Underwater machine positioning method based on ultra wide band

Abstract

The invention provides an ultra wide band (UWB)-based underwater machine positioning method, which comprises the following steps: S1, constructing an ultra wide band (UWB) positioning network which comprises at least four anchor nodes and at least one mobile node, and the anchor nodes and the mobile node are configured with UWB communication modules; s2, performing UWB communication in the positioning network in a bidirectional flight time mode, and acquiring communication time difference between the mobile node and each anchor node; s3, respectively calculating the distance between the mobile node and each anchor node according to each communication time difference and the underwater propagation speed of electromagnetic waves during UWB communication; and S4, determining the spatial position of the mobile node according to each spacing. According to the invention, the UWB technology is applied to underwater positioning, UWB communication is carried out by constructing an UWB positioning network and adopting a two-way flight time mode, and the system has high precision and strong real-time performance of short-distance ranging positioning and is convenient to use.

Description

Technical Field

[0001] The present invention relates to the technical field of underwater positioning, and particularly to an underwater robot positioning method based on ultra-wideband. Background Art

[0002] With the deepening of marine resource development and scientific research activities, underwater robots (especially observation-class ROVs) play an increasingly important role in tasks such as underwater observation, data collection, and collaborative operations. However, their high-precision positioning technology in the underwater environment still faces significant challenges. The existing mainstream positioning methods - acoustic positioning and inertial integrated navigation systems - have the following limitations: Acoustic positioning systems (such as ultra-short baseline USBL and long baseline LBL) rely on acoustic wave signals to achieve positioning. However, their performance is significantly affected by the seawater environment (such as temperature, salinity, pressure) on the sound speed, resulting in short-range positioning errors that are usually difficult to be lower than 0.5 meters. In addition, the acoustic wave transmission speed is relatively slow (about 1500 m / s), and the signal transmission delay leads to insufficient real-time performance, making it difficult to support the rapid response requirements of dynamic operation scenarios. The LBL system needs to pre-lay a seabed beacon array, and the USBL relies on the high-precision calibration of the surface array. Both require additional equipment deployment and maintenance, significantly increasing the operation cost and complexity, and their applicability is limited in complex terrains or dynamic tasks.

[0003] Inertial integrated navigation (INS / DVL) realizes positioning through the fusion of an inertial measurement unit (IMU) and a Doppler velocity log (DVL). However, its performance is restricted by the working conditions of the DVL: the DVL needs to rely on the seabed reflection signal to measure the speed. When the ROV hovers or the height from the seabed exceeds the DVL range, the system will fail due to signal loss. At the same time, the INS has a problem of cumulative error. Frequent calibration with external references (such as GPS or acoustic beacons) is required during long-term operation, resulting in operation interruption and inability to independently maintain high-precision positioning. In narrow space or collaborative operation scenarios, the feasibility of frequent calibration is low, further restricting the practicality of this technology.

[0004] The above acoustic positioning is restricted by the sound speed change and delay, and inertial navigation is limited by terrain dependence and error accumulation. These two types of positioning methods cannot both achieve short-range high precision and strong real-time performance, resulting in insufficient positioning accuracy and poor real-time performance of existing observation-class ROVs in high-precision complex operation scenarios such as short-range ROV collaborative operations, equipment precise docking, and narrow space exploration in the underwater environment, restricting their in-depth application in fields such as ocean engineering and scientific exploration. Therefore, there is an urgent need for a new positioning method that can break through the inherent bottlenecks of acoustic and inertial technologies within a short distance range and achieve high-precision and low-latency underwater positioning to meet the increasingly complex operation requirements. Summary of the Invention

[0005] In view of this, the object of the present invention is to provide an underwater robot positioning method based on ultra-wideband, which solves the problem that the existing conventional positioning methods cannot take into account both short-distance high precision and strong real-time performance, resulting in insufficient positioning accuracy and poor real-time performance in high-precision complex operation scenarios such as underwater short-distance ROV collaborative operations, equipment precise docking, and narrow space detection of existing observation-class ROVs.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: An underwater robot positioning method based on ultra-wideband according to the present invention includes the following steps: S1. Construct an ultra-wideband (UWB) positioning network, where the positioning network includes at least four anchor nodes and at least one mobile node, and both the anchor nodes and the mobile nodes are configured with UWB communication modules; S2. In the positioning network, use the two-way time-of-flight (TW-TOF) method for UWB communication to obtain the communication time differences between the mobile node and each of the anchor nodes; S3. According to each of the communication time differences and the propagation speed of electromagnetic waves in water during the UWB communication, calculate the distances between the mobile node and each of the anchor nodes respectively; S4. Determine the spatial position of the mobile node according to each of the distances.

[0007] Preferably, when the number of the mobile nodes in this round of positioning is more than two, in step S2, it further includes: S5. Define one of the mobile nodes as the current mobile node, and the other mobile nodes as waiting mobile nodes; S6. Control the current mobile node to perform the UWB communication with each of the anchor nodes to obtain the communication time differences, and complete steps S3 and S4, and then enter step S7; S7. Define one of the waiting mobile nodes as the new current mobile node, and then command the new current mobile node to execute step S6 until the spatial positions of all the mobile nodes in this round of positioning are obtained; S8. End this round of positioning.

[0008] Preferably, the mobile node and the anchor node obtain the communication time difference through at least three signal interactions during the UWB communication.

[0009] More preferably, the content of the at least three signal interactions includes: Step1. The anchor node first sends a first signal to the mobile node and records the transmission timestamp as , the mobile node receives the first signal and records the reception timestamp as ; Step 2. The mobile node processes and sends a first response signal to the anchor node, and records the transmission timestamp as . The anchor node receives the first response signal and records the reception timestamp as ; Step 3. The anchor node sends a second signal to the mobile node and records the transmission timestamp as . The mobile node receives the second signal and records the reception timestamp as ; Then, the time of flight

[0010] wherein, , , , ; Then, the actual time of flight

[0011] The distance between the mobile node and the anchor node .

[0012] Preferably, in step S1, when the number of anchor nodes exceeds four, it further includes defining a dynamic ad-hoc network protocol to achieve autonomous switching of the anchor nodes.

[0013] Preferably, lightweight time division multiple access (TDMA) scheduling is adopted between the devices for positioning and networking.

[0014] Preferably, in the UWB communication, the received signal is processed by pulse shaping technology.

[0015] Preferably, in the UWB communication, the carrier frequency of the transmitted signal is switched according to the changes in water depth and / or salinity.

[0016] More preferably, when the water depth increases and / or the salinity increases, the carrier frequency of the transmitted signal is reduced, and a UWB communication is initiated with the reduced carrier frequency; When the water depth decreases and / or the salinity decreases, the carrier frequency of the transmitted signal is increased, and a UWB communication is initiated with the increased carrier frequency; When the water depth and / or salinity remain unchanged, the carrier frequency of the transmitted signal is maintained unchanged, and a UWB communication is initiated with the current carrier frequency.

[0017] More preferably, in the UWB communication, an improved multipath suppression algorithm is introduced to process the received signal; The improvement includes adjusting the transmission intensity parameter in the multipath suppression algorithm according to the marine environment.

[0018] Compared with the prior art, the advantageous effects of the underwater machine positioning method based on ultra-wideband described in the present invention are mainly reflected in: The present invention applies ultra-wideband technology to underwater positioning. By building an ultra-wideband (UWB) positioning network, it can support dynamic access and collaborative positioning of multiple mobile nodes, effectively leveraging the advantage of the fast propagation speed of UWB communication signals, greatly improving the real-time performance of underwater positioning and achieving millisecond-level real-time response. By using a two-way time-of-flight (TW-TOF) method for UWB communication, the propagation delay error caused by the significant attenuation of electromagnetic waves by the water medium is eliminated. This not only ensures the transmission distance of UWB signals underwater, but also greatly improves the accuracy of ranging and positioning, achieving centimeter-level positioning accuracy (<10 cm), breaking the limitations of ultra-wideband technology in underwater applications. The positioning networking device of the present invention is composed of an anchor node and a mobile node equipped with a UWB communication module. It has a simple structure and does not require the deployment of other equipment. It supports multi-mobile node collaborative positioning through a networking protocol. It does not require additional maintenance during use, has high ease of use and economy, and can be applied to short distances or confined spaces underwater. Therefore, the present invention provides a new underwater equipment positioning method that has high adaptability to underwater environments and can take into account both short-distance high precision and strong real-time performance. When used in underwater robots, it can solve the problem that existing conventional positioning methods cannot take into account both short-distance high precision and strong real-time performance, resulting in insufficient positioning accuracy and poor real-time performance of existing observation-level ROVs in high-precision and complex operation scenarios such as underwater short-distance (<100 meters) ROV collaborative operations, precise equipment docking, and narrow space detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of the preferred embodiments of the present invention shown in the accompanying drawings. The same reference numerals indicate the same parts throughout the accompanying drawings, and the drawings are not drawn to scale with actual size. The emphasis is on illustrating the subject matter of the present invention.

[0020] Figure 1 A schematic flow chart of an underwater vehicle positioning method based on ultra-wideband provided in an embodiment of the present invention; Figure 2 A schematic diagram of the principle of the two-way time-of-flight (TW-TOF) provided in an embodiment of the present invention; Figure 3 Based on Figure 2 Schematic diagram of the calculation principle. DETAILED DESCRIPTION

[0021] The technical solution of the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present invention and be able to implement it. However, the embodiments cited do not limit the present invention. In this embodiment, it should be understood that the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation of the present invention.

[0022] It should be noted that when an element is considered to be "connected" to another element, it can be directly connected to the other element and integrated with it, or there may be an intermediate element at the same time. The terms "installation", "one end", "the other end" and similar expressions used in the present invention are only for the purpose of illustration.

[0023] This embodiment provides an underwater robot positioning method based on ultra-wideband, as Figure 1 shown, including the following steps: S1. Build an ultra-wideband (UWB, Ultra-Wideband) positioning network. The positioning network includes at least four anchor nodes and at least one mobile node. Both the anchor nodes and the mobile nodes are configured with UWB communication modules; Among them, the anchor nodes are the positioning reference points and base stations. The four anchor nodes are respectively used as base stations for measuring the upper, lower, left, and right spatial distances of the mobile node to meet the needs of underwater positioning space; the mobile node can be various underwater devices to be positioned including robots.

[0024] S2. Adopt the two-way time of flight (TW-TOF) method for UWB communication in the positioning network to obtain the communication time difference between the mobile node and each anchor node; S3. Calculate the distances between the mobile node and each anchor node respectively according to each communication time difference and the propagation speed of electromagnetic waves in water when performing UWB communication; S4. Determine the spatial position of the mobile node according to each distance.

[0025] The embodiment of the present invention applies ultra-wideband technology to underwater positioning. By building an ultra-wideband (UWB) positioning network, it can support the dynamic access and collaborative positioning of multiple mobile nodes, effectively utilize the advantage of the fast propagation speed of UWB communication signals, greatly improve the real-time performance of underwater positioning, and achieve millisecond-level real-time response; By using a two-way time-of-flight (TW-TOF) method for UWB communication, the propagation delay error caused by the significant attenuation of electromagnetic waves by the water medium is eliminated. This not only ensures the transmission distance of UWB signals underwater, but also greatly improves the accuracy of ranging and positioning, achieving centimeter-level positioning accuracy (<10 cm), breaking the limitations of ultra-wideband technology in underwater applications. The positioning networking device of the present invention is composed of an anchor node and a mobile node equipped with a UWB communication module. It has a simple structure and does not require the deployment of other equipment. It supports multi-mobile node collaborative positioning through a networking protocol. It does not require additional maintenance during use, has high ease of use and economy, and can be applied to short distances or confined spaces underwater. This embodiment provides a novel underwater equipment positioning method that is highly adaptable to underwater environments and can achieve both short-range high precision and strong real-time performance. When used in underwater robots, this method can address the problem that existing conventional positioning methods cannot achieve both short-range high precision and strong real-time performance. This leads to insufficient positioning accuracy and poor real-time performance of existing observation-level ROVs in high-precision and complex operation scenarios such as short-range (especially less than 100 meters) ROV collaborative operations, precise equipment docking, and confined space detection underwater.

[0026] In a preferred embodiment, when the number of mobile nodes in the current positioning round is more than two, step S2 further includes: S5. Define one of the mobile nodes as the current mobile node and the other mobile nodes as waiting mobile nodes. S6. Control the current mobile node to perform UWB communication with each anchor node to obtain the communication time difference, complete steps S3 and S4, and then proceed to step S7; S7, defining one of the waiting mobile nodes as a new current mobile node, and then instructing the new current mobile node to execute step S6 until the spatial positions of all mobile nodes in this round of positioning are obtained; S8. End the positioning of this round.

[0027] The method of this embodiment provides communication rules between each mobile node and the anchor node when the number of mobile nodes is more than two, that is, only a single mobile node is allowed to communicate with each anchor node separately via UWB within a certain time period to complete positioning. This avoids communication confusion or congestion, and ensures communication efficiency and the timeliness and effectiveness of positioning.

[0028] In another preferred embodiment, Figure 2 and Figure 3 As shown in Figure 2, the mobile node and the anchor node obtain the communication time difference through at least three signal interactions during UWB communication. in, Figure 2 The Device in the module represents the UWB module.round represents the time for one round of signal reception and transmission; T reply represents the time used by the receiving party to process the received signal and then send a signal to the other party; T prop represents the time for the transmitted signal to be transmitted and propagated (i.e., the time of flight); Specifically, the content of the at least three signal interactions described above includes: Step1: The anchor node first sends a first signal to the mobile node and records the transmission timestamp as , and the mobile node receives the first signal and records the reception timestamp as ; Step2: After processing, the mobile node sends a first response signal to the anchor node and records the transmission timestamp as , and the anchor node receives the first response signal and records the reception timestamp as ; Step3: The anchor node sends a second signal to the mobile node and records the transmission timestamp as , and the mobile node receives the second signal and records the reception timestamp as ; Then, the time of flight ;

[0029] Among them, parameter , , , ; So, the actual time of flight , and the actual time of flight is the communication time difference; The distance between the mobile node and the anchor node .

[0030] Among them, represents the propagation speed of electromagnetic waves underwater, which can be directly obtained according to existing relevant physical standards. Both the first signal and the first response signal are message signals that are not important for the content. The second signal records the transmission timestamp , and the reception timestamp , so that in Step3, the mobile node will obtain six timestamps.

[0031] In this embodiment, through three UWB communications between the mobile node and the anchor node, the measurement error caused by different signal processing delays of the devices during UWB communication can be eliminated, the accuracy of time measurement can be improved, and high-precision distance measurement can be achieved.

[0032] It should be noted that both the anchor node and the mobile node perform signal interaction through their respective configured UWB communication modules. In addition, the signal interaction can also be more than three times, such as four times, etc., but the distance calculation method can still adopt the above method.

[0033] In another preferred embodiment, in step S1, when the number of anchor nodes exceeds four, it further includes defining a dynamic ad hoc network protocol to achieve the autonomous switching of anchor nodes. In this way, when an anchor node fails, a neighboring anchor node can be dynamically upgraded to a temporary anchor point, avoiding the state of unable to locate or inaccurate positioning.

[0034] In another preferred embodiment, lightweight time division multiple access (TDMA) scheduling is adopted between the devices for positioning networking to reduce underwater communication conflicts and energy consumption.

[0035] In another preferred embodiment, in UWB communication, the received signal is processed by pulse shaping technology to optimize the UWB signal spectrum, match the underwater channel characteristics, and reduce the attenuation effect of the water medium on the electromagnetic wave signal.

[0036] In another preferred embodiment, in UWB communication, the carrier frequency of the transmitted signal is switched according to the changes in water depth and / or salinity, so that the carrier frequency of the transmitted signal adapts to the changes in the underwater environment; the carrier frequency can be roughly divided into a high-frequency band and a low-frequency band. The high-frequency band range is approximately 3 to 5 GHz and is used for short-distance high-precision measurement, while the low-frequency band is mainly used to expand the coverage area.

[0037] Specifically, when the water depth increases and / or the salinity increases, the carrier frequency of the transmitted signal is reduced, and a UWB communication is initiated with the reduced carrier frequency; When the water depth decreases and / or the salinity decreases, the carrier frequency of the transmitted signal is increased, and a UWB communication is initiated with the increased carrier frequency; When the water depth and / or salinity remain unchanged, the carrier frequency of the transmitted signal is maintained unchanged, and a UWB communication is initiated with the current carrier frequency.

[0038] It should be noted that the transmitted signal and the received signal in the above embodiments refer to the same UWB communication.

[0039] In a further preferred embodiment, in UWB communication, for the complex propagation path and reflection environment underwater, an improved multipath suppression algorithm (RAKE receiver combined with machine learning environment feature recognition) is introduced to process the received signal; The improvement includes adjusting the transmission intensity parameter in the multipath suppression algorithm according to the ocean environment, usually the ocean environment with a depth of more than 1000 meters, which can make the algorithm more obvious in suppressing the multipath reflection of radio waves propagating in seawater and improve the ranging stability of the method in this embodiment in a complex reflection environment.

[0040] In this specification, unless otherwise clearly specified or limited, a first feature being "on" or "under" a second feature may mean that the first and second features are in direct contact, or that the first and second features are indirectly in contact via an intermediate medium. Moreover, a first feature being "above", "over" and "on top of" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature has a higher level of height than the second feature. A first feature being "under", "below" and "beneath" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature has a lower level of height than the second feature.

[0041] In the description of this specification, the description with reference to terms such as "preferred embodiment", "another embodiment", "other embodiments" or "specific examples" means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples.

[0042] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present application. Those of ordinary skill in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present application.

Claims

1. An underwater robot positioning method based on ultra-wideband, characterized in that, Including the following steps: S1. Construct a Ultra-Wideband (UWB) positioning network. The positioning network includes at least four anchor nodes and at least one mobile node, and both the anchor nodes and the mobile nodes are configured with UWB communication modules; S2. In the positioning network, use the Two-Way Time-of-Flight (TW-TOF) method for UWB communication to obtain the communication time differences between the mobile node and each of the anchor nodes; S3. According to each of the communication time differences and the propagation speed of electromagnetic waves in water during the UWB communication, calculate the distances between the mobile node and each of the anchor nodes respectively; S4. Determine the spatial position of the mobile node according to each of the distances.

2. The method according to claim 1, characterized in that, When the number of the mobile nodes in this round of positioning is more than two, in step S2, it further includes: S5. Define one of the mobile nodes as the current mobile node, and the other mobile nodes as waiting mobile nodes; S6. Control the current mobile node to perform the UWB communication with each of the anchor nodes to obtain the communication time differences, and complete steps S3 and S4, then enter step S7; S7. Define one of the waiting mobile nodes as the new current mobile node, and then command the new current mobile node to execute step S6 until the spatial positions of all the mobile nodes in this round of positioning are obtained; S8. End this round of positioning.

3. The method according to claim 1, wherein: The mobile node and the anchor nodes obtain the communication time differences through at least three signal interactions during the UWB communication.

4. The method according to claim 3, characterized in that, The content of the at least three signal interactions includes: Step 1. The anchor node first sends a first signal to the mobile node and records the transmission timestamp as , and the mobile node receives the first signal and records the reception timestamp as ; Step 2, the mobile node processes and sends a first response signal to the anchor node, and records the transmission timestamp as , the anchor node receives the first response signal and records the reception timestamp as ; Step 3. The anchor node sends a second signal to the mobile node and records the transmission timestamp as , and the mobile node receives the second signal and records the reception timestamp as ; Then, the flight time ; Among them, , , , ; So, the actual flight time ; The distance between the mobile node and the anchor node .

5. The method according to claim 1, characterized in that: In step S1, when the number of the anchor nodes exceeds four, it further includes defining a dynamic self-organizing network protocol to achieve the autonomous switching of the anchor nodes.

6. The method according to claim 1, characterized in that: Lightweight Time Division Multiple Access (TDMA) scheduling is adopted between the devices of the positioning network.

7. The method according to claim 1, wherein: In the UWB communication, the received signal is processed by pulse shaping technology.

8. The method according to claim 1, wherein: In the UWB communication, the carrier frequency of the transmitted signal is switched according to the changes in water depth and / or salinity.

9. The method according to claim 8, wherein: When the water depth increases and / or the salinity increases, lower the carrier frequency of the transmitted signal, and initiate a UWB communication with the lowered carrier frequency; When the water depth decreases and / or the salinity decreases, raise the carrier frequency of the transmitted signal, and initiate a UWB communication with the raised carrier frequency; When the water depth and / or the salinity remain unchanged, keep the carrier frequency of the transmitted signal unchanged, and initiate a UWB communication with the current carrier frequency.

10. The method according to claim 1 or 7, characterized in that: In the UWB communication, an improved multipath suppression algorithm is introduced to process the received signal; The improvement includes adjusting the transmission intensity parameter in the multipath suppression algorithm according to the ocean environment.

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