U.S. patent application number 10/931464 was filed with the patent office on 2006-03-02 for systems and methods for control of vehicle electrical generator.
Invention is credited to Toufic M. Huazi, Nick S. Kapsokavathis, Chandra S. Namuduri, Kenneth J. Shoemaker, David W. Walters.
Application Number | 20060043939 10/931464 |
Document ID | / |
Family ID | 35942157 |
Filed Date | 2006-03-02 |
United States Patent
Application |
20060043939 |
Kind Code |
A1 |
Namuduri; Chandra S. ; et
al. |
March 2, 2006 |
SYSTEMS AND METHODS FOR CONTROL OF VEHICLE ELECTRICAL GENERATOR
Abstract
Systems, methods and devices are described for controlling a
vehicle electrical generator. A regulator for controlling a
generator in response to an input signal received from a control
module suitably includes a discriminator module, a processing
module and a switching circuit. The discriminator determines
whether the regulator is operating in voltage or torque control
mode. If the input signal is a voltage control, the output
generator produces a modulation signal to produce a desired voltage
between two battery terminals. If the input signal is a torque
control, the output generator produces one or more modulation
signals (e.g. pulse width modulation signals) to control the torque
of the generator. The modulation signals are applied across a field
coil or other controllable element of the generator by a switching
circuit that applies positive and/or negative voltage from the
battery terminals as appropriate.
Inventors: |
Namuduri; Chandra S.; (Troy,
MI) ; Kapsokavathis; Nick S.; (Shelby Township,
MI) ; Huazi; Toufic M.; (Troy, MI) ;
Shoemaker; Kenneth J.; (Highland, MI) ; Walters;
David W.; (Sterling Heights, MI) |
Correspondence
Address: |
General Motors Legal Staff;300 Renaissance Center
MC 482-C23-B21
P.O. Box 300
Detroit
MI
48265
US
|
Family ID: |
35942157 |
Appl. No.: |
10/931464 |
Filed: |
August 31, 2004 |
Current U.S.
Class: |
322/23 |
Current CPC
Class: |
H02P 9/305 20130101 |
Class at
Publication: |
322/023 |
International
Class: |
H02H 7/06 20060101
H02H007/06; H02P 9/00 20060101 H02P009/00; H02P 11/00 20060101
H02P011/00 |
Claims
1. A regulator for controlling a generator having a controllable
element in response to an input signal received from a control
module, the regulator comprising: a discriminator configured to
determine whether the input signal is a voltage control or a torque
control; a processing module configured to convert the input signal
to a modulation signal using a first conversion technique if the
input signal is a voltage control and a second conversion technique
different from the first conversion technique if the input signal
is a torque control; and a switching circuit configured to modulate
the controllable element of the generator in response to the
modulation signal to thereby control the generator.
2. The regulator of claim 3, wherein the discriminator is a
frequency discriminator.
3. A regulator for controlling a generator having a controllable
element in response to an input signal received from a control
module, the regulator comprising: a discriminator configured to
determine whether the input signal is a voltage control or a torque
control; a processing module configured to convert the input signal
to a modulation signal using a first conversion technique if the
input signal is a voltage control and a second conversion technique
different from the first conversion technique if the input signal
is a torque control; and a switching circuit configured to modulate
the controllable element of the generator in response to the
modulation signal to thereby control the generator, wherein the
switching circuit comprises: a first switch operatively located
between a first reference voltage and a first terminal of the
controllable element; a second switch operatively located between a
second reference voltage and a second terminal of the controllable
element; a first uni-directionally conducting device operatively
located between the first switch and the second reference voltage;
and a second uni-directionally conducting device operatively
located between the second switch and the first reference
voltage.
4. The regulator of claim 3 wherein the first and second switches
are transistors.
5. The regulator of claim 4 wherein the modulation signal comprises
a first portion provided to the first switch and a second portion
provided to the second switch.
6. A regulator for controlling a vehicle alternator having a field
coil to produce a desired voltage between a first and a second
battery terminal in response to an input signal received from a
control module, the regulator comprising: an input port configured
to receive the input signal; a discriminator module configured to
produce a mode selection signal indicating whether the input signal
is a voltage control or a torque control; a processing module
configured to convert the input signal to a first modulation signal
and a second modulation signal different from the first conversion
technique using a conversion routine selected in response to the
mode selection signal; and a switching circuit configured to
modulate the controllable element of the generator in response to
the first and second modulation signals to thereby control the
generator, wherein the switching circuit comprises: a first
transistor operatively located between the first battery terminal
and a first terminal of the field coil element and operable to
couple the first terminal of the field coil to the first battery
terminal in response to the first modulation signal; a second
transistor operatively located between the second battery terminal
and a second terminal of the field coil and operable to couple the
second terminal of the field coil to the second battery terminal in
response to the second modulation signal; a first diode operatively
located between the first transistor and the second battery
terminal; and a second diode operatively located between the second
transistor and the first battery terminal.
7. The regulator of claim 6 wherein the switching circuit is
further configured to provide a positive voltage across the field
coil when the first and second transistors are active, and to
provide a negative voltage across the field coil when the first and
second transistors are inactive.
8. A generator assembly for a vehicle having an engine, a battery
having first and second battery terminals with a battery voltage
therebetween, and a control module configured to produce an input
signal, the generator assembly comprising: an alternator configured
to convert mechanical energy from the engine to electrical energy,
wherein the alternator comprises a controllable element; a
rectifier configured to convert the electrical energy from the
alternator to a direct current (DC) voltage applied across the
first and second battery terminals; and a regulator comprising: a
discriminator configured to determine whether the input signal is a
voltage control or a torque control; a processing module configured
to convert the input signal to a modulation signal using a first
conversion technique if the input signal is a voltage control and a
second conversion technique different from the first conversion
technique if the input signal is a torque control; and a switching
circuit configured to modulate the controllable element of the
alternator in response to the modulation signal by switchably
applying the battery voltage from the first and second battery
terminals to the controllable element to thereby control the
generator.
9. The generator assembly of claim 8 wherein the switching circuit
is further configured to temporarily reverse the polarity of the
battery voltage applied across the controllable element when the
input signal is a torque control.
10. The generator assembly of claim 8 wherein the switching circuit
comprises: a first transistor operatively located between the first
battery terminal and a first terminal of the controllable element
and operable to couple the first terminal of the controllable
element to the first battery terminal in response to the first
modulation signal; a second transistor operatively located between
the second battery terminal and a second terminal of the
controllable element and operable to couple the second terminal of
the controllable element to the second battery terminal in response
to the second modulation signal; a fist uni-directionally
conducting device operatively located between the first transistor
and the second battery terminal; and a second uni-directionally
conducting device operatively located between the second transistor
and the first battery terminal.
11. A method for controlling a generator having a field coil in
response to an input signal received from a control module, the
method comprising the steps of: determining whether the input
signal is a voltage control or a torque control; converting the
input signal to a modulation signal using a first conversion
technique if the input signal is a voltage control and a second
conversion technique different from the first conversion technique
if the input signal is a torque control; and modulating the field
coil of the generator in response to the modulation signal to
thereby control the generator.
12. The method of claim 11 wherein the second conversion technique
comprises adjusting a signal frequency of the input signal to
produce the modulation signal.
13. The method of claim 12 wherein the modulation signal has a duty
cycle substantially equal to an input duty cycle of the input
signal.
14. The method of claim 11 wherein the determining step comprises
determining a frequency of the input signal.
15. The method of claim 11 wherein the determining step comprises
determining whether the input signal is the voltage control or the
torque control as a function of a speed of the generator.
16. The method of claim 11 wherein the determining step further
comprises determining whether the input signal corresponds to a
fast torque control or a normal torque control.
17. The method of claim 16 wherein the modulating step comprises
reversing the polarity of a voltage applied across the field coil
when the input signal corresponds to a fast torque control.
18. The method of claim 11 further comprising the step of
monitoring the field coil to obtain feedback data about the
generator for the control module.
19. The method of claim 11 wherein the modulating step comprises
reversing the polarity of a voltage applied across the field
coil.
20. A device for controlling a generator having a field coil in
response to an input signal received from a control module, the
device comprising: means for determining whether the input signal
is a voltage control or a torque control; means for converting the
input signal to a modulation signal using a first conversion
technique if the input signal is a voltage control and a second
conversion technique if the input signal is a torque control; and
means for modulating the field coil of the generator in response to
the modulation signal to thereby control the generator.
21. The regulator of claim 3, wherein the discriminator is a
voltage amplitude discriminator.
22. The regulator of claim 3 wherein the first and second
uni-directionally conducting devices are diodes.
23. The method of claim 11 wherein the determining step comprises
determining a voltage amplitude of the input signal.
Description
TECHNICAL FIELD
[0001] The present invention generally relates to multi-mode
control of a vehicle electrical generator, and more particularly
relates to generator systems and methods for operating in multiple
modes in response to one or more control inputs.
BACKGROUND
[0002] Conventional automobiles and other vehicles include numerous
electrical components such motors, lights, gauges and such
accessories as power windows, power locks, audio systems and the
like. Typically, such components derive electrical power from a
vehicle electrical system that includes a battery and an
alternator. The battery typically provides electrical power while
the engine is off and/or is being started; the alternator generally
converts mechanical energy from the vehicle's engine to electrical
energy that can be used to drive various electrical components
while the vehicle is running. The alternator also recharges the
battery during engine operation as appropriate.
[0003] The electrical system typically also includes a "regulator"
that controls the voltage generated by the alternator. Generally,
an engine control module (ECM) or other vehicle control device
provides a signal to the regulator that indicates a desired output
voltage. Regulator circuitry is commonly "built in" to many modern
alternators such that the alternator and regulator components are
provided within a common housing.
[0004] As the electrical demands upon the electrical system
continue to increase, however, it is desirable to provide a
generator assembly that is increasingly flexible and capable. In
particular, it is desirable to produce a vehicle generator assembly
that is capable of quickly responding to stalls or other engine
operating conditions. Further, it is desirable to control the
torque load placed on the engine by the generator assembly to
further improve engine performance and fuel economy. Furthermore,
other desirable features and characteristics will become apparent
from the subsequent detailed description and the appended claims,
taken in conjunction with the accompanying drawings and the
foregoing technical field and background.
BRIEF SUMMARY
[0005] Systems, methods and devices are described for controlling a
vehicle electrical generator. According to various exemplary
embodiments, a regulator for controlling a generator in response to
an input signal received from a control module suitably includes a
discriminator module, a processing module and a switching circuit.
The discriminator determines whether the regulator is operating in
voltage or torque control mode. If the input signal indicates a
voltage control operating mode, the output generator produces a
modulation signal to achieve a desired voltage between the battery
terminals (e.g. B+ and B-). If the input signal is a torque
control, the output generator produces one or more modulation
signals (e.g. pulse width modulation signals) to control the torque
of the generator. The modulation signals are applied across a field
coil or other controllable element of the generator by a switching
circuit that applies positive and/or negative voltage from the
battery terminals as appropriate. In various further embodiments, a
"fast torque control" may be implemented by, for example,
configuring the chopper circuit to modulate the controllable
element using voltages of opposing polarities. By directly
controlling the torque of the generator, benefits realized in
various exemplary embodiments may include improved engine
performance, improved recovery from engine stalls, reduced fuel
consumption, improved idle quality, improved vehicle emissions
and/or other benefits.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] The present invention will hereinafter be described in
conjunction with the following drawing figures, wherein like
numerals denote like elements, and:
[0007] FIG. 1 is a block diagram of an exemplary vehicle;
[0008] FIG. 2 is a block diagram of an exemplary vehicle electrical
generator with a multi-mode regulator;
[0009] FIG. 3 is a block diagram of an alternate embodiment of an
exemplary vehicle electrical generator with a multi-mode regulator;
and
[0010] FIG. 4 is a plot of exemplary results obtainable with one
embodiment of a fast torque reduction technique.
DETAILED DESCRIPTION
[0011] The following detailed description is merely exemplary in
nature and is not intended to limit the invention or the
application and uses of the invention. Furthermore, there is no
intention to be bound by any expressed or implied theory presented
in the preceding technical field, background, brief summary or the
following detailed description.
[0012] According to various exemplary embodiments, a generator
assembly that includes a regulator and an alternator is operable in
either a voltage control or a torque control mode. When the
generator is in the torque control mode, the torque load placed on
the engine due to the electrical load of the generator is suitably
controlled in response to a control signal provided by an engine
control module or other controller. Moreover, the regulator may
include switching circuitry that allows either positive or negative
voltage to be switchably applied across a controllable element of
the alternator, thereby allowing for rapid reduction of torque as
appropriate. In various further embodiments, the regulator includes
one or more discriminator modules that sense the desired operating
mode of the generator in response to a frequency of the signal
input from the controller, the operating speed of the alternator,
and/or any other appropriate factors. The torque control mode may
be used to rapidly decrease torque loads on the engine in the event
of a stall, for example, and/or may be used to improve engine
performance, reduce emissions, improve fuel economy and/or the
like.
[0013] With initial reference to FIG. 1, an exemplary vehicle 100
suitably includes an engine 102 and an electrical system that
includes a battery 106 and a generator assembly 104. Generator
assembly 104 is mechanically coupled to engine 102 via a belt 112,
chain or other coupling that facilitates transmission of rotational
energy from the engine to the electrical system for generating
electrical energy. Generator assembly 104 also receives a control
signal (L) 118 from an engine control module (ECM) or other
controller, and as described more fully below. Generator assembly
104 may also provide an optional feedback signal (F) 116 to ECM 114
as appropriate. Signals 116 and 118 may be transmitted and received
in any manner across any number of serial and/or parallel data
channels using any digital, analog, optical or other communications
protocol as appropriate.
[0014] The term "generator assembly" as used herein is intended to
broadly encompass any device or component that converts mechanical
energy to electrical energy usable by battery 106 and/or any other
electrical components within vehicle 100. Accordingly, generator
assembly 104 may include any type of generator, alternator and/or
other circuitry as appropriate. In an exemplary embodiment,
generator assembly 104 suitably includes an alternator as well as a
regulator circuit and a converter such as a rectifier circuit
capable of converting alternating current (AC) produced by the
alternator to an appropriate direct current (DC) typically used by
battery 106 and other vehicle components. Other embodiments may
include a DC generator in place of or in addition to an alternator,
thereby reducing or eliminating the need for separate AC-to-DC
conversion. Various exemplary generator assemblies 104 are
described in connection with FIGS. 2 and 3 below.
[0015] Generator assembly 104 and battery 106 each include at least
two electrical terminals as appropriate. These terminals are
typically interconnected to allow generator assembly 104 to
recharge battery 106 during operation of engine 102. FIG. 1 shows
the positive terminals (B+) interconnected by signal line 110 and
negative terminals (B-) 108, 109 each connected to the engine 102
or another object representing an electrical ground. In alternate
embodiments, the negative terminals of generator assembly 104 and
battery 106 may be interconnected. Indeed, the various components
and terminals shown in FIG. 1 may be electrically or mechanically
arranged in any manner, as will vary from embodiment to
embodiment.
[0016] In operation, then, generator assembly 104 suitably produces
an electrical output that can typically be represented as a DC
signal between two nodes 108 and 110. Because this electrical
energy is produced from mechanical energy received from engine 102
via belt 112, generator assembly 104 suitably places a torque load
upon engine 102 that is dependent upon the electrical load placed
upon the generator. More particularly, the torque load produced by
the generator assembly is a function of the DC output voltage, the
rotational speed and the current output of the generator.
Similarly, the generator output current is typically dependent upon
the battery voltage applied across the generator as well as the
speed of the generator and the amount of excitation field current
present in the generator.
[0017] Because the torque load of the generator is at least
partially dependent upon the field current of the generator,
variations in the field current can be used to control the torque
load of generator assembly 104. In practice, however, changing the
field current with a conventional voltage control signal provided
by a typical controller can be inordinately slow due to the large
leakage time constants of many conventional alternators. Various
embodiments therefore place the generator assembly into a "torque
control mode" that is capable of processing torque/current control
signals in a manner apart from the conventional voltage control
signals typically provided from ECM 114 to generator assembly
104.
[0018] With reference now to FIG. 2, an exemplary generator
assembly 200 suitably includes a regulator module 201, an
alternator 203 and a rectifier circuit 205. In the embodiment shown
in FIG. 2, generator assembly processes an input signal 202
received from a controller (e.g. ECM 114 in FIG. 1) to produce one
or more modulation signals 252, 254 which can be used to
appropriately apply the battery voltages 246, 248 across a
controllable element 226 of alternator 203. Generator assembly 200
generally corresponds to generator assembly 104 shown in FIG.
1.
[0019] Regulator module 201 (also referred to as simply "regulator"
201) is any circuit, processing module, logic or the like capable
of regulating one or more parameters or components of alternator
203. As shown in FIG. 2, regulator module suitably includes one or
more discriminator modules 206/208, a processing module 212 and
additional switching circuitry (e.g. transistors 216, 222 and
diodes 224, 218) as appropriate. In various embodiments, regulator
module 201 is implemented with a combination of discrete components
and a digital processor, although other embodiments may be
implemented with any discrete and/or integrated components, with a
microcontroller or with any other hardware and/or software
components used alone or in combination. Discriminator modules 206
and 208, for example, may be physically combined with processing
module 212 in a common chip or circuit in various alternate
embodiments, and need not be implemented as separate hardware
components.
[0020] Alternator 203 is any device capable of controllably
providing a desired electrical output. In various embodiments,
alternator 203 is any conventional Lundell machine or other vehicle
alternator having any number of electrical phases. As mentioned
below, alternate embodiments may not include an alternator 203 at
all, but may equivalently provide a DC generator, electric motor or
other device that is capable of receiving modulation signals from
regulator 201. As shown in FIG. 2, however, alternator 203 is a
conventional Lundell machine having a field coil 226 as a
controllable element and three electrical phases 228, 230, 232.
[0021] Rectifier 205 is any circuit capable of shaping or modifying
the output of alternator 203 to produce a direct current output
between two terminals 246, 248. FIG. 2 shows rectifier 205 as a
conventional diode rectifier having three electrical phases
corresponding to the three phases of alternator 203. Each phase is
shown with a pair of diodes 234 and 236, 238 and 240, 242 and 244
separating the alternator phases from the battery voltage terminals
246, 248 as appropriate. As discussed below, rectifier 205 may not
be required in all embodiments, particularly when alternator 203 is
equivalently implemented with a direct current generator, and
therefore has no need for AC-to-DC conversion.
[0022] Input signal 202 is any digital or analog signal provided to
regulator 201 by an external controller such as ECM 114 (FIG. 1).
In an exemplary embodiment, input signal 202 is a signal that
represents either a desired voltage to be applied at the output of
generator module 200 or a torque control to be applied across field
coil 226 to reduce the torque load of the generator. Input signals
202 may be provided to generator assembly 200 in any manner. In
various embodiments, signals 202 are provided via the "L" channel
118 described above, with voltage and torque controls being
provided on a common channel. Torque and voltage control signals
may be differentiated from each other in any manner, such as
through any difference in phase, frequency or magnitude, as
described more fully below.
[0023] Although either or both of the voltage and torque control
signals could be represented in any manner, an exemplary embodiment
represents the voltage control as a pulse-width modulated (PWM)
signal having a duty cycle that indicates the desired voltage. Duty
cycle variation, for example, could be used to represent the
operating voltages between desired minimum or maximum limits. In
one embodiment, duty cycles varying between about 10-90% could be
used to represent voltages across a range of about 11-15.5 volts,
for example, with duty cycles outside 10-90% being interpreted as a
default or other mode. In an exemplary default mode, the output
voltage generator module 200 is set to a predetermined value
corresponding to an internal reference voltage (e.g. a voltage of
about 13.8 volts or so). Similarly, torque control signals could be
represented in any manner. In an exemplary embodiment, the external
controller computes desired modulation signals to be applied to the
controllable element 226 of alternator 203, and produces PWM input
signals 202 having duty cycles that are at least approximately
equal to the duty cycles of the modulation signals applied, as
described more fully below. Again, other embodiments may have
widely varying operating parameters and signaling schemes.
[0024] Controller 201 suitably determines whether the input signals
202 are voltage or torque controls using any appropriate technique.
Such processing may be accomplished, for example, with an
appropriate discriminator module 208 that receives the input
signals 202, determines whether the signals correspond to voltage
or torque controls, and provides an appropriate output signal 264
to processing module 212 to indicate the "operating mode" of
regulator 201. Discriminator module 208 may also identify one or
more "sub-modes" 266 in various further embodiments. Such modes may
correspond to "fast" or "normal" torque control modes, for example,
or any other mode information that may be extracted from input
signals 202.
[0025] In an exemplary embodiment, ECM 114 suitably differentiates
torque control signals from voltage control signals by assigning
different frequencies to the two types of signals. Further, signals
202 representing a "fast" torque control mode may be assigned to a
third transmit frequency. Normal regulated voltage control (RVC)
signals, for example, could be assigned a first frequency (e.g. 128
Hz or so), with normal mode regulated torque control (RTC) signals
assigned a second frequency (e.g. 64 Hz or so) and "fast" RTC
signals assigned a third frequency (e.g. 256 Hz or so). In such
embodiments, discriminator 208 is a frequency discriminator capable
of discerning the frequency of incoming input signals 202 and of
providing corresponding output signals 264, 266 to indicate the
type of signals received to processing module 212. The exemplary
frequencies described herein are chosen somewhat arbitrarily;
alternate embodiments may represent the various operating modes
with any combinations of harmonic or non-harmonic frequencies, or
indeed may use other differentiation schemes entirely, as discussed
more fully below.
[0026] A second discriminator module 206 suitably receives input
signals 202 and provides decoding functionality as appropriate.
When input signals 202 represent RVC instructions, for example,
discriminator module 206 suitably determines the desired voltage
(Vref) 260 from the duty cycles of the PWM input signal 202. When
input signals 202 are provided in RTC mode, discriminator module
206 may similarly process signals 202 to directly determine the
duty cycle (F_duty) 262 of the modulation signals 252, 254 as
appropriate. In various further embodiments, discriminator module
206 is further configured to provide a fault indication to the
external controller in response to a fault signal 280 received from
processing module 212. This signal may represent a fault observed
in alternator 203, for example, or any other issue with generator
assembly 200 that is of interest to the external controller. Fault
signals may be transmitted in any manner; in various embodiments,
module 206 simply connects signal line "L" (line 118 in FIG. 1) to
a reference voltage (e.g. ground) until the fault is removed,
regulator 201 is reset, a period of time elapses or another
appropriate condition is met. In alternate embodiments, fault data
is provided by module 210 via signal line 204, as described below.
In still other embodiments, fault reporting to the external
controller is omitted completely, or implemented in any other
manner.
[0027] Processing module 212 is any circuit, module, logic routine
or the like capable of producing one or more modulation signals
252, 254 based upon information contained in input signals 202.
Although processing module 212 may not receive input signals 202
directly in all embodiments, module 212 suitably receives data 264,
266 from module 208 about the type of information contained within
input signals 202, and/or receives duty cycle or other encoded data
via module 206. This information is processed in any manner that is
appropriate for the embodiment and the type of data received. In
various embodiments, processing module 212 processes input signal
data with a different routine depending on whether the signal
provides RVC or RTC information. If input signals 202 indicate RVC
control mode, for example, processing module 212 suitably computes
appropriate modulation signals 252, 254 based upon the desired
reference voltage (Vref) 260 and the current generator voltage
observed between terminals 246 and 248. Appropriate modulation
signals may be obtained from a lookup table contained within module
212, for example, or may be computed using any suitable algorithm
and/or appropriate control and feedback techniques. In still other
embodiments, modulation signals 252, 254 are processed with
discrete or integrated circuitry.
[0028] If input signals 202 are identified as RTC controls,
however, processing module 212 suitably processes the data in a
different manner from that used for RVC controls. In various
embodiments, RTC controls are simply modulated instructions from
the ECM or other external controller that provide a duty cycle to
be applied to PWM modulation signals provided by processing module
212. In such cases, processing module 212 need simply determine the
duty cycle of the input signals and produce modulation signals
having the same duty cycle at the appropriate modulation frequency.
Processing module 212 may determine the input duty cycle directly,
or may receive an indication 262 of the duty cycle from module 206,
as appropriate. Other RTC signals may be encoded and/or processed
in any other manner as appropriate.
[0029] Modulation signals 252, 254 signals applied to one or more
elements in the switching circuitry to properly control any portion
of alternator 203 to produce the desired output. In various
embodiments, modulation signals 252, 254 are PWM signals that are
applied to the gate terminals of one or more transistors, relays,
switches or other appropriate devices to modulate the controllable
element 226 of alternator 203 as desired. In such embodiments, the
switching elements remain activated throughout the duration of the
duty cycle, and otherwise inactive. Accordingly, the amount of time
that one or more switching elements remains in a particular state
can be controlled by varying the duty cycle of modulation signals
252, 254.
[0030] The exemplary embodiment of switching circuitry shown in
FIG. 2 employs a conventional two-quadrant chopper circuit that
includes two MOSFET transistors 216, 218 that selectively couple
one side 256, 258 of the alternator field coil 226 to a high or low
battery voltage 246, 248 respectively. Each of the transistors 216,
218 is activated by applying one of the modulation signals 252, 254
to the transistor gate as appropriate. When transistors 216, 222
are turned "on" by modulation signals 252, 254, terminal 256 of
field coil 226 is connected to battery terminal 246 (B+), and
terminal 258 of field coil 226 is connected to battery terminal 248
(B-). When transistor 216 is turned off, terminal 256 of field coil
226 gets connected to battery terminal 248 (B-) via freewheeling
diode 218. Similarly, when transistor 222 is turned off, terminal
258 of field coil 226 gets connected to battery terminal 246 via
diode 224. Accordingly, by applying proper modulation signals 252,
254 to the gates of transistors 216, 222, the battery voltages
coupled to each side of field coil 226 can be controlled as
desired.
[0031] Various modulation and switching schemes could be formulated
in a wide array of alternate embodiments. In various embodiments,
either transistor 216, 222 is kept in a relatively constant "on"
state during normal operation and the other transistor is modulated
as desired. Whether transistor 216 or transistor 22 is kept active
in the arrangement shown in FIG. 2, voltage differences only exist
across field coil 226 when both transistors are active. For a
faster control, however, both transistors 216, 222 may be modulated
at the same time to produce voltages having opposite polarities
across field coil 226 when the transistors are "on" or "off". That
is, the polarity of the voltage applied across field coil 226 is
reversed when the transistors 216, 222 are activated or deactivated
in tandem. This "reverse" voltage effectively enables faster decay
of field current, thereby resulting in faster torque or voltage
reductions as appropriate. Accordingly, using the two quadrant
chopper circuit shown in FIG. 2, "normal" voltage or torque control
modes may be implemented by maintaining one modulation signal in a
relatively constant active state while modulating the other signal.
"Fast" control modes may be implemented by simultaneously
modulating both sides of controllable element 226.
[0032] Again, many modifications could be made to the circuitry
shown in FIG. 2 in a wide array of equivalent embodiments.
Modulation signals 252, 254 need not be applied directly to
transistors 216, 220, for example, but rather may be applied to a
driver circuit 214, 220 as shown. Such driver circuits are any
conventional bias circuits capable of placing and maintaining
transistors 216, 222 into saturation mode for the duration of the
duty cycle in modulation signals 252, 254, respectively. Further,
the N-channel enhancement mode MOSFETs shown in FIG. 2 could be
replaced with any type of FET, MOSFET, bipolar or other transistor,
or any other type of switch or relay. Diodes 218 and 224 could
similarly be implemented using transistors or other
uni-directionally conducting components or circuits. Further, some
or all of the switching circuitry could be implemented with
integrated circuitry (which may be further integrated with
processor 212 and/or modules 206, 208 as well). Accordingly, many
different circuit arrangements could be used to implement the
features described above.
[0033] In various embodiments, regulator 201 further includes an
optional field monitor module 210 for providing feedback data to
ECM 114 (FIG. 1) or another recipient for diagnostic or control
purposes as appropriate. As shown in FIG. 2, field monitor module
210 suitably receives an indication 268 of the voltage applied
across the field winding 226 of alternator 203. This voltage 268
can be used to measure the responsiveness of regulator 201, to
obtain a rough measurement of the torque load produced by
alternator 203, or for any other purposes. Feedback data may be
provided to ECM 114 via signal line 116 (FIG. 1).
[0034] With reference now to FIG. 3, an alternate embodiment of a
generator assembly 300 suitably includes a generator speed sensing
circuit 302 in place of or in addition to frequency discriminator
208. In various embodiments, torque control may be most beneficial
at low engine speeds, when torque loads are typically of greatest
concern. Accordingly, selection between torque and voltage control
modes may be made based upon the engine and/or alternator speed
rather than upon the frequency or other characteristics of incoming
input signals 202. Input signals 202 received when the alternator
speed is relatively low (e.g. less than about 2000 rpm or so),
could be readily assumed to be torque control signals, for example,
whereas input signals 202 received at higher speeds can be assumed
to be voltage controls. By determining the frequency of the
alternator rotation (which is related to the engine rotation speed
by a pulley ratio) using signal 304, module 302 may determine one
or more operating modes without the need to further analyze the
frequency or other characteristics of the input signals 202.
Alternatively, input signals may be further analyzed to determine
additional data. In the embodiment shown in FIG. 3, for example,
generator speed sensing module 302 processes signal 304 to indicate
RVC or RTC mode with signal 306, whereas frequency discriminator
module 208 suitably indicates "normal" or "fast" mode using signal
216. In embodiments wherein either "normal" or "fast" mode are not
implemented, however, either module 208 or module 302 may be
eliminated as appropriate. In still further embodiments, mode
selection signals (e.g. signals 266, 306) are produced by an ECM or
external controller and provided to regulator 201 with input
signals 202. In such embodiments, regulator 201 need not determine
mode selection information, since this data is readily available
from an external source.
[0035] Using the various concepts set forth herein, one or more
benefits may be provided to the various implementations and
embodiments. With final reference to FIG. 4, significant reductions
in torque response times can be realized using the concepts of
torque control set forth herein. FIG. 4 shows that torque fall
times have been reduced by an order of magnitude or more, thereby
resulting in improved control and fewer vehicle stalls. Moreover,
the concepts set forth herein can be used for more precise control
over engine torque management, thereby resulting in improved fuel
efficiency and emissions quality.
[0036] Although the various embodiments are most frequently
described with respect to automotive applications, the invention is
not so limited. Indeed, the concepts, circuits and structures
described herein could be readily applied in any commercial, home,
industrial, consumer electronics or other setting. The concepts
described herein could similarly be readily applied in
aeronautical, aerospace, marine or other vehicular settings as well
as in the automotive context.
[0037] While at least one exemplary embodiment has been presented
in the foregoing detailed description, a vast number of variations
exist. The various circuits described herein may be modified
through conventional electrical and, electronic principles, or may
be logically altered in any number of equivalent embodiments
without departing from the concepts described herein. Although the
present disclosure frequently refers to a Lundell machine or other
alternator, for example, the concepts of torque control discussed
herein could be readily applied to any other type of AC or DC
generator, motor or the other device having a controllable element
as described herein. Accordingly, the exemplary embodiments
described herein are intended only as examples, and are not
intended to limit the scope, applicability, or configuration of the
invention in any way. Rather, the foregoing detailed description
will provide those skilled in the art with a convenient road map
for implementing one or more exemplary embodiments. Various changes
can therefore be made in the functions and arrangements of elements
set forth herein without departing from the scope of the invention
as set forth in the appended claims and the legal equivalents
thereof.
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