CN110597281A - A Method for Acquiring Parameters of Automatic Landing Longitudinal Flight Control System - Google Patents

Abstract

The invention discloses a parameter acquisition method of an automatic landing longitudinal flight control system. Firstly, the linear small disturbance model describing the longitudinal movement of the carrier-based aircraft is used as the controlled object, based on the automatic landing of the F/A-18A carrier-based aircraft The longitudinal control law constructs the model of the longitudinal flight control system of the automatic landing, and then combines the system stability theory, the flight data of the F/A-18A carrier aircraft and the optimization method of the control system, aiming at the cascade control system of the longitudinal flight control system of the automatic landing. With the nested loop structure, starting from the pitch rate control loop, the undetermined parameters of the autopilot, the approach power compensation system and the guidance law are calibrated loop by loop from the inside to the outside. The above method is simple and efficient, can make the automatic landing flight control system have good longitudinal maneuverability, and has high practical value.

Description

A Method for Acquiring Parameters of Automatic Landing Longitudinal Flight Control System

technical field

The invention relates to the technical field of aeronautical engineering take-off and landing, in particular to a method for acquiring parameters of an automatic landing longitudinal flight control system.

Background technique

During the landing stage of carrier-based aircraft, the environmental interference factors are complex, but the control accuracy is high, so the pilot operation is very difficult. In order to improve the success rate of landing and reduce the pressure on pilots to perform landing tasks, the U.S. Navy has been researching fully automatic landing technology since the 1950s. Through the Automatic Carrier Landing System (ACLS), the carrier-based aircraft "No manual control, all-weather, fully automatic" recycling. At present, ACLS has been put into actual combat in large quantities and has become one of the most effective tools for assisting carrier-based aircraft to land on the ship. Especially in extreme situations where pilots are not competent (such as heavy fog and dusty weather), ACLS has played an irreplaceable and important role. For example, the AN/SPN-46 system used to ensure the automatic boarding of F-18 and F-35 carrier aircraft, and the UCARS system that guides the automatic recovery of the medium-sized unmanned rotorcraft "Fire Scout".

ACLS is mainly composed of deck motion compensation system and flight control system (Flight Control System, FCS). FCS is divided into shipboard system and airborne system: the shipboard part is responsible for solving the automatic landing guidance law, and the airborne part is divided into In order to control the stability augmentation system (Control Augmentation System, CAS), that is, the autopilot, and the approach power compensation system (Approach Power Compensation System, APCS). In order for the carrier-based aircraft to eliminate the approach trajectory error as soon as possible and accurately track the commanded glide slope, ACLS must have good longitudinal maneuverability, and the longitudinal FCS parameter is the key to restricting the realization of this performance. However, in the prior art, since the automatic landing longitudinal FCS has a cascaded nested multi-feedback loop structure, there are many undetermined parameters, and it is very inefficient to adjust these parameters by using the traditional root locus correction method or by trial and error purely based on engineering experience .

Contents of the invention

The object of the present invention is to provide a method for obtaining parameters of an automatic landing longitudinal flight control system, which is simple and efficient, enables the automatic landing flight control system to have good longitudinal maneuverability, and has high practical value.

The purpose of the present invention is achieved through the following technical solutions:

A method for obtaining parameters of an automatic landing longitudinal flight control system, the method comprising the following steps:

Step 1. Taking the linear small disturbance model describing the longitudinal motion of the carrier-based aircraft as the controlled object, the automatic landing longitudinal flight control system model is constructed based on the longitudinal control law of the F/A-18A carrier-based aircraft's automatic landing;

Step 2. According to the accuracy requirements of carrier-based aircraft landing control and referring to the test results of the automatic landing performance of the F/A-18A carrier-based aircraft, set the automatic landing longitudinal flight control system parameter correction target;

Step 3, calculate the transfer function of the pitch rate control loop based on the constructed model, and narrow the value range of the pitch rate control loop parameters K _Q , _KI and K _P according to the stability criterion in the control theory;

Step 4. Optimize the step response of the pitch rate control loop to the angular rate command with an amplitude of 0.01rad, and stop when the optimization result is close to the performance test of the pitch rate control loop of the F/A-18A carrier aircraft automatic landing Optimize to obtain the parameters of the pitch rate control loop;

Step 5, fix the parameter correction results obtained in step 4, take the vertical velocity response performance of the F/A-18A carrier-based aircraft as the optimization goal, and correct the autopilot by optimizing the step response of the autopilot to the altitude change rate deviation command Parameters to be determined in the instrument;

Step 6, fix the parameter correction results obtained in steps 4 and 5, and correct the APCS parameters of the approach power compensation system, mainly to adjust the two control gains of K _e and K _αP ;

Step 7. Fix the parameter correction result obtained in step 6, then proceed to step 5, and then repeat the operations of steps 6 and 5 until the response of the altitude change rate and angle of attack both reach the parameter correction target;

Step 8, fix the parameter correction result obtained in step 7, and correct the guidance law parameter K _H by optimizing the step response of the approach height of the carrier aircraft.

It can be seen from the above-mentioned technical solution provided by the present invention that the above-mentioned method is simple and efficient, can make the automatic landing flight control system have good longitudinal maneuverability, and has high practical value.

Description of drawings

In order to illustrate the technical solutions of the embodiments of the present invention more clearly, the drawings that need to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. Those of ordinary skill in the art can also obtain other drawings based on these drawings on the premise of not paying creative work.

Fig. 1 is a schematic flowchart of a method for acquiring parameters of an automatic landing longitudinal flight control system provided by an embodiment of the present invention;

Fig. 2 is a schematic diagram of the simulation result after all the internal loop parameters of the automatic landing longitudinal flight control system of the example of the present invention are acquired.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

The embodiment of the present invention will be further described in detail below in conjunction with the accompanying drawings. As shown in FIG. 1, it is a schematic flowchart of a method for obtaining parameters of an automatic landing flight control system provided by an embodiment of the present invention. The method includes:

Step 1. Taking the linear small disturbance model describing the longitudinal motion of the carrier-based aircraft as the controlled object, the automatic landing longitudinal flight control system model is constructed based on the longitudinal control law of the F/A-18A carrier-based aircraft's automatic landing;

In this step, the linear small disturbance model that can describe the longitudinal motion of the carrier-based aircraft is used as the controlled object, and its expression is:

in:

x=[Δv _I Δα _I Δq Δθ Δh] ^T , u=[Δδ _e Δδ _c Δδ _p ] ^T , v _I means ground speed, that is, inertial speed, m/s; α _I means ground speed angle of attack or inertial angle of attack, rad; q means pitch angular velocity, rad/s; θ means pitch angle, rad; h means height, m ; n _z represents the normal overload, g; γ represents the track angle, rad; the three components in the control vector u represent the disturbance of the elevator deflection angle, the canard deflection angle and the effective throttle opening in turn, and the unit is °; Δ represents the deviation between the physical quantity and its reference value (nominal value), and the subscript "*" represents the reference value (nominal value) of the variable, such as v _I* = 70m/s, the same below; the constant value matrix AF, specifically as Table 1 shows:

The longitudinal flight control law of F/A-18A carrier-based aircraft automatic landing is composed of three parts: autopilot, approach power compensation system (APCS) and outer loop guidance law. The autopilot control law includes the pitch rate control loop. The APCS of the F/A-18A adopts the throttle control strategy of maintaining a constant angle of attack. After properly simplifying the throttle control law of the F/A-18A carrier-based aircraft in the prior art, the expression of the APCS control law is obtained as follows:

In the formula, δ _ec is the elevator pitch command, and K _αP , K _αI , _Ke , K _q , K _nz are control gains.

In addition, since the F/A-18A carrier-based aircraft uses the rate of change of approach altitude as the direct control state of the autopilot, considering that the speed of the carrier-based aircraft remains basically unchanged during the landing stage, the The disturbance expression (3) shows that the control Equivalent to control γ. In order to improve the system damping, it is also necessary to control the vertical acceleration (normal overload) of the carrier aircraft.

Table 1 Coefficient matrix A-F of carrier-based aircraft linear motion model

Step 2. According to the accuracy requirements of carrier-based aircraft landing control and referring to the test results of the automatic landing performance of the F/A-18A carrier-based aircraft, set the automatic landing longitudinal flight control system parameter correction target;

In the specific implementation, the set calibration goals are shown in Table 2 below;

Table 2 System parameter calibration target

Step 3, calculate the transfer function of the pitch rate control loop based on the constructed model, and narrow the value range of the pitch rate control loop parameters K _Q , _KI and K _P according to the stability criterion in the control theory;

In this step, the control gain K _Q is connected in series with the lag-lead filter (the parameters are T ₁ and T ₂ , and T ₁ > T ₂ ), both of which are in the pitch rate feedback loop, and K _I and K _P are the integral gain and proportional gain of the forward channel transfer function of the pitch rate control loop, respectively.

Step 4. Optimize the step response of the pitch rate control loop to the angular rate command with an amplitude of 0.01rad. When the optimization result is similar to the performance test of the pitch rate control loop for the automatic landing of the F/A-18A carrier aircraft, the optimization can be stopped , to obtain the parameters of the pitch rate control loop;

Before optimization, the parameter value range should be selected according to the calculation results of step 3, and the performance index of the step response should be set as follows: the adjustment time is not greater than 3s, the steady-state error is 1%, and the overshoot is less than 200%;

After performing this step, the parameters of the obtained pitch rate control loop are:

K _Q =1.174 K _I =522.268 K _P =362.242 T ₁ =1.766 T ₂ =0.766

Step 5, fix the parameter correction results obtained in step 4, take the vertical velocity response performance of the F/A-18A carrier-based aircraft as the optimization goal, and correct the autopilot by optimizing the step response of the autopilot to the altitude change rate deviation command Parameters to be determined in the instrument;

In this step, the parameters of the autopilot need to be corrected and They are respectively in the carrier aircraft track angle feedback and normal overload feedback loop; the correction method is similar to the previous two steps, first calculate The transfer function of the response, according to the stability criterion in the control theory, narrows the value range of the undetermined parameters, and then sets the step performance indicators such as the overshoot within 15%, the adjustment time of 4.5s, and the steady-state error of 1% to optimize the automatic Pilot step response to altitude rate deviation command.

Step 6, fixing the parameter correction results obtained in steps 4 and 5, correcting the APCS parameters of the approach power compensation system, mainly adjusting the two control gain parameters K _e and K _αP ;

In this step, according to the angle of attack control capability of the F/A-18A carrier-based aircraft in the landing phase, the correction target is set as: the time for the carrier-based aircraft to return to the nominal value after the angle of attack of the carrier-based aircraft responds to the step command of the altitude change rate Not more than 5s;

All the parameters that need to be corrected in this step are given by formula (2). According to the relationship formula (4) between the attack angle disturbance Δα, track angle disturbance Δγ and pitch angle disturbance Δθ of the carrier-based aircraft, the previous parameter correction process cannot To ensure that Δα converges to 0, and it is impossible to use conventional indicators to define the step response of Δα to the deviation command of the altitude change rate, and to take into account the high-order properties of the control system, it is difficult to optimize the APCS parameters with the help of software tools or theoretical calculations, which can be based on The empirical debugging is completed, mainly to adjust the two control gains of K _e and K _αP .

Δθ=Δα+Δγ (4)

In addition, due to the coupling between the control loops of the system, this step is likely to reduce the parameter correction effect of step 5, that is, it will have a negative impact on the vertical velocity response performance of the carrier aircraft.

Step 7. Fix the parameter correction result obtained in step 6, then proceed to step 5, and then repeat the operations of steps 6 and 5 until the response of the altitude change rate and angle of attack both reach the parameter correction target;

This step is mainly to improve the comprehensive control effect of the system on the altitude change rate and angle of attack. When the angle of attack response meets the requirements, fix the APCS parameters obtained in step 6, and then use step 5 to optimize the parameters and Then fix the autopilot parameters and adjust the APCS parameters again... In this way, repeat the operations of steps 5 and 6 several times to complete the design of all parameters in the inner loop of the automatic landing longitudinal flight control system, so that the altitude change rate of the carrier aircraft and the response The corner responses all meet the parameter calibration objectives.

For example, the parameter correction results of this step are as follows, and the corresponding simulation results are shown in Figure 2. Obviously, after this step is executed, the response of the system to the altitude change rate command is better than that of the F/A-18A carrier-based aircraft Test Results.

K _q =120K _e =4K _αI =40K _αP =−95K _nz =20.

Step 8, fix the parameter correction result obtained in step 7, and correct the guidance law parameter K _H by optimizing the step response of the approach height of the carrier aircraft.

In this step, according to the general requirements of carrier-based aircraft landing trajectory correction, the step response performance index is selected to be within 3% of the overshoot, the adjustment time is not greater than 8s, and the steady-state error is within 1%, and the state response is comprehensively considered. Overshoot and adjustment time to finally determine the guiding law parameters. After performing this step, the parameter correction results shown in Table 3 are obtained:

Table 3 Guidance law parameter correction results

It should be noted that the content not described in detail in the embodiments of the present invention belongs to the prior art known to those skilled in the art.

In summary, the method described in the embodiment of the present invention has the following advantages:

(1) According to the general requirements of carrier-based aircraft landing control and the actual measurement data of the F/A-18A carrier-based aircraft's automatic landing system to the command response, the parameter correction target is quantified, which improves the efficiency of parameter correction and the practicality of parameter design results sex;

(2) The value range of undetermined parameters is narrowed by the stability criterion in the automatic control theory, which greatly saves the workload of parameter correction and improves the efficiency of parameter correction.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person familiar with the technical field can easily conceive of changes or changes within the technical scope disclosed in the present invention. Replacement should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims.

Claims (6)

1. A method for acquiring parameters of an automatic landing longitudinal flight control system is characterized by comprising the following steps:

step 1, taking a linear small disturbance model describing carrier landing longitudinal motion of a carrier-based aircraft as a controlled object, and constructing an automatic carrier landing longitudinal flight control system model based on an F/A-18A carrier-based aircraft automatic carrier landing longitudinal control law;

step 2, setting a parameter correction target of an automatic carrier landing longitudinal flight control system according to the precision requirement of carrier landing control of the carrier-based aircraft and by referring to an F/A-18A carrier-based aircraft automatic carrier landing performance test result;

step 3, calculating a transfer function of the pitch angle rate control loop based on the constructed model, and reducing a pitch angle rate control loop parameter K according to a stability criterion in a control theory_Q、K_IAnd K_PThe value range of (a);

step 4, optimizing the step response of the pitch angle rate control loop to the amplitude 0.01rad angle rate instruction, and stopping optimization when the optimization result is close to the performance test condition of the F/A-18A carrier-based aircraft automatic landing pitch angle rate control loop to obtain the parameters of the pitch angle rate control loop;

step 5, fixing the parameter correction result obtained in the step 4, taking the vertical speed response performance of the F/A-18A carrier aircraft landing stage as an optimization target, and correcting undetermined parameters in the autopilot through optimizing the step response of the autopilot to the high-degree change rate deviation instruction;

step 6, fixing step 4, and step 5The obtained parameter correction result is used for correcting the APCS parameter of the approach power compensation system, mainly adjusting K_eAnd K_αPTwo control gains;

step 7, fixing the parameter correction result obtained in the step 6, then performing the step 5, and then repeating the operations of the steps 6 and 5 until the response of the altitude change rate and the response of the attack angle reach the parameter correction target;

and 8, fixing the parameter correction result obtained in the step 7, and correcting the guidance law parameter K by optimizing the step response of the approach height of the carrier-based aircraft_H。

2. The parameter acquisition method of the automatic carrier landing longitudinal flight control system according to claim 1, wherein in step 1, the taking of the linear small disturbance model describing the carrier aircraft landing longitudinal motion as the controlled object specifically comprises:

a linear small disturbance model capable of describing the carrier landing longitudinal motion of a carrier-based aircraft is adopted as a controlled object, and the expression is as follows:

wherein:

x＝[Δv_I Δα_I Δq Δθ Δh]^T，u＝[Δδ_e Δδ_c Δδ_p]^T，v_Ito represent

The ground speed; alpha is alpha_IRepresenting the ground speed attack angle or inertial attack angle; q represents a pitch angular velocity; θ represents a pitch angle; h represents height; n is_zIndicating a normal overload; gamma represents the track angle; 3 components in the control vector u sequentially represent disturbance quantities of elevator deflection, canard wing deflection and effective accelerator opening; Δ represents the deviation of the physical quantity from its reference value, and the subscript "-" represents the reference value of the variable; the matrices a-F are all constant value matrices.

3. The parameter acquisition method of the automatic landing longitudinal flight control system according to claim 1, wherein in step 1, an outer loop of the F/a-18A carrier-based aircraft automatic landing longitudinal control law is a guidance law, and an inner loop comprises an autopilot and an Approach Power Compensation System (APCS), wherein the autopilot comprises a pitch angle rate control loop;

the expression of the APCS control law is as follows:

in the formula, delta_ecA pitch instruction for the elevator; k_αP、K_αI、K_e、K_q、K_nzAre all control gains.

4. The parameter acquisition method of the automatic landing longitudinal flight control system according to claim 1, wherein in step 4, before optimization, a parameter value range is selected according to the calculation result of step 3, and the performance index of the step response is set as: the adjusting time is not more than 3s, the steady-state error is 1%, and the overshoot is less than 200%.

5. The parameter acquisition method of the automatic carrier landing longitudinal flight control system according to claim 1, wherein in step 6, according to the attack angle control capability of the F/a-18A carrier aircraft in a carrier landing stage, a correction target is set as follows: the time for the attack angle of the carrier-based aircraft to return to the nominal value after responding to the high-degree change rate step command does not exceed 5 s.

6. The parameter acquisition method of the automatic landing longitudinal flight control system according to claim 1, wherein in step 8, according to the general requirement of carrier aircraft landing trajectory deviation correction, the step response performance index is selected to be within 3% of overshoot, the adjustment time is not more than 8s, and the steady-state error is within 1%, and the overshoot and the adjustment time of the state response are comprehensively considered to finally determine the guidance law parameter K_H。