U.S. patent application number 14/722831 was filed with the patent office on 2016-12-01 for electronic speed control for locomotives.
This patent application is currently assigned to Caterpillar Inc.. The applicant listed for this patent is Caterpillar Inc.. Invention is credited to Joshua Fossum, Khanh Ngo, Cody Ryerson.
Application Number | 20160347315 14/722831 |
Document ID | / |
Family ID | 55963119 |
Filed Date | 2016-12-01 |
United States Patent
Application |
20160347315 |
Kind Code |
A1 |
Ngo; Khanh ; et al. |
December 1, 2016 |
Electronic Speed Control for Locomotives
Abstract
A drivetrain system for a machine includes an engine, a brake,
and a controller operatively coupled to the engine and the brake.
The controller is configured to generate a first speed error based
on a first speed command signal and a first ground speed signal;
generate a first engine speed command signal based on the first
speed error; send the first engine speed command signal to the
engine; compare the first speed error to an upper threshold; set a
brake command signal to an engagement value when a magnitude of the
first speed error is greater than a magnitude of the upper
threshold; engage the brake in response to setting the brake
command signal to the engagement value; and increase a speed of the
engine in response to the first engine speed command signal while
the brake command signal is set to the engagement value.
Inventors: |
Ngo; Khanh; (Peoria, IL)
; Ryerson; Cody; (Peoria, IL) ; Fossum;
Joshua; (Peoria, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Caterpillar Inc. |
Peoria |
IL |
US |
|
|
Assignee: |
Caterpillar Inc.
Peoria
IL
|
Family ID: |
55963119 |
Appl. No.: |
14/722831 |
Filed: |
May 27, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60L 15/2063 20130101;
B61C 15/00 20130101; B60W 2710/0644 20130101; Y02T 10/70 20130101;
B60L 2260/40 20130101; B60W 30/188 20130101; B60W 2510/0604
20130101; B60W 2510/0657 20130101; Y02T 10/64 20130101; B60W
30/18063 20130101; B60W 10/06 20130101; B60L 2200/26 20130101; B60W
10/184 20130101; B60L 50/10 20190201; B60L 2250/26 20130101; B60L
2240/441 20130101; B60L 15/10 20130101; B60W 2510/0638 20130101;
Y02T 10/72 20130101; B60L 2240/12 20130101 |
International
Class: |
B60W 30/188 20060101
B60W030/188; B60W 10/184 20060101 B60W010/184; B61C 15/00 20060101
B61C015/00; B60W 10/06 20060101 B60W010/06 |
Claims
1. A drivetrain system for a machine, the drivetrain system
comprising: an engine operatively coupled to means for propelling
the machine over a work surface; a brake operatively coupled to the
means for propelling the machine over the work surface; and a
controller operatively coupled to the engine and the brake, the
controller being configured to: generate a first speed error based
on a first speed command signal and a first ground speed signal;
generate a first engine speed command signal based on the first
speed error; send the first engine speed command signal to the
engine; compare the first speed error to an upper threshold; set a
brake command signal to an engagement value when a magnitude of the
first speed error is greater than a magnitude of the upper
threshold; engage the brake in response to setting the brake
command signal to the engagement value; and increase a speed of the
engine in response to the first engine speed command signal while
the brake command signal is set to the engagement value.
2. The system of claim 1, wherein the controller is further
configured to: generate a second speed error based on a second
speed command signal and a second ground speed signal; generate a
second engine speed command signal based on the second speed error;
send the second engine speed command signal to the engine; compare
the second speed error to a lower threshold; set the brake command
signal to a disengagement value when a magnitude of the second
speed error is less than a magnitude of the lower threshold;
disengage the brake in response to setting the brake command signal
to the disengagement value; and adjust a speed of the engine in
response to the second engine speed command signal while the brake
command signal is set to the disengagement value.
3. The system of claim 1, further comprising a throttle input
device operatively coupled to the controller, wherein the
controller is further configured to: generate a fuel command signal
based on a throttle setting of the machine; and override the fuel
command signal with the first engine speed command signal.
4. The system of claim 2, wherein a value of the upper threshold
equals a value of the lower threshold.
5. The system of claim 2, wherein a magnitude of the upper
threshold is greater than a magnitude of the lower threshold.
6. The system of claim 2, wherein a value of the first ground speed
signal equals a value of the second ground speed signal, and a
value of the first speed command signal does not equal a value of
the second speed command signal.
7. The system of claim 2, wherein a value of the first ground speed
signal does not equal a value of the second ground speed signal,
and a value of the first speed command signal equals a value of the
second speed command signal.
8. The system of claim 1, wherein the first speed command signal
corresponds to a desired ground speed of the machine.
9. The system of claim 1, wherein the first engine speed command
signal is contained in a speed data field of a Torque/Speed Control
#1 (TSC1) message of an SAE J1939 data bus communication
standard.
10. The system of claim 1, wherein the controller is further
configured to determine the first engine speed command signal with
a PID controller.
11. The system of claim 1, wherein a value of the first speed
command signal is lower than a steady-state idle ground speed of
the machine.
12. The system of claim 2, wherein the controller is further
configured to adjust at least one of the upper threshold and the
lower threshold based on a user input.
13. A method for controlling a ground speed of a machine, the
method comprising: generating a first speed error based on a first
speed command signal and a first ground speed signal; generating a
first engine speed command signal based on the first speed error;
sending the first engine speed command signal from an engine speed
controller to an engine of the machine; comparing the first speed
error to an upper threshold via a brake controller; setting a brake
command signal to an engagement value, via the brake controller,
when a magnitude of the first speed error is greater than a
magnitude of the upper threshold; engaging a brake of the machine
in response to the setting the brake command signal to the
engagement value; and increasing a speed of the engine in response
to the first engine speed command signal while the brake command
signal is set to the engagement value.
14. The method of claim 13, further comprising: generating a second
speed error based on a second speed command signal and a second
ground speed signal; generating a second engine speed command
signal based on the second speed error; sending the second engine
speed command signal from the engine speed controller to the engine
of the machine; comparing the second speed error to a lower
threshold via the brake controller; setting the brake command
signal to a disengagement value, via the brake controller, when a
magnitude of the second speed error is less than a magnitude of the
lower threshold; disengaging the brake of the machine in response
to the setting the brake command signal to the disengagement value;
and adjusting a speed of the engine in response to the second
engine speed command signal while the brake command signal is set
to the disengagement value.
15. The method of claim 13, further comprising: generating a fuel
command signal based on a throttle setting of the machine, via the
engine speed controller; and overriding the fuel command signal
with the first engine speed command signal.
16. The method of claim 14, wherein a value of the upper threshold
equals a value of the lower threshold.
17. The method of claim 14, wherein a magnitude of the upper
threshold is greater than a magnitude of the lower threshold.
18. The method of claim 13, wherein the first engine speed command
signal is contained in a speed data field of a Torque/Speed Control
#1 (TSC1) message of an SAE J1939 data bus communication
standard.
19. The method of claim 13, wherein a value of the first speed
command signal is lower than a steady-state idle ground speed of
the machine.
20. An article of manufacture comprising non-transitory
machine-readable media having instructions encoded thereon for
causing a controller to: generate a first speed error based on a
first speed command signal and a first ground speed signal;
generate a first engine speed command signal based on the first
speed error; send the first engine speed command signal from an
engine speed controller to an engine of a machine; compare the
first speed error to an upper threshold via a brake controller; set
a brake command signal to an engagement value, via the brake
controller, when a magnitude of the first speed error is greater
than a magnitude of the upper threshold; engage a brake of the
machine in response to setting the brake command signal to the
engagement value; and increase a speed of the engine in response to
the first engine speed command signal while the brake command
signal is set to the engagement value.
Description
TECHNICAL FIELD
[0001] This patent disclosure relates generally to a system and
method for controlling a ground speed of a machine, and more
particularly, to a system and method for controlling a ground speed
of a locomotive using a controller operatively coupled to an engine
and brake system.
BACKGROUND
[0002] Closed-loop control is known for controlling the speed of
machine transmission outputs, such as the ground speed of machines,
swing speeds of machine components, or other speed-controlled
machine elements. Generally, closed-loop speed control operates by
minimizing a difference between a desired speed and an actual speed
of the machine element in question. Often, the actual speed of the
controlled entity is fed back into a controller, which may
implement a proportional-integral-derivative (PID) control scheme,
to generate a power command signal. When applied, the power command
signal may reduce the difference between the actual speed and the
desired speed.
[0003] The controller typically generates the power command signal
based on various gain parameters. While higher gains initially
result in a more rapid response to speed change inputs, these gains
may result in instability, such as continuous overshooting or
ringing. For more stable speed control, a system may benefit from
lower gain values. However, the resultant system may become less
responsive to operator control inputs, which can lead to operator
impatience and dissatisfaction, and in some cases, may also result
in operator errors and inefficiencies.
[0004] U.S. Patent Application Publication No. 2014/0316664 (the
'664 publication), entitled "Aggressive and Stable Speed Control,"
purports to address the problems of stability in control systems.
The system described in the '664 publication includes a PID control
module configured to periodically change the proportional,
derivative, and integral gain values based on a speed error value.
However, the system described in the '664 publication may not be
well suited to speed control for some types of machines or some
machine operating conditions. Accordingly, there is a need for
improved ground speed control systems and methods to address the
aforementioned problems and/or other problems known in the art.
[0005] It will be appreciated that this background description has
been created to aid the reader, and is not to be taken as a
concession that any of the indicated problems were themselves known
in the art.
SUMMARY
[0006] According to an aspect of the disclosure, a drivetrain
system for a machine comprises an engine operatively coupled to
means for propelling the machine over a work surface, a brake
operatively coupled to the means for propelling the machine over
the work surface, and a controller operatively coupled to the
engine and the brake. The controller is configured to generate a
first speed error based on a first speed command signal and a first
ground speed signal, generate a first engine speed command signal
based on the first speed error, send the first engine speed command
signal to the engine, compare the first speed error to an upper
threshold, set a brake command signal to an engagement value when a
magnitude of the first speed error is greater than a magnitude of
the upper threshold, engage the brake in response to setting the
brake command signal to the engagement value, and increase a speed
of the engine in response to the first engine speed command signal
while the brake command signal is set to the engagement value.
[0007] According to another aspect of the disclosure, a method for
controlling a ground speed of a machine comprises generating a
first speed error based on a first speed command signal and a first
ground speed signal, generating a first engine speed command signal
based on the first speed error, sending the first engine speed
command signal from an engine speed controller to an engine of the
machine, comparing the first speed error to an upper threshold via
a brake controller, setting a brake command signal to an engagement
value, via the brake controller, when a magnitude of the first
speed error is greater than a magnitude of the upper threshold,
engaging a brake of the machine in response to the setting the
brake command signal to the engagement value, and increasing a
speed of the engine in response to the first engine speed command
signal while the brake command signal is set to the engagement
value.
[0008] According to yet another aspect of the disclosure, an
article of manufacture comprises non-transient machine-readable
instructions encoded thereon for causing a controller to generate a
first speed error based on a first speed command signal and a first
ground speed signal, generate a first engine speed command signal
based on the first speed error, send the first engine speed command
signal from an engine speed controller to an engine of a machine,
compare the first speed error to an upper threshold via a brake
controller, set a brake command signal to an engagement value, via
the brake controller, when a magnitude of the first speed error is
greater than a magnitude of the upper threshold, engage a brake of
the machine in response to setting the brake command signal to the
engagement value, and increase a speed of the engine in response to
the first engine speed command signal while the brake command
signal is set to the engagement value.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a side view of a machine, according to an aspect
of the disclosure.
[0010] FIG. 2 is a schematic diagram of a drivetrain system,
according to an aspect of the disclosure.
[0011] FIG. 3 is a schematic diagram of a controller, according to
an aspect of the disclosure.
[0012] FIG. 4 is a flowchart for a process of the drivetrain
system, according to an aspect of the disclosure.
[0013] FIG. 5 is a flowchart for a process of an engine speed
controller, according to an aspect of the disclosure.
DETAILED DESCRIPTION
[0014] Aspects of the disclosure will now be described in detail
with reference to the drawings, wherein like reference numbers
refer to like elements throughout, unless specified otherwise.
[0015] FIG. 1 illustrates a machine 100, according to an aspect of
the disclosure. The machine 100 can be a railroad vehicle; an
"over-the-road" vehicle, such as a truck used in transportation; an
off-road vehicle; or may be any other type of machine that performs
an operation associated with an industry such as mining,
construction, farming, transportation, or any other industry known
in the art. For example, the machine 100 may be an off-highway
truck, a railroad locomotive, and earth-moving machine, such as a
wheel loader, an excavator, a dump truck, a backhoe, a motor
grader, a material handler, or the like. The specific machine 100
illustrated in FIG. 1 is a railroad locomotive.
[0016] The machine 100 includes an engine 102 operatively coupled
to a controller 104. The engine 102 may be an internal combustion
engine including a reciprocating piston engine, such as a
compression ignition engine or a spark ignition engine, a
turbomachine such as a gas turbine, combinations thereof, or any
other internal combustion engine known in the art.
[0017] The engine 102 may be configured to generate a mechanical
output that drives a main generator 108 to produce electric power.
The electric power from the main generator 108 may be used to
propel the machine 100 along a work surface 110 via one or more
traction motors 112 operatively coupled with wheels 114. The
traction motors 112 and/or wheels 114 may be operatively coupled to
brakes 116 to provide a retarding force on the traction motors 112
and/or wheels 114. In other aspects, the engine 102 may also be
operatively coupled to other means known in the art for propelling
the machine 100 across the work surface 110. The electric power
from the main generator 108 may also be directed to other auxiliary
loads within the machine 100, such as control systems, heating,
lights, fans, etc.
[0018] The machine 100 may include an operator cab 118 that
includes one or more control input devices 120 that are operatively
coupled to the controller 104. The control input devices 120 may
include manual control input devices configured to communicate
manual control inputs form an operator in the cab 118 to the
controller 104; automatic control input devices such as open-loop
controllers, closed-loop controllers, programmable logic
controllers, and the like; remote control input devices such as
wired or wireless telemetry devices; combinations thereof; or any
other control input device known in the art.
[0019] The machine 100 may also include at least one engine speed
sensor 122 in electronic communication with the controller 104. The
engine speed sensor 122 may be operatively coupled to the engine
102 and configured to determine a speed of the engine 102, such as
a crankshaft speed of the engine 102, a camshaft speed of the
engine 102, or a combination thereof. The engine speed sensor 122
may be a crankshaft position sensor, a camshaft position sensor, a
Hall effect sensor, an optical sensor, an inductive sensor, or
another type of sensor known in the art. The engine speed sensor
122 may periodically provide an engine speed signal 238 (see FIG.
3) to controller 104. For example, the engine speed sensor 122 may
output the current engine speed to the controller 104 every 20
milliseconds. The engine speed sensor 122 may also be configured to
send an engine speed signal 238 when it receives a request signal
from the controller 104.
[0020] The machine 100 may also include at least one ground speed
sensor 124 in electronic communication with the controller 104. The
ground speed sensor 124 may be operatively coupled to the traction
motors 112 and/or wheels 114 and configured to determine a ground
speed of the machine 100. The ground speed sensor 124 may be a
wheel speed sensor including bearingless wheelset speed sensors,
optical sensors, magnetic sensors, or other sensors known in the
art. The ground speed sensor 124 may also periodically provide a
ground speed signal 216 (see FIG. 2) to the controller 104. The
ground speed sensor 124 may also be configured to send a ground
speed signal 216 when it receives a request signal from the
controller 104.
[0021] FIG. 2 is a schematic diagram of a drivetrain control system
200, according to an aspect of the disclosure. The drivetrain
control system 200 may include a control module 202 operatively
connected to the engine 102. The control module 202 may include an
engine speed controller 204 and a brake controller 206. The
drivetrain control system 200 may also include a throttle 208 and a
vehicle dynamics module 210 operatively coupled to the engine 102.
The control module 202, the engine speed controller 204, the brake
controller 206, and the vehicle dynamics module 210 may be modules
programmed on and/or in communication with the controller 104.
[0022] The drivetrain control system 200 may receive a speed
command signal 212 at a summation block 214. The speed command
signal 212 may represent a desired speed value of the machine 100
across the work surface 110. The speed command signal 212 may be
superimposed at the summation block 214 with a ground speed signal
216 generated by the vehicle dynamics module 210. According to an
aspect of the disclosure, the summation block 214 may inverse a
sign of the ground speed signal 216 before superimposing the ground
speed signal 216 with the speed command signal 212. The vehicle
dynamics module 210 may be operatively connected to one or more
ground speed sensors 124 in order to determine the ground speed
signal 216.
[0023] The summation block 214 determines a speed error signal 218
from the speed command signal 212 and the ground speed signal 216.
The speed error signal 218 may represent the difference between the
current ground speed of the machine 100 and a desired ground speed
of the machine 100. FIG. 2 illustrates that the speed error signal
218 is generated by superimposing the speed command signal 212 with
the inverse of the ground speed signal 216. In other aspects, the
speed error signal 218 may be generated by other combinations of
the speed command signal 212 and ground speed signal 216. Further,
it will be appreciated that superposition of the speed command
signal 212 and the inverse of the ground speed signal 216 may be
achieved by direct superposition of analog signals, or arithmetic
operations based on magnitudes of analog signals, digital signals,
or combinations thereof, for example.
[0024] The speed error signal 218 may be received by the engine
speed controller 204, and the engine speed controller 204 may
generate an engine speed command signal 220 based on the speed
error signal 218. The engine speed command signal 220 may
correspond to a desired speed of the engine 102, such as a
particular revolutions per minute (RPM) of a crankshaft and/or a
camshaft of the engine 102. The process for generating the engine
speed command signal 220 is subsequently described in more detail
with respect to FIG. 3. The engine speed command signal 220 is
received by the engine 102 and used to control a speed of the
engine 102.
[0025] As mentioned previously, a throttle 208 may be operatively
coupled to the engine 102 and configured to send a fuel command
signal 222 to the engine 102. The fuel command signal 222 may
regulate a quantity of fuel injected into the engine 102. The fuel
command signal 222 may be used to control a speed of the engine
102. When the drivetrain control system 200 is active, the engine
speed command signal 220 may override the fuel command signal
222.
[0026] The speed error signal 218 may also be received at the brake
controller 206. The brake controller 206 may generate a brake
command signal 224 from the speed error signal 218. The brake
command signal 224 may correspond to an engagement value or a
disengagement value configured to engage or disengage,
respectively, the brakes 116. The brake command signal 224 may also
correspond to a variable braking force signal. For example, a
magnitude of the braking force applied by the brakes 116 may be
proportional to a magnitude of the brake command signal 224.
Alternatively, the brake controller 206 may toggle the braking
force between two discrete states, namely a disengaged state and an
engaged state. The process for generating the brake command signal
224 is subsequently described in more detail with respect to FIG.
3. The brake command signal 224 is then sent from the brake
controller 206 to the vehicle dynamics module 210 to control the
brakes 116.
[0027] The ground speed of the machine 100 may change due to the
engine speed command signal 220 and the brake command signal 224.
For example, if the engine speed command signal 220 is greater than
a current engine speed of the engine 102 and the brake command
signal 224 is set at a disengagement value, the ground speed of the
machine 100 may increase as a result of increased engine 102 power
output, for example. Alternatively, if the engine speed command
signal 220 is less than a current engine speed of the engine 102
and the brake command signal 224 is set at an engagement value, the
ground speed of the machine 100 may decrease as a result of a
retarding force of the brakes 116, a decrease in engine 102 power
output, or combinations thereof. The vehicle dynamics module 210
may determine the ground speed of the machine 100 across the work
surface 110 using ground speed sensors 124 and send the ground
speed signal 216 to the summation block 214.
[0028] FIG. 3 is a schematic diagram of the control module 202,
according to an aspect of the disclosure. As described previously,
the control module 202 includes an engine speed controller 204 and
a brake controller 206. The engine speed controller 204 may include
a PD control module 226 and a variable gain module 228. The PD
control module 226 may receive the speed error signal 218 from the
summation block 214. The speed error signal 218 may be scaled by a
proportional gain (Kp) 230 at the PD control module 226. The speed
error signal 218 may also be scaled by a derivative gain (Kd) 232
at the PD control module 226. The proportional gain 230 and the
derivative gain 232 may be stored in a memory of the control module
202. Further, the proportional gain 230 and the derivative gain 232
may be configured by a user. In other aspects, the control module
202 may determine the proportional gain 230 and the derivative gain
232 based on various parameters of the machine 100. Based on both
the proportional gain 230 and derivative gain 232, the PD control
module 226 may generate an adjusted speed error signal 234. In
further aspects, the PD control module 226 may be a PID controller
that is configured to generate the adjusted speed error signal 234
with an integral gain (Ki) in addition to the proportional gain
230, the derivative gain 232, or combinations thereof.
[0029] The variable gain module 228 may receive the adjusted speed
error signal 234 from the PD control module 226. The variable gain
module 228 may adjust the adjusted speed error signal 234 into an
engine speed adjustment signal 236 that may be processed by the
engine 102. According to an aspect of the disclosure, the adjusted
speed error signal 234 corresponds to a ground speed error of the
machine 100 and has units of speed. The engine speed adjustment
signal 236 may have units of engine speed, such as revolutions per
minute (RPM). The variable gain module 228 may change the units of
the adjusted speed error signal 234 to a corresponding engine speed
value. This scaling may be based on a number of calibration factors
of the machine 100, including a gear ratio, a machine load, or
other properties of the machine 100.
[0030] The engine speed adjustment signal 236 may be superimposed
with an engine speed signal 238 at the summation block 240 to
generate the engine speed command signal 220. As mentioned
previously with respect to FIG. 2, the engine speed command signal
220 may be a desired engine speed of the engine 102. The engine
speed signal 238 may be received from an engine speed sensor 122
operatively connected to the engine 102. The engine speed command
signal 220 may be contained in a speed data field of a Torque/Speed
Control #1 (TSC1) message of an SAE J1939 data bus communication
standard. The engine speed command signal 220 may be subsequently
sent to the engine 102 to control the engine speed.
[0031] As mentioned previously, the control module 202 in FIG. 3
further includes a brake controller 206. Similar to the engine
speed controller 204, the brake controller 206 may receive the
speed error signal 218 from the summation block 214. An inverse
gain module 242 may be applied to the speed error signal 218 to
generate a modified speed error signal 244. The modified speed
error signal 244 may be received at the brake controller 206. In
other aspects, the inverse gain module 242 may not be implemented.
The brake controller 206 may also receive an upper threshold value
246 and a lower threshold value 248. The brake controller 206 may
be configured to generate the brake command signal 224 based on a
comparison between the modified speed error signal 244 and the
upper/lower threshold values 246, 248. The brake controller 206 may
set the brake command signal 224 to an engagement value when a
magnitude of the modified speed error signal 244 is greater than a
magnitude of the upper threshold 246. The brake controller 206 may
set the brake command signal 224 to a disengagement value when a
magnitude of the modified speed error signal 244 is less than a
magnitude of the lower threshold 248. Further, the brake command
signal 224 may remain unchanged from the previous value when the
magnitude of the modified speed error 244 is between the lower
threshold 248 and the upper threshold 246.
[0032] By having an upper threshold 246 greater than the lower
threshold 248, the drivetrain control system 200 may effect a
hysteresis loop that may help avoid instability potentially caused
by switching the brake ON and OFF too rapidly. The upper threshold
value 246 and lower threshold value 248 may be pre-programmed
values within the control module 202. In other aspects, the upper
threshold value 246 and lower threshold value 248 may be configured
based on user input received at the control input devices 120.
INDUSTRIAL APPLICABILITY
[0033] The present disclosure is applicable to apparatus and
methods for controlling a ground speed of a machine 100, and more
particularly, to a system and method for controlling a ground speed
of a locomotive using a controller operatively coupled to an engine
102 and brake system 116. Referring to FIG. 1, the machine 100 may
be configured to be propelled along a work surface 110 via one or
more traction motors 112 associated with wheels 114. The traction
motors 112 may be directly or indirectly powered by mechanical
output from the engine 102. It will be appreciated that the
traction motors 112 may be indirectly powered by mechanical output
form the engine 102 when the traction motors 112 receive electrical
power from a generator that is driven by shaft power from the
engine 102, for example.
[0034] The machine 100 may have a steady-state idle ground speed
that corresponds to the engine 102 being operated at an idle
condition and the brakes 116 being disengaged. For example, the
machine 100 may have a steady-state idle ground speed of 5 km/hr
when the engine 102 idles at 700 rpm and the brakes 116 are
disengaged.
[0035] In some applications, it may be desirable to control the
ground speed of the machine 100 to a value below the steady-state
idle ground speed. In the previous example, it may be desirable to
control a ground speed of the machine 100 to a ground speed value
of 4 km/hr, which is less than the exemplary idle ground speed of 5
km/hr. Accordingly, to control the ground speed of the machine 100
below the steady-state ground speed, it may be desirable to set the
brake command signal 224 to an engagement value and increase the
engine speed of the machine 100 until the desired ground speed is
reached.
[0036] FIG. 4 is a flowchart of a process 400 for the drivetrain
control system 200, according to an aspect of the disclosure. The
process 400 may be executed by the controller 104. The process 400
starts at step 402. In step 404, a speed error signal 218 is
determined. As illustrated in FIG. 3, the speed error signal 218
may be determined based on a difference between the speed command
signal 212 and the ground speed signal 216 at the summation block
214.
[0037] In step 406, the brake controller 206 determines whether a
magnitude of the speed error signal 218 is greater than a magnitude
of the upper threshold value 246. If the magnitude of the speed
error signal 218 is greater than the magnitude of the upper
threshold value 246, the process 400 proceeds to step 408, and the
brake controller 206 sets the brake command signal 224 to an
engagement value. If the magnitude of the speed error signal 218 is
less than the magnitude of the upper threshold value 246, the
process 400 proceeds to step 410. At step 410, the brake controller
206 determines whether the magnitude of the speed error signal 218
is less than a magnitude of the lower threshold value 248. If a
magnitude of the speed error signal 218 is less than the magnitude
of the lower threshold value 248, the process 400 proceeds to step
412, and the brake controller 206 sets the brake command signal 224
to a disengagement value. If the magnitude of the speed error
signal 218 is not less than the magnitude of the lower threshold
value 248, the process proceeds to step 414, and the brake
controller 206 may not change the brake command signal 224. In
other aspects, the brake controller 206 may complete step 410
before step 406.
[0038] From step 408, step 412, and/or step 414, the controller 104
may proceed to step 416. At step 416, the engine speed controller
204 generates the engine speed command signal 220. The process for
generating the engine speed command signal 220 has been described
previously with reference to FIG. 3. In other aspects, step 416 may
be completed independently from steps 404-414. For example, the
controller 104 may generate the engine speed command signal 220
before or while generating the brake command signal 224. The
process 400 then proceeds to step 418. At step 418, the ground
speed of the machine 100 may be adjusted by the engine speed
command signal 220, the brake command signal 224, or both.
Accordingly, the controller 104 may engage the brakes 116 and
simultaneously increase or decrease a speed of the engine 102 when
the target ground speed of the machine 100 is less than a
steady-state idle ground speed of the machine 100. Following step
418, the process 400 ends at step 420.
[0039] FIG. 5 is a flowchart of a process 500 for the engine speed
controller 204, according to an aspect of the disclosure. The
process 500 starts at step 502. In step 504, a speed error signal
218 may be received at a PD control module 226. As illustrated in
FIG. 3, the speed error signal 218 may be determined based on a
difference between the speed command signal 212 and the ground
speed signal 216 at the summation block 214. At step 506, the
engine speed controller 204 applies the proportional gain 230 and
the derivative gain 232 to the speed error signal 218 to generate
the adjusted speed error signal 234.
[0040] At step 508, the variable gain module 228 may apply various
parameters to the adjusted speed error signal 234 to generate an
engine speed adjustment signal 236. At step 510, the engine speed
command signal 220 may be generated by superimposing the engine
speed adjustment signal 236 with an engine speed signal 238.
Following step 510, the process 500 ends at step 512.
[0041] Process 400 and process 500 may be executed by the
controller 104. As will be appreciated, the controller 104 may be a
solid state device having a processor and optionally other
resources such as memory, converters, or the like to implement one
or more control functions. The controller 104 may receive one or
more signal and/or command inputs, which may be digital or analog,
and provide one or more output control signals in keeping with the
control process implemented by the controller 104.
[0042] As used herein, the controller 104 may be a processor-based
device that operates by executing computer-executable instructions
read from a non-transitory computer-readable medium. The
non-transitory computer-readable medium may be a hard drive, flash
drive, RAM, ROM, optical memory, magnetic memory, combinations
thereof, or any other machine-readable medium known in the art. The
controller 104 may be single device or a plurality of devices.
Further, the controller 104 may be a dedicated controller or may be
implemented within an existing controller also serving one or more
other functions, e.g., engine or machine speed control. It will be
appreciated that any of the processes or functions described herein
may be effected or controller by the controller 104.
[0043] It will be appreciated that the foregoing description
provides examples of the disclosed system and technique. However,
it is contemplated that other implementations of the disclosure may
differ in detail from the foregoing examples. All references to the
disclosure or examples thereof are intended to reference the
particular example being discussed at that point and are not
intended to imply any limitation as to the scope of the disclosure
more generally. All language of distinction and disparagement with
respect to certain features is intended to indicate a lack of
preference for those features, but not to exclude such from the
scope of the disclosure entirely unless otherwise indicated.
[0044] Recitation of ranges of values herein are merely intended to
serve as a shorthand method of referring individually to each
separate value falling within the range, unless otherwise indicated
herein, and each separate value is incorporated into the
specification as if it were individually recited herein. All
methods described herein can be performed in any suitable order
unless otherwise indicated herein or otherwise clearly contradicted
by context.
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