JPH0592898A - Device and method for controlling and position- ing fork of vehicle for handling material - Google Patents

Abstract

PURPOSE: To provide a device and a method for automatically positioning a fork at an opening of cargo. CONSTITUTION: This device controls and moves forks 30 and 32 of a material handling vehicle 2 in a lateral direction of a carriage assembly 12. The carriage assembly 12 includes fork position sensors 81 and 83 to detect the lateral position of the respective forks 30 and 32. When a controller receives a signal from the position sensors 81 and 83, it moves the forks 30 and 32 to a specified position or a computed position. Fork chip sensors 102 and 104 detect an opening 188 of a moving cargo 186. The controller 178 receives a signal from the fork chip sensors 102 and 104, and it positions the forks 30 and 32 as to place them in the opening 188. The device is particularly suitable for its application on an automatic guide vehicle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to an apparatus and method for moving the first and second forks of a material handling vehicle in a controlled manner, and more particularly to each fork relative to a load opening. Regarding positioning.

[0002]

BACKGROUND ART In the field of material handling, flexibility is a major factor. Material handling vehicles receive, carry, and unload loads for a variety of purposes. Loads are typically packaged in shipping tubs, pallets, containers and the like. Vehicles typically include a pair of forks located at the load opening.

The width of the load opening varies considerably depending on the type, size and application of the load. The distance between the forks is limited by the minimum width of the load opening for any load. Therefore, a vehicle that can change the distance between the forks is desirable. For example, forklift trucks typically have forks carried by a carrier. That is, the fork is coupled to the lift mast assembly for manual positioning depending on the width of the load opening. Ch on June 10, 1984 and March 5, 1985, respectively.
arles J. P. U.S. Pat. Nos. 4,458,786 and 4,502,568 issued to Lebre disclose forklift trucks having handles for varying fork spacing. However, this is done manually and additionally the forks must be moved simultaneously and in the same direction.

Forklift trucks with fork spreaders are also known. This device allows the operator to hydraulically or electrically control the fork. 1
D.M. A. U.S. Pat. No. 2,886,197 issued to Harris discloses a lift truck with a load clamp, which truck is a hydraulic valve for moving an arm of the clamp to open and close the clamp. Includes hydraulic cylinders. However, there is no means on this track to determine the exact position of the clamp's arm except at the operator's discretion. Therefore, it is difficult to position the forks at the correct spacing.

Driverless type automated guided vehicle (AG
Some V) also include a lift mast assembly and fork. Greater flexibility is required in these vehicles. Since AGVs are used to transport different loads, they must be able to accommodate different loads and load openings. A problem arises by limiting the width of the forks to accommodate the smallest load opening. It becomes very unstable when handling wider loads, usually heavier loads. It is extremely undesirable to add manual operation to such an operator-less vehicle, so it automatically detects the position of each fork at any point during operation and automatically The need for positioning systems is becoming increasingly important.

The present invention is directed to overcoming one or more of the problems set forth above.

[0007]

DISCLOSURE OF THE INVENTION According to one aspect of the present invention, a material handling vehicle has a frame and a lift / mast assembly, the lift / mast assembly being coupled to the frame and having a pair of spaced-apart vertical solids. And a carriage assembly having a first guide portion laterally oriented with respect to these uprights, which is connected to the uprights and is movable along the same, and this carriage assembly. A material handling vehicle is provided that has first and second forks that are connected to a solid body and that can move laterally relative to the upright solid body relative to the carriage assembly. A sensor detects the positions of the forks and outputs a signal representative of those positions. A controller calculates the fork position with respect to the carriage assembly.

In accordance with another aspect of the invention, the first and second forks of the material handling vehicle are controlled to align with a load having a load opening having first and second spaced vertical edges. While moving the first and second forks at predetermined first and second initial positions,
Moving the first and second forks to their respective lateral positions, detecting the first vertical edge of the load opening,
Detecting the second vertical edge of the load opening, and detecting the position of the first fork in response to detecting the first vertical edge;
Detecting the position of the second fork in response to detecting the second vertical edge, stopping the movement of the first fork at a predetermined position with respect to the first vertical edge, and having a predetermined position with respect to the second vertical edge. Stopping the movement of the second fork and positioning the second fork at a distance from the first fork.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Referring to FIG. 1, a preferred material handling vehicle 2 is an automatic guided vehicle 4 (AG).
(Known in the art as V). The AGV 4 has a frame 6 and a lift / mast assembly 8
The lift mast assembly includes a pair of spaced uprights 10 coupled to the frame 6 and a carriage assembly 12 adapted to engage a load 186. The carriage assembly 12 moves along the upright body 10. Lift and mast assembly 8 is located along the deck 13
It moves in the longitudinal direction relative to GV4. As shown in phantom, the lift and mast assembly 8 includes the carriage assembly 1
2 and load 186 are placed on deck 13 during transport with an even load distribution about the longitudinal axis of AGV 4.

Referring to FIG. 2, the carriage assembly 12 includes a carriage 18 and a displaceable side frame 20 connected to the carriage 18 and having a support bracket 19. The carriage 18 is the first guide portion 1
4 and a carriage frame 21. The first guide portion 14, although shown as a guide rod as the preferred form, is slidably disposed within a hole provided in the support bracket 19. The displaceable side frame 20 is movable relative to the carriage 18 in a direction that substantially traverses the upright 10. First and second forks 30, 32 are connected to the displaceable side frame 20 and are movable in a direction along the second guide portion 16 on the displaceable side frame 20. As best seen in FIG. 3, the first and second forks 30, 32 include a shank 42 and a load engaging portion 44. The forks 30, 32 are of the "hook" type and are suspended from the side frame 20 which is displaceable in the usual way.

The load 186 is at least one constituted by first and second vertical edges 190,192 spaced apart and first and second lateral edges 194,196 spaced apart.
It has one load opening 188.

Vertical Carriage Assembly Drive System 7
0 moves the carriage assembly 12 vertically along the upright 10 in a controlled manner. The vertical carriage assembly drive system 70 includes a chain and pulley assembly (not shown) and a hydraulic lift cylinder 72. The chain / train assembly is operatively connected to the carriage assembly 12, upright 10 and hydraulic lift cylinder 72. The vertical carriage assembly drive system 70 moves the carriage assembly 14 along the upright 10 in the conventional manner. This vertical carriage assembly drive system 70 is known in the art. Therefore, no further description will be given.

Referring to FIGS. 2 and 3, there are first and second positions for detecting the positions of the first and second forks 30, 32.
The second sensing means 80, 82 are shown. These first,
The second sensing means 80, 82 are the bar code system 12
2 is preferable. First and second elongated placard 1
28 and 130 are mounted to the displaceable side frame 20 using brackets 132 in the conventional manner. A dark vertical mark 124 is printed on the surface 126 of these placards 128, 130. Alternatively, the placards 128, 130 may be grouped together into a single elongated member 12
You can set it to 0. The surface 126 has the first and second forks 3
Facing 0, 32 shank 42.

The first and second position sensors 81 and 83 send out electromagnetic radiation toward the first and second placards 128 and 130. Electromagnetic radiation is absorbed by the dark surface and reflected by the light surface. Position sensor 81, 1 of 83
The electromagnetic radiation sent from the two placards 128, 13
When directed towards the space between the marks 124 on the zero, the electromagnetic radiation reflects back towards the same position sensor 80, 82. The position sensors 81 and 83 detect the reflected electromagnetic radiation and output first and second electric signals in response thereto. The position sensors 81, 83 output one of two voltage levels when detecting electromagnetic radiation and output the other voltage level when not detecting electromagnetic radiation, whereby the placards 128, 13 are output.
"Read" mark 124 on 0. Controller 18
0 detects this change in the output state of the position sensors 81 and 83.

Alternatively, the marks 124 on the placards 128, 130 may be permanent magnets and the position sensors 80, 82 may be Hall effect sensors (not shown). The Hall effect sensor reads the mark 124 and changes the output state as the magnet moves in close proximity.

Alternatively, the first and second detecting means 80, 8
2 may include a resolver system 160 as shown in FIG. The ladder assembly 162 is mounted on the displaceable side frame 20 in any suitable manner (eg, screw fasteners not shown). For simplicity,
Only one of the first and second sensing means 80, 82 is shown. First and second toothed elements 166, 168 are rotatably mounted on the forks 30, 32. The toothed elements 166, 168 engage the ladder assembly 162 and rotate in response to movement of the forks 30, 32. The rotational movement of the toothed elements 166, 168 is transmitted to the resolvers 174, 176 via the shaft 164. Resolver 17
4, 176 are well known in the art, and are excited by a constant frequency signal and output a pair of constant frequency signals having a magnitude and phase relationship proportional to the angular position of the resolvers 174, 176. Gearbox 170 may be connected between shaft 164 and resolvers 174, 176 if deceleration is desired. Resolvers 174 and 176 are resolvers
It is electrically connected to the digital (R / D) converter 172. The R / D converter 172 includes resolvers 174, 17
6 to receive a frequency signal and generate a multi-bit digital signal related to the amount of rotation of shaft 164. This digital signal is a signal indicating the momentum of the forks 30 and 32, and is input to the controller 180.

A third sensing means 90 senses the position of the displaceable side frame 20 relative to the carriage 18 and, in response to the displaceable side frame 20 being in a predetermined lateral position, produces a third electrical response. Output a signal. Preferably, this third sensing means 90 comprises a lateral position sensor 91 with a Hall effect sensor 92 and a permanent magnet 94. The Hall effect sensor 92 is the carriage frame 21.
The permanent magnet 94 is mounted on the displaceable side frame 20. The Hall effect sensor 92 changes the output state when the permanent magnet 94 approaches. Sensor 92 when permanent magnet 94 is moving by
The output state change of appears as a pulse. Preferably, the permanent magnet 94 is the centerline 22 of the displaceable side frame 20.
Hall effect sensor 92 mounted on top of the permanent magnet 9
The side frame 2 that is laterally aligned with 4 and is displaceable
When 0 is centered with respect to the carriage 18, it outputs a third electric signal in response to that.

The fourth sensing means 100 senses the first and second vertical edges 190, 192 of the load opening 188 and, in response thereto, outputs fourth and fifth electrical signals. Preferably, the fourth sensing means 100 includes first and second fork tip sensors 102,104. These fork tip sensors 102, 104 emit electromagnetic radiation in the direction away from the vehicle 2 toward the load 186 and the load opening 188, and detect the reflection of this electromagnetic radiation. Electromagnetic radiation reflects in the presence of suitable obstacles, such as load 186. First and second fork tip sensors 102, 10
Reference numeral 4 sends fourth and fifth signals to the controller 180 in response to a change in the state when the reflected electromagnetic radiation is detected or not.

The fifth and sixth detection means 200 and 202 detect the positions of the first and second forks 30 and 32 with respect to the predetermined first and second initial positions, respectively. Preferably,
The first and second initial positions are close to each other and are centered on the carriage assembly 12. Preferably, the detection means 2
00 and 202 are first and second initial sensors 204 and 206.
Includes. The first and second initial sensors 204, 206 are attached to the carriage 18 and emit electromagnetic radiation toward the first and second forks 30, 32, respectively. Preferably, the first and second initial sensors 204, 20
6 is connected to the carriage assembly 12 above the respective forks 30, 32. A first retroreflective strip 208 is connected to the first fork 30 and a second retroreflective strip 210 is connected to the second fork 32. These retroreflective strips 208, 210 are
The second forks 30, 32 are oriented so as to reflect electromagnetic radiation in response thereto when in the first and second initial positions, respectively. First and second initial sensor 2
04 and 206 emit first and second initial signals in response to the reflected electromagnetic radiation, respectively.

The carriage assembly 12 includes a second guide portion 1
First and second forks 30, 3 in the direction along 6
It includes first and second driving means 50 and 52 for moving the two while individually controlling them. Preferably, these drive means 50, 52 are first and second electric actuators 54, 5
It includes first and second driving guides 51 and 53 having a number 6. The electric actuators 54, 56 are operated in a conventional manner via a motor control system (not shown). The first drive system 51 responds to the sixth and seventh electrical signals from the controller 180 by moving the first fork 30 to the first fork 30 along the second guide portion 16.
Laterally and in a second lateral direction along the second guide portion 16. The second drive system 53 moves the second fork 32 in the first lateral direction and the second lateral direction in response to receiving the eighth and ninth electric signals from the controller 180. Alternatively, for example, a hydraulic cylinder may be used to move the forks 30, 32 while controlling them. The sixth, seventh, eighth, and ninth signals actuate solenoid actuated hydraulic control valves for controlling movement of the forks 30,32.

Third driving means 6 for moving the side frame 20 displaceable along the first guide portion 14 while controlling it.
0 is also set. Preferably, the third drive means 60 includes a lateral carriage assembly drive system 61 and includes a hydraulic system (not shown) including a hydraulic cylinder 62 mounted between the carriage 18 and the displaceable side frame 20. )
Has become a part of.

Referring to FIG. 5, the control system 178 includes a controller 180 under software control, which controller includes first and second fork position sensors 81, 83, first and second fork tips.・ Sensor 1
02, 104, the signal from the lateral position sensor 91 and the signal from the vertical position sensor 110 for detecting the position of the carriage 18 with respect to the upright body 10. Vertical position sensor 110 preferably includes a resolver system as described above.

The control means 180 controls the vertical movement of the carriage assembly 12 and the lateral movement of the displaceable side frame 20 in the vertical carriage assembly drive system 7.
0, lateral carriage assembly drive system 61, load engagement drive system 140 and vehicle drive system 150. Since there are many drive systems suitable for the intended purpose, the drive system 7
A detailed description of 0, 61, 140, 150 will not be given here. The control means 180 includes a controller 178,
The movements of the first and second forks 30 and 32 are independently controlled via the first and second fork drive systems 50 and 52.

Controller 180 typically includes a microprocessor, static memory and dynamic memory.
These are well known in the vehicle control arts and will not be described in detail here.

The controller 180 is the carriage assembly 1
A vertical height of 2, a signal indicating the lateral position of the displaceable side frame 20 and a signal indicating the presence or absence of a load 186 are received. Using these signals, the controller 180 operates to position the forks 30, 32 and the displaceable side frame 20 in a suitable position to engage the load 186 by searching the load opening 188. Once the positioning is done, the controller 180
Moves the forks 30, 32 into the load opening 188. The controller 180 can control the various parts that engage the load 186 of the AGV 4. For example, the AGV 4 has a lift mast assembly 8 and a carriage assembly 12 mounted thereon by the load engagement drive system 140.
Can remain stationary while moving relative to the longitudinal axis of the. Alternatively, the vehicle drive system 150 is AGV4
May be moved toward load 186 and forks 30, 32 may be moved into load opening 188 to engage load 186.

Referring to FIG. 6, there are sensors 81,
The electrical connections between 83, 102, 104, 91 and controller 180 are shown. As can be seen here, the sensors 81, 83, 102, 104, 91 and the controller 18
The electrical connections of 0 are the same. Therefore, only the electrical connection between the first fork position sensor 81 and the controller 180 will be described below. However, this description applies equally to the remaining sensors 83, 102, 104, 91.
Therefore, similar components are provided with similar reference numerals. The output portion of the first position sensor 81 is 95
Connect to the cathode of. The anode of diode 95 is connected to pull-up resistor 96 and low pass filter 97. The low pass filter 97 includes a series resistor 98 and a capacitor 99. The series resistor 98 has one end connected to the anode of the diode 95 and the opposite end connected to the capacitor 99. The capacitor 99 is also connected to circuit ground. The low-pass filter 97 is connected to the controller 18 via the amplifier 93.
Connected to 0. The sensor 81 emits a pulse when it passes a mark 124 on the surface 126 of the placard 128. Low pass filter 97 removes high frequency noise from the pulse and amplifier 93 provides controller 180 with the amplified pulse. The controller 180 detects the pulse and determines the position of the first fork 30 as a function of this pulse. The illustrated fork position sensors 81, 83 and fork tip sensors 102, 104 have open collector outputs and are commercially available. The lateral position sensor 91 includes the Hall effect sensor 92 and the permanent magnet 94, as described above. Hall effect sensor 92
A pulse is generated when the permanent magnet 94 passes through it. The controller 180 receives the filtered and amplified pulse as described above. The position of the displaceable side frame 20 is determined as a function of this pulse and lateral velocity of travel.

Referring to FIG. 7, there is shown a portion of one embodiment of control software. Controller 18
0 is programmed with the route to the next load 186 on the AGV 4 and the type of load 186 that is going to be transported. As shown in the control block 200, the forks 30 and 32 are positioned at an initial position in the lateral center of the displaceable side frame 20 and the displaceable side frame 20.
Is positioned in a laterally central position on the carriage assembly 12. In the control block 202, the controller 180
Moves AGV 4 to a position substantially in front of load 186. The controller 180 has a control block 2
As shown at 04 and 206, the forks 30 and 32 are moved in the first and second lateral directions. Fork position sensor 8
1, 83 in response to detecting the marks 124 on the placards 128, 130 as the forks 30, 32 are moved along the second guide portion 16, the controller 1
Send a pulse to 80. Controller 180 uses each mark 1
The spacing of 24 and the width of each mark 124 is programmed.
The controller 180 receives the pulses from the position sensors 80, 82 and calculates the position of the forks 30, 32 with respect to the displaceable side frame 20.

A corresponding distance between the first and second vertical edges 190, 192 that matches the type of load 186 is programmed into the controller 180. A desired distance “D” between the first and second forks 30, 32 is determined based on the distance between the first and second vertical edges 190, 192. For this desired distance “D”, the forks 30 and 32 are at the load opening 18
It is a distance suitable for entering the load 8 and lifting the load 186.
The positions of the first and second 30, 32 are the forks 30, 32.
Is repeatedly calculated as M moves along the second guide portion 16. A desired distance “D” with respect to the center line 22 of the side frame 20 in which the position of the first fork 30 can be displaced.
The movement is stopped when it reaches a value approximately equal to half (control block 208). The side frame 2 in which the position of the second fork 32 can be displaced in the opposite lateral direction.
When a value equal to approximately half the desired distance "D" is reached with respect to the 0 centerline 22, the movement is stopped (control block 210).

Thereafter, the displaceable side frame 20 is positioned in front of the load opening 188 and the forks 30, 3 are
2 can be located in the load opening 188 as follows. First, a vertical search is initiated at control block 212. Displaceable side frame 20 and first,
Carriage assembly 12 including second forks 30, 32
Are moved in the first vertical direction. First lateral edge 194
Is detected by the fork tip sensors 102, 104, the carriage assembly 12 is stopped. The control system 178 then determines the height of the first lateral edge 194 by sensing the position of the carriage assembly 12 with respect to the upright 10. The carriage assembly 12 is then moved in a second lateral direction and the carriage assembly 12 is stopped when the second lateral edge 196 is detected by the fork tip sensors 102, 104. The control system 178 then determines the height of the second lateral edge 196 by sensing the position of the carriage assembly 12 with respect to the upright 10. First and second lateral edges 19
The heights of 4, 196 are averaged and the height of the load opening 188 approximately at the center is found. In control block 214, the carriage assembly 12 is vertically positioned such that the forks 30, 32 are vertically centered on the load opening 188. A similar search is made in control block 216 to find the lateral center of load opening 188. This is accomplished by moving the displaceable side frame 20 in first and second lateral directions and sensing the first and second vertical edges 190,192. The lateral center of the load opening 188 may then be calculated. The displaceable side frame 20 is then moved along the first guide portion 14 in the control block 218, causing the forks 30, 32 to move into the load opening 188.
Come to the desired position for. Finally, the controller 180
However, the load engagement drive means 140 or the vehicle drive system 15
0 or both of them to use the carriage assembly 12
To engage the load 186.

In another embodiment, the controller 180
Stores the route that the AGV4 should take in its memory. However, the controller 180 is not programmed for the type of load 188. Therefore, the fork 30,
The desired distance "D" of 32 cannot be determined as described above. Referring to FIG. 8, another embodiment of control software is shown here. In control block 240, the first and second forks 30, 32 are moved to the initial position. These initial positions are preferably close to the centerline 22 of the side frame 20 which is displaceable as far as the range of movement allows. At control block 242, AGV 4 is moved to a position generally forward of load 188. The first and second forks 30, 32 are simultaneously moved in the first and second lateral directions (control blocks 244, 246, respectively). First fork tip sensor 102
If the first vertical edge 190 of the load opening 188 is detected by the control block 248, the movement of the first fork 30 is stopped. Second fork tip sensor 10
When the 4 detects the second vertical edge 192 of the load opening 188, the movement of the second fork 30 is stopped in the control block 250. In the control block 252, the controller 180 calculates the desired distance “D” between the first and second forks 30, 32 based on the positions of the first and second forks 30, 32. This desired distance “D” is a predetermined distance “X” between the first fork 30 and the first vertical edge 190 and a predetermined distance “Y” between the second fork 32 and the second vertical edge 192. Giving, as a result, the edges 190, 1
A gap is provided between 92 and the forks 30, 32. Next (control block 254), the forks 30, 32 are moved to a center position on the displaceable side frame 20 while maintaining the desired distance "D". The distance traveled by each fork 30, 32 is stored in the controller 180. The displaceable side frame 20 is moved using the stored distance and the calculated desired distance “D”, and the displaceable side frame 20 is moved.
And the forks 30, 32 are positioned relative to the load opening 188. Finally, the controller 180 moves the carriage assembly 12 into engagement with the load 186 using the load engaging drive means and / or the vehicle drive system 150.

[0031]

INDUSTRIAL APPLICABILITY With reference to the drawings, in operation, the AGV 4 is guided via an on-board guidance system (not shown) towards the destination point where it is about to pick up the load 186. The load 186 is a tab, a pallet, a container, or the like. During movement, the lift and mast assembly 8 is positioned on the deck 13 as shown in phantom in FIG. AGV 4 is driven by vehicle drive system 150 to a position generally forward of load 186.

The load engagement drive system 140 moves the lift and mast assembly 8 on the deck 13 along the AGV 4 to the position indicated by the solid line. The vertical carriage assembly system 70 moves the carriage assembly 12 along the upright 10 to an evaluation position where the forks 30, 32 are in front of the load opening 188.

The controller 180 is programmed with the type and size of the load 186 to be transported. Load 1
The 86 type has a corresponding load opening 188 constituted by first and second vertical edges 190, 192 and first and second lateral edges 194, 196. The vertical edges 190, 192 are set to a constant distance that gives the load opening 188 a set width. The controller 180 loads 186
Is programmed to move the set distance fork corresponding to the type of.

The first and second forks 30 and 32 are moved laterally toward predetermined first and second initial positions. The initial sensors 204, 206 send electromagnetic radiation toward the forks 30, 32 and receive electromagnetic radiation reflected by the retroreflective strips 208, 210 when the forks 30, 32 are in place and responsive thereto. It outputs the first and second initial signals. The controller 180 receives these initial signals and stops the movement of the forks 30 and 32 at the first and second predetermined positions, respectively.

From the initial position, the forks 30, 32 are moved outwardly in opposite directions. The fork position sensors 80, 82 are on the surface 126 of the placards 128, 130.
The upper mark 124 is read and a signal is sent to the controller 180. The controller 180 is programmed with the spacing and dimensions of the marks 124 so that it keeps track of the position of the forks 30, 32 relative to the displaceable side frame 20. When the first fork 30 reaches half the desired distance between it and the centerline of the displaceable side frame 20, its movement is stopped. When the second fork 32 reaches half the desired distance between it and the centerline of the displaceable side frame 20, its movement is stopped.

Displaceable side frame 20 and associated forks 30, 32 (distance "D" between them)
Are positioned so that the forks 30, 32 can be located within the load opening 188. Fork tip sensor 10
The vertical search 212 is completed using 2, 104.
The carriage assembly 12 is moved along the upright body 10. The fork tip sensors 102, 104 detect the lateral edges 194, 196 and the controller 180 utilizes the vertical position sensor 110 to detect the edge 19.
Calculate the height of 4,196. The approximate height of the center of the load opening 188 is the first and second lateral edges 194, 196.
It is calculated by averaging the heights of. The controller 180 then moves the carriage assembly 12,
The fork is placed at the evaluated height in the center of the load opening 188.

A similar search is made to find the lateral center of the load opening 188. The displaceable side frame 20 is moved along the first guide portion 14. Fork tip sensors 102, 104 detect vertical edges 190, 192 of load opening 188. The position of the vertical edges 190, 192 with respect to the carriage assembly 12 is calculated based on the time taken to move the fork between the center position and the first and second vertical edges 190, 192. The lateral center of the load opening 188 is calculated by averaging the stored positions. The displaceable side frame 20 is moved laterally to the center.

The forks 30, 32 are now centered on the displaceable side frame 20 and the displaceable side frame 20 is centered with respect to the load opening 188. The controller 180 commands the load engagement drive system 140 to move the lift mast assembly 8 toward the load opening 188 and engage the load 186. Once fork 3
When 0, 32 are completely within load opening 188, controller 180 causes vertical carriage assembly drive system 7 to move.
0 is given to move the carriage assembly 12 upward along the upright body 10 to lift the load 186. Once the load 186 is raised to a predetermined vertical position, the carriage assembly 12 is stopped from moving. The displaceable side frame 20 is then positioned laterally with respect to the carriage 18 to assess bad lateral loading or improper load distribution with respect to the center of gravity of the AGV 4.

The carriage assembly 12 and load 186 are
It is then lifted and placed on deck 13 for transportation by vertical carriage assembly drive system 70 and load engagement drive system 140.

In another embodiment, the type and size of load 186 to be shipped is not programmed into controller 180. Therefore, the forks 30, 32
The desired distance "D" between is unknown. The desired distance "D" is
It is calculated by using the first and second fork tip sensors 102 and 104. The first fork 30 is moved in a first lateral direction with respect to the displaceable side frame 20 and is stopped when the first vertical edge 190 is detected. The second fork 32 is moved in a first lateral direction with respect to the displaceable side frame 20 and is stopped when the first vertical edge 192 is detected. Thus, the forks 30, 32 are positioned in front of the first and second vertical edges 190, 192, respectively.

The forks 30, 32 are centered with respect to the displaceable side frame 20 in order to ensure proper loading and avoid inappropriate load distribution on the AGV 4, as well as the displaceable side frame. 20 must be centered with respect to load opening 188. First, the first and second forks 30, 32 and their respective edges 190, 192
A desired distance "D" between the forks 30, 32 is calculated which allows a set distance between.

The controller 180 provides a signal indicating the position of the first and second forks 30, 32 with respect to the vertical edges 190, 192 of the load opening 188, the first, second 30, with respect to the displaceable side frame 20 ,. A signal indicating the position of 32 and a signal indicating the position of the displaceable side frame 20 with respect to the carriage 18 is received. Displaceable side frame 20 and forks 30, 32 are displaceable side frame 20 such that they are centered with respect to the load opening 188.
It is possible to calculate the offset distance that must be moved. When the forks 30, 32 are centered on the displaceable side frame 20, the displaceable side frame 20 and the forks 30, 32 are moved an offset distance. The load 186 can now be lifted and shipped as described above.

[Brief description of drawings]

FIG. 1 is a schematic side view of an automated guided vehicle having a lift and mast assembly, in which a load at a transportation position is indicated by a virtual line and a load in a loading process is indicated by a solid line.

2 is a schematic partial front view of the lift and mast assembly of FIG. 1. FIG.

FIG. 3 is a schematic side view of one fork showing the positions of the fork position sensor and fork tip sensor.

FIG. 4 is a diagram showing another embodiment of first and second detecting means.

FIG. 5 is a block diagram of part of an embodiment of an electronic control system.

6 is an electrical wiring diagram showing a part of an embodiment of the control system of FIG.

FIG. 7 is a block diagram of an example of a portion of control software.

FIG. 8 is a block diagram of another embodiment of a portion of control software.

[Explanation of symbols]

 2 Material Handling Vehicle 4 Automated Guided Vehicle (AGV) 6 Frame 8 Lift / Mast Assembly 10 Vertical Solid 12 Carriage Assembly 13 Deck 18 Carriage 20 Displaceable Side Frame 21 Carriage Frame 30 First Fork 32 Second Fork 42 Shank 44 Load-engaging portion 50 First drive means 51 First drive system 52 Second drive means 53 Second drive system 54 First electric actuator 56 Second electric actuator 60 Third drive means 61 Lateral carriage assembly drive means 62 Hydraulic cylinder 70 Vertical carriage assembly drive system 72 Hydraulic lift cylinder 80 First detection means 81 First position sensor 82 Second detection means 83 Second position sensor 90 Third detection means 91 Lateral position sensor 92 Hall effect Sensor 94 Permanent magnet 100 fourth sensing means 102 first fork tip sensor 104 second fork tip sensor 110 vertical position sensor 122 bar code system 124 mark 128 first elongated placard 130 second elongated placard 160 resolver system 162 Ladder assembly 166 First toothed element 168 Second toothed element 172 Resolver-to-digital converter 174 Resolver 176 Resolver 178 Control system 180 Controller 186 Load 188 Load opening 190 First vertical edge 192 Second vertical edge 194th 1 lateral edge 196 2nd lateral edge 200 5th sensing means 202 6th sensing means 204 1st initial sensor 206 2nd initial sensor 208 1st retroreflective strip 210 2nd retroreflective strip

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Paul Dee Grossmeyer Illinois, State of the United States 61525 Dunlop Boxx 126 (72) Inventor Jioseph Jei Harding Ohio, USA 44060 Mentor Blue Ark Court 6369 (72) Inventor Darren El Klaan United States Ohio 44060 Mento Marine Parkway 6001 B 110

Claims (20)

[Claims] 1. A lift mast assembly (8) having a frame (6) and a lift mast assembly (8).
Is a pair of spaced upright solids (10) connected to the frame (6) and a carriage assembly (which is connected to these upright solids (10) and is movable along these upright solids (10). 12) and first and second forks (3) connected to the carriage assembly (12) and movable relative to the carriage assembly across the uprights (10).
0, 32) and a material handling vehicle (2)
The first fork (3) for the carriage assembly (12)
0) for detecting the lateral position of the second fork (32) with respect to the carriage assembly (12) and first detecting means (80) for generating a first signal in response to the detected position. And a second detection means (80) for generating a second signal in response to the detection position, and receiving the first and second signals and combining the first and second signals as a set. Control means (180) for processing in accordance with programmed instructions and responsively generating first and second movement signals; and a first fork (30) for receiving said first movement signal and responsive thereto
Drive means (50) for moving the carriage to a predetermined position relative to the carriage assembly (12) as described by the programmed instructions, and receiving a second movement signal in response to the second movement signal. 2 forks (30)
A material handling vehicle including second drive means (52) for moving the carriage assembly (12) to a predetermined position as described by the programmed instructions. 2. A material handling vehicle according to claim 1, wherein the first and second sensing means (80, 82) include a bar code system. 3. The material handling vehicle of claim 1, wherein the first and second sensing means (80, 82) include a resolver system. 4. A vehicle according to claim 1, wherein said carriage assembly (12) has a first guide portion (14) oriented laterally with respect to the upright body (10). A displaceable side frame (20) having a second guide portion (16) oriented substantially parallel to the first guide portion (14), the displaceable side frame (20) being a carriage. (18) connected to a side frame (20) which is movable along the first guide portion (14) and in which the first and second forks (30, 32) are displaceable. And a material handling vehicle characterized by being movable along the second guide portion (16). 5. The material handling vehicle according to claim 4, wherein the position of the displaceable side frame (20) with respect to the carriage (18) is detected, and the displaceable side frame (20) has a predetermined lateral direction. A third sensing means (90) for outputting a third signal in response to the third signal when in the position, the control means (180) receiving the third signal, the third signal and a set. A means for generating a third movement signal in response to the programmed command of the third movement signal and further responsive to receiving the third movement signal to program the displaceable side frame (20). A material handling vehicle characterized in that a third drive means (60) for moving the carriage (18) to a predetermined position according to the command is provided. 6. The material handling vehicle according to claim 1, wherein the vertical edges (190, 19) of the load opening (188).
2) is included, and fourth control means (100) for generating a fourth signal and a fifth signal in response thereto are included, and the control means (180) receives the fourth and fifth signals. Then
A material handling vehicle including means for positioning the first and second forks (30, 32) with respect to the load opening (188). 7. A frame (6) and a lift-mast assembly (8), the lift-mast assembly (8) being connected to the frame (6) with a pair of spaced upright solids (8). 10), and a carriage assembly (12) connected to the upright solid (10) and movable along the same, and a carriage assembly (12) connected to the upright solid (10).
First and second forks (30, 32) movable relative to the carriage assembly (12) across the carriage assembly (12), the carriage assembly (12) being lateral to the upright body (10). A displaceable side frame (20) having a first oriented guide portion (14) and a second guided portion (16) oriented substantially parallel to the first guide portion (14), A lateral frame (20) is connected to the carriage (18) and is movable along the first guide portion (14). The first and second forks (3) are
0, 32) is connected to the displaceable lateral frame (20) and is displaceable in a material handling vehicle (2) adapted to move along the second guide portion (16). The lateral position of the first fork (30) with respect to the side frame (20) is detected to detect the first fork (30).
The first sensing means (80) for generating a first signal in response to this position of the second fork and the lateral position of the second fork (30) with respect to the displaceable side frame (20). Second detection means (82) for generating a second signal in response to this position of (30) and the position of the displaceable side frame (20) relative to the carriage (18),
A material handling vehicle including a third sensing means (90) for outputting a third signal in response to the displaceable side frame (20) in a predetermined lateral position. .. 8. A frame (6) and a lift-mast assembly (8), the lift-mast assembly (8) being connected to the frame (6) with a pair of spaced upright solids (8). 10) and a carriage (18) having a first guide portion (14) oriented laterally with respect to the upright body (10) and a second guide portion (orientated substantially parallel to said first guide portion (14). Displaceable lateral frame (20) with 16)
A carriage assembly (12) including a carriage, the displaceable lateral frame (20) being connected to a carriage (18), the carriage being movable along a first guide portion (14). An assembly (12) is connected to the upright body (10) and is movable along it, said carriage (18) having first and second forks (30, 32) and a carriage assembly (12). ), And is movable in a direction traversing the upright body (10) with respect to the carriage assembly (12), and the first and second forks (30, 3).
2) each have a shank (42) and a load-engaging portion (44), which load-engaging portion (44) extends substantially away from the material handling vehicle (2), said shank (42) ) Detects the position of the first fork (30) in the material handling vehicle which is connected to the second guide portion (16) and generates a first signal in response to the position. And including an elongated member (120) having a surface (126) and a plurality of distinguishable, spaced-apart marks (124) disposed along the surface (126), the elongated member (120) being a first 1 guide part (14)
Carriage assembly (12) substantially parallel to and
First sensing means (80) coupled to the first surface and the surface (120) facing the first and second shanks (42);
Second detecting means (82) for detecting the position of the second fork (32) and generating a second signal in response to the position,
Second sensing means (8) including said elongated member (120).
2) and a control means (180) for receiving the first signal, generating a first movement signal in response to the first signal, and receiving a second signal, and generating a second movement signal in response to the second signal. The first fork (30) is controlledly moved with respect to the carriage assembly (12) in response to the first movement signal, and the displaceable side frame (20) and the first side frame (20).
First drive means (5) connected between the shanks (42)
0) and in response to the first movement signal, the second fork (32) is controlledly moved with respect to the carriage assembly (12), and the side frame (20) is displaceable. A second drive means (52) connected between the second shanks (72) and including the first sensing means (8).
0) sends electromagnetic radiation towards the surface (126) of the elongate member (120), receives its reflection and then sends the first signal in response thereto,
The second sensing means (82) is the elongated member (120).
Of electromagnetic radiation in the direction of the surface (126) of the same, receiving its reflection and then transmitting the second signal in response thereto, the first and second sensing means (80, 8).
2) is connected to the first and second forks (30, 32) respectively, and these first and second forks (30, 3) are connected.
A second guide portion (16) in response to each movement of 2).
A material handling vehicle characterized in that it is adapted to move along. 9. The material handling vehicle of claim 8, wherein the elongated member (120) is coupled to a displaceable lateral frame (20) of first and second placards (12).
Material handling vehicle characterized by including (8, 130). 10. A lift mast assembly (8) having a frame (6) and a lift mast assembly (8).
Has a pair of spaced upright solids (10) connected to the frame (6) and a first guide portion (14) oriented laterally with respect to the upright solids (10). Carriage assembly (1
2) and first and second forks (which are connected to the carriage assembly (12) and are movable relative to the carriage assembly (12) and laterally with respect to the upright body (10). Material handling vehicle having (30, 32) (2)
In the first detecting means (8) for detecting the position of the first fork (30) and generating a first signal in response to the position.
0) and having an elongated surface (126) (12)
0) and a plurality of distinguishable, spaced-apart marks (124) located along the surface (126), said elongated member (120) being substantially parallel to the first guide portion (14). And connected to the carriage assembly (12), the surface (120) being provided with first and second shanks (4).
2) a first detecting means (80) facing the second detecting means (80) and a second detecting means (82) for detecting the position of the second fork (32) and generating a second signal in response to the position, A second sensing means (82) including said elongate member (120); receiving a first signal and generating a first movement signal in response to it; and receiving a second signal in response to it. A control means (180) for generating a second movement signal, and a first means for controlling the first fork (30) to move relative to the carriage assembly (12) in response to the first movement signal. A first driving means (50) and a second driving means (52) adapted to move the second fork (32) relative to the carriage assembly (12) while controlling the second fork (32) in response to the first movement signal. And the first detection means (8
0) sends electromagnetic radiation towards the surface (126) of the elongate member (120), receives its reflection and then sends the first signal in response thereto,
The second sensing means (82) is the elongated member (120).
Of electromagnetic radiation in the direction of the surface (126) of the same, receiving its reflection and then transmitting the second signal in response thereto, the first and second sensing means (80, 8).
2) is connected to the first and second forks (30, 32) respectively, and these first and second forks (30, 3) are connected.
A second guide portion (16) in response to each movement of 2).
A material handling vehicle characterized in that it is adapted to move along. 11. The material handling vehicle of claim 10, wherein the elongated member (120) is connected to a carriage assembly (12) with first and second placards (128, 128).
130) A material handling vehicle characterized by including the above. 12. The material handling vehicle according to claim 8, wherein the displaceable side frame (20) is attached to the first guide edge (1).
4) A third drive means (6) for moving along with control
0) and the position of the displaceable side frame (20) with respect to the carriage (18) and in response to this when the displaceable side frame (20) is in a predetermined lateral position, a third Detection means (90) for outputting the signal of
And the first and second upright edges (19) of the load opening (188).
0, 192) and outputs a fourth and a fifth signal in response to the respective detection, the control means (180) includes a fourth and a fourth detection means (100). The fifth signal is received and the sixth and seventh signals are output. When the fourth signal is received, the movement of the first fork (30) is stopped in response to the reception of the fourth signal. Responsive to receiving a fifth signal, the movement of the second fork (32) is stopped, and the first and second load engagements of the first and second forks (30, 32) are performed. The position is calculated, and when the first and second load engaging positions are substantially positioned on the displaceable side frame (20),
A second fork (30, 32) allows the load opening (18
8) so that the vehicle can enter the inside, and outputs the eighth and ninth signals, respectively, at the first and second load engaging positions, respectively.
Stop the forks (30, 32) of the
The position of the displaceable side frame (20) with respect to the load opening (188) is calculated when the signal is received, and the displacement is calculated when the calculated position substantially matches the load opening (188). Comprising programmable microcomputer software means adapted to move the possible lateral frame (20) to a computing position,
A first fork (30) in a first lateral direction in response to the first drive means (50) receiving the sixth signal.
For moving the first fork (30) in the second lateral direction in response to the reception of the eighth signal, and the second driving means (52) for moving the first fork (30). When the 9th signal is received, the second fork (32) is moved in the first lateral direction in response thereto, and when the 7th signal is received, the second fork (32) is moved in the second lateral direction in response thereto. ) Is a material handling vehicle characterized by being adapted to move. 13. The material handling vehicle of claim 10, wherein the first fork (30) is moved in the first lateral direction in response to the sixth signal received by the first drive means (50). , The first fork (30) is moved in the second lateral direction in response to the reception of the seventh signal, and when the second driving means (52) receives the eighth signal. In response to this, the second fork (32) is moved in the first lateral direction, and when the ninth signal is received, the second fork (32) is moved in the second lateral direction in response thereto. The control means (18
0) includes programmable microcomputer software means for initializing first and second variables indicating first and second fork initial positions, outputting the sixth signal and outputting the first signal. In response to the reception, the first predetermined value is added to the first variable, the seventh signal is output, and when the first signal is received, the second predetermined value is set in the first variable in response. Values are added, the eighth signal is output, and the second signal is output in response to the second signal when the second signal is received.
Adding a third predetermined value to the variable and outputting the ninth signal,
A fourth predetermined value is added to the second variable in response to receiving the second signal, and in response thereto when the first variable is equal to a fifth predetermined value, the first fork (3
0) the movement of said second fork (32) in response to said second variable being equal to a sixth predetermined value.
Material handling vehicle characterized by stopping the movement of the. 14. A pair of spaced upright solids (10) having a frame (6) and a lift mast assembly (8) connected to the frame (6), and a upright solid (10). A carriage assembly (12) having a first guide portion (14) oriented laterally with respect to it, connected to the upright body (10) and movable along it; and this carriage assembly (12). Connected to the carriage assembly (1
In a material handling vehicle (2) having first and second forks (30, 32) movable relative to 2) and laterally with respect to the upright body (10), the first fork (3)
0) for detecting the position and generating a first signal in response to the position, and a second fork (32).
Second detecting means (82) for detecting the position of the first position and generating a second signal in response to the position, receiving a first signal and generating a first movement signal in response to the second signal, and Control means (180) for receiving a signal and generating a second movement signal in response to the signal; and controlling a first fork (30) for the carriage assembly (12) in response to the first movement signal. The first driving means (5
0), and second drive means (52) adapted to move the second fork (32) relative to the carriage assembly (12) in response to the first movement signal.
A first predetermined initial position is detected, and the first fork (3
0) is in the first predetermined initial position and outputs a first initial signal in response to the fifth initial detection signal (200),
The second predetermined initial position is detected, and the second fork (3
2) includes a sixth detecting means (202) which outputs a second initial signal in response to the second predetermined initial position, and the control means (180) includes the first and second Upon receiving an initial signal, in response thereto, the movement of the first and second forks (30, 32) is stopped, and the fifth and sixth detection means (200, 202).
The first and second initial sensors (204, 206) connected to the carriage assembly (12) and the first and second retroreflective reflections connected to the first and second forks (30, 32) respectively. A strip (208, 210), the first and second initial sensors (204, 206) including the first,
Adapted to emit electromagnetic radiation in the respective directions of the second retroreflective strips (208, 210), receive reflections of this electromagnetic radiation and, in response thereto, output the first and second initial signals. A vehicle for handling materials that is characterized by 15. A lift mast assembly (8) having a frame (6) and a lift mast assembly (8).
A carriage (18) having a pair of spaced upright solids (10) connected to a frame (6) and a first guide portion (14) oriented laterally with respect to the upright solid (10); Displaceable lateral frame (20) having a second guide portion (16) oriented substantially parallel to the first guide portion (14).
A carriage assembly (12) including a carriage, the displaceable lateral frame (20) being connected to a carriage (18), the carriage being movable along a first guide portion (14). (18) is connected to the upright (10) and is movable along it, each of which is a shank (42) and a material handling vehicle (2).
A first and a second fork (30, 32) having a load engaging portion (44) extending substantially away from the shank (42) connected to the second guide portion (16); In the automated guided vehicle (2), the first and second forks (30, 32) are movable relative to the carriage assembly (12) along the second guide portion (16), with the surface (126) and this. A plurality of distinguishable, spaced-apart marks (124) disposed along a surface (126) and coupled to a displaceable side frame (20), the surface (126) being the first fork. Facing the shank (42) of (30) and said second guide portion (16)
A first elongate placard (128) substantially parallel to, a surface (126) and a displaceable lateral frame (20) disposed along the surface (126).
A plurality of distinguishable, spaced-apart marks connected to
And the surface (126) has the second fork (3).
2) a second elongated placard (130) facing the shank (42) and substantially parallel to the second guide portion (16), and the first placard member (128). First sensing means (80) for emitting electromagnetic radiation in the direction of the surface of the device, receiving reflections of this electromagnetic radiation and responsively transmitting a first signal, which is connected to the first fork (30). A first sensing means (80) movable along the second guide portion (16) in response to the movement.
And second detection means (82) for sending electromagnetic radiation toward the surface of the second placard member (130), receiving reflection of the electromagnetic radiation, and sending a second signal in response to the reflection. A second sensing means (82) connected to the second fork (32) and movable along the second guide portion (16) in response to the movement thereof, and a carriage (1).
Third, sensing the position of the displaceable side frame (20) with respect to 8) and responsive to it to issue a third signal when the displaceable side frame (20) is in a predetermined lateral position. Detecting means (90) and fourth detecting means for detecting the first and second vertical edges (190, 192) of the load opening (188) and outputting fourth and fifth signals in response thereto. (100) and a first lateral direction relative to the carriage assembly (12) in response to receiving the seventh signal.
Moving the fork (30) under control,
First drive means (50) for moving the first fork (30) in a second lateral direction relative to the carriage assembly (12) in response to receiving the signal, and responsive to receiving the ninth signal Then, the second fork (32) is moved in the first lateral direction while being controlled, and the second fork (32) is moved in the second lateral direction in response to the reception of the tenth signal. Second drive means (52),
Displaceable lateral frame (20) with first guide edge (14)
Third drive means (60) for moving along with control
And receiving the first and third signals, the carriage assembly (1
The position of the first fork (30) with respect to 2) is calculated, the second signal is received, the position of the second fork (32) with respect to the carriage assembly (12) is calculated, and the fourth and fifth signals are received. And sends the sixth signal and the ninth signal to stop the movement of the first fork (30) in response to the reception of the fourth signal, and the second signal in response to the reception of the fifth signal. Stop the movement of the fork (32),
The first and second load engaging positions of the second fork (30, 32) are calculated, and the first and second load engaging positions are substantially above the center of the displaceable side frame (20). To allow the first and second forks (30, 32) to enter the load opening (188) when in the first and second load engaging positions, respectively. Fork (30,3
2) is stopped and the displaceable lateral frame (2) relative to the load opening (188) in response to the third signal.
0) position to align the displaceable side frame (20) with the load opening (188) when the calculated position is substantially coincident with the load opening (188). An automatic guided vehicle, characterized in that it includes a control means (180) adapted to 16. The automatic guided vehicle according to claim 15, wherein a first predetermined initial position is detected, and when the first fork (30) is at the first predetermined initial position, the first initial position is responsive thereto. Fifth detection means (200) for outputting a signal
And a sixth detecting means (202) for detecting a second predetermined initial position and outputting a second initial signal in response to the second predetermined fork (32) being in the second predetermined initial position.
And the control means (180) includes the first and second
The automatic guided vehicle which is adapted to stop the movement of the first and second forks (30, 32) in response to the initial signal from the vehicle. 17. The automated guided vehicle as set forth in claim 16, wherein the fifth and sixth detection means (200, 202) are connected to a carriage assembly (12). 206) and first and second retroreflective strips (208, 210) connected to first and second forks (30, 32), respectively, said first and second initial sensors (204). , 206) emits electromagnetic radiation in the direction of the first and second retroreflective strips (208, 210), receives reflections of this electromagnetic radiation and, in response, outputs the first and second initial signals. An automated guided vehicle characterized in that it is designed to be delivered. 18. A method of controlling and moving first and second forks (30, 32) of a material handling vehicle (2) to align with a load (186) having a load opening (188). , The forks (30, 32) have fork tip sensors (102, 104) and fork position sensors (81, 83), and the load opening (188) is approximately equidistant from the centerline. A material handling vehicle (2) having first and second vertical edges (190, 192) separated from each other is provided with a pair of uprights (10) and uprights (1).
Displaceable lateral frame (2) that can be moved across
0) and a microcomputer, wherein the first and second predetermined positions are respectively provided in the first and second initial positions.
Positioning the forks (30, 32) of the vehicle, moving the first and second forks (30, 32) to their respective lateral positions, and the first and second forks (30, 32), respectively. Generating a first and a second position signal in response to detecting the position of the first and second vertical edges (190) of the load opening (188) in response to detecting the first position. Generating an edge signal, generating a second edge signal in response to detecting the second vertical edge (192) of the load opening (188), the first edge signal and the first edge signal. Calculating a position "X" in response to a position signal, calculating a position "Y" in response to the second edge signal and the second position signal, and the first and second forks ( 30 and 32) respectively in position "X",
Positioning at "Y", detecting the position of the displaceable side frame (20) with respect to the material handling vehicle (2), and displaceable for at least one of the sensed vertical edges (190, 192) Side frame (20)
Calculating the position of the centerline of the. 19. A method according to claim 18, wherein the step of moving the first and second forks (30, 32) in their respective lateral directions comprises:
A method comprising positioning between them a predetermined position having a distance D relative to a centerline. 20. The method according to claim 19, wherein the fork (30, 32) is displaceable on the side frame (2).
0) and further includes the first fork (3).
0) is at position "X" and the second fork (32) is at position "Y" so that the side frame (20) and its associated forks (30, 3) are displaceable.
2. A method comprising the step of moving 2) laterally.