An automatic flight control method for roll angle holding of a large fixed-wing aircraft

Abstract

The application discloses a kind of automatic flight control methods of large fixed-wing aircraft roll angle keeping, comprising the following steps: S1, receive roll angle instruction and roll angle present value, as the main control signal of aircraft roll angle keeping, while receiving roll angle rate as feedback signal;S2, the roll angle instruction signal on machine is limited in amplitude processing, calculates roll angle instruction value and present roll angle deviation ΔRoll;S3, by absolute value, integral processing, amplitude limiting etc. link to real-time roll angle deviation, obtain roll angle limiting adjustment index Int_ ΔRoll;S4, through proportional link and roll angle speed instruction protection link controller, calculate roll angle rate instruction initial value AP_RollRate;S5, the feedback signal of roll angle rate is as negative feedback, and the difference value of roll angle rate instruction initial value AP_RollRate is calculated, to form roll angle rate instruction value AP_RollRate_cmd;S6, roll angle rate instruction value is substituted into equivalent quasi-fitted low-order system transfer function, forms roll angle rate instruction and is sent to fly-by-wire flight control system.

Description

Technical Field

[0001] This invention belongs to the field of flight control technology, specifically relating to an automatic flight control method for maintaining roll angle of a large fixed-wing aircraft. Background Technology

[0002] Based on the different axes of the aircraft's trajectory and attitude, automatic flight control systems are generally divided into longitudinal and lateral modes. Lateral modes use ailerons (spoilers) and rudder to control the aircraft's direction and horizontal trajectory. Control of the aircraft's horizontal trajectory and heading can be achieved by changing its tilt attitude; therefore, the roll channel control can use attitude angles as the basic loop, with each mode generating tilt attitude angle commands according to control requirements for roll channel control. The rudder channel primarily handles coordinated control during roll axis manipulation.

[0003] Automatic roll hold control technology enables aircraft to track a roll reference value and maintain a certain roll angle during flight. However, existing technologies, both domestically and internationally, suffer from significant overshoot and slow convergence during roll angle adjustment, which negatively impacts the flight quality and passenger comfort of large fixed-wing aircraft. Therefore, it is necessary to improve the control performance of the roll channel, reduce overshoot and adjustment time during roll angle control, enhance the flight quality and passenger comfort of large fixed-wing aircraft, and simultaneously meet the roll angle control requirements for automatic flight control in civil aircraft, complying with the requirements of ICCA CCAR25 and AC 25.1329 regarding aircraft roll angle control in automatic flight control. Summary of the Invention

[0004] This invention provides an automatic flight control method for maintaining roll angle of a large fixed-wing aircraft to solve the above-mentioned problems, comprising the following steps:

[0005] S1. Receive the roll angle command and the current roll angle value as the main control signal for maintaining the aircraft's roll angle, and simultaneously receive the roll angle rate as a feedback signal.

[0006] S2. Limit the received roll angle command signal and calculate the roll angle command value and the current roll angle deviation ΔRoll;

[0007] S3. By using the roll angle deviation limiting regulator, the real-time roll angle deviation is processed through absolute value, integral processing, and amplitude limiting to obtain the roll angle limiting regulation index Int_ΔRoll.

[0008] S4. After passing through the proportional circuit and the roll rate command protection circuit controller, calculate the initial value of the roll rate command AP_;

[0009] S5. The feedback signal of the roll rate is used as negative feedback. The difference between the feedback signal and the initial value of the roll rate command AP_RollRate is calculated, and the limiting protection circuit is set to form the roll rate command value AP_RollRate_cmd.

[0010] S6. Substitute the roll rate command value into the equivalent fitted low-order system transfer function to form a roll rate command, which is then sent to the fly-by-wire flight control system.

[0011] Preferably, the limiting process in step S2 is to keep the upper or lower limit unchanged when the roll angle command exceeds the limit value, until the next command value within the range appears.

[0012] Preferably, the roll angle deviation ΔRoll in step S2 is calculated as follows:

[0013]

[0014] Wherein, ΔRoll is the deviation between the aircraft's current roll angle and the roll angle command value; Rollcmd_deg_u is the upper limit of the roll angle command value limiting function, and Rollcmd_deg_d is the lower limit of the roll angle command value limiting function; Rollcmd_deg is the roll angle command value; and Roll_deg is the current roll angle.

[0015] Preferably, the calculation method for the roll angle limiting adjustment index Int_ΔRoll in step S3 is as follows:

[0016]

[0017] Where Int_ΔRoll is the roll angle deviation limit adjustment index, delta_Roll_u is the upper limit of the roll angle deviation, and delta_Roll_p is the lower limit of the roll angle deviation. For the integral element, k2 is the roll angle deviation control gain adjustment coefficient, used to adjust the system response time.

[0018] Preferably, the initial value of the roll rate command AP_RollRate in step S4 is calculated as follows:

[0019] AP_RollRate=k1·ΔRoll-Int_ΔRoll……………….……[3]

[0020] Wherein, AP_RollRate is the initial value of the aircraft roll rate command; k1 is the roll rate control gain adjustment coefficient, used to adjust the system response time.

[0021] Preferably, the calculation method for the roll rate command value AP_RollRate_cmd in step S5 is as follows:

[0022]

[0023] in, This is a function for limiting the roll rate command value. AP_RollRate_cmd_u is the upper limit of the roll rate command, and AP_RollRate_cmd_d is the lower limit of the roll rate command.

[0024] Preferably, the low-order system transfer function in step S6 is expressed as:

[0025]

[0026] Where T R T s ξ represents the time constant of the roll and helical modes, respectively. nd ω nd τ represents the damping ratio and natural frequency of the Dutch roll mode. φ Indicates the delay time.

[0027] Preferably, the roll mode time constant T R The damping ratio ξ is 1.4 to 3.0. nd The natural frequency ω is between 0.2 and 0.7. nd ≥0.4 and ξ nd ·ω nd ≥0.4.

[0028] The beneficial effects of this invention are as follows:

[0029] Compared with traditional lateral basic mode control, this invention balances adjustment time and improves control accuracy. It uses the roll rate transmitted by the roll rate gyroscope as a feedback signal to assist negative feedback, increase roll damping, optimize the control performance of the aircraft's tilt attitude, and improve the stability of the controlled parameters in the feedback control loop. This provides an optimized basis for improving the lateral automatic control accuracy of large fixed-wing aircraft. Attached Figure Description

[0030] Figure 1 This is the overall control flowchart of the present invention.

[0031] Figure 2 This is a schematic diagram illustrating the principle of the automatic roll angle controller of the present invention.

[0032] Figure 3 This is a schematic diagram of roll angle deviation.

[0033] Figure 4 This is a schematic diagram of the roll angle deviation limiter adjustment in Example 1.

[0034] Figure 5 The diagram shows the roll angle command value for Example 1 and the actual roll angle control effect of the aircraft during flight.

[0035] Figure 6 This is a schematic diagram of the roll angle deviation in Example 2.

[0036] Figure 7 This is a schematic diagram of the roll angle deviation limiter adjustment in Example 2.

[0037] Figure 8 The diagram shows the roll angle command value and the actual roll angle control effect of the aircraft during flight, as shown in Example 2. Detailed Implementation

[0038] The present invention will be further described below with reference to the accompanying drawings and specific embodiments 1 and 2. Obviously, the embodiments described are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. Any obvious improvements, substitutions or modifications made by those skilled in the art without creative effort without departing from the essence of the present invention shall fall within the scope of protection of the present invention.

[0039] See Figure 1 The roll angle command is sent by the onboard flight management system. The current roll angle value is sent by the vertical gyroscope, and the roll rate is sent by the independent roll rate gyroscope. The automatic roll angle controller implements roll angle command control and output. The roll rate command is sent to the fly-by-wire flight control system to control the aileron deflection to achieve horizontal roll angle control of the aircraft, including the following steps:

[0040] S1. Receive the roll angle command and the current roll angle value as the main control signal for maintaining the aircraft's roll angle, and simultaneously receive the roll angle rate as a feedback signal.

[0041] S2. Perform amplitude limiting processing on the received roll angle command signal. When the roll angle command exceeds the limit value, keep the upper or lower limit value unchanged until the next command value within the amplitude appears; calculate the roll angle command value and the current roll angle deviation ΔRoll;

[0042] S3. By using the roll angle deviation limiting regulator, the real-time roll angle deviation is processed through absolute value, integral processing, and amplitude limiting to obtain the roll angle limiting regulation index Int_ΔRoll.

[0043] S4. After passing through the proportional circuit and the roll rate command protection circuit controller, calculate the initial value of the roll rate command AP_RollRate;

[0044] S5. The feedback signal of the roll rate is used as negative feedback. The difference between the feedback signal and the initial value of the roll rate command AP_RollRate is calculated, and the limiting protection circuit is set to form the roll rate command value AP_RollRate_cmd.

[0045] S6. Substitute the roll rate command value into the equivalent fitted low-order system transfer function to form a roll rate command, which is then sent to the fly-by-wire flight control system.

[0046] See Figure 2 The calculation method for the roll angle deviation ΔRoll in step S2 is as follows:

[0047]

[0048] Wherein, ΔRoll is the deviation between the aircraft's current roll angle and the roll angle command value; Rollcmd_deg_u is the upper limit of the roll angle command value limiting function, and Rollcmd_deg_d is the lower limit of the roll angle command value limiting function; Rollcmd_deg is the roll angle command value; and Roll_deg is the current roll angle.

[0049] See Figure 2 The calculation method for the roll angle limiting adjustment index Int_ΔRoll in step S3 is as follows:

[0050]

[0051] Where Int_ΔRoll is the roll angle deviation limit adjustment index, delta_Roll_u is the upper limit of the roll angle deviation, and delta_Roll_p is the lower limit of the roll angle deviation. For the integral element, k2 is the roll angle deviation control gain adjustment coefficient, which is used to adjust the system response time and improve the stability of the aircraft.

[0052] See Figure 2 The initial value of the roll rate command AP_RollRate in step S4 is calculated as follows:

[0053] AP_RollRate=k1·ΔRoll-Int_ΔRoll

[0054] Among them, AP_RollRate is the initial value of the aircraft roll rate command; k1 is the roll rate control gain adjustment coefficient, which is used to adjust the system response time. Together with the roll angle deviation gain adjustment coefficient in the roll angle deviation limit regulator, it improves the system stability.

[0055] See Figure 2The calculation method for the roll rate command value AP_RollRate_cmd in step S5 is as follows:

[0056]

[0057] in, This is a function for limiting the roll rate command value. AP_RollRate_cmd_u is the upper limit of the roll rate command, and AP_RollRate_cmd_d is the lower limit of the roll rate command.

[0058] Example 1:

[0059] See Figure 3 and Figure 4 The lateral control of a certain type of fixed-wing aircraft has the following actual data: aircraft weight 200,000 kg, initial aileron deflection 0°, initial roll angle 0°, and initial roll rate 0 rad·s. -1 The initial altitude is 30,000 ft, the initial Mach number is 0.6, and the maximum roll angle is 25°.

[0060] Given an aircraft roll angle command of 15°, based on the flight characteristics of the aircraft in this example, we can set: Rollcmd_deg_d = -25, Rollcmd_deg_u = 25. After amplitude limiting, the roll angle command is fed into the roll angle control loop.

[0061] The roll angle command value and the current roll angle deviation are calculated, and after the control loop is activated, the roll angle deviation ΔRoll is finally adjusted to approach 0°.

[0062] The roll angle deviation was adjusted using a limiting mechanism. Based on the aircraft characteristics in this example, the upper and lower limits of the roll angle deviation in the limiting mechanism were set to delta_Roll_u = 10 and delta_Roll_p = -10, respectively. In this limiting adjustment, k2 was set to 0.01. The roll angle deviation underwent a 10-second adjustment time in the limiting mechanism, with an overshoot of approximately 3.3°. After one overshoot, the increment of this branch reached a steady state.

[0063] See Figure 5 Roll mode time constant T R The damping ratio ξ is 2.0. nd The natural frequency ω is 0.5. nd It is 0.9, ξ nd ·ω nd=0.45, calculate the initial value of the roll rate and the roll rate command. The instantaneous value upon receiving the command is 3. After the aircraft finally reaches the given roll rate command, the roll rate command approaches 0. In this example, the roll rate control gain adjustment coefficient k1 is set to 0.2. In the limiting protection loop of the roll rate command output, AP_RollRate_cmd_u = 10, AP_RollRate_cmd_p = -10. Simulation tests verify that at 11s, the roll angle deviation is 0.5°, and after 14s, the roll angle error almost completely approaches 0, with the roll angle deviation less than 0.05°.

[0064] Example 2:

[0065] See Figure 6 , Figure 7 and Figure 8 The aircraft weighs 200,000 kg, has an initial aileron deflection of 0°, an initial roll angle of 0°, an initial altitude of 40,000 ft, an initial Mach number of 0.7, and a maximum roll angle deflection of 25°.

[0066] Given an aircraft roll angle of 26°, after boundary control processing by the roll angle initiation module, the aircraft enters the roll angle deviation proportional circuit and roll angle deviation limiting regulator.

[0067] Roll mode time constant T R The damping ratio ξ is 2.5. nd The natural frequency ω is 0.7. nd It is 0.8 and ξ nd ·ω nd =0.56, calculate the roll rate command value AP_RollRate_cmd, the instantaneous value upon receiving the command is 5. After a 17s adjustment period, the roll angle deviation is 0.4°, and after 24s, the roll angle error approaches 0, with the roll angle deviation less than 0.05°.

Claims

1. An automatic flight control method for maintaining roll angle of a large fixed-wing aircraft, characterized in that, Includes the following steps: S1. Receive the roll angle command and the current roll angle value as the main control signal for maintaining the aircraft's roll angle, and simultaneously receive the roll angle rate as a feedback signal. S2. Limit the received roll angle command signal and calculate the limited roll angle command value and the current roll angle deviation. ; S3. By using the roll angle deviation limiting regulator, the real-time roll angle deviation is processed through absolute value, integral, and amplitude limiting steps to obtain the roll angle limiting adjustment index. The calculation method is as follows: in, The roll angle deviation limit adjustment index, This is the upper limit of the roll angle deviation. This is the lower limit of the roll angle deviation. For the points-based system, This is the roll angle deviation control gain adjustment coefficient, used to adjust the system response time; S4. After passing through the proportional circuit and the roll rate command protection circuit controller, the initial value of the roll rate command is calculated. The calculation method is as follows: in, This is the initial value of the aircraft roll rate command; This is the roll rate control gain adjustment coefficient, used to adjust the system response time; S5. Use the roll rate feedback signal as negative feedback, and combine it with the initial value of the roll rate command. The difference is calculated, and the amplitude limiting protection is set to generate the roll rate command value. ; S6. The roll rate command value generated in step S5 is... Substitute the equivalent fourth-order system transfer function into the value, and then generate a new roll rate command value to be sent to the fly-by-wire flight control system.

2. The automatic flight control method for maintaining roll angle of a large fixed-wing aircraft according to claim 1, characterized in that, The limiting process in step S2 is as follows: when the roll angle command exceeds the limit value, the upper or lower limit value remains unchanged until the next command value within the range appears.

3. The automatic flight control method for maintaining roll angle of a large fixed-wing aircraft according to claim 1, characterized in that, The roll angle deviation in step S2 The calculation method is as follows: in, The deviation between the aircraft's current roll angle and the roll angle command value; The function for limiting the roll angle command value. The upper limit value of the limit function for the roll angle command value. The lower limit of the limit function for the roll angle command value. This is the roll angle command value. This is the current roll angle.

4. The automatic flight control method for maintaining roll angle of a large fixed-wing aircraft according to claim 1, characterized in that, The roll rate command value in step S5 The calculation method is as follows: in, The limiting function for the roll rate command value. This is the upper limit of the roll rate command. This is the lower limit of the roll rate command.

5. The automatic flight control method for maintaining roll angle of a large fixed-wing aircraft according to claim 1, characterized in that, The fourth-order system transfer function in step S6 is expressed as: in These represent the time constants for the roll and helical modes, respectively. This represents the damping ratio and natural frequency of the Dutch roll mode. Indicates the delay time.

6. The automatic flight control method for maintaining roll angle of a large fixed-wing aircraft according to claim 5, characterized in that, Roll mode time constant The damping ratio is 1.4 to 3.

0. The natural frequency is 0.2 to 0.

7. ≥0.4 and ≥0.4.

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