) constrain the dynamic switching process of the limit controller, ensuring that the switching process not only meets the designed activation range but also applies constraints to the engine parameters with upper and lower limits respectively. and The prediction process is such that the corresponding limit controller will only be activated when the predicted value exceeds the designed safety boundary. This further narrows the scope of the limit controller and avoids the problem of premature activation of the limit control strategy, which could lead to a loss of aero-engine performance.

[0076] 3) Since the improved switching rules rely on the dynamic changes of the constraint, when engine parameters fluctuate, the control strategy may frequently enter or exit the activation range, resulting in multiple switching of the control strategy within a short period of time. To solve this problem, a dwell time switching constraint is introduced into the state-dependent control strategy switching rules shown in equations (2)-(6):

[0077]

[0078] in, and These represent control strategy switching signals. The two adjacent switching times, The minimum stay time is set.

[0079] From equations (2) to (7), the control strategy switching signal The final form of expression is:

[0080]

[0081] in, and They are defined as follows:

[0082] .

[0083] Step 2: Improve controller design;

[0084] At multiple operating points within the entire operating envelope of the aero-engine, the system dynamics are linearized, and the following switched linear system model is established:

[0085]

[0086] in, Indicates the system status. express The derivative of and These represent the low-pressure rotor speeds, respectively. and high-voltage rotor speed The increment; Indicates the input to the control system. Indicates fuel flow signal The increment; Indicates the system's physical output. , , , All of these are dimension matrices obtained after linearizing the aero-engines;

[0087] Define augmented vectors From equation (11), we obtain the augmented control system:

[0088]

[0089] in, The derivative of the control signal. , and They are defined as follows: , ;

[0090] in, Let represent the identity matrix; based on this, the derivative of the control signal is designed as:

[0091]

[0092] in, Defined as: ;

[0093] and Defined as Represents a symbolic function. Indicates the controller gain. express and its steady-state value The error between them; from equation (11), we get Further, we obtained:

[0094]

[0095] in, Indicates system output The steady-state value; substituting equation (14) into equation (13), we obtain the designed control signal:

[0096]

[0097] in, This represents the control error of the system output. This represents the integrating factor.

[0098] Step 3: Aero-engine simulation experiment;

[0099] For a component-level model of a low-bypass turbofan engine, Two typical operating conditions were selected, and the system output was designed as the incremental speed of the high-voltage rotor. High-pressure turbine outlet temperature and high pressure compressor outlet pressure These correspond to three control strategies: speed, temperature, and pressure, respectively. The control cycle of the control system is set to... The maximum turbine outlet temperature and the minimum compressor outlet pressure are set to 5000 K and 5000 K, respectively. Pa. After normalization, the safety boundary is defined as... Switch rule parameters to , , The controller parameters are designed as follows , , , , , , , .

[0100] Experimental results are as follows Figures 2-13 As shown.

[0101] Experiment 1: For traditional controller design methods;

[0102]

[0103] and traditional control strategy switching rule design methods based on Min and Max.

[0104] ,

[0105] Experimental results are as follows Figures 2-5 As shown in the diagram, under the traditional Min and Max-based limit protection switching control, the engine speed can accurately track the target value, while the selected limits, namely turbine outlet temperature and compressor outlet pressure, effectively operate within the safe range, and the operation process does not exceed the set safety boundaries. and Therefore, traditional limit protection switching control methods can effectively ensure the safety performance of aero engines. However, due to... Figure 4 and Figure 5 It can be seen that there are instances where the limit controller activates prematurely before the limit quantity enters the desired activation region. For example... Figure 4 As shown, at time t=5.8 seconds, the output of the temperature controller is compared between Min and Max, and the final output result is obtained. At the same time, the corresponding temperature limit controller is also activated at t=5.8 seconds. However, due to... Figure 4As can be seen, the corresponding temperature response curve at this point is still some distance from the designed controller activation boundary. Limiting the premature activation of the controller results in a loss of control performance for the aero-engine.

[0106] Experiment 2: To address the issue of premature activation of the controller, the basic Min and Max switching rules were revised based on the traditional controller (16) as follows:

[0107] ,

[0108] in, and The definitions are shown in equations (9) and (10). Based on this, the activation region of the controller is further narrowed, and the constraint is enforced so that the corresponding control strategy will only be activated when the limit quantity enters the designed activation region. Experimental results are as follows: Figures 6-9 As shown. By Figures 7-9 It can be seen that, under the action of the traditional controller (16) and the revised switching rules, the speed response curve of the aero-engine can accurately track the expected value, and the turbine outlet temperature and compressor outlet pressure can also be effectively limited within the safety boundary, ensuring the safe and stable operation of the aero-engine. Furthermore, by Figure 8 and Figure 9 It can be seen that the engine temperature and pressure trajectories corresponding to the activation moment of the limiting controller are both within the designed activation range, effectively solving the engine performance loss problem caused by premature activation of the limiting controller. Correspondingly, in the speed increase phase of Mode 1 and the speed decrease phase of Mode 2, the speed tracking response time of the aero-engine is 4.94 s and 5.9 s, respectively. Compared with Experiment 1, the corresponding speed response times are shortened by 12.1% and 11.4%, respectively. By optimizing the control strategy switching rules and narrowing the activation range of the limiting controller, the dynamic response speed of the aero-engine is effectively improved, and the transient control performance is enhanced. However, due to... Figure 7 It can be seen that, because the optimized switching rules are highly dependent on the dynamic changes in the aircraft engine's limitations, these changes cause the switching rule state to repeatedly change between being satisfied and not satisfied, resulting in frequent controller switching. For example... Figure 7 As shown, the control strategy switched frequently multiple times within a relatively short time interval [5 s, 10 s]. In practical engineering, this high-frequency switching phenomenon can reduce the reliability and stability of the entire control system to some extent, increasing the potential risk of failure.

[0109] Experiment 3: To address the high-frequency controller switching problem present in Experiment 2, firstly, a dwell time switching constraint is introduced into the state-dependent switching rules. The minimum execution time for each control strategy is specified, resulting in the designed hybrid state-time dependent switching rule (8). Next, the proposed nonlinear controller design method (15) is selected, and a nonlinear power function is introduced into the controller design to enhance the dynamic response capability of the control system. The experimental results are as follows Figures 10-13 As shown. By Figures 11-13 It can be seen that the aero-engine's rotational speed response is rapid. In the speed increase phase of Mode 1 and the speed decrease phase of Mode 2, the response times are 3.66 s and 5.54 s, respectively. Compared to Experiment 2, the corresponding speed response times are shortened by 25.9% and 6.1%, respectively, demonstrating the control system's strong dynamic response capability. Figure 12 and Figure 13 It can be seen that the selected limiting variables are all effectively constrained within the specified safety boundaries, fully ensuring the safety performance of the aero-engine. Furthermore, the limiting controllers are all activated within their designed activation regions, and the operation of the limiting quantities closely approximates the designed safety boundaries, effectively guaranteeing the control performance of the aero-engine. Meanwhile, by Figure 10 It can be seen that after adopting the proposed switching rule design method, the control strategy activated each time can maintain operation for a certain duration, effectively solving the problem of frequent switching and improving the overall reliability of the control system.

Claims

1. A hybrid state-time dependent aero-engine limitation and protection switching control method, characterized in that, The steps are as follows: Step 1: Design of new switching rules; The operating mode switching signal of an aero-engine is defined as The control strategy switching signal is defined as follows: and respectively the working mode switching signal and control strategy switching signal Design; Step 2: Improve controller design; At multiple operating points within the entire operating envelope of the aero-engine, the system dynamics are linearized, and the following switched linear system model is established: （11）； in, x = [ Δ N 1 Δ N 2 ] T Indicates the system status. express The derivative, and These represent the low-pressure rotor speeds, respectively. and high-voltage rotor speed The increment; Indicates the input to the control system. Indicates fuel flow signal The increment; Indicates the system's physical output. , , , All of these are dimension matrices obtained after linearizing the aero-engines; Define augmented vectors η = [ x T u T ] T From equation (11), we obtain the augmented control system: （12）； in, The derivative of the control signal. , and They are defined as follows: A ˜ σ = [ A σ B σ 0 0 ] , B ˜ = [ 0 I ] , C ˜ σς = [ C σς D σς ] ; in, Let represent the identity matrix; based on this, the derivative of the control signal is designed as: （13）； in, Defined as: ℓ σ ς = [ 0 0 1 ] ⋅ [ A σ B σ C σ ς D σ ς ] ; and Defined as , , , , Represents a symbolic function. Indicates controller gain. express and its steady-state value The error between them; from equation (11), we get [ x u ] = [ A σ B σ C σ ς D σ ς ] − 1 ⋅ [ x ˙ y ς ] Further, we obtained: （14）； in, Indicates system output The steady-state value; substituting equation (14) into equation (13), we obtain the designed control signal: ，（15）； in, This represents the control error of the system output. This represents the integrating factor.

2. The hybrid state-time dependent aero-engine limitation and protection switching control method according to claim 1, characterized in that, The operating mode of an aircraft engine depends primarily on the pilot's control of the throttle lever angle; therefore, the operating mode switching signal of an aircraft engine... The design is as follows: （1）； in, , Indicates the angle of the thrust rod. This represents the threshold value for the range of throttle lever angle changes in the i-th operating mode. This indicates the number of operating modes of an aircraft engine.

3. The hybrid state-time dependent aero-engine limitation and protection switching control method according to claim 1, characterized in that, Aircraft engine control strategy switching signal The design is as follows: 1) Considering the switching mechanism of the Min selector and Max selector in the aircraft engine limit protection control system, define... and ;in, This indicates the output of the speed controller. , ..., This indicates the output of a speed controller with an upper limit constraint. The number of speed controllers subject to upper limit constraints. , ..., This indicates the output of a speed controller with a lower limit constraint. The number of speed controllers with lower limit constraints; defined and The control strategy switching mechanism under the action of the Min selector and the Max selector is obtained: （2）； 2) To prevent premature activation of the speed limit controller, state-dependent switching constraints are introduced in both the Min and Max selectors. For the speed controller with an upper limit constraint, the following activation condition is designed based on the Min selector: （3）； （4）； in, This indicates engine parameters subject to upper limits. yes The corresponding upper limit, Given coefficients, Indicates the control period. express Regarding time rate of change, It is a given positive integer; For a speed controller with a lower limit constraint, based on the Max selector, the following activation condition is designed: （5）； （6）； in, This represents engine parameters subject to lower limit constraints. yes The corresponding upper limit, Given coefficients, It is a given positive integer; 3) In the state-dependent control strategy switching rules shown in equations (2)-(6), a dwell time switching constraint is introduced: （7）； in, and These represent control strategy switching signals. The two adjacent switching times, The minimum stay time is set. From equations (2) to (7), the control strategy switching signal The final form of expression is: （8）； in, and They are defined as follows: （9）； （10）。

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