Autonomous forklift truck for lifting and transporting a load, and associated method

Abstract

This autonomous forklift truck (1) comprises: - a vertically movable fork (4) provided with at least two arms (4a, 4b) for lifting loads, - a drive system (7) for moving the forklift truck, and - a control unit (9) able to control the operation of the drive system to autonomously guide the forklift truck and able to control the vertical movement of the fork (4). The forklift truck further comprises a contactless detection device (10) for contactlessly detecting a load movable together with the fork, which device is arranged above the arms (4a, 4b) of the fork. The contactless detection device (10) is able to emit a light beam sweeping at least one predefined planar detection zone located above the arms of the fork in order to detect the presence of a load to be lifted.

Description

[0001] DESCRIPTION

[0002] TITLE: Autonomous forklift for lifting and transporting loads, and associated method

[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, in order to limit the risk of transported loads falling, forklifts are traditionally equipped with mechanical sensors placed on the vertical uprights of the fork used for lifting and transporting these loads.

[0011] Such mechanical sensors are in the form of pivoting stops between a deployed position corresponding to a load that is absent or not resting against said stop, and a retracted position corresponding to a load resting against said stop. However, when picking up loads from storage racks, it is often difficult for the fork to reach a position allowing the mechanical sensors installed at the bottom of the fork to detect the presence of the load to be moved. This is particularly the case when the load to be picked up is offset inwards relative to the racks. It then sometimes becomes necessary to replace the existing storage racks with racks of a different design.

[0012] To overcome this drawback, one solution is to equip forklifts with telemeters.

[0013] However, rangefinders that use point measurement do not allow for the detection of all types of load. This may be the case, for example, when the load to be detected includes holes or bores, as is the case for tires.

[0014] Statement of the invention

[0015] In view of the above, the aim of the invention is therefore to propose an autonomous forklift capable of detecting remotely and without contact the loads to be transported, with high detection reliability regardless of the size or shape of the loads to be detected.

[0016] The invention relates to an autonomous forklift truck comprising a vertically movable fork equipped with at least two arms for lifting loads, a drive system for moving the forklift truck and a control unit capable of controlling the operation of the drive system to autonomously guide the forklift truck.

[0017] According to a general characteristic, the forklift truck further comprises a device for contactless detection of a load, said detection device being movable jointly with the fork and arranged above the arms of said fork.

[0018] The detection device is capable of emitting a light beam scanning at least one predefined flat detection zone located above at least one of the arms of the fork to detect the presence or absence of a load to be lifted.

[0019] According to another general characteristic, the control unit receives information representative of the presence or absence of the load to be lifted in said predefined flat detection zone from the contactless detection device.

[0020] According to another general characteristic, the control unit is able to control the operation of the drive system and the vertical movement of the fork based on this information.

[0021] The integration of such a contactless detection device makes it possible to detect any type of load remotely, increasing the level of reliability and security compared to conventional detections.

[0022] It also becomes possible to safely pick up a load "at the end of the fork" of the truck. This means there is no need to modify the design of existing storage racks.

[0023] Advantageously, said predefined flat detection zone scanned by the light beam emitted by the contactless detection device is horizontal.

[0024] Preferably, said predefined flat detection zone scanned by the light beam emitted by the contactless detection device is located above the two arms. In this case, said flat detection zone can extend laterally at least partly beyond the transverse dimensions of said fork arms.

[0025] Alternatively, the contactless detection device may scan two distinct planar detection zones, namely a first predefined planar detection zone located above a first arm of the fork and a second predefined planar detection zone located above a second arm of the fork different from the first.

[0026] According to another characteristic, the fork comprises at least two uprights supporting the arms, the contactless detection device being arranged on one of the uprights.

[0027] In a particular embodiment, the autonomous forklift truck further comprises a stop arranged on each of the fork uprights and pivotally mounted between a deployed position corresponding to a load that is absent or not bearing against said stop and a retracted position corresponding to a load bearing against said stop, the contactless detection device arranged on said upright being located above the associated stop. Alternatively, it remains possible to provide that the truck is not equipped with these stops.

[0028] The autonomous forklift comprises an on-board location device configured to acquire position data of the forklift and communicating with the control unit. Preferably, the non-contact detection device is separate from the location device.

[0029] According to another aspect, the invention relates to a method of lifting and transporting a load by an autonomous forklift as described above.

[0030] The lifting and transporting process includes:

[0031] - a step of positioning the fork arms in relation to the load,

[0032] - at least a first step of detection of the load by the contactless detection device,

[0033] - a step of lifting the load if the load is detected in at least a first predefined flat detection zone scanned by the light beam emitted by the contactless detection device during the first detection step, and

[0034] - a step of moving the autonomous forklift and transporting the load.

[0035] For example, the first predefined detection zone is defined by four points delimiting a rectangle.

[0036] In a particular embodiment, the method may comprise, before the step of lifting the load, a second step of detecting the successive load by the contactless detection device, the step of lifting the load being carried out if the load is detected during the second detection step. For example, the step of lifting the load is carried out after a timing step itself carried out after the first detection step.

[0037] Preferably, the second step of detecting the load can be carried out in at least one second predefined detection zone located inside said first detection zone on the side of the contactless detection device.

[0038] In one embodiment, said load detection step is performed in a flat detection zone which is common to the fork arms.

[0039] In another embodiment, said load detection step is carried out in two separate, flat detection zones, each specific to one of the two arms of the fork.

[0040] According to one characteristic, the method may comprise, during the step of moving the autonomous forklift and transporting the load, a sub-step of controlling the rotation of the load by the contactless detection device, the control of the rotation of the load being carried out in relation to each detection zone which is specific to one of the two arms of the fork, the step of moving the autonomous forklift and transporting the load being stopped if the load is not detected simultaneously in said two detection zones.

[0041] According to another characteristic, the method may comprise, during the step of moving the autonomous forklift and transporting the load, a sub-step of controlling the position of the load by the contactless detection device, the control of the position of the load being carried out in relation to said first detection zone, the step of moving the autonomous forklift and transporting the load being stopped if the load is not detected in said first detection zone.

[0042] According to another characteristic, the method may comprise, during the step of moving the autonomous forklift and transporting the load, a sub-step of controlling the position of the load by the contactless detection device, the control of the position of the load being carried out in relation to at least one predefined detection zone representative of a sliding of the load and located outside said first detection zone on the side of the contactless detection device, the step of moving the autonomous forklift and transporting the load being stopped if the load is detected in said predefined detection zone representative of a sliding of the load.

[0043] Brief description of the figures

[0044] 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:

[0045] [Fig 1] is a perspective view of an autonomous forklift according to an exemplary embodiment of the invention;

[0046] [Fig 2] schematically illustrates the forklift of Figure 1 in use;

[0047] [Fig 3] is a partial top view of the forklift of Figure 1 in which a first load detection zone is schematically represented;

[0048] [Fig 4] illustrates the flowchart of a method for lifting and transporting a load according to one embodiment of the invention;

[0049] [Fig 5] is a partial top view of the forklift of Figure 1 in which two load tipping detection zones are schematically represented;

[0050] [Fig 6] illustrates a flowchart of a method of lifting and transporting a load according to another embodiment of the invention;

[0051] [Fig 7] is a partial top view of the forklift of Fig. 1 showing schematically first and second load detection zones;

[0052] [Fig 8] illustrates a flowchart of a method for lifting and transporting a load according to another embodiment of the invention; and [Fig 9] is a partial top view of the forklift of Figure 1 in which a load slip detection zone is schematically represented.

[0053] Detailed description of at least one embodiment

[0054] Figure 1 shows the main elements of an autonomous forklift 1 according to one embodiment of the invention.

[0055] 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 automatic mode.

[0056] The self-contained forklift 1 illustrated in Figure 1 comprises a fork carriage 3 provided with a fork 4 comprising two arms 4a, 4b spaced laterally and extending forward. The fork 4 also comprises two uprights 4'a, 4'b each supporting one of the arms 4a, 4b.

[0057] The arms 4a, 4b of the fork are generally used to insert 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.

[0058] The fork 4 is able to move in translation in a vertical plane V defined by the fork-carrying carriage 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 parallel. The longitudinal axes of the arms 4a, 4b of the fork 4 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 are also preferably movable laterally relative to each other.

[0059] Alternatively, the arms of the fork 4 could also be telescopic or retractable, and / or angularly orientable around their longitudinal axis.

[0060] In the illustrated embodiment, the carriage 1 further comprises a mechanical stop 6 arranged on each of the uprights 4'a, 4'b of the fork and pivotally mounted between a deployed position corresponding to a load absent or not bearing against said stop, and a retracted position corresponding to a load bearing against said stop. The stops 6 are mounted at the lower end of the uprights 4'a, 4'b. In Figure 1, one of the stops 6 is shown in the deployed position and the other stop is shown in the retracted position for reasons of understanding.

[0061] In a manner known per se, the trolley 1 is equipped with a drive system 7 allowing the trolley 1 to move. The drive system comprises at least one electric or thermal motor (not shown) allowing the wheels (not referenced) of the trolley 1 to be driven.

[0062] The truck 1 is also equipped with an on-board location device 8, and an on-board control unit 9 (figure 2) receiving information from the location device 8 to autonomously control the movement of the forklift.

[0063] The control unit 9 comprises the hardware and software means for controlling the operation of the drive system 7 based on the information received from the location device 8. The control unit 9 also makes it possible to control the automatic movement of the fork 4.

[0064] The carriage 1 is also equipped with a contactless detection device 10 which is arranged above the arms 4a, 4b of the fork 4. The detection device 10 is fixed to the upright 4'a of the fork and is located above the arms 4a, 4b. In the illustrated embodiment, the detection device 10 is fixed to the upright 4'a above the associated stop 6. The contactless detection device 10 is movable together with the upright 4'a of the fork. The detection device 10 is separate from the location device 7.

[0065] As will be described in more detail below, the detection device 10 is capable of emitting a light beam scanning at least one predefined flat detection zone located above the arms 4a, 4b to detect the presence of a load to be lifted by intersection of the light beam with said load inside said predefined flat detection zone.

[0066] The detection device 10 is configured to acquire position data of the load to be lifted, and to transmit to the control unit 9 information representative of the presence or absence of the load detected within the predefined flat detection zone. Depending on the information received, the control unit 9 then controls the operation of the drive system 7 and the vertical movement of the fork 4. The detection device 10 may for example be a laser sensor of the Lidar type.

[0067] We will now describe, with reference to figures 2 and 3, the operating principle of the autonomous forklift 1 for detecting the presence or absence of a load 12 to be lifted on a shelf 13.

[0068] In an initial phase, the control unit 9 controls the operation of the carriage 1 to bring it closer to the rack 13 and to raise the arms of the fork 4 to position them relative to the load 12 to be lifted. The carriage 1 is controlled by the control unit 9 according to the data from the location device 8. During its movement, the carriage 1 is controlled to maintain a minimum safety distance d relative to the rack 13. During the initial phase, the carriage 1 is controlled to maintain a minimum horizontal safety distance between the cantilevered end of the arms of the fork 4 and the rack 13 in order to allow the arms to pass safely over the rack 13.

[0069] Then, the detection device 10 emits a light beam 14 scanning at least a first predefined flat detection zone 15 located above the arms 4a, 4b of the fork. The vertical projection of the detection zone 15 covers the arms 4a, 4b of the fork and the transverse space separating these arms.

[0070] In the illustrated embodiment, the detection zone 15 is defined by four distinct points delimiting a rectangle, such as points B, C, D and E in FIG. 3. Point A schematically represents the emission point of the light beam 14 at the output of the device 10. The detection zone 15 is here horizontal. Alternatively, it could be possible to provide a zone 15 inclined relative to the horizontal.

[0071] The long side of the rectangle delimited by points B, C, D and E has a length y greater than the transverse dimensions of the arms 4a, 4b of the fork, and the detection zone 15 is centered relative to these arms. In other words, the flat detection zone 15 extends laterally beyond the transverse dimensions of the arms 4a, 4b of the fork. As an indication, the width w of the short side of the rectangle delimited by points B, C, D and E, and therefore the depth of the detection zone 15, may be equal to 50 mm.

[0072] The detection device 10 is configured to detect whether the load 12 is within the detection zone 15. The load 12 is detected by the device 10 as being present when it intersects the light beam 14 and is within the detection zone 15. The detection device 10 is capable of detecting that the load is within the first detection zone 15 by a distance measurement.

[0073] If there is no intersection of the light ray 14 emitted by the device 10 with the load, or if this intersection exists but the detection device 10 detects that the distance separating it from the load 12 is outside the predefined flat detection zone 15, then the device 10 detects an absence of the load 12 in said detection zone.

[0074] A method 20 for lifting and transporting a load by the autonomous forklift 1 will now be described. The method 20 is illustrated in FIG. 4. The method 20 begins with the pre-positioning step 21, during which the control unit 9 controls the forklift 1 to position it vertically above the load 12 to be lifted and to position the arms 4a, 4b of the fork 4 vertically at the level of the latter.

[0075] During the next positioning step 22, the control unit 9 controls the carriage 1 to bring the arms 4a, 4b closer to the load 12.

[0076] The method then continues with a first step 23 of detecting the load carried out by the device 10. The device 10 detects whether the load 12 is located inside the detection zone 15 (Figure 3). This is the case if the load 12 intersects the light ray 14 emitted by the device 10 and if the load is located inside the detection zone 15. The device 10 transmits to the control unit 9 the information representative of the presence or absence of the load to be lifted in the detection zone 15.

[0077] If the load 12 is not detected inside the detection zone 15 by the device 10, the control unit 9 initializes in step 24 a time delay value T equal to a predetermined value t. The predetermined value t can be configured by the control unit 9 according to the speed of movement of the carriage 1. The control unit 9 checks using sensors (not referenced) in the following step 25, whether the minimum safety distance d has been reached or whether the fictitious destination point has been reached. If this is the case, the control unit 9 stops the carriage 1 in step 26 to allow a reset by an operator. If this is not the case, the control unit 9 controls the carriage 1 to continue to bring the arms 4a, 4b closer to the load 12 by starting again at step 22.

[0078] In the illustrated embodiment, if the load 12 is detected inside the detection zone 15 by the device 10 during step 23, the control unit 9 decreases the time delay value T by a predetermined value x during a step 28a, and checks in the following step 28b whether the time value T is less than or equal to 0. If this is not the case, the control unit 9 controls the carriage 1 to continue to bring the arms 4a, 4b closer to the load 12 by starting again at step 22.

[0079] If this is the case, this means that the time delay has elapsed, and the control unit 9 carries out the lifting of the load by issuing a lifting instruction in step 29. Then, the control unit 9 controls the movement of the trolley 1 and the transport of the load during step 30. To do this, the control unit 9 uses the information received from the location device 8 to move the forklift 1 to the intended destination of the load 12 to be transported.

[0080] In the described embodiment, the method comprises a detection step 23 followed by a timing step. Alternatively, the method may comprise only the detection step 23 without resorting to a timing.

[0081] In the described implementation mode, the initialization of the time delay T is carried out after the detection step 23, when the load is not detected in the detection zone 15. Alternatively, the method could comprise an initialization of the time delay carried out before the positioning step 22.

[0082] In the implementation described, in detection step 23, the detection zone 15 of the detection device is common to the two arms 4a and 4b of the fork 4. In other words, the vertical projection of the detection zone 15 covers the arms 4a, 4b of the fork and the transverse space separating these arms.

[0083] Alternatively, it could be possible to provide for each of the arms 4a, 4b of the fork a first detection zone specific to it. In other words, the detection device 10 (figures 1 and 2) is capable of emitting a light beam scanning a first detection zone 15a specific to the arm 4a of the fork and located above this arm 4a and a first zone 15b specific to the arm 4b, located above this arm 4b and distinct from the first detection zone 15a as illustrated in figure 5.

[0084] The vertical projection of the first detection zone 15a covers the arm 4a of the fork and the vertical projection of the first detection zone 15b covers the arm 4b. The first zone 15a is here defined by four distinct points defining a rectangular zone such as B, C, D' and E', and the second zone 15b is defined by four distinct points defining another rectangular zone such as B', C', D and E.

[0085] In another variant of implementation of the method of figure 4 illustrated in figure 6, in which the identical steps bear the same references, a second detection step 32 is provided during which the device 10 performs a detection of the load 12 inside a second detection zone 17 illustrated in figure 7. In this mode of implementation, there is no timing step.

[0086] In the illustrated embodiment, this second detection zone 17 is defined by four distinct points delimiting a rectangle having a side of long length common to the rectangle defined by the points B, C, D and E of the first detection zone 15. The second detection zone 17 is defined by the points E, B, B', E'. The second detection zone 17 is located inside the first zone 15 and on the side of the detection device 10. The width of the short side of the rectangle delimited by the points E, B, B', E' is less than that of the short side of the rectangle delimited by the points B, C, D and E.

[0087] Referring again to Figure 6, if the load 12 is not detected inside the second detection zone 17 during the detection step 32, the method resumes at step 25 and then the control unit 9 brings the arms 4a, 4b closer to the load 12, resuming at step 22 if the minimum safety distance d has not been reached.

[0088] If the load 12 is detected inside the second detection zone 17 during the detection step 32, the control unit 9 lifts the load by issuing a lifting instruction (step 29), and then controls the movement of the carriage 1 and the transport of the load during step 30.

[0089] In this embodiment, the first and second detection zones 15, 17 are each common to the two arms 4a and 4b of the fork 4. Alternatively, it could also be possible to provide first detection zones each specific to one of the arms 4a, 4b as described previously, and second detection zones also each specific to one of the arms 4a, 4b.

[0090] In another variant of implementation of the method illustrated in figure 8, in which the identical steps bear the same references, a sub-step 30a of controlling the position of the load 12 is provided during step 30 of transporting the load.

[0091] During sub-step 30a, the detection device 10 can perform a detection of the load 12 using the detection zone 15 described previously. If the load is not detected in the zone 15, the control unit 9 considers that the transport of the load 12 cannot be ensured safely because this is representative of a slippage of the load and issues a stop instruction, to allow a re-ordering by an operator.

[0092] Alternatively, during sub-step 30a, the detection device 10 can perform a detection of the load 12 using a detection zone 18 representative of a sliding of the load, located outside the first detection zone 15 and corresponding to the triangle AFG, as illustrated in FIG. 9. This detection zone 18 is located on the side of the detection device 10 and at a distance from the rectangle defined by the points B, C, D and E of the first detection zone 15.

[0093] If the load is detected in the detection zone 18 representing the sliding of the load, the control unit 9 considers that the load has slipped during transport and issues in step 31 of the process an instruction to stop the trolley 1 to allow an operator to put it back in order.

[0094] In another embodiment of the method, it is possible to provide during step 30 of transporting the load a sub-step of controlling a possible rotation of the load. This is possible when for each of the arms 4a, 4b of the fork is associated a detection zone which is specific to it as described previously.

[0095] In this case, during step 30 of transporting the load, if the load is not detected simultaneously in the two detection zones associated with the two arms 4a, 4b of the fork, the control unit 9 considers that the load has undergone a rotation around the vertical axis Z during transport and issues an instruction to stop the carriage 1 at step 31 of the method to allow an operator to put it back in order.

Claims

DEMANDS 1. Self-contained forklift (1) comprising: - a vertically movable fork (4) equipped with at least two arms (4a, 4b) for lifting loads, - a drive system (7) for moving the forklift (1), and - a control unit (9) capable of controlling the operation of the drive system (7) to autonomously guide the forklift, and capable of controlling the vertical movement of the fork (4), characterized in that the forklift further comprises: - a non-contact load detection device (10), said detection device (10) being movable in conjunction with the fork (4) and disposed above the arms (4a, 4b) of said fork, the non-contact detection device (10) being capable of emitting a light beam (14) sweeping at least a predefined flat detection zone located above at least one of the arms (4a, 4b) to detect the presence or absence of a load to be lifted, the control unit (9) receiving information representative of the presence or absence of the load to be lifted in said predefined flat detection zone from the non-contact detection device (10), and being capable of controlling the operation of the drive system (7) and the vertical movement of the fork (4) according to this information.

2. Autonomous forklift according to claim 1, wherein said predefined flat detection zone swept by the light beam (14) emitted by the non-contact detection device (10) is horizontal.

3. Autonomous forklift according to claim 1 or 2, wherein the fork (4) comprises at least two uprights (4' a, 4'b) supporting the arms (4a, 4b), the non-contact detection device (10) being disposed on one of the uprights (4' a, 4'b).

4. Self-contained forklift according to claim 3, further comprising a stop (6) disposed on each of the uprights (4' a, 4' b) of the fork and pivotally mounted between a deployed position corresponding to a load not present or in support against said stop, and a retracted position corresponding to a load in support against said stop, the non-contact detection device (10) disposed on said upright (4' a, 4'b) being located above the associated stop (6).

5. Autonomous forklift according to any one of the preceding claims, comprising an on-board location device (8) configured to acquire position data of the forklift and communicating with the control unit (9), the non-contact detection device (10) being separate from the location device (8).

6. Method (20, 20') of lifting and transporting a load (12) by a self-propelled forklift (1) according to any one of the preceding claims, characterized in that it comprises: - a step (22) of positioning the arms (4a, 4b) of the fork (4) relative to the load (12), - at least one first step (23) of load detection (12) by the non-contact detection device (10), - a load lifting step (29) if the load (12) is detected in at least one first predefined planar detection zone (15) swept by the light beam (14) emitted by the non-contact detection device (10) during the first detection step, and - a step (30) of movement of the autonomous forklift and transport of the load.

7. Method according to claim 6, wherein said first predefined detection zone (15) is defined by four points delimiting a rectangle.

8. Method according to claim 6 or 7, comprising, before the step (29) of lifting the load, a second step (32) of detecting the subsequent load by the non-contact detection device (10), the step of lifting the load being carried out if the load is detected during the second step (32) of detection.

9. A method according to claim 6 or 7, wherein the step (29) of lifting the load is carried out after a step (28b) of the timing itself carried out after the first detection step (23).

10. Method according to claim 8, wherein the second stage (32) of load detection is carried out in at least one second predefined detection zone (17) located inside said first detection zone (15) on the side of the non-contact detection device (10). 1 1. Method according to any one of claims 6 to 10, wherein said load detection step is carried out in a plane detection zone (15, 17) which is common to the arms (4a, 4b) of the fork.

12. Method according to any one of claims 6 to 10, wherein said load detection step is carried out in two plane detection zones (15a, 15b) which are each specific to one of the two arms (4a, 4b) of the fork.

13. Method according to claim 12, comprising, during the step (30) of movement of the autonomous forklift and transport of the load, a substep of control of the rotation of the load by the non-contact detection device (10), the control of the rotation of the load being carried out in relation to each detection zone (15a, 15b) which is specific to one of the two arms (4a, 4b) of the fork, the step (30) of movement of the autonomous forklift and transport of the load being stopped if the load is not detected simultaneously in said two detection zones (15a, 15b).

14. A method according to any one of claims 6 to 13, comprising, during the step (30) of moving the autonomous forklift and transporting the load, a substep (30a) of checking the position of the load by the non-contact detection device (10), the checking of the position of the load being carried out in relation to said first detection zone (15), the step (30) of moving the autonomous forklift and transporting the load being stopped if the load is not detected in said first detection zone (15).

15. A method according to any one of claims 6 to 13, comprising, during step (30) of moving the forklift autonomous and load transport, a substep (30a) of load position control by the non-contact detection device (10), the load position control being carried out in relation to at least one predefined detection zone (18) representative of a load slip and located outside said first (15) detection zone on the side of the non-contact detection device (10), the step (30) of autonomous forklift movement and load transport being stopped if the load is detected in said predefined detection zone (18) representative of a load slip.

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