CN117891268B - Self-noise-reduction rotor unmanned aerial vehicle sound detection control method - Google Patents
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Abstract
The invention discloses a self-noise-reduction rotor unmanned aerial vehicle sound detection control method, which belongs to the technical field of sound orientation, and comprises the following steps that after a sound source orientation instruction is received, an unmanned aerial vehicle enters a working state; controlling the unmanned aerial vehicle to rise in an accelerating way until the unmanned aerial vehicle reaches the maximum rising speed and the height is larger than the safety height, and controlling the unmanned aerial vehicle to stop; when the unmanned aerial vehicle enters a free falling state, a microphone array is started to collect audio signals; when the unmanned aerial vehicle is stopped for a preset time, starting a propeller of the unmanned aerial vehicle to work at maximum power and stopping audio signal acquisition; clipping the collected audio signals to obtain effective sound signals.
Description
Technical Field
The invention relates to the technical field of sound orientation, in particular to a self-noise-reduction rotor unmanned aerial vehicle sound detection control method.
Background
The technology of determining the state and direction of a noise source by using a microphone array has been applied to the fields of noise pollution monitoring, industrial equipment fault monitoring, target state identification, sound source enhancement and the like. However, in many application scenarios, since the target is moving or does not travel along a fixed path, it is required that the microphone array can move with the target or make a patrol monitoring alarm. The unmanned aerial vehicle has the advantages of low cost, wide task range, rapid movement, flexible deployment and the like, and the microphone array device can be used for detecting sound on the unmanned aerial vehicle. However, because stronger self-noise exists in the operation process of the unmanned aerial vehicle, the acoustic signal is seriously interfered, and therefore, the application of the acoustic signal detection on the unmanned aerial vehicle system is greatly limited.
Disclosure of Invention
Aiming at the defects in the prior art, the self-noise-reduction rotor unmanned aerial vehicle sound detection control method provided by the invention can acquire high signal-to-noise ratio sound signals by creating a monitoring window period through short stop of the unmanned aerial vehicle in the air.
In order to achieve the aim of the invention, the invention adopts the following technical scheme:
the method for controlling the sound detection of the self-noise-reducing rotor unmanned aerial vehicle comprises the following steps:
S1, after receiving a sound source orientation instruction, the unmanned aerial vehicle enters a working state;
S2, controlling the unmanned aerial vehicle to rise in an accelerating way, and controlling the unmanned aerial vehicle to stop when the unmanned aerial vehicle reaches the maximum rising speed and the height is greater than the safety height;
s3, when the unmanned aerial vehicle enters a free falling state, starting a microphone array to collect audio signals;
s4, starting the unmanned aerial vehicle propeller to work at maximum power and stopping audio signal acquisition after the unmanned aerial vehicle stops for a preset time;
s5, cutting the collected audio signals to obtain effective sound signals.
Further, the method for obtaining the maximum rising speed comprises the following steps:
according to the air pressure collected by the air pressure sensor and the local ground air pressure, calculating the average vertical speed of the unmanned aerial vehicle:
Wherein, For time intervals ofAn average vertical velocity within; For time intervals of The number of test points in the test strip; The time interval between test points; Is the first The height at the location of the individual test points,∈[0,-1]；Is the local ground air pressure; atmospheric pressure at the nth test point;
When the average vertical speed is maintained at a variation amplitude within a preset proportion for a plurality of continuous time intervals T, the unmanned aerial vehicle reaches a maximum rising speed.
The beneficial effects of the technical scheme are as follows: the average vertical speed in a short time is calculated through the altitude signal approximation, so that the use of an expensive airspeed head is avoided, and the cost and the complexity of the sound detection target are reduced.
Further, the method for calculating the safety height comprises the following steps:
Dividing the calculation of the safety height into three phases, setting the time consumption of the whole flight process of the three phases as t, and respectively calculating the time of the unmanned aerial vehicle in the three phases:
Wherein, The method comprises the steps of (1) achieving the maximum vertical lifting speed for the unmanned aerial vehicle and stopping the unmanned aerial vehicle; The time from restarting the unmanned aerial vehicle to reaching the maximum rotating speed of the propeller is obtained through experiments; the time for the unmanned aerial vehicle propeller to reach the maximum rotating speed and to be decelerated and stopped is set; maximum lift of the unmanned aerial vehicle;
The quality of the whole unmanned aerial vehicle is that of the unmanned aerial vehicle; gravitational acceleration; is the maximum rising speed of the unmanned aerial vehicle; determining the time length of the needed effective acoustic signal according to the actual condition of the project; And Respectively obtaining the time for reducing and increasing the sound pressure level to the rated value through experiments;
Safety height The following conditions need to be satisfied:
Wherein, Is the falling height;、 respectively at Stage(s),Stage and stageThe variation of the unmanned plane height in the stage;
According to the unmanned aerial vehicle dynamic model corresponding to the three time phases, the height of each phase is obtained through the Euler method, and the unmanned aerial vehicle dynamic models of the three time phases are respectively:
Wherein, The acceleration component of the unmanned aerial vehicle in the vertical direction; is a velocity component of the unmanned aerial vehicle in the vertical direction; is the resistance coefficient in the vertical direction; For taking a sign function; lift provided for the unmanned aerial vehicle propeller; the maximum lift available to the propeller.
Further, the method for obtaining the height of each stage by the euler method comprises the following steps:
At the position of In the dynamic equation corresponding to the stage, neglectThenAndThe corresponding kinetic models within the phase can be expressed as follows:
For a pair of The differential equation of the kinetic model of the stage is converted into the following differential equation using the finite difference method:
Wherein, 、Respectively the firstThe velocity and displacement values in the vertical direction at the points; And Respectively the firstThe velocity and displacement values in the vertical direction at the points; A time step that is differential;
By passing through The difference equation of the stage calculates the height value at any momentWherein the initial value is set as:， And (2) and ,；、Respectively isEnd time of phaseAnd start timeCorresponding height values; And Respectively isEnd time of phaseAnd start timeCorresponding height values;
For a pair of The differential equation of the kinetic model of the stage is converted into the following differential equation using the finite difference method:
By passing through The difference equation of the stage calculates the height value at any momentAnd (2) and，AndRespectively isEnd time of phaseAnd start timeCorresponding height values.
The beneficial effects of the technical scheme are as follows: according to the scheme, the unmanned aerial vehicle height change prediction model is built through the unmanned aerial vehicle dynamics model, the overall time is estimated through an approximation processing method, the Euler method calculation model is calculated through numerical calculation, the safety height is obtained through calculation, the unmanned aerial vehicle can be guaranteed to have enough time to obtain the high signal-to-noise ratio acoustic signal, and meanwhile safety in the falling process of the unmanned aerial vehicle can be guaranteed.
Further, the method for clipping the collected audio signals comprises the following steps:
Calculating the sound pressure level of an audio signal, and recording the time when the sound pressure level drops to the highest interference noise sound pressure level after the unmanned aerial vehicle is stopped ; Recording time for sound pressure level to rise to highest interference noise sound pressure level after restarting unmanned aerial vehicle; Intercepting from the whole acquired audio signalTo the point ofAs an effective acoustic signal.
The interception of the audio signal is carried out by combining the sound pressure level, so that the interference of noise on the audio signal can be reduced, and the quality of the collected audio signal is improved.
Further, the expression for calculating the sound pressure level of the audio signal is:
，
Wherein, Is an audio signal; Is the reference sound pressure; Is the effective value of the sound pressure to be measured; x is the sampling point of the acoustic signal; k is the number of discrete points of the acoustic signal; k is the acoustic signal discrete point variable.
Further, the expression of the drag coefficient is:
Wherein, Is the maximum ascent speed of the unmanned aerial vehicle.
The invention has the beneficial effects that: the unmanned aerial vehicle actively stops in a short time to create a window period without self-noise, and the microphone acquires an acoustic signal with high signal-to-noise ratio in the window period; by the method, compared with the prior art that the microphone is directly used for sound signal acquisition and sound source orientation on the unmanned aerial vehicle, the influence of noise of the unmanned aerial vehicle is reduced, a target sound signal with higher signal-to-noise ratio can be obtained, and therefore the accuracy of voiceprint recognition and sound source orientation is improved.
According to the scheme, the unmanned aerial vehicle is controlled before stopping, so that the unmanned aerial vehicle has an upward initial speed before stopping, the free falling time of the unmanned aerial vehicle is prolonged, the monitoring time of a microphone is longer, and a longer high signal-to-noise ratio audio signal is obtained.
Drawings
FIG. 1 is a flow chart of one embodiment of a method for self-denoising rotorcraft acoustic detection control.
Fig. 2 is a schematic diagram of each stage of the unmanned aerial vehicle in stop and fly-away.
Fig. 3 is a full flow chart of the acoustic detection control method.
FIG. 4 is a graph showing the comparison of calculated height values with actual height values.
Fig. 5 is a waveform schematic diagram of an effective audio clip.
Fig. 6 is a schematic diagram of effective audio clipping based on sound pressure level.
Detailed Description
The following description of the embodiments of the present invention is provided to facilitate understanding of the present invention by those skilled in the art, but it should be understood that the present invention is not limited to the scope of the embodiments, and all the inventions which make use of the inventive concept are protected by the spirit and scope of the present invention as defined and defined in the appended claims to those skilled in the art.
Referring to fig. 1, fig. 1 illustrates a flow chart of one embodiment of a method of self-denoising rotorcraft acoustic detection control; as shown in FIG. 1, the method S comprises the steps S1-S5; the detailed flow of this scheme can be seen with reference to fig. 3.
In step S1, after receiving the sound source direction instruction, the unmanned aerial vehicle enters a working state.
According to the scheme, the sound source orientation instruction is an external signal, and can be sent to the flight control chip through other development boards on the unmanned aerial vehicle in a bus communication or wireless communication mode, and the instruction can be written into the flight control program for periodic execution, so that the unmanned aerial vehicle periodically enters a monitoring flight state.
In step S2, controlling the unmanned aerial vehicle to rise in an accelerating way until the unmanned aerial vehicle reaches the maximum rising speed and the height is larger than the safety height, and controlling the unmanned aerial vehicle to stop, wherein the propeller stops rotating;
In one embodiment of the present invention, the method for acquiring the maximum rising speed includes:
according to the air pressure collected by the air pressure sensor and the local ground air pressure, calculating the average vertical speed of the unmanned aerial vehicle:
Wherein, For time intervals ofAn average vertical velocity within; For time intervals of The number of test points in the test strip; The time interval between test points; Is the first The height at the location of the individual test points,∈[0,-1]；Is the local ground air pressure; atmospheric pressure at the nth test point;
when the average vertical speed is maintained at a variation amplitude within a preset proportion for a plurality of continuous time intervals T, the unmanned aerial vehicle reaches a maximum rising speed. The preferred multiple time intervals T of this embodiment are 5 consecutive time intervals T, with a preset proportion of 5%.
In implementation, the method for calculating the safety height preferably comprises the following steps:
Dividing the calculation of the safety height into three phases, setting the time consumption of the whole flight process of the three phases as t, and respectively calculating the time of the unmanned aerial vehicle in the three phases:
Wherein, The unmanned aerial vehicle has the advantages that the maximum vertical lifting speed is reached, the shutdown time after the safety height is met is the preset value, the unmanned aerial vehicle can not be completely instable due to long-time shutdown in the air in order to ensure that enough sound signals are acquired,Should satisfy；The time from 0 rotation speed to the maximum rotation speed in the rotating speed map of the propeller is the time from 0 rotation speed to the maximum rotation speed of the unmanned aerial vehicleA value; For the time of deceleration and stopping after the propeller of the unmanned aerial vehicle reaches the maximum rotating speed, the following formula can be directly used for solving:
Wherein the method comprises the steps of Is the maximum lift force of the unmanned aerial vehicle; The quality of the whole unmanned aerial vehicle is that of the unmanned aerial vehicle; gravitational acceleration; is the maximum ascent speed of the unmanned aerial vehicle.
By artificial setting, in order to ensure that enough acoustic signals are obtained, and the unmanned aerial vehicle is not completely instable due to long-time air shutdown,Should satisfy。
The values of (2) can be obtained by the following tests: the unmanned aerial vehicle is fixed on a test bed, the unmanned aerial vehicle is connected with the test bed through a tension sensor, and when the propeller of the unmanned aerial vehicle reaches the maximum rotating speed, the reading of the tension sensor is thatIs a value of (2).
In order to avoid the unmanned aerial vehicle from striking the ground when falling, the following conditions are required to be satisfied in the safety height:
i.e. the height of the unmanned aerial vehicle when the unmanned aerial vehicle is stopped is required to be larger than that of the unmanned aerial vehicle when the unmanned aerial vehicle is stopped 、、Total drop height in three stages。、The height variation of the unmanned aerial vehicle in each time period is respectively calculated by adding the height variation of the unmanned aerial vehicle in the whole time period。
The height of each stage can be obtained through the Euler method according to the unmanned aerial vehicle dynamic model corresponding to the three time stages, and the unmanned aerial vehicle dynamic models of the three time stages are respectively:
Wherein, The acceleration component of the unmanned aerial vehicle in the vertical direction; is a velocity component of the unmanned aerial vehicle in the vertical direction; is the resistance coefficient in the vertical direction; For taking a sign function; lift provided for the unmanned aerial vehicle propeller; the maximum lift available to the propeller.
In one embodiment of the invention, the method of deriving the height of each stage by the euler method comprises:
At the position of In the dynamic equation corresponding to the stage, neglectThenAndThe corresponding kinetic models within the phase can be expressed as follows:
For a pair of The differential equation of the kinetic model of the stage is converted into the following differential equation using the finite difference method:
Wherein, 、Respectively the firstThe velocity and displacement values in the vertical direction at the points; And Respectively the firstThe velocity and displacement values in the vertical direction at the points; A time step that is differential;
By passing through The difference equation of the stage calculates the height value at any momentWherein the initial value is set as:， And (2) and ,；、Respectively isEnd time of phaseAnd start timeCorresponding height values; And Respectively isEnd time of phaseAnd start timeCorresponding height values;
For a pair of The differential equation of the kinetic model of the stage is converted into the following differential equation using the finite difference method:
By passing through The difference equation of the stage calculates the height value at any momentAnd (2) and，AndRespectively isEnd time of phaseAnd start timeCorresponding height values.
Fig. 4 shows a graph of calculated height values compared to actual height values, during the period from when the unmanned aerial vehicle propeller is stopped until the unmanned aerial vehicle falls to the lowest height,The rotor unmanned aerial vehicle safety height calculated for this scheme promptly. As can be seen from the comparison between the actual test data and the actual test data in FIG. 4, the calculated safety height of the scheme is slightly lower than the actual descending height of the unmanned aerial vehicle, and no body instability occurs in the whole process. Therefore, when the height of the unmanned aerial vehicle propeller is greater than the safety height during the shutdown, the safety and stability of the unmanned aerial vehicle in the whole process can be ensured.
In practice, the expression of the preferred drag coefficient of the present solution is:
Wherein, Is the maximum ascent speed of the unmanned aerial vehicle.
In step S3, when the unmanned aerial vehicle enters a free falling state, a microphone array is turned on to collect audio signals; as fig. 2 shows a schematic diagram of each stage of stopping and flying, as can be seen from fig. 2, after the unmanned aerial vehicle is stopped, the unmanned aerial vehicle continues to move upwards under the action of inertia, and after the unmanned aerial vehicle rises to the highest point, the unmanned aerial vehicle can enter a free falling state, namely, the microphone array can be started by the scheme.
The method for stopping the unmanned aerial vehicle (namely, losing power of the unmanned aerial vehicle) can be realized in various modes, including, but not limited to, power outage of all propeller motors, 0 of control signal output of all propeller motors and the like. After stopping, the microphone starts working, the acoustic signal is collected, and the timing module in the unmanned aerial vehicle flight control chip is started. In the free falling process, the microphone continuously collects sound signals, and when the timing module in the unmanned aerial vehicle flight control chip counts time to reach set time, the unmanned aerial vehicle propeller is restarted and works with maximum power.
In step S4, after the unmanned aerial vehicle is stopped for a preset time, starting the unmanned aerial vehicle propeller to work at the maximum power and stopping audio signal acquisition; after the unmanned aerial vehicle restarts, the unmanned aerial vehicle can continuously descend by a certain height under the action of inertia, finally reaches the lowest height and starts to ascend.
Specifically, the step S4 of restarting the unmanned aerial vehicle further includes two stages S401 and S402:
s401, starting a propeller of the unmanned aerial vehicle, but not reaching the maximum rotating speed;
S402, starting the unmanned aerial vehicle propeller, enabling the unmanned aerial vehicle propeller to reach the maximum rotating speed, enabling the unmanned aerial vehicle propeller to perform deceleration motion downwards, and finally decelerating to 0, enabling the microphone to stop working, and enabling the collected original sound signal to be used as an available sound signal after cutting.
In step S5, the collected audio signal is clipped to obtain an effective acoustic signal. Before clipping, the highest interference noise sound pressure level required by the subsequent sound processing algorithm needs to be confirmed, the robustness of different algorithms is different, and the anti-interference capability is also different, so that the highest interference noise sound pressure level needs to be valued by the actual anti-interference capability of the algorithm.
In one embodiment of the present invention, a method for clipping an acquired audio signal includes:
as shown in the waveform diagram of the acoustic signal in fig. 5 and the sound pressure level diagram in fig. 6, firstly, the sound pressure level of the audio signal is calculated, and the time when the sound pressure level drops to the highest interference noise sound pressure level after the unmanned aerial vehicle is stopped is recorded ; Recording time for sound pressure level to rise to highest interference noise sound pressure level after restarting unmanned aerial vehicle; Intercepting from the whole acquired audio signalTo the point ofAs an effective acoustic signal. Wherein t 4 and t 5 correspond to the end time of t dec and the end time of t inc in fig. 5 and 6, respectively.
The expression for calculating the sound pressure level of the audio signal is:
，
Wherein, Is an audio signal; For reference sound pressure, the reference sound pressure is generally taken in air Pa；；Is the effective value of the sound pressure to be measured; x is the sampling point of the acoustic signal, K is the discrete point number of the acoustic signal; k is the acoustic signal discrete point variable.
In fig. 5, a portion having a sound pressure level of 60dB or less is taken as effective sound signal data based on the calculation result.
In summary, according to the scheme, the unmanned aerial vehicle accelerates to rise firstly, and stops after reaching the maximum speed, so that the microphone can pick up the sound for a longer time; because the scheme is to collect the audio signal in the free falling time period after the unmanned aerial vehicle propeller stalls, longer audio signal data with high signal to noise ratio can be obtained.
Claims (5)
1. The method for controlling the sound detection of the self-noise-reducing rotor unmanned aerial vehicle is characterized by comprising the following steps:
S1, after receiving a sound source orientation instruction, the unmanned aerial vehicle enters a working state;
S2, controlling the unmanned aerial vehicle to rise in an accelerating way, and controlling the unmanned aerial vehicle to stop when the unmanned aerial vehicle reaches the maximum rising speed and the height is greater than the safety height;
s3, when the unmanned aerial vehicle enters a free falling state, starting a microphone array to collect audio signals;
s4, starting the unmanned aerial vehicle propeller to work at maximum power and stopping audio signal acquisition after the unmanned aerial vehicle stops for a preset time;
S5, cutting the collected audio signals to obtain effective sound signals;
the method for acquiring the maximum rising speed comprises the following steps:
according to the air pressure collected by the air pressure sensor and the local ground air pressure, calculating the average vertical speed of the unmanned aerial vehicle:
Wherein, For time intervals ofAn average vertical velocity within; For time intervals of The number of test points in the test strip; The time interval between test points; Is the first The height at the location of the individual test points,∈[0,-1]；Is the local ground air pressure; atmospheric pressure at the nth test point;
When the average vertical speed is kept within the variation amplitude of the preset proportion in a plurality of continuous time intervals T, the unmanned aerial vehicle reaches the maximum rising speed;
the method for calculating the safety height comprises the following steps:
Dividing the calculation of the safety height into three phases, setting the time consumption of the whole flight process of the three phases as t, and respectively calculating the time of the unmanned aerial vehicle in the three phases:
Wherein, The method comprises the steps of (1) achieving the maximum vertical lifting speed for the unmanned aerial vehicle and stopping the unmanned aerial vehicle; The time from restarting the unmanned aerial vehicle to reaching the maximum rotating speed of the propeller is obtained through experiments; the time for the unmanned aerial vehicle propeller to reach the maximum rotating speed and to be decelerated and stopped is set; maximum lift of the unmanned aerial vehicle;
The quality of the whole unmanned aerial vehicle is that of the unmanned aerial vehicle; gravitational acceleration; is the maximum rising speed of the unmanned aerial vehicle; determining the time length of the needed effective acoustic signal according to the actual condition of the project; And Respectively obtaining the time for reducing and increasing the sound pressure level to the rated value through experiments;
Safety height The following conditions need to be satisfied:
Wherein, Is the falling height;、 respectively at Stage(s),Stage and stageThe variation of the unmanned plane height in the stage;
According to the unmanned aerial vehicle dynamic model corresponding to the three time phases, the height of each phase is obtained through the Euler method, and the unmanned aerial vehicle dynamic models of the three time phases are respectively:
Wherein, The acceleration component of the unmanned aerial vehicle in the vertical direction; is a velocity component of the unmanned aerial vehicle in the vertical direction; is the resistance coefficient in the vertical direction; For taking a sign function; lift provided for the unmanned aerial vehicle propeller; the maximum lift available to the propeller.
2. The self-noise-reducing rotary-wing unmanned aerial vehicle sound detection control method according to claim 1, wherein the method of obtaining the height of each stage by the euler's solution comprises:
At the position of In the dynamic equation corresponding to the stage, neglectThenAndThe corresponding kinetic models within the phase can be expressed as follows:
For a pair of The differential equation of the kinetic model of the stage is converted into the following differential equation using the finite difference method:
Wherein, 、Respectively the firstThe velocity and displacement values in the vertical direction at the points; And Respectively the firstThe velocity and displacement values in the vertical direction at the points; A time step that is differential;
By passing through The difference equation of the stage calculates the height value at any momentWherein the initial value is set as:， And (2) and , ；、Respectively isEnd time of phaseAnd start timeCorresponding height values; And Respectively isEnd time of phaseAnd start timeCorresponding height values;
For a pair of The differential equation of the kinetic model of the stage is converted into the following differential equation using the finite difference method:
By passing through The difference equation of the stage calculates the height value at any momentAnd (2) and，AndRespectively isEnd time of phaseAnd start timeCorresponding height values.
3. The self-noise-reducing rotor unmanned aerial vehicle sound detection control method according to claim 1, wherein the method for clipping the collected audio signal is as follows:
Calculating the sound pressure level of an audio signal, and recording the time when the sound pressure level drops to the highest interference noise sound pressure level after the unmanned aerial vehicle is stopped ; Recording time for sound pressure level to rise to highest interference noise sound pressure level after restarting unmanned aerial vehicle; Intercepting from the whole acquired audio signalTo the point ofAs an effective acoustic signal.
4. The self-noise-reducing rotary-wing unmanned aerial vehicle sound detection control method according to claim 3, wherein the expression for calculating the sound pressure level of the audio signal is:
，
Wherein, Is an audio signal; Is the reference sound pressure; is the effective value of the sound pressure to be measured; x is the sampling point of the acoustic signal, K is the discrete point number of the acoustic signal; k is the acoustic signal discrete point variable.
5. The self-noise-reducing rotor unmanned aerial vehicle sound detection control method according to claim 2, wherein the expression of the drag coefficient is:
Wherein, Is the maximum ascent speed of the unmanned aerial vehicle.
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| CN109856593A (en) * | 2018-12-21 | 2019-06-07 | 南京理工大学 | Intelligent miniature array sonic transducer and its direction-finding method towards sound source direction finding |
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