Patent Application
20220146618
This application claims the benefit of priority to Taiwan Patent Application No. 109138740, filed on Nov. 6, 2020. The entire content of the above identified application is incorporated herein by reference.
Some references, which may include patents, patent applications and various publications, may be cited and discussed in the description of this disclosure. The citation and/or discussion of such references is provided merely to clarify the description of the present disclosure and is not an admission that any such reference is “prior art” to the disclosure described herein. All references cited and discussed in this specification are incorporated herein by reference in their entireties and to the same extent as if each reference was individually incorporated by reference.
The present disclosure relates to a localization method, device, and system, and more particularly to an ultra-wideband localization method, device, and system.
Unmanned aerial vehicles (UAVs), unmanned aircrafts (UAS) or drones can be classified according to fields of utilization, e.g., military, commercial, and entertainment. In recent years, the market for small-sized drones is growing. Since the small-sized drones have advantages of easy deployment, low maintenance costs, and high mobility, the small-sized drones can be used for various commercial applications. For example, commercial drones can be used for aerial photography, package delivery service, pesticide spraying, and bridge structure inspections.
As applications of UAVs (e.g., drones) become more and more diversified, more and more UAVs are likely to perform different tasks in the air in the future, and a large number of UAVs require an air traffic management center to monitor the statuses and locations of all UAVs.
Nowadays, most small-sized UAVs use the Global Positioning System (GPS) for localization. However, altitude deviations of the GPS in urban areas are usually greater than or equal to 5 meters. The altitude deviations can cause the TCAS to err in determinations of DAA, which affects aviation safety of the small-sized UAVs.
In addition, standardized management regulations have been stipulated by countries around the world for UAVs (or remotely controlled drones). For example, a user is required to pass an aeronautical knowledge test to obtain a remote pilot certificate, so as to ensure aviation safety. In the aeronautical knowledge test, the performance test in certain regions is conducted under a condition of a UAV having the GPS thereof turned off. The user then remotely controls the UAV to fly through a specific aviation route (e.g., flying in a pentagon-shaped aviation route while maintaining an altitude of 20 meters, and flying in an aviation route of a shape of the number “8” while maintaining an altitude of 50 meters, etc.). Afterwards, an examiner determines whether or not the user has passed the test through visual inspection. However, since the GPS of the UAV has been turned off and the UAV cannot autonomously transmit localization data to the air traffic management center, whether or not the user passes the test and is qualified are only determined subjectively by the examiner, so that the above-mentioned test lacks objective data to support the effectiveness thereof.
Therefore, it has become an important issue in the industry to provide a localization method, device, and system having a high accuracy (e.g., having a localization deviation being less than one meter) to overcome the above-mentioned inadequacies.
In response to the above-referenced technical inadequacies, the present disclosure provides an ultra-wideband (UWB) localization method, device, and system.
In one aspect, the present disclosure provides an ultra-wideband (UWB) localization method that is adapted to a UWB localization system. The UWB localization system includes a tag and a plurality of anchors. The UWB localization method includes: determining whether or not a plurality of UWB hardware measurement deviations are calibrated; determining, when the UWB hardware measurement deviations are calibrated, whether or not a plurality of anchor coordinates of the anchors are automatically measured; obtaining, when the anchor coordinates of the anchors are automatically measured, a plurality of measurement distances between each of the anchors and the tag, respectively, and deducting the UWB hardware measurement deviations from the measurement distances, respectively; and calculating a tag coordinate of the tag according to the measurement distances from which the UWB hardware measurement deviations are deducted.
In another aspect, the present disclosure provides a UWB localization device that is adapted to a UWB localization system. The UWB localization system includes a tag, a plurality of anchors, and a traffic management cloud server. The UWB localization device is disposed on the tag, and includes a distance measurement module, a first communication module, and a processing module. The distance measurement module is used for measuring a plurality of measurement distances between each of the anchors and the tag, respectively, and for measuring a plurality of actual altitudes between the tag and a datum plane. The first communication module is coupled to the distance measurement module, and is used to transmit the measurement distances and the actual altitudes. The processing module is coupled to the first communication module, and is used to calculate a tag coordinate of the tag according to the measurement distances and the actual altitudes and then transmit the tag coordinate to the traffic management cloud server.
In yet another aspect, the present disclosure provides a UWB localization system including a tag, a plurality of anchors, a traffic management cloud server, and a UWB localization device configured on the tag. The UWB localization device includes a distance measurement module, a first communication module, and a processing module. The distance measurement module is used for measuring a plurality of measurement distances between each of the anchors and the tag, respectively, and for measuring a plurality of actual altitudes between the tag and a datum plane. The first communication module is coupled to the distance measurement module, and is used to transmit the measurement distances and the actual altitudes. The processing module is coupled to the first communication module, and is used to calculate a tag coordinate of the tag according to the measurement distances and the actual altitudes and then transmit the tag coordinate to the traffic management cloud server.
One of the beneficial effects of the UWB localization method, device, and system of the present disclosure is that the UWB localization method, device, and system can increase localization accuracy of a Z-axis coordinate through technical solutions of “measuring the measurement distances between the tag and the anchors, respectively, through the UWB wireless communication technology” and “calculating a third coordinate component of the tag coordinate according to a cost function”.
These and other aspects of the present disclosure will become apparent from the following description of the embodiment taken in conjunction with the following drawings and their captions, although variations and modifications therein may be affected without departing from the spirit and scope of the novel concepts of the disclosure.
The described embodiments may be better understood by reference to the following description and the accompanying drawings, in which:
The present disclosure is more particularly described in the following examples that are intended as illustrative only since numerous modifications and variations therein will be apparent to those skilled in the art. Like numbers in the drawings indicate like components throughout the views. As used in the description herein and throughout the claims that follow, unless the context clearly dictates otherwise, the meaning of “a”, “an”, and “the” includes plural reference, and the meaning of “in” includes “in” and “on”. Titles or subtitles can be used herein for the convenience of a reader, which shall have no influence on the scope of the present disclosure.
The terms used herein generally have their ordinary meanings in the art. In the case of conflict, the present document, including any definitions given herein, will prevail. The same thing can be expressed in more than one way. Alternative language and synonyms can be used for any term(s) discussed herein, and no special significance is to be placed upon whether a term is elaborated or discussed herein. A recital of one or more synonyms does not exclude the use of other synonyms. The use of examples anywhere in this specification including examples of any terms is illustrative only, and in no way limits the scope and meaning of the present disclosure or of any exemplified term. Likewise, the present disclosure is not limited to various embodiments given herein. Numbering terms such as “first”, “second” or “third” can be used to describe various components, signals or the like, which are for distinguishing one component/signal from another one only, and are not intended to, nor should be construed to impose any substantive limitations on the components, signals or the like.
Referring to
In a three-dimensional model composed of X, Y, and Z axes, assuming that a coordinate of the tag T is {right arrow over (T)}({tilde over (x)},{tilde over (y)},{tilde over (z)}), and coordinates of the anchors A1 to AN are known to be A1(x1, y1, z1) to AN(xN, yN, zN), a distance di between the tag T and an ith anchor Ai can be expressed by the following equation (1):
({tilde over (x)}−xi)2+({tilde over (y)}−yi)2+({tilde over (z)}−zi)2=di2 (1); in which i is an integer, and 1≤i≤N.
Taking the anchor AN as a reference point, the distance dN between the tag T and the anchor AN can be expressed by the following equation (2):
({tilde over (x)}−xN)2+({tilde over (y)}−yN)2+({tilde over (z)}−zN)2=dN2 (2);
when {tilde over (x)}−xi={tilde over (x)}−xN−(x1−xN),{tilde over (y)}−yi={tilde over (y)}−yN(yi−yN), {tilde over (z)}−zi={tilde over (z)}−zN−(zi−zN), equation (1) can be rewritten as the following equation (3):
(({tilde over (x)}−xN)−(xi−xN))2+({tilde over (y)}−yN)−(yi−yN))2+(({tilde over (z)}−zN)−(zi−zN))2=di2 (3);
by subtracting equation (1) from equation (3) and then organizing, the following equation (4) is obtained:
(xi−xN)({tilde over (x)}−xN)+(yi−yN)({tilde over (y)}−yN)+(zi−zN)({tilde over (z)}−zN)=½(RiN2−di2+dN2) (4);
in which, RiN2=(xi−xN)2+(yi−yN)2+(z1−zN)2.
Finally, the equation (4) is rewritten into a matrix form as the following equation (5), and the coordinate {right arrow over (T)}({tilde over (x)}, {tilde over (y)}, {tilde over (z)}) of the tag T can be obtained through a least squares error (LSQ) method.
However, when a height of the tag T (i.e., the Z-axis coordinate {tilde over (z)}) is multiple times the height of the anchors A1 to AN (i.e., the Z-axis coordinates Z1 to ZN), under a premise that the LSQ method is used to solve the equations, Z-axis spans between the anchors A1 to AN are very small relative to the Z-axis coordinate {tilde over (z)} of the tag T, thereby causing altitude deviations on the scale of meters. In practice, under the premise that the LSQ method is used to solve the equations, in order to reduce the altitude deviations of the UAV (i.e., the tag T) that is tens of meters above the ground to be on the scale of centimeters, altitude differences among the anchors A1 to AN are required to be increased, which is unpractical. On the other hand, since X-axis spans and Y-axis spans between the anchors A1 to AN are large enough relative to an X-axis coordinate and a Y-axis coordinate of the tag T, the deviations solved by the LSQ method in the horizontal plane (i.e., the XY plane) are on the scale of centimeters. Accordingly, the X-axis coordinate {tilde over (x)} and the Y-axis coordinate {tilde over (y)} obtained from equations (1) to equation (5) can be substituted as constants, equation (1) is then rewritten, and the rewritten equation (1) is substituted into a cost function, indicated as equation (6), so as to calculate the Z-axis coordinate 2 of the tag T. In other words, the cost function of the present disclosure improves a conventional method of solving three unknowns to a method of solving only one unknown, through subtracting the X-axis coordinate component {tilde over (x)} and the Y-axis coordinate component {tilde over (y)} from the distance di measured by the UWB ranging method, and then calculating the Z-axis coordinate {tilde over (z)} according to the cost function.
In a scenario of a UAV operation test (e.g., a performance test), the anchors A1 to AN are arranged on the ground or close to the ground, and the UAV can then fly above the anchors A1 to AN. Accordingly, according to the scenario in practice, it is assumed in the present disclosure that the height of the tag T (i.e., the Z-axis coordinate {tilde over (z)}) is greater than an average height =zi−
ε({tilde over (z)}′)=1/N×Σ=1N[({tilde over (z)}′−z′i)2−d′i2]2 (6); in which, d′i2=d12−[({tilde over (x)}−xi)2+({tilde over (y)}−yi)2].
According to equation (6), the parameter d′i is a value obtained by subtracting the X-axis coordinate component {tilde over (x)} and the Y-axis coordinate component {tilde over (y)} from the distance di measured by the UWB ranging method. Since the parameters z′i and d′i are known, only a single variable {tilde over (z)}′ in equation (6) needs to be solved.
In order to minimize the altitude deviations, the best solution of the variable {tilde over (z)}′ in equation (6) satisfies a condition of dε/(d{tilde over (z)}′)=0, such that equation (6) can be differentiated to obtain equation (7) as follows:
f({tilde over (z)}′)={tilde over (z)}′3−A{tilde over (z)}′+B=0 (7);
in which, A=1/N×Σi=1N d′i2−3/N×Σi=1Nz′i2, B=1/N×Σi=1N d′i2z′i−1/N×Σi=1Nz′i3.
Next, Newton's approximation method as shown in equation (8) is used to obtain the solution of the variable {tilde over (z)}′ of equation (7), and iterated to ({tilde over (z)}′n+1−{tilde over (z)}′n)<0.01 (unit: meter), in which the variable {tilde over (z)}′n+1 is a solution of equation (7), and then the average height Z of the anchors A1 to AN is added to the variable {tilde over (z)}′n+1, so as to obtain the height of the tag T. Equation (8) is expressed as follows:
{tilde over (z)}′
n+1
={tilde over (z)}′
n−(f({tilde over (z)}′n))/(f{circumflex over ( )}′({tilde over (z)}′n)) (8).
The distance measurement module 31 is coupled to the first communication module 32, and is used to measure the measurement distances d1 to dN between the localization device 30 (i.e., the UAV) and the anchors A1 to AN through the UWB wireless communication technology. The GPS module 34 is coupled to the first communication module 32 for generating GPS information InfoGPS.
The first communication module 32 is coupled to the distance measurement module 31, the GPS module 34, and the processing module 33, and the first communication module 32 is used to transmit the measurement distances d1 to dN measured by the distance measurement module 31, a plurality of actual altitudes D1 to DN of the localization device 30, and the GPS information InfoGPS generated by the GPS module 34 to the processing module 33. In one embodiment, the localization device 30 further includes a height measurement module (not shown in
The processing module 33 is coupled to the first communication module 32, and is used to calculate the coordinate {right arrow over (T)}({tilde over (x)},{tilde over (y)},{tilde over (z)}) of the tag T according to the measurement distances d1 to dN and the actual altitudes D1 to DN, and then transmit the coordinate {right arrow over (T)}({tilde over (x)},{tilde over (y)},{tilde over (z)}) to at least one of a traffic management cloud server, i.e., a UAV traffic management (UTM) cloud server 10, and a remote control device 11. In one embodiment, the processing module 33 is used to execute or terminate a localization operation according to a control signal CTRL generated by the remote control device 11.
The processing module 33 includes a processor 330, a memory 331, and a second communication module 332. The processor 330 is coupled to the first communication module 32, the memory 331, and the second communication module 332, and the processor 330 is used to calculate a plurality of UWB hardware measurement deviations E1 to EN of the distance measurement module 31 and a plurality of anchor coordinates A1(x1, y1, z1) to AN(xN, yN, zN) of the anchors A1 to AN according to the measurement distances d1 to dN and the actual altitudes D1 to DN. Next, the processing module 33 can apply the measurement distances d1 to dN and the anchor coordinates A1(x1, yi, z1) to AN(xN, yN, zN) to the UWB localization model 2 shown in
The memory 331 is coupled to the processing module 33 for storing a code 333, the measurement distances d1 to dN, the actual altitudes D1 to DN, the UWB hardware measurement deviations E1 to EN, the anchor coordinates A1(x1, y1, z1) to AN(xN, yN, zN), and any information related to the localization device 30.
The second communication module 332 is coupled to the processor 330, the UTM cloud server 10, and the remote control device 11, and is used to transmit the coordinate {right arrow over (T)}({tilde over (x)},{tilde over (y)},{tilde over (z)}) to at least one of the UTM cloud server 10 and the remote control device 11 and receives the control signal CTRL generated by the remote control device 11.
Therefore, under the circuit structure shown in
Step 400: Begin.
Step 401: Determining whether or not a plurality of UWB hardware measurement deviations are calibrated. If not, proceed to step 402; if yes, proceed to step 405.
Step 402: Obtaining the measurement distances and the actual altitudes between the tag and each of the anchors.
Step 403: Obtaining the UWB hardware measurement deviations through the LSQ method.
Step 404: Recording the UWB hardware measurement deviations; then returning to step 401.
Step 405: Determining whether or not the anchor coordinates are automatically measured. If not, proceed to step 406; if yes, proceed to step 408.
Step 406: Obtaining the measurement distances between the tag and each of the anchors and deducting the UWB hardware measurement deviations from the measurement distances.
Step 407: Calculating the anchor coordinates; then returning to step 405.
Step 408: Obtaining the distances between each of the anchors and the tag, and subtracting the deviations from the distances.
Step 409: Calculating the tag coordinate.
Step 410: Transmitting the tag coordinates in real time.
Step 411: Determining whether or not to calculate the tag coordinate. If yes; proceed to step 408; if not, proceed to step 412.
Step 412: End.
In step 401 to step 404, the localization device 30 (or the tag T in
When the UWB hardware measurement deviations are calibrated, in step 405 to step 407, the localization device 30 determines whether or not the anchor coordinates A1(x1, y1, z1) to AN(xN, yN, zN) have been automatically measured.
When the anchor coordinates A1 (x1, y1, z1) to AN(xN, yN, zN) are not automatically measured, the localization device 30 obtains the measurement distances d1 to dN from the memory 331 through the processor 330 and the UWB hardware measurement deviations E1 to EN, the UWB hardware measurement deviations E1 to EN are respectively subtracted from the measurement distances d1 to dN, and then the anchor coordinates A1(x1, y1, z1) to AN(xN, yN, zN) are calculated through the processor 330.
When the anchor coordinates A1(x1, yi, zi) to AN(xN, yN, zN) have been automatically measured, in step 408 to step 410, the localization device 30 obtains the measurement distances d1 to dN from the memory 331 through the processor 330 and the UWB hardware measurement deviations E1 to EN, the UWB hardware measurement deviations E1 to EN are respectively subtracted from the measurement distances d1 to dN; the coordinate {right arrow over (T)}({tilde over (x)},{tilde over (y)},{tilde over (z)}) of the tag T is calculated through the processor 330, and then the coordinate {right arrow over (T)}({tilde over (x)},{tilde over (y)},{tilde over (z)}) of the tag T is transmitted (to the UTM cloud server 10) in real time. In step 409, the processor 330 calculates the coordinate {right arrow over (T)}({tilde over (x)},{tilde over (y)},{tilde over (z)}) of the tag T according to the cost function represented by equation (6), equation (7), and equation (8).
Finally, in step 411, the localization device 30 determines whether or not the coordinate {right arrow over (T)}({tilde over (x)},{tilde over (y)},{tilde over (z)}) of the tag T is required to be calculated. In one embodiment, the localization device 30 receives the control signal CTRL through the second communication module 332, and determines whether or not the coordinate {right arrow over (T)}({tilde over (x)},{tilde over (y)},{tilde over (z)}) of the tag T is required to be calculated according to the control signal CTRL. When the coordinate {right arrow over (T)}({tilde over (x)},{tilde over (y)},{tilde over (z)}) of the tag T is required to be calculated, the localization device 30 executes step 408 to step 410 again so as to execute the localization operation. On the other hand, when the coordinate {right arrow over (T)}({tilde over (x)},{tilde over (y)},{tilde over (z)}) of the tag T is not required to be calculated, the localization device 30 terminates the localization operation.
Therefore, through executing the process shown in
In
According to Table 1, a Z-axis coordinate range obtained by the localization method of the present disclosure is closer to the target altitude of three meters, and the 95% localization deviation accumulation value is less than 1 meter. Therefore, compared with the conventional LSQ method, the localization method of the present disclosure can effectively improve the localization accuracy of the Z-axis coordinate.
In
According to Table 2, the Z-axis coordinate range obtained by the localization method of the present disclosure is closer to the target altitude of five meters, and the 95% localization deviation accumulation value is less than 1 meter. Therefore, compared with the conventional LSQ method, the localization method of the present disclosure can effectively improve the localization accuracy of the Z-axis coordinate.
In
According to Table 3, in the localization method of the present disclosure, the higher the target altitude is, the lower the 95% localization deviation accumulation value is (i.e., the 95% localization deviation accumulation value of the target altitude of five meters is less than that of the target altitude of three meters). In other words, in the localization method of the present disclosure, the greater a distance between a flying altitude and an anchor, the higher the localization accuracy of the Z-axis coordinate.
One of the beneficial effects of the UWB localization method, device, and system of the present disclosure is that the UWB localization method, device, and system can increase localization accuracy of the Z-axis coordinate through technical solutions of “measuring the measurement distances between the tag and the anchors, respectively through the UWB wireless communication technology” and “calculating a third coordinate component of the tag coordinate according to the cost function”.
The foregoing description of the exemplary embodiments of the disclosure has been presented only for the purposes of illustration and description and is not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Many modifications and variations are possible in light of the above teaching.
The embodiments were chosen and described in order to explain the principles of the disclosure and their practical application so as to enable others skilled in the art to utilize the disclosure and various embodiments and with various modifications as are suited to the particular use contemplated. Alternative embodiments will become apparent to those skilled in the art to which the present disclosure pertains without departing from its spirit and scope.
| Number | Date | Country | Kind |
|---|---|---|---|
| 109138740 | Nov 2020 | TW | national |
