Method for detecting overlarge descent rate alarm constant false alarm rate of terrain perception and alarm system

Abstract

The invention provides a method for detecting an excessive descent rate alarm constant false alarm rate of a terrain perception and alarm system. The method comprises the following steps of: 1, calculating non-alarm trajectory data of an aircraft according to flight parameters of the aircraft; calculating track data after the airplane alarms; performing collision detection on the non-alarm flight path and the post-alarm flight path with a first-order Markov random terrain, and judging whether the alarm is successful or unnecessary; 2, a Monte Carlo method is used for carrying out a large amount of simulation, statistics is carried out on a successful alarm rate and a false alarm rate to generate an SOC curve, and an optimal alarm threshold point is selected; 3, selecting a constant false alarm rate range according to the obtained optimal alarm threshold point; according to the selected constant false alarm rate, obtaining a relation between a descent rate and an alarm height; and 4, repeating the step 3 to obtain the optimal constant false alarm rate. The method can effectively reduce the false alarm rate of the alarm in the overlarge descent rate mode, increases the safe flight probability, and is suitable for more flight conditions.

Description

Technical Field

[0001] The invention belongs to the technical field of terrain perception and alarm, and relates to a method for detecting a constant false alarm rate of an excessive descent rate alarm of a terrain perception and alarm system. Background Art

[0002] The Terrain Awareness and Warning System (TAWS) is an airborne avionics system developed to help pilots resolve controlled flight into terrain accidents. The core functions of TAWS include six warning modes and a forward-looking function, which together ensure flight safety and help pilots take timely risk avoidance measures in various potentially dangerous situations.

[0003] In the Terrain Awareness and Warning System, the excessive descent rate warning is also called the Mode 1 warning. Mode 1 is a key configuration in the aircraft warning system, which is used to monitor the aircraft's descent rate based on radio altitude and trigger an alarm when it exceeds a predetermined threshold. To avoid aviation accidents, this system monitors radio altitude and descent rate, and if a warning is triggered, it will release sound and light signals.

[0004] However, Mode 1 also has the problem of false alarms, which means that the system mistakenly identifies the normal descent rate as an excessive descent rate, resulting in unnecessary alarm triggering. This false alarm phenomenon may be caused by a variety of factors, such as sensor data fluctuations, environmental interference, or improper algorithm settings. Frequent false alarms may not only distract the pilot's attention, but also trigger unnecessary emergency operations and increase the tension during the flight. Therefore, optimizing and improving data processing capabilities to reduce the occurrence of false alarms has become an important measure to ensure flight safety and enhance pilot trust. Summary of the invention

[0005] Purpose of the invention: The technical problem to be solved by the present invention is to provide a constant false alarm rate detection method for excessive descent rate alarm in a terrain perception and warning system in view of the deficiencies in the prior art. In the field of target detection using radar technology, the constant false alarm rate (CFAR) algorithm, as a target detection method, has undergone a development process from the traditional mean class to the modern neural network. The present invention focuses on the obstacle avoidance data of the aircraft under different terrains and different flight speeds to establish the basis for the warning model, so that the warning threshold is more suitable for actual flight; by adjusting the warning altitude, the probability of safe flight can be effectively increased while maintaining a constant false alarm rate.

[0006] The method of the present invention specifically comprises the following steps:

[0007] Step 1: Calculate the aircraft's non-alarm trajectory data and post-alarm trajectory data, perform collision detection on the non-alarm flight trajectory and post-alarm flight trajectory with the first-order Markov random terrain, and determine whether it is a successful alarm or an unnecessary alarm. An unnecessary alarm is a false alarm.

[0008] Step 2, using the Monte Carlo method to perform simulation, statistically calculate the success alarm rate and false alarm rate to generate a system operating characteristic (SOC) curve, and select the optimal alarm threshold point;

[0009] Step 3, according to the obtained optimal alarm threshold point, the false alarm rate P(UA) of the optimal alarm threshold point is processed differently as a constant false alarm rate; the relationship between the descent rate and the alarm height is obtained from the obtained constant false alarm rate;

[0010] Step 4, repeat step 3, compare the effects of constant false alarm rate under different treatments, and obtain the best constant false alarm rate.

[0011] Furthermore, step 1 includes:

[0012] Step 1.1, generate a first-order Markov random terrain:

[0013] In a first-order Gaussian Markov terrain, the value of the terrain height at any point depends only on the height value of the previous position, and this dependence is described by a normal distribution, which is used to generate a height with a mean of 0 and a variance of σ 2 One-dimensional random terrain model, the current terrain height y n and the terrain height y at the next moment n+1 The following relations are satisfied:

[0014] y n+1 =e -β y n +ξ n

[0015] The intermediate parameter β = 1 / l0, l0 is the correlation length; ξ n is satisfied with a mean of 0 and a variance of σ 2 (1-e -2β ) is a normally distributed random variable, expressed as:

[0016] ξ n ~N(0,σ 2 (1-e -2β ))

[0017] Where e represents a natural constant;

[0018] Changing σ and l0 can produce different terrains;

[0019] Step 1.2, calculating the aircraft's no-alarm trajectory data according to the aircraft's flight parameters;

[0020] Step 1.3, calculate the trajectory data after the aircraft alarm by combining the pilot delay time and the track angle change rate;

[0021] Step 1.4, perform collision detection between the flight trajectory and the first-order Markov random terrain to determine whether the alarm is successful.

[0022] Furthermore, step 1.2 includes:

[0023] Assume that the aircraft is a point mass moving at a uniform speed, with an initial state of (v0,h0,l0) and a state at time t of (v t ,h t ,l t ), where v0, v t They represent the airspeed of the aircraft at time 0 and time t respectively; h0, h t They represent the radio altitude of the aircraft at time 0 and time t respectively; l0, l t They represent the horizontal flight distance of the aircraft at time 0 and the horizontal flight distance at time t respectively; since the aircraft moves at a uniform speed, v0 = v t =v, v is a constant speed; θ0 is the flight path angle of the aircraft;

[0024] After a normal flight time t, the aircraft's radio altitude is: h t =h0-v·sinθ0·t, the horizontal flight distance of the aircraft is: l t =l0+v·cosθ0·t.

[0025] Furthermore, step 1.3 includes:

[0026] Step 1.3.1, generate the reaction delay phase trajectory:

[0027] The height h(t) of the aircraft at any time during the reaction delay phase is:

[0028] h(t)=h0-v·sinθ0·t

[0029] Set the delay time for the pilot to take action after the alarm is t delay , the height h1 of the aircraft when taking measures is calculated as:

[0030] h1=h0-v·sinθ0·t delay ;

[0031] Step 1.3.2, generate the trajectory of the pull-up phase:

[0032] The aircraft's angle of attack α and the engine's angle of attack ω are relatively small. In order to simplify the model, the aircraft's angle of attack α and the engine's angle of attack ω are set to 0. At the same time, when pulling up, the aircraft's pull-up action is set to be stable and uniform, without considering the inclination angle. In this way, the aircraft will maintain a constant pitch speed in the vertical direction and fly along an arc with a radius of R. The vertical track angle gradually changes from θ0 to θ1, and the track angle change rate is constant. The time t spent in this stage pullup for:

[0033]

[0034] The height h(t) of the aircraft at any time t during the pull-up phase is:

[0035]

[0036] Where h1 represents the altitude of the aircraft when the measure is taken, d represents the integral sign, and τ represents the variable to be integrated;

[0037] At the end of the pull-up phase, the aircraft's altitude h2 is:

[0038]

[0039] Step 1.3.3, generate the trajectory of the stable holding phase:

[0040] The aircraft climbs at a constant speed at a fixed vertical track angle θ1. The height h(t) of the aircraft at any time t is:

[0041] h(t)=h2+v·sinθ1·t.

[0042] Furthermore, step 1.4 includes:

[0043] During each flight simulation, if the normal no-warning trajectory collides with the terrain, the number of no-warning aircraft collisions will increase by 1; if the trajectory collides with the terrain at any time after the alarm, it will be regarded as an alarm failure, and the number of collisions after the alarm will increase by 1.

[0044] Furthermore, step 2 includes:

[0045] Repeat steps 1.1 to 1.4, use the Monte Carlo method to simulate the near-ground flight event, and calculate the successful alarm rate P(SA) and the false alarm rate P(UA):

[0046] P(SA)=1-X1 / X3,

[0047] P(UA)=1-X2 / X3,

[0048] Where X1 represents the number of times the aircraft hits the ground without an alarm, X2 represents the number of times the aircraft hits the ground after an alarm, and X3 represents the total number of simulations;

[0049] The SOC curve is drawn with P(UA) as the horizontal axis and P(SA) as the vertical axis, the value of P(SA)-P(UA) is taken as the alarm benefit, and the maximum value of the alarm benefit is taken as the optimal alarm threshold point.

[0050] Furthermore, step 3 includes:

[0051] The P(UA) obtained by the optimal alarm threshold point is used as the constant false alarm rate, and steps 1 to 2 are repeated to obtain the warning altitude under the constant false alarm rate; the complete alarm envelope is obtained by changing the descent speed.

[0052] Furthermore, the present invention also provides an electronic device, including a processor and a memory, wherein the memory stores program code, and when the program code is executed by the processor, the processor executes the steps of the described method.

[0053] Furthermore, the present invention also provides a storage medium storing a computer program or instruction, which executes the steps of the method when the computer program or instruction is run on a computer.

[0054] Compared with the prior art, the beneficial effects that can be achieved by adopting the above technical solution in the embodiments of this specification include: the present invention sets a constant false alarm rate to ensure that the false alarm rate remains within a set threshold, thereby dynamically adjusting the warning height, thereby improving the accuracy and reliability of the alarm. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more clear.

[0056] Figure 1 This is a trajectory modeling diagram of an embodiment of the present invention.

[0057] Figure 2 is a flow chart of an embodiment of the present invention.

[0058] Figure 3 This is a schematic diagram of the mode 1 alarm envelope finally generated by an embodiment of the present invention. DETAILED DESCRIPTION

[0059] like Figure 1 and Figure 2 As shown, an embodiment of the present invention provides a method for detecting a constant false alarm rate of an excessive descent rate alarm of a terrain perception and alarm system, comprising the following steps:

[0060] Step 1: Calculate the aircraft's non-alarm trajectory data based on the aircraft's flight parameters; then calculate the aircraft's post-alarm trajectory data based on the pilot's delay time, track angle change rate and other parameters; perform collision detection on the non-alarm flight trajectory and post-alarm flight trajectory with the first-order Markov random terrain to determine whether the alarm is successful or unnecessary (false alarm);

[0061] Step 2: Use the Monte Carlo method to perform a large number of simulations, calculate the successful alarm rate and false alarm rate to generate the SOC curve, and select the optimal alarm threshold point;

[0062] Step 3: According to the obtained optimal alarm threshold point, select the range of constant false alarm rate; and obtain the relationship between the descent rate and the alarm height from the selected constant false alarm rate;

[0063] Wherein step 1 comprises the following steps:

[0064] Step 1.1: Generate a first-order Markov random terrain:

[0065] In a first-order Gaussian Markov terrain, the value of the terrain height at any point depends only on the height value of its previous position, and this dependence is described by a normal distribution, which is used to generate a height with a mean of 0 and a variance of σ 2 A one-dimensional random terrain model:

[0066] y n+1 =e -β y n +ξ n (1)

[0067] Where β = 1 / l0, l0 is the correlation length; ξ n is satisfied with a mean of 0 and a variance of σ 2 (1-e -2β )A normally distributed random variable:

[0068] ξ n ~N(0,σ 2 (1-e -2β ))(2)

[0069] By changing σ and l0, different terrains can be obtained;

[0070] Step 1.2: Calculate the aircraft's no-alarm trajectory data based on the aircraft's flight parameters;

[0071] Step 1.3: Calculate the trajectory data after the aircraft alarm by combining the pilot delay time, track angle change rate and other parameters;

[0072] Step 1.4: Perform collision detection between the flight trajectory and the first-order Markov random terrain to determine whether the alarm is successful;

[0073] The step 1.2 specifically includes:

[0074] Assume that the aircraft is a point mass moving at a uniform speed, with an initial state of (v0,h0,l0) and a state at time t of (v t ,h t ,l t ), where v0, v t They represent the airspeed of the aircraft at time 0 and time t respectively; h0, h t They represent the radio altitude of the aircraft at time 0 and time t respectively; l0, l t They represent the horizontal flight distance of the aircraft at time 0 and the horizontal flight distance at time t respectively; since the aircraft moves at a uniform speed, v0 = v t =v, v is a constant speed; θ0 is the flight path angle of the aircraft;

[0075] Then after time t, the radio altitude of the aircraft is:

[0076] h t =h0-v·sinθ0·t (3);

[0077] The horizontal flight distance of the aircraft is:

[0078] l t =l0+v·cosθ0·t (4)

[0079] The step 1.3 further comprises:

[0080] Step 1.3.1: Generate reaction delay phase trajectory

[0081] The height h(t) of the aircraft at any time during the reaction delay phase is:

[0082] h(t)=h0-v·sinθ0·t (5)

[0083] Set the delay time for the pilot to take action after the alarm is t delay , the height h1 of the aircraft when taking measures is calculated as:

[0084] h1=h0-v·sinθ0·t delay (6)

[0085] Step 1.3.2: Generate the pull-up phase trajectory

[0086] The aircraft's angle of attack α and the engine's angle of attack ω are relatively small. To simplify the model, they are assumed to be 0. At the same time, when pulling up, it is assumed that the aircraft's pulling up action is stable and uniform, and the tilt angle is not considered. In this way, the aircraft will maintain a constant pitch speed in the vertical direction and fly along an arc with a radius of R. The vertical track angle gradually changes from θ0 to θ1, and the track angle change rate is constant. The time t spent in this stage pullup for:

[0087]

[0088] The height h(t) of the aircraft at any time during the pull-up phase is:

[0089]

[0090] At the end of the pull-up phase, the aircraft's altitude h2 is:

[0091]

[0092] Step 1.3.3: Generate stable hold phase trajectory

[0093] The aircraft climbs at a constant speed at a fixed vertical track angle θ1. The height h(t) of the aircraft at any time is:

[0094] h(t)=h2+v·sinθ1·t (10)

[0095] The step 1.4 further comprises:

[0096] During each flight simulation, if the normal no-warning trajectory collides with the terrain, the number of no-warning aircraft collisions will increase by 1; if the trajectory collides with the terrain at any time after the alarm, it will be regarded as an alarm failure, and the number of collisions after the alarm will increase by 1.

[0097] The method for detecting excessive descent rate alarm constant false alarm of a ground proximity warning system according to claim 2, wherein step 2 comprises:

[0098] Repeat steps 1.1 to 1.4, use the Monte Carlo method to simulate the near-ground flight event, and calculate the successful alarm rate P(SA) and the false alarm rate P(UA); where P(SA) = 1-the number of aircraft collisions without an alarm / total number of simulations; P(UA) = 1-the number of aircraft collisions after an alarm / total number of simulations; draw an SOC curve with P(UA) as the horizontal axis and P(SA) as the vertical axis, use the value of P(SA)-P(UA) as the alarm benefit, and use its maximum value as the optimal alarm threshold point.

[0099] The method for detecting excessive descent rate alarm constant false alarm of a ground proximity warning system according to claim 3, wherein step 3 comprises:

[0100] Select the appropriate P(UA) as the constant false alarm rate through the optimal alarm threshold point, repeat steps 1 to 2, and obtain the warning altitude under the optimal constant false alarm rate; by changing the descent speed, a complete alarm envelope can be obtained.

[0101] In this embodiment, under the condition that the terrain variance is 269 and the airspeed range is 1000 to 5000 feet per minute, the constant false alarm rate alarm envelope and the maximum benefit alarm envelope obtained according to steps 1 to 3 are as follows: Figure 3 shown.

[0102] In this embodiment, under the condition of maximum alarm benefit and constant false alarm rate, the overall P(SA) is reduced from 80.43% to 73.54%, a decrease of 8.57%; the overall P(UA) is reduced from 21.16% to 16%, a decrease of 24.4%, thereby achieving a greater reduction in P(UA) with a smaller P(SA) loss.

[0103] The experimental results show that the method in this embodiment can obtain a reasonable and effective warning envelope. The warning envelope finally generated effectively reduces the false alarm rate, allowing pilots to better handle excessive descent rate warning events.

[0104] The present invention provides a method for detecting a constant false alarm rate of an excessive descent rate alarm of a terrain sensing and warning system. There are many methods and ways to implement the technical solution. The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be considered as the protection scope of the present invention. All components not specified in this embodiment can be implemented using existing technologies.

Claims

1. A method for detecting a constant false alarm rate of an excessive descent rate alarm in a terrain sensing and warning system, characterized in that: The following steps are involved: Step 1: Calculate the aircraft's non-alarm trajectory data and post-alarm trajectory data, perform collision detection on the non-alarm flight trajectory and post-alarm flight trajectory with the first-order Markov random terrain, and determine whether it is a successful alarm or an unnecessary alarm. An unnecessary alarm is a false alarm. Step 2, using the Monte Carlo method to perform simulation, statistically calculate the successful alarm rate and false alarm rate to generate the system operation performance SOC curve, and select the optimal alarm threshold point; Step 3, according to the obtained optimal alarm threshold point, the false alarm rate P(UA) of the optimal alarm threshold point is processed differently as a constant false alarm rate; the relationship between the descent rate and the alarm height is obtained from the obtained constant false alarm rate; Step 4, repeat step 3, compare the effects of constant false alarm rate under different treatments, and obtain the best constant false alarm rate.

2. The method according to claim 1, characterized in that Step 1 includes: Step 1.1, generate a first-order Markov random terrain: In a first-order Gaussian Markov terrain, the value of the terrain height at any point depends only on the height value of the previous position, and this dependence is described by a normal distribution, which is used to generate a height with a mean of 0 and a variance of σ 2 One-dimensional random terrain model, the current terrain height y n and the terrain height y at the next moment n+1 The following relations are satisfied: and n+1 =e -β and n +ξ n The intermediate parameter β = 1 / l0, l0 is the correlation length; ξ n is satisfied with a mean of 0 and a variance of σ 2 (1-e -2β ) is a normally distributed random variable, expressed as: x n ~N(0,σ 2 (1-e -2β )) Where e represents a natural constant; Changing σ and l0 can produce different terrains; Step 1.2, calculating the aircraft's no-alarm trajectory data according to the aircraft's flight parameters; Step 1.3, calculate the trajectory data after the aircraft alarm by combining the pilot delay time and the track angle change rate; Step 1.4, perform collision detection between the flight trajectory and the first-order Markov random terrain to determine whether the alarm is successful.

3. The method according to claim 2, characterized in that Step 1.2 includes: Assume that the aircraft is a point mass moving at a uniform speed, with an initial state of (v0,h0,l0) and a state at time t of (v t ,h t ,l t ), where v0, v t They represent the airspeed of the aircraft at time 0 and time t respectively; h0, h t They represent the radio altitude of the aircraft at time 0 and time t respectively; l0, l t They represent the horizontal flight distance of the aircraft at time 0 and the horizontal flight distance at time t respectively; since the aircraft moves at a uniform speed, v0 = v t =v, v is a constant speed; θ0 is the flight path angle of the aircraft; After a normal flight time t, the aircraft's radio altitude is: h t =h0-v·sinθ0·t, the horizontal flight distance of the aircraft is: l t =l0+v·cosθ0·t.

4. The method according to claim 3, characterized in that Step 1.3 includes: Step 1.3.1, generate the reaction delay phase trajectory: The height h(t) of the aircraft at any time during the reaction delay phase is: h(t)=h0-v·sinθ0·t Set the delay time for the pilot to take action after the alarm is t delay , the height h1 of the aircraft when taking measures is calculated as: h1=h0-v·sinθ0·t delay ; Step 1.3.2, generate the trajectory of the pull-up phase: The aircraft's angle of attack α and the engine's angle of attack ω are set to 0. When pulling up at the same time, the aircraft's pull-up action is set to be stable and uniform, regardless of the tilt angle. The aircraft will maintain a constant pitch speed in the vertical direction and fly along an arc with a radius of R. The vertical track angle gradually changes from θ0 to θ1, and the track angle change rate is constant. The time t pullup for: The height h(t) of the aircraft at any time t during the pull-up phase is: Where h1 represents the altitude of the aircraft when the measure is taken, d represents the integral sign, and τ represents the variable to be integrated; At the end of the pull-up phase, the aircraft's altitude h2 is: Step 1.3.3, generate the trajectory of the stable holding phase: The aircraft climbs at a constant speed at a fixed vertical track angle θ1. The height h(t) of the aircraft at any time t is: h(t)=h2+v·sinθ1·t.

5. The method according to claim 4, characterized in that Step 1.4 includes: During each flight simulation, if the normal no-warning trajectory collides with the terrain, the number of no-warning aircraft collisions will increase by 1; if the trajectory collides with the terrain at any time after the alarm, it will be regarded as an alarm failure, and the number of collisions after the alarm will increase by 1.

6. The method according to claim 5, characterized in that Step 2 includes: Repeat steps 1.1 to 1.4, use the Monte Carlo method to simulate the near-ground flight event, and calculate the successful alarm rate P(SA) and the false alarm rate P(UA): P(SA)=1-X1 / X3, P(UA)=1-X2 / X3, Where X1 represents the number of times the aircraft hits the ground without an alarm, X2 represents the number of times the aircraft hits the ground after an alarm, and X3 represents the total number of simulations; The SOC curve is drawn with P(UA) as the horizontal axis and P(SA) as the vertical axis, the value of P(SA)-P(UA) is taken as the alarm benefit, and the maximum value of the alarm benefit is taken as the optimal alarm threshold point.

7. The method according to claim 6, characterized in that Step 3 includes: The P(UA) obtained by the optimal alarm threshold point is used as the constant false alarm rate, and steps 1 to 2 are repeated to obtain the warning altitude under the constant false alarm rate; the complete alarm envelope is obtained by changing the descent speed.

8. An electronic device, characterized in that: The method comprises a processor and a memory, wherein the memory stores program codes, and when the program codes are executed by the processor, the processor executes the steps of the method according to any one of claims 1 to 7.

9. A storage medium, characterized in that: A computer program or instruction is stored, and when the computer program or instruction is run on a computer, the steps of the method according to any one of claims 1 to 7 are executed.

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