Leased forklift asset location tracking method and system

Abstract

The application provides a rental forklift asset position tracking method and system. Each forklift broadcasts satellite positioning quality factor and absolute position coordinates, and the number of communicable neighbors whose satellite positioning quality does not meet the standard in the current statistical time window is used to represent the node connectivity to conduct distributed election of direct positioning nodes, relay positioning nodes and nodes to be positioned. The level of the direct positioning node is zero; the relay positioning node only broadcasts valid coordinates after successful calculation using at least three positioned nodes, and the level thereof is one more than the maximum level of the used nodes. The node to be positioned selects at least three reference nodes with a level not exceeding an upper limit to complete ranging and position calculation, reduces the ranging calculation weight with the increase of the level of the reference node, and increases the observation noise covariance of inertial fusion according to the maximum level, to obtain a fusion positioning result. The scheme can reduce the influence of the propagation of the relay position uncertainty along the cooperative positioning link on the forklift position tracking result.

Description

Technical Field

[0001] This application relates to the field of location tracking technology, and more specifically, to a method and system for tracking the location of leased forklift assets. Background Technology

[0002] Position tracking refers to converting discrete spatiotemporal observation data of a target object in physical space into a spatiotemporally continuous motion trajectory through signal observation and data processing. Its core challenge lies in balancing the contradiction between accuracy, cost, and environmental universality.

[0003] In existing forklift asset location tracking, pre-deploying fixed positioning base stations is not well-suited to the working conditions of forklifts moving between different rental sites, while obstructions such as metal racks can prevent some forklifts from continuously obtaining usable satellite positioning solutions. When using mobile forklifts as step-by-step positioning references, if relay nodes participate in downstream positioning before completing their own position calculations, or if downstream calculations do not distinguish between the uncertainties of direct positioning coordinates and step-by-step calculated coordinates, relay position errors will be carried over into subsequent ranging calculations and fusion. Therefore, existing solutions struggle to simultaneously satisfy both positioning coverage under conditions without fixed infrastructure and constraints on the propagation of relay position uncertainties. Summary of the Invention

[0004] This application provides a method and system for tracking the location of leased forklift assets, which can reduce the impact of relay location uncertainty propagating along the cooperative positioning link on the forklift location tracking results.

[0005] Firstly, this application provides a method for tracking the location of leased forklift assets, including: Deploy an inter-vehicle ranging self-organizing network module on each forklift, and broadcast the satellite positioning quality factor and absolute position coordinates to each forklift; Each forklift calculates node connectivity based on the satellite positioning quality factor of surrounding forklifts. The node connectivity is the number of surrounding forklifts that meet the signal reception quality requirements but whose satellite positioning quality does not meet the preset positioning quality requirements within the current statistical time window. Each forklift is selected in a distributed manner based on satellite positioning quality factors and node connectivity: those with valid satellite positioning solutions and positioning quality that meet the preset positioning quality requirements are direct positioning nodes; those that have been successfully distanced and solved by at least three surrounding nodes that already carry valid absolute position coordinates are relay positioning nodes; the rest are nodes to be positioned. The relay level of direct positioning nodes is zero, and the relay level of relay positioning nodes is the maximum relay level of the nodes used plus one. After successful solution, the valid coordinates are broadcast. The node to be located selects at least three reference nodes from direct positioning nodes or relay positioning nodes whose absolute position coordinates are valid and whose relay level is not higher than the preset maximum relay level. The relative distance set is obtained by measuring the distance between vehicles, and the absolute position coordinates and relay level of each reference node are received. The node to be located calculates its own absolute position based on the relative distance set and absolute position coordinates after time synchronization. The corresponding ranging calculation weight is reduced according to the relay level of the reference node. The observation noise covariance of inertial fusion is increased according to the largest relay level participating in the calculation, using its own absolute position as the observation. The fusion positioning result is obtained.

[0006] In some embodiments, the statistical node connectivity of each forklift based on the satellite positioning quality factor of surrounding forklifts specifically includes: Extract the satellite positioning quality factor corresponding to each surrounding forklift from the locally maintained neighbor information table; Based on the timestamps of the corresponding records of each surrounding forklift in the neighbor information table, the valid neighbor records within the current statistical time window are determined. The node connectivity is obtained by counting the records in the effective neighbor records that meet the signal reception quality requirements but whose satellite positioning quality factors do not meet the preset positioning quality requirements.

[0007] In some embodiments, the distributed election of each forklift based on satellite positioning quality factor and node connectivity specifically includes: For each forklift, obtain its own satellite positioning quality factor and the connectivity of the node; Based on the satellite positioning quality factor and the node connectivity, calculate the election score of this forklift as a reference node; Based on the election score and the surrounding forklift role perception results obtained by this forklift from receiving broadcast messages from surrounding forklifts, the election role of this forklift is determined. Mark this forklift as a direct positioning node, a relay positioning node, or a node to be positioned.

[0008] In some embodiments, the node to be located selects at least three reference nodes from direct positioning nodes or relay positioning nodes whose absolute position coordinates are valid and whose relay level is not higher than a preset maximum relay level, performs inter-vehicle ranging to obtain a relative distance set, and receives the absolute position coordinates and relay level of each reference node, specifically including: From the direct positioning nodes or relay positioning nodes whose absolute position coordinates perceived by this forklift are valid and whose relay level is not higher than the preset maximum relay level, select at least three reference nodes whose spatial geometric distribution meets the requirements for planar position calculation. Vehicle-to-vehicle distance measurements are performed with the selected reference nodes to obtain a set of relative distances containing the relative distances between each selected reference node; Receive the absolute position coordinates and relay level from each selected reference node.

[0009] In some embodiments, the node to be located calculates its absolute position based on the time-synchronized relative distance set and absolute position coordinates, and the reduction of the corresponding ranging calculation weight according to the relay level of the reference node specifically includes: Obtain the absolute position coordinates, relay level, relative distance corresponding to the relative distance set of each reference node that has completed time synchronization, and the received signal strength indication corresponding to the relative distance; Based on the absolute position coordinates and corresponding relative distances of each reference node, a set of distance observation equations is constructed with the position of the node to be located as the unknown. The distance observation equations are linearized, and a weighted matrix based on the received signal strength indication and the relay level of the reference node is introduced, wherein the higher the relay level, the lower the corresponding weight. The absolute position of the node to be located is obtained by solving the weighted least squares method.

[0010] In some embodiments, the observation noise covariance of inertial fusion is increased according to the maximum relay level involved in the calculation to obtain the fused positioning result, specifically including: Obtain the recursive position result of the inertial measurement unit of the node to be located at the current solution time; The observation noise covariance of the Kalman filter is set according to the maximum relay level involved in the solution. The higher the maximum relay level, the larger the observation noise covariance. The measurement update process of the Kalman filter is performed with the absolute position as the observation and the recursive result of the position as the state prediction, to obtain the fused position-state vector. The final position coordinates of the node to be located are extracted from the fused position state vector and used as the fused positioning result.

[0011] In some embodiments, the self-organizing network module is an on-board communication device integrated on the forklift that can realize direct distance measurement and data exchange between vehicles without relying on external fixed communication infrastructure.

[0012] Secondly, this application provides a location tracking system for leased forklift assets, comprising: The broadcast module is used to deploy an ad hoc network module for inter-vehicle ranging on each forklift, and each forklift broadcasts its satellite positioning quality factor and absolute position coordinates. The processing module is used to calculate the node connectivity of each forklift based on the satellite positioning quality factor of the surrounding forklifts. The node connectivity is the number of surrounding forklifts that meet the signal reception quality requirements but whose satellite positioning quality does not meet the preset positioning quality requirements within the current statistical time window. The processing module is also used for distributed election of each forklift based on satellite positioning quality factor and node connectivity: those with valid satellite positioning solutions and positioning quality that meet the preset positioning quality requirements are direct positioning nodes; those that have been successfully distanced and solved by at least three surrounding nodes that have carried valid absolute position coordinates are relay positioning nodes; the rest are nodes to be positioned; the relay level of direct positioning nodes is zero; the relay level of relay positioning nodes is the maximum relay level of the nodes used plus one; and the valid coordinates are broadcast after successful solution. The processing module is also used to select at least three reference nodes from direct positioning nodes or relay positioning nodes whose absolute position coordinates are valid and whose relay level is not higher than the preset maximum relay level, perform inter-vehicle distance measurement to obtain a relative distance set, and receive the absolute position coordinates and relay level of each reference node. The execution module is used to calculate the absolute position of the node to be located based on the relative distance set and absolute position coordinates after time synchronization, reduce the corresponding ranging calculation weight according to the relay level of the reference node, and increase the observation noise covariance of inertial fusion according to the absolute position of the node to be located and the maximum relay level involved in the calculation, so as to obtain the fused positioning result.

[0013] Thirdly, this application provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the above-described method.

[0014] Fourthly, this application provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the above-described method.

[0015] The technical solutions provided by the embodiments disclosed in this application have the following beneficial effects: This application provides a method and system for tracking the location of leased forklift assets. Node connectivity is determined by the number of neighbors within the current statistical time window that meet reception quality requirements but whose satellite positioning quality does not meet preset requirements. This ensures that the election score simultaneously reflects the forklift's own satellite positioning conditions and the range of neighboring units available for positioning. Relay positioning nodes only broadcast valid absolute position coordinates after completing ranging and position calculations using at least three already positioned nodes. Direct positioning nodes have a level of zero, while relay positioning nodes have a level equal to or greater than the maximum level of the nodes used, and are subject to a preset maximum level limit. Therefore, nodes that have not yet been calculated will not enter the cooperative positioning link, and the referencing relationship expands unidirectionally according to the level. During the calculation process, the ranging calculation weight of the node to be positioned decreases as the reference node level increases, and the observation noise covariance of the inertial fusion is increased according to the maximum level participating in the calculation. If there are fewer than three reference nodes, the previous fusion result is maintained and recursively applied using inertial measurement units, and the node re-participates in the election in the next cycle. Thus, this method eliminates the need for pre-set fixed positioning base stations and reduces the impact of relay position uncertainty propagating along the cooperative positioning link on the forklift location tracking results. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating a method for tracking the location of leased forklift assets according to some embodiments of this application; Figure 2 This is a flowchart illustrating the process of determining node connectivity according to some embodiments of this application; Figure 3 This is a schematic diagram of the structure of a leased forklift asset location tracking system according to some embodiments of this application; Figure 4 This is an internal structural diagram of a computer device for implementing a method for tracking the location of leased forklift assets, according to some embodiments of this application. Detailed Implementation

[0017] To better understand the technical solutions in this embodiment, the technical solutions in this embodiment will be described in detail below with reference to the accompanying drawings and specific implementation methods.

[0018] refer to Figure 1 The figure is a flowchart illustrating a method for tracking the location of leased forklift assets according to some embodiments of this application. The method for tracking the location of leased forklift assets mainly includes the following steps: In step 101, an inter-vehicle ranging self-organizing network module is deployed on each forklift, and each forklift broadcasts its satellite positioning quality factor and absolute position coordinates.

[0019] In practice, each forklift is equipped with an ad hoc network module integrating an ultra-wideband ranging chip and a satellite positioning receiver module. This ad hoc network module has both nanosecond-level pulse time-of-flight ranging capability and multi-constellation satellite signal reception capability. After the forklift is powered on, the ad hoc network module autonomously generates and sends broadcast messages at a preset fixed period, typically once per second. Each broadcast message contains at least the following information fields: firstly, a satellite positioning quality factor characterizing the reliability of the forklift's current satellite positioning result. Specifically, this can be a positioning quality score calculated from the position accuracy attenuation factor, where a larger value indicates better satellite positioning quality, or a quality grading value mapped from the positioning solution type flag. Both values ​​increase as the satellite positioning quality improves. Secondly, the absolute positioning quality calculated by the forklift based on the satellite signal is... The location coordinates, which are absolute location coordinates expressed in longitude, latitude, elevation or converted local plane coordinates, are accompanied by a Coordinated Universal Time (UTC) timestamp. While sending its own broadcast, each forklift continuously listens for similar broadcast messages from surrounding forklifts and records the forklift identifier, satellite positioning quality factor, absolute location coordinates, role enumeration value (described later), election score and relay level, received signal strength indication, and reception time in its local neighbor information table. For forklifts that have not yet obtained a valid satellite positioning solution, the satellite positioning quality factor field in their broadcast message is filled with a conventional value indicating that satellite positioning is unavailable, and the absolute location coordinate field is set to an invalid flag until the forklift's own absolute position is subsequently calculated. The receiver does not use records carrying this invalid flag as the location source of the reference node.

[0020] It should be noted that the self-organizing network module described in this application is an on-board communication device that is integrated on the forklift and can realize direct distance measurement and data exchange between vehicles without relying on external fixed communication infrastructure; its distance measurement function is based on the time-of-flight principle of ultra-wideband signals, and the relative distance between vehicles is observed based on the round-trip propagation time of the pulse between the transmitter and receiver; the satellite positioning quality factor is a quantitative indicator that measures the usability of the forklift's own position coordinates calculated by receiving global navigation satellite signals, and can be used to distinguish whether the current satellite positioning solution meets the preset positioning quality requirements; the absolute position coordinates refer to the spatial position expression of the forklift in a global or local geodetic coordinate system with the Earth as a reference, providing a unified spatial reference for each node; the broadcast refers to the operation of each forklift periodically sending its own positioning-related information to surrounding reachable forklifts in a connectionless manner through the self-organizing network wireless channel, and each broadcast message includes the sending time and positioning data.

[0021] In step 102, each forklift calculates node connectivity based on the satellite positioning quality factor of surrounding forklifts. The node connectivity is the number of surrounding forklifts that meet the signal reception quality requirements but whose satellite positioning quality does not meet the preset positioning quality requirements within the current statistical time window.

[0022] In some embodiments, reference Figure 2 As shown in the figure, this is a schematic flowchart illustrating the process of determining node connectivity in some embodiments of this application. The following steps can be used to calculate the node connectivity of each forklift based on the satellite positioning quality factor of surrounding forklifts: In step 1021, the satellite positioning quality factor corresponding to each surrounding forklift is extracted from the locally maintained neighbor information table; In step 1022, based on the timestamps of the corresponding records of each surrounding forklift in the neighbor information table, the valid neighbor records within the current statistical time window are determined; In step 1023, the records in the effective neighbor records that meet the signal reception quality requirements and whose satellite positioning quality factors do not meet the preset positioning quality requirements are counted to obtain the node connectivity.

[0023] Here, the forklift traverses all currently stored records in the neighbor information table, reads the satellite positioning quality factor field corresponding to the identifiers of each surrounding forklift in each record, and extracts and organizes the forklift identifiers and satellite positioning quality factors in a pairwise association form into a set of quality factors to be processed. The satellite positioning quality factors are derived from the messages periodically broadcast by each surrounding forklift in the aforementioned steps.

[0024] In a specific implementation, based on the timestamps of the corresponding records of surrounding forklifts in the neighbor information table, determining the valid neighbor records within the current statistical time window can further include: using the current system time of this forklift as a benchmark, tracing back a preset statistical time span to define the start and end times of the current statistical time window; then, traversing the records in the neighbor information table to determine whether the receiving time carried by each record is within the window defined by the start and end times; if so, the record is marked as a valid neighbor record; otherwise, it is considered an outdated record outside the window and removed from the current statistics. The value of the statistical time span determines the balance between the sensitivity of network topology change perception and the stability of connectivity statistics; those skilled in the art can adjust the specific value of this time span according to the specific working conditions of the leased site, and this application does not limit this.

[0025] In a specific implementation, the node connectivity is obtained by counting records among the effective neighbor records that meet the signal reception quality requirements but whose satellite positioning quality factors do not meet the preset positioning quality requirements. This can further include: first, extracting the received signal strength indicator (RSI) from each effective neighbor record to characterize the signal quality; second, comparing the RSI with the preset signal reception quality requirements; identifying records with RSIs better than the preset requirements as reliable neighbor records, and removing records with poor reception quality due to signal attenuation or multipath interference; finally, deduplicating the selected reliable neighbor records according to their source forklift identifier, and... After deduplication, based on the satellite positioning quality factors of the surrounding forklifts carried by each record, records whose satellite positioning quality factors already meet the preset positioning quality requirements, i.e., the surrounding forklifts themselves can directly obtain a usable satellite positioning solution, are removed. The count results of the remaining records are used as the node connectivity statistics value within the current statistical time window. The node connectivity quantitatively reflects the scale of neighbors that this forklift can maintain a stable communication connection in the ad hoc network, and that it cannot directly obtain a usable satellite positioning solution itself. In other words, it is the scale of objects that this forklift can provide positioning reference for once it assumes the role of a reference node, which is used to measure the network topology value of each forklift in the subsequent distributed election process.

[0026] In step 103, each forklift undergoes a distributed election based on satellite positioning quality factors and node connectivity: those with valid satellite positioning solutions and whose positioning quality meets the preset positioning quality requirements are direct positioning nodes; those that have been successfully distanced and solved by at least three surrounding nodes carrying valid absolute position coordinates are relay positioning nodes; and the rest are nodes to be positioned. The relay level of direct positioning nodes is zero, and the relay level of relay positioning nodes is the maximum relay level of the nodes used plus one. Valid coordinates are broadcast only after successful solution.

[0027] In some embodiments, the distributed election of forklifts based on satellite positioning quality factors and node connectivity can be achieved through the following steps: For each forklift, obtain its own satellite positioning quality factor and the connectivity of the node; Based on the satellite positioning quality factor and the node connectivity, calculate the election score of this forklift as a reference node; Based on the election score and the surrounding forklift role perception results obtained by this forklift from receiving broadcast messages from surrounding forklifts, the election role of this forklift is determined. Mark this forklift as a direct positioning node, a relay positioning node, or a node to be positioned.

[0028] In this embodiment, the selection score of the forklift as a reference node based on the satellite positioning quality factor and the node connectivity can be achieved in the following way: The satellite positioning quality factor is mapped to a positioning capability component, where a higher satellite positioning quality factor results in a higher positioning capability component. Simultaneously, the node connectivity is mapped to a coverage capability component, where a higher connectivity value results in a higher coverage capability component. Both the positioning capability component and the coverage capability component are dimensionless quantities normalized to the same preset value range. After assigning corresponding dimensionless weight coefficients to the positioning capability component and the coverage capability component, a weighted sum is performed to obtain the score for the forklift. Election scoring; wherein, the election score comprehensively reflects the suitability of the signal conditions of the forklift as a positioning reference source and the scale of the object to be positioned within its one-hop range; wherein, the relative magnitude of the weight coefficients determines whether the selection focuses on positioning quality or coverage of the object to be positioned. Those skilled in the art can adjust the values ​​of the two sets of weight coefficients according to the degree of satellite signal obstruction and forklift distribution density at the site where the rental fleet is located. In sites with severe satellite signal obstruction, the weight of the positioning capability component can be increased to ensure the accuracy of the reference source. In sites where forklifts are more dispersed in satellite blind zones, the weight of the coverage capability component can be increased to enable the selected reference node to cover more objects to be positioned.

[0029] Specifically, the forklift's election role is determined by checking whether its own satellite positioning receiver module outputs a valid satellite positioning solution and whether the satellite positioning quality factor meets the preset positioning quality requirements. If both are met, the forklift will initially be considered a direct positioning node candidate. If the forklift does not meet the conditions for a direct positioning node, it will check whether there are any forklifts marked as direct positioning nodes or relay positioning nodes in the surrounding area based on the broadcast messages received from surrounding forklifts in the neighbor information table. The forklift must have at least three forklifts marked as direct positioning nodes and relay positioning nodes that have confirmed their positions in its surrounding area, and its node connectivity must not be zero, meaning there are forklifts marked as direct positioning nodes in its surrounding area. When a forklift requires a positioning reference, it is initially identified as a candidate for a relay positioning node. If there are at least three reference nodes around the forklift but their connectivity is zero, the forklift is not considered a candidate for a relay positioning node but is initially identified as a node to be positioned. If the forklift does not meet the conditions for a direct positioning node or a relay positioning node, it is initially identified as a node to be positioned. After being initially identified as a candidate for a direct positioning node or a relay positioning node, the forklift's election score is compared with the election scores of surrounding candidate forklifts of the same type. The forklifts are ranked from highest to lowest election score within the local competition area. Before the number of identified reference nodes reaches a preset upper limit, the top-ranked candidate forklifts are sequentially designated as the corresponding direct positioning nodes or relay positioning nodes. The number of identified reference nodes within the local competition range must not be less than a preset minimum number of reference nodes. Only when the number of identified reference nodes within the local competition range reaches the preset upper limit, and the forklift's election score ranking is outside this upper limit, is the forklift downgraded to a node awaiting positioning. The minimum number of reference nodes is not less than three and not greater than the upper limit. Among the forklifts downgraded to nodes awaiting positioning, those that can still output satellite positioning solutions that meet the preset positioning quality requirements are preferred. The satellite positioning solution is used as the local positioning output, and the cooperative positioning solution is no longer used to replace the satellite positioning solution. The local competition range of the direct positioning node is defined as all candidate forklifts of the direct positioning node within its own communication one-hop range, and the local competition range of the relay positioning node is defined as all candidate forklifts of the relay positioning node within the coverage range of the forklifts that have been identified as direct positioning nodes within its own communication one-hop range. This application uses an election scoring competition mechanism constrained by the minimum and maximum number of reference nodes to ensure that the same local area retains a sufficient number of reference nodes to support the positioning node to complete the position calculation, while avoiding the communication overhead and positioning interference caused by excessive redundancy of reference nodes.

[0030] During implementation, after the forklift determines its elected role, it updates the role status variable maintained internally to the corresponding role enumeration value. This role enumeration value includes at least three possible values: direct positioning node, relay positioning node, and node to be positioned. After the role status variable is updated, in the next broadcast cycle, the forklift appends the role enumeration value and its election score as new information fields to the broadcast message, allowing surrounding forklifts to perceive the forklift's role and election score by receiving the broadcast message. If the forklift is marked as a relay positioning node, it selects at least three nodes from the surrounding direct or relay positioning nodes that already carry valid absolute position coordinates to perform inter-vehicle distance measurement and position calculation. Only after successfully calculating its own absolute position does the forklift carry these coordinates in subsequent broadcast messages and assume relay functions. The broadcast message also carries the relay level. The relay level of the directly located node is zero, and the relay level of the relay location node is the maximum relay level of all nodes used in this round plus one. If the calculated relay level exceeds the preset maximum relay level, the calculated coordinates will not be broadcast in this round and the node will not assume relay functions. Since all nodes participating in the calculation already carry valid absolute position coordinates, and their levels are lower than the forklift level determined by this calculation, the collaborative positioning reference relationship is expanded unidirectionally by level to avoid two nodes that have not yet completed their position calculations using each other as position references.

[0031] In step 104, the node to be located selects at least three reference nodes from direct positioning nodes or relay positioning nodes whose absolute position coordinates are valid and whose relay level is not higher than the preset maximum relay level. The node performs inter-vehicle distance measurement to obtain a relative distance set and receives the absolute position coordinates and relay level of each reference node.

[0032] In some embodiments, the node to be located selects at least three reference nodes from direct positioning nodes or relay positioning nodes whose absolute position coordinates are valid and whose relay level is not higher than a preset maximum relay level, performs inter-vehicle ranging to obtain a relative distance set, and receives the absolute position coordinates and relay level of each reference node. This can be achieved by the following steps: From the direct positioning nodes or relay positioning nodes whose absolute position coordinates perceived by this forklift are valid and whose relay level is not higher than the preset maximum relay level, select at least three reference nodes whose spatial geometric distribution meets the requirements for planar position calculation. Vehicle-to-vehicle distance measurements are performed with the selected reference nodes to obtain a set of relative distances containing the relative distances between each selected reference node; Receive the absolute position coordinates and relay level from each selected reference node.

[0033] During implementation, the node to be located traverses the broadcast messages of surrounding forklifts recorded in the neighbor information table, filtering forklift entries marked as direct positioning nodes or relay positioning nodes in the role information field to form a candidate reference node set. When the number of nodes in the candidate reference node set is not less than three, the candidate reference nodes are sorted in descending order of received signal strength, prioritizing the selection of several nodes with the highest received signal strength as ranging objects. Simultaneously, the spatial geometric distribution of the candidate reference nodes is considered during the selection process, prioritizing nodes distributed in different directions of the forklift to form a reference node combination beneficial for subsequent position calculation. If the candidate reference node set includes relay positioning nodes and direct positioning nodes with confirmed positions, the direct positioning nodes are prioritized as reference nodes. If the number of direct positioning nodes is less than three, relay positioning nodes are used to supplement to at least three. The candidate reference node set only includes forklifts whose most recent broadcast message carries valid absolute position coordinates, and includes forklifts whose role information field has been marked as relay positioning nodes but are not yet... Forklifts without valid absolute position coordinates are eliminated, and the relay levels of the selected reference nodes do not exceed the preset maximum relay level. Within the same relay level, selection is based on the aforementioned received signal strength indication and spatial geometric distribution rules. The spatial geometric distribution meeting the planar position calculation requirements means that at least three selected reference nodes are not located on the same straight line, and the interior angles of the triangle formed by any three selected reference nodes are not less than the preset minimum interior angle threshold. Reference node combinations that do not meet this condition are eliminated and selected again according to the above sorting. When the number of nodes in the candidate reference node set is less than three after elimination according to the above rules, position calculation is not performed in this round. The node to be positioned maintains the position result output by the previous fusion cycle and only updates its own position recursively using the inertial measurement unit. At the same time, it re-participates in the role election in the next broadcast cycle. If the forklift does not yet have the position result output by the previous fusion cycle, the satellite positioning solution that most recently met the preset positioning quality requirements of the forklift, or the preset initial position at the site entrance, is used as the starting position reference for the inertial measurement unit recursion.

[0034] In a specific implementation, vehicle-to-vehicle distance measurement is performed with selected reference nodes to obtain a relative distance set containing the relative distances between the vehicle and each selected reference node. This can further include: the node to be located sequentially initiating a bilateral two-way ranging process to each selected reference node. This process involves the node to be located sending a ranging request message to the reference node, the reference node responding with a ranging response message, and the node to be located sending a ranging confirmation message after receiving the response message. Upon receiving the confirmation message, the reference node sends its recorded sending and receiving timestamps back to the node to be located via a ranging result message. The node to be located obtains two round-trip times and two response delays based on its own sending and receiving timestamps and the received sending and receiving timestamps from the other end, recorded during the three message interactions. The response delays are measured using the timestamps recorded by both the sender and receiver and do not need to be fixed values. Then, based on the time combination relationship of the bilateral two-way ranging, the node to be located calculates the ultra-wideband signal at the location of the target node using the two round-trip times and the two response delays. The one-way flight time between the positioning node and the reference node is used to offset the impact of the local clock frequency deviation between the transmitting and receiving parties on the flight time estimation. The one-way flight time is multiplied by the electromagnetic wave propagation speed to obtain the relative distance between the two nodes. After the positioning node completes the bilateral two-way ranging process with all selected reference nodes, all ranging results are summarized into a relative distance set. Each distance record in the relative distance set is associated with the corresponding reference node identifier, distance value, and received signal strength indication and first path detection confidence level used to characterize the signal quality of this ranging. Among them, for ranging results caused by non-line-of-sight propagation due to temporary obstruction between forklifts, the additional time delay deviation caused by non-line-of-sight propagation is estimated by jointly estimating the additional time delay deviation of this ranging using the first path detection confidence level and received signal strength indication. The distance corresponding to the additional time delay deviation is subtracted from the relative distance to complete the error compensation correction. The compensated relative distance and the original relative distance before compensation are included in the relative distance set and marked for subsequent calculation and anomaly investigation.

[0035] In this embodiment, while performing the ranging process with each selected reference node, the node to be located extracts the absolute position coordinates and corresponding Coordinated Universal Time timestamp carried in the most recent broadcast message of each selected reference node from the neighbor information table; if the absolute position coordinates of a selected reference node have been transmitted back in the ranging result message, the absolute position coordinates carried in the ranging result message are used as the standard for updating; the node to be located associates the absolute position coordinates of each selected reference node with the corresponding distance record in the relative distance set to ensure that each relative distance record matches the absolute position coordinates of the corresponding reference node.

[0036] In step 105, the node to be located calculates its own absolute position based on the relative distance set and absolute position coordinates after time synchronization, reduces the corresponding ranging calculation weight according to the relay level of the reference node, and increases the observation noise covariance of inertial fusion according to the largest relay level involved in the calculation, using its own absolute position as the observation, to obtain the fused positioning result.

[0037] In some embodiments, the node to be located calculates its absolute position based on the time-synchronized relative distance set and absolute position coordinates, and reduces the corresponding ranging calculation weight according to the relay level of the reference node, which can be achieved by the following steps: Obtain the absolute position coordinates, relay level, relative distance corresponding to the relative distance set of each reference node that has completed time synchronization, and the received signal strength indication corresponding to the relative distance; Based on the absolute position coordinates and corresponding relative distances of each reference node, a set of distance observation equations is constructed with the position of the node to be located as the unknown. The distance observation equations are linearized, and a weighted matrix based on the received signal strength indication and the relay level of the reference node is introduced, wherein the higher the relay level, the lower the corresponding weight. The absolute position of the node to be located is obtained by solving the weighted least squares method.

[0038] In practice, during the reception of the absolute position coordinates of each selected reference node, the reference node with the strongest signal is used as the master time node. The node to be located estimates the clock deviation relative to the master time node based on the timestamped messages exchanged with each reference node, and converts the timestamps attached to the absolute position coordinates of each reference node to the same clock reference. The transmit and receive timestamps generated by bilateral bidirectional ranging are used to associate the relative distance record with the corresponding measurement time. After completing the timestamp reference conversion, the absolute position coordinates of each reference node are extrapolated to the current calculation time based on the time difference between the timestamp attached to the absolute position coordinates of each reference node and the current calculation time, combined with the movement speed of the reference node obtained by the difference of the absolute position coordinates carried by two adjacent broadcast messages. Extrapolation is not performed when the movement speed is lower than a preset speed threshold or the time difference is less than a preset time threshold, to avoid differential noise exceeding the compensated displacement. Before participating in subsequent calculations, the absolute position coordinates of each reference node are uniformly converted to the same local plane coordinate system.

[0039] In some embodiments, constructing a set of distance observation equations with the position of the node to be located as the unknown quantity based on the absolute position coordinates and corresponding relative distances of each reference node may further include: using the planar coordinates of the node to be located as the unknown quantity, for each reference node participating in the solution, establishing a theoretical distance expression between the reference node and the node to be located based on the calculation relationship between two points in plane geometry, and setting the theoretical distance expression equal to the relative distance actually measured in step 104, thereby writing a distance observation equation for each reference node, and combining the distance observation equations corresponding to all reference nodes to form the set of distance observation equations; wherein, each equation in the set of distance observation equations uses the absolute position coordinates of the reference node as a known constant, the planar coordinates of the node to be located as the unknown variable, and the corresponding relative distance as the observed value, and the solution of the set of equations is the absolute position of the node to be located; wherein, the self-organizing network module antennas of each forklift are installed at the same height and the ground elevation difference of the site is negligible, so the relative distance can be directly regarded as its projection in the same horizontal plane, and the absolute position coordinates of each reference node are taken as its projection in the same horizontal plane and then used to write the above equations.

[0040] In implementation, one equation from the range observation equation set can be selected as a reference equation. The remaining equations are subtracted from the reference equation to eliminate quadratic terms in the unknowns, transforming the nonlinear range observation equation set into a linear equation set about the planar coordinates of the node to be located, resulting in a linear matrix equation. Subsequently, a weighting matrix is ​​constructed. This weighting matrix is ​​a diagonal matrix with the same order as the number of linear equations obtained after subtraction. Each element on the diagonal corresponds to the weight of each linear equation obtained after subtraction. Since each linear equation obtained after subtraction involves both the reference node corresponding to the reference equation and the other reference node from which it is subtracted, each weight is determined jointly by the two reference nodes involved in the linear equation. The lower received signal strength indication of the two reference nodes is taken as the ranging signal quality characterization of the linear equation. The higher the received signal strength indication, the greater the weight assigned, allowing the reference node with better ranging signal quality to play a greater role in position calculation. Furthermore, the weights are reduced based on the higher relay level carried in the broadcast messages of the two reference nodes. No reduction is applied when the relay levels of both reference nodes are zero. The higher the relay level, the smaller the reduction factor, to account for the position uncertainty accumulated level by level as the absolute position coordinates of the reference node are obtained through step-by-step calculation. Then, the weighted matrix is ​​substituted into the weighted least squares solution process, sequentially calculating the transpose of the coefficient matrix in the linear matrix equation, the product of the transpose of the coefficient matrix and the weighted matrix, the product of this product and the coefficient matrix again, and the inverse matrix of the result. Finally, the inverse matrix, the transpose of the coefficient matrix, and the weighted matrix are combined... The right-hand side terms of the linear matrix equations are multiplied sequentially to obtain the absolute position of the node to be located. This absolute position is located in the same local plane coordinate system as the absolute positions of all reference nodes. It should be noted that when the relay levels of all reference nodes participating in the solution are the same, the linear equations obtained after subtracting the above reduction pairs have the same proportion. In this case, the reduction does not change the solution result of the weighted least squares. The uncertainty of the reference node's position, accumulated with the relay level, is accounted for by the corresponding amplification of the observation noise covariance matrix described below.

[0041] In some embodiments, the observation noise covariance of inertial fusion is increased according to the maximum relay level involved in the calculation to obtain the fused positioning result. This can be achieved by the following steps: Obtain the recursive position result of the inertial measurement unit of the node to be located at the current solution time; The observation noise covariance of the Kalman filter is set according to the maximum relay level involved in the solution. The higher the maximum relay level, the larger the observation noise covariance. The measurement update process of the Kalman filter is performed with the absolute position as the observation and the recursive result of the position as the state prediction, to obtain the fused position-state vector. The final position coordinates of the node to be located are extracted from the fused position state vector and used as the fused positioning result.

[0042] In this embodiment, the self-position recursion result and the self-absolute position are in the same local plane coordinate system, and the positioning result of the previous fusion time used in the recursion process comes from the output after Kalman filter fusion correction in the previous cycle, thereby ensuring the continuity of the recursion starting point and the fusion output in the time series.

[0043] In a specific implementation, using the absolute position of the node to be located as the observation and the recursive result of the position as the state prediction, the measurement update process of Kalman filtering is performed to obtain the fused position-state vector. This can further include: constructing a state vector with the planar position and velocity of the node to be located as state components; using the velocity increment and position increment during the recursive process of the inertial measurement unit as control inputs; establishing a state transition matrix based on the assumption of uniform motion or uniform acceleration motion; recursively transferring the posterior state vector of the previous fusion moment to the current moment through the state transition matrix; and combining the process noise covariance matrix to obtain the state prediction and the corresponding prediction error covariance matrix. Subsequently, using the absolute position of the node to be located obtained by the weighted least squares method as the external observation, an observation matrix is ​​constructed to map the state vector to the observation space. Based on the received signal strength indication of each reference node, the geometric accuracy attenuation factor calculated from the spatial geometric configuration of each reference node participating in the calculation relative to the node to be located, and the signal strength of each reference node participating in the calculation, the state prediction is obtained. The maximum relay level is used to jointly estimate the observation noise covariance matrix of the current observations. The larger the maximum relay level, the larger the estimated observation noise variance. Then, the Kalman gain is calculated. Finally, the measurement update is performed using the Kalman gain, the observations, and the state predictions to obtain the fused posterior state vector and the posterior error covariance matrix at the current time. The process noise covariance matrix is ​​set based on matching the typical motion dynamics of the forklift in warehouse conditions. The more frequent the forklift acceleration and deceleration, the larger the process noise variance is set. When the forklift runs at a constant speed and smoothly, a smaller process noise variance can be set. The observation noise covariance matrix is ​​dynamically adjusted according to the ranging signal quality of the reference nodes participating in each solution. When the overall ranging signal quality is good, the observation noise variance is taken as a smaller value to make the fusion result more reliable to the observation values. When the overall ranging signal quality is poor, the observation noise variance is taken as a larger value to make the fusion result more reliable to the inertial recursive prediction values. When the maximum relay level among the reference nodes participating in this solution is high, a larger observation noise variance is also taken.

[0044] In this embodiment, the position component extracted from the posterior state vector according to a preset index is the final position coordinate of the node to be located output in the current fusion cycle. This final position coordinate is output as the fusion positioning result to the leased asset management platform and serves as the starting position reference for the inertial measurement unit recursion in the next fusion cycle. The fusion positioning result is obtained by Kalman filtering fusion of the cooperative positioning absolute position calculation and the inertial measurement unit recursion. When the ranging signal quality of the reference node is poor or the relay level is high, the influence of the external observation on the fusion result is reduced by increasing the observation noise covariance. When the external observation quality is good, the external observation is used to correct the inertial recursion deviation, thereby suppressing the jump of the continuous positioning trajectory and reducing the error accumulation caused by relying solely on inertial recursion.

[0045] In another aspect, in some embodiments, this application provides a location tracking system for leased forklift assets, with reference to... Figure 3 This figure is a schematic diagram of the structure of a rental forklift asset location tracking system 200 according to some embodiments of this application. The rental forklift asset location tracking system 200 includes a broadcast module 201, a processing module 202, and an execution module 203. Each module is described below: The broadcast module 201 is mainly used to deploy an ad hoc network module for inter-vehicle ranging on each forklift, and each forklift broadcasts the satellite positioning quality factor and absolute position coordinates; wherein, the ad hoc network module sends the satellite positioning quality factor, absolute position coordinates and timestamp through broadcast messages.

[0046] The processing module 202 is mainly used to calculate the node connectivity of each forklift based on the satellite positioning quality factor of the surrounding forklifts. The node connectivity is the number of surrounding forklifts that meet the signal reception quality requirements but whose satellite positioning quality does not meet the preset positioning quality requirements within the current statistical time window. The processing module 202 extracts the valid records within the current statistical time window from the neighbor information table and calculates the node connectivity.

[0047] The processing module 202 is also used for distributed election of each forklift based on satellite positioning quality factor and node connectivity: those with valid satellite positioning solutions and positioning quality that meet the preset positioning quality requirements are direct positioning nodes; those that have been successfully distanced and solved by at least three surrounding nodes that have carried valid absolute position coordinates are relay positioning nodes; the rest are nodes to be positioned; the relay level of direct positioning nodes is zero; the relay level of relay positioning nodes is the maximum relay level of the nodes used plus one; and the valid coordinates are broadcast only after the solution is successful; wherein, the relay positioning node only broadcasts the valid coordinates after completing the distance measurement and position solution, and uses the maximum relay level of the nodes used plus one as the relay level of this node.

[0048] The processing module 202 is further configured to select at least three reference nodes from direct positioning nodes or relay positioning nodes whose absolute position coordinates are valid and whose relay level is not higher than the preset maximum relay level, perform inter-vehicle distance measurement to obtain a relative distance set, and receive the absolute position coordinates and relay level of each reference node; wherein, the processing module 202 filters candidate records with valid coordinates and relay levels not exceeding the upper limit from the neighbor information table, and forms a reference node set.

[0049] The execution module 203 is mainly used to calculate the absolute position of the node to be located based on the relative distance set and absolute position coordinates after time synchronization, reduce the corresponding ranging calculation weight according to the relay level of the reference node, and increase the observation noise covariance of inertial fusion according to the maximum relay level participating in the calculation, using the absolute position of itself as the observation, to obtain the fused positioning result; wherein, the execution module 203 forms its own absolute position using the weighted least squares method, and then uses the absolute position of itself as the Kalman filter observation to complete the inertial fusion.

[0050] In addition, this application also provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the above-described method for tracking the location of leased forklift assets.

[0051] In some embodiments, reference Figure 4 This figure is an internal structural diagram of a computer device implementing a method for tracking the location of leased forklift assets according to some embodiments of this application. The method for tracking the location of leased forklift assets in the above embodiments can be implemented through... Figure 4 The computer device shown is used to implement this, and the computer device 300 includes at least one processor 301, a communication bus 302, a memory 303, and at least one communication interface 304.

[0052] The processor 301 may be a general-purpose central processing unit (CPU), an application-specific integrated circuit (ASIC), or one or more devices used to control the execution of the rental forklift asset location tracking method in this application.

[0053] The communication bus 302 is used to transmit information between the aforementioned components.

[0054] The memory 303 may be a read-only memory (ROM) or other type of static storage device capable of storing static information and instructions, random access memory (RAM) or other type of dynamic storage device capable of storing information and instructions, or an electrically erasable programmable read-only memory (EEPROM), a compact disc read-only memory (CDROM) or other optical disc storage, optical disc storage (including compressed optical discs, laser discs, optical discs, digital universal optical discs, Blu-ray discs, etc.), a magnetic disk or other magnetic storage device, or any other medium capable of carrying or storing desired program code in the form of instructions or data structures and accessible by a computer, but not limited thereto. The memory 303 may exist independently and be connected to the processor 301 via a communication bus 302. The memory 303 may also be integrated with the processor 301.

[0055] The memory 303 stores program code for executing the solution of this application, and its execution is controlled by the processor 301. The processor 301 executes the program code stored in the memory 303. The program code may include one or more software modules. In the above embodiment, the leased forklift asset location tracking method can be implemented by the processor 301 and one or more software modules in the program code in the memory 303.

[0056] Communication interface 304 uses any transceiver-like device to communicate with other devices or communication networks, such as Ethernet, radio access network (RAN), wireless local area networks (WLAN), etc.

[0057] In a specific implementation, as one example, a computer device may include multiple processors, each of which may be a single-core (single CPU) processor or a multi-core (multi CPU) processor. Here, a processor may refer to one or more devices, circuits, and / or processing cores used to process data (e.g., computer program instructions).

[0058] The aforementioned computer device can be a general-purpose computer device or a special-purpose computer device. In specific implementations, the computer device can be a desktop computer, a portable computer, a network server, a handheld digital assistant (PDA), a mobile phone, a tablet computer, a wireless terminal device, a communication device, or an embedded device. This application does not limit the type of computer device.

[0059] In addition, this application also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the above-described method for tracking the location of leased forklift assets. The computer-readable storage medium may be the non-transitory storage medium described in memory 303, and the stored program code is read and executed by processor 301.

[0060] In summary, in the rental forklift asset location tracking method and system disclosed in this application, each forklift performs distributed role election based on satellite positioning quality factors and node connectivity. The relay positioning node assumes relay function only after completing ranging and position calculation using at least three surrounding forklifts carrying valid absolute position coordinates; its level is the maximum relay level of the selected nodes plus one. The node to be located selects only at least three reference nodes with valid coordinates and a level not exceeding the upper limit. The ranging calculation weight is reduced as the reference node level increases, and the observation noise covariance of inertial fusion is increased according to the maximum level to obtain the fused positioning result. Therefore, the impact of relay position uncertainty propagating along the cooperative positioning link on the forklift location tracking result can be reduced.

[0061] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0062] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A method for tracking the location of leased forklift assets, characterized in that, include: Deploy an inter-vehicle ranging self-organizing network module on each forklift, and broadcast the satellite positioning quality factor and absolute position coordinates to each forklift; Each forklift calculates node connectivity based on the satellite positioning quality factor of surrounding forklifts. The node connectivity is the number of surrounding forklifts that meet the signal reception quality requirements but whose satellite positioning quality does not meet the preset positioning quality requirements within the current statistical time window. Each forklift is selected in a distributed manner based on satellite positioning quality factors and node connectivity: those with valid satellite positioning solutions and positioning quality that meet the preset positioning quality requirements are direct positioning nodes; those that have been successfully distanced and solved by at least three surrounding nodes that already carry valid absolute position coordinates are relay positioning nodes; the rest are nodes to be positioned. The relay level of direct positioning nodes is zero, and the relay level of relay positioning nodes is the maximum relay level of the nodes used plus one. After successful solution, the valid coordinates are broadcast. The node to be located selects at least three reference nodes from direct positioning nodes or relay positioning nodes whose absolute position coordinates are valid and whose relay level is not higher than the preset maximum relay level. The relative distance set is obtained by measuring the distance between vehicles, and the absolute position coordinates and relay level of each reference node are received. The node to be located calculates its own absolute position based on the relative distance set and absolute position coordinates after time synchronization. The corresponding ranging calculation weight is reduced according to the relay level of the reference node. The observation noise covariance of inertial fusion is increased according to the largest relay level participating in the calculation, using its own absolute position as the observation. The fusion positioning result is obtained.

2. The method as described in claim 1, characterized in that, Each forklift's connectivity is calculated based on the satellite positioning quality factor of surrounding forklifts, specifically including: Extract the satellite positioning quality factor corresponding to each surrounding forklift from the locally maintained neighbor information table; Based on the timestamps of the corresponding records of each surrounding forklift in the neighbor information table, the valid neighbor records within the current statistical time window are determined. The node connectivity is obtained by counting the records in the effective neighbor records that meet the signal reception quality requirements but whose satellite positioning quality factors do not meet the preset positioning quality requirements.

3. The method as described in claim 1, characterized in that, The distributed election of each forklift based on satellite positioning quality factor and node connectivity specifically includes: For each forklift, obtain its own satellite positioning quality factor and the connectivity of the node; Based on the satellite positioning quality factor and the node connectivity, calculate the election score of this forklift as a reference node; Based on the election score and the surrounding forklift role perception results obtained by this forklift from receiving broadcast messages from surrounding forklifts, the election role of this forklift is determined. Mark this forklift as a direct positioning node, a relay positioning node, or a node to be positioned.

4. The method as described in claim 1, characterized in that, The node to be located selects at least three reference nodes from direct positioning nodes or relay positioning nodes whose absolute position coordinates are valid and whose relay level is not higher than the preset maximum relay level. It then performs inter-vehicle ranging to obtain a relative distance set and receives the absolute position coordinates and relay level of each reference node, specifically including: From the direct positioning nodes or relay positioning nodes whose absolute position coordinates perceived by this forklift are valid and whose relay level is not higher than the preset maximum relay level, select at least three reference nodes whose spatial geometric distribution meets the requirements for planar position calculation. Vehicle-to-vehicle distance measurements are performed with the selected reference nodes to obtain a set of relative distances containing the relative distances between each selected reference node; Receive the absolute position coordinates and relay level from each selected reference node.

5. The method as described in claim 1, characterized in that, The node to be located calculates its absolute position based on the relative distance set and absolute position coordinates after time synchronization, and the corresponding ranging calculation weight is reduced according to the relay level of the reference node, specifically including: Obtain the absolute position coordinates, relay level, relative distance corresponding to the relative distance set of each reference node that has completed time synchronization, and the received signal strength indication corresponding to the relative distance; Based on the absolute position coordinates and corresponding relative distances of each reference node, a set of distance observation equations is constructed with the position of the node to be located as the unknown. The distance observation equations are linearized, and a weighted matrix based on the received signal strength indication and the relay level of the reference node is introduced, wherein the higher the relay level, the lower the corresponding weight. The absolute position of the node to be located is obtained by solving the weighted least squares method.

6. The method as described in claim 1, characterized in that, The observation noise covariance of inertial fusion is increased according to the largest relay level involved in the solution to obtain the fused localization result, which specifically includes: Obtain the recursive position result of the inertial measurement unit of the node to be located at the current solution time; The observation noise covariance of the Kalman filter is set according to the maximum relay level involved in the solution. The higher the maximum relay level, the larger the observation noise covariance. The measurement update process of the Kalman filter is performed with the absolute position as the observation and the recursive result of the position as the state prediction, to obtain the fused position-state vector. The final position coordinates of the node to be located are extracted from the fused position state vector and used as the fused positioning result.

7. The method as described in claim 1, characterized in that, The self-organizing network module is an on-board communication device that is integrated on the forklift and can realize direct distance measurement and data exchange between vehicles without relying on external fixed communication infrastructure.

8. A location tracking system for leased forklift assets, characterized in that, include: The broadcast module is used to deploy an ad hoc network module for inter-vehicle ranging on each forklift, and each forklift broadcasts its satellite positioning quality factor and absolute position coordinates. The processing module is used to calculate the node connectivity of each forklift based on the satellite positioning quality factor of the surrounding forklifts. The node connectivity is the number of surrounding forklifts that meet the signal reception quality requirements but whose satellite positioning quality does not meet the preset positioning quality requirements within the current statistical time window. The processing module is also used for distributed election of each forklift based on satellite positioning quality factor and node connectivity: those with valid satellite positioning solutions and positioning quality that meet the preset positioning quality requirements are direct positioning nodes; those that have been successfully distanced and solved by at least three surrounding nodes that have carried valid absolute position coordinates are relay positioning nodes; the rest are nodes to be positioned; the relay level of direct positioning nodes is zero; the relay level of relay positioning nodes is the maximum relay level of the nodes used plus one; and the valid coordinates are broadcast after successful solution. The processing module is also used to select at least three reference nodes from direct positioning nodes or relay positioning nodes whose absolute position coordinates are valid and whose relay level is not higher than the preset maximum relay level, perform inter-vehicle distance measurement to obtain a relative distance set, and receive the absolute position coordinates and relay level of each reference node. The execution module is used to calculate the absolute position of the node to be located based on the relative distance set and absolute position coordinates after time synchronization, reduce the corresponding ranging calculation weight according to the relay level of the reference node, and increase the observation noise covariance of inertial fusion according to the absolute position of the node to be located and the maximum relay level involved in the calculation, so as to obtain the fused positioning result.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the leased forklift asset location tracking method according to any one of claims 1 to 7.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the leased forklift asset location tracking method as described in any one of claims 1 to 7.

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