Method for judging rationality of gravity center of helicopter based on hovering attitude

Abstract

The invention belongs to the overall technical field of helicopters, and relates to a method for judging the rationality of the gravity center of a helicopter based on hovering postures. The method comprises the following steps: collecting multi-dimensional airborne sensor data of a helicopter in a hovering state; key factors which can cause center-of-gravity shift are identified from the multi-dimensional airborne sensor data; according to the key factors, calculating a linear regression model of a takeoff weight point and a pitching angle in a hovering state; and according to the linear regression model, gravity center rationality judgment is performed. The method is suitable for the helicopter in the test flight and delivery user use stage, whether the gravity center of the whole helicopter is within the safety range or not can be rapidly judged, and therefore the test flight and use cost and risk of the helicopter are reduced.

Description

Technical Field

[0001] The invention belongs to the general technical field of helicopters and relates to a method for judging the rationality of the center of gravity of a helicopter based on a hovering posture. Background Art

[0002] A helicopter's flight safety and flight performance are significantly affected by its center of gravity. Flying outside the restricted center of gravity range can lead to increased rotor and flight loads, increased fuselage attitude, decreased maneuverability, and even loss of control. Therefore, it's crucial to assess the appropriateness of the helicopter's center of gravity before flight.

[0003] Currently, before a helicopter test flight, the center of gravity of the entire aircraft is mainly assessed through manual calculation. For example, the center of gravity of the entire aircraft is calculated based on the theoretical or actual weight center of gravity data of the empty aircraft, crew, loading, fuel and other loads, and then it is further determined whether the center of gravity envelope limit will be exceeded during use.

[0004] The shortcomings of the existing technology are: the calculation is complicated and the rationality of the center of gravity cannot be quickly determined; human errors cannot be completely avoided, resulting in calculation errors. Summary of the Invention

[0005] Purpose of the Invention: This method uses data collected during takeoff and hovering at different weights to assess whether a helicopter's center of gravity meets specified limits during operation. This method is applicable to helicopters during test flights and delivery to customers, enabling rapid assessment of whether the helicopter's center of gravity is within a safe range, thereby reducing the costs and risks of flight testing and operation.

[0006] Technical solution:

[0007] A method for determining the rationality of a helicopter's center of gravity based on a hovering attitude is provided, comprising:

[0008] Collect multi-dimensional airborne sensor data of the helicopter in hovering state;

[0009] Identify key factors that can cause center of gravity shift from multi-dimensional airborne sensor data;

[0010] Calculate the linear regression model of takeoff weight point and pitch angle in hover state based on key factors;

[0011] According to the linear regression model, the rationality of the center of gravity is judged.

[0012] Furthermore, the key factors that may cause center of gravity shift are identified from multi-dimensional airborne sensor data, including:

[0013] Identify the center of gravity characteristics of the model and identify the risk points of the center of gravity;

[0014] Based on the helicopter's design features, operating environment, and center of gravity risk points, identify the key factors that may cause center of gravity shift.

[0015] Furthermore, a linear regression model for the takeoff weight center of gravity and the pitch angle in hovering state is calculated based on key factors, including:

[0016] Based on the helicopter's maximum allowable takeoff weight and center of gravity limits, calculate weight and center of gravity data for a series of key takeoff weight points. This weight and center of gravity data includes takeoff weight and center of gravity position of the entire aircraft. These takeoff weight points represent the helicopter's center of gravity position within the center of gravity envelope when fully fueled and empty of fuel. The center of gravity position of the entire aircraft in the fully fueled state is used as the aft limit of the helicopter's center of gravity, while the center of gravity position of the entire aircraft in the empty state is used as the forward limit of the helicopter's center of gravity.

[0017] The aircraft's hovering attitude at each takeoff weight point is calculated using a high-precision helicopter flight dynamics model modified based on test flight data.

[0018] Furthermore, a high-precision helicopter flight dynamics model modified based on test flight data is used to calculate the aircraft hovering attitude at each takeoff weight point, including:

[0019] Establish a high-precision helicopter flight dynamics model and perform full-machine trim;

[0020] According to the takeoff weight at each takeoff weight point, the pitch angle of the helicopter in the hovering state is calculated through the balanced flight force model.

[0021] Furthermore, the linear regression model is:

[0022] θi=aWi+b;

[0023] a and b are regression coefficients; Wi is the takeoff weight at the takeoff weight point; θi is the corresponding pitch angle in the hovering state.

[0024] Furthermore, based on the linear regression model, the rationality of the center of gravity is judged, including:

[0025] The actual take-off weight of the helicopter is read through the onboard weight sensor;

[0026] Calculate the theoretical pitch angle corresponding to the actual takeoff weight based on the linear regression model;

[0027] Get the actual pitch angle of the helicopter in hovering posture;

[0028] Compare the theoretical pitch angle and actual pitch angle corresponding to the actual takeoff weight to determine the rationality of the center of gravity.

[0029] Furthermore, for the case where the center of gravity of the entire aircraft shifts forward as fuel is consumed, the theoretical pitch angle corresponding to the actual takeoff weight is compared with the actual pitch angle to determine the rationality of the center of gravity, including:

[0030] If the actual pitch angle is greater than the theoretical pitch angle, it means that the current center of gravity of the helicopter is further back than the preset center of gravity. As fuel is consumed, the center of gravity of the entire aircraft will not exceed the forward center of gravity limit. The center of gravity of the entire aircraft is properly loaded and will not exceed the center of gravity limit during use.

[0031] If the actual pitch angle = the theoretical pitch angle, it means that the current center of gravity of the helicopter is consistent with the preset center of gravity. As the fuel is consumed, the center of gravity of the entire aircraft will not exceed the center of gravity limit. The center of gravity of the entire aircraft is properly loaded and will not exceed the center of gravity limit during use.

[0032] If the actual pitch angle is less than the theoretical pitch angle, it means that the current center of gravity of the helicopter is forward of the preset center of gravity. As fuel is consumed, there is a risk that the center of gravity of the entire aircraft will exceed the forward limit of the center of gravity. The center of gravity of the entire aircraft is not properly loaded and needs to be readjusted.

[0033] Furthermore, for situations where the aircraft's center of gravity shifts aft as fuel is consumed, the rationality of the center of gravity is determined by comparing the theoretical pitch angle corresponding to the actual takeoff weight with the actual pitch angle, including:

[0034] If the actual pitch angle is greater than the theoretical pitch angle, it means that the current center of gravity of the helicopter is further back than the preset center of gravity. As fuel is consumed, the center of gravity of the entire aircraft will exceed the rear limit of the center of gravity. The center of gravity of the entire aircraft is not properly loaded and needs to be readjusted.

[0035] If the actual pitch angle = the theoretical pitch angle, it means that the current center of gravity of the helicopter is consistent with the preset center of gravity. As the fuel is consumed, the center of gravity of the entire aircraft will not exceed the rear center of gravity limit. The center of gravity of the entire aircraft is properly loaded and will not exceed the center of gravity limit during use.

[0036] If the actual pitch angle is less than the theoretical pitch angle, it means that the current center of gravity of the helicopter is forward of the preset center of gravity. As the fuel is consumed, the center of gravity of the entire aircraft will not exceed the rear limit of the center of gravity. The center of gravity of the entire aircraft is loaded reasonably and will not exceed the center of gravity limit during use.

[0037] Beneficial effects:

[0038] This invention provides a method for assessing the rationality of a helicopter's center of gravity based on its hovering attitude. By combining onboard sensor data with a pre-established attitude-weight relationship model, this method enables rapid and accurate assessment of the helicopter's center of gravity. The method first collects multi-dimensional onboard sensor data while the helicopter is in hover, including but not limited to real-time parameters measured by accelerometers, gyroscopes, altimeters, and other devices. This sensor data is then input into a hovering attitude-based weight analysis system for processing and calculation. This system integrates an attitude-weight relationship model established through extensive experiments and flight tests. Based on the helicopter's current attitude parameters (such as pitch angle) and total weight information, it can rapidly infer the helicopter's overall center of gravity and assess its rationality. Compared to traditional manual measurement or ground-based weighing methods, this technology offers enhanced real-time performance, ease of operation, and wide applicability. It is particularly suitable for helicopter operations in complex environments, effectively improving flight safety and control efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Figure 2 is a graph showing the changes in helicopter weight and longitudinal center of gravity position with fuel consumption.

[0040] Figure 2 The graph shows the relationship between weight and posture at reasonable center of gravity boundaries under different weights. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solutions and advantages of the implementation of this application clearer, the technical solutions in the implementation of this application will be described in more detail below in conjunction with the drawings in the implementation of this application. In the drawings, the same or similar numbers throughout represent the same or similar elements or elements with the same or similar functions. The described implementation is a part of the implementation of this application, not all of the implementations. The implementation described below with reference to the drawings is exemplary and is intended to be used to explain this application, and should not be understood as a limitation on this application. Based on the implementation in this application, all other implementations obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. The implementation of this application is described in detail below in conjunction with the drawings.

[0042] The present invention provides a method for judging the rationality of the center of gravity of a helicopter based on a hovering posture, comprising:

[0043] Step 1: Identification of key factors

[0044] A helicopter's center of gravity (CG) is primarily affected by its empty, loaded, and fueled CGs. CG characteristics vary across different helicopter platforms, so it's important to first identify the CG characteristics of each model and identify CG risk points. Based on the helicopter's design and operating environment, identify the key factors that can cause CG shifts.

[0045] For example:

[0046] like Figure 1 As shown, if the fuel tank is placed behind the center of gravity of the aircraft, the center of gravity of the aircraft will gradually move forward as the fuel is consumed during flight, and there is a risk of exceeding the front limit.

[0047] Uneven mission load distribution: The distribution of loads in different missions may cause the center of gravity to change. For example, if the load is at the center of gravity of the entire aircraft and then unloaded during flight (such as a parachute jump), the center of gravity may exceed the previous limit.

[0048] Equipment installation or removal: The addition or removal of certain equipment during the use of the helicopter may affect the overall center of gravity of the helicopter. Always pay attention to changes in the center of gravity of the helicopter.

[0049] For example, in a Type A helicopter, the fuel tank is located far behind the rotor shaft. After fuel is loaded, the center of gravity of the aircraft is within the center of gravity envelope. However, as fuel is consumed during flight, the center of gravity shifts forward, creating a risk of exceeding the limit in the latter stages of flight. Therefore, fuel consumption is a factor that requires special attention when designing assessment methods.

[0050] Step 2: Calculate the reasonable takeoff weight center of gravity

[0051] Based on the maximum allowable takeoff weight and center of gravity limit range of helicopter A, the takeoff weight Wi and the corresponding longitudinal center of gravity position Xi (i=1, 2, 3...) of a series of key takeoff weight points are calculated; these takeoff weight points represent the center of gravity position of helicopter A in the full fuel state and the empty fuel state, and these weight points are all within the center of gravity envelope. The specific calculation method is as follows:

[0052] 1. According to the design parameters of the helicopter (such as maximum take-off weight, fuel capacity, etc.), determine the weight Wi of a series of reasonable landing weight points 着陆 (Generally, equal gradient weight is used, and the range covers the minimum weight to the maximum weight, such as 6t, 7t, 8t, 9t, ...).

[0053] 2. According to the helicopter center of gravity limit requirements, determine Wi 着陆 The corresponding longitudinal center of gravity position Xi 着陆 Here, the longitudinal center of gravity position can represent the center of gravity position of the entire machine weight.

[0054] 3. According to Wi 着陆 、Xi 着陆 And the fuel weight center of gravity is used to calculate the Wi at takeoff 起飞 He Xi 起飞 .

[0055] For example:

[0056] Type A helicopter parameters:

[0057] The permitted flight weight is between 5.5t and 10t;

[0058] The longitudinal center of gravity limit range is 8.1m to 8.7m;

[0059] The helicopter's fuel weight is 1 ton and its longitudinal center of gravity is 9.8 meters.

[0060] As helicopter A consumes fuel, its center of gravity gradually shifts forward. The risk is that after the fuel is depleted, the center of gravity may exceed the forward boundary of 8.1 meters. Therefore, the forward center of gravity boundaries for landing weight are (6t, 8.1m), (7t, 8.1m), (8t, 8.1m), (9t, 8.1m), and (10t, 8.1m).

[0061] Then calculate the takeoff weight center of gravity based on the landing weight point. Take the landing weight of 6000kg as an example, see Table 1.

[0062] Table 1

[0063] Item weight Weight (t) Longitudinal center of gravity position (m) Remark Landing 6 8.100 fuel 1 9.800 take off 7 8.343 To ensure that the longitudinal center of gravity is greater than 8.100 when landing, the takeoff center of gravity must be greater than 8.343

[0064] The sum of the weights of each item is used to calculate the takeoff weight:

[0065] 6+1=7(t);

[0066] Calculate the center of gravity at takeoff using the moment method:

[0067] (6×8.1+1×9.8)÷7=8.343;

[0068] The corresponding longitudinal center of gravity position at a takeoff weight of 7t is 8.343m.

[0069] Similarly, we can calculate:

[0070] (8t, 8.313m), (9t, 8.289m), (10t, 8.270m).

[0071] Step 3: Calculate the hovering posture and establish a linear regression model

[0072] Using the helicopter flight dynamics model, calculate the aircraft hovering attitude θi (i=1, 2, 3...) at each takeoff weight point. The specific steps are as follows:

[0073] 1. Based on the weight center of gravity data of each weight point Wi, calculate the pitch angle θi of the helicopter in the hovering state.

[0074] 2. Based on the calculated Wi and θi results, establish a linear regression model: θi = aWi + b, where a and b are regression coefficients. Use methods such as the least squares method to fit the optimal values ​​of a and b.

[0075] For example:

[0076] Table 2 is obtained based on the balance calculation of the entire aircraft. The calculation method refers to the balance of the helicopter in hovering in Section 12-3 of "Helicopter Aerodynamics".

[0077] Table 2

[0078] Weight (t) Longitudinal center of gravity position (m) Pitch angle (°) Takeoff weight 1 7t 8.343 4.2 Takeoff weight 2 8t 8.313 3.7 Takeoff weight 3 9t 8.289 3.23 Takeoff weight 4 10t 8.27 2.75

[0079] Linear regression analysis was performed based on Table 2. Figure 2 As shown:

[0080] The regression calculation model is obtained: θi=-0.482Wi+7.567.

[0081] Step 4: Calculate the theoretical pitch angle

[0082] The helicopter takeoff weight W is read by the onboard weight sensor, and the theoretical pitch angle θ is calculated based on the W value and the linear equation θi=aWi+b.

[0083] For example:

[0084] The takeoff weight is 8.6t, and the corresponding pitch angle is calculated as 3.42° based on θi=-0.482Wi+7.567.

[0085] Step 5: Actual posture measurement

[0086] The helicopter's pitch angle β in hovering position is read using the onboard attitude sensor. It should be noted that the sensor data needs to be calibrated and filtered to improve accuracy.

[0087] For example:

[0088] The take-off weight is 8.6t, and the helicopter's hovering attitude angle actually measured by onboard sensors is 3.8°.

[0089] Step 6: Judgment of rationality of center of gravity

[0090] (1) As the center of gravity of the entire aircraft moves forward with fuel consumption, the calculation of the preset center of gravity takes into account the front boundary of the center of gravity:

[0091] If the actual pitch angle is greater than the theoretical pitch angle, it means that the current center of gravity of the helicopter is further back than the preset center of gravity. As fuel is consumed, the center of gravity of the entire aircraft will not exceed the forward center of gravity limit. The center of gravity of the entire aircraft is properly loaded and will not exceed the center of gravity limit during use.

[0092] If the actual pitch angle = the theoretical pitch angle, it means that the current center of gravity of the helicopter is consistent with the preset center of gravity. As the fuel is consumed, the center of gravity of the entire aircraft will not exceed the center of gravity limit. The center of gravity of the entire aircraft is properly loaded and will not exceed the center of gravity limit during use.

[0093] If the actual pitch angle is less than the theoretical pitch angle, it means that the current center of gravity of the helicopter is forward of the preset center of gravity. As the fuel is consumed, the center of gravity of the entire aircraft will exceed the forward limit of the center of gravity. The center of gravity of the entire aircraft is not properly loaded and needs to be readjusted.

[0094] (2) As the aircraft's center of gravity shifts rearward with fuel consumption, the calculation of the preset center of gravity takes into account the rear boundary of the center of gravity:

[0095] If the actual pitch angle is greater than the theoretical pitch angle, it means that the current center of gravity of the helicopter is further back than the preset center of gravity. As fuel is consumed, the center of gravity of the entire aircraft will exceed the rear limit of the center of gravity. The center of gravity of the entire aircraft is not properly loaded and needs to be readjusted.

[0096] If the actual pitch angle = the theoretical pitch angle, it means that the current center of gravity of the helicopter is consistent with the preset center of gravity. As the fuel is consumed, the center of gravity of the entire aircraft will not exceed the rear center of gravity limit. The center of gravity of the entire aircraft is properly loaded and will not exceed the center of gravity limit during use.

[0097] If the actual pitch angle is less than the theoretical pitch angle, it means that the current center of gravity of the helicopter is forward of the preset center of gravity. As the fuel is consumed, the center of gravity of the entire aircraft will not exceed the rear limit of the center of gravity. The center of gravity of the entire aircraft is loaded reasonably and will not exceed the center of gravity limit during use.

[0098] Taking helicopter A as an example, the center of gravity risk point is at the front center of gravity. Compare the β value with the θ value:

[0099] If β>θ, it means that the current center of gravity of the helicopter is further back than the preset center of gravity. As the fuel is consumed, the center of gravity of the entire aircraft will not exceed the front limit of the center of gravity. The center of gravity of the entire aircraft is loaded reasonably and will not exceed the center of gravity limit during use.

[0100] If β=θ, it means that the current center of gravity of the helicopter is consistent with the preset center of gravity. As the fuel is consumed, the center of gravity of the entire aircraft will not exceed the front limit of the center of gravity. The center of gravity of the entire aircraft is loaded reasonably and will not exceed the center of gravity limit during use.

[0101] If β<θ, it means that the current center of gravity of the helicopter is forward of the preset center of gravity. As fuel is consumed, there is a risk that the center of gravity of the entire aircraft will exceed the forward limit of the center of gravity. The center of gravity of the entire aircraft is not properly loaded and needs to be readjusted (such as adjusting the position of the mission payload).

[0102] For example:

[0103] The take-off weight is 8.6t, and the helicopter's hovering attitude angle actually measured by onboard sensors is 3.8°, which is greater than 3.42°.

[0104] It can be judged that when the helicopter's takeoff weight is 8.6t and the hovering attitude is 3.8 degrees, the helicopter's takeoff center of gravity is further back than the preset center of gravity. As the fuel is consumed, the center of gravity moves forward but still does not exceed the center of gravity limit, meeting the mission requirements and allowing takeoff.

[0105] Other embodiments of the present disclosure will readily occur to those skilled in the art after considering the specification and practicing the disclosure herein. This application is intended to cover any variations, uses, or adaptations of the present disclosure that follow the general principles of the present disclosure and include common knowledge or customary techniques in the art not disclosed herein. The description and examples are to be considered as exemplary only, with the true scope and spirit of the present disclosure being indicated by the following claims.

[0106] It should be understood that the present disclosure is not limited to the exact structures that have been described above and shown in the drawings, and that various modifications and changes can be made without departing from the scope thereof. The scope of the present disclosure is limited only by the appended claims.

Claims

1. A method for judging the rationality of a helicopter's center of gravity based on its hovering posture, characterized in that: include: Collect multi-dimensional airborne sensor data of the helicopter in hovering state; Identify key factors that can cause center of gravity shift from multi-dimensional airborne sensor data; Calculate the linear regression model of takeoff weight point and pitch angle in hover state based on key factors; According to the linear regression model, the rationality of the center of gravity is judged.

2. The method according to claim 1, characterized in that Identify key factors that can cause center of gravity shift from multi-dimensional airborne sensor data, including: Identify the center of gravity characteristics of the model and identify the center of gravity risk points; Based on the helicopter's design features, operating environment, and center of gravity risk points, identify the key factors that may cause center of gravity shift.

3. The method according to claim 2, characterized in that Calculate the linear regression model for takeoff weight center of gravity and pitch angle in hover state based on key factors, including: Based on the helicopter's maximum allowable takeoff weight and center of gravity limits, calculate weight and center of gravity data for a series of key takeoff weight points. This weight and center of gravity data includes takeoff weight and center of gravity position of the entire aircraft. These takeoff weight points represent the helicopter's center of gravity position within the center of gravity envelope when fully fueled and empty of fuel. The center of gravity position of the entire aircraft in the fully fueled state is used as the aft limit of the helicopter's center of gravity, while the center of gravity position of the entire aircraft in the empty state is used as the forward limit of the helicopter's center of gravity. The aircraft's hovering attitude at each takeoff weight point is calculated using a high-precision helicopter flight dynamics model modified based on test flight data.

4. The method according to claim 3, characterized in that Using a high-precision helicopter flight dynamics model modified based on test flight data, the aircraft hovering attitude at each takeoff weight point is calculated, including: Establish a high-precision helicopter flight dynamics model and perform full-machine trim; According to the takeoff weight of each takeoff weight point, the pitch angle of the helicopter in the hovering state is calculated through the balanced flight force model.

5. The method according to claim 4, characterized in that The linear regression model is: θi=aWi+b; a and b are regression coefficients; Wi is the takeoff weight at the takeoff weight point; θi is the corresponding pitch angle in the hovering state.

6. The method according to claim 5, characterized in that According to the linear regression model, the rationality of the center of gravity is judged, including: The actual take-off weight of the helicopter is read through the onboard weight sensor; Calculate the theoretical pitch angle corresponding to the actual takeoff weight based on the linear regression model; Get the actual pitch angle of the helicopter in hovering posture; Compare the theoretical pitch angle and actual pitch angle corresponding to the actual takeoff weight to determine the rationality of the center of gravity.

7. The method according to claim 6, characterized in that When the center of gravity of the entire aircraft moves forward as fuel is consumed, compare the theoretical pitch angle corresponding to the actual takeoff weight with the actual pitch angle to determine the rationality of the center of gravity, including: If the actual pitch angle is greater than the theoretical pitch angle, it means that the current center of gravity of the helicopter is further back than the preset center of gravity. As fuel is consumed, the center of gravity of the entire aircraft will not exceed the forward center of gravity limit. The center of gravity of the entire aircraft is properly loaded and will not exceed the center of gravity limit during use. If the actual pitch angle = the theoretical pitch angle, it means that the current center of gravity of the helicopter is consistent with the preset center of gravity. As the fuel is consumed, the center of gravity of the entire aircraft will not exceed the center of gravity limit. The center of gravity of the entire aircraft is properly loaded and will not exceed the center of gravity limit during use. If the actual pitch angle is less than the theoretical pitch angle, it means that the current center of gravity of the helicopter is forward of the preset center of gravity. As fuel is consumed, there is a risk that the center of gravity of the entire aircraft will exceed the forward limit of the center of gravity. The center of gravity of the entire aircraft is not properly loaded and needs to be readjusted.

8. The method according to claim 6, characterized in that When the center of gravity of the entire aircraft shifts aft as fuel is consumed, compare the theoretical pitch angle corresponding to the actual takeoff weight with the actual pitch angle to determine the rationality of the center of gravity, including: If the actual pitch angle is greater than the theoretical pitch angle, it means that the current center of gravity of the helicopter is further back than the preset center of gravity. As fuel is consumed, the center of gravity of the entire aircraft will exceed the rear limit of the center of gravity. The center of gravity of the entire aircraft is not properly loaded and needs to be readjusted. If the actual pitch angle = the theoretical pitch angle, it means that the current center of gravity of the helicopter is consistent with the preset center of gravity. As the fuel is consumed, the center of gravity of the entire aircraft will not exceed the rear center of gravity limit. The center of gravity of the entire aircraft is properly loaded and will not exceed the center of gravity limit during use. If the actual pitch angle is less than the theoretical pitch angle, it means that the current center of gravity of the helicopter is forward of the preset center of gravity. As the fuel is consumed, the center of gravity of the entire aircraft will not exceed the rear limit of the center of gravity. The center of gravity of the entire aircraft is loaded reasonably and will not exceed the center of gravity limit during use.

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