Control method for flight level change mode, and automatic flight system

Abstract

A control method for a flight level change mode, and an automatic flight system. The control method comprises: on the basis of a signal acquired from engines regarding whether the engines operate in a dual-engine mode or a single-engine mode, selectively setting respective different vertical speed thresholds during climb and descent processes in a flight level change mode.

Description

Control method of flight level change mode and automatic flight system TECHNICAL FIELD

[0001] The present disclosure relates to the field of automatic flight technology of civil aircraft, and more particularly, to a control method of flight level change mode and an automatic flight system, which can complete aircraft climb and descent under normal double-engine condition (both engines work) and support gliding under single-engine failure condition. BACKGROUND

[0002] The automatic flight system of civil aircraft generally has a flight level change (FLC) mode, also known as an open climb (Open CLB) and open descent (Open Descent) mode in some models. When the mode is activated, the automatic flight system will control the aircraft to maneuver in the pitch direction to ensure that the aircraft speed reaches the target speed selected by the pilot, and at the same time, the mode will also take into account the target altitude selected by the pilot, so that the aircraft can climb or descend towards the target altitude selected by the pilot while maintaining the target speed. In addition, the pilot can set the target altitude and target speed through the human-machine interface device of the automatic flight system, i.e., the flight control panel.

[0003] Under normal double-engine condition (both engines work), the pilot will use the FLC mode of the automatic flight system to achieve climb or descent at the target speed. The climb or descent rate cannot be too slow, otherwise it will affect the flight experience of the pilot. In addition, under single-engine failure condition, the pilot also needs to use the FLC mode to complete single-engine gliding, so that the aircraft height can be as slowly as possible, so as to meet the obstacle clearance requirements of the aircraft.

[0004] Therefore, the FLC mode control algorithm of the automatic flight system must be able to meet the use requirements of both normal double-engine and single-engine failure conditions when designed.

[0005] In the prior art, the FLC mode control law takes the target speed as the control target, but also takes into account the vertical speed (VS) of the aircraft. When the aircraft climbs, the VS is required to be positive, and when the aircraft descends, the VS is required to be negative. In addition, when the absolute value of the VS of the aircraft is greater than a certain threshold, the FLC mode of the automatic flight system will issue a "pitch maneuver command" to make the aircraft track the target speed, and when the absolute value of the VS of the aircraft is less than a certain threshold, the automatic flight FLC mode will issue a "pitch command" to make the aircraft generate the required VS, so as to ensure that the aircraft can climb or descend towards the target altitude.

[0006] In the prior art, the setting of the vertical speed threshold mainly adopts the following two ways.

[0007] (1) Set the vertical speed threshold value to 0

[0008] When the target altitude is greater than the current altitude of the aircraft, the FLC mode prioritizes ensuring that the VS is positive to ensure that the aircraft climbs in altitude, and when the target altitude is less than the current altitude of the aircraft, the FLC mode prioritizes ensuring that the VS is negative to ensure that the aircraft descends in altitude.

[0009] However, if the vertical speed threshold value is set to 0, in the normal twin-engine flight scenario, there will be a situation where the automatic flight system controls the aircraft to maintain the target speed in the pitch maneuver, but (because the VS is small) climbs or descends very slowly, which does not meet the flight operation requirements of civil aircraft. For example, in the process of the target speed being greater than the current speed of the aircraft and the target altitude being greater than the current altitude of the aircraft, i.e., the aircraft needs to increase speed to climb, the automatic flight system may cause the aircraft to maintain a very small VS, which makes the climb very slow and does not meet the actual flight requirements.

[0010] (2) Set the vertical speed threshold value to a certain value (for example, 200 ft / m)

[0011] When the target altitude is greater than the current altitude of the aircraft, the FLC mode prioritizes ensuring that the VS is greater than 200 ft / m, and when the target altitude is less than the current altitude of the aircraft, the FLC mode prioritizes ensuring that the VS is less than -200 ft / m.

[0012] If the vertical speed threshold value is set to a certain value (for example, 200 ft / m), in most normal twin-engine climb or descent scenarios, the absolute value of the VS of the aircraft will be greater than the threshold value, and no particular problem may occur. However, in the single-engine failure glide scenario, the aircraft needs to maintain a given single-engine glide target speed, and the flight altitude of the aircraft needs to descend at the slowest possible descent rate. At this time, the FLC mode of the automatic flight system still prioritizes ensuring that the absolute value of the VS of the aircraft is greater than the threshold value, thereby causing the single-engine failure glide to descend too quickly and not being able to maintain the target speed, thereby not being able to fully play the single-engine glide performance of the aircraft.

[0013] Therefore, how to design a flight altitude layer change mode control method that can ideally change the set value of the vertical speed threshold value in the flight altitude layer change mode according to the requirements of the vertical speed threshold value in different scenarios has become a technical problem to be solved. SUMMARY

[0014] The present disclosure is made to solve the above-mentioned existing problems, and the purpose is to provide a flight altitude layer change mode control method that can ideally change the set value of the vertical speed threshold value in the flight altitude layer change mode according to the requirements of the vertical speed threshold value in different scenarios.

[0015] Another object of the present disclosure is to provide an automatic flight system for implementing a control method of a flight altitude layer change mode.

[0016] To achieve the above object, the present disclosure provides a control method of a flight altitude layer change mode, characterized in that the control method comprises: setting a vertical speed threshold value in a climb and a descent process in the flight altitude layer change mode, respectively, according to a signal about a twin-engine or a single-engine of an engine acquired from the engine.

[0017] Preferably, when the state of the engine is judged as a twin-engine, i.e., both of the engines are in normal operation, the vertical speed threshold value of the aircraft is set according to a relationship between a current altitude of the aircraft and a target altitude acquired from a flight control panel and two altitude threshold values set in advance.

[0018] Preferably, if the current altitude of the aircraft is less than the target altitude, the vertical speed threshold value set at this time for the aircraft is a first climb vertical speed threshold value, and the vertical speed of the aircraft should be greater than the first climb vertical speed threshold value, and if the current altitude of the aircraft is greater than the target altitude, the vertical speed threshold value set at this time for the aircraft is a first descent vertical speed threshold value, and the vertical speed of the aircraft should be less than the first descent vertical speed threshold value.

[0019] Preferably, the first climb vertical speed threshold value is set as a constant value when the current altitude of the aircraft is less than a first altitude threshold value, and is linearly reduced to 0 ft / mm from the constant value within a range of the first altitude threshold value to a second altitude threshold value.

[0020] As an example, the first altitude threshold value is 20000 ft, the second altitude threshold value is 40000 ft, the constant value of the first climb vertical speed threshold value is 250 ft / m, and the first descent vertical speed threshold value is -250 ft / m.

[0021] Preferably, when the state of the engine is judged as a single-engine, i.e., a single engine fails, the vertical speed threshold value of the aircraft is set according to the current altitude of the aircraft and the target altitude acquired from the flight control panel.

[0022] Preferably, if the current altitude of the aircraft is less than the target altitude, the vertical speed threshold value set at this time for the aircraft is a second climb vertical speed threshold value less than the first climb vertical speed threshold value, and if the current altitude of the aircraft is greater than the target altitude, the vertical speed threshold value set at this time for the aircraft is a second descent vertical speed threshold value greater than the first descent vertical speed threshold value.

[0023] As an example, the second climb vertical speed threshold value is 0 ft / m, and the second descent vertical speed threshold value is 0 ft / m.

[0024] Preferably, a compensation value of the vertical speed is calculated and complementary filtered based on a signal related to the vertical speed acquired from an atmospheric system and a signal related to the normal acceleration acquired from an inertial navigation system, and the vertical speed threshold value and the complementary filtered vertical speed are input into the flight level change control law which issues a pitch maneuver command to an external actuator.

[0025] Preferably, the complementary filtering method of the signal related to the vertical speed and the signal related to the normal acceleration is shown in equation (1):

[0026] Another aspect of the present disclosure provides an automatic flight system for implementing the control method of the flight level change mode, characterized in that the automatic flight system has: a threshold setting unit which sets a vertical speed threshold value of an aircraft according to different states of an engine selected from an engine; a compensation calculation unit which calculates a compensation value of the vertical speed according to a signal related to the vertical speed acquired from an atmospheric system and a signal related to the normal acceleration acquired from an inertial navigation system; and a flight level change control law which receives the vertical speed threshold value and the complementary filtered vertical speed and issues a pitch maneuver command to an external actuator.

[0027] According to the above configuration, the control method of the flight level change mode and the automatic flight system for implementing the control method can distinguish between the two-engine and single-engine cases according to different states of the engine, and the automatic flight system adopts different vertical speed threshold values during the climb and descent processes in the flight level change mode, thus ensuring that the flight level change mode can complete the aircraft climb and descent in the normal case (both engines working) and support the glide in the single-engine failure case.

[0028] In addition, according to the above configuration, since the air is thin at high altitudes, the climb ability of the aircraft is lower than that at low altitudes, and therefore the first climb vertical speed threshold value is set to different climb vertical speed threshold values for the climb of the flight level change at different altitudes, and the higher the current flight altitude, the smaller the first climb vertical speed threshold value, thus avoiding the use of an excessively large climb speed threshold value to cause the automatic flight system to control the aircraft to have an excessively large pitch angle at high altitudes, thereby causing an unintended aircraft response.

[0029] Furthermore, according to the above configuration, by comparing the complementary filtered vertical speed VS with the vertical speed threshold value set in the aforementioned manner, the inaccuracy of the vertical speed output by the atmosphere caused by lateral disturbances during single-engine failure can be avoided, and the control performance of the flight level change is further affected. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is a schematic block diagram of an automatic flight system for implementing the control method for changing flight altitude modes of the present disclosure.

[0031] Figure 2 is a graph showing the setting of the vertical speed threshold in the twin-engine climb scenario of the control method for the flight altitude layer change mode shown in Figure 1. Detailed Implementation

[0032] The control method for changing flight altitude mode of the present disclosure will be described in detail below with reference to Figures 1 and 2. Figure 1 is a schematic block diagram showing the implementation of the control method for changing flight altitude mode of the present disclosure, and Figure 2 is a graph showing the setting of the vertical speed threshold during the climb condition in the control method for changing flight altitude mode shown in Figure 1.

[0033] The control method for flight altitude layer change mode disclosed herein can adaptively design different vertical velocity thresholds VSth for the different needs of two scenarios: twin-engine climb / descent and single-engine drift. In particular, considering that the aircraft is susceptible to lateral disturbances in the single-engine case, the vertical velocity VSth after complementary filtering is compared with the vertical velocity threshold VSth.

[0034] More specifically, as shown in Figure 1, the automatic flight system 100, used to implement the control method for changing flight altitude modes of this disclosure, can acquire signals regarding the engine status from the engine 10, signals regarding vertical velocity VS, airspeed, and altitude from the atmospheric system 20, and signals regarding normal acceleration Nz from the inertial navigation system 30. Additionally, the automatic flight system 100 also acquires setpoints for target speed and target altitude from the flight control panel 40.

[0035] In the automatic flight system 100 used to implement the control method for changing flight altitude mode of the present disclosure, there is a threshold setting unit 110 that selectively sets the vertical speed threshold VSth of the aircraft according to the state of the relevant engine.

[0036] When the engine status is determined to be that both engines are working normally, the vertical speed threshold VSth of the aircraft is set according to the relationship between the current altitude of the aircraft, the target altitude, and the two altitude thresholds.

[0037] That is, when the flight altitude layer change mode is activated, the magnitude of the current altitude of the aircraft and the target altitude is determined, if the current altitude of the aircraft is less than the target altitude, the vertical speed threshold VSth set at this time for the aircraft is the first climb vertical speed threshold VScth1, and the vertical speed of the aircraft should be greater than the first climb vertical speed threshold VScth1, otherwise, if the current altitude of the aircraft is greater than the target altitude, the vertical speed threshold VSth set at this time for the aircraft is the first descent vertical speed threshold VSdth1, and the vertical speed of the aircraft should be less than the first descent vertical speed threshold VSdth1.

[0038] In addition, the first climb vertical speed threshold VScth1 is set as shown in FIG. 2, which is a constant value (e.g. 250 ft / m) when the current altitude of the aircraft is less than the first altitude threshold Hth1, and linearly decreases from the constant value (e.g. 250 ft / m) to 0 ft / m within the range of the first altitude threshold Hth1 to the second altitude threshold Hth2.

[0039] On the other hand, when the state of the engine is determined to be a single engine failure condition, the vertical speed threshold of the aircraft is set according to the current altitude of the aircraft and the target altitude.

[0040] That is, when the flight altitude layer change mode is activated, the magnitude of the current altitude of the aircraft and the target altitude is determined, if the current altitude of the aircraft is less than the target altitude, the vertical speed threshold VSth set at this time for the aircraft is the second climb vertical speed threshold VScth2, otherwise, if the current altitude of the aircraft is greater than the target altitude, the vertical speed threshold VSth set at this time for the aircraft is the second descent vertical speed threshold VSdth2.

[0041] As an example, the first altitude threshold Hth1 is 20000 ft, and the second altitude threshold Hth2 is 40000 ft. In addition, the first descent vertical speed threshold VSdth1 is -250 ft / m, and the second climb vertical speed threshold VScth2 and the second descent vertical speed threshold VSdth2 are both 0 ft / m.

[0042] In addition, since the vertical speed signal from the on-board atmospheric system 20 is indirectly measured by measuring atmospheric pressure (static pressure) to measure the change in altitude, when the single engine of the aircraft fails, the lateral side is easily disturbed, causing the value and phase of the vertical speed output by the atmospheric system 20 to be abnormal, at this time, if only the value of the vertical speed output by the atmospheric system 20 is compared with the set vertical speed threshold VS, it will have an adverse effect on the control of the flight altitude layer change mode, therefore, in the automatic flight system 100 for implementing the control method of the flight altitude layer change mode of the present disclosure, as shown in FIG. 1, there is also a compensation calculation part 120 for further calculating the compensation value of the vertical speed VS according to the signal related to the vertical speed VS and the signal related to the normal acceleration Nz.

[0043] Since the inertial navigation system 30 is not easily affected by the outside environment, the signals of the vertical speed VS output by the atmospheric system 20 and the normal acceleration Nz output by the inertial navigation system 30 are subjected to complementary filtering, so as to reduce the influence of single failure.

[0044] The complementary filtering method is shown in formula (1):

[0045] In addition, in the automatic flight system 100, as shown in FIG. 1, the vertical speed VS subjected to complementary filtering and the vertical speed threshold VSth are input into the flight altitude layer changing control law 130, and a pitch maneuver command is issued to the external action part 50 such as the main flight control / elevator by the flight altitude layer changing control law 130.

[0046] According to the above-mentioned configuration, the control method of the flight altitude layer changing mode and the automatic flight system for implementing the control method can distinguish between the double-engine and single-engine cases according to different engine states, and the automatic flight system adopts different vertical speed thresholds VSth in the climbing and descending processes in the flight altitude layer changing mode, respectively, so as to ensure that the flight altitude layer changing mode can complete the climbing and descending of the aircraft in the normal case (both engines are working), and also support the gliding in the single-engine failure case.

[0047] In addition, according to the above-mentioned configuration, since the air is thin at high altitudes, the climbing ability of the aircraft is lower than that at low altitudes, so the first climbing vertical speed threshold VScth1 is set to different climbing vertical speed thresholds for the climbing of the flight altitude layer at different altitudes, and the higher the current flight altitude, the smaller the first climbing vertical speed threshold VScth1, so that the automatic flight system can avoid controlling the aircraft to have a too large pitch angle at high altitudes due to the use of a too large climbing speed threshold, thereby causing an unintended aircraft response.

[0048] In addition, according to the above-mentioned configuration, by comparing the vertical speed VS subjected to complementary filtering with the vertical speed threshold VSth set in the aforementioned manner, the influence of the inaccurate vertical speed output by the atmosphere due to the disturbance in the lateral direction when the single engine fails can be avoided, and the control performance of the flight altitude layer changing can be further affected.

[0049] Other advantages and modifications will be readily apparent to those skilled in the art. The disclosure is not limited to the details and representative embodiments shown and described herein. Therefore, modifications and alterations can be made without departing from the scope and spirit of the general inventive concept as defined by the appended claims and their equivalents.

Claims

1. A control method of a flight altitude layer change mode, characterized by, The control method includes: According to the signal acquired from the engine (10) about the twin-engine or single-engine of the engine (10), the vertical speed threshold (VSth) in the climb and descent process in the flight altitude layer change mode is selectively set.

2. The control method of the flight altitude layer change mode according to claim 1, wherein When the state of the engine is judged as twin-engine, i.e. both engines are normal, the vertical speed threshold (VSth) of the aircraft is set according to the relationship between the current altitude of the aircraft and the target altitude acquired from the flight control panel (40) and the two height thresholds set in advance.

3. The control method of the flight altitude layer change mode according to claim 2, wherein If the current altitude of the aircraft is less than the target altitude, the vertical speed threshold (VSth) set at this time is the first climb vertical speed threshold (VScth1), and the vertical speed (VS) of the aircraft should be greater than the first climb vertical speed threshold (VScth1), If the current altitude of the aircraft is greater than the target altitude, the vertical speed threshold (VSth) set at this time is the first descent vertical speed threshold (VSdth1), and the vertical speed (VS) of the aircraft should be less than the first descent vertical speed threshold (VSdth1).

4. The control method of the flight altitude layer change mode according to claim 3, wherein The first climb vertical speed threshold (VScth1) is set to a constant value when the current altitude of the aircraft is less than the first height threshold (Hth1), and linearly decreases from the constant value to 0 ft / mm within the range of the first height threshold (Hth1) to the second height threshold (Hth2).

5. The control method of the flight altitude layer change mode according to claim 4, wherein The first height threshold (Hth1) is 20000 ft, The second height threshold (Hth2) is 40000 ft, The constant value of the first climb vertical speed threshold (VScth1) is 250 ft / m, The first descent vertical speed threshold (VSdth1) is -250 ft / m.

6. The control method of the flight altitude layer change mode according to claim 3, wherein When the state of the engine is judged as single-engine, i.e. a single engine fails, the vertical speed threshold (VSth) of the aircraft is set according to the current altitude of the aircraft and the target altitude acquired from the flight control panel (40).

7. The control method of the flight altitude layer change mode according to claim 6, wherein If the current altitude of the aircraft is less than the target altitude, the vertical speed threshold (VSth) set at this time is the second climb vertical speed threshold (VScth2) less than the first climb vertical speed threshold (VScth1), If the current altitude of the aircraft is greater than the target altitude, the vertical speed threshold (VSth) set at this time is the second descent vertical speed threshold (VSdth2) less than the first descent vertical speed threshold (VSdth1). If the current altitude of the aircraft is greater than the target altitude, the vertical speed threshold (VSth) set by the aircraft at this time is the second descent vertical speed threshold (VSdth2) which is greater than the first descent vertical speed threshold (VSdth1).

8. The control method of a flight altitude layer change mode according to claim 7, wherein the second climb vertical speed threshold (VScth2) is 0 ft / m, the second descent vertical speed threshold (VSdth2) is 0 ft / m.

9. The control method of a flight altitude layer change mode according to any one of claims 1 to 8, wherein a compensation value of the vertical speed (VS) is calculated and complementary filtered based on a signal relating to the vertical speed (VS) acquired from an atmospheric system (20) and a signal relating to the normal acceleration (Nz) acquired from an inertial navigation system (30), the complementary filtered vertical speed (VS) and the vertical speed threshold (VSth) are input to a flight altitude layer change control law (130) which issues a pitch maneuver command to an external actuator (50).

10. The control method of a flight altitude layer change mode according to claim 9, wherein The complementary filtering method of the vertical speed (VS) signal and the normal acceleration (Nz) signal is shown in equation (1):

11. An automatic flight system for implementing the control method of the flight altitude layer change mode according to any one of claims 1 to 10, characterized in that, the automatic flight system has: a threshold setting section (110) which selectively sets the vertical speed threshold (VSth) of the aircraft depending on the state of the engine (10); a compensation calculation section (120) which calculates a compensation value of the vertical speed (VS) based on a signal relating to the vertical speed (VS) acquired from an atmospheric system (20) and a signal relating to the normal acceleration (Nz) acquired from an inertial navigation system (30); and a flight altitude layer change control law (130) which receives the complementary filtered vertical speed (VS) and the vertical speed threshold (VSth) and issues a pitch maneuver command to an external actuator (50).

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