Civil aircraft longitudinal gravity center position estimation method based on moment balance

Abstract

The invention relates to a civil aircraft longitudinal gravity center position estimation method based on moment balance, and belongs to the technical field of civil aviation. Aiming at the problem that the aircraft weight and the center-of-gravity position are unobservable, aircraft pneumatic data, engine data and sensor measurement information are comprehensively utilized, the aircraft weight is estimated according to the Newton second law, and an explicit expression of the longitudinal center-of-gravity position of the aircraft is deduced based on a moment balance hypothesis. According to the method, real-time estimation of the weight and the longitudinal center-of-gravity position of the aircraft is realized under the condition that airborne equipment is not added, and accurate input can be provided for core functions of a flight management system such as optimal profile planning and flight path prediction.

Description

Technical Field

[0001] The invention belongs to the field of civil aviation technology, and in particular relates to a method for estimating the longitudinal center of gravity position of a civil aircraft based on moment balance. Background Art

[0002] Weight and center of gravity position are crucial to aircraft design, flight control, flight management and flight safety. They play an important role in stability, controllability and performance, such as climb and cruise performance, take-off and landing performance, flight resistance, trajectory prediction, range, fuel consumption, etc. A favorable center of gravity position can reduce flight resistance and emissions, while an unreasonable center of gravity position may cause a serious degradation of flight quality and even cause an air crash. In addition, the real-time center of gravity position is a necessary condition for realizing active center of gravity control, so as to achieve a reasonable match between the center of gravity and the aerodynamic focus and achieve optimal flight performance. However, the weight and center of gravity position of the aircraft during flight cannot be measured by sensors.

[0003] The present invention is proposed in this context, and provides a solution to the problem that the weight and center of gravity position of civil airliners are unobservable, thereby achieving accurate and real-time estimation of the center of gravity position of the aircraft, and providing reliable input for the function implementation and performance optimization of key airborne systems such as flight control systems and flight management systems. Summary of the invention

[0004] The technical problems to be solved by the present invention are:

[0005] In order to solve the problem that the center of gravity position of civil aircraft is unobservable, the present invention proposes a method for estimating the longitudinal center of gravity position based on moment balance, which comprehensively utilizes aircraft aerodynamic data, engine data and sensor measurement information, and derives the display expression of the aircraft longitudinal center of gravity position from the perspective of moment balance.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A method for estimating the longitudinal center of gravity of a civil aircraft based on moment balance, characterized by comprising:

[0008] Acquire aerodynamic model information, engine model information, navigation parameters, airflow angle, three-axis acceleration measured by accelerometer and accelerometer installation position of the aircraft object; the aerodynamic model information includes aerodynamic lift, aerodynamic drag, aerodynamic side force, aerodynamic rolling moment, aerodynamic pitching moment, aerodynamic yaw moment and aerodynamic moment reference point; the engine model information includes engine thrust; the navigation parameter information includes roll angle rate, pitch angle rate, yaw angle rate; the airflow angle includes angle of attack and sideslip angle;

[0009] Calculate the three-axis acceleration at the center of gravity of the aircraft based on the three-axis acceleration, pitch angular rate, yaw angular rate, and the installation position of the accelerometer;

[0010] Calculate an estimate of the aircraft weight based on the three-axis acceleration at the aircraft's center of gravity, engine thrust, aerodynamic lift, angle of attack, and sideslip angle;

[0011] Based on the pitching moment balance assumption, the pitching moment balance equation is established; based on the pitching moment balance equation, the estimated value of the longitudinal center of gravity position of the aircraft is calculated.

[0012] A further technical solution of the present invention is as follows: In the step of calculating the three-axis acceleration at the center of gravity of the aircraft based on the three-axis acceleration, the pitch angular rate, the yaw angular rate, and the installation position of the accelerometer, the formula used is as follows:

[0013]

[0014] Among them, a x,acc ,a y,acc ,a z,acc is the three-axis acceleration measured by the accelerometer, q is the pitch angular rate, p is the roll angular rate, r is the yaw angular rate, x acc ,y acc ,z acc is the installation position of the accelerometer, and It is the estimated value of the aircraft's center of gravity at the previous moment.

[0015] A further technical solution of the present invention is as follows: In the step of calculating the estimated value of the aircraft weight based on the three-axis acceleration at the center of gravity of the aircraft, the engine thrust, the aerodynamic lift, the angle of attack and the sideslip angle, the formula used is as follows:

[0016]

[0017] Among them, F thrust is the engine thrust, F lift is the aerodynamic lift, is the estimated value of the aircraft weight, α is the angle of attack, and β is the sideslip angle.

[0018] A further technical solution of the present invention is as follows: the pitch moment balance equation is expressed as:

[0019]

[0020] Among them, M B is the aerodynamic pitch moment, F x ,F z is the projection of the total external force on the aircraft on the aircraft coordinate system, x B ,z Bis the position of the aerodynamic torque reference point, It is the estimated coordinate value of the aircraft's center of gravity in the center of gravity coordinate system.

[0021] A further technical solution of the present invention is as follows: the estimated value of the longitudinal center of gravity position of the aircraft is expressed as:

[0022]

[0023] Among them, z0 is the z-axis center of gravity position when the aircraft is empty.

[0024] A computer system, characterized in that it comprises: one or more processors, and a computer-readable storage medium for storing one or more programs, wherein when the one or more programs are executed by the one or more processors, the one or more processors implement the above-mentioned method.

[0025] A computer-readable storage medium, characterized in that it stores computer-executable instructions, which are used to implement the above method when executed.

[0026] A computer program product, characterized by comprising computer executable instructions, wherein the instructions are used to implement the above method when executed.

[0027] The beneficial effects of the present invention are:

[0028] In view of the problem that the center of gravity position of civil aircraft is unobservable, the present invention proposes a method for estimating the longitudinal center of gravity position based on moment balance. Compared with the existing aircraft center of gravity position estimation method, the present invention provides a display expression of aircraft weight and longitudinal center of gravity position information, which can provide more intuitive reference instructions for the crew; in addition, the estimation results of the present invention can provide reliable input for the function realization and performance optimization of key airborne systems such as flight control systems and flight management systems, and further exert aircraft performance on the basis of ensuring flight safety to achieve the best flight quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0030] Figure 1 Schematic diagram of the forces on the plumb surface of an aircraft.

[0031] Figure 2 Schematic diagram of the moments acting on the aircraft.

[0032] Figure 3 Schematic diagram of the center of gravity coordinate system and the body coordinate system.

[0033] Figure 4Aircraft weight and longitudinal center of gravity position estimation results.

[0034] Figure 5 Flow chart of the method of the present invention. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0036] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0037] In order to enable those skilled in the art to better understand the present invention, the present invention is described in detail below in conjunction with specific embodiments.

[0038] Problem description: The initial flight altitude of the aircraft is 3000m, the flight speed is 120m / s, the initial heading is 0°, and the initial center of gravity position is (16.063,0,1.333)m, corresponding to 25%MAC; in addition, in order to verify the effectiveness of the present invention during dynamic flight, the aircraft maintains level flight in the first 500 seconds, starts to climb at the 500th second, with a target altitude of 3500m and an expected center of gravity position of 35%, and starts to descend at the 1000th second, with a target altitude of 2500m and an expected center of gravity position of 30%MAC.

[0039] The specific solutions are:

[0040] Step 1: Load the engine thrust (F thrust ), aerodynamic lift (F lift ), aerodynamic drag (F drag ), aerodynamic side force (F YForce ), aerodynamic rolling moment (L B ), aerodynamic pitch moment (M B), aerodynamic yaw moment (N B ), roll angular rate (p), pitch angular rate (q), yaw angular rate (r), angle of attack (α), sideslip angle (β), and three-axis acceleration measured by the accelerometer (a x,acc ,a y,acc ,a z,acc ), the installation position of the accelerometer (3,0,2.5)m, the position of the aerodynamic torque reference point (16.063,0,0.85)m;

[0041] Step 2: Calculate the three-axis acceleration at the center of gravity of the aircraft The calculation method is:

[0042]

[0043] Step 3: Estimate the aircraft weight, specifically:

[0044] Step 3.1: According to Newton's second law, establish the force equation of the aircraft in the plumb plane:

[0045]

[0046] Step 3.2: Calculate the estimated value of the aircraft weight:

[0047] Step 4: Estimate the longitudinal center of gravity of the aircraft, specifically:

[0048] Step 4.1: Calculate the moment M of the external force on the aircraft relative to the center of gravity of the aircraft G , the calculation method is:

[0049]

[0050] Step 4.2: Based on the pitching moment balance assumption, establish the pitching moment balance equation:

[0051]

[0052] Step 4.3: Calculate the estimated value of the aircraft's longitudinal center of gravity

[0053] Step 5: Repeat steps 1 to 4 to estimate the longitudinal center of gravity position of the aircraft during the entire flight process.

[0054] The effects of this application are described in detail below in conjunction with simulation.

[0055] According to the above steps, the simulation is performed and the estimated result of the center of gravity position of the aircraft is obtained as follows Figure 4As shown in the figure, the mean of the aircraft center of gravity position estimation error is -0.0028% MAC, and the root mean square error is 0.0848% MAC. Combined with the aircraft size information, the aircraft center of gravity position estimation error is within ±0.1m.

[0056] The results show that the method for estimating the center of gravity of a large passenger aircraft based on moment balance proposed in the present invention can achieve accurate and reliable estimation of the center of gravity of the aircraft, and provide a feasible solution to the problem of unobservable center of gravity of civil aircraft.

[0057] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should be included in the protection scope of the present invention.

Claims

1. A method for estimating the longitudinal center of gravity of a civil aircraft based on moment balance, characterized in that: include: Acquire aerodynamic model information, engine model information, navigation parameters, airflow angle, three-axis acceleration measured by accelerometer and accelerometer installation position of the aircraft object; the aerodynamic model information includes aerodynamic lift, aerodynamic drag, aerodynamic side force, aerodynamic rolling moment, aerodynamic pitching moment, aerodynamic yaw moment and aerodynamic moment reference point; the engine model information includes engine thrust; the navigation parameter information includes roll angle rate, pitch angle rate, yaw angle rate; the airflow angle includes angle of attack and sideslip angle; Calculate the three-axis acceleration at the center of gravity of the aircraft based on the three-axis acceleration, pitch angular rate, yaw angular rate, and the installation position of the accelerometer; Calculate an estimate of the aircraft weight based on the three-axis acceleration at the aircraft's center of gravity, engine thrust, aerodynamic lift, angle of attack, and sideslip angle; Based on the pitching moment balance assumption, the pitching moment balance equation is established; based on the pitching moment balance equation, the estimated value of the longitudinal center of gravity position of the aircraft is calculated.

2. The method for estimating the longitudinal center of gravity of a civil aircraft based on moment balance according to claim 1, characterized in that: In the step of calculating the three-axis acceleration at the center of gravity of the aircraft based on the three-axis acceleration, the pitch angular rate, the yaw angular rate, and the installation position of the accelerometer, the formula used is as follows: Among them, a x,acc ,a y,acc ,a z,acc is the three-axis acceleration measured by the accelerometer, q is the pitch angular rate, p is the roll angular rate, r is the yaw angular rate, x acc ,y acc ,z acc is the installation position of the accelerometer, and It is the estimated value of the aircraft's center of gravity at the previous moment.

3. The method for estimating the longitudinal center of gravity of a civil aircraft based on moment balance according to claim 1, characterized in that: In the step of calculating the estimated value of the aircraft weight based on the three-axis acceleration at the center of gravity of the aircraft, the engine thrust, the aerodynamic lift, the angle of attack and the sideslip angle, the formula used is as follows: Among them, F thrust is the engine thrust, F lift is the aerodynamic lift, is the estimated value of the aircraft weight, α is the angle of attack, and β is the sideslip angle.

4. The method for estimating the longitudinal center of gravity of a civil aircraft based on moment balance according to claim 1, characterized in that: The pitching moment balance equation is expressed as: Among them, M B is the aerodynamic pitch moment, F x ,F z is the projection of the total external force on the aircraft on the aircraft coordinate system, x B ,z B is the position of the aerodynamic torque reference point, It is the estimated coordinate value of the aircraft's center of gravity in the center of gravity coordinate system.

5. The method for estimating the longitudinal center of gravity of a civil aircraft based on moment balance according to claim 1, characterized in that: The expression for the estimated value of the longitudinal center of gravity position of the aircraft is: Among them, z0 is the z-axis center of gravity position when the aircraft is empty.

6. A computer system, characterized in that include: One or more processors, and a computer-readable storage medium for storing one or more programs, wherein when the one or more programs are executed by the one or more processors, the one or more processors are enabled to implement the method of claim 1.

7. A computer-readable storage medium, characterized in that Computer executable instructions are stored, and when the instructions are executed, they are used to implement the method of claim 1.

8. A computer program product, characterized in that The invention comprises computer executable instructions, which are used to implement the method of claim 1 when being executed.

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