Note: Descriptions are shown in the official language in which they were submitted.
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TITLE: Remote Controi System for a Locomotive with Solid
State Tilt Sensor
FIELD OF THE INVENTION
s
The present invention relates to an electronic system
and components thereof for remotely controlling a
locomotive. The system has a tilt sensor designed to
operate in low temperatures often encountered in northern
regions.
BACKGROUND OF THE INVENTION
Economic constraints have led railway companies to
develop portable master controllers allowing a ground-
based operator to remotely control a locomotive in a
switching yard. The portable master controller has a
transmitter communicating with a slave controller on the
locomotive by way of a radio link. To enhance safety, the
portable master controller carried by the operator is
provided with a tilt-sensing device to monitor the spatial
orientation of the portable master controller and
determine occurrence of operator incapacitating events;
such as the operator tripping and falling over objects and
loss of conscience due to a medical condition, among
others. When the tilt-sensing device reports that the
portable master controller i_s outside the normal range of
inclination, t'he portable master controller will
automatically generate, without operator input, a command
signal over the radio link to stop the locomotive.
Tilt-sensing devices used by prior art. portable
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master controllers are in the form of mercury switches.
Those have proven unreliable in cold temperature
operations where the mercury bead in the switch can freeze
and loose mobility. Attempts to overcome this drawback
include adding thallium to the mercury to lower its
freezing point. This solution, however, is objectionable
because thallium is a toxic substance. Hence, for
environmental reasons, thallium is very rarely used in the
industrial community.
Against this background, the reader will appreciate
that a clear need exists in the industry to develop a
system and components thereof for remotely controlling a
locomotive, featuring tilt-sensing devices that can
reliably operate in very low temperatures and 'do not use
mercury or thallium materials in their construction:
SUMM~IRY OF THE INVENTION
In one broad aspect, the invention provides a portable
master controller for a locomotive remote control system.
The portable master controller has a user interface for
receiving commands to control a movement of the
locomotive. The user interface is responsive to operator
commands to generate control signals. The portable master
controller includes a processing unit receiving the
control signals from the user interface to generate
digital command signals directing the movement of the
locomotive. A transmission unit receives the digital
command signals and generates a RF transmission conveying
the digital command signals to the slave controller.
A solid-state tilt sensor incommunication with the
processing unit communicates inclination information to
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the processing unit about the portable master controller.
The processing unit receives and processes the inclination
information. If the inclination information indicates that
the portable master controller is in an unsafe.operational
condition, the processing unit generates an emergency
digital command signal to the transmission unit, without
input from the operator, for directing the locomotive to
acquire a secure condition.
By "solid-state" is meant a tilt sensor that does not
uses a liquid to produce inclination information.
In a specific' and non-limiting example of
implementation, the solid-state tilt sensor includes a
single axis accelerometer responsive to the acceleration
of gravity. Optionally, the accelerometer. is a multi-axis
device responding to vertical acceleration and
acceleration in at least another axis, as well. The
ability to assess acceleration levels in axes other than
the vertical axis permits detection of unsafe conditions
that do not necessarily translate into an excessive
inclination of the portable master controller.
The inclination information sent by the solid-state tilt
sensor can be in any form as long as it allows the
processing unit to detect an unsafe operational condition.
The determination as to what is safe and what is unsafe
can vary greatly according to the specific application.
All the variants, however, include a common denominator,
which is an assessment of the degree of inclination of the
portable master controller. In addition to the assessment
of the degree of inclination, other parameters may be
taken into account, such as the time during which the
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portable master controller remains beyond a certain
inclination angle, among others.
Once the occurrence of an unsafe operational condition
has been detected, the processing unit generates an
emergency command signal to direct the locomotive to
acquire a secure condition. A "secure" condition is a
condition in which the risk of accident from the
locomotive is substantially reduced. An example of a
secure condition is. stopping the locomotive.
In a second broad aspect, the invention provides a
remote control system for a locomotive including in
combination the portable master controller defined broadly
above and the slave controller for mounting on-board the
locomotive.
In third broad aspect, the invention provides a portable
master controller that uses an accelerometer to generate
inclination information.
Under a fourth broad aspect, the invention provides a
remote control system for a locomotive that has a portable
master controller using an accelerometer to generate
inclination information.
BRIEF DESCRIPTION OF THE DRAWINGS
A detailed description of examples of implementation
of the present invention is provided hereinbelow with
reference to the following drawings, in which:
Figure 1 is a functional block diagram of the remote
control system for a locomotive according to 'a specific
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and non-limiting example of implementation of the
invention;
Figure 2 is a structural block diagram of the
portable master controller of the system shown in Figure
1;
Fsgure 3 is a structural block diagram of the slave
controller of the system shown in Figure 1; and
Figure 4 is a flow chart illustrating a' diagnostic
procedure to identify a malfunction of the solid state
tilt sensor.
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
Figure 1 is a high-level block diagram of a remote
control system 10 for a locomotive. The remote control
system 10 includes a portable master controller l2 that is
carried by a human operator. The system 10 also includes
a slave controller 14 mounted on-board the locomotive
(locomotive not shown in the drawings). The portable
master controller 22 and the slave controller 14 exchange
3o information over a radio link 16.
The portable master controller 12 includes a user=
interface l8 through which the operator enters commands to
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control the movement of the locomotive. Such commands may
include forward movement, backward movement, movement at a
certain speed, coasting, stopping, etc. Optionally, the
user interface 18 also conveys information to the
operator, such as status information, alarms, etc. The
user-interface 18 may comprise a variety of input
mechanisms to permit the user to enter commands. Those
. input mechanisms may include electromechanical knobs and
switches, keyboard, pointing device, touch sensitive
surface and speech recognition capability, among others.
Similarly, the user-interface 18 may comprise a variety of
output mechanisms to communicate i.riformation to the user
such as visual display or audio feedback, among others:
The user-interface 18 generates control signals 20,
which represent the inputs of the operator. Tn instances
where the user-interface 18 also communicates information
to the operator, data signals 22 are supplied to the user-
interface 18 from a processing unit 2-4, to be described
below. The data signals convey the information that is to
be communicated to the user.
The processing unit 24 receives and processes the
control signals 20. The extent of the processing performed
by the unit 24 will depend on the particular control
strategy implemented by the system 10. At its output, the
processing unit 24 will issue digital command signals 26
that direct the operation of the locomotive. Those command
signals 26 represent commands, such as move forward, move
backwards, stop, move at a selected speed; throttle
command; brake command, among others.
The command signals 26 are supplied to a transmission
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unit 28 that generates a Radio Frequency (RF) transmission
conveying those commands over the-RF link 16 to the slave
controller 14.
The slave controller 14 is comprised of a receiver
module 30 for sensing the RF transm.ission over the RF link
16. The receiver module 30 generates at its output
digital command signals 32 that are passed to a processing
module 34 that processes those signals and issues local
signals 36 that control the locomotive. The local signals
36 include, for example, throttle settings, brake
settings, etc.
An important feature of the system 10 is a tilt
sensor 38 that is part of the portable master controller
12. The tilt sensor 38 produces inclination information
about the portable master controller 12 and sends this
inclination information to the processing unit 24. The
processing unit 24 will analyze this information to
determine if the portable master controller 12 is in a
potentially unsafe operational condition. In the
affirmative, the processing unit 24 generate s internally
an emergency digital command signal directing the
locomotive to acquire a secure condition. The digital
command signal is sent to the slave controller via the
transmission unit 28 and the radio link l6.
The inclination information processing strategy,
which determines if the portable master controller 12- is
in an operational condition that is safe or unsafe, can
greatly vary and can take into account various parameters.
One of those parameters is the degree of inclination of
the portable master controller I2. In one example, the
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degree of inclination can be quantified in terms of angle
of inclination. Another parameter is the time during which
the portable master controller 12 is maintained at or
beyond a certain degree of inclination. One possible
strategy is to declare an unsafe operational condition
only after a certain degree of inclination has been
maintained for a predetermined time period, thus avoiding
issuing the emergency digital command' signal in cases
where the operator moves his body in such a way that it
will excessively tilt the portable master controller 12,
but only for a moment.
The reader will appreciate that a wide variety of
inclination information processing strategies are possible
without departing from the spirit of the invention. All
those' strategies rely on the degree of inclination as
parameter; alone or in combination with other parameters.
In a specific example of implementation; the tilt
sensor 38 is an accelerometer that is responsive to static
gravitational acceleration. By "static" it is meant that
the accelerometer senses the force of gravity even when
the portable master controller 12 is not moving vertically
up or down. The accelerometer is mounted in the casing of
the portable master controller 12 such that the axis along
which the acceleration is sensed coincides with the
vertical axis. When the portable master controller l2 is
inclined, the component of the force of gravity along the
vertical axis changes which allows determining the degree
of inclination of the portable master controller l2.
Optionally, the accelerometer may also be sensitive
about axes other than the vertical axis to detect abnormal
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accelerations indicative of potentially unsafe conditions
that may not translate in an abnormal inclination of the
portable master controller 12. Examples of such other
abnormal accelerations arise when the portable master
controller 12 (or the operator) is severely bumped
without, however, the operator falling on the ground.
In a possible variant the tilt sensor 38 may include
a plurality of accelerometers, each accelerometer being
sensitive in a different axis.
When the tilt sensor 38 includes an accelerometer
that outputs a signal having both a dynamic and a static
component, it is desirable to filter out the dynamic
component such as to be able to mare easily .determine or
derive the orientation of the master controller 12.
Techniques to filter out the dynamic component of the
output signal are known in the, art and will not be
discussed here in detail.
If the processing unit 24 recognizes an unsafe
operational condition; it issues an emergency command
signal to secure the locomotive. (?ne example of securing
the locomotive includes directing the locomotive to
~ perform to stop.
In a specific and non-limiting example of
implementation the tilt sensor 38 is based on an
accelerometer available from Analog Devices Inc. in the
USA, under part number ADXL202. The output of the tilt
sensor 3~8 is a pulse width modulated signal, where the
width of the pulse indicates the degree of inclination.
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For safety reasons, it is desirable for the
processing unit 24 to determine when the tilt sensor 38
may be malfunctioning. At this end the processing unit 24
has diagnostic unit 25 that implements a diagnostic
procedure. The diagnostic procedure runs continuously
during the operation of the master controller l2. The
flow chart of the diagnostic procedure is shown at Figure
4. The procedure starts at step 100. At step 102 the
signal from the tilt sensor 38 is received by the
processing unit 24. The diagnostic procedure then performs
two series of actions designed to confirm the proper
operation of the tilt sensor 38 and the continued
operation of the tilt sensor 38. The proper operation
procedure will be described first. At . step 104 a timer is
started. The timer runs for a predetermined period of
time. For example, this period of time can be from a
couple of seconds to a couple of minutes. Decision step
26 detects changes in the output signal of the tilt sensor
38. If a change is noted, i.e., indicating a movement of
the master controller 12, the timer 104 is reset: If no
change is noted i.e., indicating a lack of master
controller movement during the predetermined time period
(the timer expires), the step 108 is initiated.
The step 108 verifies the integrity of tilt sensor
108 by performing a calibration test. This is effected by
subjecting the tilt sensor 38 to a known condition that
will produce a variation in the output signal. One
possibility is to subject the tilt sensor 38 to a self-
test which will induce a change in the output signal.
Sending a control signal to a pin of the tilt sensor 38
initiates such self-test. At step 110, the processing
unit 24 observes the output signal and if a change is
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noted, which indicates that no detectable malfunction is
present, then processing continues at step 100.
Otherwise, the conditional step 110 branches to step 112
that triggers an alarm . The alarm may be an audible,
visual (ar both) indication on the user interface 18 that
a malfunction has been noted. Once the alarm at step 112
has been triggered, one possibility for the processing
unit 24 is to generate an emergency digital command signal
to -the transmission unit 28 without input from the
l0 operator, for directing the locomotive to acquire a secure
condition.
The continued operation procedure is performed at the
same time as the proper operation procedure. The
continued operation procedure includes a decision step 114
at which the output signal of the tilt sensor 38 is
validated. In this example, the validation includes
observing the signal to determine if it is within a normal
range of operation. For example, when the output signal
of the tilt sensor 38 is a pulse width modulated signal
(PWM) the decision step 114 screens the signal
continuously and if the frequency of the signal falls
outside the normal range of operation of the tilt sensor
38 or the signal disappears altogether, a tilt sensor
failure is declared. When such tilt sensor failure
occurs, the alarm 112 is triggered and the 'locomotive
brought to a secure condition, as described earlier.
It should, be noted that the diagnostic procedure
implemented by the processing unit 24 might vary from the
example described earlier without departing from the
spirit of the invention. For instance, the diagnostic
procedure may include only the steps necessary to perform
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the proper operation procedure without the steps for
performing the continued operation procedure.
Alternatively, the diagnostic procedure may include only
the steps necessary to perform the continued operation
procedure without the steps for performing the proper
operation procedure. Objectively, both the proper
operation and continued operation procedures are desirable
from the standpoint of enhanced safety, however one of
them can be omitted while still providing at least some
degree of protection against tilt sensor failure.
Figure 2 is a structural block diagram of the
portable master controller 12. The portable master
controller l2 is largely software implemented and includes
a Central Processing Unit (CPU) 40 that connects with a
data storage medium 42 over a data bus 44. The data
storage- medium 42 holds the program element that. is
executed by the CPU 40 to implement various functional
elements of the portable master controller 12, in
particular the processing unit 24. Data is exchanged
between the CPU 40 and the data storage medium 42 over the
data bus 44. Peripherals connect to the data bus 44 such
as to send and receive information from the CPU 40 and the
data storage medium 42. Those peripherals include the
user interface l8, the transmission unit 28 and the tilt
sensor 38.
It should be noted that the diagnostic unit 25 (shown
in Figure 1) is implemented in software by the, processing
unit 24. Alternatively, the diagnostic .procedure may be
implemented partly in hardware and partly in software or
only in hardware.
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' Figure 3 is a structural block diagram of the slave
controller l4. As is the case with the portable master
controller 12, the slave controller 14 has a CPU 46
connected to a data storage medium 48 with a data bus 50.
The data storage medium 48 holds the program element that
is executed by the CPU 46 to implement various functional
elements of the slave controller 14, in particular the
processing module 34. Peripherals connect to the data bus
50 such as to send and receive information from the CPU 46
and the data storage. medium 48. Those peripheral s include
the receiver module 30 and an interface 52 through which
the slave controller 14 connects to . the locomotive
controls.
Although various embodiments have been illustrated,
this was for the purpose of describing, but not limiting,
the invention. Various modifications will become apparent
to those skilled in the art .and are within the scope of
this invention, which is defined more particularly by the
attached claims.
