Helicopter rotor rotating speed correction control law design method

Abstract

The invention belongs to the technical field of overall design of helicopters, and particularly relates to a helicopter rotor rotating speed correction control law design method. Comprising the following steps: S1, acquiring static pressure and external atmospheric temperature, and calculating relative atmospheric density; calculating a corrected rotor speed omega1 based on the atmospheric density and the vacuum speed; s2, correcting the rotating speed of the rotor wing based on the rotating speed adjustment amplitude in the hovering state to obtain an unlimited corrected rotating speed omega2; s3, according to the adjusting range of the rotating speed of the rotor wing, calculating a corrected rotating speed omega3 considering boundary limitation; and S4, according to the rotor rotating speed change rate limitation, calculating to obtain the rotor target rotating speed omega of the current time step.

Description

Technical Field

[0001] The invention belongs to the technical field of overall helicopter design, and in particular relates to a helicopter rotor speed correction control law design method. Background Art

[0002] For helicopters of conventional configuration, the rotor is the main source of lift, and the rotor speed is an important parameter in helicopter design. Usually, the rotor speed of a helicopter is fixed, but during the flight of a helicopter, the atmospheric environment and flight conditions are constantly changing. If the rotor speed can be adjusted within a certain range according to the atmospheric environment and flight conditions, it will effectively improve the helicopter rotor capability and environmental adaptability. When flying at high altitudes, due to the low air density, appropriately increasing the rotor speed can avoid a reduction in lift and improve the helicopter's capabilities. When flying at low altitudes, the rotor speed can be appropriately reduced, which can effectively reduce noise. At the same time, when flying at high speeds, the forward blade shock wave can also be effectively avoided by reducing the speed. Summary of the invention

[0003] The purpose of the present invention is to design a helicopter rotor speed correction control law design method, based on atmospheric density compensation and flight state correction, to adjust the helicopter rotor speed within a certain range, thereby compensating the lift of the rotor at high altitude, reducing low-altitude noise, and improving the helicopter's flight capability.

[0004] In order to achieve the above object, the present invention adopts the following technical solution to achieve it.

[0005] A method for designing a helicopter rotor speed correction control law, the method comprising:

[0006] S1, obtains static pressure and external atmospheric temperature, calculates relative atmospheric density; calculates corrected rotor speed Ω1 based on atmospheric density and true air speed;

[0007] S2, correcting the rotor speed based on the speed adjustment amplitude in the hovering state to obtain an unlimited corrected speed Ω2;

[0008] S3, according to the adjustment range of the rotor speed, calculate the modified speed Ω3 considering the boundary limit;

[0009] S4, according to the rotor speed change rate limit, calculate the rotor target speed Ω of the current time step.

[0010] Furthermore,

[0011] S1, obtain static pressure and external atmospheric temperature, and calculate relative atmospheric density, specifically:

[0012] C ρ =288.15 / (273.15+T)×(P / 1013.25)

[0013] Among them, C ρ It represents the relative atmospheric density, T represents the measured external atmospheric temperature, unit: °C, and P represents the measured static pressure, unit: hPa.

[0014] Furthermore,

[0015] S1, the method for calculating the corrected rotor speed Ω1 is specifically as follows:

[0016] Corrected rotor speed Ω1:

[0017] Where, Ω0 represents the reference rotor speed, Ω V min Indicates the corrected speed under low speed conditions, Ω V max Indicates the corrected speed under high speed conditions, C V Indicates the true airspeed conversion factor.

[0018] Furthermore,

[0019] True air speed conversion factor C V The value of is:

[0020] C V =0(V <V min )

[0021] C V =(VV min ) / (V max -V min )(V min ≤V≤V max )

[0022] C V =1(V>V max )

[0023] Where V represents true airspeed, V min Indicates the minimum critical speed for speed correction, V max Indicates the maximum critical speed for speed correction.

[0024] Furthermore,

[0025] In S2, the unlimited corrected speed Ω2 is calculated as:

[0026] Ω2=Ω1+ΔΩ hover ×(1-C V )

[0027] Where ΔΩ hover Indicates the speed adjustment amplitude in the hovering state.

[0028] Furthermore,

[0029] The modified speed Ω3 calculated in S3 considering the boundary limit is specifically:

[0030] Ω3=MIN[MAX(Ω2,Ω min ),Ω max ]

[0031] Among them, MIN(a,b) means the smaller value between a and b, MAX(a,b) means the larger value between a and b, Ω min Indicates the lower limit of the speed within the adjustable range, Ω max Indicates the upper limit of the speed within the adjustable range.

[0032] Furthermore,

[0033] In S4, the rotor target speed Ω at the current time step is calculated as:

[0034] Ω=MIN(Ω3,Ω t-1 +k×Δt)(Ω>Ω t-1 )

[0035] Ω=MAX(Ω3,Ω t-1 -k×Δt)(Ω<Ω t-1 )

[0036] Among them, Ω t-1 represents the target speed of the previous time step, k represents the rate of change of the rotor speed, and Δt represents the time step.

[0037] Furthermore,

[0038] After S4, the method further includes:

[0039] S5, the speed change command is sent only when the difference between the rotor target speed Ω and the speed in the previous time step is greater than the preset threshold, and the rotor target speed Ω is reached at a rate that does not exceed the limit;

[0040] If the difference between the rotor target speed Ω and the speed of the previous time step is less than a preset threshold, the rotor target speed Ω adopts the speed of the previous time step.

[0041] A helicopter rotor speed correction control law designed by the present invention can adjust the rotor speed within a variable range by using atmospheric density compensation and true airspeed correction, while avoiding small amplitude oscillations of the rotor speed. The speed correction control law in the present invention can effectively compensate for the lift loss of the rotor under high-altitude and low-atmospheric density conditions, while reducing rotor noise while ensuring low-altitude rotor capability, and can delay the generation of blade tip shock waves during high-speed forward flight, effectively improving the helicopter rotor capability and environmental adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A schematic flow chart of a method for designing a helicopter rotor speed correction control law provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0043] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings.

[0044] The rotor speed correction control law in the present invention takes into account atmospheric density compensation and true airspeed correction, and ensures that the target speed is between the upper and lower speed limits. At the same time, in order to avoid endless small oscillations of the speed near a stable value, the speed change instruction will be sent only when the difference between the target speed and the speed of the previous time step is not less than a certain threshold, and the target speed will be reached at a suitable rate. If the difference between the target speed and the speed of the previous time step is less than the threshold, the speed will be locked.

[0045] When calculating the target speed, the relative atmospheric density is first calculated using the measured static pressure and external atmospheric temperature. The rotor speed is compensated based on the relative atmospheric density and true air speed to obtain the rotor speed Ω1 corrected based on the atmospheric density and true air speed, as shown in the following formula:

[0046]

[0047] C ρ =288.15 / (273.15+T)×(P / 1013.25)

[0048] C V =0(V <V min )

[0049] C V =(VV min ) / (V max -V min )(V min ≤V≤V max )

[0050] C V =1(V>V max )

[0051] Where, Ω0 represents the reference rotor speed, Ω V min Indicates the corrected speed under low speed conditions, Ω V max Indicates the corrected speed under high speed conditions, C V Indicates the true airspeed conversion factor, C ρ represents the relative atmospheric density, T represents the measured external atmospheric temperature (unit: °C), P represents the measured static pressure (unit: hPa), V represents the true vacuum speed, V minIndicates the minimum critical speed for speed correction, V max Indicates the maximum critical speed of the speed correction. When the true air speed is less than the minimum critical speed of the speed correction, the true air speed conversion factor is set to 0; when the true air speed is greater than the maximum critical speed of the speed correction, the true air speed conversion factor is set to 1; when the true air speed is between the maximum and minimum critical speeds of the speed correction, the true air speed conversion factor is obtained by linear interpolation.

[0052] Then, the rotor speed is further corrected based on the speed adjustment amplitude in the hovering state to obtain an unlimited corrected speed Ω2, as shown in the following formula:

[0053] Ω2=Ω1+ΔΩ hover ×(1-C V )

[0054] Where ΔΩ hover Indicates the speed adjustment amplitude in the hovering state.

[0055] Since the rotor speed has a certain adjustment range, the corrected speed needs to be limited to ensure that the corrected rotor speed is within the speed limit. If the corrected rotor speed exceeds the adjustable range, the boundary value close to the corrected speed is taken as the corrected speed Ω3 considering the boundary limit, as shown in the following formula:

[0056] Ω3=MIN[MAX(Ω2,Ω min ),Ω max ]

[0057] Among them, MIN(a,b) means the smaller value between a and b, MAX(a,b) means the larger value between a and b, Ω min Indicates the lower limit of the speed within the adjustable range, Ω max Indicates the upper limit of the speed within the adjustable range.

[0058] Finally, the speed change rate limit needs to be considered. If the difference between the corrected speed considering the boundary limit and the speed of the previous time step is too large, the target speed Ω of the current time step needs to be limited to ensure that the rotor speed change rate does not exceed the limit, see the following formula:

[0059] Ω=MIN(Ω3,Ω t-1 +k×Δt)(Ω>Ω t-1 )

[0060] Ω=MAX(Ω3,Ω t-1 -k×Δt)(Ω<Ω t-1 )

[0061] Among them, Ω t-1 represents the target speed of the previous time step, k represents the rate of change of the rotor speed, and Δt represents the time step.

[0062] The target speed calculation logic based on atmospheric density compensation and true speed correction is shown in the attached figure.

[0063] The technical solution of the present invention (1) uses atmospheric density and true airspeed to correct the rotor speed of a helicopter, compensates for the lift of the rotor at high altitude, reduces low-altitude noise, and improves the flight capability of the helicopter; (2) fully considers the low-speed state characteristics of the helicopter, and uses the speed adjustment amplitude in the hovering state to further correct the rotor speed corrected based on atmospheric density and true airspeed; (3) uses threshold setting to avoid endless small oscillations of the speed near a stable value, and uses the speed change rate as a target speed limit to avoid excessive changes in the speed.

[0064] A helicopter rotor speed correction control law designed by the present invention can adjust the rotor speed within a variable range by using atmospheric density compensation and true airspeed correction, while avoiding small amplitude oscillations of the rotor speed. The speed correction control law in the present invention can effectively compensate for the lift loss of the rotor under high-altitude and low-atmospheric density conditions, while reducing rotor noise while ensuring low-altitude rotor capability, and can delay the generation of blade tip shock waves during high-speed forward flight, effectively improving the helicopter rotor capability and environmental adaptability.

Claims

1. A method for designing a helicopter rotor speed correction control law, characterized in that: The method comprises: S1, obtains static pressure and external atmospheric temperature, calculates relative atmospheric density; calculates corrected rotor speed Ω1 based on atmospheric density and true air speed; S2, correcting the rotor speed based on the speed adjustment amplitude in the hovering state to obtain an unlimited corrected speed Ω2; S3, according to the adjustment range of the rotor speed, calculate the modified speed Ω3 considering the boundary limit; S4, according to the rotor speed change rate limit, calculate the rotor target speed Ω of the current time step.

2. A helicopter rotor speed correction control law design method according to claim 1, characterized in that: S1, obtain static pressure and external atmospheric temperature, and calculate relative atmospheric density, specifically: C ρ =288.15 / (273.15+T)×(P / 1013.25) Among them, C ρ It represents the relative atmospheric density, T represents the measured external atmospheric temperature, unit: °C, and P represents the measured static pressure, unit: hPa.

3. A helicopter rotor speed correction control law design method according to claim 2, characterized in that: S1, the method for calculating the corrected rotor speed Ω1 is specifically as follows: Corrected rotor speed Ω1: Where, Ω0 represents the reference rotor speed, Ω Vmin Indicates the corrected speed under low speed conditions, Ω Vmax Indicates the corrected speed under high speed conditions, C V Indicates the true airspeed conversion factor.

4. A helicopter rotor speed correction control law design method according to claim 3, characterized in that: True air speed conversion factor C V The value of is: C V =0(V <V min ) C V =(VV min )(V max -V min )(V min ≤V≤V max ) C V =1(V>V max ) Where V represents true airspeed, V min Indicates the minimum critical speed for speed correction, V max Indicates the maximum critical speed for speed correction.

5. A helicopter rotor speed correction control law design method according to claim 4, characterized in that: In S2, the unlimited corrected speed Ω2 is calculated as: Ω2=Ω1+ΔΩ hover ×(1-C V ) Among them, ΔΩ hover Indicates the speed adjustment amplitude in the hovering state.

6. A helicopter rotor speed correction control law design method according to claim 5, characterized in that: The modified speed Ω3 calculated in S3 considering the boundary limit is specifically: Ω3=MIN[MAX(Ω2,Ω min ),Oh max ] Among them, MIN(a,b) means the smaller value between a and b, MAX(a,b) means the larger value between a and b, Ω min Indicates the lower limit of the speed within the adjustable range, Ω max Indicates the upper limit of the speed within the adjustable range.

7. A helicopter rotor speed correction control law design method according to claim 6, characterized in that: In S4, the rotor target speed Ω at the current time step is calculated as: Ω=MIN(Ω3,Ω t-1 +k×Δt)(Ω>Ω t-1 ) Ω=MAX(Ω3,Ω t-1 -k×Δt)(Ω<Ω t-1 ) Among them, Ω t-1 represents the target speed of the previous time step, k represents the rate of change of the rotor speed, and Δt represents the time step.

8. The method for designing a helicopter rotor speed correction control law according to claim 1, characterized in that: After S4, the method further includes: S5, the speed change command is sent only when the difference between the rotor target speed Ω and the speed in the previous time step is greater than the preset threshold, and the rotor target speed Ω is reached at a rate that does not exceed the limit; If the difference between the rotor target speed Ω and the speed of the previous time step is less than a preset threshold, the rotor target speed Ω adopts the speed of the previous time step.

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