Automatic forklift for lifting and transporting goods and related method

Abstract

The invention relates to an automatic forklift (1) comprising:-a lifting member (2) having a vertically movable front fork (4) provided with at least one arm (4a, 4b) for lifting goods,-a drive system (6) for moving the forklift (1), and-a control unit (14) for controlling the operation of the drive system (6) for automatically guiding the forklift and for controlling the vertical movement of the front fork (4). The forklift further comprises non-contact detection means (8) for detecting obstacles, said detection means being movable together with the lifting member (2). The detection device (8) is capable of emitting a light beam that sweeps over at least one predetermined planar detection area in order to detect the presence of an obstacle. A detection device (8) is fixed to the lifting member to pass the light beam over the transported cargo.

Description

Technical Field

[0001] The present invention relates to the field of autonomous vehicles for autonomous transport of goods, such as autonomous forklifts. Background Art

[0002] Autonomous vehicles for transporting goods are increasingly being used to increase productivity and improve logistics management in manufacturing plants and warehouses.

[0003] For example, autonomous forklifts are such vehicles and are able to load, transport and position goods at height without human intervention.

[0004] However, in environments such as manufacturing plants or warehouses, human intervention is still necessary to supplement automated operations, such as checking that those operations are performed correctly or performing tasks that machines cannot perform alone. Therefore, these environments are shared between humans and autonomous machines.

[0005] In this work environment, personnel safety is of paramount importance and therefore specific procedures need to be implemented.

[0006] For example, during the operation of placing goods on a storage rack, it is necessary to check that the position on the rack intended to receive the goods is empty.

[0007] For this purpose, forklifts are usually provided with distance meters or photoelectric cells.

[0008] However, these technologies cannot detect all types of goods that may be present on storage racks. This is the case, for example, if the goods include holes or punctures, especially in the case of tires. Summary of the invention

[0009] In view of the above, an object of the present invention is therefore to provide an automatic forklift that can remotely and contactlessly detect goods that have been placed on a storage rack in a highly reliable detection manner, regardless of the size or shape of the goods to be detected.

[0010] The object of the present invention is to provide an automatic forklift, which comprises a lifting member, a drive system and a control unit, wherein the lifting member comprises a front fork which can be moved vertically and is provided with at least one arm for lifting goods, the drive system is used to move the forklift, and the control unit is capable of controlling the operation of the drive system to automatically guide the forklift and is capable of controlling the vertical movement of the front fork of the lifting member.

[0011] According to one general feature, the forklift further comprises a device for contactlessly detecting obstacles, the detection device being movable together with the lifting member and being capable of emitting a light beam directed toward the front of the forklift and sweeping across at least one predetermined planar detection area. The detection device is fixed to the lifting member so that the light beam passes over the transported goods.

[0012] The light beam passes over the transported goods, so the presence of the goods does not hinder the detection performed by the detection device.

[0013] According to another general feature, the forklift further comprises measuring means for determining the height of the front forks of the lifting member relative to the ground.

[0014] According to another general feature, the control unit receives information from the measuring device indicating the height of the front fork relative to the ground and information from the contactless detection device indicating the presence or absence of an obstacle in said predetermined planar detection area.

[0015] According to another general feature, the control unit is able to control the drive system and the vertical movement of the front fork of the lifting member as a function of this information.

[0016] With such an automated forklift, when placing goods on a storage rack, it is possible to check that the position on the rack intended to receive this goods is free of any other goods that could constitute an obstacle to its placement, and the forklift can move forward without the risk of pushing against goods already present and thus causing them to fall.

[0017] Furthermore, the integration of this contactless detection device enables remote detection of any type of cargo.

[0018] The detection device is advantageously fixed above a bracket supporting the lifting member of the front fork.

[0019] The carriage of the lifting member preferably comprises an upper crossbeam to which the detection device is fixed.

[0020] Preferably, the height of the front forks of the lifting member relative to the ground is determined continuously.Such continuous measurement further increases the reliability of the forklift.

[0021] According to another feature, the forklift further comprises means for determining a linear movement of the forklift. The determining means are capable of acquiring information representative of the movement of the forklift.

[0022] According to another feature, the control unit receives information representative of the movement of the forklift from the determination means and is able to control the operation of the drive system as a function of this information.

[0023] In a particular embodiment, the determination means comprises an all-or-nothing sensor oriented perpendicularly to the wheels of the forklift and coupled to the chassis of the forklift, and an indicator placed on the steering rod of the wheel, the all-or-nothing sensor being able to detect the indicator. The detection of the indicator corresponds to the orientation of the wheel according to the longitudinal axis of the forklift. The determination means further comprises means for measuring the movement of the forklift, the means for measuring the movement of the forklift being adapted to obtain information representative of the movement of the forklift.

[0024] In another specific embodiment, the determination device comprises a direction sensor oriented perpendicular to the wheels of the forklift and coupled to the chassis of the forklift and a magnetized target fixed to the steering rod of the wheel. The sensor is capable of detecting the position of the magnetized target according to the steering angle of the wheel. The determination device also comprises a device for measuring the movement of the forklift, and the device for measuring the movement of the forklift is capable of obtaining information representing the movement of the forklift.

[0025] When viewed from the side of the forklift, the light beam emitted by the detection device advantageously forms an oblique angle with the horizontal axis.

[0026] Alternatively, the light beam emitted by the detection device may be horizontal.

[0027] The light beam emitted by the detection device is preferably directed downwards.

[0028] Alternatively, the light beam emitted by the detection device may be directed upwards.

[0029] According to one feature, the predetermined planar detection area swept by the light beam emitted by the contactless detection device is defined by four points bounding a rectangle.

[0030] The automatic forklift includes an onboard positioning device configured to obtain forklift position data and communicate with the control unit. The non-contact detection device is preferably separate from the positioning device. The device for determining linear movement is preferably also separate from the positioning device.

[0031] According to another aspect, the object of the present invention is to provide a method for transporting and placing goods by means of an automated forklift as described above.

[0032] Transportation and placement methods include:

[0033] - a step of positioning a forklift relative to a structure intended to support the cargo in an approach position relative to said structure,

[0034] - a step of height-direction positioning of the front forks of the lifting member when the forklift has reached the access position and a step of obstacle detection by means of contactless detection means in the control volume swept by the light beam,

[0035] - if during the step of obstacle detection the contactless detection means detects no obstacle in the control volume, the step of moving the forklift forward relative to the structure to a placement position, and

[0036] - Steps for placing cargo on the structure at the placement location.

[0037] The obstacle detection step advantageously comprises:

[0038] - a sub-step of activating the detection means when the front fork of the lifting member has reached a predetermined first height relative to the ground during the height-direction positioning of the front fork, and

[0039] - A sub-step of deactivating the detection means when the front fork of the lifting member has reached a second height relative to the ground different from the predetermined first height.

[0040] The method advantageously comprises the step of controlling the forklift to move linearly to the placement position during the forward moving step.

[0041] The step of placing the load on the structure in the placement position is advantageously performed if the controlled movement of the forklift is purely linear or substantially linear.

[0042] By "substantially linear" it is meant that the movement of the forklift includes lateral variations relative to the purely linear movement, these variations remaining less than or equal to a predetermined limit value. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Other objects, features and advantages of the present invention will become apparent from a reading of the following description given by way of non-limiting example only and with reference to the accompanying drawings, in which:

[0044] Figure 1 is a perspective view of an automatic forklift according to one embodiment of the present invention;

[0045] Figures 2 to 4 , Figure 6 , Figure 7 and Figure 8 Schematically depicts Figure 1 of forklifts are in use;

[0046] Figure 5 yes Figure 1 A partial top view of a forklift, schematically showing a first cargo detection area; and

[0047] Fig. 9 is a flow chart of a method of transporting and placing according to one embodiment of the present invention. DETAILED DESCRIPTION

[0048] exist Figure 1 , main elements of an automatic forklift 1 according to an embodiment of the present invention are shown.

[0049] The architecture of the forklift 1 is described by way of example and does not limit the invention to the only configuration of the described architecture. It should be understood that the invention also relates to a forklift designed to operate in a manual mode, which has been adapted to implement an automatic second operating mode.

[0050] Figure 1The illustrated automatic forklift 1 comprises a lifting member 2 comprising a carriage 3 supporting a front fork 4 comprising two arms 4a, 4b spaced laterally apart and extending towards the front of the forklift. Alternatively, the front fork 4 may comprise only one arm.

[0051] The bracket 3 forms a frame. The bracket 3 is provided with a horizontal upper beam 3a and two arms 3b, 3c extending vertically downward from the upper beam 3a.

[0052] The front fork 4 also comprises two uprights 4'a, 4'b fixed to the carriage 3, each upright supporting 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 carriage.

[0053] The arms 4a, 4b of the front fork are usually intended to be inserted into insertion channels provided in a transport pallet supporting the cargo to be lifted. The uprights 4'a, 4'b are capable of lifting the arms 4a, 4b so as to be able to lift a transport pallet or some other type of cargo and to be able to put down or pick up a pallet or other type of cargo at height.

[0054] The front fork 4 can translate along the vertical mast 5 of the forklift in a vertical plane V defined by the bracket 3. The uprights 4'a, 4'b can slide along the mast 5. The arms 4a, 4b of the front fork can be Figure 1 The high-end position and the low-end position shown move between and correspond to the rolling position.In the low-end position, the arm 4a, 4b is located at a distance from the ground.

[0055] The longitudinal axes of the arms 4a, 4b are parallel. These longitudinal axes are oriented parallel to the horizontal axis X and define a horizontal plane H called the lifting plane. The arms 4a, 4b of the front fork 4 are perpendicular to the vertical plane V. The arms 4a, 4b of the front fork 4 are also preferably movable transversely relative to each other.

[0056] Alternatively, the arms 4a, 4b may also be telescopic or retractable and / or may be angularly oriented about the longitudinal axis.

[0057] As is known, the forklift 1 is equipped with a drive system 6 capable of moving the forklift 1. The drive system comprises at least one electric motor or internal combustion engine (not shown) for driving the wheels 15 of the forklift 1.

[0058] The forklift 1 is also equipped with an onboard positioning device 7 and an onboard control unit 14 ( Figure 2 ).

[0059] The control unit 14 comprises hardware and software means for controlling the operation of the drive system 6 according to the information received from the positioning device 7. The control unit 14 is also used to control the automatic movement of the lifting member 2.

[0060] The forklift 1 is also equipped with a contactless detection device 8 that can move with the lifting member 2 and a measuring device 9 for determining the height of the front fork 4 relative to the ground. The data from the detection device 8 and the measuring device 9 are transmitted to the control unit 14. The detection device 8 and the measuring device 9 are separate from the positioning device 7.

[0061] The device 9 continuously measures the relative height between the mast 5 and the carriage 3. In the embodiment shown, the measuring device 9 is fixed to the mast 5 of the forklift and faces the target 3d fixed to the carriage 3. The measuring device 9 is fixed to the mast 5 at a constant height relative to the ground. The measuring device 9 is configured to measure the relative height between the mast 5 and the carriage 3. The control unit 14 determines the height of the front fork from the measured relative height between the mast 5 and the carriage 3 by subtracting the value of a predetermined constant offset parameter (which corresponds to the relative height between the mast 5 and the carriage 3 when the front fork 4 is in the lowest position). When the front fork 4 is in the lowest position, the value of the front fork 4 thus determined is therefore equal to zero. For example, the measuring device 9 may include a rangefinder or a redundant combination of two rangefinders for determining the height of the front fork 4 relative to the ground.

[0062] Alternatively, the height of the front fork 4 relative to the ground can be determined directly at the level of the measuring device 9 by subtracting the value of said constant offset parameter from the value of the relative height measured between the mast 5 and the carriage 3 .

[0063] As mentioned above, in the embodiment shown, the measuring device 9 is fixed to the mast 5 at a constant height relative to the ground. Alternatively, the measuring device 9 may be fixed to a component of the forklift other than the mast 5 at a constant height relative to the ground. Alternatively, the measuring device 9 may also be movable together with the lifting member 2, for example by being fixed to the bracket 3 of the lifting member, in particular to one of the arms of the bracket 3.

[0064] The detection device 8 is fixed to the carriage 3, without possibility of movement relative to said carriage. Here, the detection device 8 is fixed to the upper crossbeam 3a of the carriage.

[0065] As described in more detail below, the non-contact detection device 8 is capable of emitting a light beam 10 ( Figure 2 ), the light beam 10 points to the front of the forklift 1, passes through the transported goods 12 and scans the plane detection area 11 to detect whether there is an obstacle.

[0066] The detection device 8 is fixed to the bracket 3 of the lifting member so that the light beam 10 passes over any type of cargo that can be transported by the forklift in the forklift application under consideration.

[0067] In the example shown, the light beam 10 emitted by the detection device 8 is tilted downwards. Thus, the light beam 10 emitted by the detection device 8 forms an inclination angle i with the horizontal axis, as seen from the side of the forklift.

[0068] In operation, the detection device 8 is configured to detect whether an obstacle is located within the detection area 11. When an obstacle intersects the light beam 10 and is located within the detection area 11, the obstacle is detected by the device 8. The detection device 8 can detect whether an obstacle is located within the detection area 11 by measuring distance and angle.

[0069] If the light beam 10 emitted by the device 8 is not intercepted by an obstacle, or if there is such an interception but the detection device 8 detects a distance between it and the obstacle outside the predefined planar detection area 11, the device 8 detects that there is no obstacle in said detection area.

[0070] The forklift 1 is also equipped with a device 13 for determining the linear movement of the forklift relative to the ground ( Figure 2 ), the determining device 13 is able to obtain information representing the linear movement of the forklift on the ground. The determining device is different from the positioning device 7.

[0071] The determination device 13 comprises means 13 a for measuring the movement of the forklift 1 , said measuring means 13 a being configured to acquire information representative of the movement of the forklift 1 and transmit it to the control unit 14 .

[0072] The measuring device 13a preferably comprises at least one rotary encoder capable of measuring the rotation of at least one of the wheels 15 of the forklift 1. The encoder is capable of determining a movement value of the forklift 1 from the number of rotations of the relevant wheel 15 detected.

[0073] The determination device 13 also comprises a steering sensor oriented perpendicularly to the forklift's wheel 15 and coupled to the forklift's chassis, and a magnetized target fixed to the steering rod of the forklift's wheel 15. The sensor is capable of detecting the position of the magnetized target as a function of the steering angle of that wheel 15 corresponding to the steering angle of the forklift's movement.

[0074] The linear movement of the forklift 1 is controlled based on information from the measuring device 13a and the steering sensor acquired at a predetermined frequency. For example, the acquisition frequency of information for controlling the linear movement of the forklift 1 may be 10 milliseconds. The purely linear or substantially linear movement of the forklift 1 is controlled according to the following equation:

[0075] |∑(angle×distance)|≤K(1)

[0076] in,

[0077] Angle represents the steering angle of the forklift's movement relative to its longitudinal axis as measured by the steering sensor at a given time, expressed in degrees;

[0078] Distance represents the distance travelled by the forklift truck measured by the measuring device 13a between two acquisitions, expressed in millimeters;

[0079] || is the absolute value of the calculated sum; and

[0080] K represents a predetermined limit value corresponding to the maximum permissible lateral movement of the forklift.

[0081] As described above, the control unit 14 receives information from the positioning device 7, information indicating the height of the forks from the measuring device 9 and information indicating whether there is an obstacle in the relevant detection area from the detection device 8. The control unit 14 also receives information from the determination device 13 indicating linear movement.

[0082] The control unit 14 controls the operation of the drive system 6 and the vertical movement of the front fork 4 based on this information.

[0083] In the described embodiment, the determination means 13 comprises a steering sensor and a magnetized target (which may be, for example, a magnetostrictive ruler). In an alternative embodiment, the determination means 13 may comprise an all-or-nothing sensor oriented perpendicularly to the wheels 15 of the forklift and coupled to the chassis of the forklift 1. In this case, the determination means 13 also comprises an indicator placed on the steering rod of the wheel 15. The all-or-nothing sensor is capable of detecting the indicator, which corresponds to the orientation of the wheel 15 relative to the longitudinal axis of the forklift 1. The indicator may comprise, for example, an RFID type tag.

[0084] Now refer to Figures 3 to 8 Describes the operating principle of an automated forklift 1 for safely placing cargo 12 on a rack-type structure 16 intended to receive cargo 12 transported by the forklift and Fig. 9 The relevant placement method shown in 20.

[0085] The method 20 starts with a positioning step 21 during which the control unit 14 controls the forklift 1 to position it in a predefined access position relative to the shelf 16. In a particular embodiment, the position of the forklift 1 in the access position can be stored by the control unit 14.

[0086] exist Figure 3In this initial stage shown, the control unit 14 controls the operation of the forklift 1 so that it moves toward the shelf 16. The forklift 1 is controlled by the control unit 14 based on the data from the positioning device 7. When it moves, the forklift 1 is controlled to maintain a minimum safety distance d from the shelf 16. In the initial stage of forklift positioning and the subsequent stage of height-direction positioning of the arm of the front fork 4, the forklift 1 is controlled to maintain this minimum horizontal safety distance d between the overhanging end of the arm of the front fork 4 and the shelf 16, thereby achieving safe height-direction positioning of the arm.

[0087] When the forklift 1 reaches the access position, the method 20 continues with a step 22 of heightwise positioning of the front forks 4, during which the control unit 14 controls the vertical movement of the arms 4a, 4b between a first height Z1 and a second height Z2 relative to the ground.

[0088] Based on the data from the measuring device 9, the control unit 14 controls the vertical positioning of the arms 4a, 4b until a first height Z1 ( Figure 4 ). The value of the height Z1 is predetermined. For example, the value of the height Z1 may depend on data such as the size of the shelf 16 and the goods 12 to be placed, the positioning of the detection device 8 relative to the arms 4a, 4b, and the inclination i of the light beam 10 that the detection device 8 can emit.

[0089] When the arm of the fork 4 has reached the height Z1, the method proceeds to step 23 of obstacle detection. This step 23 includes an activation sub-step 23a and a deactivation sub-step 23b. In the activation sub-step 23a, the control unit 14 controls the activation of the non-contact detection device 8. When the fork 4 has reached the height Z1, the non-contact detection device 8 emits the light beam 10. During the deactivation sub-step 23b, when the arm of the fork 4 has reached a second height Z2 ( Figure 6 ), the control unit 14 controls the deactivation of the non-contact detection device 8.

[0090] Thus, the obstacle detection step 23 is performed during the height-direction positioning step 22 of the front fork 4. During this step 22, the vertical movement of the arms 4a, 4b is continuous.

[0091] The value of height Z2 may be predetermined and may depend on the same data as used to determine the value of height Z1. When the value of height Z2 is predetermined, control unit 14 controls the vertical positioning of the arms of front fork 4 according to data from measuring device 9 until this height Z2 is reached.

[0092] Alternatively, the value of the height Z2 may be determined based on a time delay from the triggering of the first height Z1.

[0093] During the activation sub-step 23a, the light beam 10 emitted by the detection device 8 sweeps across the planar predefined detection area 11. The detection device 8 continues to be activated until the arms 4a, 4b reach the height Z2.

[0094] The width and height of the vertical projection of the detection area 11 do not exceed the width and depth of the shelf 16 .

[0095] In the embodiment shown, the detection area 11 is defined by four different points bounding a rectangle, e.g. Figure 5 Point A schematically represents the point at which the light beam 10 is emitted from the output end of the detection device 8.

[0096] The vertical projection of the rectangle defined by points B, C, D and E is located at a minimum distance w from the inner edge of shelf 16, constituting a safety margin against unnecessary detection of said edge of shelf 16. For example, distance w may be equal to 100 mm.

[0097] As described above, the detection device 8 is active during the vertical movement between the height Z1 and the height Z2 and emits the light beam 10 to detect any obstacle present in the detection area 11. As the detection device 8 realizes vertical movement between the heights Z1 and Z2, the light beam 10 sweeps the entire height interval between Z1 and Z2 and the obstacle detection is within the control volume 17 ( Figure 6 ) is realized in a control volume whose height is equal to the vertical displacement between heights Z1 and Z2 and whose cross section is equal to the detection area 11.

[0098] If an obstacle is detected in the control volume 17 during the obstacle detection step 23 , the control unit 14 stops the forklift 1 for an operator reset (step 24 ).

[0099] If, on the other hand, no obstacle is detected, the method continues with a step 25 of moving the forklift 1 forward, during which the control unit 14 controls the forklift 1 to move in a straight line from the approach position to the predetermined position 18 in order to place it on the shelf 16 ( Figure 7 The determining means 13 acquires information representing the movement of the forklift during the forward movement. As described above, the information is acquired at a predetermined frequency.

[0100] In a particular embodiment, during the step 25 of forward movement of the forklift 1, the method continues with a control step 26 during which the control unit 14 controls the linear movement of the forklift according to the data from the determination means 13 until the longitudinal arrival of the depositing position 18. At this stage, the load 12 is located vertically above the depositing position 18. For safety reasons, this ensures that any lateral deviation of the forklift 1 with respect to the linear movement remains below a predetermined permissible limit value.

[0101] If the movement of the forklift 1 is not determined by the determination device 13 to be linear or substantially linear, the control unit 14 stops the forklift 1 for an operator reset (step 27).

[0102] In the opposite case, the control unit 14 controls the straight-line movement of the forklift to longitudinally reach the predetermined placement position 18. Once the forklift reaches this position ( Figure 8 ), the method continues with a placing step 28, during which the control unit 14 controls the vertical positioning of the arms 4a, 4b relative to the shelf 16 so as to place the item 12 at the placing location 18.

[0103] During this step, the control unit 14 controls the lowering of the goods 12 above the shelf 16 until the goods 12 come into contact with a portion of the shelf 16 intended to receive the goods 12. Then, the control unit 14 continues to lower the arms 4a, 4b, causing a vertical relative movement between the arms 4a, 4b and the goods 12, indicating that the goods 12 are no longer in contact with the arms 4a, 4c and are completely placed on the shelf 16.

[0104] Alternatively, the method 20 may comprise an additional step for height-direction positioning of the front fork, performed after the sub-step 23b of deactivating the contactless detection means 8 and before the forward movement step 25. During this additional step, the height-direction positioning of the front fork may be continuous, in other words, no stoppage of the vertical movement is recorded since the step 22 of height-direction positioning of the front fork.

[0105] In another specific embodiment, in the step 25 of the forklift moving forward, the control unit 14 may limit the forward movement of the forklift to a maximum value dist( Figure 5 ), which maximum value corresponds to the component measured along the axis X of the minimum distance between the detection device 8 and the distal side CD of the detection area 11.

[0106] In the placement method shown, the height direction positioning step 22 is achieved by raising the front fork. Alternatively, the height direction positioning step 22 can be achieved by lowering the front fork. In this case, the first height Z1 is greater than the second height Z2.

Claims

1. A method (20) for transporting and placing goods (12) by means of an automatic forklift (1), the automatic forklift comprising: - a lifting member (2) comprising a front fork (4) which is vertically movable and provided with at least one arm (4a, 4b) for lifting a load (10), - a drive system (6) for moving the forklift (1), a control unit (14) capable of controlling the operation of the drive system (6) to automatically guide the forklift and capable of controlling the vertical movement of the front forks (4) of the lifting member, - a device (8) for contactlessly detecting obstacles, the detection device (8) being movable together with the lifting member (2) and being capable of emitting a light beam (10) directed towards the front of the forklift (1) and sweeping across at least one predetermined planar detection area (11), the detection device (8) being fixed to the lifting member (2) so that the light beam (10) passes over the transported goods (12), and - a measuring device (9) for determining the height of the front fork (4) of the lifting member relative to the ground, The control unit (14) receives information indicating the height of the front fork (4) relative to the ground from the measuring device (9) and information indicating whether there is an obstacle in the predetermined plane detection area (11) from the non-contact detection device (8), and is capable of controlling the vertical movement of the drive system (6) and the front fork (4) of the lifting member according to the information, The method is characterized by comprising: - a step (21) of positioning a forklift relative to a structure (16) intended to support the cargo in an approach position relative to said structure, - a step (22) of height-direction positioning of the front forks (4) of the lifting member when the forklift (1) has reached the approach position, and a step (23) of obstacle detection by means of a contactless detection device (8) in the control volume (17) swept by the light beam (10), - if during the step (23) of obstacle detection the contactless detection device (8) does not detect an obstacle in the control volume (17), a step (25) of moving the forklift (1) forward relative to the structure (16) to a placement position, and - A step of placing the cargo on the structure at a placement location (28).

2. The method according to claim 1, wherein: The obstacle detection step (23) includes: - a sub-step (23a) of activating the detection device (8) when the front fork (4) of the lifting member has reached a predetermined first height Z1 relative to the ground during the height-direction positioning of the front fork, and - Sub-step (23b) of deactivating the detection means (8) when the front fork (4) of the lifting member has reached a second height Z2 relative to the ground, different from the predetermined first height Z1.

3. A method according to claim 1 or 2, comprising the step (26) of controlling the linear movement of the forklift (1) to the depositing position during the forward movement step (25).

4. The method according to claim 3, wherein: If the controlled movement of the forklift (1) is purely linear or substantially linear, a step (28) of placing the load on the structure at the placement position is performed.

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