CN111115515A

CN111115515A - Unmanned forklift

Info

Publication number: CN111115515A
Application number: CN201911399615.5A
Authority: CN
Inventors: 李陆洋; 杨建辉; 方牧; 鲁豫杰; 郑帆
Original assignee: Shihang Robot Foshan Co ltd
Current assignee: Shihang Robot Foshan Co ltd
Priority date: 2019-12-30
Filing date: 2019-12-30
Publication date: 2020-05-08

Abstract

The invention relates to an unmanned forklift, comprising: a vehicle body; the pallet fork is used for supporting the goods; the lifting driving mechanism is used for driving the fork to move up and down; the portal frame assembly is connected with the truck body and can drive the fork to horizontally move relative to the truck body; the first detection device is arranged on the gantry assembly to form a first detection plane, and the first detection plane extends along the horizontal direction; and the controller is electrically connected with the first detection device, when the fork lifts the goods to enable the goods to touch the first detection plane, the first detection device sends a first detection signal to the controller, and the controller obtains the height of the goods according to the first detection signal sent by the first detection device. Foretell unmanned fork truck is equipped with first detection device, can obtain the width of goods, prevents that the goods superelevation and unable placing in the packing cupboard or collision packing cupboard, can improve the goods and deposit efficiency.

Description

Unmanned forklift

Technical Field

The invention relates to the technical field of unmanned forklifts, in particular to an unmanned forklift.

Background

When traditional unmanned fork truck carried the goods to the packing cupboard, only can be to the high limit for height of fork lift, the goods is depositing the in-process and striking the packing cupboard because of too high easily, influences the efficiency of depositing of goods.

Disclosure of Invention

Therefore, it is necessary to provide an unmanned forklift for solving the problem that the cargo is too high and collides with the container.

An unmanned forklift comprising:

a vehicle body;

the pallet fork is used for supporting the goods;

the lifting driving mechanism is used for driving the fork to move up and down;

the portal frame assembly is connected with the truck body and drives the fork to horizontally move relative to the truck body;

the first detection device is arranged on the portal frame assembly to form a first detection plane, the first detection plane extends along the horizontal direction, and the direction of the lifting motion of the fork relative to the vehicle body is vertical to the first detection plane; and

the controller is electrically connected with the first detection device, when the fork lifts the goods to enable the goods to touch the first detection plane, the first detection device sends a first detection signal to the controller, and the controller obtains the height of the goods according to the first detection signal sent by the first detection device.

Foretell unmanned fork truck is equipped with first detection device, drives the goods through the fork and goes up and down to make the first detection plane of goods touching, and the width that the controller obtained the goods according to the first detected signal that first detection device sent prevents that the goods from superelevation and can't place in the packing cupboard or bump the packing cupboard, can improve the goods and deposit efficiency.

In one embodiment, the first detecting device includes a first adjusting seat, a first mounting seat, and a first detector, the first detector is rotatably disposed on the first mounting seat, the first mounting seat is slidably connected to the first adjusting seat, and the first adjusting seat is fixedly disposed on the gantry assembly.

In one embodiment, the first mounting seat is provided with a mounting hole, the first adjusting seat is provided with a waist-shaped hole, the waist-shaped hole is obliquely arranged relative to a horizontal plane, a first pin shaft penetrates through the mounting hole and is partially exposed out of the mounting hole, and the pin shaft partially exposed out of the mounting hole is slidably arranged in the waist-shaped hole, so that the position of the first mounting seat is adjustable.

In one embodiment, the first adjusting seat includes two first side plates and two second side plates, the two first side plates are oppositely disposed, the first mounting seat is disposed between the two first side plates, the two second side plates are respectively disposed on the top side and the bottom side of the first mounting seat in a covering manner.

In one embodiment, the vehicle further comprises a second detection device, wherein the second detection device is respectively arranged on two opposite sides of the vehicle body so as to respectively form second detection planes which are parallel to each other on the two sides of the vehicle body, and the second detection planes extend along the vertical direction.

In one embodiment, the controller is electrically connected to the second detection device, and when the fork translates the load so that the load touches the second detection plane, the second detection device sends a second detection signal to the controller, and the controller obtains the width of the load according to the second detection signal sent by the second detection devices located on two sides of the vehicle body.

In one embodiment, the second detecting device includes a second adjusting seat, a second mounting seat, and a second detector, the second detector is rotatably disposed on the second mounting seat, the second mounting seat is slidably connected to the second adjusting seat, and the second adjusting seat is fixedly disposed on the gantry assembly.

In one embodiment, at least one of the following is also included:

the first detector can emit laser light, and the first detector forms the first detection plane through rotary scanning relative to the first mounting seat; and/or the presence of a gas in the gas,

the second detector is capable of emitting laser light, and the second detector rotationally scans relative to the second mount to form the second detection plane.

In one embodiment, the mast assembly includes a first mast coupled to the body, the forks are slidably coupled to the second mast, the second mast is coupled to the first mast, and the first sensing device is disposed on the first mast.

In one embodiment, the mast assembly further comprises a third mast, the forks being slidably coupled to the third mast, the third mast being slidably coupled to the second mast such that the second mast is positioned between the first mast and the third mast, the second mast and the third mast being capable of two-stage elevating movement.

Drawings

FIG. 1 is an isometric view of an unmanned forklift in one embodiment;

FIG. 2 is an enlarged view of a portion A of FIG. 1;

FIG. 3 is an enlarged view of part B of FIG. 1;

FIG. 4 is a diagram illustrating a first detection plane according to an embodiment;

FIG. 5 is a schematic view of the fork, the load and the first sensing plane in one embodiment;

FIG. 6 is a diagram illustrating a second detection plane according to an embodiment;

FIG. 7 is a schematic view of an embodiment of a fork, a load and a second detection plane;

FIG. 8 is an exploded view of the unmanned forklift shown in FIG. 1;

FIG. 9 is an isometric view of the combination of the mast assembly and lift drive mechanism of the unmanned aerial vehicle of FIG. 1;

fig. 10 is a top view of fig. 9.

Detailed Description

To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

It will be understood that when an element is referred to as being "secured to" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "left," "right," and the like as used herein are for illustrative purposes only and do not represent the only embodiments.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Referring to fig. 1, 5 and 8, an unmanned forklift according to an embodiment is used for forking the cargo 20, and includes a body 100, a first mast 210, a fork 300, a lift driving mechanism 400, a first detecting device 500 and a controller (not shown).

Referring to fig. 1, the mast assembly 200 is coupled to the body 100 and is capable of moving the forks 300 horizontally relative to the body 100.

Specifically, the vehicle body 100 includes a body 110 and a chassis 120, the body 110 is fixedly connected to the chassis 120 and is located above the chassis 120, and the mast assembly 200 is connected to the chassis 120.

In some embodiments, the body 110 and the chassis 120 are connected by riveting, so that the chassis 120 can be replaced after being damaged, and resource recycling is facilitated. In other embodiments, the body 110 and the chassis 120 may be integrally formed structures to enhance the structural strength and integrity.

Further, referring to fig. 8, the chassis 120 includes a connecting portion 121 and two extending portions 122, the two extending portions 122 are respectively connected to two ends of the connecting portion 121, the extending portions 122 extend along a first direction (i.e., an X direction shown in fig. 8), a sliding slot 123 is disposed inside the extending portions 122, the sliding slot 123 extends along the X direction shown in fig. 8, a roller 201 is disposed outside the first mast 210, the roller 201 slides along the sliding slot 123, that is, the mast assembly 200 can drive the fork 300 to horizontally move along the first direction relative to the body 100, so as to adjust a distance between the fork 300 and the cargo 20 when the fork 300 forks the cargo 20.

In some embodiments, the connecting portion 121 and the protruding portion 122 are integrally formed, and have high integrity and high strength. In other embodiments, the connecting portion 121 and the protruding portion 122 may also be a split structure, and the protruding portion 122 may be detachably connected to the connecting portion 121, so that the protruding portion 122 may be replaced after being damaged.

In some embodiments, the length of the extension 122 is not adjustable. In other embodiments, the extension portion 122 may also be provided with a retractable structure, so that the length of the extension portion 122 can be adjusted conveniently, so as to meet different space requirements when the unmanned forklift travels.

In some embodiments, the roller 201 is disposed outside the first gantry 210. In other embodiments, the roller 201 may also be protruded from the bottom of the first gantry 210. Alternatively, the sliding groove 123 may be provided in the first gantry 210, and the roller 201 may be provided in the protruding portion 122.

In some embodiments, two rollers 201 are respectively disposed on both sides of the first gantry 210. In other embodiments, in order to prevent the roller 201 from sliding after being damaged, a plurality of rollers 201 are respectively disposed on two sides of the first gantry 210, and the plurality of rollers 201 are disposed side by side along the first direction at intervals.

Further, referring to fig. 8, the unmanned forklift further includes wheels 130, and the wheels 130 are rotatably disposed on the chassis 120.

In some embodiments, the wheels 130 are rotatably disposed at the ends of the connecting portion 121 and the protruding portion 122, so that the unmanned forklift can keep stable and is not prone to shake when moving. In other embodiments, the wheel 130 may also protrude from the bottom surface of the protrusion 122.

Referring to fig. 9, the lift driving mechanism 400 is disposed on the mast assembly 200 for driving the fork 300 to move in a second direction (i.e., the Y direction shown in fig. 9).

Specifically, the mast assembly 200 includes the first mast 210, the lifting driving mechanism 400 includes a first lifting driving mechanism 410, the first lifting driving mechanism 410 includes a first fixing portion 411 and a first movable portion 412, the first fixing portion 411 is fixed on the first mast 210, the first movable portion 412 is connected to the fork 300 through a chain (not shown in the figure), and the first movable portion 412 can move up and down relative to the first fixing portion 411, so as to drive the fork 300 to move up and down along a second direction (i.e., the Y direction shown in fig. 9).

Referring to fig. 4, the first detecting device 500 is disposed on the mast assembly 200 to form a first detecting plane 501, the first detecting plane 501 extends along a substantially horizontal direction, and the direction of the lifting motion of the fork 300 relative to the truck body 100 is substantially perpendicular to the first detecting plane 501.

Specifically, referring to fig. 2, the first detecting device 500 includes a first detector 510, a first adjusting seat 520 and a first mounting seat 530, the first detector 510 is rotatably disposed on the first mounting seat 530, the first mounting seat 530 is slidably connected to the first adjusting seat 520, and the first adjusting seat 520 is fixedly disposed on the first gantry 210.

It should be noted that the first detector 510 can emit laser light, and the first detector 510 scans and forms the detection plane 501 with respect to the first mounting base 530.

In some embodiments, a mounting hole (not shown) is formed in the first mounting seat 530, a waist-shaped hole 540 is formed in the first adjusting seat 520, the waist-shaped hole 540 is disposed in an inclined manner with respect to a horizontal plane, a first pin (not shown) penetrates through the mounting hole and is partially exposed out of the mounting hole, and the pin partially exposed out of the mounting hole is slidably disposed in the waist-shaped hole 540, so that the position of the first mounting seat 530 is adjustable, thereby facilitating the position adjustment of the first detector 510. When the height and horizontal position of the first detector 510 are not appropriate or the first detection plane 501 is tilted, the first detector 510 can be adjusted by adjusting the position of the first mounting seat 530. In other embodiments, the first adjusting base 520 and the first mounting base 530 may also be rotatably connected by a hinge or a hinge.

In some embodiments, referring to fig. 2, the first mounting seat 530 includes a first side plate 531, a second side plate 532 and a bottom plate 533, the first side plate 531 and the second side plate 532 are both vertically connected to the bottom plate 533, the bottom plate 533 is fixedly connected to the first gantry 210, the first side plates 531 are disposed in two opposite directions, the first mounting seat 530 is disposed between the two first side plates 531, the second side plates 532 are disposed in two opposite directions, and the two second side plates 532 are respectively disposed on the top side and the bottom side of the first mounting seat 530, so as to perform the functions of dust-proof and water-proof for the first detector 510. In other embodiments, the first side plate 531, the second side plate 532 and the bottom plate 533 may be connected at other angles, or the first detector 510 may be directly connected to the bottom plate 533 in a rotatable manner.

Further, the above unmanned forklift further includes a control box 502, the controller is disposed in the control box 502 and electrically connected to the first detection device 500, when the fork 300 lifts the goods 20 so that the goods 20 touch the first detection plane 501, the first detection device 500 sends a first detection signal to the controller, and the controller obtains the height H of the goods 50 according to the first detection signal sent by the first detection device 500.

For ease of understanding, reference will now be made to FIG. 5.

The preset height H1 of the first detection device 500 is a fixed value, the fork 300 drives the goods 20 to go up and down to the time of triggering the first detection plane 501, the fork 300 stops the lifting motion, the lifting height H2 of the fork 300 can be obtained through the controller at the moment, the height H of the goods 20 is the difference between H1 and H2, the height H of the goods 20 is convenient to obtain, the operation is simple, the cost is low, and the problem that the goods 20 cannot be placed in a container due to overhigh height can be effectively avoided.

Further, the controller can set a preset size of the container and control the fork 300 to move according to the obtained height of the cargo 20, so that the fork 300 places the cargo 20 in the container with the preset size at least larger than the height of the cargo 20.

Specifically, when the height of the cargo 20 is larger than the height of the container, the controller can know the height of the cargo 20 in advance, and then can control the fork 300 to stop placing the cargo 20 in the container, for example, to send a buzzer prompt, or select a container with a preset size larger than the cargo for storage, so as to avoid the cargo 20 from colliding with the container or being unable to be placed in the container due to being too high.

Referring to fig. 1, the unmanned forklift further includes a second detecting device 600, the second detecting device 600 is respectively disposed on two opposite sides of the forklift body 100, so as to form second detecting planes 601 parallel to each other on two sides of the forklift body 100, the second detecting planes 601 extend substantially along a vertical direction, and the second detecting planes 601 are substantially perpendicular to the first detecting planes 501.

Specifically, referring to fig. 3, the second detecting device 600 includes a second detector 610, a second adjusting seat 620 and a second mounting seat 630, the second detector 610 is rotatably disposed on the second mounting seat 630, the second mounting seat 630 is slidably connected to the second adjusting seat 620, and the second adjusting seat 620 is fixedly disposed on the first gantry 210.

It should be noted that the second detector 610 is capable of emitting laser light, and the second detector 610 forms a second detection plane 601 by rotating and scanning with respect to the second mounting base 630.

Since the second adjusting base 610, the second mounting base 620 and the second detector 630 of the second detecting device 600 are assembled in a similar manner to the first adjusting base 520, the first mounting base 530 and the first detector 510 of the first detecting device 500, they will not be described in detail.

Further, the controller is electrically connected to the second detecting device 600, when the fork 300 drives the cargo 20 to move horizontally so that the cargo 20 touches the second detecting plane 601, the second detecting device 600 sends a second detecting signal to the controller, and the controller obtains the width W of the cargo 20 according to the second detecting signal sent by the second detecting device 600 located at two sides of the vehicle body 100.

For ease of understanding, the following description will be made with reference to fig. 7, in which the number of the second detection devices 600 is two and two second detection devices 600 are provided on opposite sides of the vehicle body 100.

In some embodiments, the fork 300 is located between two oppositely disposed second detecting devices 600, the fork 300 first drives the cargo 20 to move to the second detecting plane 601 on the left side of the trigger along the Z direction shown in fig. 7, then the fork 300 first drives the cargo 20 to move to the second detecting plane 601 on the right side of the trigger along the Z direction shown in fig. 7, the horizontal distance W1 between the two oppositely disposed second detecting devices 600 is a fixed value, the distance W2 that the fork 300 moves from the second detecting plane 601 on the left side of the trigger to the second detecting plane 601 on the right side of the trigger is obtained by the controller, the width W of the cargo 20 is the difference between W1 and W2, the width W of the cargo 20 is obtained conveniently, the operation is simple, the cost is low, and the problem that the cargo 20 cannot be placed on the container due to being too wide can be.

In other embodiments, the fork 300 is located outside the left second detecting device 600 or the right second detecting device 600, the fork 300 drives the cargo 20 to move along the Z direction shown in fig. 7 to sequentially trigger the left second detecting plane 601 and the right second detecting plane 601, the preset horizontal distance W1 between the two oppositely disposed second detecting devices 600 is a fixed value, the distance from the triggered left second detecting plane 601 to the triggered right second detecting plane 601 of the fork 300 is W2, and the width W of the cargo 20 is the difference between W1 and W2.

Further, the controller can set a preset size of the container and control the fork 300 to move according to the obtained width of the cargo 20, so that the fork 300 places the cargo 20 in the container with the preset size at least larger than the width of the cargo 20.

Specifically, when the width of the cargo 20 is larger than the width of the container, the controller can know the width of the cargo 20 in advance, and then can control the fork 300 to stop placing the cargo 20 in the container, for example, to send a buzzer prompt, or select a container with a preset size larger than the cargo for storage, so as to avoid the cargo 20 from colliding with the container or being unable to be placed in the container due to the super-width.

Further, in order to make the adjustment range of the lifting height of the fork 300 wider and more precise, referring to fig. 9, the mast assembly 200 further includes a second mast 220 and a third mast 230, the second mast 220 and the third mast 230 can perform two-stage lifting motion, the above-mentioned unmanned forklift further includes a second lifting driving mechanism 420, the fork 300 is slidably connected to the third mast 230, the second mast 220 is slidably connected between the third mast 230 and the first mast 210, the first lifting driving mechanism 410 can drive the fork 300 to perform lifting motion along a second direction (along the Y direction shown in fig. 9), and the second lifting driving mechanism 420 can drive the second mast 220 and the third mast 230 to perform lifting motion along the second direction, so as to drive the fork 300 to perform lifting motion along the second direction.

Specifically, the second lifting driving mechanism 420 includes a second fixed portion 421 and a second movable portion 422, the second fixed portion 421 is fixed on the first door frame 210, and the second movable portion 422 is connected to the second door frame 220 to drive the second door frame 220 and the third door frame 230 to perform a lifting motion along a second direction (i.e., the Y direction shown in fig. 9).

In some embodiments, referring to fig. 8, the fork 300 is slidably connected to the third mast 230 through a first pulley 310, referring to fig. 10, the first mast 210 is slidably connected to the second mast 220 through a second pulley 221, the second mast 220 is slidably connected to the third mast 230 through a third pulley 231, and the control unit is connected to the first pulley 310, the second pulley 221, and the third pulley 231 to control the lifting speed. The second gantry 220 and the third gantry 230 can perform two-stage lifting movement, for example, the control unit can control the rotation speeds of the second pulley 221 and the third pulley 231, and when the rotation speeds of the second pulley 221 and the third pulley 231 are the same, the second gantry 220 and the third gantry 230 can be synchronously lifted along the second direction and lifted at the same lifting speed; when the rotation speeds of the second pulley 221 and the third pulley 231 are different, the second gantry 220 and the third gantry 230 are lifted synchronously along the second direction and the lifting speeds are different.

In other embodiments, the forks 300 and the third mast 230, the first mast 210 and the second mast 220, and the second mast 220 and the third mast 230 may be slidably coupled by a slide rail and slider fit.

In some embodiments, the first lift drive mechanism 410 and the second lift drive mechanism 420 are both hydraulic rams. In other embodiments, the first lifting driving mechanism 410 and the second lifting driving mechanism 420 may also be motors or air cylinders or lead screw assemblies.

Referring to fig. 8, the unmanned forklift further includes a side transfer frame 700 and a fork carriage 800, the side transfer frame 700 is slidably connected to the first mast 210, the fork carriage 800 is slidably connected to the side transfer frame 700, and the forks 300 are fixed to the fork carriage 800 such that the forks 300 can move horizontally in a third direction (i.e., the Z direction shown in fig. 8) relative to the side transfer frame 700.

In some embodiments, the side shifting frame 700 has a hollow shaft 710, the fork carriage 800 has a hydraulic cylinder 810 disposed on the shaft 710, and the hydraulic cylinder 810 extends through the shaft 710 to allow the forks 300 to laterally shift in a third direction (i.e., the Z direction in fig. 8) relative to the side shifting frame 700 to facilitate forking of the cargo 20.

In some embodiments, the number of forks 300 is two and the forks 300 are spaced apart, and the spacing between the forks 300 is not adjustable. In other embodiments, the cylinder can be arranged between the two forks 300, the two forks 300 are driven by the cylinder to be close to or far away from each other, so that the distance between the two forks 300 is changed, the forks 300 can conveniently fork the cargos 20 with different sizes, and the application range of the unmanned forklift is expanded.

In some embodiments, the ends of the forks 300 are tapered to facilitate the forking of the cargo 20. In other embodiments, the ends of the forks 300 may also be W-shaped. In some embodiments, the length of the forks 300 is not adjustable. In other embodiments, the fork 300 may be provided with a retractable structure to meet the requirements of different sizes of the cargo 20.

The unmanned forklift is provided with the first detection device 500 and the second detection device 600, the goods 20 are driven to move to the triggering first detection plane 501 and/or the second detection plane 601 through the fork 300, so that the height H and/or the width W of the goods 20 are calculated, the goods 20 are prevented from being too high or too wide and cannot be placed in a container or collide with the container, the storage efficiency of the goods 20 is improved, the operation is simple and convenient, the cost is low, and the structural design is reasonable.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. An unmanned forklift, comprising:

a vehicle body;

the pallet fork is used for supporting the goods;

the lifting driving mechanism is used for driving the fork to move up and down;

2. The unmanned forklift of claim 1, wherein the first detecting device comprises a first adjusting seat, a first mounting seat and a first detector, the first detector is rotatably disposed on the first mounting seat, the first mounting seat is slidably connected to the first adjusting seat, and the first adjusting seat is fixedly disposed on the mast assembly.

3. The unmanned forklift as claimed in claim 2, wherein the first mounting seat is provided with a mounting hole, the first adjusting seat is provided with a waist-shaped hole, the waist-shaped hole is arranged obliquely relative to the horizontal plane, a first pin shaft penetrates through the mounting hole and is partially exposed out of the mounting hole, and the pin shaft partially exposed out of the mounting hole is slidably arranged in the waist-shaped hole, so that the position of the first mounting seat is adjustable.

4. The unmanned forklift of claim 2, wherein the first adjusting seat comprises two first side plates and two second side plates, the two first side plates are oppositely arranged, the first mounting seat is arranged between the two first side plates, the two second side plates are respectively arranged on the top side and the bottom side of the first mounting seat in a covering manner.

5. The unmanned forklift as claimed in claim 2, further comprising second detection means provided on opposite sides of the vehicle body, respectively, to form second detection planes parallel to each other on the opposite sides of the vehicle body, respectively, the second detection planes extending substantially in a vertical direction, the second detection planes being substantially perpendicular to the first detection planes.

6. The unmanned forklift as claimed in claim 5, wherein the controller is electrically connected to the second detecting device, and when the fork translates the load so that the load touches the second detecting plane, the second detecting device sends a second detecting signal to the controller, and the controller obtains the width of the load according to the second detecting signal sent by the second detecting device located on both sides of the forklift body.

7. The unmanned lift truck of claim 5, wherein said second sensing device comprises a second adjustment base, a second mounting base, and a second sensor, said second sensor being rotatably mounted to said second mounting base, said second mounting base being slidably coupled to said second adjustment base, said second adjustment base being fixedly mounted to said mast assembly.

8. The unmanned forklift of claim 7, further comprising at least one of:

9. The unmanned lift truck of claim 1, wherein said mast assembly includes a first mast and a second mast, said first mast coupled to said body, said forks slidably coupled to said second mast, said second mast coupled to said first mast, said first sensing device disposed on said first mast.

10. The unmanned lift truck of claim 9, wherein said mast assembly further comprises a third mast, said forks being slidably coupled to said third mast, said third mast being slidably coupled to said second mast such that said second mast is positioned between said first mast and said third mast, said second mast and said third mast being capable of two-stage lifting movement.