Note: Descriptions are shown in the official language in which they were submitted.
CA 02453754 2003-12-19
TITLE: REMOTE CONTROL SYSTEM FOR A LOCOMOTIVE
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims the benefit ~of U.S. provisional
application serial number 60/434,6'72 filed December 20,
2002. The contents of the above document are incorporated
herein by reference.
FIELD OF THE INVENTION
The present invention relates generally to remote control
systems for locomotives and, more particularly, to remote
control systems in , which a designated one of several
portable transmitter units has the authority to issue
locomotive commands at a given time.
BACKGROUND
Economic constraints have led the railway industry to
develop portable transmitter units allowing a ground-based
operator to remotely control a locomotive in a switching
yard. The unit is essentially a battery-powered transmitter
communicating by way of a radio link with a slave cantroll.er
that is either on-board the locomotive or in communication
therewith. Typically, the operator, carries this unit along
with him or her and can perform duties such as coupling and
uncoupling cars while remaining in control of the locomotive
movement at all times. This allows for placing the point of
control at the point of movement thereby potentially
enhancing safety, accuracy and efficiency.
In some instances, a single operator may effectively and
safely control a consist that includes a limited number of
1
CA 02453754 2003-12-19
cars remaining at all times well within the visual range of
the operator. However, when the consist is long, two,
operators may be required, each person being physically
close to and monitoring one end of the train. To this end,
remote control systems have been designed whereby a
locomotive controller is capable of receiving inputs from a
designated one of twa or more hand-held transmitters. An
example of such a remote control system is described in U.S.
Patent 5 , 685., 507 to Horst et al . , the contents of which a,re
l0 incorporated by reference herein.
In the two-operator arrangement described in U.S. Patent
5,685,507, each operator is provided with a portable
transmitter unit. Circuitry within each unit obtains the
current setting of various switches and levers on the unit,
resulting in the generation of a digital command word sent
periodically via radio frequency (RF) to the locomotive
controller. Tn order to avoid confusion, however, the
locomotive controller will accept, at any given point in
time, commands from only one of the portable transmitter
units, namely the one unit said to hold "command authority".
Commands received from any other portable transmitter unit
are rejected by the locomotive controller. The exception is
a limited set of emergency and signaling commands that are
available to a portable transmitter unit irrespective of
whether it holds command authority. Also disclosed in U.S.
Patent 5,685,507 is a handoff procedure for transferring the
,designation of command authority holder from one portable
transmitter unit to another.
The above arrangement therefore solves the problem of
allowing only one designated operator to execute, at any
given time, the vast majority of commands in relation to the
control of a locomotive. However, those skilled in. the art
CA 02453754 2003-12-19
will appreciate that this scheme is inefficient from a power
and bandwidth standpoint. In particular, the fact that
commands received from a portable transmitter unit that does
not hold command authority are rejected signifies that such
commands have been unnecessarily transmitted to the
locomotive controller. That is to say, since the vast
majority of, its commands will ultimately be rejected, a
portable transmitter unit that lacks command authority
causes the needless expenditure of battery power and
l0 consumption of radio frequency bandwidth.
Thus, there is a need in the industry to provide a ,remote
control system for a locomotive which alleviates at least in
part the deficiencies associated with existing systems.
SUMMARY
The present invention recognizes that battery power can be
conserved and airwave congestion reduced by precluding the
transmission of commands that will be rejected: because of
the lack of command authority of an originating portable
communications unit. Meanwhile, it is recognized that a
portable communications unit which holds command authority
must continue to be able to send a complete set of commands.
In order to allow this dual transmission, capability to take
place, each portable communications unit is made aware of
its operational status, which is either that of a command
authority holder or that of a command authority non-holder.
Tf the operational status is that of a command authority
34 holder, then a full set of commands will be transmitted to
the locomotive controller, while if the operational status
is that of a command authority non-holder, then only, a
limited set of commands will be transmitted. This results in
a reduction in the bandwidth used by a portable
3
CA 02453754 2003-12-19
communications unit whose operational status is that of a
command authority non-holder, which in turn allows the
conservation of battery power.
According.a broad aspect; therefore, the invention provides
a system for controlling a locomotive. The system includes
a plurality of portable communications units, each unit
adapted to generate signals conveying commands indicative of
functions to be performed by the locomotive . Each unit is
also associated with an operational status; the signals
generated by each unit have a characteristic dependent on
the operational status associated with that unit:. Also, the
system includes a controller adapted to receive the signals
generated by the plurality of portable communications units,
to decode the commands conveyed by the received signals and
to control the locomotive on the basis of the decoded
commands.
According to a second broad aspect, the present invention
2o seeks to provide a portable communications unit for use in a
remote control system having a controller for controlling a
locomotive. The portable communications 'unit includes a
user interface, for allowing a user to specify functions to
be performed by the locomotive and a command generator
adapted to generate commands indicative of the functions
specified by the user vi,a the user interface, the command
generator being further adapted to determine an operational
status assigned to the portable communications unit. The
portable Communications unit further includes a transmitter
3o connected to the command generator, the transmitter is
adapted to send signals conveying the commands generated by
the command generator to the Controller, wherein the signals
generated by the transmitter have a Characteristic dependent
on the operational status associated with that unit.
4
CA 02453754 2003-12-19
In accordance with a third broad aspect, the present
invention provides a controller for controlling a
locomotive. The controller includes a transceiver for
receiving commands from a plurality of remote communications
units and for sending messages to the remote communications
units. The controller further includes a processing unit
connected to the transceiver, the processing unit being
operative for assigning to each remote communications unit
to an operational status selected from the group consisting of
a command authority holder operational status and a command
authority non-holder operational status. The processing unit
is further adapted to control the locomotive on the basis of
the commands received from the remote communications units
and on the basis of the operational status of each remote
communications unit from which commands are received, the
processing unit is further adapted to allow transfer of
command authority holder operational status between the
remote communications units. Upon. a transfer of command
authority from a first remote communications unit to a
second remote communications unit, the processing unit sends
a message to the first and second remote communications
units indicative of the change in the operational status of
the respective remote communications unit.
The present invention may be summarized according to a
fourth broad aspect as a method implemented by a portable
communications unit used for instructing a locomotive
controller to control a locomotive. The method includes
3o determining an operational status associated with the
portable communications unit; assembling commands indicative
of functions to be performed by the locomotive; and
generating signals conveying the commands, the signals
CA 02453754 2003-12-19
having a characteristic dependent on the operational status
associated with the portable communications unit.
These and other aspects and features of the present
invention will now become apparent to those of ordinary
skill in the art upon review of the following description of
specific embodiments of the invention in conjunction with
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings:
Fig. 1 shows in schematic form a remote control system
composed of a controller and a plurality of portable
communications units;
Fig. 2 is a top plan view of one of the portable
communications units of Fig. 1;
Fig. 3 is a block diagram of the portable communications
units of Fig. 1, including a command generator;
Fig. 4 is a flowchart illustrating steps in the operation
the command generator of Fig. 3;
Fig. 5 is a block diagram of the controller of Fig. 2,
,including a processing unit;
Figs. 6A and 6B show a flowchart describing steps in the
operation the.processing unit of Fig. 5; and
Fig. 7 illustrates a locomotive control word generated by
the command generator of Fig. 3.
CA 02453754 2003-12-19
In the drawings, embodiments of the invention are
illustrated by way of example. It is to be expressly
understood that the description and drawings are only for
purposes of illustration and as an aid to understanding., and
are not intended to be a definition of the limits of the
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
With reference to Fig. 1, there is shown a remote control
system in accordance with an embodiment of the invention,
including a plurality of portable communications units 10,
each of which generates a digitally encoded radio frequency
(RF) signal to convey operator commands to a controller for
controlling a set of locomotives 13, 15. Separate
controllers may be mounted on-board each of the locomotives
13, 15 or, as illustrated, a single controller 46 may be
located in a central station which communicates with the
various locomotives 13, 15. The controller 46 .detects the
various RF signals transmitted by the plurality of portable
communications units 10, decodes their contents and causes
operation of various actuators on the locomotives 13, 15 to
carry into effect the commands remotely issued by the
operators (not shown).
It should be understood that not all operators are allowed
to control all trains. In general, only a limited number of
operators are allowed to control a given train, typically
one operator at the front of the train and another at the
back. To this end, it is useful to assign to each of the
operators an identifier, conveniently denoted X, Y, Z and W
in Fig. 1. In a hypothetical scenario, it may be that the
operators with identifiers X and Y are allowed to control
7
CA 02453754 2003-12-19
locomotive 13 and the operators with identifiers 2 and W are
allowed to control locomotive 15. As will be described in
further detail herein below, the identifiers of those
operators allowed to control each train are stored in a
memory within the controller 46.
Figure 2 illustrates the physical layout of a portable
communications unit 10 in accordance with an embodiment of
the present,invention. The unit 10 comprises a housing 12
enclosing electronic circuitry and a battery supplying
electric power to operate the circuitry as well as other
comporients on and within the housing 12. The main user
interface is made up of a plurality of manually operable
levers and switches 14-28, which project outside the housing
12 to allow adjustment of parameters such as locomotive
speed, rate of acceleration, sounding of horn, etc.
By way of example, various controls identified by reference
numerals on the portable communications unit in Figure 2 are
listed in the following table:
REF. CONTROL TYPE OF
NUMERAL ACTUATOR
14 Locomotive Speed Control Multi-Position dial
16 Locomotive Override Brake Multi-Position dial
Control
18 Reset Push-Button
3 0 26 Direction (Forward/Reverse/Neutral)Multi-Position Switch
22 Ring Bell/Horn Toggle Switch
24 Power on/Lights Dim/Bright Toggle Switch
20 Train Brake Control Multi-Position Switch
28 Status Request Push-Button
The various manually operable switches, levers and buttons
briefly described. above are constituted by electric contacts
whose state of conduction is altered when the control
8
CA 02453754 2003-12-19
settings are changed. For instance, the push-buttons 18 and
28 and the toggle switches 22 and 24 have electric contacts
that can assume either a closed condition or an opened
condition. The mufti-position dials 14 and 16., and the
mufti-position switches 20 and 26, have a set of electric
contact pairs, only a single pair being closed at each
position of the lever or switch. By reading the conduction
state of the individual electric contact pairs, the commands
issued by the operator can be determined.
On the front surface of the housing 12 is provided a display
panel 34 that visually echoes the control settings of the
portable transmitter 10, as determined from the conduction
state of the individual electric contact pairs. The display
panel 34 includes an array of individuallight sources 36,
such as light emitting diodes (LEDs), corresponding to the
various operative conditions of the locomotive that can be
selected by the operator. Hence, a simple visual
observation of the active LEDs 36 allows the operator to
determine the current position of the controls 14-28.
Among those portable communications units allowed to exert
control aver each of the locomotives 13, 15,, only one unit
is authorized, at any given time, to issue the vast majority
of commands. This is required in order to prevent the
controller 46 from receiving parallel sets of contradictory
commands in relation to the same train from different
portable communications units. Thus, it can be said that,
generally, at most one of the portable communications unit s
10 has a "command authority holder" operational status at
any given time, while the other portable communications
units have a "command authority non-holder" operational
status. In accordance with the present invention, each
R
CA 02453754 2003-12-19
portable communications unit will have knowledge of its
operational status.
Due to this arrangement, certain commands will only be
accepted by the controller 46 (shown in Figure 1) if they
originate from the portable communications unit that has a
"command authority holder" operational status. Thus, for
example, a portable communications unit 10 that has a
"command authority non-holder" operational status is unable
to dim the Lights of the locomotive (see reference numeral
24). Naturally, the "relinquish control to companion"
command is only available to the one portable communications
unit 10 which has a "command authority holder" operational
status.
A select subset of commands are available to all portable
communications units, regardless of their operational
status. For example, of the five types of brake control
commands (release, low, medium, full, and emergency) the
emergency brake command is available to all the portable
communications units 10, including those that have a
"command authority non-holder" operational status. The
remaining four brake commands (release, low; medium and
full) are only available to the portable communications unit
10 that has a "command authority holder°' operational status.
Also included in the subset of commands that are available
to all the portable communications units is the "ring
:bell/horn" command, which is self-explanatory. Certain
other commands relate to controls specifically directed to
those portable communications units that have command
authority non-holder operational status. Such commands
include the "reset" command, which is indicative of an
operator's desire to gain a "command authority holder"
CA 02453754 2003-12-19
operational status for his or her portable communications
unit.
In accordance with an embodiment of the present invention,
the portable communications unit 10 can be equipped with an
indicator 37 of the current operational status assigned to
the unit l0. As shown in the illustrated embodiment, the
indicator 37 may take the form of an LED which conveys the
operational status of the portable communications unit 10 in
to a visual manner. The binary distinction between 'command
authority holder" operational status and °'command authority
non-holder operational status" may be visually conveyed by
way of the presence or absence of light, a light intensity,
a rate of blinking, color of light, for example.
In an alternate implementation of the portable
communications unit 10, the sensory indicator 37 indicates
the current operational status of the unit 1.0 by means of an
audible sound or a physical movement (e.g., vibration). In
still another configuration of the portable communications
unit 10, the sensory indicator 37 may be adapted to emit a
signal only when there .has been a change in the operational
status of the unit 10. Myriad other ways of providing a
sensory indication of the operational status (or of a change
in the operational status) of the portable communications
unit 10 will become apparent to those of ordinary skill in
the art in light of the present specification and need not
be described in further detail herein.
3o FIG. 3 provides a functional diagram of the electronic
circuitry within the portable communications unit lfl.
Specifically, there is provided a command signal generator
38 and a transmitter 40, and optionally; a receiver 41.
CA 02453754 2003-12-19
The command signal generator 38 scans at short intervals the
state of conduction of each pair of contacts. A
microprocessor- within the command signal generator 38
assembles the results of the scan into a binary sequence,
hereinafter referred to as a "locomotive control word". The
transmitter 40 receives the locomotive control word from the
command signal generator 38 and generates an RF signal for
transmission of the coded sequence by a suitable modulation
scheme, such as frequency shift keying (FSK). Other
suitable modulation schemes known in the art may be used
without detracting from the spirit of the invention.
In an embodiment of the present invention, the transmitter
40 sends out the modulated locomotive control word in
repetition at a fixed rate (e. g., selected in the range from
two (2) to five (5) times per second). By providing the
transmitter 40 on each portable communi-cations-unit 10 with
a unique repetition rate, the likelihood of transmission
errors is reduced when several units in close proximity
broadcast control locomotive control words pertaining to
different locomotives. It will be known how to set each
transmitter (and the companion receiver) at a unique
transmission/reception period so as to maintain secure
communication links even when all the transmitters use the
same carrier frequency. Of course, other schemes of
conveying the locomotive control word in a robust fashion
will be apparent to those of ordinary skill in the art. For
example, a scheme using variable time intervals between
transmission is described in U:S. Patent No 6,456,674 issued
to Canac Inc, the contents of which are incorporated herein
by reference.
In an alternative implementation, it is within the scope of
the present invention for the portable communications units
I2
CA 02453754 2003-12-19
10, and the controller 46 to transmit signals using a TDMA
type, or spread spectrum type protocol. In such embod-invents,
each of the communication entities, meaning each portable
communications unit 10 (and the controller 46 in. the cases
where the controller 46 is able to transmit signals to
either the portable communications units 10 or to the
locomotives. l3, 15) is assigned a time interval within a
TDMA frame during which it is able to transmit signals . For
example, a portable communications unit 10 is able to
transmit a locomotive control word during its respective
time interval in the TDMA frame. Such a protocol avoids
collisions between transmissions by assigning only one
entity per time interval.
As indicated above, the command signal generator 38
generates a locomotive control word. The locomotive control
word may be implemented in a plurality of different ways. In
a non-limiting example, as shown in Fig. 7, a locomotive
control word 700 includes a function component 710A, 710B,
an identifier component 720 and an integrity component 730.
The function component 710A, 710B is indicative of the
desired operative state of the locomotive being controlled
by the operator of the portable communications unit l0: The
function component 710A, 714B is determined on the basis of
the state of conduction of each pair of contacts.
corresponding to the switches, levers and buttons 14-32 of
the unit 10.
In a specific implementation, the function component 710A,
710B has a length that may be dependent on the operational
status (command authority holder or command authority non-
holder) of the portable communications unit 10. For
example, commands relative to speed and braking (except zor
CA 02453754 2003-12-19
emergency braking controls) that are input by an operator of
a portable communications unit that has "command authority
non-holder" status need not be transmitted; as such commands
would in any event be rejected by the controller 46. Hence,
a majority of the information gained from the positions of
the levers, switches and buttons 14-32 can be omitted from
the function component when the portable communications unit
has "command authority non-holder" operational status.
10 Accordingly, the function component 710A is illustrative of
the case where the portable communications unit 10 has
"command authority holder" status, while the function
component 710B is illustrative of the case were the
portable communications unit 10 has "command authority non-
holder" status. As depicted, emergency commands (brake and
horn settings) as well as the "reset" control (i.e., a
request to assume "command authority holder" ope~ationa.l
status) appear as the "initial" bits of the function
component 710B.
The identifier component 720 uniquely represents the
portable communications unit 10 with respect to other
portable communications units. The identifier component 720
may be hard-wired in the circuitry of the portable
communications unit 10 (e.g,., it may be the unit's serial
number) or it may be received from the controller 46 in the
case. where the portable communications unit 10 includes a
. receiver 41. The identifier component 720 will 3~e compared
by the controller 46 to a list of identifiers that are
allowed to control a particular locomotive. Optionally, the
identifier component 720 may also include a component
uniquely representing the locomotive which is being
controlled.
I4
CA 02453754 2003-12-19
The integrity component 730, which is-aptional, is used to
assist the controller 46, in determining whether it has
correctly received the function component 710A, 710B and the
identifier component 720 of the locomotive control word 7fl0.
In one embodiment, the integrity component 730 may take the
form of a cyclic redundancy check (CRC).
Referring back to Figure 3, in order to assemble the various
components of the locomotive control word 700, an embodiment,
of the present invention provides the command signal
generator 38 with a microprocessor that runs a program
stored an a computer-readable medium. In a different form
of construction, the command signal generator 38 may be
constituted by an array of hardwired logic gates that
generate the locomotive control word upon actuation of the
controls.
Operation of the microprocessor in accordance with its
program is now described in greater detail with reference to
the flowchart in Fig. 4. At step 410, the microprocessor
records the state of conduction of the electric contacts of
the transmitter controls. This may be done on a periodic
basis or upon a change being detected in one of the
actuators. At step 420; the microprocessor checks the
operational status of the portable communications unit 10.-
On the basis of the identity of the closed contacts, and on
the basis of the operational status of the portable
communications unit 10, the microprocessor will produce
either the full-length function component 710A or the
shortened function component 710B of the locomotive control
word 700.
Specifically, if at step 420, the microprocessor determines
that the operational status of the portable communications
I~
CA 02453754 2003-12-19
unit 10 is that of a "command authority holder", then the
microprocessor proceeds to step 430, where the full-length
function component 710A is assembled. In particular, the
function component 710A will be indicative of the various
settings selected by the operator, including speed, brake,
power and horn settings, among others. The microprocessor
then proceeds to step 450.
On the other hand, if at step 420, it is determined that the
operational status of the unit 10 is that of a command
authority non-holder, then the microprocessor proceeds to
step 440, where the shortened function component 7108 is
created on the basis of a restricted subset of the ~ controls
selected by the operator. This subset may be limited to
25 emergency controls, such as an emergency brake control 16,
as v~iell as the control indicative of a desire to gain
command_authority. holder operational status, which could be
conveyed by the operator via the reset push-button 18, or
any other input, or sequence of inputs. The microprocessor
then proceeds to step 450.
At step 450, the, microprocessor appends the identifier
component 720. to the function component (either 710A or
7108): In order to minimize the design complexity of the
controller 46 (to be described later), it may be
advantageous to append the identifier component 720 to the
"front" of the function component, such that it is released
before the function component.
At step 460, a data security code enabling the controller 46
to check for transmission errors maybe created and appended
in the form of the integrity component 730. As with the
identifier component 720, the integrity component 730 can be
appended to an operational-status-invariant location with
16
CA 02453754 2003-12-19
respect to the remainder of the locomotive control word,
such as the "front" of the identifier component 720 or
between the identifier component 720 and the function
component 710A, 710B.
At step 470, the completed locomotive control word 700 is
supplied to the transmitter 40, which handles modulation arid
radio frequency transmission of the locomotive control word
to the controller 46. It will be appreciated that the use
l0 of shorter words when the portable communications unit 10
has "command authority non-holder" operational :status
results in quicker completion of the transmission and hence
uses less bandwidth on the wireless link and allows the unit
to conserve power. After step 470, the microprocessor
returns to step 410 and waits for the next occasion to
record the state of conduction of the electric contacts of
the transmitter controls.
In a non-limiting embodiment, in order to further reduce
bandwidth occupied by ignals sent from a portable
communication unit 10 having a "command authority non-
holder" operational status, the transmitter 40 can transmit
signals generated by portable communication units l0 having
a "command authority non-holder" operational status at a
reduced repetition rate in comparison to the signals
generated by a portable communication unit 10 having a
"command authority holder" operational status. As such,
locomotive control words 700 generated by portable
communication units 10 having "command authority non-holder"
operational status would be transmitted less frequently than
a locomotive control word 700 generated by a portable
communication unit 10 having a "command authority holder"
operational status.
CA 02453754 2003-12-19
It should be understood that in such an alternative
embodiment, it is not necessary for the portable
communication units 10 to generate locomotive control words
having shortened function components 7108. As such, in an
alternative embodiment the repetition rate of transmission
may be lessened for the portable communication units 10
having a "command authority non-holder" operational status,
while the function component 710B of the locomotive control
words 700 generated by the portable communication units l0
l0 having a "command authority non-holder" operational status
is of the same length as the locomotive control words 700
generated by the portable communications unit 10 having a
"command authority holder" operational status.
In yet another non-limiting embodiment, in the case where
the portable communication units 10 use TDMA, or spread
spectrum protocols, it is possible for the portable
communications unit 10 having a "command authority holder"
operational status to be assigned a time interval in the
2o TDMA frame having a longer length than the time intervals
assigned to the portable communications units 10 having a
"command authority non-holder" operational status.
Alternatively,, it is possible for the portable communication.
unit 10 having the "command authority holder" operational
status to be assigned more time intervals in the TDMA frame
than the portable communications units 10 having the
"command authority non-holder" operational status.
As described above, it is within the scope of the present
3o invention for the portable communications units 10 to
include a sensory indicator 37 for indicating to an operator
whether the portable communications unit 10 has a "command
authority holder" operational status or a "command authority
non-holder" operational status. In order to inform the
I~
CA 02453754 2003-12-19
operator of the current operational status of the portable
communications unit 10, the sensory indicator 37 may be
triggered or toggled when appropriate.
In a first example of implementation, the portable
communications units 10 do not include a receiver 41 for
receiving signals from the controller 46, or from other
portable communications units 10. In such an embodiment, the
portable communications units 10 include a memory in which
l0 is stored a profile associated to the "command authority
holder" operational status, and the "command authority non-
holder" operational status. Depending on the operational
status of the portable communication unit 10, the memory is
set to select either one of the "command authority holder"
operational status, or the "command authority non-holder"
operational status. In a non-limiting example of
implementation, when the operator of a portable
communications unit 10 that has a "command authority holder"
operational status decides to relinquish that status, the
operator activates the "reset" button, or any other input,
or sequence of inputs, needed to relinquish the operational.
status. Upon activation of the relinquish inputs, the memory
of the portable communication device is modified such that
the memory toggles to select the opposite operational
status, which is the "command authority non-holder"
operational status. Once this is done, the operator of that
portable communication unit 10 communicates either verbally,
or through a visual cue, to the operator of another portable
communications unit 10 that it should acquire the °'command
authority holder" operational statuso Accordingly, the
operator of that other portable communication unit 10 can
then activate the "reset" button, or any other input, or
sequence of inputs, on his/her portable communication unit
10, such that its memory toggles to the profile associated
L9
CA 02453754 2003-12-19
to "command authority holder" operational status. In this
manner, each of the affected portable communications units
will appropriately tailor the format of the locomotive
control words they generate meaning the message length,
repetition rate or both, in accordance with their respective
new operational status.
It should be understood that by activating the "reset"
button, or other input or sequence of inputs, as described
l0 above, the portable communications units 10 send signals to
the controller 46 indicative of the desire to switch
operational status. However, in the above described
embodiment, the portable communications units 1d do not
receive confirmation from the controller 47 or from the
other portable communication units 10 as to the change, or
current status; of their respective operational status.
The controller 46 is responsive to the signals indicative of
the desire to switch operational status to update in its own
2o memory the profiles of the portable communications units 10,
such that its memory is up to date as to which portable
communications unit 10 has a "authority command holder°'
operational status. It will be appreciated that in order for
a portable communication unit to be assigned the "command
authority holder" operational status, the portable
communications unit 10 that previously held that status gust
have sent a signal relinquishing that status.
In an alternative embodiment, as shown in Figure 3, the
3o portable communication units 10 include a receiver 41, and
the operational status of the unit 10 (command authority
holder or command authority non-holder) is communicated to
the receiver 41 by the controller 46, e.g., via a wireless
link. Upon receipt of a signal from the controller at the
CA 02453754 2003-12-19
receiver 41, the receiver 41 is configured to distribute the
operational status to the, other components of the portable
communications unit 10, namely the command signal generator
38, the transmitter 40 and the sensory indicator 37.
Alternatively, when the current operational status of the
portable communication unit 10 is checked at step 420, as
described above with respect to Figure 4, it is within the
scope of the present invention to determine whether this
current operational status is different from the operational
status that was in effect during the previous execution of
step 420. If .there has been a change, then the sensory
indicator 37 can be triggered (e. g., an audible tone with
increasing.pitch or volume to indicate assumption of command
authority and decreasing pitch or volume to indicate
relinquishing of command authority). Alternatively ; the
sensory indicator 37 can be toggled (e.g., LED on to
indicate that- the unit 10 has command authority and LED off
to indicate that the unit 10 does not have command
authority). It should be understood that although the
sensory indicator 37 has been described above as being in
the form of a light or a sound, any type of display, such as
text or pictograph, could also be used to indicate the
operational status to an operator, without departing from
the spirit of the invention.
Fig. 5 provides a functional diagram of the controller 46,.
which can be either mounted on board one of the locomotives
13, 15 or centrally arranged to communicate with each of the
locomotives 13, 15 in wireless or wireline fashion. The
controller 46 includes a transceiver unit 48, or a receiver
unit in the case where the controller 46 is unable to
transmit signals to the portable communication units 10, a
processing unit 50 and an interface 72. The processing unit
50 includes a CPU 66 with access to a memory 68 ir~ which are
2~
CA 02453754 2003-12-19
stored (1) a list of identifiers specifying those portable
communications units allowed to control each locomotive and
(2) the identifier of the single portable communications
unit which currently has command authority holder
operational status. If the controller 46 is mounted on-
board a given locomotive, then the interface 72 will
typically connect the processing unit to a driver unit 52
and to a plurality of sensors 78 situated on the locomotive.
Otherwise, if the controller 46 is mounted remotely from the
locomotive, the interface 72 will be connected to another
transceiver unit (not shown) which maintains communication
with a driver unit 52 and a plurality of sensors 78 located
on board the locomotive.
The transceiver unit 48 senses modulated signals sent out
from the portable communications units ZO and decodes the
locomotive control words contained therein. Details of
channel acquisition and synchronization are not described
here as they are assumed to be within the reach of a person
ordinarily skilled in the art.
In general, a received locomotive control word might have
been sent out,by a portable communication unit that is not
allowed to control a particular locomotive. Assuming,
however, that the originating portable communications unit
is indeed allowed to control the locomotive in question, the
operational status (i.e:, command authority holder or
command authority non-holder) is still not known a priori to
the transceiver 48. Hence, the transceiver should be
capable of decoding both types of locomotive control words,
namely those originated by a portable communications unit
having "command authority holder" operational status as well
as those originated by a portable communications unit having
"command authority non-holder" operational status.
22
CA 02453754 2003-12-19
In one embodiment of the present invention, the lack of a
priori knowledge of the operational status of the
originating portable communications unit is inconsequential
to design or operation of the transceiver 48. This is
because, in such an embodiment, the only difference between
locomotive control words issued by portable communications
units having differing operational status appears in the
length of the locomotive control word, and possibly, the
repetition rate at which the locomotive control word is
sent. The mere presence of certain superfluous bits at the
tail end of a locomotive control word issued by .a portable
communications unit that does not have command authority
holder operational status:will not affect the validity of
the initial bits which may contain emergency commands or a
command indicative of a desire to assume command authority
holder operational status. It is therefore acceptable to
allow the transceiver 48 to feed the processing unit 50 with
a full-length locomotive control word without knowledge of
the operational status of the originating partable
communications unit.
The processing unit 50 receives the locomotive control word
from the transceiver 48 as well as input signals received
via the interface 72 from various sensors on the locomotive
in question. Examples of sensors include direction sensors,
speed sensors, pressure sensors, air flow rate sensorsl etc.
The interface 72 receives the signals produced by the
sensors and digitizes them where required so they can be
directly processed by the CPU 66. The CPU 66 generates
binary signals for commanding the various controls of the
locomotive in question and supplies these binary signals via
the interface 72. Optionally; the processing unit 50
supplies data conveying an indication of each portable
23
CA 02453754 2003-12-19
transmitters unit's operational status to the transceiver
unit 48, in the cases where the transceiver 48 transmits
signals to the portable communication units 10 regarding the
operational status of the portable communication units l0.
In order to generate the signals to control a given
locomotive and, when necessary, to inform a portable
communications unit of its operational status, the CPU 66
runs a program stored on a computer-readable medium:
to Operation of the CPU 66 in accordance with its program is
now described in greater detail with reference to the
flowchart in Fig. 6A & 6B.
Specifically, upon reception of a locomotive control word
700 at step 610, the CPU 66 will identify the full-length
function component, a.s well as the identifier component and
the integrity component. It will of course be appreciated
that the function component actually transmitted may have
been a shortened version of the function component, in the
2o event that the originating portable communications unit has
command authority non-holder operational status. Although
the length of the function component will be an important
factor later on (see steps 660, 670), this is still not
relevant at the present stage of processing.
At step 620, the CPU 66 compares the identifier component of
the locomotive control word to a list of two or more
possible identifiers stored in the memory 68. The list of
acceptable identifiers contains the identifiers of all the
portable communications units allowed to control the
locomotive.
If, at step 630, the identifier in the locomotive control
word does not correspond to any one of the identifiers in
~4
CA 02453754 2003-12-19
the list, then the CPU 66 rejects the word and takes no
action. Otherwise, the system will examine the function
component in order to determine what are the requested
functions that the locomotive should perform. If, at step
640, it is determined that the function component is
indicative of a command that can be sent by either a
"command authority holder" portable communication unit or a
"command authority non-holder" portable communication unit.
In this non-limiting implementation depicted in Figure 6A,
to at step 640 it is determined whether the function component
is indicative of a request to apply the emergency brake or
to sound the bell or horn, then the system complies with the
request. If step 640 answered in the negative, at step 650,
the system will implement the command only if the identifier
in the locomotive control word matches a specific identifier
in the list that designates the remote transmitter currently
holding the command authority (steps 660 and 670).
If, indeed, step 670 is verified, then the locomotive
executes the command unless it is determined at step 680
that the command is a request to transfer command authority
to another remote controller. The CPU 66 recognizes this
request by checking the state of the bit reserved for this
function in the locomotive control word. If the state of
the bit is 1 (command transfer requested), the CPU 66 will
proceed to perform a certain number of safety checks to
determine if the command transfer can be made in a safe
manner. More particularly, the CPU 66 will determine if the
locomotive is stopped and if the brake safety checks (steps
690, 692) are verified. If the locomotive is moving or the
brake safety checks fail, then no action is taken and the
command remains with the portable transmitter currently in
control.
2~
CA 02453754 2003-12-19
If steps 690 and 692 are successfully passed, then the CPU
66 proceeds to monitor the reset bit of all the locomotive
control words received that carry an identifier in the list
stored in the memory 68 (the reset bit issued by the
transmitter currently holding the controls is not
considered). The procedure of checking the reset bit, or
any other confirmation button or sequence, is used for
safety purposes in order to transfer the control of the
locomotive only when the target portable communications unit
has effectively acknowledged acceptance of the control. To
this end, the CPU 66 executes to step 694, where it
determines whether, within a designated amount of time
(e. g., 10 seconds), the "reset" bit has been set to~the high
position. This requires performing an additional series of
steps similar to steps 610 through 650. If the time limit
has expired without having received an indication that a
portable communications unit wishes to assume command
authority holder operational status, the CPU 66 will abort
the transfer function and resume normal execution of the
program.
However, if within the designated amount of time sinoe
reception of ,the request to transfer control from the
current transmitter the CPU 66 observes a reset bit in the
high position, implying that the operator of a remote
transmitter in the pool of candidates able to acquire
control has depressed the reset button, the program proceeds
to step 696, where the CPU 66 modifies the memory 68 to
reflect the identity of the portable communications unit
3o that has assumed command authority. For example, this may
be done by shifting in memory 68 the identifier associated
with the reset bit at high to the position of the current
holder of command authority. From now on, the CPU 65 will
accept commands (except the safety-related controls such as
26
CA 02453754 2003-12-19
applying the emergency brake and sounding the bell/horn)
only from the new holder of command authority. In addition,
at step 698, which is an optional step, the CPU 66 signals
to the former holder of command authority that its
operational status has been changed to that of command
authority non-holder and, likewise, signals to the new
holder of command authority that its operational status has
been changed to that of command authority holder. Both
signaling operations are effected via the transceiver unit
48. Each of the affected portable communications units will
appropriately tailor the format of the locomotive control
words they generate in accordance with their respective new
operational status.
In the non-limiting embodiments described above, the
multiple portable communication units 10 have been described
as having a "command authority holder" operational status,
or a "command authority non-holder" operational status. It
should be understood that instead of having multiple
portable communication units 10 with these operational
status, it is within the scope of the present invention for
one of the portable communication units to have a "student"
operational status, and for one or more other portable
communication units 10 to have a "trainer" or "teacher"
operational status.
In such an embodiment, the portable communication unit 10
having a "student" operational status would be able to
generate locomotive control words having a function
3o component 710A having commands relative to the desired
operative state of the locomotive. Moreover, the portable
communication unit 10 having a "student" operational status
would be able to control most, if not all, of the
functionality of the locomotive, similarly to the portable
27
CA 02453754 2003-12-19
communications units 10 having an "authorized command
holder" operational status.
However, the portable communication units 10 having the
"trainer" operational status would be slightly different
from the portable communication units 10 having the
"authorized command non-holder" operational status. More
specifically, the operator of the portable communication
units 10 having the "trainer" operational status would only
l0 provide inputs via the switches, levers and buttons when it
is desired to override the commands sent by the operator of
the portable communication unit 10 having the "student"
operational status. As such, the command signal generator 38
of the portable communication units 10 having the "trainer"
operational status would scan the contacts of the controls
14-28 and would only generate a locomotive control, when
there is a change in the controls 14-28, thereby indicating
that the operator has entered a command. Upon receipt of the
locomotive control word from a portable communication snit
10 having the "trainer" operational status the processing
unit 50 of the controller 46 is operative to override any
command sent by the portable communication units 10 having
the "student " operational status, and implement the commands
contained in the function component of the locomotive
control word of the portable communication units 10 having
the "trainer" operational status.
In this manner, the remote control system is able to
conserve bandwidth by only transmitting a locomotive control
word issued by a portable communications unit 10 having the
"trainer" operational status when the operator of the
portable communications unit 10 having the "trainer"
operational status desires to overide a command sent by a
portable communication units 10 having the "student"
2~
CA 02453754 2003-12-19
operational status. Alternatively, the portable
communication unit 10 having the "trainer" operator status
may send periodic contact messages of the type "I am alive".
The controller 46 is adapted to continue to implement
commands issued by the portable communication unit having
the "student" operational status only as long as it receives
the periodic "I am alive" message from the "trainer".
Advantageously, this prevents the controller 46 from
implementing commands from the "student" when the "trainer"
is unable to override the commands.
Those skilled in the art will appreciate that various
alternative implementations of the present invention are
possible. For example, there exist alternatives to the use
of a unique repetition rate to allow secure communication
between the transmitters in the various portable
communications units l0 and the controller 46 while sharing
the same frequency band. An example is spread spectrum
communication, a specific example of which is code division
multiple access (CDMA). In such a scenario, each portable
communications unit can be supplied with its own spreading
code or its own Walsh code, allowing interference-free
communications to occur contemporaneously and within a
common frequency range.
The transmitter and receiver gear of the remote locomotive
control system in accordance with a non-limiting example of
implementation of the invention has been described above in
terms of function of the principal parts of the system and
3o their interaction. The components and interconnections of
the electric network necessary to carry into effect the
desired functions are not being specified because such
details are well within the reach of a person skilled in the
art.
CA 02453754 2003-12-19
Also, those skilled in the art will appreciate that each of
the various processing units described herein above may be
implemented as an arithmetic and logic unit (ALU) with
access to a code memory which stores program instructions
for the operation of the ALU. The program instructions
could be stored on a medium which is fixed, tangible and
readable directly by the processor, (e. g., removable
diskette, CD-ROM, ROM, or fixed disk), or the program
l0 instructions could be stored remotely but transmittable to
the processor via a modem or other interface device (e.g., a
communications adapter) connected to a network over a
transmission medium. The transmission medium may ~e either
a tangible medium (e. g., optical or analog communications
lines) or a medium implemented using wireless techniques
(e. g., microwave, infrared or other transmission schemes).
Those skilled in the art should also appreciate that the
program instructions stored in the code memory can be
2o compiled from a high level program written in a number of
programming languages for use with many computer
architectures or operating systems. For example, the high
level program, may be written in assembly language, while
other versions may be written in a procedural programming
language (e. g., "C") or an object oriented programming
language (e.g., "C++" or "JAVA"). Those skilled in the art
should further appreciate that in some embodiments of the
,invention, the functionality of the processor may be
implemented as pre-programmed hardware or firmware elements
(e. g., application specific integrated circuits (ASICs),
electrically erasable programmable read-only memories
(EEPROMs), etc.), or other related components.
CA 02453754 2003-12-19
While specific embodiments of the present invention have
been described and illustrated, it will be apparent to those
skilled in the art that numerous modifications and
variatioz~s can be made without departing from the scope of
the invention as defined in the appended claims.
3~
