Aircraft speed monitoring method, aircraft

Abstract

The present application provides an aircraft speed monitoring method and an aircraft, and relates to the field of unmanned aerial vehicles. The aircraft speed monitoring method includes obtaining the optical flow speed corresponding to the current flight speed of the aircraft based on the optical flow method; when it is determined that the optical flow speed is outside a preset detection range, controlling the camera device of the aircraft to adjust the focal length; when it is determined that the optical flow speed after the camera device adjusts the focal length is within the preset detection range, obtaining the adjusted focal length value of the camera device; based on the adjusted focal length value, the flight altitude of the aircraft and the preset speed calculation relationship, obtaining the flight speed of the aircraft. When the aircraft is in a state where the optical flow method cannot calculate its own flight speed, the camera focal length is adjusted so that the aircraft can obtain its own flight speed in different flight states, thereby facilitating precise control of the aircraft.

Description

Technical Field

[0001] The present invention relates to the technical field of unmanned aerial vehicles (UAVs), and in particular to an aircraft speed monitoring method and an aircraft. Background Art

[0002] Currently, drone flight speed calculations typically use optical flow technology, which typically involves image block matching, the LK optical flow algorithm, or corner matching. Furthermore, optical flow methods must meet three requirements: constant brightness, spatial consistency, and minimal motion. Minimal motion means that changes in time do not cause drastic changes in position, meaning that the displacement of pixels between the two captured frames is minimal.

[0003] Due to the inherent limitations of the optical flow method, calculating a drone's flight speed based on it requires that its speed and altitude remain within a certain range. If these ranges are exceeded, the speed cannot be calculated. Specifically, when the camera is close to an object at the same speed, the pixels in the captured image will experience excessive motion, resulting in no identical pixels between adjacent frames. This makes it impossible to calculate the flight speed using the optical flow method. Conversely, when the camera is far from an object, the pixel motion is less than the optical flow method's lower speed limit, making it impossible to calculate the flight speed. Similarly, if the altitude remains constant but the flight speed is too fast or too slow, the speed can also be calculated. This can manifest as a drone experiencing significant back-and-forth swaying or rapid drift at very low altitudes, and slow drift at high altitudes. Summary of the Invention

[0004] In view of this, when the optical flow method is used in the prior art to calculate the flight speed of an aircraft in different altitude ranges, speed distortion occurs and the flight speed cannot be obtained. The present invention aims to provide an aircraft speed monitoring method and an aircraft, so that the aircraft can obtain its own accurate speed at different altitudes through the optical flow method, thereby achieving precise control of the aircraft.

[0005] In order to achieve the above objectives, the embodiments of the present application are implemented in the following manner:

[0006] In a first aspect, an embodiment of the present application provides a method for monitoring the speed of an aircraft, comprising: obtaining an optical flow speed corresponding to the current flight speed of the aircraft based on an optical flow method; when it is determined that the optical flow speed is outside a preset detection range, controlling the camera device of the aircraft to adjust the focal length, wherein the preset detection range is smaller than the actual detection range, the lower limit of the preset detection range is the calculation lower limit of the optical flow method, and the upper limit of the preset detection range is set based on the resolution of the image captured by the camera device; after determining that the camera device adjusts its focal length, when the optical flow speed is within the preset detection range, obtaining the adjusted focal length value of the camera device; and obtaining the flight speed of the aircraft based on the relationship between the adjusted focal length value, the flight altitude of the aircraft, and the preset speed calculation.

[0007] In this embodiment, when the optical flow velocity is outside the actual detection range, it indicates that the optical flow method cannot be used to calculate the optical flow velocity or flight speed. Because the optical flow method calculates the optical flow velocity using images captured by a camera, before velocity distortion occurs, the camera focal length can be changed to alter the captured image, allowing the aircraft's flight speed to be reflected in the image, allowing the optical flow method to continue calculating the optical flow velocity and flight speed. Furthermore, when the optical flow method is able to calculate the flight speed after the focal length is adjusted, using the captured data and a preset speed calculation formula can more quickly and efficiently calculate the flight speed. Since calculating the optical flow velocity after adjusting the aircraft's focal length requires reprocessing the captured image, using the optical flow method to recalculate the optical flow velocity consumes additional computational resources. Therefore, using the preset speed calculation formula eliminates the need for the aircraft to use the optical flow method to calculate the flight speed. Thus, by adjusting the camera focal length, the aircraft can use the optical flow method to determine its flight speed in different flight states, facilitating precise control of the aircraft.

[0008] In one embodiment, when it is determined that the optical flow speed is outside a preset detection range, the camera device of the aircraft is controlled to adjust the focal length, including: when it is determined that the optical flow speed is greater than the upper limit of the preset detection range, the camera device is controlled to reduce the focal length.

[0009] In one embodiment, when it is determined that the optical flow speed is outside the preset detection range, the camera device of the aircraft is controlled to adjust the focal length, including: when it is determined that the optical flow speed is less than the lower limit of the preset detection range, the camera device is controlled to increase the focal length.

[0010] In this embodiment, different focal length adjustment methods are provided to address different situations where the optical flow method is about to be unable to calculate the flight speed, that is, when the optical flow speed is outside the preset detection range but has not yet exceeded the maximum detection range. According to the different focal length adjustment methods, the focal length of the camera device is quickly adjusted accordingly to quickly obtain the optical flow speed and flight speed, thereby achieving precise control of the aircraft.

[0011] In one embodiment, before obtaining the optical flow velocity corresponding to the current flight velocity of the aircraft based on the optical flow method, the method includes: controlling the camera device to set the focal length to the median value of the zoom range of the camera device.

[0012] In this embodiment, the focal length of the camera device is set to the middle value of the zoom range, which can make the focal length adjustment faster and more sensitive.

[0013] In one embodiment, the aircraft speed monitoring method further includes: when it is determined that the optical flow speed is outside a preset detection range, obtaining the flight status of the aircraft, the flight status including the change in altitude and the change in the flight speed; based on the flight status, controlling the sensor in the camera device to adjust the frame rate; when it is determined that the optical flow speed is within the preset detection range after the sensor adjusts the frame rate, obtaining the adjusted frame rate value of the sensor; and obtaining the flight speed of the aircraft based on the calculated relationship between the adjusted frame rate value, the flight altitude and the preset speed.

[0014] In this embodiment, when the optical flow method is about to fail to calculate the flight speed or optical flow velocity, that is, when the optical flow method is outside the preset detection range but within the actual detection range, a second adjustment method is provided. Since the calculation of the optical flow velocity by the optical flow method is also affected by the interval between two adjacent frames of captured images, the interval between captured images can be changed by adjusting the frame rate of the camera sensor, thereby enabling the calculation of the flight speed based on the optical flow method. When the flight speed can be calculated based on the optical flow method after adjusting the frame rate, the flight speed can be calculated more quickly and efficiently using the collected data and the preset speed calculation formula, so that the aircraft does not need to expend more computing resources to calculate the corresponding flight speed through the newly obtained optical flow velocity, thereby making the process of obtaining the flight speed faster.

[0015] In one embodiment, based on the flight state, the sensor in the camera device is controlled to adjust the frame rate, including: when it is determined that the aircraft is in a first flight state, the camera device is controlled to increase the frame rate; wherein the first flight state indicates that the current flight altitude of the aircraft remains unchanged and the flight speed increases.

[0016] In one embodiment, controlling the sensor in the camera device to adjust the frame rate based on the flight state includes: when it is determined that the aircraft is in a second flight state, controlling the camera device to increase the frame rate; wherein the second flight state indicates that the current flight speed of the aircraft remains unchanged and the flight altitude decreases.

[0017] In this embodiment, different frame rate adjustment methods are provided for different situations to quickly respond to different flight states of the aircraft, so that the aircraft can obtain the flight speed in different flight states and achieve precise control. In addition, adjusting the frame rate can also prevent the upper and lower limits of the optical flow speed from being affected by the flight speed being too fast or too slow, thereby making the method of calculating the flight speed in the first embodiment of the first aspect faster and more sensitive.

[0018] In a second aspect, an embodiment of the present application provides an aircraft, comprising: an aircraft body equipped with a processor, the processor being used to execute the aircraft speed monitoring method as described in any one of the first aspects; a camera device being arranged on the aircraft body and being used to capture images; the processor being further used to control the aircraft body so that the aircraft body controls the camera device to adjust the focal length; the camera device being further connected to the processor and being used to adjust the frame rate based on the control instructions of the processor; the camera device being further used to send the adjusted focal length value to the processor.

[0019] In one embodiment, the camera device includes: a zoom camera connected to the aircraft body, used to adjust the focal length based on the control instruction; a sensor arranged in the zoom camera, connected to the processor, used to adjust the frame rate of the sensor based on the control instruction.

[0020] In one embodiment, the sensor is further configured to obtain a focal length value of the zoom camera after adjustment; and the processor is further configured to obtain a frame rate value of the sensor after adjustment.

[0021] In this embodiment, a zoom camera is used to enable the camera device to change the focal length, change the image captured by the camera device, change the frame rate through the sensor, and control the interval time of the camera device capturing images, thereby enabling the optical flow method to continue to calculate the flight speed.

[0022] Other features and advantages of the present disclosure will be set forth in the following description, or some features and advantages may be inferred or unambiguously determined from the description, or may be learned by practicing the above-mentioned technology of the present disclosure.

[0023] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments of the present invention are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0025] Figure 1 A structural block diagram of an aircraft provided in an embodiment of the present application;

[0026] Figure 2 A flow chart of a method for monitoring aircraft speed provided in an embodiment of the present application;

[0027] Figure 3 A flowchart of another aircraft speed monitoring method provided in an embodiment of the present application;

[0028] Figure 4 This is a schematic diagram of the pinhole imaging principle provided in an embodiment of the present application.

[0029] Icons: aircraft 300; aircraft body 310; processor 311; drive device 312; camera device 320; sensor 322; zoom camera 321. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0031] See also Figure 1 , Figure 1 An aircraft 300 provided in one embodiment of the present application includes an aircraft body 310 and a camera device 320 .

[0032] In one embodiment, the aircraft body 310 is equipped with a processor 311, which is used to execute the two aforementioned aircraft speed monitoring methods; the camera device 320 is provided on the aircraft body 310 and is used to capture images; the processor 311 is also used to control the aircraft body 310, so that the aircraft body 310 controls the camera device 320 to adjust the focal length; the camera device 320 is also connected to the processor 311 and is used to adjust the frame rate based on the control instructions of the processor 311; the camera device 320 is also used to send the adjusted focal length value to the processor 311.

[0033] In this embodiment, a processor 311 is mounted within the aircraft body 310, and the aircraft speed calculation process is performed by the processor 311. The specific process of the processor 311 controlling the aircraft body 310 to control the camera device 320 to adjust the focal length may be that the processor 311 issues a control instruction to the drive device 312 disposed within the aircraft, and the drive device 312 drives the camera device 320 to adjust the focal length.

[0034] In one embodiment, the camera device 320 includes a zoom camera 321, which is connected to the aircraft body 310 and is used to adjust the focal length based on the control of the aircraft body 310; a sensor 322 is arranged in the zoom camera 321 and is connected to the processor, and is used to adjust the frame rate of the sensor based on the control instructions.

[0035] In this embodiment, since the focus value of the camera device 320 needs to be changed to monitor the flight speed, the camera of the camera device 320 needs to be a camera that can adjust the focus, that is, a zoom camera 321. The zoom camera 321 can be driven by the driving device 312 to change the focus.

[0036] In this embodiment, the zoom camera 321 is equipped with a sensor 322, which can accurately obtain the real-time focal length value of the zoom camera 321. Exemplarily, the sensor 322 can be a capacitive displacement sensor.

[0037] In this embodiment, the frame rate of the sensor 322 is adjustable, and the adjustment of the frame rate can be controlled by the processor 311 .

[0038] In one embodiment, the sensor 322 is further configured to obtain the focal length value of the zoom camera 321 after adjustment; and the processor is further configured to obtain the frame rate value of the sensor after adjustment.

[0039] In this embodiment, the sensor 322 can obtain the focal length value of the zoom camera, but the sensor 322 cannot obtain its own frame rate value, which needs to be calculated by the processor.

[0040] Please refer to Figure 2 , based on the same inventive concept, Figure 2 A flowchart of a method for monitoring aircraft speed is provided in accordance with an embodiment of the present application. The method may include the following steps:

[0041] S100, obtaining an optical flow velocity corresponding to the current flight velocity of the aircraft based on an optical flow method.

[0042] In one embodiment, the LK optical flow algorithm in the optical flow method is used to obtain the optical flow speed corresponding to the current flight speed of the aircraft.

[0043] In the embodiments of the present application, the optical flow method is required to calculate the optical flow velocity, so here we first briefly introduce the LK (Lucas–Kanade) optical flow algorithm involved in this application.

[0044] The LK optical flow algorithm, a type of optical flow method, is an optical flow estimation algorithm based on two-frame differences. It makes three assumptions: brightness constancy, minimal motion, and spatial consistency. Constancy refers to the fact that the brightness of a pixel remains constant over time. This is a fundamental requirement of all optical flow methods and must be met. Minimal motion means that changes in time do not cause drastic changes in the position of the selected pixel. This allows the partial derivative of grayscale with respect to position to be calculated using the grayscale value changes caused by position changes between adjacent frames. It can be understood that the grayscale value at a position changes while the brightness of the pixel remains unchanged. This minimal motion condition must be met by all optical flow methods. Spatial consistency refers to the fact that pixels that are adjacent in the previous frame are also adjacent in the next frame. This is a unique assumption of the LK optical flow algorithm. This is because calculating the velocity in the x and y directions requires solving multiple equations simultaneously. The spatial consistency assumption allows the establishment of n equations using n neighboring pixels.

[0045] The LK optical flow algorithm calculates optical flow velocity by measuring the change in the same pixel between two consecutive image frames. Specifically, optical flow velocity = the displacement of the same pixel between two consecutive image frames / the time interval between the two frames. Therefore, changes in the image content of two consecutive captured frames, or changes in the time interval between the two captured images, will affect the calculated optical flow velocity. This section only briefly explains the LK optical flow algorithm; the specifics of its calculation method are prior art and will not be elaborated in this solution.

[0046] In this embodiment, the optical flow velocity corresponding to the current flight speed of the aircraft is calculated by the LK optical flow algorithm, which is recorded as v(x, y), where v(x) represents the horizontal optical flow velocity and v(y) represents the longitudinal optical flow velocity.

[0047] In one embodiment, before obtaining the optical flow velocity corresponding to the current flight velocity of the aircraft based on the optical flow method, the camera device is controlled to set the focal length to the median value of the zoom range of the camera device.

[0048] In this embodiment, the aircraft's camera device is equipped with a zoom camera. When the aircraft's camera device is activated, the focal length of the camera device is set to the middle value of the zoom range. For example, when the zoom range of the camera device is 3mm-16mm, the focal length of the camera is set to 9.5mm.

[0049] S110 , when it is determined that the optical flow velocity is outside the preset detection range, controlling the camera device of the aircraft to adjust the focal length.

[0050] In one embodiment, the preset detection range is smaller than the actual detection range.

[0051] In this embodiment, the optical flow velocity of the aircraft can be obtained when it is within the actual detection range. It can be understood that the optical flow method can obtain the optical flow velocity when it is outside the detection range and within the actual detection range. However, due to the continuous change of the optical flow velocity, if it is not adjusted in time, the optical flow velocity will exceed the actual detection range, making it impossible to calculate the optical flow velocity. Therefore, it is necessary to adjust the focal length in time when it exceeds the preset detection range.

[0052] In one embodiment, the upper limit of the preset detection range is determined based on the resolution of the image captured by the camera device.

[0053] In this embodiment, the upper limit of the preset detection range is set to threshold T, which is typically half the smaller value of the image resolution. Too small a threshold T value causes the camera to frequently adjust focus, while too large a value makes focus adjustment insensitive and takes a long time. Testing has shown that half the resolution is optimal for T. For example, when the image resolution is 640*480, the T value is typically 240, expressed in pixels. The actual detection range is set based on the image resolution. Specifically, the upper limit can be 480, which is greater than the threshold T of the preset detection range.

[0054] In one embodiment, the preset detection range lower limit is the calculation lower limit of the optical flow method.

[0055] In this embodiment, since the optical flow velocity is calculated using the LK optical flow algorithm, the preset detection range is limited by the LK optical flow algorithm. Specifically, the LK optical flow algorithm calculates optical flow velocity based on pixel changes, and cannot calculate changes less than 1 pixel. Therefore, the minimum detection velocity of the LK optical flow algorithm is 1 pixel, which means that the lower limit of the preset detection range is also 1 pixel. The actual detection range also uses the optical flow method to calculate the optical flow velocity. Therefore, the lower limit of the actual detection range is the same as the lower limit of the preset detection range.

[0056] In one embodiment, when it is determined that the optical flow velocity is greater than the upper limit of the preset detection range, the camera device is controlled to reduce the focal length.

[0057] In this embodiment, when both the transverse and longitudinal optical flow velocities exceed the upper limit of the preset detection range, the camera device is controlled to reduce its focal length. Specifically, when v(x) > T and v(y) < -T, the camera device is controlled to reduce its focal length. Alternatively, when v(y) > T and v(x) < -T, the camera device is controlled to reduce its focal length. In either case, the optical flow velocity is considered to be greater than the upper limit of the preset detection range.

[0058] In this embodiment, when controlling the imaging device to reduce the focal length, the lower limit of the reduction is the lower limit of the zoom range of the imaging device. That is to say, when controlling the imaging device to reduce the focal length, the adjustable range of the focal length is between the current focal length value and the lower limit of the zoom range of the imaging device.

[0059] In one embodiment, when it is determined that the optical flow velocity is less than the lower limit of the preset detection range, the imaging device is controlled to increase the focal length.

[0060] In this embodiment, when both the horizontal optical flow velocity and the vertical optical flow velocity exceed the lower limit of the preset detection range, the imaging device is controlled to increase the focal length. Since the lower limit calculated by the LK optical flow algorithm is 1 pixel, when v(x) > -1 and v(x) < 1, or when v(y) > -1 and v(y) < 1, the imaging device is controlled to increase the focal length. Both cases can be regarded as the optical flow velocity being less than the lower limit of the preset detection range.

[0061] In this embodiment, when controlling the imaging device to increase the focal length, the upper limit of the increase in the focal length is the upper limit of the zoom range of the imaging device. That is to say, when controlling the imaging device to increase the focal length, the adjustable range of the focal length is between the current focal length value and the upper limit of the zoom range of the imaging device.

[0062] In one embodiment, when the optical flow velocity is within the preset detection range, the current flight speed of the aircraft can be directly calculated by the optical flow method.

[0063] S120. When it is determined that the optical flow velocity after the imaging device adjusts the focal length is within the preset detection range, obtain the adjusted focal length value of the imaging device.

[0064] In one embodiment, the optical flow velocity is obtained based on the optical flow method.

[0065] In this embodiment, it can be that the optical flow velocity is calculated in real time by the LK optical flow algorithm during the process of the imaging device adjusting the focal length until the calculated optical flow velocity is within the preset detection range, and then the focal length value is no longer adjusted.

[0066] In this embodiment, it can also be that every time the imaging device completes a focal length adjustment, the aircraft calculates the optical flow velocity using the current focal length until the calculated optical flow velocity is within the preset detection range, and then the focal length value is no longer adjusted.

[0067] In one embodiment, when the calculated optical flow velocity is within the preset detection range, the focal length value is no longer adjusted, and the focal length value at this time is obtained. Exemplarily, when v(x) < T and v(y) > -T, it is considered that the focal length adjustment is completed. The way to obtain the focal length can be through the sensor inside the imaging device.

[0068] S130. Based on the adjusted focal length value, the flight altitude of the aircraft, and the preset speed calculation relationship, obtain the flight speed of the aircraft.

[0069] In one embodiment, the preset speed calculation relationship is set based on the pinhole imaging principle, where the preset speed calculation formula v = (d × x × ps) / (t × f), where the camera's pixel size (or length) is ps, meaning each pixel has a length of ps, which is a constant and is the same for the same sensor. The camera's focal length is f, where x is the optical flow length, d is the flight altitude, and t is the time interval between consecutive images captured by the camera.

[0070] See also Figure 4 To make the principle of this embodiment easier to understand, Figure 4 A schematic diagram of the pinhole imaging principle is provided. In this embodiment, the preset speed calculation formula is obtained based on the pinhole imaging principle. The pinhole imaging principle formula is:

[0071] H1:L1=H2:L2

[0072] Where H1 is the length of the object imaged on the image plane, L1 is the focal length of the camera, L2 is the distance between the camera and the object, and H2 is the length of the object.

[0073] The image of H2 on the image plane occupies x pixels, so the pinhole imaging principle can be converted into formula (1):

[0074]

[0075] Where l is the length H2 of the object and d is the distance L2 from the object to the camera.

[0076] In the optical flow method, assuming that the movement distance of an object is l, the generated optical flow is x. It can be understood that the optical flow x is the number of pixels occupied by the object on the image plane. When the optical flow x exceeds the maximum resolution of the camera device, optical flow distortion will occur. Using the velocity calculation formula v = l / t (where t is the movement time), formula (1) can be converted to formula (2):

[0077]

[0078] Wherein, formula (2) is the preset speed calculation formula.

[0079] In this embodiment, the pixel x in the preset speed calculation formula is calculated by the LK optical flow algorithm, and the final output result of the LK algorithm is the optical flow speed speed_flow(x, y), where x is the horizontal displacement per unit time, and y is the vertical displacement per unit time.

[0080] In this embodiment, in the preset speed calculation formula, ps is the pixel particle size of the sensor, and time t is the time taken by the camera device to capture two adjacent frames of images, that is, the inverse of the sensor's frame rate, t=1 / fps, where fps is the sensor's frame rate.

[0081] In one embodiment, the flight altitude of the aircraft is obtained by other means. For example, the altitude can be calculated by a barometer or ultrasonic detector carried by the aircraft.

[0082] In this embodiment, after determining that all factors in the preset speed calculation formula are available, the aircraft can obtain the current flight speed of the aircraft using the preset speed calculation formula. For example, when the aircraft's flight speed remains unchanged but the flight speed cannot be calculated using the LK optical flow algorithm (i.e., x reaches its maximum value), if the aircraft's flight altitude d decreases, the focal length f can be simultaneously reduced to maintain the preset speed calculation formula unchanged. When it is determined that the optical flow velocity after adjusting the focal length is within the preset detection range, the focal length adjustment is considered complete. The focal length value at this time is obtained, and then the aircraft's altitude d, the pixel particle size ps of the camera device, and the optical flow velocity calculated by the optical flow method are used to generate the optical flow x. The time t obtained by acquiring two adjacent frames of image capture is used to calculate the aircraft's flight speed at this time.

[0083] In this embodiment, because the focal length change causes changes in the captured image, calculating optical flow velocity using the optical flow method may require reprocessing the image, and after processing, the flight velocity must be calculated using the optical flow method. Therefore, in this embodiment, after adjusting the focal length, using the preset velocity calculation formula can both obtain accurate flight velocity, but using the preset velocity calculation formula is faster and more efficient, eliminating the need for optical flow calculation, and facilitating precise control of the aircraft.

[0084] In this embodiment, it is understood that the focal length adjustment method of the present application embodiment is adjusted based on a preset calculation formula. Specifically, if the flight speed remains unchanged and the altitude increases or decreases, the focal length of the camera device will increase or decrease accordingly; if the flight altitude remains unchanged and the flight speed increases or decreases, the focal length of the camera device will decrease or increase accordingly. When both the flight speed and the altitude remain unchanged, the generated optical flow x can be changed by changing the focal length, so that the optical flow velocity can be calculated and the flight speed can be calculated accordingly.

[0085] Please refer to Figure 3 , Figure 3 A flowchart of another aircraft speed monitoring method provided in one embodiment of the present application, the method may include the following steps:

[0086] S210: When it is determined that the optical flow velocity is outside the preset detection range, the flight state of the aircraft is obtained.

[0087] In one embodiment, before determining whether the optical flow velocity is within a preset detection range, the optical flow velocity of the current flight speed of the aircraft is obtained based on an optical flow method.

[0088] In this embodiment, the method for obtaining the optical flow velocity corresponding to the flight speed is the same as in the first aircraft speed monitoring method S100, using the LK optical flow algorithm to calculate the optical flow velocity corresponding to the aircraft's current flight speed. Additionally, the method for determining whether the optical flow velocity is outside the preset detection range is the same as in the first aircraft speed monitoring method S110 and will not be further described here.

[0089] In one embodiment, the acquired flight status of the aircraft includes changes in altitude and flight speed.

[0090] In this embodiment, the flight speed can be calculated in real time using a preset speed calculation formula. Therefore, the flight speed change is obtained through the flight speed change when the flight speed can be directly obtained.

[0091] In this embodiment, the flight speed is calculated using a preset speed calculation formula. This requires controlling one of the flight states (altitude or speed) while maintaining it constant and increasing or decreasing the other. For example, the flight altitude remains constant while the flight speed increases or decreases. While the altitude can be directly obtained through other means, the flight status can be obtained through the aforementioned method. The specific flight speed value must be obtained through subsequent calculations.

[0092] S220 , controlling the sensor in the camera device to adjust the frame rate based on the flight status.

[0093] In one embodiment, a sensor is provided inside the camera device, and the sensor is used to control the number of images captured by the camera device per unit time.

[0094] In this embodiment, the sensor can adjust the frame rate to set the number of image frames captured by the camera device per second. For example, when the frame rate of the camera device is 25 frames, it indicates that the camera device can capture 25 frames of images per second.

[0095] In this embodiment, the frame rate can reflect the interval between two frames of images. The interval between two frames of images is equal to the inverse of the frame rate, that is, t = 1 / fps, where fps is the frame rate. For example, for an image with a frame rate of 25 frames, the interval is 1 / 25 second.

[0096] In this embodiment, the frame rate of the camera device needs to be adjusted, so a camera device with adjustable frame rate is selected, and the specific adjustment range is set based on the performance of the camera device. In addition, adjusting the frame rate can also prevent the speed from being too fast or too slow to affect the upper and lower limits of the optical flow speed, thereby making the method of calculating the flight speed by adjusting the focal length faster and more sensitive.

[0097] In one embodiment, the camera device adjusts the frame rate based on a preset speed calculation formula and the flight state. Specifically, t = 1 / fps in the preset speed calculation formula. This means that the adjusted frame rate is reflected in the formula as a change in time t. Therefore, while the flight state remains unchanged, the preset speed calculation formula can be maintained by changing the frame rate.

[0098] In one embodiment, when the aircraft is determined to be in a first flight state, the camera device is controlled to increase the frame rate. The first flight state represents an increase in the aircraft's current flight altitude while maintaining a constant flight speed. Specifically, when the flight altitude remains constant and the flight speed increases, the time t in the preset speed calculation formula can be reduced while maintaining other factors in the formula constant. Reducing time t can be achieved by increasing the frame rate. Specifically, increasing the frame rate can reduce time t while maintaining other factors in the preset speed calculation formula constant, thereby obtaining the real-time flight speed when the flight altitude remains constant and the flight speed increases.

[0099] In one embodiment, when the aircraft is determined to be in a second flight state, the camera device is controlled to increase its frame rate; the second flight state indicates that the aircraft's current flight speed remains unchanged while its altitude decreases. Specifically, as the altitude decreases, while other factors in the preset speed calculation formula remain unchanged, the time t needs to be increased. This increase in time t can be achieved by increasing the camera device frame rate, thereby allowing the corresponding flight speed to be calculated using the preset speed calculation formula.

[0100] In one embodiment, when it is determined that the aircraft is in the third flight state, the camera device is controlled to reduce the frame rate; wherein the third flight state indicates that the current flight speed of the aircraft remains unchanged and the flight altitude increases.

[0101] In one embodiment, when it is determined that the aircraft is in the fourth flight state, the camera device is controlled to reduce the frame rate; wherein the fourth flight state indicates that the flight altitude of the aircraft remains unchanged and the flight speed decreases.

[0102] S230 , when it is determined that the optical flow velocity after the sensor adjusts the frame rate is within a preset detection range, obtain the frame rate value after the sensor adjusts the frame rate.

[0103] In this embodiment, the change in frame rate also changes the time interval between two consecutive image frames, and thus the optical flow velocity calculated using the LK optical flow algorithm. Specifically, as the frame rate increases, the time interval between two image frames decreases, and the calculated optical flow velocity is higher than the pre-adjusted optical flow velocity. Therefore, when changing the sensor's frame rate, the optical flow velocity must also be recalculated to ensure it remains within the preset detection range.

[0104] S240 , obtaining the flight speed of the aircraft based on the adjusted frame rate value, the flight altitude, and the preset speed calculation relationship.

[0105] In one embodiment, t=1 / fps is substituted into a preset speed calculation formula to calculate the current flight speed of the aircraft.

[0106] In this embodiment, the method for obtaining other parameters is the same as that in S130, and will not be described in detail here.

[0107] In the embodiments provided herein, it should be understood that the disclosed methods and devices may also be implemented in other ways. The device embodiments described above are merely illustrative. The functional modules in the various embodiments of the present application may be integrated together to form an independent part, or each module may exist independently, or two or more modules may be integrated to form an independent part.

[0108] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

[0109] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply the existence of any such actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or device comprising the element.

Claims

1. A method for monitoring aircraft speed, characterized in that: include: Obtain the optical flow speed corresponding to the current flight speed of the aircraft based on the optical flow method; When it is determined that the optical flow velocity is outside a preset detection range, controlling the camera device of the aircraft to adjust the focal length, wherein the preset detection range is smaller than the actual detection range, the lower limit of the preset detection range is the calculation lower limit of the optical flow method, and the upper limit of the preset detection range is determined based on the resolution of the image captured by the camera device; When it is determined that the optical flow velocity after the camera device adjusts the focal length is within the preset detection range, obtaining the focal length value of the camera device after the adjustment; Obtaining a flight speed of the aircraft based on the adjusted focal length value, the flight altitude of the aircraft, and a preset speed calculation relationship; When determining that the optical flow velocity is outside a preset detection range, controlling the camera device of the aircraft to adjust the focal length includes: when determining that the optical flow velocity is greater than an upper limit of the preset detection range, controlling the camera device to reduce the focal length; and / or when determining that the optical flow velocity is less than a lower limit of the preset detection range, controlling the camera device to increase the focal length; The method further includes: when it is determined that the optical flow velocity is outside a preset detection range, obtaining a flight state of the aircraft, the flight state including a change in altitude and a change in the flight speed; based on the flight state, controlling a sensor in the camera device to adjust a frame rate; when it is determined that the optical flow velocity after the sensor adjusts the frame rate is within the preset detection range, obtaining a frame rate value after the sensor adjusts the frame rate; and obtaining the flight speed of the aircraft based on a calculated relationship between the adjusted frame rate value, the flight altitude, and the preset speed; The preset speed calculation relationship includes: v=(d×x×ps) / (t×f) Among them, ps is the length of each pixel particle, f is the focal length value of the camera device after adjustment, x is the optical flow length, d is the flight height, and t is the interval time for the camera device to capture adjacent images.

2. The method according to claim 1, characterized in that Before obtaining the optical flow speed corresponding to the current flight speed of the aircraft based on the optical flow method, the method includes: controlling the camera device to set the focal length to the median value of the zoom range of the camera device.

3. The method according to claim 1, characterized in that Controlling the sensor in the camera device to adjust the frame rate based on the flight state includes: when it is determined that the aircraft is in a first flight state, controlling the camera device to increase the frame rate; wherein the first flight state indicates that the current flight altitude of the aircraft remains unchanged and the flight speed increases.

4. The method according to claim 1, wherein Controlling the sensor in the camera device to adjust the frame rate based on the flight state includes: when it is determined that the aircraft is in a second flight state, controlling the camera device to increase the frame rate; wherein the second flight state indicates that the current flight speed of the aircraft remains unchanged and the flight altitude decreases.

5. An aircraft, characterized in that: include: An aircraft body equipped with a processor, wherein the processor is used to execute the aircraft speed monitoring method according to any one of claims 1 to 4; A camera device, provided on the aircraft body, for collecting images; The processor is further configured to control the aircraft body so that the aircraft body controls the camera device to adjust the focal length; The camera device is further connected to the processor and is configured to adjust the frame rate based on a control instruction of the processor; The camera device is further configured to send the adjusted focal length value to the processor; The camera device includes: a zoom camera connected to the aircraft body, and configured to adjust the focal length based on control of the aircraft body; A sensor is arranged in the zoom camera and connected to the processor, and is used to adjust the frame rate of the sensor based on the control instruction; the sensor is also used to obtain the focal length value of the zoom camera after adjustment; the processor is also used to obtain the frame rate value of the sensor after adjustment.

Images