A method for searching materials by a construction robot based on RFID tags

Abstract

The application discloses a building robot material searching method based on RFID tags, which comprises the following steps: material is packed into piles and is piled in a site; after a building robot enters the site, a material pile is found and the building robot is moved to the side of the material pile, taking the material pile as a starting point; RFID tags of each material pile are read to find a material pile required by a first construction area; the found material pile is moved to the first construction area and is constructed; after the construction of the first construction area is completed, the previously read RFID tags are searched to confirm whether there is material pile information required by a next construction area; if yes, the building robot is directly moved to the side of the material pile and is constructed; if not, all the observed but not read material piles are faced and a required material pile is found in the material piles; the required material of a subsequent construction area is continuously searched, and the construction of the corresponding construction area is completed until the construction is completed. The application greatly improves the material searching efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of construction robots, and particularly relates to a construction robot material searching method based on RFID tags. BACKGROUND

[0002] During construction, a large number of materials are usually stored in a relatively open site. Some materials have a designated use area, so when these areas are under construction, the required materials need to be found from among the numerous materials. Because materials are often moved in actual construction, even if all the materials are counted and located in advance, the obtained information may be outdated and unreliable, so it is often necessary to search for the required materials in the site temporarily. The traditional method is to visually inspect each material pile by manual labor to determine whether it is the searched material. Recently, the construction industry has promoted the digital traceability technology of building materials, and materials are provided with RFID tags when they leave the factory. An RFID reader can be manually held to read the information of each material pile, and then it can be determined whether it is the required material. However, due to cost reasons, the reading distance of the RFID tag used is usually within a few meters, and the personnel need to approach the material pile to stably read the information in the tag. Therefore, the existing technology requires a large amount of manual operation, which is time-consuming and labor-intensive. When the site is large, the materials are scattered, and the line of sight is easily blocked, some materials are often missed, resulting in the need to search for materials again. Moreover, the manual planning of the material searching path is often not scientific, and the searching time has room for compression.

[0003] Therefore, it is urgent to solve the above problems. SUMMARY

[0004] The purpose of the present application is to provide a construction robot material searching method based on RFID tags, which can quickly find the required material pile among the material piles scattered in the site based on RFID tags, so as to improve the efficiency of the robot and reduce the labor intensity.

[0005] Technical scheme: In order to achieve the above purpose, the present application discloses a construction robot material searching method based on RFID tags, comprising the following steps:

[0006] (1) The materials are packed into piles and enter the site, and are stacked in the site;

[0007] (2) The construction robot enters the site, finds a material pile after entering the site, and moves to the side of the material pile, taking the material pile as the starting point;

[0008] (3) The construction robot finds the material pile required by the first construction area by reading the RFID tags of each material pile. The RFID tag information read in the finding process is stored in the construction robot. If the construction robot has scanned and modeled the global environment of the construction site, the construction robot groups the material piles in the global environment according to their positions, identifies how many material piles are in each material pile group by using a contour recognition algorithm, then plans a route to visit each group of material piles one by one, and uses the RFID reader to find the required material pile in each group of material piles. If the construction robot has not scanned and modeled the global environment of the construction site, the construction robot groups the material piles that can be observed at the starting point according to their positions, identifies how many material piles are in each material pile group by using a contour recognition algorithm, then plans a route to visit each group of material piles one by one. After finding the required material pile, the construction robot interrupts the subsequent route planning and no longer visits the subsequent material pile groups.

[0009] (4) The construction robot moves the found material pile to the first construction area and performs construction.

[0010] (5) After completing the construction of the first construction area, the construction robot retrieves the previously read RFID tags to confirm whether there is material pile information required by the next construction area. If there is, the construction robot can directly move to the side of the material pile and repeat step (4). If there is not, the construction robot faces all the observed but not read material piles, repeats steps (3) and (4), and finds and uses the required material pile in the process.

[0011] (6) Repeat step (5) to find the required material for subsequent construction areas, and complete the construction in the corresponding construction area until all areas are constructed.

[0012] Optionally, in step (1), the material is packed into a pile and placed on a tray, and the tray enters the site together with the material. When the material is packed, an ultra-high frequency (UHF) or active RFID tag is attached to ensure that the reading distance of the RFID tag reaches 4m or more. The RFID tag indicates the quantity and size of the material in the material pile and the corresponding construction area information in the construction site.

[0013] Optionally, in step (2), if the construction robot stores a three-dimensional map of the site, the construction robot moves to the nearest material pile based on the three-dimensional map after entering the site, and uses the material pile as the starting point.

[0014] Optionally, in step (2), if the construction robot does not store the three-dimensional map of the site, the construction robot will move to the nearest material pile as the starting point if it can see all or part of the material pile in its field of view at the entrance; if the construction robot cannot see the material pile in its field of view, the construction robot will perform a full site mapping and modeling according to the preset inner spiral full traversal path planning algorithm, and read the RFID tags of the observed material piles during the mapping and modeling; then after the mapping and modeling is completed, the construction robot will move to the nearest material pile to the starting point.

[0015] Optionally, in step (2), if the construction robot stores the three-dimensional map of the site, but when the material piles in the site are moved, the expired three-dimensional map information should not be used, and the operation should be performed as if the three-dimensional map of the site is not stored, that is, the construction robot will move to the nearest material pile as the starting point if it can see all or part of the material pile in its field of view at the entrance; if the construction robot cannot see the material pile in its field of view, the construction robot will perform a full site mapping and modeling according to the preset inner spiral full traversal path planning algorithm, and read the RFID tags of the observed material piles during the mapping and modeling; then after the mapping and modeling is completed, the construction robot will move to the nearest material pile to the starting point.

[0016] Optionally, in step (3), the specific method of grouping is to set the reading distance of the RFID tags on the material piles as the radius of a circle, and then cover all the material piles with as few circles as possible, and the position corresponding to each circle is a group of material piles; in this way, the information of each pile in the corresponding group can be read at the center position of each circle; when some material piles belong to two or more groups of material piles, the material piles are preferentially assigned to the group with more piles or closer to the current starting point.

[0017] Optionally, in step (3), the specific method of planning the route is that the construction robot faces all groups of material piles that have been observed and not visited, and needs to plan a path to reach these groups of material piles so that these groups of material piles are only visited once and the required material piles can be found as soon as possible; in the route planning, it is not necessary to plan to return to the current position; the goal is no longer to minimize the total path, but to minimize the expected time to find the required material piles in the groups of material piles that have been observed and not visited.

[0018] Optionally, the specific method of route planning in step (3) is: during the movement of the construction robot to the next group of material piles, some previously unobserved material piles may be observed; then when the construction robot reaches the next group of material piles, re-plan the path for all observed but unvisited material piles, and then move according to the new optimal planned path to find the required material pile.

[0019] Optionally, the specific method of route planning in step (3) is: when the construction robot has visited all observed groups of material piles but cannot find the required material pile, the entire construction site will be scanned and modeled according to the preset inner spiral full traversal path planning algorithm, and the trajectory gap of the scanning and modeling will be set within twice the reading distance of the RFID tag on the material pile, so that the construction robot can read the RFID tags of all material piles in the construction site during the scanning and modeling process; if the required material pile is still not found, the construction robot will issue an alarm.

[0020] Optionally, the specific mathematical model of route planning in step (3) is:

[0021] Suppose there are M piles of material piles in the global scene of the construction site, the current construction robot has visited P groups of material pile groups, and has not found the required material pile, P groups of material pile groups contain Q piles of material piles, Q≥P; the current construction robot is beside the Pth group of material piles, which is taken as the starting point, and the serial number is 0; J groups of unvisited material pile groups have been observed, J groups of unvisited material pile groups contain K piles of material piles, K≥J, K+Q≤M; the serial numbers of J groups of unvisited material pile groups are 1, 2, …, J, and the number of material piles in each group of material pile groups is I i (i = 1, 2, …, J), The distance between the ith group and the s group of material piles is D is , i, s are the serial numbers of the material pile groups, and the moving speed of the construction robot is a constant value V;

[0022] Path planning is performed for J groups of unvisited material pile groups, assuming that the path passes through 1, 2, …, J groups of material pile groups in turn, and the corresponding path takes W 12…J time. The enumeration method or dynamic programming algorithm can be used to plan the path of J groups of material pile groups, and there are at most paths. For each planned path, the expected time to find the required material pile can be calculated according to the following formula:

[0023] W 12…J = P1*T1+P2*T2+…+P J *T J +P other *T other

[0024] wherein P t (t = 1, 2, 3, …, J) is the probability of finding the required pallet in the tth group of pallets, T t is the time for the construction robot to reach the tth group of pallets, P other is the probability that the required pallet is not in the current planned J groups of pallets, nor in the P groups of pallets that have been visited before, but in the remaining M-Q-K pallets, T other is the time for finding the required pallet in the remaining M-Q-K pallets after visiting the current J groups of pallets; since in the calculation of the expected time for all different paths for the current planned J groups of pallets, P other and T other are constant values, therefore when comparing different path plans, only P1*T1+P2*T2+…+P J *T J are needed;

[0025] Assuming that the probabilities of the remaining M-Q pallets other than the previously visited Q pallets are equal, and each is then

[0026]

[0027] T t = (D 01 +D 12 +…+D t-1,t ) / V

[0028] For other paths, W 12…J and the subscripts of D 01 +D 12 +…+D t-1,t are adjusted according to the actual sequence of the path, and the W values under different path plans are calculated, and the path corresponding to the minimum T value is the optimal path under the current conditions.

[0029] Advantages: Compared with the prior art, the present application has the following remarkable advantages: the present application uses RFID tags to mark materials for different construction areas, so that the robot can identify the materials through the RFID reader; the improved path planning method of the present application enables the construction robot to plan the moving path according to the observed and identified pallets, and thus find the required materials as soon as possible in the dispersed pallets; the improved path planning method of the present application is closer to the actual scene of material searching, can shorten the material searching time, and the material searching process is more intelligent and efficient. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1The flowchart of the present application. DETAILED DESCRIPTION

[0031] In order to make the objects, technical solutions and advantages of the present application clearer, further detailed description will be given below in combination with the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application.

[0032] It should be understood that the present application can be implemented in different forms and should not be interpreted as being limited to the embodiments presented herein. On the contrary, these embodiments are presented to make the disclosure complete and full and to fully convey the scope of the present application to those skilled in the art. In the drawings, the sizes and relative sizes of the components can be exaggerated for the sake of clarity. The same reference signs represent the same components throughout.

[0033] As shown in the drawings, a building robot material searching method based on RFID tags in the present application comprises the following steps: Figure 1

[0034] (1) The materials are packed into the site and stacked in the site;

[0035] The materials need to be packed into stacks and placed on pallets, and the pallets are brought into the site together. When the materials are packed, an ultra-high frequency (UHF) or active RFID tag needs to be attached to ensure that the reading distance of the RFID tag reaches 4m or more. The RFID tag indicates the quantity and size of the materials in the material stack and the corresponding construction area information in the construction site;

[0036] (2) The building robot enters the site. When the building robot enters the site, it finds a material stack through the laser radar or visual camera installed on the robot body and moves to the side of the material stack, taking the material stack as the starting point;

[0037] If the building robot stores a three-dimensional map of the site, the building robot moves to the nearest material stack after entering the site according to the three-dimensional map, taking the material stack as the starting point;

[0038] If the building robot does not store a three-dimensional map of the site, the building robot moves to the nearest material stack at the entrance if it can see all or part of the material stacks in its field of view, taking the material stack as the starting point. If the building robot cannot see the material stacks in its field of view, it will scan and model the entire construction site according to a preset inner spiral traversal path planning algorithm and read the RFID tags of the observed material stacks during the scanning and modeling process. Then, after the scanning and modeling is completed, the building robot moves to the nearest material stack and takes it as the starting point;

[0039] ​The laser sensor has a large ranging distance, and the mapping trajectory of the construction robot is also large, so the construction robot does not necessarily pass by all the material piles in close range during the mapping process, and therefore the RFID information of all the material piles is not necessarily read during the mapping process. During the whole material searching process, if the construction robot has obtained the information of some material piles in advance, the construction robot can directly move to the material pile when it needs to search for the material pile again, without searching for it again;

[0040] If the construction robot stores a three-dimensional map of the site, but the materials in the site have been moved, the outdated map information should not be used, and the operation should be performed according to the mode in which the three-dimensional map of the site is not stored;

[0041] (3) The construction robot searches for the material pile needed by the first construction area by reading the RFID information of each material pile, and the RFID information read during the searching process is stored in the construction robot;

[0042] If the construction robot has performed mapping modeling on the global environment of the construction site, the material piles in the global environment are grouped according to their positions, the number of material piles in each group is identified by a contour recognition algorithm, and then the construction robot plans a route to visit each group of material piles one by one, and uses the RFID reader to search for the needed material pile in each group of material piles;

[0043] If the construction robot has not performed mapping modeling on the global environment of the construction site, the material piles that can be observed at the starting point are grouped according to their positions, the number of material piles in each group is identified by a contour recognition algorithm, and then the construction robot plans a route to visit each group of material piles one by one;

[0044] After the needed material pile is found, the construction robot interrupts the subsequent route planning and no longer visits the subsequent group of material piles;

[0045] The specific method of grouping is as follows:

[0046] The reading distance of the RFID tag on the material pile is set as the radius of a circle, and then as few circles as possible are used to cover all the material piles, and the position corresponding to each circle is a group of material piles; in this way, the information of each pile in the corresponding group can be read at the center position of each circle; according to this method, some material piles may belong to two or more groups of material piles, and these material piles can be preferentially assigned to the group with more piles or closer to the current starting point;

[0047] The specific method of planning a route is as follows:

[0048] The construction robot needs to plan a path to reach all the material pile groups which have been observed but not visited, so that these material pile groups are only visited once and the required material pile can be found as soon as possible; in the route planning, it is not necessary to plan to return to the current position; the goal of planning is no longer the shortest total path, but the shortest expected time to find the required material pile in the current material pile groups which have been observed but not visited;

[0049] Suppose that there are M piles of material piles in the global scene of the construction site, the current construction robot has visited P groups of material pile groups, and has not found the required material pile, P groups of material pile groups contain Q piles of material piles in total, Q≥P; the current construction robot is located beside the Pth group of material piles, which is taken as the starting point, and the serial number is 0; J groups of unvisited material piles have been observed, J groups of unvisited material piles contain K piles of material piles in total, K≥J, K+Q≤M; suppose that the serial numbers of J groups of unvisited material piles are 1, 2,…,J, and the number of material piles in each group of material piles is I i (i=1,2,…,J), The distance between the ith group and the sth group of material piles is D is , i, s are the serial numbers of the material piles, and the moving speed of the construction robot is a constant value V;

[0050] The path of J groups of unvisited material piles is planned, assuming that the path passes through 1, 2,…,J groups of material piles in turn, and the time taken by the corresponding path is W 12…J The enumeration method or dynamic programming algorithm can be used to plan the path of J groups of material piles, and there are at most paths, for each planned path, the expected time to find the required material pile can be calculated according to the following formula:

[0051] W 12…J =P1*T1+P2*T2+…+P J *T J +P other *T other

[0052] In the formula, P t (t=1,2,3,…,J) is the probability of finding the required material pile in the tth group of material piles, T t is the time taken by the construction robot to reach the tth group of material piles, P other is the probability that the required material pile is not in the current planned J groups of material piles, nor in the previously visited P groups of material piles, but in the remaining M-Q-K piles of material piles, and T other is the time taken by the construction robot to find the required material pile in the remaining M-Q-K piles of material piles after visiting the current J groups of material piles; since Pother and T other is a constant value, so when comparing different path planning, only P1*T1+P2*T2+…+P J *T J ;

[0053] It can be assumed that, in addition to the previously visited Q piles of material piles, the remaining M-Q piles of material piles that have not been visited are equal in probability of containing the required material, and each has a probability of then

[0054]

[0055] T t =(D 01 +D 12 +…+D t-1,t ) / V

[0056] The above formula is calculated according to the path of sequentially passing through 1, 2, …, J groups of materials. For other paths, W needs to be adjusted according to the specific path when calculating 12…J and D 01 +D 12 +…+D t-1,t subscript, using parameters consistent with the actual order; thus the W value under different path planning can be calculated, and the path corresponding to the minimum T value is the optimal path under the current conditions;

[0057] During the movement of the construction robot to the next group of material piles, some material piles that have not been observed before may be observed; then when the construction robot reaches the next group of material piles, the path planning for all observed but unvisited material piles is re-planned, and then the new optimal planning path is followed to move and find the required material pile;

[0058] When the construction robot visits the observed group of material piles but cannot find the required material pile, it will follow the preset inner spiral full traversal path planning algorithm to scan and model the entire construction site, and the gap between the scanning and modeling trajectories will be set within twice the reading distance of the RFID tag on the material pile, so that the construction robot can read the RFID tag of all material piles in the construction site during the scanning and modeling process; if the required material pile is still not found, the construction robot will issue an alarm;

[0059] (4) The construction robot moves the found material pile to the first construction area and performs construction;

[0060] (5) After completing the construction of the first construction area, the construction robot retrieves the RFID tag read previously to confirm whether there is the material stack information required for the next construction area; if so, it can directly move to the material stack and repeat step (4); if not, it faces all the material stacks that have been observed but not read, repeating steps (3) and (4) to find and use the required material stacks;

[0061] (6) Repeat step (5) to find the materials required for the subsequent construction area and complete the construction in the corresponding construction area until all planned areas are completed.

[0062] Example 1

[0063] The construction robot in the present invention can be a ceiling installation robot as disclosed in CN118793252A. This embodiment depicts a factory undergoing ceiling installation, where the robot is used to locate, fork, move, and lift materials, assisting workers in construction. The factory measures 40m x 80m, with six pillars as the primary obstruction. The factory's construction site requires 32 stacks of ceiling panels, of which 16 have already been installed, corresponding to half the total area.

[0064] The remaining 16 stacks of ceiling tiles have all arrived on-site and are scattered across the factory floor. The tiles are packaged into stacks and placed on pallets, arriving on-site with the pallets. Each stack of ceiling tiles is equipped with an ultra-high-frequency (UHF) RFID tag with a stable read range of up to 4 meters. Reading the RFID tag provides a list of materials within the stack, along with the dimensions of each tile. The stack's overall number is also available, indicating which area within the factory the stack is intended for. RFID tags typically also record other factory-installed material information, such as manufacturer, production date, material, and weight. This facilitates material acceptance, management, and subsequent maintenance, while also facilitating on-site deployment and replenishment requests.

[0065] When the ceiling tiles arrived on-site, most were delivered directly to the areas where they would be used, but a small number might have been sent to locations other than those designated for their intended use. The ceiling tiles' storage location within the factory building wasn't reflected in the building's BIM model. Because these ceiling tiles hadn't arrived when the construction robot was scanning and modeling the building, they were often not included in the robot's 3D map. Therefore, when the ceiling tile installation robot arrived on-site, it didn't use the 3D map converted from the BIM file or the previously scanned and modeled map. Instead, it used a 3D camera for navigation and recognition.

[0066] When the ceiling panel installation robot enters the factory building, the 3D camera of the ceiling panel installation robot is started to identify the surrounding environment. By calling the YOLO V5 visual algorithm, the ceiling panel installation robot can perceive objects such as ceiling panel stacks and obstacles in the scene, and identify the outline of the ceiling panel stacks and the tray under the ceiling panel stacks in the scene through the open source data set and algorithm. However, due to reasons such as light and obstacles, the ceiling panel installation robot can only identify the scene within a radius of about 10 meters, and there are 5 stacks of ceiling panels in this range, 3 of which are separately stacked and are within 5-10 meters from other ceiling panels, and 2 of which are stacked together and are about 3 meters apart from each other. According to the specific grouping method in the present application, the two stacks are grouped into one group, and the other three stacks each form a group.

[0067] The group of ceiling panels closest to the ceiling panel installation robot contains only one stack of ceiling panels, and the ceiling panel installation robot moves to the vicinity of the stack of ceiling panels, reads the serial number of the stack of ceiling panels through the RFID reader carried by the ceiling panel installation robot, and the serial number is 22. The area currently planned for construction by the robot is No. 17, which does not match the serial number of the ceiling panel.

[0068] The ceiling panel installation robot needs to find the required serial number 17 of the ceiling panel in the remaining 3 groups (4 stacks) of ceiling panels that have been observed but not visited, and the ceiling panel installation robot needs to plan a path to visit the 3 groups of ceiling panels in turn.

[0069] The serial numbers of the 3 groups (4 stacks) of ceiling panels are set as shown in Table 1:

[0070] Table 1

[0071]

[0072] According to the measurement of the 3D camera of the ceiling panel installation robot, the distances between the 4 groups of ceiling panels are as shown in Table 2:

[0073] Table 2

[0074] Group number\Distance\Group number 0 1 2 3 0 0 5 7.5 10 1 5 0 8 6 2 7.5 8 0 9 3 10 6 9 0

[0075] The serial number 17 of the ceiling panel is among the remaining 15 stacks of ceiling panels in the site, but not necessarily in the 3 groups (4 stacks) of ceiling panels that can be observed at present.

[0076] Based on the 3 groups (4 stacks) of ceiling panels that have been observed but not visited, the ceiling panel installation robot plans a total of paths, which are 123 (i.e. first move to the group with serial number 1, then move to the groups with serial numbers 2 and 3 in turn), 132, 213, 231, 312, and 321. Then, the ceiling panel installation robot calculates the expected time to find the required ceiling panel for each path.

[0077] For the path with sequence 123, the expected time to find the required material pile is calculated according to the mathematical model of route planning in the present application, without considering P other *T other ,

[0078] W 123 = P1*T1+P2*T2+P3*T3

[0079]

[0080] The calculation can be obtained where V is the moving speed of the robot.

[0081] The expected time to find the required material pile for the other 5 paths can be calculated in the same way. Then the path with the shortest expected time is selected as the current optimal planning path. The calculation time of the suspended ceiling panel installation robot is within 1 ms, and the calculation time is generally not more than 20 ms when the number of groups and piles is less than 50.

[0082] The suspended ceiling panel installation robot visits these suspended ceiling panel piles according to the optimal planning path to find the No. 17 suspended ceiling panel pile. If other unvisited suspended ceiling panel piles are observed during the movement, they will be included in the path planning range and the path will be re-planned. If all the suspended ceiling panel piles observed during the movement are visited and the No. 17 suspended ceiling panel pile is still not found, a comprehensive movement will be made in the entire factory to find unobserved suspended ceiling panel piles and find the No. 17 suspended ceiling panel pile from them.

[0083] After the suspended ceiling panel installation robot finds the No. 17 suspended ceiling panel pile, it uses the YOLO V5 visual algorithm to identify the pallet under the material pile, determines the relative pose between the robot and the pallet, then adjusts its chassis to approach and be parallel to the edge of the pallet, then extends the fork teeth on the chassis into the pallet, lifts the pallet and the material, and then moves the fork teeth into the suspended ceiling panel installation robot, moving the pallet and the material to the upper part of the chassis of the suspended ceiling panel installation robot. The suspended ceiling panel installation robot carrying the No. 17 pallet and the suspended ceiling panel moves to the planned construction area, i.e. the No. 17 area.

[0084] After the installation of the No. 17 suspended ceiling panel pile is completed, the suspended ceiling panel installation robot repeats the above steps to find the No. 18 material, and performs the fork picking, carrying, jacking, and checking. Then the above steps are repeated for the No. 19, 20, …, 32 materials, and the construction is completed.

[0085] During the movement of the suspended ceiling panel installation robot, including the aforementioned movement according to the planned path to find the required suspended ceiling panel pile, the suspended ceiling panel installation robot models the environment along the way using a 3D camera. At the same time, the suspended ceiling panel installation robot records the numbers of the material piles that have read the RFID tags, facilitating subsequent quick positioning of material piles with specific numbers without the need to re-plan the path and re-find the material piles.

Claims

1. A construction robot material search method based on RFID tags, characterized in that: The steps include: (1) Materials are packed into stacks and stacked on site; (2) The construction robot enters the site, finds a material stack, and moves to the side of the material stack, using the material stack as the starting point; (3) The construction robot searches for the material stacks required for the first construction area by reading the RFID tags of each material stack. The RFID tag information read during the search process is stored inside the construction robot. If the construction robot has performed an overscanning modeling of the global environment of the construction site, the material stacks in the global environment are grouped according to their locations, and the contour recognition algorithm is used to identify the number of material stacks in each material stack group. Then, a route is planned to visit the material stacks in each group one by one, and the RFID reader is used to search for the required material stacks in each group of material stacks. If the construction robot has not performed an overscanning modeling of the global environment of the construction site, the material stacks that can be observed at the starting point are grouped according to their locations, and the contour recognition algorithm is used to identify the number of material stacks in each material stack group. Then, a route is planned to visit the material stacks in each group one by one. After finding the required material stack, the construction robot interrupts the subsequent planned route and no longer visits the subsequent material stack groups. (4) The construction robot moves the found material stack to the first construction area and starts construction; (5) After completing the construction of the first construction area, the construction robot retrieves the RFID tag read previously to confirm whether there is the material stack information required for the next construction area; if so, it can directly move to the material stack and repeat step (4); if not, it faces all the material stacks that have been observed but not read, repeating steps (3) and (4) to find and use the required material stacks; (6) Repeat step (5) to find the materials required for the subsequent construction area and complete the construction in the corresponding construction area until all areas are completed.

2. The material-finding method for a construction robot based on RFID tags according to claim 1, characterized in that: In step (1), the materials are packed into stacks, placed on pallets, and brought into the site together with the pallets; when the materials are packed, an ultra-high frequency (UHF) or active RFID tag must be attached to ensure that the reading distance of the RFID tag reaches 4m or more, and the RFID tag indicates the quantity and size of the materials in the material stack and the corresponding construction area information in the construction site.

3. The material-finding method for a construction robot based on RFID tags according to claim 1, characterized in that: In step (2), if the construction robot stores a three-dimensional map of the site, after entering the site, the construction robot moves to the nearest material stack according to the three-dimensional map and uses the material stack as a starting point.

4. The material-searching method for a construction robot based on RFID tags according to claim 1, characterized in that: In step (2), if the construction robot does not store a three-dimensional map of the site, the construction robot is at the entrance. If the construction robot can see all or part of the material stack in its field of view, it will move to the nearest material stack and use the material stack as the starting point. If the construction robot cannot see the material stack in its field of view, it will scan and model the entire construction site according to the preset inner spiral full traversal path planning algorithm, and read the RFID tags of the observed material stacks during the scanning and modeling process; Then, after scanning and modeling, it moves to the material stack closest to itself and uses the material stack as the starting point.

5. The method for searching materials by a construction robot based on RFID tags according to claim 1, characterized in that: In step (2), if the construction robot has stored a three-dimensional map of the site, but the material stacks in the site have been moved, the outdated three-dimensional map information should not be used, but the operation should be carried out as if no three-dimensional map of the site is stored. That is, when the construction robot is at the entrance, if all or part of the material stacks can be seen in the field of view of the construction robot, it will move to the nearest material stack and use the material stack as the starting point; If the construction robot cannot see the material stack in its field of view, it will scan and model the entire construction site according to the preset inner spiral full traversal path planning algorithm, and read the RFID tags of the observed material stacks during the scanning and modeling process; Then, after scanning and modeling, it moves to the material stack closest to itself and uses the material stack as the starting point.

6. The method for searching materials by a construction robot based on RFID tags according to claim 1, characterized in that: The specific method for grouping in step (3) is as follows: the reading distance of the RFID tag on the material stack is set to the radius of a circle, and then all the material stacks are covered with as few circles of the radius as possible, and the position corresponding to each circle is a group of material stacks; according to this method, the information of each stack in the corresponding group can be read at the center of each circle; when some material stacks belong to two or more groups of material stacks at the same time, such material stacks are preferentially assigned to the group with more stacks or closer to the current starting point.

7. The method for searching materials by a construction robot based on RFID tags according to claim 1, characterized in that: The specific method of planning the route in step (3) is as follows: the construction robot faces all the material stack groups that have been observed and not visited, and needs to plan a path to reach these material stack groups, so that these material stack groups are visited only once and the required material stack can be found as quickly as possible; When planning a route, there is no need to plan to return to the current location; The planning goal is no longer to minimize the total path, but to minimize the expected time to find the required material stack in the currently observed and unvisited material stack group.

8. The method for searching materials by a construction robot based on RFID tags according to claim 7, characterized in that: The specific method for planning the route in step (3) is as follows: when the construction robot moves to the next group of material stacks, it may observe some material stacks that have not been observed before; then when the construction robot arrives at the next group of material stacks, it re-plans the path for all material stacks that have been observed but not visited, and then moves according to the new optimal planned path to find the required material stacks.

9. The method for searching materials by a construction robot based on RFID tags according to claim 8, characterized in that: The specific method of planning the route in step (3) is as follows: when the construction robot has visited the observed material stack group but cannot find the required material stack, it will scan and model the entire construction site according to the preset inner spiral full traversal path planning algorithm, and the trajectory gap of the scanning and modeling will be set within twice the reading distance of the RFID tag on the material stack, so that the construction robot can read the RFID tags of all material stacks in the construction site during the scanning and modeling process; if the required material stack still cannot be found, the construction robot will issue an alarm.

10. The method for searching materials by a construction robot based on RFID tags according to claim 9, characterized in that: The specific mathematical model for planning the route in step (3) is: There are M material stacks in the global scene of the construction site. The current construction robot has visited P material stacks and has not found the required material. The P material stacks contain Q material stacks, and Q ≥ P. The current construction robot is next to the P-th material chopping group. The P-th material chopping group is taken as the starting point and the sequence number is set to 0; The J-group unvisited material chopping group has been observed. The J-group unvisited material chopping group contains K material stacks, K ≥ J, K + Q ≤ M; let the serial numbers of the J-group unvisited material chopping groups be 1, 2, ..., J, and the number of material stacks in each material chopping group is I i (i=1,2,…,J), The distance between the i-th group and the s-th group of materials is D is , i,s ​​is the serial number of the material chopping group, and the moving speed of the construction robot is a constant value V; Plan the path for the J-group material chops that have not been visited. Assume that the path passes through 1, 2, ..., J-group material chops in sequence, and the time taken for the corresponding path is W 12…J , you can use enumeration or dynamic programming algorithm to plan the path of J groups of materials to chop groups, with a maximum of For each planned path, the expected time to find the required material stack can be calculated according to the following formula: W 12…J =P1*T1+P2*T2+…+P J *T J +P other *T other Where P t (t=1,2,3,…,J) is the probability of finding the required material stack in the tth group of material stacks, T t is the time when the construction robot arrives at the tth group of material stacks, P other T is the probability that the required material stack is not in the currently planned J group material chop group, nor in the previously visited P group material chop group, but in the remaining MQK stack material stacks, other After visiting the current J-group material chop group, the time to continue to find the required material in the remaining MQK stacks of materials; because in the calculation of the expected time of all different paths for the currently planned J-group material chop group, P other and T other is a constant value, so when comparing different path plans, we only need to compare P1*T1+P2*T2+…+P J *T J That's it; Assume that, in addition to the Q stacks of materials that have been visited before, the probability of the remaining MQ stacks of materials that have not been visited being the required materials is equal, both but T t =(D 01 +D 12 +…+D t-1,t ) / V For other paths, W needs to be adjusted accordingly during calculation. 12…J and D 01 +D 12 +…+D t-1,t The subscript of , using the parameters that match the actual order, is used to calculate the W value under different path planning. The path corresponding to the minimum T value is the optimal path under the current conditions.

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