U.S. patent number 3,617,962 [Application Number 05/025,344] was granted by the patent office on 1971-11-02 for automatic guidance system for vehicles.
This patent grant is currently assigned to American Chain & Cable Company, Inc.. Invention is credited to Kenneth A. Wilson.
United States Patent |
3,617,962 |
Wilson |
November 2, 1971 |
AUTOMATIC GUIDANCE SYSTEM FOR VEHICLES
Abstract
A switch device for placement in a floor for an automatic
vehicle guidance system utilizing a reed switch encased in the
floor having armature plates extending from the reed switch to the
floor surface to detect the presence of a vehicle.
Inventors: |
Wilson; Kenneth A. (Locust
Valley, NY) |
Assignee: |
American Chain & Cable Company,
Inc. (New York, NY)
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Family
ID: |
21825458 |
Appl.
No.: |
05/025,344 |
Filed: |
April 3, 1970 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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680182 |
Nov 2, 1967 |
3512601 |
May 19, 1970 |
|
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Current U.S.
Class: |
335/151 |
Current CPC
Class: |
G05D
1/0265 (20130101); B65G 47/496 (20130101); H01H
36/0006 (20130101) |
Current International
Class: |
H01H
36/00 (20060101); B65G 47/49 (20060101); B65G
47/48 (20060101); G05D 1/02 (20060101); H01h
036/00 (); H01h 051/28 () |
Field of
Search: |
;335/151,154,205 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Gilheany; Bernard A.
Assistant Examiner: Envall, Jr.; R. N.
Parent Case Text
This application is a division of y copending application Ser. No.
680,182, filed Nov. 2, 1967 , now U.S. Pat. No. 3,512,601 issued
May 19, 1970.
This invention relates to guidance systems and particularly to
guidance systems for unmanned self-propelled vehicles such as
tractors which are utilized in warehouses and the like for
transporting loads from one destination to another.
Claims
I claim:
1. A switch device for placement in a floor comprising a
casing,
an armature in said casing having an end thereof exposed whereby
when said casing is placed in the floor, the end of said armature
extends and faces upwardly,
a reed switch positioned beneath said armature,
and encapsulating material surrounding said armature and said reed
switch and filling said casing,
said armature comprising angularly related armature plates.
2. The combination set forth in claim 1 including a plastic support
to which the armature plates are adhered.
3. The combination set forth in claim 2 wherein said plastic
support has a hollow opening in which said reed switch is
positioned.
4. The combination set forth in claim 3 wherein said armature
plates, plastic support and reed switch comprise a subassembly,
and an insulating coating applied to said subassembly.
5. The combination set forth in claim 4 wherein said encapsulating
material comprises epoxy resin.
6. The combination set forth in claim 5 wherein said reed switch
comprises a monostable reed switch.
7. The combination set forth in claim 5 wherein said reed switch
comprises a bistable reed switch.
Description
BACKGROUND OF THE INVENTION
It has been well known that an unmanned self-propelled vehicle may
be guided along a predetermined path defined by an energized
conductor by sensing the position of the conductor and guiding the
vehicle along the path defined by the conductor. Such a system is
shown, for example, in the U.S. Pat. to Paulus et al. No.
2,317,400. In such systems, various decision points are provided as
where the paths intersect, diverge or converge as well as when the
vehicle reaches the desired destination. In the U.S. Pat. to De
Liban No. 3,147,817, there is disclosed a system wherein the guide
path is defined by conductors that are energized at two different
frequencies at least at the decision points and the sensor on the
vehicle is controlled or tuned at a decision point so that it is
responsive only to one of the two frequencies. Obviously, such a
system requires separate energizing sources for the various paths
as well as accurately controlled sensor means. In the U.S. Pat. to
Barrett No. 3,245,493, there is disclosed a system wherein at each
decision point, there is a gap or space in the guide path and the
steering mechanism of the vehicle is locked in a straight line by
an internally generated signal so that the sensor that normally
guides the vehicle is, in effect, bypassed at the decision point.
Such a system is undesirable in that the movement of the vehicle is
not being positively controlled while the vehicle is in this gap
between conductor portions.
Among the objects of the present invention are to provide a
guidance system which effectively controls the vehicle by selective
energization of a single conductor closed circuit system at the
decision points; which is relatively simple and requires a minimum
of maintenance: which utilizes novel control devices; and wherein
the control devices derive their energy from the guide path
conductor.
SUMMARY
The guidance system disclosed herein comprises a guide path to be
followed by the vehicle which is defined by a conductor or wire
embedded in the floor. The conductor is connected to produce a
single closed circuit energized by a constant current oscillator.
The vehicle includes sensor means which follows the energized
conductor and guides the vehicle along the path. The path may
contain various decision points such as points at which portions of
the conductor are brought into close proximity so that the vehicle
must decide which path to follow, such as points where the paths
intersect, diverge and converge. The guide path includes separately
energizable portions at such decision points, controlled by guide
path control devices, which are selectively energized upon signal
from the vehicle so that only that portion is energized which lies
along the direction in which it is desired that the vehicle travel.
Where a plurality of vehicles are provided, provision is made for
causing a leading vehicle to energize a holding loop at a point
behind the leading vehicle which produces a signal that is received
by a succeeding vehicle and causes the succeeding vehicle to be
stopped until the leading vehicle has passed the predetermined
point. Similar blocking devices are associated with the
aforementioned decision points.
Some of the guide path control devices derive energy from the guide
path conductor and incorporate a novel construction.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram of a typical guide path embodying the guidance
system of the present invention.
FIG. 2 is a partly diagrammatic fragmentary view of a vehicle
utilized in the system.
FIG. 3 is a diagrammatic plan view of a vehicle utilized in the
system.
FIG. 4 is a schematic wiring diagram of the intersection shown in
FIG. 1 when utilized for a single vehicle system.
FIG. 5 is a schematic diagram of the point of divergence of the
path shown in FIG. 1 when utilized for a single vehicle system.
FIG. 6 is a schematic diagram of the point of convergence in the
guide path shown in FIG. 1 when utilized for a single vehicle.
FIG. 7 is a schematic diagram of a portion of the guidance system
shown in FIG. 1 wherein a plurality of vehicles are used.
FIG. 8 is a schematic diagram of the intersection shown in FIG. 1
wherein a plurality of vehicles are used.
FIG. 9 is a schematic diagram of the diverging point shown in FIG.
1 when a plurality of vehicles are used.
FIG. 10 is a schematic diagram of the converging point shown in
FIG. 1 when a plurality of vehicles are used.
FIG. 11 is a wiring diagram showing the manner in which the portion
of the guide path containing the diverging and converging points is
electrically connected.
FIG. 12 is a block diagram of the control system.
FIG. 13 is a fragmentary side elevational view of a portion of a
floor module in position.
FIG. 14 is a part sectional elevational view of the module shown in
FIG. 13.
FIG. 15 is a part sectional elevational view of another form of
module.
FIG. 16 is a plan view of the same.
FIG. 17 is a schematic diagram of the same.
FIG. 18 is a wiring diagram of the same.
GENERAL DESCRIPTION
Referring to FIG. 1, the guide path 10 shown is utilized for
controlling the movement of one or more vehicles such as tractors
which may pull trailers between stations 1, 2 and 3. As shown, the
guide path includes an intersection I, a diverging intersection II
wherein the vehicle can move in one of two paths 21, 22, the latter
extending to station 3, and a converging intersection III.
As will appear more clearly hereinafter, the guide path 20 is
defined by a single circuit comprising conductors or wires embedded
in the floor and so connected that at all times a single circuit is
defined. The conductor is energized by a constant current
oscillator, for example, at a frequency of 2 kc. and one-eighth
amperes.
Referring to FIG. 2, the vehicle T which may comprise a tractor is
provided with rear drive wheels 24 that are driven by a motor 25
through a differential 26 and a front dirigible style steering
wheel 27 that is steered by a steering motor 28. A control system
is provided on the vehicle which senses readers along the guide
path and produces an appropriate signal for selectively energizing
portions of the guide path along which the vehicle is to pass, as
more fully described hereinafter. The control system includes a
programming selector or sensor 29 into which the operator places or
selects a destination to which the vehicle is to be guided.
Referring to FIG. 3, the vehicle includes sensor means 30 which are
utilized to control the steering motor 28 and steer the vehicle
along the energized guide path as described, for example, in the
U.S. Pat. to Hosking et al. No. 3,039,954, issued June 19, 1962. In
addition, the vehicle has a permanent magnet 31 thereon which is
utilized in the path control system and a selectively energizable
electromagnet 32 which is also utilized in the path control
system.
Further, the vehicle supports a signal device path as a pickup coil
33 that is utilized in controlling the movement of the vehicle and
particularly in stopping the vehicle in the event that a leading
vehicle is interrupted in its movement or is closer than a
predetermined interval with respect to the succeeding vehicle.
In addition, selectively energizable sensing means in the form of
two bars 34, 35 supporting sensing devices are provided for sensing
or reading signals placed in predetermined positions along the path
of the vehicle to produce guidance of the vehicle along the
shortest path and to stop the vehicle at the predetermined
destination.
GUIDE PATH CONTROL SYSTEM --SINGLE VEHICLE
Referring to FIG. 1, in areas of the guide path wherein the guide
path intersects other paths or portions of the guide paths move
into close proximity so that it is necessary to make a decision as
to which path is to be followed by the vehicle, the path control is
achieved by selectively energizing one of two portions at such
points shown in FIG. 1 as I, II and III.
Referring to FIG. 4, the manner in which the decision is made at
points of intersection is shown schematically in FIG. 4. Thus, a
vehicle approaching the intersection along path portion 50 defined
by a conductor momentarily actuates a normally closed monostable
device 51 that controls a bistable device 56 which energizes a
portion 52 of the intersecting guide path 53 and deenergizes a
portion 54. The bistable device 56 incorporates a holding circuit
which maintains the portion 52 energized. Thus, as the vehicle
approaches the intersection of paths 50 and 53, only path 50 is
energized and the sensor means on the vehicle will thus cause the
vehicle to follow along path 50. As the vehicle further moves and
passes the intersection, a second normally open monostable device
55, in advance of conductor portion 52, returns the bistable device
56 to its original state to deenergize the bypass circuit 52 so
that current will flow through the normal path 54. Similarly, when
a vehicle approaches the intersection along path 53, a normally
closed monostable device 57 is utilized to energize a bypass
portion 58 and deenergize the principal portion 59' of the path 50.
Specifically, monostable device 57 actuates a bistable device 59 in
the bypass circuit 58 to energize the bypass circuit 58 until the
vehicle has passed the intersection and momentarily energizes a
normally open monostable device 60 which deenergizes the bistable
device 59 to deenergize the circuit 58 and reestablish the flow of
current across portion 59' of path 50.
The monostable devices 51, 55, 57 and 60 may comprise reed switches
that are embedded along the path and in the floor and are actuated
by a magnet on the vehicle such as a magnet 31 (FIG. 3). The
bistable devices 56, 59 may comprise monostable reed switches with
a holding circuit. As sown in the schematic diagram FIG. 4, the
bistable devices 56, 59 include a normally closed pair of contacts
62 which is electrically connected to complete a circuit between
portions 53, 54 of the conductor. THe bistable device further
includes a holding circuit 63. When the monostable device 51
interrupts the current flow through the portions 54, current can
only flow through the holding circuit 63 and thus maintains the
contacts 62 in open position until the second monostable device 55,
which is normally opened, is momentarily closed to short cross the
holding circuit 63 and reestablish current flow between portions
53, 54 of the conductor. The second bistable device 59 is similarly
connected.
The manner in which the conductor is selectively energized and
wired in order to control the vehicle at a point of divergence such
as shown at point II in FIG. 1 is shown in FIG. 5 wherein a
bistable device 65 which is a two position device without a holding
circuit is provided in the path of the vehicle and normally
completes a circuit thereby energizing a portion 66 that extends in
the normal path of the main portion 67 of the guide path. The
bistable device 65 normally interrupts the flow of current to a
second portion 68 of the conductor that is aligned and extends
between the portion 67 in the direction and the portion 68' in the
direction of the diverging path. Portion 68' is energized by a
conductor portion 69 that is parallel to another portion 70, and
the latter is interconnected to the portion 66 by a portion 71. It
can be seen that the portions 69, 70 have current flow therein in
opposite directions so that there is no net signal which would
produce a steering signal to the vehicle. As the vehicle approaches
the point of divergence, if the electromagnet 32 on the vehicle is
properly energized as will occur when a decision is made by the
path control system to cause the vehicle to diverge, the energized
electromagnet 32 on the vehicle will actuate the bistable device 65
to break the circuit to the portion 66 and complete the circuit to
the conductor portion 68 so that the vehicle will follow the
energized conductor portion 68 in the diverging path. The bistable
device 65 will remain in this position until it is again actuated
by an opposite signal from the electromagnet 32 of a succeeding
vehicle to return it to a condition for energizing conductor
portion 66 so that the vehicle will follow in a normal path between
portions 67 and 72a. A resistor 67a is provided in parallel with
portions 66, 68 to maintain a load in the circuit during momentary
switching and thereby obviate the possibility that the guide might
be momentarily open-circuited during switching.
The manner in which the control of conductor path energization at a
point such as the point of convergence III in FIG. 1 is shown
schematically in FIG. 6 wherein the portion of the guide path 72 is
electrically connected to a bistable device 75 of the
aforementioned B type such that current normally flows through a
guide path conductor portion 76 that extends from alignment with
the bypass portion 68' and is electrically connected to a portion
77 aligned with the portion 72b. The bypass conductor portion 68
has a portion 78 extending parallel to interconnecting portion 79
so that no signal is normally produced in that area. If a vehicle
is on the bypass conductor path 68 and approaches the point of
divergence, it passes through to the main path 77.
If, however, a vehicle approaches along the path 72, the permanent
magnet 31 on the vehicle actuates the bistable device 75
interrupting the flow to the portion 76 and permitting the flow of
current to portion 81 so that the vehicle will pass along the main
path to the portion 77. After the vehicle passes the point of
convergence, a monostable device 82 that is normally open is
momentarily closed to short circuit the holding circuit of the
bistable device 75 and reestablish flow of current to the portion
76.
In the aforementioned description, the monostable devices of the
simple switch type have been designated by the letter A, the
monostable devices with a holding circuit have been designated by
the letter B, and the bistable devices have been designated by the
letter S.
In devices of the B-type, the impedance of the holding circuit
portion is made much greater than the impedance of the guide path
portion. Thus, for example, in FIG. 6 the impedance of the holding
portion is much greater than the impedance of the guide path
portion 80--79--76 which is in parallel therewith. Thus, the two
paths will divide the current in inverse proportion to their
resistances. The current flow through path 81 is negligible
compared to the current flow through path 79 and the radiating
signal will be in the same proportion as the currents. When the
device 75 of the B-type is switched, the path 79 will be an open
circuit and all the current will be forced to travel through the
path 81. When the current is in the path 79, the power absorbed
from the signal generator will be small compared to the power
absorbed from the signal generator when the current is in the path
81. Since in the system of the present invention the circuits
normally maintain the B-type modules in the deenergized position
except when being traversed by a vehicle, only a few of the B-type
devices are "on" at any time so that the total energy absorbed by
the B-type devices is relatively low. Thus, it can be seen that in
all cases the impedance of the path in parallel with the holding
circuit is maintained at a low level.
It may be noted that in each of the figures, the arrows represent
travel of the vehicle as well as instantaneous current flow.
FLOOR MODULES
As will be apparent, the monostable and bistable devices that are
positioned in the floor are preferably in the form of encapsulated
modules. In the schematic drawings heretofore shown, the modules
have been also designated by the letters A, B and S. The module A
in the preferred form comprises a monostable reed switch. The
module B comprises a monostable reed switch with a holding circuit.
THe module S comprises a bistable reed switch.
Referring more specifically to FIGS. 13 and 14, the module A
comprises a casing 100 in which a subassembly is positioned. The
subassembly comprises angularly related armature plates 102 which
are fixed by an adhesive 103 to a plastic support 104 that has a
hollow opening supporting the encapsulated reed switch 105. A
silicon rubber dipped coating is applied to the subassembly and an
epoxy resin 106 holds and encapsulates the coated subassembly in
the casing 100. The entire module is inserted in an opening in the
floor with the upper end of the armature projecting beyond the
casing into substantially flush relation with the floor surface and
the leads L extending laterally outwardly and connected to the
conductor in a suitable manner. Grouting material G is provided
around the upper end of the armature.
The B module as shown in FIGS. 15 and 16 is substantially identical
to the A module except that it includes a coil wound around the
switch 105 and associated electronic elements which are shown in
schematic form in FIG. 17.
Referring to FIG. 18, the B-module in addition to the normally
closed contacts includes a holding circuit heretofore described by
the designation M which comprises two parallel branches 110, 111
that have oppositely directed diodes 112, 113 and oppositely wound
coils 114, 115 therein. Capacitors 116, 117 are provided in
parallel with the coils 114, 115. By this arrangement, the AC
current which is diverted into the branch of the B-module when the
contacts are opened is converted to a DC current that creates a
constant magnetic field in the vicinity of the reed and maintains
the contacts in open condition until the B-module is reset by short
circuiting across the contacts as occurs when an A-module is
subsequently momentarily closed.
The S-module is substantially identical to the A-module except that
instead of a monostable reed 105, a bistable reed switch is
provided.
GUIDE PATH CONTROL SYSTEM --MULTIPLE VEHICLES
Where multiple vehicles are used on a guide path such as shown in
FIG. 1, it is essential to provide that one vehicle will not
contact another, both in the normal movement along a single path
and at the points of decision such as at the intersection I,
diverging point II and converging point III.
In the movement of the vehicle along a single portion of the
conductor, interference or contact between successive vehicles is
eliminated by selectively energizing a holding coil or beacon 85
rearwardly of the vehicle to produce a signal that is sensed by the
coil 33 on the vehicle to stop the vehicle, (FIG. 7). The coils 85
are selectively energized by bistable devices 86 of the type
heretofore described which are electrically connected so that they
normally permit current flow through the conductor path. However,
as a vehicle passes each bistable device 86, the permanent magnet
31 on the vehicle momentarily interrupts the flow of current
through the main conductor so that current will flow through the
holding circuit 88 of the bistable device energizing the holding
coil 85 rearwardly of the vehicle and in the path of the succeeding
vehicle. As the preceding vehicle moves past the bistable device
86, the permanent magnet thereon momentarily completes a circuit to
a monostable device 89 that is electrically convected to the
succeeding bistable device 86 and momentarily shorts the holding
circuit 88 thereof to deenergize the holding coil 85. The
arrangement is such that one bistable device 86 is actuated to
energize its respective coil 85 before the monostable device 89 is
actuated to deenergize the previously energized holding coil
85a.
The manner in which such a blocking or stopping system is utilized
at a point of intersection such as intersection II in FIG. 1 is
shown schematically in FIG. 8 wherein the conventional wiring of
FIG. 4 is enclosed in broken lines. Where a plurality of vehicles
are used, in addition, bistable devices 86 that control holding
coils 85 and are reset by monostable devices 89 are provided along
the length of the intersecting guide path conductors. However, each
bistable device 86 not only energizes its respective holding coil
85 but, in addition, energizes an additional holding coil 90 along
the opposite path of the conductor so that a vehicle approaching
along the intersecting path will be stopped until the first vehicle
passes through. It should be noted that the holding coils 85 and 90
are schematically shown side by side for simplicity, but in actual
installations may be laid one on top of another, or in the same
slot in the floor, so that one sensor will sense either coil 85 or
coil 90 or both when they are energized.
Similarly, as shown in FIG. 9, where multiple vehicles are used at
the point of divergence, a bistable device 86 is provided on both
the main and diverging paths for energizing holding coils 85 for
interrupting the movement of a succeeding vehicle. As shown,
appropriate holding coils 85 are provided for controlling the
movement along the main path, the divergent path and the branch
path so that it is not possible that one vehicle will overtake
another.
As shown in FIG. 10, in the case of the converging point III in
FIG. 1, the bistable devices 86 not only energize a holding coil 85
for stopping a succeeding vehicle but, in addition, energize a
holding coil 91 along the converging path to interrupt a vehicle
that may be coming along the converging path toward the point of
intersection. In the system shown in FIG. 10, additional monostable
devices 92, 93 are provided. A vehicle passing over device 92 will
actuate B module 86--1. The vehicle, in turn, passes over device 93
and deactivates B module 86--2. This effectively transfers the hold
command from 86--2 to 86--1 so that device 89--3 will reset the
hold command 86--1 as the vehicle passes over 89--3. Also 89--3
will reset the holding of the intersection.
The manner in which the electrical connections are made in the area
of the guide path between diverging point II and converging point
III is shown in FIG. 11 wherein return paths 69a, 78a are provided
between the portions 72a and 69 and the portions 78 and 72b,
respectively. The cross hatching represents areas in which the
current flow is in opposite directions so that there is no net
signal which would interfere with steering.
It can be seen that in each of the path control connections that
are made by the various monostable or bistable devices, a
continuous circuit is maintained both in the main and what might be
termed divergent or convergent branch paths. As a result the
uniform maintenance of current supply is substantially insured
throughout the entire conductor.
Each of the monostable and bistable devices are inserted in the
floor preferably in small capsules so that they can be actuated as
desired by appropriate devices on the vehicle such as permanent or
electromagnets.
Although the use of the modules has heretofore been described in
connection with the control of the energization of one or two paths
in a guide path, the modules may also be utilized to control more
than two paths.
CONTROL SYSTEM --SUMMARY
Referring to FIG. 12 which is a schematic diagram of the
interrelationship between the control system on the vehicle and the
path control system along the path, the horizontal line represents
the floor which has embedded therein a conductor heretofore
described. The vehicle supports sensor means 30 in the form of
coils which are utilized to actuate a steering control for
operating a steering motor to steer the front wheel of the vehicle
and follow the path.
The monostable and bistable modules A, B and S which control the
selection of energization of portions of the guide path at the
decision points and the holding loops which provide a signal for
stopping the vehicle are provided in the floor.
The vehicle also supports permanent magnet 31 that actuates the
monostable and bistable modules A and B and electromagnet 32 that
actuates the bistable decision point module S and sometimes A. In
addition, a sensor senses the energization of a holding coil to
stop the vehicle.
Permanent magnet 31 is mounted along the centerline of the tractor
and actuates all modules in line therewith of the A or B type.
Electromagnet 32 is mounted a predetermined set distance from the
centerline of the vehicle and actuates all modules in the floor a
set distance from the centerline of the vehicle, the modules being
of the S or A type.
As shown, the vehicle supports a program into which the operator
sets a signal determining the destination of the vehicle. Into this
program, a code sensor provides a signal depending upon the reading
from signals along the floor. Specifically, magnets embedded in
predetermined manner in predetermined locations in the floor
produce signals that are read by a code sensor and compared in the
programmer to produce a stop signal or a path control signal. The
stop signal causes the drive motor to be deenergized and the brake
to be energized. An appropriate path control signal selectively
energizes the electromagnet 32 so that the proper decision will be
made at any decision point, like diverging point II, to guide the
vehicle through the shortest path. In the event that there is a
failure of a reading signal sensing the guide path, for example,
due to deenergization of the guide path, a stop signal is provided
to the start-stop control for stopping the vehicle.
* * * * *