Method for lifting and transporting a load using an autonomous forklift truck

Abstract

This method (20) for lifting and transporting a load comprises: - a receive step (21) whereby the truck receives a mission comprising a theoretical value of at least one dimension of said load; - a movement step (22) of moving the truck to face the load that is to be lifted and transported; - an acquisition step (23) of acquiring at least one image of the load using at least one camera fixed to the truck; - a determination step (24) of determining an actual value of said dimension of the load from said image obtained in the acquisition step; - a comparison step (26) of comparing the actual value and the theoretical value of said dimension, and - a stopping step (27) of stopping the truck if the discrepancy between the actual value of said dimension and its theoretical value is greater, in terms of absolute value, than a predefined limit value.

Description

[0001] DESCRIPTION

[0002] TITLE: Method of lifting and transporting a load by an autonomous lifting forklift

[0003] Technical field

[0004] The present invention relates to the field of autonomous vehicles for the automated transport of loads, such as autonomous forklifts.

[0005] State of the prior art

[0006] Autonomous vehicles for transporting loads are increasingly used to increase productivity and improve logistics management in factories and warehouses.

[0007] Automated forklifts are an example of such vehicles and allow, for example, loading, transporting and positioning a load at height without human intervention.

[0008] However, in environments such as factories or warehouses, human intervention is still necessary to complement automated operations, for example to monitor the smooth running of these operations or to perform tasks that cannot be performed by machines alone. These environments are therefore shared between humans and autonomous machines.

[0009] The safety of people is fundamental in such working environments and therefore requires the implementation of specific procedures.

[0010] For example, when picking up a load from a storage rack that can accommodate different loads, particularly in terms of dimensions, it is possible that the load actually present on the rack does not correspond to the load to be picked up by the autonomous forklift truck according to the mission assigned to the latter by a management system managing the warehouse flows.

[0011] If this is the case, there is a risk of an accident. Disclosure of the invention

[0012] In view of the above, the aim of the invention is to increase the safety of lifting and load transport operations by an autonomous forklift.

[0013] The subject of the invention is a method for lifting and transporting a load by an autonomous forklift truck comprising a vertically movable fork equipped with at least one arm.

[0014] The process includes:

[0015] - a step of receiving by the trolley an assigned mission of moving the load to be lifted and transported which includes a theoretical value of at least one dimension of said load;

[0016] - a step of moving the autonomous forklift in front of the load to be lifted and transported,

[0017] - a step of acquiring at least one image of the load by at least one camera fixed to the autonomous forklift truck, being centered relative to the fork and having a line of sight oriented forward along a longitudinal axis of said truck;

[0018] - a step of determining a real value of said dimension of the load from said image obtained in the acquisition step,

[0019] - a step of comparing the actual value of said dimension of the load determined in the determination step and the theoretical value of said dimension of the load received in the reception step, and

[0020] - a step of stopping the trolley if the difference between the actual value of said dimension and its theoretical value is greater in absolute value than a predefined limit value, or a step of lifting and transporting the load if the difference between the actual value of said dimension and its theoretical value is less than or equal in absolute value to the predefined limit value.

[0021] Such a method makes it possible to increase operational safety by stopping the autonomous truck before taking the load if this load does not correspond to that of the mission assigned to the truck. Such a method makes it possible to increase operational safety by taking into account the actual values ​​of the dimensions of the load to be transported. The method thus makes it possible to adapt the behavior of the truck according to the loads to be transported in order to preserve the safety of people.

[0022] The process thus makes it possible to check the consistency between the mission assigned by the truck and the load actually present on the rack before carrying out lifting and transport operations. The process thus makes it possible not to rely solely on the information from the mission assigned to the truck to carry out these operations.

[0023] According to a first embodiment, said camera is a 3D camera restoring a cloud of points of coordinates measured in a reference frame associated with said 3D camera, and the determination step comprises a step of digital processing of said image obtained in the acquisition step which comprises a sub-step of calculating the real value of said dimension of the load.

[0024] According to a second alternative implementation mode, the determination step comprises a step of reading a barcode on said image obtained in the acquisition step, and a step of extracting the actual value of said dimension of the load from a table contained in a memory of the forklift according to the barcode read. For this alternative implementation mode, said camera may or may not be a 3D camera.

[0025] According to the first mode of implementation, it is possible for example that: the load to be lifted and transported is annular, the mission assigned to the reception step includes theoretical values ​​of the depth and the outer diameter of the annular load, the digital processing step includes sub-steps for calculating the actual values ​​of the depth and the outer diameter of the annular load, the comparison step includes the comparison of the actual value and the theoretical value of the depth of the load, and the comparison of the actual value and the theoretical value of the outer diameter of the load, the step of stopping the trolley is carried out if the difference between at least one of said actual values ​​and its theoretical value is greater in absolute value than a predefined limit value.

[0026] It is also possible to provide, for example, that:

[0027] - the step of digitally processing said image obtained in the acquisition step comprises a sub-step of detecting a first inner circle located on a front face of the annular load and corresponding to the inner diameter of said annular load, and a second inner circle located on a rear face of the annular load and corresponding to an inner surface of said load,

[0028] - the calculation of the actual value of the depth of the annular charge is carried out from the diameter DI Ô of the first inner circle, the diameter D17 of the second inner circle, and the distance d between said 3D camera and the front face of the charge according to the following equation: "back" of the annular charge means the front face of the charge that is oriented away from the 3D camera. "Front face" of the annular charge means the front face of the charge that is oriented toward the 3D camera. The back and front faces delimit the thickness of the charge.

[0029] According to one characteristic, the actual value of the depth of the annular charge is equal to the maximum deviation between the coordinates of the points of an interior surface of the annular charge included between the interior circles, said deviation being measured along the axis of the reference frame oriented along the line of sight of said 3D camera.

[0030] According to another characteristic, the step of digitally processing said image obtained in the acquisition step comprises a sub-step of detecting a circle located on the front face of the annular load and corresponding to the external diameter of the annular load. For example, the acquisition step comprises the following successive sub-steps:

[0031] - a first sub-step of acquiring at least one image;

[0032] - a sub-step of advancing the trolley towards the load by a predefined distance; and

[0033] - a second sub-step of acquiring at least one image taken when the carriage has traveled said predefined distance,

[0034] - and in which the sub-step of calculating the actual value of the outer diameter of the annular load is carried out from the image obtained in the first acquisition sub-step, and the sub-step of calculating the actual value of the depth (P) of the annular load is carried out from the image obtained in the second acquisition sub-step.

[0035] Advantageously, the digital processing step comprises a sub-step of filtering said image obtained in the acquisition step which is carried out before any other sub-step of the digital processing step. This filtering sub-step makes it possible to reduce the quantity of data to be processed by filtering the points of the images obtained in the acquisition step to keep only the points forming part of a region of particular interest. By limiting the calculations to the reduced domains of the areas of particular interest, the method accelerates the obtaining of the results without degrading their quality. By limiting the data to the areas of interest, the size of the memory required by the control and digital image processing module associated with the 3D cameras is also reduced.

[0036] Preferably, the step of acquiring said image of the load is carried out by a single 3D camera. Alternatively, the acquisition step can be carried out by several 3D cameras. Alternatively, the acquisition step can be carried out by one or more non-3D cameras allowing the reading of bar codes.

[0037] According to another aspect, the invention relates to an autonomous forklift truck comprising a vertically movable fork provided with at least one arm, at least one 3D camera for acquiring at least one image of point cloud data, said 3D camera being fixed to the autonomous forklift truck while being centered relative to the fork and having a line of sight oriented forward along a longitudinal axis of said truck, a control and digital image processing module associated with the 3D camera, a wireless telecommunications device, as well as a control unit for said truck configured for the execution of a method as described above.

[0038] Brief description of the figures

[0039] Other aims, characteristics and advantages of the invention will appear on reading the following description, given solely by way of non-limiting example, and made with reference to the appended drawings in which:

[0040] [Fig 1] is a perspective view of an autonomous forklift according to an exemplary embodiment of the invention;

[0041] [Fig 2] is a detail view of the forklift of Figure 1;

[0042] [Fig 3] schematically illustrates the forklift of Figure 1 in use;

[0043] [Fig 4] illustrates the flowchart of a method of lifting and transporting a load by a trolley of figure 1 according to an embodiment of the invention; and

[0044] [Fig 5] is a simplified example of an image acquired by a camera of the forklift in Figure 1 in the case of a ring load.

[0045] Detailed description of at least one embodiment

[0046] Figure 1 shows the main elements of an autonomous forklift 1 according to one embodiment of the invention.

[0047] The architecture of the forklift 1 is given by way of example and does not limit the invention to the sole configuration of the architecture presented. It is understood that the invention also relates to forklifts intended to operate in manual mode and which have been adapted to allow a second mode of operation in autonomous mode.

[0048] The self-propelled forklift 1 illustrated in Figure 1 comprises a lifting member 2 comprising an apron 3 which supports a fork 4 comprising two arms 4a, 4b spaced laterally and extending towards the front of the truck. Alternatively, the fork 4 could comprise a single arm.

[0049] The apron 3 forms a frame. The apron 3 is provided with a horizontal upper crosspiece 3a, and two arms 3b, 3c extending the upper crosspiece 3a vertically downwards.

[0050] The fork 4 also comprises two uprights 4' a, 4' b which are fixed to the apron 3 and which each support one of the arms 4a, 4b. Each of the uprights 4' a, 4' b is fixed to one of the arms 3b, 3c of the apron.

[0051] The fork arms 4a, 4b are generally used to fit into insertion tunnels provided in the transport pallets supporting the loads to be lifted. The uprights 4'a, 4'b allow the arms 4a, 4b to be raised in order to be able to lift a pallet to be transported or another type of load and to be able to place or pick up a pallet or another type of load at height.

[0052] The fork 4 is able to move in translation in a vertical plane V defined by the apron 3, along a vertical mast 5 of the truck. The uprights 4'a, 4'b can slide along the mast 5. The arms 4a, 4b of the fork are movable between an extreme high position, and an extreme low position which is illustrated in figure 1 and which corresponds to a rolling position. In the extreme low position, the arms 4a, 4b are located at a distance from the ground.

[0053] The longitudinal axes of the arms 4a, 4b are parallel. These longitudinal axes are oriented parallel to a horizontal axis X, and define a horizontal plane H called the lifting plane. The arms 4a, 4b of the fork 4 are perpendicular to the vertical plane V. The arms 4a, 4b of the fork 4 are also preferably laterally movable relative to each other. Alternatively, the arms 4a, 4b could also be telescopic or retractable, and / or angularly orientable around their longitudinal axis.

[0054] In a manner known per se, the trolley 1 is equipped with a drive system 6 allowing the trolley 1 to move. The drive system comprises at least one electric or thermal motor (not shown) allowing the wheels of the trolley 1 to be driven.

[0055] The truck 1 is also equipped with an on-board location device 7, an on-board wireless telecommunications device 8 and an on-board control unit 9 (figure 3) receiving information from the location device 7 and the wireless telecommunications device 8 to autonomously control the movement of the forklift.

[0056] The trolley 1 is also equipped with at least one 3D camera 10 with time-of-flight measurement (acronym TOE for “Time Of Elight” in English) and an associated digital image control and processing module 11 (figure 3), called the vision module, which controls the taking of images by the 3D camera and which receives and interprets the images captured by the 3D camera. In the remainder of the description, the module 11 will be called the vision module.

[0057] In a manner known per se, the 3D camera 10 is capable of capturing an image of an object and restoring a cloud of points of relative coordinates measured with respect to a reference frame associated with the 3D camera. The reference frame associated with the 3D camera 10 comprises a reference frame R composed of three orthogonal axes XI, Y l, Z l, as illustrated in FIG. 2. The axis Zl of the reference frame is here oriented along the line of sight of the 3D camera 10, and the axis Y l of the reference frame is oriented along a horizontal axis Y perpendicular to the line of sight of the 3D camera 10. A 3D camera is capable of measuring distances along the three axes of the reference frame associated with it. For example, as illustrated, the horizontal, vertical or depth offset with respect to the 3D camera 10 is measured along the axes Y l, XI or Z l, respectively.

[0058] The 3D camera 10 is distinct from the location device 7. The 3D camera 10 is here distinct from the vision module 11. Alternatively, the 3D camera 10 and the vision module 11 could form a single unit.

[0059] The control unit 9 comprises the hardware and software means for controlling the operation of the drive system 6 based on the information received from the location device 7 and the telecommunications device 8.

[0060] The control unit 9 controls the operation of the drive system 6 also based on data from the vision module 11 and is configured to communicate with it. Alternatively, the vision module 11 could be integrated into the control unit 9. The control unit 9 also makes it possible to control the autonomous movement of the lifting member 2.

[0061] As illustrated in Figures 1 and 2, the 3D camera 10 is centered relative to the fork 4 and its line of sight is oriented forward along a longitudinal axis of the carriage 1. The 3D camera 10 is fixed to the apron 3 at a constant height relative to the lifting plane H and without the possibility of relative movement relative to said apron. The 3D camera 10 is movable jointly with the fork 4. The 3D camera 10 is here fixed in the lower part of the apron 3 above the lifting plane H. In variants not illustrated, the 3D camera 10 can be fixed to the apron 3 at the level of the lifting plane H or below this plane.

[0062] As will be described in more detail later, the 3D camera 10 is capable of capturing images of the environment located in front of the forklift 1, to determine the actual size of the loads to be lifted and transported by the forklift.

[0063] The wireless telecommunications device 8 is configured to communicate with the control unit 9 and with a warehouse management computer system 18 (in English "Warehouse Management System" or WMS) which is remote from the trolley 1 and intended to manage the operations of a storage warehouse and to control a fleet of trolleys 1.

[0064] Each trolley 1 receives, via the telecommunications device 8, instructions in the form of periodic digital messages sent by the WMS system 18 concerning missions assigned to it relating to movements to be carried out and loads to be transported. Each trolley 1 is capable of transmitting to the WMS system 18 digital messages representative of the status of the missions assigned to it. A trolley 1 can, for example, report an error encountered during the execution of a mission by sending an error code.

[0065] A method 20 for verifying the safety of a load socket according to the invention will now be described with reference to FIG. 4. In the method to be described, the load is annular. An annular load generally comprises a support consisting of a hollow cylindrical core, generally provided with solid or radiused circular-shaped edges, intended to receive a wire or cable which is wound around the core. Alternatively, an annular load may be a tire.

[0066] The method 20 begins with a preliminary reception step 21 in which the wireless telecommunications device 8 of the trolley receives an instruction relating to a load to be transported and constituting a mission assigned to the trolley 1 by the WMS system 18. The instruction includes information relating to the type of load to be transported, the dimensions of the load, the current position of the load and its destination.

[0067] In particular regarding the dimensions of the annular load, the instruction received may for example include the theoretical value of the outer diameter, the theoretical value of the inner diameter and / or the theoretical value of the depth. It is understood that ideally, the theoretical value of each dimension of a given load should correspond to the actual value of this dimension. However, it may happen that the theoretical value received does not correspond to the actual value of the load present in situ, which may lead to accident risks.

[0068] The information received, in particular the information relating to the dimensions of the load to be transported, is stored in a memory of the trolley 1. During the following movement step 22, the control unit 9 controls the operation of the trolley 1 to bring it closer to the rack 13 and the lifting of the arms of the fork 4 to position them relative to the load 12 to be lifted. The trolley 1 is controlled by the control unit 9 according to the data from the location device 7 and the instruction received in the reception step 21.

[0069] The method 20 continues with a step 23 of acquiring at least one image of the load 12 by the 3D camera 10 which is controlled by the vision module 11. The image acquisition is carried out at a predefined distance DI (figure 3) from the load 12. When the carriage is located at this predefined distance D1, the control unit 9 stops the carriage 1 and sends an image acquisition request to the vision module 11 which controls the taking of images by the associated 3D camera 10. The 3D camera 10 thus captures at least one image of the load 12 located at the front of the carriage 1 and sends it back to the vision module 11. A simplified example of a captured image of an annular load is illustrated in figure 5. The images captured by the 3D camera 10 restore a cloud of points with coordinates XI, Y1, Z1 in the reference frame R associated with the 3D camera 10.

[0070] After the acquisition step 23, the method continues with a step 24 of determining the actual value of each dimension received with the instruction from the WMS system 18, that is to say the value that each dimension actually has for which the trolley received a theoretical value in the reception step 21. The determination of the actual value is carried out from at least one image which is obtained in the acquisition step 23.

[0071] The determination step 24 comprises a digital processing step 25 of the images obtained carried out by the vision module 11. It should be noted that the digital processing of the images can begin as soon as the image captured by the 3D camera 10 is made available to the vision module 11. The digital processing step 25 comprises a sub-step 25b of calculating the dimensions of the load 12 actually present on the shelf 13.

[0072] For example, the digital processing step comprises a sub-step 25a of detecting circles 14, 16 located on a front face of the load 12, and a circle 17 located on a rear face of the load 12 (figure 5).

[0073] The detection of the circles is carried out so that the circle 14 is the circle perceived on the front face of the load and which corresponds to the outer surface of the load 12, and the circles 16, 17 are respectively the circles perceived on its front face and on its rear face and corresponding to the inner surface of the load 12. The detection of the circles 14, 16 and 17 is carried out using known circle detection methods, for example of the Hough transform type.

[0074] As previously indicated, the digital processing step includes a sub-step 25b of calculating the actual value of the dimensions of the load.

[0075] In this sub-step, the actual outer and inner diameters of the load are considered to be equal to the diameters DM, DI Ô (figure 5) of the outer and inner circles 14 and 16 which are perceived on the front face of the load. During this sub-step 25b, the diameter D17 of the inner circle 17 is also determined. The value of the diameter D 17 is less than that of the diameter DI Ô taking into account the angle of escape of the image.

[0076] In this sub-step 35, the calculation of the actual value of the depth P of the load is carried out from the diameter values ​​DI Ô and D17 of the circles 16, 17 determined in the circle detection sub-step 25a, and from the value of the distance d between the front face of the annular load and the 3D camera 10 which is determined by the latter, by applying the following equation:

[0077] Alternatively, in another embodiment used for example when the contrast between the front and rear faces of the load 12 is not sufficient, the actual value of the depth P of the annular load is calculated as being equal to the maximum difference between the coordinates of the points of the interior surface 15 of the annular load 12, between the circles 16 and 17, said difference being measured along the axis of the reference frame R oriented along the line of sight of the 3D camera 10.

[0078] After the actual values ​​of the load have been determined by the vision module 11, the control unit 9 has information relating to the dimensions of the load obtained by two separate channels, namely by the vision module 11 on the one hand and by the WMS system 18 on the other hand.

[0079] Referring again to Figure 4, after the determination step 24, the method continues with a step 26 of comparing the actual values ​​determined during the determination step 24 and the theoretical values ​​of the load dimensions received in step 21.

[0080] In this case, in the described embodiment, the actual values ​​of the outer diameter, the inner diameter and the depth of the load are compared with the corresponding theoretical values. Alternatively, it could be possible to determine only one or two of these actual values ​​of the load for the comparison step 26.

[0081] During comparison step 26, if the difference between the actual value and the theoretical value of one of the dimensions of the load is greater in absolute value than a predefined associated limit value, the control unit 9 commands the stopping of the trolley 1 for reordering by an operator (step 27).

[0082] This limit value can be determined according to the permissible tolerances relating to the safety requirements of lifting and transport operations. The limit value can be specific to each dimension of the load considered.

[0083] During step 27 of stopping the trolley, the control unit 9 can transmit to the WMS system 18 an error message representative of the error encountered.

[0084] On the contrary, if the actual values ​​correspond to the theoretical values ​​associated with the limit values, the control unit of the truck controls the lifting and transport operation (step 28). This lifting and transport operation can be carried out according to a predetermined lifting and transport scenario which is stored in the control unit 9 of the truck and which includes safety parameters specific to the theoretical dimensions of the load. For example, the safety parameters define in which aisles or openings of the warehouse the truck can move according to the dimensions of the load.

[0085] Alternatively, before controlling the lifting and transport operation, the control unit 9 can modify the safety parameters according to the actual dimensions of the load and then carry out the control according to the lifting and transport scenario with the adapted safety parameters.

[0086] In the implementation example which has just been described, the acquisition step 23 of one or more images is carried out at the sole distance DI from the load 12. Alternatively, the acquisition step 23 may comprise a first sub-step of acquisition at the distance D1, followed by a second sub-step of acquisition at a distance D2 reduced relative to the load which therefore occurs after the carriage has moved forward.

[0087] This two-step acquisition can be useful for loads of large dimensions, in particular annular loads for which the viewing angle of the 3D camera 10 may be too small to capture both the inner surface and the outer surface of the load. In this case, the first acquisition sub-step is carried out so as to be able to calculate the actual values ​​of the outer diameter and the inner diameter of the load and the second acquisition sub-step is carried out so as to be able to calculate the actual value of the depth of the load 12.

[0088] In the illustrated embodiment, the digital processing step 25 comprises a preliminary point filtering sub-step 25c. This sub-step 25c is carried out before any other sub-step of the digital processing step 25 and makes it possible to reduce the quantity of data to be processed by filtering the points of the images obtained in the acquisition step to keep only the points forming part of a region of particular interest. For example, the inner surface 15 of the annular charge 12 may constitute a region of particular interest (FIG. 5). By limiting the calculations to the reduced domains of the regions of particular interest, the method accelerates the obtaining of the results without degrading their quality. By limiting the data to the regions of interest, the size of the memory required by the vision module 11 is also reduced. Alternatively, it remains possible not to provide this filtering sub-step 25c.

[0089] In the implementation example described, step 24 of determining the actual values ​​of the dimensions of the load is carried out by digital processing 25 of the images obtained by the vision module 11.

[0090] In an alternative embodiment, the determination step 24 could comprise a step of reading a barcode on said image obtained in the acquisition step 23, followed by a step of extracting a real value of the or each dimension considered of the load from a table contained in the memory of the forklift as a function of the barcode read.

[0091] Furthermore, the example of implementation of the method has been described with an annular load. It is not outside the scope of the invention when the load is a palletized load. By "palletized load" is meant a pallet supporting a load. A pallet is a platform which generally comprises a floor supported by spacers or two floors connected by spacers. A pallet can also be provided with feet supporting the platform.

[0092] For a palletized load, the dimensions taken into consideration may be the height, depth and / or width of the load taken alone.

[0093] For example, the digital processing step may include a sub-step of detecting the front face of the load and a bottom face of the load using conventional computer vision algorithms. The width and height dimensions of the load are then calculated from the front face images, while the depth dimensions are calculated from the bottom face images.

Claims

CLAIMS 1. Method (20) for lifting and transporting a load by an autonomous forklift truck comprising a vertically movable fork provided with at least one arm, said method being characterized in that it comprises: a step (21) of receiving by the truck an assigned mission of moving the load to be lifted and transported which comprises a theoretical value of at least one dimension of said load; a step (22) of moving the autonomous forklift truck in front of the load to be lifted and transported, a step of acquiring (23) at least one image of the load by at least one camera fixed on the autonomous forklift truck while being centered relative to the fork and having a line of sight oriented forward along a longitudinal axis of said truck; a step of determining (24) a real value of said dimension of the load from said image obtained in the acquisition step (23), a step (26) of comparing the actual value of said dimension of the load determined in the determining step (24) and the theoretical value of said dimension of the load received in the receiving step (21), and a step (27) of stopping the trolley if the difference between the actual value of said dimension and its theoretical value is greater in absolute value than a predefined limit value, or a step of lifting and transporting (28) the load if the difference between the actual value of said dimension and its theoretical value is less than or equal in absolute value to the predefined limit value.

2. Method according to claim 1, in which said camera is a 3D camera restoring a cloud of points of coordinates measured in a reference frame (R) associated with said 3D camera, and in which the determination step (24) comprises a step (25) of digital processing of said image obtained in the acquisition step (23) which comprises a sub-step (25b) of calculating the real value of said dimension of the load.

3. The method of claim 1, wherein the determining step (24) comprises a step of reading a barcode on said image obtained in the acquisition step (23), and a step of extracting the real value of said load dimension of a table contained in a forklift memory based on the barcode read.

4. Method according to claim 2, in which: the load to be lifted and transported is annular, the mission assigned to the receiving step (21) comprises theoretical values ​​of the depth (P) and the outer diameter of the annular load, the digital processing step (25) comprises sub-steps (25b) of calculating the actual values ​​of the depth (P) and the outer diameter of the annular load, the comparison step (26) comprises the comparison of the actual value and the theoretical value of the depth of the load, and the comparison of the actual value and the theoretical value of the outer diameter of the load, the step (27) of stopping the carriage is carried out if the difference between at least one of said actual values ​​and its theoretical value is greater in absolute value than a predefined limit value.

5. Method according to claim 4, in which: - the step (25) of digital processing of said image obtained in the acquisition step comprises a sub-step (25a) of detecting a first inner circle (16) located on a front face of the annular load and corresponding to the inner diameter of said annular load, and a second inner circle (17) located on a rear face of the annular load and corresponding to an inner surface of said load, - the calculation of the actual value of the depth (P) of the annular load is carried out from the diameter (D IÔ) of the first inner circle (16), the diameter (D17) of the second inner circle (17), and the distance (d) between said 3D camera and the front face of the load according to the following equation: P = d x ^è^ (Eq. l ) D17 6. Method according to claim 5, in which the actual value of the depth (P) of the annular charge is equal to the maximum deviation between the coordinates of the points of an interior surface of the annular charge included between the interior circles (16, 17), said deviation being measured along the axis of the reference frame (R) oriented along the line of sight of said 3D camera.

7. Method according to any one of claims 4 to 6, in which the step (24) of digital processing of said image obtained in the acquisition step comprises a sub-step (25a) of detecting a circle (14) located on the front face of the annular load and corresponding to the external diameter of the annular load.

8. Method according to any one of claims 4 to 7, in which the acquisition step (23) comprises the following successive sub-steps: - a first sub-step of acquiring at least one image; - a sub-step of advancing the carriage towards the load by a predefined distance; and a second sub-step of acquiring at least one image produced when the carriage has traveled said predefined distance, - and in which the sub-step of calculating the actual value of the external diameter of the annular load is carried out from the image obtained in the first acquisition sub-step, and the sub-step of calculating the actual value of the depth (P) of the annular load is carried out from the image obtained in the second acquisition sub-step.

9. Method according to any one of the preceding claims 2 or 4 to 8, in which the digital processing step (25) comprises a sub-step (25c) of filtering said image obtained in the acquisition step which is carried out before any other sub-step of the digital processing step (25).

10. Method according to any one of the preceding claims, in which the step of acquiring (23) said image of the load is carried out by a single 3D camera. 1 1. Autonomous forklift truck (1) comprising a vertically movable fork (4) provided with at least one arm, at least one 3D camera (10) for acquiring at least one image of point cloud data, said 3D camera being fixed to the autonomous forklift truck while being centered relative to the fork and having a line of sight oriented forward along a longitudinal axis of said truck, a module (1 1) for controlling and digitally processing images associated with the 3D camera (10), a wireless telecommunications device (8), as well as a control unit (9) of said truck configured for the execution of a method according to any one of claims 1 to 10.

Images