U.S. patent application number 15/795017 was filed with the patent office on 2019-05-02 for wireless control of tightly spaced machines.
The applicant listed for this patent is Amazon Technologies, Inc.. Invention is credited to Samuel Gardner GARRETT, Sachin Rajendra KOTHARI, Seshachalamgupta MOTAMARRI, Timothy Alan TALDA.
Application Number | 20190132769 15/795017 |
Document ID | / |
Family ID | 64110212 |
Filed Date | 2019-05-02 |
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United States Patent
Application |
20190132769 |
Kind Code |
A1 |
KOTHARI; Sachin Rajendra ;
et al. |
May 2, 2019 |
WIRELESS CONTROL OF TIGHTLY SPACED MACHINES
Abstract
Embodiments herein describe wireless transmission techniques for
mitigating interference between wirelessly controlled machines in a
shared space. To mitigate interference, the machines may be
assigned different channels within the same frequency band.
However, if machines using the same channel in a frequency band
receive each other's wireless signals, the wireless signals can
interfere. To free up additional bandwidth, in one embodiment, the
command signals are transmitted using a different frequency band
than a heartbeat signal used to stop the machines in case of
emergencies. In another embodiment, time multiplexing or
directional antennas can be used to mitigate interference. In
another example, antenna diversity and multiple-input-multiple
output (MIMO) can be used to further focus the radiation pattern
onto the desired machine while avoiding transmitting wireless
signals to neighboring machines. In one embodiment, the machines
may use dual-channels to transmit and receive duplicate data.
Inventors: |
KOTHARI; Sachin Rajendra;
(Issaquah, WA) ; GARRETT; Samuel Gardner;
(Seattle, WA) ; MOTAMARRI; Seshachalamgupta;
(Redmond, WA) ; TALDA; Timothy Alan; (Seattle,
WA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Amazon Technologies, Inc. |
Seattle |
WA |
US |
|
|
Family ID: |
64110212 |
Appl. No.: |
15/795017 |
Filed: |
October 26, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B25J 9/1674 20130101;
H04B 7/0697 20130101; G06Q 10/0834 20130101; H04B 7/024 20130101;
H04L 43/10 20130101; H04W 72/0453 20130101; B25J 13/006 20130101;
E02F 9/205 20130101; H04W 74/0841 20130101; G06Q 50/28 20130101;
B60L 3/04 20130101; G05B 19/048 20130101; H04B 7/0452 20130101;
H04B 7/026 20130101; H04W 16/28 20130101; H04B 7/0617 20130101;
H04B 7/2618 20130101; H04Q 11/04 20130101; H04W 72/046 20130101;
B25J 13/065 20130101; H04J 3/1682 20130101; G05B 19/18 20130101;
H04B 7/0669 20130101; Y10S 901/01 20130101; H04W 28/04
20130101 |
International
Class: |
H04W 28/04 20060101
H04W028/04; H04L 12/26 20060101 H04L012/26 |
Claims
1. A system comprising: a first machine comprising a first
plurality of wirelessly controlled robots; a second machine
comprising a second plurality of wirelessly controlled robots; a
first controller configured to transmit first commands to the first
plurality of robots using a first antenna; a second controller
configured to transmit second commands to the second plurality of
robots using a second antenna, wherein the first machine is within
a radiation pattern of the second antenna and the second machine is
within a radiation pattern of the first antenna; a third antenna
configured to transmit a first heartbeat signal to the first
plurality of robots; and a fourth antenna configured to transmit a
second heartbeat signal to the second plurality of robots, wherein
the first and second pluralities of robots perform the first and
second commands, respectively, so long as the first and second
heartbeat signals are received, and wherein the first and second
commands are transmitted on a first frequency band and the first
and second heartbeat signals are transmitted on a second frequency
band different from the first frequency band.
2. The system of claim 1, wherein the first controller is
configured to transmit the first commands using a first channel in
the first frequency band and the second controller is configured to
transmit the second commands using a second channel in the first
frequency band different from the first channel.
3. The system of claim 1, wherein first controller is configured to
transmit the first commands during a first timeslot during which
the second controller is not transmitting the second commands to
the second machine and the second controller is configured to
transmit the second commands during a second timeslot during which
the first controller is not transmitting the first commands to the
first machine.
4. The system of claim 3, wherein, during the first timeslot, the
first controller is configured to transmit the first commands using
a first channel in the first frequency band and, during the second
timeslot, the second controller is configured to transmit the
second commands using the first channel.
5. The system of claim 1, wherein the first controller is
configured to use a first plurality of antennas that includes the
first antenna to transmit the first commands to the first plurality
of robots using multiple input, multiple output (MIMO), wherein the
second controller is configured to use a second plurality of
antennas that includes the second antenna to transmit the second
commands to the second plurality of robots using MIMO.
6. The system of claim 1, wherein the first controller is
configured to use a first plurality of repeaters that includes the
first antenna to transmit the first commands to the first plurality
of robots, wherein the first plurality of repeaters is disposed at
different locations along a length of the first machine, wherein
the second controller is configured to use a second plurality of
repeaters that includes the second antenna to transmit the second
commands to the second plurality of robots, wherein the second
plurality of repeaters is disposed at different locations along a
length of the second machine.
7. A system, comprising: a first wirelessly controlled machine
comprising at least one receive antenna; and a control system
comprising at least one transmit antenna, wherein the control
system is configured to: wirelessly transmit first commands to the
first machine using a first frequency band, and wirelessly transmit
a first heartbeat signal to the first machine using a second
frequency band, wherein the first machine performs the first
commands so long as the first heartbeat signal is received.
8. The system of claim 7, wherein the control system is configured
to: transmit the first commands during a first timeslot and not
transmit the first commands during a second timeslot; and transmit
the first heartbeat signal during both the first and second
timeslots.
9. The system of claim 7, further comprising: a second wirelessly
controlled machine disposed in a shared space with the first
machine, wherein at least one of the first commands and the first
heartbeat signal reach a receive antenna in the second machine,
wherein the control system is configured to wirelessly transmit
second commands to the receive antenna of the second machine using
a first channel in the first frequency band, wherein the first
commands are transmitted to the first machine using a second
channel in the first frequency band.
10. The system of claim 7, further comprising: a plurality of
transmit antennas comprising the at least one transmit antenna,
wherein the control system is configured to, using the plurality of
transmit antennas, transmit the first commands to the first machine
using MIMO.
11. The system of claim 7, further comprising: a first plurality of
repeaters comprising the at least one transmit antenna that is
disposed at different locations along a length of the first
machine, wherein the control system is configured to transmit the
first commands to the first machine using the first plurality of
repeaters, wherein the plurality of repeaters use a same channel in
the first frequency band to transmit the first commands.
12. The system of claim 7, further comprising: a second wirelessly
controlled machine disposed in a shared space with the first
machine; and a third wirelessly controlled machine disposed in the
shared space, wherein the third machine is spaced a greater
distance from the first machine than the second machine in the
shared space, wherein the control system is configured to
wirelessly transmit the first commands to the first machine using a
first channel in the first frequency band, wirelessly transmit
second commands to the second machine using a second channel in the
first frequency band, and wirelessly transmit third commands to the
third machine using the first channel in the first frequency
band.
13. The system of claim 7, wherein the transmit antenna is a
directional antenna arranged to point a main lobe of a radiation
pattern along a length of the first machine and point a null of the
radiation pattern towards a second wirelessly controlled machine
disposed in a shared space with the first machine.
14. A method, comprising: wirelessly transmitting first commands to
a first wirelessly controlled machine using a first frequency band,
wherein the first wirelessly controlled machine comprises at least
one receive antenna; and wirelessly transmitting a first heartbeat
signal to the first machine using a second frequency band, wherein
the first machine performs the first commands so long as the first
heartbeat signal is received.
15. The method of claim 14, further comprising: transmitting the
first commands during a first timeslot and not transmitting the
first commands during a second timeslot; and transmitting the first
heartbeat signal during both the first and second timeslots.
16. The method of claim 14, further comprising: wirelessly
transmitting second commands to a receive antenna of a second
wirelessly controller machine using a first channel in the first
frequency band, wherein the first commands are transmitted to the
first machine using a second channel in the first frequency band,
and wherein at least one of the first commands and the first
heartbeat signal reach the receive antenna in the second
machine.
17. The method of claim 14, wherein transmitting the first commands
to the first machine comprises: transmitting the first commands to
the first machine using a plurality of transmit antennas and
MIMO.
18. The method of claim 14, wherein transmitting the first commands
to the first machine comprises: transmitting the first commands
using a plurality of repeaters disposed at different locations
along a length of the first machine, wherein the plurality of
repeaters use a same channel in the first frequency band to
transmit the first commands.
19. The method of claim 14, further comprising: wirelessly
transmitting the first commands to the first machine using a first
channel in the first frequency band; wirelessly transmitting second
commands to a second wirelessly controlled machine using a second
channel in the first frequency band; and wirelessly transmitting
third commands to a third wirelessly controlled machine using the
first channel in the first frequency band, wherein the third
machine is spaced a greater distance from the first machine than
the second machine in a shared space.
20. The method of claim 14, wherein a transmit antenna used to
transmit the first commands is a directional antenna arranged to
point a main lobe of a radiation pattern along a length of the
first machine and point a null of the radiation pattern towards a
second wirelessly controlled machine disposed in a shared space
with the first machine.
Description
BACKGROUND
[0001] Automation relies on machines to perform tasks such as
transporting items between locations in a warehouse, assembling or
manufacturing products, sorting items, packaging items, removing
items from packaging, and the like. The machines may be controlled
using wireless signals from a controller. Bandwidth becomes limited
as more and more machines which rely on wireless control are spaced
closer together. For example, to reduce the amount of occupied
floor space (e.g., the footprint), a manufacturer or distributor
may space the wirelessly controlled machines such that the wireless
signals transmitted for controlling one machine can interfere with
the wireless signals transmitted to another, neighboring
machine.
[0002] To mitigate interference, the wireless signals transmitted
to one machine may use a different wavelength (or range of
wavelengths) than the wireless signals transmitted to another
machine. In this manner, the machines can be allocated different
portions of the bandwidth using non-interfering wireless signals.
However, as the density of machines increases, the amount of
bandwidth (e.g., the available wavelengths) becomes limited.
Because of bandwidth constraints, the same wavelengths may be used
to transmit controls to two different machines. If the signals
transmitted to one of the machines reach the other machine, the
signals can cause interference which prevents that machine from
reliable receiving the wireless signals intended for it.
BRIEF DESCRIPTION OF DRAWINGS
[0003] Various embodiments in accordance with the present
disclosure will be described with reference to the drawings, where
like designations denote like elements.
[0004] FIG. 1 illustrates an item-sortation machine, according to
various embodiments.
[0005] FIG. 2 is a flowchart for controlling robots in a machine
using a heartbeat signal and wireless instructions, according to
various embodiments.
[0006] FIG. 3 illustrates using multiple wireless frequency bands
and multiple channels to mitigate interference between tightly
spaced machines, according to various embodiments.
[0007] FIGS. 4A and 4B illustrate using time multiplexing to
mitigate interference between tightly spaced machines, according to
various embodiments.
[0008] FIG. 5 illustrates changing assigned channels between
neighboring machines, according to various embodiments.
[0009] FIG. 6 illustrates using multiple antennas to mitigate
interference between tightly spaced machines, according to various
embodiments.
[0010] FIG. 7 illustrates assigning multiple repeaters with limited
range to mitigate interference between tightly spaced machines,
according to various embodiments.
[0011] FIGS. 8 and 9 illustrate transmitting duplicate data on
multiple channels to tightly spaced machines, according to various
embodiments.
[0012] FIG. 10 is a flowchart for transmitting command and
heartbeat signals on different frequency bands, according to
various embodiments.
[0013] FIG. 11 is a flowchart for transmitting duplicate data using
two channels in the same frequency band, according to various
embodiments.
[0014] FIGS. 12 and 13 illustrate an apparatus for sorting items,
according to various embodiments.
DETAILED DESCRIPTION
[0015] Embodiments herein describe wireless transmission techniques
for mitigating interference between wirelessly controlled machines
in a shared space--e.g., a warehouse or plant. As the density of
the machines increases, the demand for bandwidth may also increase.
For example, many wireless communication standards--e.g., IEEE
802.11a/b/g/n/ac/ad--provide different channels for allocating
bandwidth within their defined frequency band (e.g., 2.4 GHz, 5
GHz, or 60 GHz). That is, the different channels may correspond to
a different wavelength or range of wavelengths in the frequency
band. For example, each channel in the 2.4 GHz frequency band is 20
MHz wide. Machines that use different channels in the frequency
band can generally communicate without interfering with each other
(although some portions of the channels may be overlapping).
However, wireless signals in the 2.4 GHz and 5 GHz frequency bands
can travel up to 100 feet. Moreover, different machines may require
multiple channels to operate. If the channels have to be re-used
(e.g., different machines use the same channels to communicate) and
the machines are not spread far enough apart, then the wireless
signals can interfere with each other and prevent the corresponding
machines from reliably receiving the signals. However, spreading
out the machines to prevent interference means that more floor
space (e.g., a bigger footprint) is required to operate the
machines which may increase costs. The wireless techniques
described herein permit the machine density to be increased while
mitigating the likelihood the wireless signals intended for one
machine interfere with another machine.
[0016] Many machines use a heartbeat signal (e.g., a continuous
signal) as an emergency stop (E-stop) signal to stop the machines
in case of an emergency. The heartbeat signal also requires
bandwidth in the frequency band (although the bandwidth may be
smaller than the bandwidth use to transmit operational commands to
the machines). In one embodiment, the heartbeat signal is assigned
to a first frequency band while the operational commands are
assigned to a second frequency band. For example, the heartbeat
signal may be assigned to the 2.4 GHz band while the operational
commands are transmitted on the 5 GHz band (or vice versa). To
mitigate interference between neighboring machines, the machines
may be assigned different channels within the same frequency band.
For example, Machine A is assigned Channel 1, Machine B is assigned
Channel 2, and so forth. However, there are a limited number of
channels in each frequency band and some machines may require
multiple channels further restricting the bandwidth. Thus, the
channels may have to be reused which can result in interference if
the machines are within wireless range of each other. For example,
wireless signals for IEEE 802.11a/b/g/n/ac have a range up to
approximately 100 feet. If machines using the same channel in one
of these IEEE frequency bands are within 100 feet of each other,
the wireless signals can interfere.
[0017] In one embodiment, time multiplexing is used to mitigate
interference. The machines can all use the same channel (or
channels) but at different times. For example, Machine A may use
the channel during a first time slot, Machine B uses the channel
during a second time slot, Machine C during a third time slot, and
so forth. Because only one machine is using the channel at a time,
the signals cannot interfere. However, this reduces the amount of
data that can be transmitted to the machines since they
receive/transmit signal only during their time slot. However,
multiple channels in the 2.4 of 5 GHz bands could be used to send
data which can increase the bandwidth, or the machines may use a
higher bandwidth frequency band such as IEEE 802.11ad which has a
60 GHz frequency band.
[0018] In one embodiment, a directional antenna can be used to
mitigate interference between machines. The directional antenna can
be positioned to focus the wireless signals (i.e., the antenna's
radiation pattern) into an area that includes only one machine
which may mitigate the amount of wireless signals that propagate in
a direction away from the machine. As such, the machines can be
spaced closer or permit the machines to use the same channels to
transmit data with little or no interference. In another example,
antenna diversity and multiple-input-multiple output (MIMO) can be
used to further focus the radiation pattern onto the desired
machine while not transmitting wireless signals to neighboring
machines.
[0019] In one embodiment, the machines may use dual-channels to
transmit and receive data. That is, a controller may transmit the
same data using two channels in the same frequency band to the
machine. Even if a neighboring machine is using the same channels
at the same time, the likelihood the wireless signals for a
neighboring machine will interfere with both channels is low. To
further decrease the risk of interference, antenna diversity and
MIMO can be used to reduce the likelihood the wireless signals
propagate between neighboring machines.
[0020] FIG. 1 illustrates an item-sortation machine 100, according
to various embodiments. Generally, the machine 100 sorts received
items 125 into containers 180 using wirelessly controlled robots
140. However, the wireless communication techniques described
herein are not limited to such and can be used in any wireless
controlled machine (or robot(s)) such as a machine for moving
containers or racks in a warehouse, removing an item from a
package, packing an item into a shipping container, picking an
item, and the like. The embodiments herein can be used in any
machine that relies on wireless control signals which can interfere
with other wireless controlled machines in a shared area (e.g., a
warehouse, sorting facility, mail processing facility, packing
facility, etc.).
[0021] The sortation machine 100 includes a master control system
105, a feeder 130, a robot area 135, and a distribution system 170.
The master control system 105 provides the wireless control signals
using a master controller 110 and antenna 120 (e.g., a transmit
antenna) which control the actions of the robots 140 in the robot
area 135. For example, the master control system 105 may wirelessly
send move commands, pick-up commands, drop commands, stop commands,
and the like which control how the robots 140 move themselves, and
the item 125, in the robot area 135. The master control system 105
also includes a heartbeat controller 115 which uses the antennas
120 to transmit a wireless heartbeat (or E-stop) signal to the
robots 140. In one embodiment, the robots 140 perform the commands
received from the master controller 110 only as long as the
heartbeat signal is received. That is, if the heartbeat controller
115 stops sending the heartbeat signal, the robots immediately stop
(e.g., within a few millisecond) their current task. In one
embodiment, the heartbeat signal is used to stop the robots 140 in
the case of an emergency or a malfunction. Because the robots 140
could hurt a human near the machine 100 or damage the machine 100
during a malfunction, once an emergency is detected, the heartbeat
controller 115 can deactivate the heartbeat signal which
immediately stops the robots 140 to prevent harm to a human
operator or the machine 100 itself. The heartbeat controller 115
may deactivate the heartbeat signal in response to a human operator
pressing an emergency button, detecting a malfunctioning robot 140,
sensor information (e.g., a vibration sensor), and the like. Once
the emergency is handled, the heartbeat controller 115 can resume
transmitting the heartbeat signal which indicates to the robots 140
they can begin to perform the commands received from the master
controller 110.
[0022] In one embodiment, the master controller 110 and the
heartbeat controller 115 include processors or micro-controllers.
The master controller 110 and the heartbeat controller 115 can
include solely hardware and firmware or can include combinations of
hardware and software elements. Although not shown, the control
system 105 can include master controllers 110 for multiple
different machines 100. For example, the control system 105 can
refer to multiple independently operating master controllers 110
for controlling respective machines 100, synchronized master
controllers 110, or a single master controller 110 which controls
multiple different machines 100.
[0023] The feeder 130 is a structure that moves the item 125 into
the robot area 135. For example, the robot area 135 may be an
enclosure that establishes an area where the robots 140 move. The
feeder 130 may be a chute which slides the item 125 into a
receiving area in the robot area 135, a conveyor belt which moves
the packages into the area 135, or a container in which a human
places the items 125. In any case, the robots 140 can retrieve the
item 125 once the item 125 arrives in the robot area 135 and use
the commands received from the master control system 105 to move
the item to the distribution system 170 where the item is stored in
one of the containers 180.
[0024] The machine 100 can include any number of robots 140, e.g.,
one, two, three, four, etc. As shown, each robot 140 includes a
transport device 145, a movement system 150, a power source 155, a
controller 160, and at least one antenna 165. The transport device
145 permits the robot 140 to carry the item 125 to different
locations in the robot area 135. For example, the robot area 135
may be a fenced off enclosure on the warehouse floor or a frame
which includes tracks which the robots 140 can follow. The robots
140 can move along the floor and/or vertically using the frame. In
another example, a portion of the robots 140 (or the entire robot)
may remain stationary in the robot area 135. For instance, the base
of the robot 140 may be anchored while an extension of the robot
(e.g., a robotic arm) can move to pick up the items 125 and move
them to different locations. The transport device 145 may include a
claw or suction cup for lifting or picking the item 125. In another
example, the transport device 145 may be a conveyor that receives
the item 125 from a conveyor belt in the feeder 130. In another
embodiment, the transport device 145 may be a bin in which the
feeder 130 places the item 125.
[0025] The movement system 150 may move the entire robot 140 or a
portion of the robot 140 within the robot area 135. For example,
the movement system 150 may include wheels or bearings which permit
the robot 140 to move along the floor or along tracks. In another
example, the movement system 150 includes an arm attached to the
transport device 145 to move the item 125. For example, the robot
area 135 may include a central conveyor belt that moves received
items 125 past the robots 140. The master controller 110 can
instruct a selected one of the robots 140 to pick up the item 125
as it passes using the movement system 150 and the transport device
145 to place the item 125 into the distribution system 170.
[0026] The power source 155 in the robots 140 can be a battery or a
capacitor. For example, the robots 140 may move relative short
distances (e.g., less than 50 feet) before they return to recharge.
In that case, the charge on a large capacitor (or capacitors) can
be sufficient to move the robot 140 before the robot 140 returns to
a charging station or rail to recharge the capacitor. The advantage
of using a capacitor as the power source 155 is that it can provide
high currents and recharge in a shorter time than a battery,
although either is acceptable. In another example, if the entire
robot 140 does not move within the robot area 135, then the robot
can be connected to a power grid (e.g., plugged into a power
outlet) where the power source 155 can be a power converter.
[0027] The controller 160 can be a processor or a micro-controller
which receives commands from the master controller 110 using the
antenna 165 and issues corresponding commands to the transport
device 145 and movement system 150. For example, if the master
controller 110 instructs the robot 140 to move the item 125 to a
particular location in the robot area 135, the controller 160 in
turn issues one or more commands to the movement system 150 to move
the robot to the desired location. In one embodiment, in addition
to receiving information from the master controller 110, the
controller 160 can transmit information to the master controller
110. For example, the controller 160 may use the antenna 165 to
inform the master controller 110 when a command has been completed
successfully. The controller 160 may send other information
wirelessly to the master controller 110 such as the charge on the
power source 155, status of the transport device 145 or movement
system 150 (if there is a malfunction or needs repair), if the item
125 was dropped, and the like. In one embodiment, the controller
110 may be entirely hardware, but in other embodiments may include
a combination of hardware/firmware and software.
[0028] In one embodiment, the distribution system 170 receives the
item 125 from the robot 140 and places the item 125 in one of the
containers 180. The distribution system 170 may be multiple access
apertures (e.g., a filing system) with corresponding chutes that
lead to the containers 180. Using the transport devices 145, the
robots 140 can move the items 125 through the apertures in the
distribution system 170 and into the containers 180. In another
example, the distribution system 170 may include fasteners or
platforms for coupling the containers 180 to the distribution
system 170. For instance, distribution system may form a rack on
which the containers 180 are mounted. The robots 140 can travel to
the portion of the rack that stores the corresponding container 180
for the package and place the item 125 into the container 180.
[0029] In one embodiment, the containers 180 are assigned different
destinations either within the warehouse or to an external location
(e.g., a different warehouse or mailing code). Moreover, the
containers 180 may correspond to different shipping companies. In
one embodiment, the master controller 110 knows the desired
destination of the items 125, which may be determined by scanning a
bar code or reading an RFID tag on the item 125 when in the feeder
130. The master controller 110 can then provide instructions to the
robots 140 to move the item 125 to the appropriate location in
distribution system 170 such that the item 125 is stowed in the
container 180 corresponding to its destination. In this manner, the
item-sortation machine 100 can provide wireless commands to the
robots 140 for sorting received items 125 into the containers
180.
[0030] FIG. 2 is a flowchart of a method 200 for controlling robots
in a machine using a heartbeat signal and wireless commands,
according to various embodiments. For ease of explanation, the
method 200 describes controlling the robots 140 in the
item-sortation machine 100 shown in FIG. 1. However, the method 200
can be used to control any kind of wireless controlled machine such
as a single robot or a cluster of robots.
[0031] At block 205, the master controller determines instructions
for a robot to move an item to a desired location. For example, the
master controller may instruct the robot to pick up an item, move
the item (or itself) to a different location, drop of the item,
transfer the item to another robot, and the like. As used herein,
the wireless command can include any command sent from the master
controller to the robot to control the actions of the robot.
[0032] At block 210, the master controller wirelessly transmits the
instruction to the robot. The master controller may transmit the
instruction to a transmitter in the control system which uses on or
more antennas to transmit commands to receivers in the robots. The
transmitter in the control system can use various wireless
transmission algorithms such as antenna diversity and MIMO to
mitigate interference between neighboring machines.
[0033] At block 215, the heartbeat controller determines whether an
E-stop has been triggered. For example, the machine (or the
surrounding area) may include emergency stop buttons that can be
pressed by a human operator in case of an emergency or malfunction.
For example, if the operator needs to retrieve a dropped package or
notices a malfunctioning robot, the operation can press the
emergency button which triggers the E-stop. In another embodiment,
the heartbeat controller triggers the E-stop without human input.
The heartbeat controller may monitor sensors in the machine or
receive periodic or emergency status updates for the robots. Using
this information, the heartbeat controller can determine to trigger
the E-stop.
[0034] If the E-stop is triggered, the method 200 proceeds to block
220 where the heartbeat controller ceases transmitting the
heartbeat signal. In one embodiment, the heartbeat signal is a
continuous signal with a predictable pattern such as a sine wave, a
square wave, or a periodic pulse. In one example, the robots 140
may not receive commands using the heartbeat signal but rather
monitor the signal to make sure they can continue to operate.
Stated differently, the heartbeat signal may not transmit digital
data to the robots but instead provides a deactivation signal for
stopping the robots. As such, when the heartbeat controller stops
transmitting the heartbeat signal at block 220, the controller in
the robot may immediately stop the robot from moving (if currently
moving) and prevent the robot from carrying out any commands that
may be received from the master controller. In one embodiment, the
controller in the robot may put the robots in a passive state so
that the robots can be easily moved by the operator (in case the
robot has malfunctioned or needs to be moved to address a safety
concern or to retrieve a fallen item).
[0035] To improve safety, it may be desired that robots stop
immediately when the heartbeat signal stops (e.g., less than a
second and preferably less than a few milliseconds). As such, the
embodiments herein describe techniques for mitigate interference
that may occur from wireless signals transmitted by neighboring
machines in a shared area. For example, separate heartbeat signals
may be transmitted to neighboring machines. If those heartbeat
signals reach both machines, then they can interfere with each
other such that the robots may incorrectly determine that the
heartbeat signal has ceased and stop its current action.
Alternatively, if the E-stop is triggered for one of the machines,
the robots in that machine may still receive the heartbeat signal
intended for a neighboring machine and continue to operate which
can lead to an unsafe situation.
[0036] If at block 225 the heartbeat controller determines the
problem which triggered the E-stop is resolved, the method proceeds
to block 230 where the heartbeat controller resumes transmitting
the heartbeat signal and the master controller can resume normal
control and operation of the robots in the machine. However, if the
problem has not been resolved, the absence of the heartbeat signal
keeps the machine in a shutdown state.
[0037] Returning to block 215, if the E-stop has not been
triggered, the robot performs the command so long as the heartbeat
signal is received. That is, in addition to checking that the
heartbeat signal is active when a new command is received at the
robot, the controller in the robot may continue to perform the
action or actions indicated in the command only as long as the
heartbeat signal remains active. For example, the controller may
have a separate detection system which continually monitors the
heartbeat signal to detect when the signal stops. In response, the
detection system transmits an interrupt or override signal which
stops the other functions in the controller. So long as the
heartbeat signal remains active, the method 200 can repeat with the
robots in the machine receiving new instructions or commands from
the master controller and performing those commands.
[0038] FIG. 3 illustrates using multiple wireless frequency bands
and multiple channels to mitigate interference between tightly
spaced machines, according to various embodiments. Specifically,
FIG. 3 illustrates a top view of a shared space 300 (e.g., floor
space in a warehouse, fabrication plant, assembly plant, sort
center, etc.) that includes a plurality of machines 100 which are
spaced a distance (d) apart. Each of the machines 100A-D
corresponds to an antenna 120A-D used by respective master
controllers (not shown) for transmitting commands to the machines
100. The machines 100 may include one or more robots (not shown)
which then receive the commands to perform corresponding
actions.
[0039] Each of the antennas 120 have a corresponding radiation
pattern 305 which graphically represent the distance the wireless
signals travel within the shared space 300. For the 2.4 GHz
frequency band which is defined by IEEE 802.11b/g/n standards and
the 5 GHz frequency band which is defined by IEEE 802.11a/h/j/n/ac
standards, the signals may propagate up to 100 feet. Thus, given
the circular radiation pattern shown in FIG. 3 (as viewed from the
top), the wireless signals transmitted by the antennas 120 may
reach neighboring machines that are within 100 feet. Here, the
distance (d) is less than 100 feet such that the radiation patterns
305 overlap at least one, if not two or more of the neighboring
machines 100.
[0040] To prevent or mitigate interference between the machines, in
this embodiment, the heartbeat signals are assigned to a different
frequency band than the command signals. For example, the heartbeat
signal may be transmitted on the 2.4 GHz frequency band while the
command signals used to control the machines 100 are transmitted on
the 5 GHz frequency band (or vice versa). In this manner,
interference between the heartbeat signal and the command signals
are mitigated. However, as shown by the radiation pattern 305A, the
heartbeat or commands signals transmitted by the antenna 120A can
reach the machine 100B which means the wireless signals for
controlling the machine 100A can cause interference at the machine
100B. To mitigate this intra-band interference, the wireless
signals can be assigned to different channels within the frequency
band. For example, the command signals transmitted to machine 100A
use Channel 1 in Frequency Band 1, the command signals transmitted
to machine 100B use Channel 2 in Frequency Band 1, the command
signals transmitted to machine 100C use Channel 3 in Frequency Band
1, and so forth. Similarly, the heartbeat signals transmitted to
machine 100A can use Channel 1 in Frequency Band 2, the heartbeat
signals transmitted to machine 100B use Channel 2 in Frequency Band
2, the heartbeat signals transmitted to machine 100C use Channel 3
in Frequency Band 2, and so forth. In this manner the command
signals are allocated different portions of the bandwidth in
Frequency Band 1 while the heartbeat signals are allocated
different portions of the bandwidth in Frequency Band 2. The
antennas 120 assigned to transmit the command and heartbeat signals
for the machines 100A-D can transmit these signals in parallel with
little or no interference despite the overlapping radiation
patterns 305.
[0041] In one embodiment, the heartbeat signal is assigned to use
the frequency band that has the least amount of bandwidth between
the two frequency bands (e.g., the fewest number of channels). That
is, because the heartbeat signal may not transmit data but rather a
continuous signal, it may have more flexible bandwidth requirements
than the command signals, and use less bandwidth. Moreover, instead
of assigning a separate channel for each machine 100 for the
heartbeat signal, multiple machines 100 may use the same heartbeat
signal. For example, if there are not enough channels in the
frequency band for each machine 100 to have its own channel for
transmitting the heartbeat signal, multiple machines may use the
same channel to receive the heartbeat. Thus, if any one of the
machines in the group trigger an E-stop, all of the machines 100 in
the group stop. Stopping all the machines in the group may be
acceptable so that a machine does not continue to operate even
though an E-stop was triggered because a neighboring machine 100
within wireless range uses the same channel to transmit its
heartbeat signal. By grouping the machines to use the same
heartbeat signal so that the channels are not reused by different
heartbeat controllers, the operator can ensure that a machine
(which triggered an E-stop) does not inadvertently receive a
heartbeat signal on the same channel intended for a different
machine.
[0042] If the distances (d) between the machines 100 shrinks and
additional machines 100 are added to the shared space, there may
not be enough pre-defined channels in the frequency bands to assign
unique channels to each of the machines as shown in FIG. 3.
Alternatively, the bandwidth of a single channel may not be
sufficient to provide data to the robots in each of the machines
100. For example, using a single channel may be sufficient to
transmit the command signals if each of the machines 100 has less
than five robots, but if the machines 100 have more than five
robots than at least two channels are used, and if the machines 100
have more than ten robots, at least three channels are used. As
such, multiple channels may be assigned to each of the machines 100
to transmit the command signals. In either case, the frequency
bands may not have a sufficient number of channels to assign all
the machines 100 within the radiation patterns 305 of each of the
machines 100 a unique channel (or channels). For example, if a
frequency band has only twenty channels but there are twenty other
machines 100 within the radiation pattern 305A of the antenna 120A
for the machine 100A, then the human operator may have to use the
same channel assigned to the machine 100A to one of the other
machines within the radiation pattern 305A which can cause
interference. Thus, the embodiments described in FIG. 3 can be
combined with other embodiments described below (or other
embodiments may be used instead of what is shown in FIG. 3) to
mitigate interference when the machine density increases or when
there is no more available bandwidth (e.g., all the channels in the
frequency bands have been used).
[0043] FIGS. 4A and 4B illustrate using time multiplexing to
mitigate interference between tightly spaced machines, according to
various embodiments. FIG. 4A illustrates the shared space 300 that
includes the machines 100 but uses time multiplexing to mitigate
interference. For example, the embodiments in FIG. 4A may be used
if the machine density or bandwidth requirements in the shared
space 300 does not permit using the wireless strategy shown in FIG.
3. In FIGS. 4A and 4B, each of the machines 100 is assigned a
respective timeslot or time slice to perform wireless communication
during which time the antennas 120 for the other neighboring
machines 100 are not transmitting wireless signals.
[0044] In FIG. 4A, the antenna 120A transmits wireless signals
while the antennas 120 for the other wireless machines (i.e.,
machines 100B-D) are unused. For example, the antenna 120A may
transmit command signals on Channel 1 of Frequency Band 1 without
having to worry about interference from the neighboring machines
100. Moreover, although FIG. 4A illustrates assigning only one
channel, in other embodiments multiple channels can be used by the
machines 100 during their respective timeslots. For example, each
of the machines 100 may use Channels 1-10 during their timeslot to
transmit command signals. Thus, even though the machines cannot
transmit command signals continuously, they can use multiple
channels to transmit more commands than could be transmitted if
only one channel is used. For example, when not transmitting, the
master controllers for the machines 100 may queue the commands for
the machine and then transmit the queued commands during the next
timeslot.
[0045] In one embodiment, the heartbeat signal is time multiplexed
in the same manner as shown in FIGS. 4A and 4B; however, this means
the machines 100 can perform the commands only during their
timeslot. Instead, the heartbeat controller may continuously
transmit the heartbeat signal so that the machines 100 can operate
continuously. For example, even though in FIG. 4A only the antenna
120A is transmitting commands to the machine 100, the other
machines 100 can nonetheless be operating using commands that were
received previously. For example, in a previously time slot, the
master controller for the machine 100B may have instructed a robot
to move four centimeters or to activate its conveyor belt to pick
up an item. Because it may take the robot several seconds to
complete this command, so long as the heartbeat signal is still
being received, the controller in the robot can issue instructions
to perform this command even if the robot is not currently
wirelessly communicating with the master controller. Because the
heartbeat signal may require less bandwidth than the command
signals, there may be sufficient available bandwidth to permit each
machine 100 to have its own channel for the heartbeat signals (or
share the same channel) so that the heartbeat signals can be
transmitted continuously.
[0046] In FIG. 4B, the antenna 120A has ceased transmitting the
command signals (e.g., its timeslot has ended) and the antenna 120B
begins transmitting during the timeslot assigned to the machine
100B (i.e., Timeslot 2). Again, if the heartbeat signal is
transmitted continuously for all the machines 100, the robots in
the machine 100A can continue to operate to perform the commands
received during Timeslot 1. In this manner, each of the machines
can transmit command signal during respective timeslot using the
same channels without interference.
[0047] In one embodiment, multiple antennas may transmit command
signals simultaneously in the shared space 300. For example, each
machine 100 may not use all the channels to transmit data during
its timeslot. As such, a neighboring machine may use the remaining
channel to transmit data during the same timeslot. For example, the
machine 100A may use Channels 1-5 during Timeslot 1 to transmit
command signals in parallel with the machine 100D using Channels
6-10 to transmit command signals. Because the machines 100 use
different channels, there is little or no interference. Of course,
if two machines are sufficient far away in the shared space 300
such that the signals transmitted by one machine cannot interfere
with the signals received by the other machine, then both machines
can transmit command signals using the same channel or channels.
The operator may identify which machines 100 in the shared space
300 are sufficiently far away from a selected machine (e.g.,
machine 100A or 100B) such that there is no interference, and then
determine which machines can use the same timeslot to transmit
wireless signals using the same channel as the selected
machine.
[0048] In one embodiment, the master controllers for each of the
machines 100 are synchronized so that each controller knows when to
transmit the command signals. For example, the master controllers
for the machines 100A-D may share the same clock signal or
periodically transmit synchronization signals to each other to
ensure that two of the antennas 120 are not transmitting on the
same channel in parallel. For example, once the machine 100A
determines its timeslot has expired, it can notify the master
controller for the machine 100B to begin its timeslot. In another
embodiment, instead of having separate master controllers for each
machine 100, there is one master controller for all the machines
100 which can manage the timeslots for the machines 100.
[0049] FIG. 5 illustrates changing assigned channels between
neighboring machines 100, according to various embodiments. As
shown, FIG. 5 illustrates a shared space 500 that includes the
machines 100A-D that each have a respective a directional antenna
510A-D. Instead of omnidirectional antennas 120 as shown in FIGS. 3
and 4A-4B, the directional antennas 510 have directional radiation
patterns 505. In this example, the radiation patterns 505 include
at least one main lobe which covers a respective machine 100. The
main lobes taper as they approach neighboring machines 100 which
reduces the likelihood that, for example, the wireless command
signals transmitted by the directional antenna 510A interfere with
the receivers in the machine 100B. That is, the directional
antennas 510 may be configured or arranged in the shared space 500
such that neighboring machines are in nulls for the radiation
patterns 505 to reduce interference.
[0050] In FIG. 5, the directional antennas 510 transmit wireless
command signals simultaneously to the machines 100. That is, in one
embodiment, the machines 100 are not time multiplexed. A distance
d2 between a machine (e.g., the machine 100A) and its direct
neighbor (e.g., the machine 100B) may be short enough (e.g., less
than 30 feet) such that the command signals transmitted by the
antennas 510 can interfere. As such, the directly neighboring
machines 100 are assigned different channels in the frequency band.
That is, the antenna 510B uses Channel 2 but the directly
neighboring antennas 510A and 510C use Channel 1. Because the
distance d1 may be large enough (e.g., more than 30 feet) such that
the wireless signals transmitted by the antenna 510A do not
interfere with the machine 100C (or the machine 100D), the antenna
510A and 510C can use the same channel. Thus, using the directional
antennas 510 with narrowed beam patterns 505 can mean the operator
assigns two different channels (or two different groupings of
channel such as Channels 1-5 and 6-10) to directly neighboring
machines.
[0051] Of course, if the distances d1 and d2 are shrunk further,
the radiation pattern 505A may also overlap with the machine 100C
which can cause interference. As such, the machine 100C may be
assigned to communicate using Channel 3 to mitigate interference.
Moreover, the machine 100D could use Channel 1 since it may be
outside the radiation pattern 505A used by the machine 100A. In
another example, as the distance d2 increases (or the directional
antenna 510A has a sufficiently narrow radiation pattern 505A), all
of the machines 100 can use the same channel (or group of channels)
so long as the radiation patterns 505 do not overlap with the
directly neighboring machines 100.
[0052] In FIG. 5, the heartbeat signal 515 is assigned to a
different frequency band (e.g., Frequency Band 2) from the
frequency band used by the command signals. If the heartbeat signal
515 is also transmitted using a directional antenna, then the
heartbeat signals 515 can be assigned using a similar scheme as the
command signals shown in FIG. 5. For example, given the distances
d1 and d2 shown here, the heartbeat signal 515 for the machine 100A
may be transmitted on Channel 1 of the Frequency Band 2, the
heartbeat signal 515 for the machine 100B is assigned Channel 2 of
the Frequency Band 2, the heartbeat signal 515 for the machine 100C
is assigned Channel 1 of the Frequency Band 2, and so forth. As the
distances d1 and d2 vary, so can the channel assignments for the
heartbeat signal 515. In another embodiment, the heartbeat signal
515 is transmitted in the same frequency band (e.g., the Frequency
Band 1) as the command signals. For example, the heartbeat signal
may be shared by all the machines 100A-D in FIG. 5 and use Channel
3 of the Frequency Band 1, in which case the heartbeat signal may
be transmitted using an omnidirectional antenna. Or, the radiation
pattern 505 (or the distances between the machines 100) may permit
the machines 100 to use the same channel of the same frequency band
without interference from a neighboring antenna transmitting its
independent heartbeat signal 515.
[0053] FIG. 6 illustrates using multiple antennas to mitigate
interference between tightly spaced machines, according to various
embodiments. As shown, FIG. 6 illustrates a shared space 600 where
multiple antennas arranged in antenna groups 610 transmit command
signals to the machines 100. That is, instead of using one antenna
to transmit command signals to the machines using one or more
channels, each machine 100 has multiple antennas in an antenna
group 610 to transmit the data signals. The antenna groups 610 can
be assigned a single channel or multiple channels in a frequency
band.
[0054] In one embodiment, the antenna groups 610 use antenna
diversity and MIMO. Doing so provides the master controllers for
the machines 100 with more control of the radiation patterns 605
corresponding to the antenna groups 610. In one embodiment, in
addition to having multiple antennas for transmitting the command
signals, each robot in the machines 100 includes multiple receive
antennas for receiving the command signals. For example, MIMO uses
multiple transmit and receive antennas to exploit multipath
propagation in the shared space 600. Using precoding (or
beamforming), the master controller uses the antenna group 610 to
cause constructive interference of the signals emitted by the
antennas at a particular location within the machines 100. That is,
the master controller can increase the received signal at a robot
by making signals emitted from the different antennas to add up
constructively and to reduce the effect of multipath fading. Thus,
MIMO permits the master controller to further control the radiation
pattern 605 to reduce interference between the neighboring machines
100. In FIG. 6, the antenna groups 610 can all use the same channel
(or plurality of channels) to transmit commands to the machines
with little or no interference.
[0055] Using MIMO and antenna diversity can permit the machines 100
to be spaced closer together than, for example, using the
omnidirectional antennas 120 shown in FIG. 3 or the directional
antennas 510 in FIG. 5. For example, the machines 100 in FIG. 5 may
have to spread out a distance of at least 30 feet to prevent
interference if all the machines 100 are assigned the same channel.
By using antenna groups 610 and MIMO, the machines 100 in FIG. 6
may be spaced less than 30 feet apart and still use the same
channel (or same group of channels) to communicate. If the distance
between the machines 100 is reduced further, then the operator can
assign the channel like what is shown in FIG. 5 where directly
neighboring machines 100 are assigned different channels. However,
the distances between the machines 100 in FIG. 6 may be smaller
than the distances between the machines in FIG. 5 thereby
increasing the density of the machines and enable a more efficient
use of the shared space 600.
[0056] Further, the antennas in the antenna groups 610 may be
directional antennas. That is, the use of directional antennas can
be combined with antenna diversity and MIMO in order to further
reduce the radiation patterns 605 and mitigate or prevent
interference between the machines 100.
[0057] The heartbeat signal 615 may be assigned to the same
frequency band used by the command signals (e.g., Frequency Band 1)
or a different frequency band (e.g., Frequency Band 2). If the
heartbeat signal 615 is also transmitted using an antenna group
implementing antenna diversity and MIMO, then the heartbeat signals
615 can be assigned using a similar scheme as the command signals
shown in FIG. 6 where individually controllable heartbeat signals
615 are transmitted without worrying about interference. In other
embodiments, the heartbeat signal 615 is transmitted using a single
antenna (e.g., without MIMO) in which case heartbeat signal 615 may
be assigned different channels for the machines 100 to mitigate
interference, or the signal 615 may be shared by multiple machines
100 in which case the heartbeat signal 615 may be transmitted using
an omnidirectional antenna rather than a directional antenna to
increase its coverage area. As an example of the latter, the
machines 100A-D may use the same heartbeats signal 615 which may
reduce deployment cost, although this means if one of the machines
100 experiences an E-stop and the heartbeat signal 615 is not
transmitted, all the machines listening for the heartbeat signal
615 also stop.
[0058] FIG. 7 illustrates assigning multiple repeaters 710 (e.g.,
synchronized antennas to transmit the same signals on the same
channel in parallel) with limited range to mitigate interference
between tightly spaced machines 100, according to various
embodiments. FIG. 7 illustrates a shared space 700 where each
machine 100 includes multiple repeaters 710 (three repeaters 710
per machine 100 in this example, but the machines 100 could include
any number) disposed at different locations along a length of the
machines 100. In one embodiment, the repeaters 710 for the same
machine transmit the same data--e.g., command signals--on the same
channel or groups of channels. Because of the limited range of
radiation patterns 705 for the repeaters 710, the neighboring
machines 100 can use the same channel or group of channels to
transmit the command signals simultaneously in the same frequency
band. That is, the repeaters 710A-C transmit command signals to the
robots in the machine 100A at the same time the repeaters 710D-F
transmit command signals to the robots in the machine 100B on the
same channel (Channel 1).
[0059] Instead of using directional antennas, antenna diversity, or
MIMO, the radiation patterns 705 can be limited or controlled by
the transmission power of the repeaters 710 or by using a frequency
band with a limited transmission range (or a combination of both).
For example, depending on the distance between the machines 100,
the operator can reduce the transmission power of the repeaters 710
to ensure the radiation patterns 705 do not overlap a neighboring
machine 100. As the distance between the machines 100 shrink, the
operator may also reduce the transmission power to prevent
interference. However, the operator may have to install additional
repeaters 710 to cover the layout of the machines 100. For example,
after reducing the radiation patterns 705, there may be dead spots
(e.g., portions of the machine 100 that are not within any
radiation pattern 705 of a repeater 710). As a result, the operator
may need to space the repeaters 710 closer together along the
length of the machines 100 and add another repeater 710 to remove
the dead spot.
[0060] In another example, the repeaters 710 may operate in a
frequency band with a smaller range than the 2.4 GHz and 5 GHz
frequency bands. For example, the 60 GHz frequency band has a much
smaller transmission distance than the 2.4 GHz and 5 GHz frequency
bands. Thus, the repeaters 710 may transmit command signals using
the 60 GHz frequency band which enables the machines 100 to be
spaced closer together relative to using slower frequency bands.
Moreover, in addition to transmitting in a faster frequency band
(which has a shorter transmission distance), the operator can also
reduce the transmission power of the repeaters 710 to further
control the radiation patterns 705. In one embodiment, the
repeaters 710 are directional antennas rather than omnidirectional
antennas as shown in FIG. 7 and are arranged such that their
corresponding radiation patterns extend primarily along the length
of the assigned machine 100 rather than to a neighboring machine
100.
[0061] The heartbeat signal 715 may be assigned to the same
frequency band used by the command signals (e.g., Frequency Band 1)
or a different frequency band (e.g., Frequency Band 2). In one
embodiment, each machine 100 includes a second set of repeaters 710
for transmitting an individually controllable heartbeat signal 715
for each machine which generates little or no interference with
neighboring machines 100. In other embodiments, the heartbeat
signal 715 is transmitted using a single antenna (e.g., without
MIMO) in which case heartbeat signal 715 may be assigned different
channels for the machines 100 to mitigate interference, or the
signal 615 may be transmitted on the same channel and shared by
multiple machines 100.
[0062] FIG. 8 illustrates transmitting duplicate data on multiple
channels to tightly spaced machines 100, according to various
embodiments. As shown, each machine 100 in the shared space 800 has
two antennas 810 for transmitting command signals to the robots
within the machine 100. For example, the machine 100A includes the
antennas 810A and 810B which transmit the same command signals to
the robots in the machine 100A. The remaining machines 100B-D also
include a respective pair of antennas 810. In this embodiment, the
antenna 810A has a radiation pattern 805A (shown as the solid line)
for transmitting the command signals while the antenna 810B has a
radiation pattern 805B (shown as the dashed line). Although the
antennas 810A and 810B transmit the command signals at the same
time, there is little or no interference between the signals
because the antenna 810A uses Channel 1 of the Frequency Band 1
while the antenna 810B uses Channel 2 of the Frequency Band 1. The
antenna pairs for the other machines 100B-D have a similar
configuration.
[0063] Although the antenna pairs do not interfere with each other,
the transmitted signals can interfere with neighboring machines as
shown by the overlapping radiation patterns 805. That is, the
command signals transmitted by the antennas 810A and 810C on the
machines 100A and 100B may interfere since both antennas use
Channel 1 to communicate and have radiation patterns 805 that
extend to neighboring machines 100. Stated differently, the
wireless signals emitted by the antenna 810A can be received by the
robots in the machine 100B at the same time those robots are
receiving command signals transmitted by the antenna 810C. The
interference from the antenna 810A can prevent the robots in the
machine 100B from receiving the commands emitted by the antenna
810C. However, because the master controller can send identical
data (e.g., the same command signals) on both of the antennas 810C
and 810D in the machine 100B using two different channels, the
controller can reduce the likelihood that interference from a
neighboring antennas prevent the robots from receiving the
commands. In one embodiment, the distance between the machines 100
is controlled that it is unlikely that interference emitted by
neighboring antennas prevent the robots from receiving the commands
emitted by the pair of antennas for that machine 100. For example,
the IEEE 802.11ad standard permits a receiver to select the best
beam forming link from a two-channel receiver (with two antennas)
depending on which channel signal path link has better performance.
Thus, if Channel 1 is currently receiving a lot of interference,
the receiver on the robots can receive the command signals using
Channel 2. In this manner, the operator can re-use channels in
neighboring machines 100 thereby freeing up available bandwidth
while mitigating the likelihood that interference from neighboring
antennas using the same channels prevents the robots from receiving
command signals from at least one of the antennas assigned to the
machine 100.
[0064] The heartbeat signal 815 may be assigned to the same
frequency band used by the command signals (e.g., Frequency Band 1)
or a different frequency band (e.g., Frequency Band 2). In one
embodiment, each machine 100 includes a second set of antenna pairs
for transmitting an individually controllable heartbeat signal 815
for each machine which generates little or no interference with
neighboring machines 100. For example, each machine 100 may include
two antennas for transmitting the heartbeat signal 815 on Frequency
Band 2 using two different channels. The receivers in the robots
can then select which of the channels provides the best version of
the heartbeat signal. Thus, when a neighboring machine (which uses
the same two channels to transmit its heartbeat signal 815)
introduces interference on one of the channels, the receivers can
receive the heartbeat signal using the other channel. While FIG. 8
illustrates using pairs of antennas to send out duplicate command
or heartbeat signals, in other embodiments each machine may use
three, four, or more antennas for transmitting duplicate command
signals or the heartbeat signal 815 on additional channels (e.g.,
Channels 3, 4, 5, etc.) to reduce the likelihood that interference
can prevent the robots from receiving on all the channels.
[0065] FIG. 9 illustrates transmitting duplicate data on multiple
channels to tightly spaced machines, according to various
embodiments. Like in FIG. 8, each machine 100 in the shared space
900 has at least two antennas for transmitting duplicate data
(e.g., either command signals or the heartbeat signal 915) to the
robots in the machines. However, unlike in FIG. 8 where only one
antenna transmits in each channel, in FIG. 9, multiple antennas
(e.g., antenna groups 910) are assigned to each channel. That is,
the antenna group 910A uses Channel 1 to transmit command or
heartbeat signals to the robots in the machine 100A while the
antenna group 910B uses Channel 2 to transmit duplicate data to the
robots in the machine 100A. These channels are then re-used by the
neighboring machines. That is, the antenna groups 910C and 910D
which transmit duplicate data to the robots in the machine 100B
also use Channel 1 and 2, respectively. As mentioned above, the
robots can have multiple antennas for receiving the duplicate data
and select which signal has the best channel signal path link.
[0066] Moreover, because each antenna group 910 includes multiple
antennas, the groups 910 can use antenna diversity and MIMO to
reduce inter-machine interference. As shown, the radiation patterns
905 corresponding to each of the antenna groups 910 are not
omnidirectional like the radiation patterns 805 in FIG. 8. For
example, the radiation pattern 905A shown by the solid line (Which
corresponds to the antenna group 910A) and the radiation pattern
905B shown by the dashed line (which corresponds to the antenna
group 910B) have main lopes that primarily cover the machine 100A.
The radiation patterns 905A and 905B may have nulls at the
locations of the other machines 100B-D in the shared space 900
thereby further mitigating the likelihood that the wireless signals
emitted by the antennas in the shared groups 910A and 910B
interfere with neighboring machines 100. Thus, the pair of antenna
groups 910 assigned to each machine 100 can use the channels that
are also used by the antenna groups 910 in neighboring machines 100
as shown. In this manner, the available bandwidth is increased so
that the machines 100 can be tightly spaced even if the radiation
patterns 905 may overlap with, or cause interference at,
neighboring machines 100.
[0067] The heartbeat signal 915 may be assigned to the same
frequency band used by the command signals (e.g., Frequency Band 1)
or a different frequency band (e.g., Frequency Band 2). In one
embodiment, each machine 100 includes a second set or pair of
antenna groups 910 for transmitting an individually controllable
heartbeat signal 915 for each machine which generates little or no
interference with neighboring machines 100. For example, each
machine 100 may include four antennas arranged in two new antenna
groups 910 for transmitting the heartbeat signal 915 on Frequency
Band 2 using two different channels. The receivers in the robots
can then select which of the channels provides the best version of
the heartbeat signal. Thus, when a neighboring machine (which uses
the same two channels to transmit its heartbeat signal 915)
introduces interference on one of the channels, the receivers can
receive the heartbeat signal using the other channel. While FIG. 9
illustrates using two antennas in each antenna group 910 to send
out duplicate command or heartbeat signals, in other embodiments
each machine may use three, four, or more antennas per group 910
for transmitting duplicate command signals or the heartbeat signal
915 to reduce the likelihood that interference can prevent the
robots from receiving on all the channels.
[0068] Except as otherwise stated, the frequency bands discussed
above can be interchanged. For example, the frequency bands can be
the 2.4 GHz, 5 Ghz, 60 GHz, or other frequency bands. Moreover, the
selection of the frequency bands for the embodiments described
above can depend on the desired spacing or distance between the
machines. For example, as distance between the machines 100 is
reduced or available bandwidth on the 2.4 GHz or 5 GHz frequency
bands is reduced, the command signals may be transmitted using the
60 GHz frequency band while the heartbeat signal is transmitted on
a different frequency band.
[0069] FIG. 10 is a flowchart of a method 1000 for transmitting
command and heartbeat signals on different frequency bands,
according to various embodiments. At block 1005, the master
controller transmits wireless commands to a wireless controlled
machine (which may include one or more individual controlled
robots) using a first channel in a first frequency band. At block
1010, the heartbeat controller transmits the heartbeat signal using
a second frequency band. In one embodiment, blocks 1005 and 1010
occur in parallel. Further, the method 1000 may include controlling
the wireless command and heartbeat signals transmitted to
neighboring wirelessly machines to mitigate interference as
described in the embodiments above for FIGS. 3, 4A-4B, 5, 6, and
7.
[0070] At block 1015, the wirelessly controlled machine operates in
response to the received command so long as the heartbeat signal is
received. Put differently, if the heartbeat control stops
transmitting the heartbeat signal, the wireless controlled machine
stops performing the received commands. Once the heartbeat signals
resumes, the wireless controlled machine can again resume
performing the commands received from the master controller.
[0071] FIG. 11 is a flowchart of a method 1100 for transmitting
duplicate data using two channels in the same frequency band,
according to various embodiments. At block 1105, the master
controller transmits commands to a wirelessly controlled machine
using a first channel in a frequency band. At block 1110, the
master controller transmits the same commands to the wirelessly
controlled machine using a second channel in the frequency band. In
one embodiment, blocks 1005 and 1010 occur in parallel. Further,
the method 1100 may include controlling the wireless command and
heartbeat signals transmitted to neighboring wirelessly machines to
mitigate interference as described in the embodiments above for
FIGS. 8, and 9.
[0072] At block 1115, the wirelessly controlled machine selects the
commands received on the channel with the best signal
characteristic. For example, the machine may select the data from
the channel that has the most gain or the best signal to noise
ratio. In one embodiment, when using the 60 GHz frequency band, the
technique for selecting which of the channels to use is described
in IEEE 802.11ad for selecting the best beam forming link from a
two-channel receiver depending on which channel signal path link
has better performance or signal characteristics.
[0073] Referring now to FIGS. 12 and 13, an apparatus which is one
example of an item sortation machine 100 shown in FIG. 1 for
sorting items such as documents or mail pieces is designated
generally 1200. The system 1200 includes a plurality of delivery
cars 1305 (e.g., the robots 140 shown in FIG. 1) to deliver items
(e.g., item 125) to a plurality of sort locations, such as output
bins 1245 (e.g., containers 180). At a loading station 1255, each
car 1305 receives an item from an input station 1205 and delivers
it to the appropriate bin.
[0074] The cars 1305 travel along a track 1230 to the sort
locations. The track has a horizontal upper rail 1235 and a
horizontal lower rail 1250, which operates as a return leg. A
number of parallel vertical track legs extend between the upper
rail 1235 and the lower return rail 1250. In the present instance,
the bins 1245 are arranged in columns between the vertical track
legs.
[0075] After a piece is loaded onto a car, the car travels upwardly
along two pairs of vertical tracks legs and then horizontally along
two upper tracks 1235. The car 1305 travels along the upper rail
until it reaches the appropriate column containing the bin for the
piece that the car is carrying. The track 1230 may include gates to
direct the car 1305 down the vertical legs where the car stops at
the appropriate bin. The car 1305 then discharges the piece into
the bin using a transport device or system.
[0076] After discharging the piece, the car 1305 continues down the
vertical legs of the column until it reaches the lower rail 1250
which the car follows until returning to the loading station 1255
to receive another item.
[0077] The cars 1305 are semi-autonomous vehicles that each have an
onboard power source (e.g., power source 155) and an onboard motor
(e.g., a movement system 150) to drive the cars along the track
1230. The cars also include a loading/unloading mechanism (e.g.,
the transport device 145), such as a conveyor, for loading pieces
onto the cars and discharging the pieces from the cars.
[0078] Since the system 1200 includes a number of cars 1305, the
positioning of the cars is controlled to ensure that the different
cars do not crash into each other. In one embodiment, the system
1200 uses a master controller (e.g., the master controller 110 in
control system 105) that tracks the position of each car 1305 and
provides wireless commands to each car to control the progress of
the cars along the track. The master controller may also control
operation of the various elements along the track, such as the
gates. Further, the control system may output a heartbeat signal,
e.g., using a heartbeat controller 115. The cars 1305 perform the
commands to move the pieces throughout the apparatus 1200 so long
as the heartbeat signal is active as described above.
[0079] At the input station 1205, the mail pieces are separated
from one another so that the pieces can be conveyed serially to the
loading station 1255 to be loaded onto the cars 1305. Additionally,
at the input station information is determined for each piece
using, for example, a bar code scanner or a mailing address so that
the piece can be sorted to the appropriate bin.
[0080] A variety of configurations may be used for the input
station, including manual or automatic configurations or a
combination of manual and automated features. In a manual system,
the operator enters information for each piece and the system sorts
the mail piece accordingly. In an automatic system, the input
system includes elements that scan each mail piece and detect
information regarding each piece. The system then sorts the mail
piece according to the scanned information.
[0081] In an exemplary manual configuration, the input system
includes a work station having a conveyor, an input device, and a
monitor. The operator reads information from a mail piece and then
drops the piece onto a conveyor that conveys the piece to the
loading station 1255.
[0082] In an exemplary automatic configuration, the system includes
an imaging station, having an imaging device such as a high speed
line scanning camera. In one example, the imaging station scans a
bar code on each mail piece to detect information regarding the
destination for each piece. The system analyzes the image data to
determine the destination information and then controls the cars to
move the piece into a bin corresponding to the destination.
[0083] FIGS. 12 and 13 illustrate such an automated system. A
feeder 1210 in the input bin serially feeds mail pieces from the
input bin to a conveyor 1215. An imaging station 1220 positioned
along the conveyor scans the mails pieces as the pieces are
conveyed to the loading station 1255. The system 1200 analyzes a
bar code or mailing address to read information for the mail
piece.
[0084] The conveyor 1215 conveys the mail piece to the loading
station 1255 where it is loaded onto a car 1305.
[0085] The input station 1205 may be configured in a wide range of
options. The options are not limited to those configurations
described above, and may include additional features, such as an
automated scale for weighing each piece, a labeler for selectively
applying labels to the mail pieces and a printer for printing
information on the mail pieces or on the labels.
[0086] In one embodiment, the system 1200 includes a plurality of
input stations which may increase the feed rate of pieces. In
addition, the input stations may be configured to process different
types of items. In this way, each input station could be configured
to efficiently process a particular category of items. For
instance, if the system is configured to process documents, such as
mail, one input station may be configured to process standard
envelopes, while another input station may be configured to process
larger mails, such as flats. Similarly, one input station may be
configured to automatically process mail by scanning it and
automatically determining the recipient. The second input station
may be configured to process rejects, such as by manually keying in
information regarding the recipient.
[0087] The system includes a sorting station 1240 which includes an
array of bins 1245 for receiving the pieces. Additionally, the
sorting station 1240 includes the track 1230 for guiding the cars
1305 to the bins 1245.
[0088] In one embodiment, during transport, the cars travel up a
pair of vertical legs from the loading station 1255 to the upper
rail 1235 (in one example, the cars actually travel up two pairs of
rails because the track includes a forward track and a parallel
opposing track). The car then travels along the upper rail until
reaching the column having the appropriate bin. The car then
travels downwardly along two front vertical posts and two parallel
rear posts until reaching the appropriate bin, and then discharges
the mail piece into the bin. The car then continues down the
vertical legs until reaching the lower horizontal leg 1250. The car
then follows the lower rail back toward the loading station.
[0089] As can be seen in FIG. 13, the track 1230 includes a front
track 1310 and a rear track 1315. The front and rear tracks 1310,
1315 are parallel tracks that cooperate to guide the cars around
the track. In one embodiment, each of the cars includes four
wheels: two forward wheel and two rearward wheels. The forward
wheels ride in the front track, while the rearward wheels ride in
the rear track. It should be understood that in the discussion of
the track the front and rear tracks 1310, 1315 are similarly
configured opposing tracks that support the forward and rearward
wheels of the cars. Accordingly, a description of a portion of
either the front or rear track also applies to the opposing front
or rear track.
[0090] The descriptions of the various embodiments of the present
invention have been presented for purposes of illustration, but are
not intended to be exhaustive or limited to the embodiments
disclosed. Many modifications and variations will be apparent to
those of ordinary skill in the art without departing from the scope
and spirit of the described embodiments. The terminology used
herein was chosen to best explain the principles of the
embodiments, the practical application or technical improvement
over technologies found in the marketplace, or to enable others of
ordinary skill in the art to understand the embodiments disclosed
herein.
[0091] In the preceding, reference is made to embodiments presented
in this disclosure. However, the scope of the present disclosure is
not limited to specific described embodiments. Instead, any
combination of the described features and elements, whether related
to different embodiments or not, is contemplated to implement and
practice contemplated embodiments. Furthermore, although
embodiments disclosed herein may achieve advantages over other
possible solutions or over the prior art, whether or not a
particular advantage is achieved by a given embodiment is not
limiting of the scope of the present disclosure. Thus, the
preceding aspects, features, embodiments and advantages are merely
illustrative and are not considered elements or limitations of the
appended claims except where explicitly recited in a claim(s).
[0092] As will be appreciated by one skilled in the art, the
embodiments disclosed herein may be embodied as a system, method or
computer program product. Accordingly, aspects may take the form of
an entirely hardware embodiment, an entirely software embodiment
(including firmware, resident software, micro-code, etc.) or an
embodiment combining software and hardware aspects that may all
generally be referred to herein as a "circuit," "module" or
"system." Furthermore, aspects may take the form of a computer
program product embodied in one or more computer readable medium(s)
having computer readable program code embodied thereon.
[0093] Any combination of one or more computer readable medium(s)
may be used to implement embodiments of the invention. The computer
readable medium may be a computer readable signal medium or a
computer readable storage medium. A computer readable storage
medium may be, for example, but not limited to, an electronic,
magnetic, optical, electromagnetic, infrared, or semiconductor
system, apparatus, or device, or any suitable combination of the
foregoing. More specific examples (a non-exhaustive list) of the
computer readable storage medium would include the following: an
electrical connection having one or more wires, a portable computer
diskette, a hard disk, a random access memory (RAM), a read-only
memory (ROM), an erasable programmable read-only memory (EPROM or
Flash memory), an optical fiber, a portable compact disc read-only
memory (CD-ROM), an optical storage device, a magnetic storage
device, or any suitable combination of the foregoing. In the
context of this document, a computer readable storage medium is any
tangible medium that can contain, or store a program for use by or
in connection with an instruction execution system, apparatus or
device.
[0094] A computer readable signal medium may include a propagated
data signal with computer readable program code embodied therein,
for example, in baseband or as part of a carrier wave. Such a
propagated signal may take any of a variety of forms, including,
but not limited to, electro-magnetic, optical, or any suitable
combination thereof. A computer readable signal medium may be any
computer readable medium that is not a computer readable storage
medium and that can communicate, propagate, or transport a program
for use by or in connection with an instruction execution system,
apparatus, or device.
[0095] Program code embodied on a computer readable medium may be
transmitted using any appropriate medium, including but not limited
to wireless, wireline, optical fiber cable, RF, etc., or any
suitable combination of the foregoing.
[0096] Aspects of the present disclosure are described with
reference to flowchart illustrations and/or block diagrams of
methods, apparatus (systems) and computer program products
according to embodiments presented in this disclosure. It will be
understood that each block of the flowchart illustrations and/or
block diagrams, and combinations of blocks in the flowchart
illustrations and/or block diagrams, can be implemented by computer
program instructions. These computer program instructions may be
provided to a processor of a general purpose computer, special
purpose computer, or other programmable data processing apparatus
to produce a machine, such that the instructions, which execute via
the processor of the computer or other programmable data processing
apparatus, create means for implementing the functions/acts
specified in the flowchart and/or block diagram block or
blocks.
[0097] These computer program instructions may also be stored in a
computer readable medium that can direct a computer, other
programmable data processing apparatus, or other devices to
function in a particular manner, such that the instructions stored
in the computer readable medium produce an article of manufacture
including instructions which implement the function/act specified
in the flowchart and/or block diagram block or blocks.
[0098] The computer program instructions may also be loaded onto a
computer, other programmable data processing apparatus, or other
devices to cause a series of operational steps to be performed on
the computer, other programmable apparatus or other devices to
produce a computer implemented process such that the instructions
which execute on the computer or other programmable apparatus
provide processes for implementing the functions/acts specified in
the flowchart and/or block diagram block or blocks.
[0099] The flowchart and block diagrams in the Figures illustrate
the architecture, functionality and operation of possible
implementations of systems, methods and computer program products
according to various embodiments. In this regard, each block in the
flowchart or block diagrams may represent a module, segment or
portion of code, which comprises one or more executable
instructions for implementing the specified logical function(s). It
should also be noted that, in some alternative implementations, the
functions noted in the block may occur out of the order noted in
the figures. For example, two blocks shown in succession may, in
fact, be executed substantially concurrently, or the blocks may
sometimes be executed in the reverse order, depending upon the
functionality involved. It will also be noted that each block of
the block diagrams and/or flowchart illustration, and combinations
of blocks in the block diagrams and/or flowchart illustration, can
be implemented by special purpose hardware-based systems that
perform the specified functions or acts, or combinations of special
purpose hardware and computer instructions.
[0100] While the foregoing is directed to embodiments of the
present invention, other and further embodiments of the invention
may be devised without departing from the basic scope thereof, and
the scope thereof is determined by the claims that follow.
* * * * *