An aircraft transient performance optimization method based on feedforward cooperative PID control structure

Abstract

The application discloses a kind of aircraft transient performance optimization methods based on feedforward cooperative PID control structure, belong to flight control technical field.The method provided by the application includes: the aerodynamic dynamic coefficient of aircraft at feature point is calculated;The closed-loop transfer function of aircraft under control at the feature point is calculated;The control system bandwidth is preset;According to the preset control bandwidth, the pole and zero point of the closed-loop transfer function of aircraft stable control loop that needs is configured;According to the closed-loop transfer function and the configured zero pole, control parameter is calculated;According to the control parameter calculated, the control parameter that does not satisfy actual engineering constraint is adjusted.The application aims at the problem that aircraft flight control exists transient performance difficult to meet, by three-loop control plus feedforward control and the pole and zero point of control system configuration, guarantee the stable performance of aircraft flight, improve transient performance under the condition of stable performance, obtain the control parameter that finally satisfies design requirement by preset parameter adjustment and parameter limiting.

Description

Technical Field

[0001] This invention relates to a method for optimizing the transient performance of aircraft based on a feedforward cooperative PID control structure, belonging to the field of aircraft flight control technology. Background Technology

[0002] The design of stable control system parameters for an aircraft refers to the design of reasonable control structure parameters to enable the aircraft to respond smoothly and quickly to commands. The designed control structure parameters need to ensure the system's time-domain response meets the requirements for speed. Therefore, to address the issue of rapid response to flight commands, a transient performance optimization method based on a feedforward cooperative PID control structure is proposed. This method increases the aircraft's stability by designing a three-loop PID control structure, enhances the transient performance of the aircraft's command response by adding a feedforward loop, improves the overall flight control performance by using zero-pole configuration to cancel out pairs of zeros and poles, and achieves stable and rapid control of the aircraft through parameter limiting.

[0003] In control engineering, the PID controller is a commonly used control structure. PID parameter design typically employs empirical formulas, frequency domain analysis, and various optimization algorithms. Empirical formulas rely on experience and trial-and-error to manually adjust controller parameters, requiring a certain understanding of the system and numerous trials, and thus have poor generalizability. Frequency domain analysis involves performing frequency domain analysis on the system's transfer function and using tools such as root locus or Bode plots to design parameters; however, this method struggles to simultaneously consider transient performance. Summary of the Invention

[0004] The technical problem solved by this invention is to overcome the shortcomings of the prior art and provide a method for optimizing the transient performance of aircraft based on a feedforward cooperative PID control structure. In the design process of the aircraft stability control system, a feedforward loop is added to change the composite control loop structure of the aircraft. By limiting the preset parameters, the control parameters are designed so that the control system can improve the transient performance of the response command while meeting the expected indicators, and the aircraft can respond to the command more smoothly and quickly.

[0005] The technical solution of this invention is: a method for optimizing the transient performance of an aircraft based on a feedforward cooperative PID control structure, comprising: Obtain the aerodynamic coefficients of the aircraft at the flight characteristic points to be designed; Determine the feedforward cooperative PID control structure, and calculate the closed-loop transfer function of the feedforward cooperative PID control structure under the control of the aircraft at the flight characteristic point to be designed, based on the aerodynamic coefficient of the flight characteristic point to be designed. Based on the airspace, velocity range, and actuator bandwidth of the flight feature points to be designed, the control system bandwidth is preset; Based on the preset control system bandwidth, configure the expected poles and zeros of the closed-loop transfer function during aircraft stability control; Calculate the control parameters based on the closed-loop transfer function and the desired poles and zeros; Adjust the control parameters that do not meet the actual engineering constraints based on the calculated control parameters.

[0006] Furthermore, obtaining the aerodynamic coefficients of the aircraft at the designed flight characteristic points includes: Based on the speed, altitude, center of mass position, combined angle of attack, and airflow roll angle at the flight characteristic points to be designed, the rudder deflection that satisfies the minimum aerodynamic moment coefficient under the set state is found by allocating different channel rudder deflections, and this state is set as the trim state. Under trim conditions, the aerodynamic coefficients of the aircraft at selected characteristic points are calculated using the small perturbation linearization method and the coefficient freezing method. .

[0007] Furthermore, the projectile dynamics model for calculating the aerodynamic coefficients of the aircraft at selected feature points is as follows: Among them, projectile input To control rudder deflection; missile output Angular velocity, For acceleration. Intermediate state quantity. Representing the angle of attack, Represents the trajectory inclination angle. The derivative representing the trajectory inclination angle, The derivative of angular velocity. For attitude angle, Let be the derivative of the attitude angle. For speed, This represents the aerodynamic coefficient of the aircraft.

[0008] Furthermore, the feedforward cooperative PID control structure includes three control loops: a damping loop, a pseudo-angle of attack feedback loop, and an acceleration feedback loop. The damping loop is used to improve the damping characteristics of the aircraft and stabilize the statically unstable aircraft. The pseudo-angle of attack feedback loop is used to reduce the gain of the damping loop while ensuring the stability of the statically unstable aircraft. The acceleration feedback loop is used to implement the linear transmission from overload command to response.

[0009] Furthermore, the closed-loop transfer function is:

[0010] in, These are preset control parameters. The aerodynamic coefficient of the aircraft. It is the acceleration due to gravity. For the speed of the aircraft This is the integral symbol for the transfer function.

[0011] Furthermore, the preset control system bandwidth includes: taking the control system bandwidth as 1 / 4 to 1 / 5 of the aircraft servo bandwidth.

[0012] Furthermore, the poles are configured as follows: Zero point configuration is ; The desired closed-loop transfer function is:

[0013] in, These are the conjugate dominant poles that determine the transient performance of an aircraft. These are the real and imaginary parts of the dominant pole, where j is the imaginary unit. These are the poles and zeros that are in the same position on the real number line; The method for configuring zeros and poles is as follows:

[0014] In this case, the zero point position is configured as the real pole position. For the configured zero and pole locations, These are the parameters of a second-order inertial element.

[0015] Furthermore, the control parameters include

[0016] in, These are preset control parameters. The aerodynamic coefficient of the aircraft. For the speed of the aircraft The preset control system bandwidth, It is pi (π).

[0017] Furthermore, the limiting processing of the control parameters includes: ; The maximum value of the mechanical constraint for rudder deflection. This represents the maximum mechanical constraint value for rudder deflection speed.

[0018] A computer-readable storage medium storing a computer program, characterized in that, when executed by a processor, the computer program implements the steps of the method for optimizing the transient performance of an aircraft based on a feedforward cooperative PID control structure.

[0019] The advantages of this invention compared to the prior art are: This invention fully considers the desired stability control indexes at the flight characteristic points of the aircraft. By using a zero provided by the forward path of the closed-loop transfer function of the aircraft stability control system to cancel out a pole, it can increase speed without changing the stability margin. The pole configuration takes into account the time-domain and frequency-domain performance of the stability control system, thus releasing the speed of the three-loop PID control structure. This invention can be implemented in software and is easy to implement in engineering. Attached Figure Description

[0020] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 This is a block diagram of the feedforward + PID control structure of the present invention.

[0021] Figure 2 This is a flowchart illustrating the design of the control parameters for this invention. Detailed Implementation

[0022] To better understand the above technical solutions, the technical solutions of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical solutions of the present invention, rather than limitations on the technical solutions of the present invention. In the absence of conflict, the embodiments of the present invention and the technical features in the embodiments can be combined with each other.

[0023] The following description, in conjunction with the accompanying drawings, provides a more detailed explanation of an aircraft transient performance optimization method based on a feedforward cooperative PID control structure, as provided in the embodiments of the present invention. Figure 2 Specific implementation methods may include: Step 1: Calculate the aerodynamic coefficients of the aircraft at the characteristic point using the small perturbation linearization method and the coefficient freezing method.

[0024] The method for calculating the aerodynamic coefficients of the selected feature points is as follows: Based on the velocity, altitude, center of mass position, combined angle of attack, and roll angle at a selected feature point, the rudder deflection that minimizes the aerodynamic moment coefficient under a given state is found by assigning different rudder deflections to different channels. This state is designated as the trim state. Under the trim state, the aerodynamic coefficients of the aircraft at the selected feature point are calculated using the small disturbance linearization method and the coefficient freezing method. .

[0025] Therefore, the projectile dynamics model is:

[0026] Among them, projectile input To control rudder deflection; missile output It's angular velocity. It's acceleration. An intermediate state quantity. Representing the angle of attack, Represents the trajectory inclination angle. The derivative representing the trajectory inclination angle, It is the derivative of angular velocity. It's the attitude angle. It is the derivative of the attitude angle. It's about speed.

[0027] Step 2: Calculate the closed-loop transfer function of the aircraft under control at the flight characteristic point based on the aerodynamic coefficients and composite control structure of the characteristic point to be designed.

[0028] The closed-loop transfer function of the aircraft under control can be determined by the following parameters and control structure: The control structure is a feedforward loop coordinated three-loop control structure. The three-loop control structure consists of a damping loop, a pseudo-angle of attack feedback loop, and an acceleration feedback loop. The damping loop is used to improve the damping characteristics of the aircraft and stabilize the statically unstable aircraft. The pseudo-angle of attack feedback loop is used to reduce the gain of the damping loop while ensuring the stability of the statically unstable aircraft. The acceleration feedback loop is used to implement linear transmission from overload command to response. See the control structure below. Figure 1 Based on the aerodynamic coefficients of the aircraft calculated in step one Preset control parameters Based on the characteristics and states, the closed-loop transfer function of the aircraft under control can be derived.

[0029] The transfer function of the closed-loop system of the aircraft under control is:

[0030] It is the acceleration due to gravity. This refers to the aircraft's flight speed.

[0031] Step 3: Based on the airspace, speed range, and actuator bandwidth of the flight feature points to be designed, preset the control system bandwidth.

[0032] The selection criteria for the preset control system bandwidth are as follows: To ensure the performance requirements of the stable control system design are met by selecting an appropriate design bandwidth, while relaxing the stability control system's ability to respond quickly to commands, the design bandwidth is limited by the servo motor bandwidth of the actuator, and is taken as 1 / 4 to 1 / 5 of the servo motor bandwidth.

[0033] Step 4: Based on the control bandwidth preset in Step 3, configure the poles and zeros of the closed-loop transfer function required for stable aircraft control.

[0034] Regarding the poles of the configuration of the closed-loop transfer function for aircraft stability control: Zero point is : The desired closed-loop transfer function can be expressed as:

[0035] in, These are the conjugate dominant poles that determine the transient performance of an aircraft. These are the real and imaginary parts of the dominant pole, where j is the imaginary unit. These are the poles and zeros that are in the same position on the real number line.

[0036] The zero-pole placement method is as follows:

[0037] In this case, the zero point position is configured as the real pole position. For the configured zero and pole locations, Set it to 4.0. The parameters of a second-order inertial element determine its time-domain response.

[0038] Step 5: Calculate the control parameters based on the closed-loop transfer function from Step 2 and the zeros and poles configured in Step 4.

[0039] The control parameters are calculated as follows:

[0040] Step 6: Based on the control parameters calculated in Step 5, adjust the control parameters that do not meet the actual engineering constraints.

[0041] The method for handling control parameters that do not meet actual engineering constraints is as follows: The control parameters obtained in step five are subjected to amplitude limiting processing, which is limited by the upper limit of the actual control rudder deflection and the rudder deflection speed of the rudder motor. .in, It is the maximum value of the mechanical constraint of the rudder deflection. It is the maximum value of the mechanical constraint on the rudder deflection speed. In the solution provided in the embodiments of the present invention, the control structure block diagram is as follows: Figure 1 As shown, the projectile dynamics model is as follows:

[0042] Among them, projectile input To control rudder deflection; missile output It's angular velocity. It's acceleration. An intermediate state quantity. Representing the angle of attack, Represents the trajectory inclination angle. The derivative representing the trajectory inclination angle, It is the derivative of angular velocity. It's the attitude angle. It is the derivative of the attitude angle. It's about speed.

[0043] The specific workflow is described below: 1. The method for calculating the aerodynamic coefficients of the selected characteristic points in the control system is as follows: Based on the characteristic point's velocity, altitude, combined angle of attack, roll angle, and the location of the aircraft's center of mass, the combined control deflections under that roll angle are iterated to find a set of combined control deflections that minimizes the aircraft's combined aerodynamic moment coefficient. Under this state, small deviations in control deflection and angle of attack are taken to calculate the aerodynamic force and moment coefficients, and the corresponding partial derivatives are obtained. Finally, the dynamic coefficient at that characteristic point is calculated, yielding the dynamic coefficient for a given characteristic point. The speed in this state is .

[0044] 2. The transfer function of the closed-loop system under controlled conditions is: Based on the dynamic coefficients of the aircraft's characteristic points, as well as the preset control parameters and the selected control structure, the transfer function of the controlled closed-loop system of the aircraft can be derived as follows: This is the acceleration due to gravity.

[0045] 3. The preset control bandwidth in fixed-point simulation is: Based on the airspace and velocity domains of the aircraft's flight characteristic points, and substituting them into the control parameter constraint equations, the bandwidth of the aircraft's flight control servo is 15~20Hz. Therefore, the preset control bandwidth is: .

[0046] 4. The zero-pole design required for the stability control index system is as follows: In practical engineering, parameters can become sensitive; being too close to the imaginary axis can lead to instability. Therefore, the canceling poles are selected as... ,in The zero point coincides with this pole, and the other two poles are constrained by parametric equations. 5. The control parameters of the aircraft closed-loop control system are designed as follows: After the zero-pole cancellation configured in step four, the closed-loop system can be equivalent to a typical second-order inertial element. The overshoot of the preset stable control system's step response is no greater than [value missing]. Then, the overshoot calculation formula can be derived from it. ,Pick The control parameters can be determined by the following formula:

[0047] Substituting the preset control bandwidth and canceled zeros and poles, the following control parameters can be obtained. .

[0048] 6. The processing and constraints of control parameters for the aircraft closed-loop control system are as follows: The control parameters calculated in step five may be unsuitable due to preset bandwidth and zero-pole configuration. The control parameters can be recalculated to meet the design requirements by adjusting the preset bandwidth and reconfiguring the zeros and poles.

[0049] Due to limitations in the bandwidth and mechanical constraints of the actual servo motor, the control parameters calculated in step five need to be limited. The servo motor mechanical limit is 30°, and the servo speed limit is 300° / s. Therefore, the parameter limits are:

[0050] This invention consists of an aircraft dynamics system, a controller, and a servo actuator. The control parameters after amplitude limiting are the final design of the controller's characteristic points.

[0051] This invention provides a computer-readable storage medium storing computer instructions that, when executed on a computer, cause the computer to perform... Figure 1 The method described.

[0052] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage and optical storage) containing computer-usable program code.

[0053] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0054] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0055] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0056] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

[0057] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A method for optimizing the transient performance of an aircraft based on a feedforward cooperative PID control structure, characterized in that, include: Obtain the aerodynamic coefficients of the aircraft at the flight characteristic points to be designed; Determine the feedforward cooperative PID control structure, and calculate the closed-loop transfer function of the feedforward cooperative PID control structure under the control of the aircraft at the flight characteristic point to be designed, based on the aerodynamic coefficient of the flight characteristic point to be designed. Based on the airspace, velocity range, and actuator bandwidth of the flight feature points to be designed, the control system bandwidth is preset; Based on the preset control system bandwidth, configure the expected poles and zeros of the closed-loop transfer function during aircraft stability control; Calculate the control parameters based on the closed-loop transfer function and the desired poles and zeros; Adjust the control parameters that do not meet the actual engineering constraints based on the calculated control parameters.

2. The method for optimizing the transient performance of an aircraft based on a feedforward cooperative PID control structure according to claim 1, characterized in that, The aerodynamic coefficients of the aircraft at the designed flight characteristic points include: Based on the speed, altitude, center of mass position, combined angle of attack, and airflow roll angle at the flight characteristic points to be designed, the rudder deflection that satisfies the minimum aerodynamic moment coefficient under the set state is found by allocating different channel rudder deflections, and this state is set as the trim state. Under trim conditions, the aerodynamic coefficients of the aircraft at selected characteristic points are calculated using the small perturbation linearization method and the coefficient freezing method. .

3. The method for optimizing the transient performance of an aircraft based on a feedforward cooperative PID control structure according to claim 2, characterized in that, The projectile dynamics model for calculating the aerodynamic coefficients of the aircraft at selected feature points is as follows: Among them, projectile input To control rudder deflection; missile output Angular velocity, For acceleration, intermediate state quantity Represents the angle of attack. Represents the trajectory inclination angle. The derivative representing the trajectory inclination angle, The derivative of angular velocity. For attitude angle, Let be the derivative of the attitude angle. For speed, This refers to the aerodynamic coefficient of the aircraft.

4. The method for optimizing the transient performance of an aircraft based on a feedforward cooperative PID control structure according to claim 1, characterized in that, The feedforward cooperative PID control structure includes three control loops: a damping loop, a pseudo-angle of attack feedback loop, and an acceleration feedback loop. The damping loop is used to improve the damping characteristics of the aircraft and stabilize the statically unstable aircraft. The pseudo-angle of attack feedback loop is used to reduce the gain of the damping loop while ensuring the stability of the statically unstable aircraft. The acceleration feedback loop is used to implement the linear transmission from overload command to response.

5. The method for optimizing the transient performance of an aircraft based on a feedforward cooperative PID control structure according to claim 1, characterized in that, The closed-loop transfer function is: in, These are preset control parameters. The aerodynamic coefficient of the aircraft. It is the acceleration due to gravity. For the speed of the aircraft This is the integral symbol for the transfer function.

6. The method for optimizing the transient performance of an aircraft based on a feedforward cooperative PID control structure according to claim 1, characterized in that, The preset control system bandwidth includes: taking the control system bandwidth as 1 / 4 to 1 / 5 of the aircraft servo bandwidth.

7. The method for optimizing the transient performance of an aircraft based on a feedforward cooperative PID control structure according to claim 1, characterized in that, The pole configuration is as follows: Zero point configuration is ; The desired closed-loop transfer function is: in, These are the conjugate dominant poles that determine the transient performance of an aircraft. These are the real and imaginary parts of the dominant pole, where j is the imaginary unit. These are the poles and zeros that are in the same position on the real number line; The method for configuring zeros and poles is as follows: In this case, the zero point position is configured as the real pole position. For the configured zero and pole locations, These are the parameters of a second-order inertial element.

8. The method for optimizing the transient performance of an aircraft based on a feedforward cooperative PID control structure according to claim 7, characterized in that, The control parameters include in, These are preset control parameters. The aerodynamic coefficient of the aircraft. For the speed of the aircraft The preset control system bandwidth, It is pi (π).

9. The method for optimizing the transient performance of an aircraft based on a feedforward cooperative PID control structure according to claim 8, characterized in that, Limiting the control parameters includes: ; The maximum value of the mechanical constraint for rudder deflection. This represents the maximum mechanical constraint value for rudder deflection speed.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the method as described in any one of claims 1 to 9.

Images