Disclosure of Invention
The invention aims at: aiming at the problem that the indoor positioning effect of a vehicle is poor when a current object flows into a garden, the satellite-free signal area positioning system based on UWB is provided.
The technical scheme adopted by the invention is as follows: the system comprises a plurality of logistics points arranged in the park, a logistics point service end deployed at each logistics point and UWB positioning labels arranged at the front end of each unmanned logistics point; each logistics point is provided with a plurality of UWB positioning base stations respectively, and the UWB positioning base stations receive data packets sent by UWB positioning labels;
The logistics point service end is used for:
the data received from each UWB positioning base station is calculated to obtain the vehicle position information corresponding to each UWB positioning tag, and the process is as follows:
grouping a plurality of UWB positioning base stations corresponding to each logistics point in pairs to form at least one clock signal deviation group and at least one redundancy group;
Respectively calculating clock deviations S1、S2 corresponding to the signal deviation group and the redundancy group, and obtaining an average clock deviation S after weighted average of the two clock deviations;
predicting a clock deviation Sk+1 of the next moment according to the clock deviation Sk of the current moment by using a Kalman filtering algorithm;
And finally, correcting the synchronous clock signal received by the UWB base station at the next moment according to the predicted clock deviation Sk+1 at the next moment to obtain more accurate time for the signal to reach the base station, and calculating the position coordinate of the vehicle according to the corrected time for the signal to reach the base station, the propagation speed of electromagnetic waves and the position coordinate of the base station.
Preferably, the logistics point service end is further configured to:
And sending reservation information to the required unmanned logistics vehicles, so that the unmanned logistics vehicles can plan an optimal path according to the distribution distance and reservation time of each logistics point in the reservation information.
Preferably, the logistics point service end is further configured to:
Loading an electronic map of a park, wherein the electronic map comprises specific positions of all logistics points, positions of all UWB positioning base stations, real-time position information of the unmanned logistics vehicle and ordering conditions of reservation information of all logistics points.
Preferably, the UWB positioning tag of each unmanned vehicle assigns a unique vehicle ID to the vehicle according to license plate information, and the ID is dynamically displayed in real time on an interface of the service end of the logistics point in the delivery process.
Preferably, the information contained in the data packet includes:
The method comprises the steps of vehicle ID, time of data transmission, position of the last moment of the vehicle, position of the vehicle at the moment, position of the next moment of the vehicle, target position of the vehicle at the moment, article information conveyed by the vehicle reaching the target position, planned walking route of the vehicle, time of the vehicle reaching the target position, coordinate information of the next target position of the vehicle, time of the vehicle reaching the next target position, article information conveyed by the vehicle reaching the next target position, current reserved time period of the vehicle, reservation information accepted by the vehicle and planned route selection of the vehicle.
Preferably, the data transmission between the UWB positioning tag and the UWB positioning base station and the data transmission between the UWB positioning base station and the logistics point server are bidirectional; the UWB positioning tag uploads vehicle information to the logistics point service end through the UWB positioning base station, and the logistics point service end issues reservation information to the UWB positioning tag of the vehicle through the UWB positioning base station.
Preferably, the UWB positioning tag of the vehicle provides a current time period capable of being reserved for the logistics point service end, the user can reserve the predicted delivery time of the vehicle through the logistics point service end interface, the vehicle plans an alternative route according to the predicted delivery time selected by the user, and the user can autonomously select the vehicle walking route according to the planned alternative route.
Preferably, the calculating the clock bias S1、S2 corresponding to the signal bias group and the redundancy group respectively, and performing weighted average on the two clock biases to obtain an average clock bias S specifically includes:
Acquiring the coordinates of a vehicle-mounted UWB positioning tag of a synchronous clock signal transmitting position, the coordinates of UWB positioning base stations and the time taken by calculating signals from transmitting to each base station;
Because clock deviation exists between the arrival of the clock signal at the base station and the receiving signal of the base station, the invention considers the influence of the clock deviation on positioning;
Subtracting the arrival time of the synchronous clock signals acquired by the two base stations in the signal deviation group and the redundant group respectively to obtain two arrival time differences A-B, A '-B' of the synchronous clock signals; the signal deviation group comprises a base station A and a base station B, and the redundancy group comprises a base station A ', a base station B';
In the signal deviation group, the arrival time difference A-B of the synchronous clock signal is subtracted from the calculated required time of the synchronous clock signal reaching the base station A, and then the subtracted time is added with the required time of the synchronous clock signal reaching the base station B to obtain the clock deviation S1 of the synchronous clock signal, and the clock deviation S2 of the synchronous clock signal of the redundancy group is obtained by the same method, and the average clock deviation S is obtained after the weighted average of the two clock deviations.
Preferably, the electronic map is formed by extracting semantic information of map points in the campus.
By adopting the technical scheme, the method has the following advantages: according to the UWB-based satellite signal-free area positioning system provided by the invention, a plurality of UWB positioning base stations are additionally arranged on each logistics point through the UWB positioning tag arranged at the front end of the unmanned logistics vehicle, and the clock deviation of the synchronizing signal is calculated by using the deployed logistics point service end, so that the purpose of correcting the arrival time of the clock signal is achieved, and the accuracy of indoor positioning of the vehicle is further improved.
Detailed Description
Specific embodiments of the invention will be described in detail below, it being noted that the embodiments described herein are for illustration only and are not intended to limit the invention. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art that: no such specific details are necessary to practice the invention. In other instances, well-known circuits, software, or methods have not been described in detail in order not to obscure the invention.
Throughout the specification, references to "one embodiment," "an embodiment," "one example," or "an example" mean: a particular feature, structure, or characteristic described in connection with the embodiment or example is included within at least one embodiment of the invention. Thus, the appearances of the phrases "in one embodiment," "in an embodiment," "one example," or "an example" in various places throughout this specification are not necessarily all referring to the same embodiment or example. Furthermore, the particular features, structures, or characteristics may be combined in any suitable combination and/or sub-combination in one or more embodiments or examples. Moreover, those of ordinary skill in the art will appreciate that the illustrations provided herein are for illustrative purposes and that the illustrations are not necessarily drawn to scale.
The present invention will be described in detail with reference to the accompanying drawings.
Referring to fig. 1 and fig. 2, the system for positioning a satellite-free signal area based on UWB provided by the embodiment of the present invention is suitable for positioning an indoor vehicle for logistics distribution in a campus, and includes a plurality of logistics points provided in the campus, a logistics point service end deployed at each logistics point, and UWB positioning tags provided at the front end of each unmanned logistics point; each logistics point is provided with a plurality of UWB positioning base stations respectively, and the UWB positioning base stations receive data packets sent by UWB positioning labels; the UWB positioning tag can be easily installed and detached, and positioning is automatically disabled after the UWB positioning tag is detached.
The logistics point service end is used for:
the data received from each UWB positioning base station is calculated to obtain the vehicle position information corresponding to each UWB positioning tag, and the process is as follows:
Grouping a plurality of UWB positioning base stations corresponding to each logistics point in pairs to form at least one clock signal deviation group and at least one redundancy group; in this embodiment, four UWB positioning base stations corresponding to one logistics point are taken as an example for explanation;
Respectively calculating clock deviations S1、S2 corresponding to the signal deviation group and the redundancy group, and obtaining an average clock deviation S after weighted average of the two clock deviations;
predicting a clock deviation Sk+1 of the next moment according to the clock deviation Sk of the current moment by using a Kalman filtering algorithm;
And finally, correcting the synchronous clock signal received by the UWB base station at the next moment according to the predicted clock deviation Sk+1 at the next moment to obtain more accurate time for the signal to reach the base station, and calculating the position coordinate of the vehicle according to the corrected time for the signal to reach the base station, the propagation speed of electromagnetic waves and the position coordinate of the base station.
The method specifically includes the steps of respectively calculating clock deviations S1、S2 corresponding to the signal deviation group and the redundancy group, and obtaining an average clock deviation S after weighted average of the two clock deviations, wherein the signal deviation group corresponds to the clock deviation S1, and the redundancy group corresponds to the clock deviation S2, and the method specifically includes:
Acquiring the coordinates of a vehicle-mounted UWB positioning tag of a synchronous clock signal transmitting position, the coordinates of UWB positioning base stations and the time taken by calculating signals from transmitting to each base station;
Because clock deviation exists between the arrival of the clock signal at the base station and the receiving signal of the base station, the invention considers the influence of the clock deviation on positioning;
Subtracting the arrival time of the synchronous clock signals measured by the two base stations in the signal deviation group and the redundant group respectively to obtain two arrival time differences A-B, A '-B' of the synchronous clock signals; the signal deviation group comprises a base station A and a base station B, and the redundancy group comprises a base station A ', a base station B';
According to the propagation speed of electromagnetic waves, the position coordinates of the vehicle-mounted UWB positioning tag updated at the previous moment and the coordinates of the UWB base stations, calculating to obtain the time required by the synchronous clock signals transmitted by the UWB positioning tag to reach each base station;
In the signal deviation group, the arrival time difference A-B of the synchronous clock signal is subtracted from the calculated required time of the synchronous clock signal reaching the base station A, and then the subtracted time is added with the required time of the synchronous clock signal reaching the base station B to obtain the clock deviation S1 of the synchronous clock signal, and the clock deviation S2 of the synchronous clock signal of the redundancy group is obtained by the same method, and the average clock deviation S is obtained after the weighted average of the two clock deviations.
The specific calculation method for predicting the clock bias Sk+1 at the next moment according to the average clock bias Sk at the current moment by using the kalman filtering algorithm is as follows:
The principle of Kalman filtering is as follows:
xk＝Axk-1+Buk-1 (1)
Pk＝APk-1AT+Q (2)
Kk＝PkHT(HPkHT+R)-1 (3)
xk＝xk+Kk(zk-Hxk) (4)
Pk＝(I-KkH)Pk (5)
Wherein xk represents the state at time k; a represents a state transition matrix and is related to a specific linear system; uk represents the influence of the outside world on the system at the time k; b represents an input control matrix, which reflects how the external influence is converted into the influence on the state; p represents an error matrix; q represents the covariance matrix of the prediction noise; r represents the covariance matrix of the measurement noise; h represents an observation matrix; kk represents the kalman gain at time K; zk represents the observed value at time k;
(1) The expression (2) represents a prediction process, the expression (1) is state prediction, and the expression (2) is error matrix prediction; (3) The equation (5) represents the correction process, (3) is Kalman gain calculation, (4) is state correction, and (5) is error matrix update;
In this example, the Kalman filtering algorithm is applied as follows:
Predicting a clock deviation Sk and a prediction error dk of the current moment according to a clock deviation Sk-1 of the previous moment, calculating Kalman gain, correcting the clock deviation Sk of the current moment, updating the prediction error, and continuously predicting a clock deviation Sk+1 of the next moment by using the updated prediction error;
Fig. 3 is a schematic diagram of a dynamic positioning experiment result of an unmanned logistics vehicle in the embodiment of the invention, and it can be seen from an image that a KF data curve 1 and a Raw data curve 2 are well fitted, the effect is smooth, no larger abrupt change point exists, and the vehicle positioning effect of the invention is accurate; wherein KF data curve 1 represents a real-time predicted car position data curve, and Raw data curve 2 represents a real car position data curve.
Specifically, UWB (Ultra wide band), high transmission rate, strong penetration, and strong anti-interference capability; when the method is applied, the logistics point server loads the electronic map of the park, and semantic information of map points in the park is extracted to form the electronic map;
Meanwhile, the UWB positioning tag of each unmanned vehicle distributes unique vehicle ID for the vehicle according to license plate information, and the ID can be dynamically displayed on the interface of the logistics point server in real time in the distribution process.
Further, in order to improve efficiency and intellectualization of campus logistics management, the logistics point server is further configured to:
And sending reservation information to the required unmanned logistics vehicles, so that the unmanned logistics vehicles can plan an optimal path according to the distribution distance and reservation time of each logistics point in the reservation information.
During distribution, the electronic map comprises specific positions of all logistics points, positions of all UWB positioning base stations, real-time position information of the unmanned logistics vehicle and ordering conditions of reservation information of all logistics points;
the information contained in the data packet sent by the UWB positioning tag is:
The method comprises the steps of vehicle ID, time of data transmission, position of the last moment of the vehicle, position of the vehicle at the moment, position of the next moment of the vehicle, target position of the vehicle at the moment, article information conveyed by the vehicle reaching the target position, planned walking route of the vehicle, time of the vehicle reaching the target position, coordinate information of the next target position of the vehicle, time of the vehicle reaching the next target position, article information conveyed by the vehicle reaching the next target position, current reserved time period of the vehicle, reservation information accepted by the vehicle and planned route selection of the vehicle.
The data transmission between the UWB positioning tag and the UWB positioning base station and the data transmission between the UWB positioning base station and the logistics point server are bidirectional; the UWB positioning tag uploads vehicle information to the logistics point service end through the UWB positioning base station, and the logistics point service end issues reservation information to the UWB positioning tag of the vehicle through the UWB positioning base station;
The UWB positioning tag of the vehicle provides a current reserved time period for the logistics point service end, a user can reserve the predicted delivery time of the vehicle through the logistics point service end interface, the vehicle plans an alternative route according to the predicted delivery time selected by the user, and the user can autonomously select the vehicle walking route according to the planned alternative route; this also allows for greater flexibility in logistics management.
By adopting the scheme, through the UWB positioning label arranged at the front end of the unmanned logistics vehicle, a plurality of UWB positioning base stations are additionally arranged at each logistics point, and the deployed logistics point service end is utilized to calculate the clock deviation of the synchronous signal, so that the purpose of correcting the arrival time of the clock signal is achieved, the accuracy of indoor positioning of the vehicle is improved, and the problem of poor indoor positioning effect is solved.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention, and are intended to be included within the scope of the appended claims and description.