Ex Parte Luedtke

Patent Trial and Appeal Board

Jan 4, 2017

13607013 (P.T.A.B. Jan. 4, 2017)

United States Patent and Trademark Office
UNITED STATES DEPARTMENT OF COMMERCE
United States Patent and Trademark Office
Address: COMMISSIONER FOR PATENTS
P.O.Box 1450
Alexandria, Virginia 22313-1450
www.uspto.gov
APPLICATION NO. FILING DATE FIRST NAMED INVENTOR ATTORNEY DOCKET NO. CONFIRMATION NO.
13/607,013 09/07/2012 Daniel Luedtke 83257363 3164
28395 7590 01/06/2017
RROOKS KTTSHMAN P C /FfTET EXAMINER
1000 TOWN CENTER DHAKAL, BICKEY
22ND FLOOR
SOUTHFIELD, MI 48075-1238 ART UNIT PAPER NUMBER
2837
NOTIFICATION DATE DELIVERY MODE
01/06/2017 ELECTRONIC
Please find below and/or attached an Office communication concerning this application or proceeding.
The time period for reply, if any, is set in the attached communication.
Notice of the Office communication was sent electronically on above-indicated "Notification Date" to the
following e-mail address(es):
docketing @brookskushman.com
PTOL-90A (Rev. 04/07)
UNITED STATES PATENT AND TRADEMARK OFFICE
BEFORE
THE PATENT TRIAL AND APPEAL BOARD
Ex parte DANIEL LUEDTKE
Appeal 2015-003605
Application 13/607,013
Technology Center 2800
Before MARK NAGUMO, WESLEY B. DERRICK, and
DEBRA L. DENNETT, Administrative Patent Judges.
NAGUMO, Administrative Patent Judge.
DECISION ON APPEAL
Daniel Luedtke (“Luedtke”) timely appeals under 35 U.S.C. § 134(a)
from the Final Rejection1 of all pending claims 1—13. We have jurisdiction.
35 U.S.C. § 6. We reverse.
1 Office action mailed 18 June 2014 (“Final Rejection”; cited as “FR”).
Appeal 2015-003605
Application 13/607,013
OPINION
A. Introduction2
The subject matter on appeal relates to the control of permanent
magnet synchronous electric motors. Such motors comprise one or more
permanent magnets in the rotor and, typically, three separate electrical
windings in the stator, each powered by alternating current voltages Va.c and
oscillating currents Ia.c that are separated by 120° in phase from one another.
(Spec. 1 [0002]).3 According to the ’013 Specification, “[t]hese winding
currents induce a rotating magnetic field which may be out of phase with the
rotor. The resulting shaft torque depends upon both the magnitude of the
magnetic field and the phase angle relative to the rotor.” (Id. ) The
Specification explains further that the strength of the permanent magnets
decreases as the temperature increases, and as a result, the current passed
through the windings of the stator to turn the rotor must be higher to
generate the same torque at higher temperatures (Spec. 6 [0017]). This
situation is illustrated in Figure 4, which is reproduced on the following
page.
2 Application 13/607,013, Electric motor temperature compensation,
filed 7 September 2012. We refer to the “’013 Specification,” which we cite
as “Spec.”
3 We refer to paragraphs as numbered in the clean copy of the Specification
including amendments filed 11 December 2008, as further amended
on 17 March 2014. It should be noted that, the amendments filed
on 17 March 2014 appear to refer to the originally filed Specification, not to
the already-amended Specification filed 11 December 2008. We trust this
discrepancy will be corrected in the event of further prosecution of this
application.
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Application 13/607,013
{Figure 4 is shown below}
{Figure 4 shows the dependence of motor operation on temperature.}
The Specification explains that, for convenience, the winding voltages
and currents can be represented by vectors with respect to a reference frame
that rotates with the rotor. In this rotating frame, the vectors have “direct
components,” Vd and Id, and “quadrature components,” Vq and Iq, that do not
oscillate based on rotor position. {Id. at 1 [0003].) Henceforth all references
to the winding voltage and current are to the direct component Id and the
quadrature component Iq, which are displayed as the horizontal and vertical
axes, respectively, in Figure 4.
According to the Specification, at the reference temperature,
curve 3224 “represents the boundary of the conditions [i.e., the direct
4 Throughout this Opinion, for clarity, labels to elements are presented in
bold font, regardless of their presentation in the original document.
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Appeal 2015-003605
Application 13/607,013
current, Id, and quadrature current, Iq] that are achievable by the inverter5 at
a particular rotor speed and bus voltage level.” (Id. at 5 [0013].) That is, the
components of the winding current are located in the region bounded to the
right and above by curve 322. {Id. at 6 [0015].) This region is called the
“field weakening region.” {Id. at [0016].) The Specification reveals further
that the most efficient operation of the motor, possible only at low torque
requests, low rotor speeds, and high bus voltages, is found for “target” Id*
and Iq* along line 318. {Id.) However, at higher torque requests, higher
rotor speeds, and lower bus voltages, operation along line 318 is not
possible. Rather, the most efficient operating point obtainable in practice is
located along curve 322 at the point of closest approach to line 318.
Curve 310 shows a constant torque corresponding to various
combinations of Id and Iq at the reference temperature. {Id. at 5 [0013].) As
shown in Figure 3 (not reproduced here), lines of larger values of constant
torque are displaced vertically, at higher values of Iq at the same value of Id.
(Id. ) Hence, at the reference temperature, the torque along line 310 is
obtained with maximum efficiency at point 430. {Id. at 7 [0017].) The
theoretical maximum efficiency of torque produced along line 310 occurs at
the intersection of curve 310 with efficiency curve 318. At higher
temperatures, because higher currents Id and Iq are required to compensate
for the weakened magnetic response of the permanent magnets, the curve of
constant torque shifts upward to dashed curve 410. (Id. ) To maintain the
motor at constant torque at higher temperatures, the controller could shift Id
5 As illustrated in Figure 1 (not reproduced here), inverter 132 is a
component of the system that converts direct current on bus 134 to
alternating current to power motor 124.
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Application 13/607,013
and Iq along curve 322 to point 432. (Id.) According to the convention
adopted by Luedtke, “[i]f I*d is negative, then increasing IA makes IA less
negative and decreasing IA makes IA more negative.” (Id. at 8 [0018].)
Thus, reaching point 432 requires that Id be decreased (i.e., made more
negative; shifted to the left) from the value of Id at point 430.
However, by correcting for the shift of the boundary of the field
weakening region to curve 422 with increasing temperature, the same torque
may be obtained at point 434, which is closer to maximum efficiency
line 418. (Id.) This change involves increasing the value of I*ci, i.e., making
I*d less negative, i.e., shifting IA to the right. Luedtke seeks patent
protection for a vehicle embodying these principles and a method of
operating an electric machine applying these principles.
Claim 1 reads:
A vehicle comprising:
a bus;
an electric machine having a temperature;
an inverter configured to supply the electric machine
a winding current having a direct component (Id) and a
quadrature component (Iq); and
a controller configured to issue pulse width modulation
commands to the inverter to adjust the winding current
such that
for a given speed and torque of the electric machine
and voltage of the bus,
the direct component increases as the temperature
increases.
(Br., Claims App. 1; some indentation, paragraphing, and emphasis added.)
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Application 13/607,013
Remaining independent Claim 8 reads:
A method of operating an electric machine having a
temperature, the method comprising:
receiving a torque request;
[a] adjusting the torque request based on the temperature;
[b] calculating a direct component (Id) and a quadrature
component (Iq) of a target winding current based on the
adjusted torque request;
[c] adjusting the calculated direct component based on
the temperature; and
issuing commands to an inverter to supply a winding
current generally equal to the adjusted target winding
current.
(Br., Claims App. 2; some indentation, paragraphing, square bracketed
labels, and emphasis added.)
The Examiner maintains the following grounds of rejection6:
A. Claims 1 and 5 stand rejected under 35 U.S.C. § 102(e) in
view of Gallegos-Lopez.7
Al. Claims 3, 4, 6, and 7 stand rejected under 35 U.S.C. § 103(a)
in view of Gallegos-Lopez.
A2. Claim 2 stands rejected under 35 U.S.C. § 103(a) in view of
the combined teachings of Gallegos-Lopez and Shero.8
6 Examiner’s Answer mailed 17 December 2014 (“Ans.”).
7 Gabriel Gallegos-Lopez et al., Temperature compensation for improved
field weakening accuracy, U.S. Patent No. 8,519,648 B2 (2013), based on an
application filed 22 July 2011.
8 David J. Shero and Habib Dadpey, Induction motor control apparatus and
method, U.S. Patent No. 4,695,783 (1987).
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Application 13/607,013
B. Claim 8 stands rejected under 35 U.S.C. § 102(e) in view of
Tam.9
B1. Claims 9—11 stand rejected under 35 U.S.C. § 103(a) in view
of Tam.
B2. Claims 12 and 13 stand rejected under 35 U.S.C. § 103(a) in
view of the combined teachings of Lim and Lim ’459.10
B. Discussion
Findings of fact throughout this Opinion are supported by a
preponderance of the evidence of record.
Luedtke focuses arguments for patentability on the independent
claims only. (Br. 6, 7.) Accordingly, we focus our attention on these
arguments.
Claim 1; anticipation by Gallegos-Lopez
Luedtke urges that Gallegos-Lopez nowhere discloses that, for a given
speed and torque of the electric machine and voltage of the bus, the direct
component Id increases as the temperature increases, as required by claim 1.
(Br. 5.) In particular, Luedtke argues that the passage cited by the Examiner,
which describes Figure 3 (Gallegos-Lopez, col. 6,1. 6, to col. 7,1. 20), does
not indicate whether the direct component increases or decreases with
temperature. (Br. 5,11. 31—32.) Moreover, Luedtke urges, the curves shown
in Gallegos-Lopez Figure 6, also cited by the Examiner, “represent[] a
9 Seong Yeop Lim et al., Method for controlling motor torque in hybrid
electric vehicle, U.S. Patent No. 7,772,791 B2 (10 August 2010), based on
an application filed 29 May 2008.
10 Seong Yeop Lim and Young Jun Kim, System for controlling motor of
hybrid vehicle, U.S. Patent Application Publication 2012/0139459 Al (17
June 2012), based on an application filed 22 July 2011.
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Application 13/607,013
different phase flux linkage strength” (id. at 6,1. 3) and the “Examiner
makes no attempt to relate constant phase flux linkage strength to constant
torque, constant speed, and constant bus voltage” (id. at 11. 8—10). In
particular, because the Examiner compares two points at constant lq,
whereas the method described by Gallegos-Lopez corrects for temperature
changes by adjusting both Id and lq, Luedtke urges that “the points being
compared by the Examiner cannot represent results of the method of
Gallegos-Lopez for constant torque, constant speed, constant bus voltage,
and varying temperature.” (Id. at 11. 7—9.)
The Examiner responds that Gallegos-Lopez discloses “adding
correcting values to the predefined stator current based on temperature”
(Ans. 2,11. 19-20), and that “[t]he way Examiner interprets ‘adding’ is
equivalent of ‘increasing’” (id. at 11. 20-21, citing, inter alia,
Gallegos-Lopez, col. 7,11. 52—67). The Examiner also quotes
Gallegos-Lopez’s explanation that Figures 5 A and 5B “demonstrate that
larger values for the stationary currents Id and lq are required to obtain the
same flux linkage when the rotor magnet(s) are warmer.” (Id. at 3,11. 1—2,
and quoting Gallegos-Lopez, col. 9,11. 2-4.)
There are several difficulties with the Examiner’s position. First, the
Examiner does not direct our attention to any credible evidence that
Gallegos-Lopez uses the term “adding” as an equivalent to “increasing.”
Second, the passage describing Figure 4 in Gallegos-Lopez, cited by the
Examiner (Gallegos-Lopez, col. 7,11. 52—67) does describe the addition of
command current correction values Aid and Alq to pre-defmed current
commands I*d and I*q, respectively, but the Examiner does not show where
the Aid and Alq are necessarily positive. Moreover, as Luedtke argues, “[t]he
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Application 13/607,013
value added to the predefined stator current is the error correction term for
closed loop control, which is not based on temperature.” (Reply11 2,11. 1—2.)
Consideration of Figure 4 supports Luedtke’s arguments more than the
Examiner’s findings. Third, in Figure 5A, the curve labeled “90°C” is to the
left, at more negative values of Id, than the curve labeled “25°C.” In
contrast, as Luedtke argues, the ’013 Specification defines “increasing Id” as
making Id less negative, not increasing the absolute value of Id. (Reply 2,
11. 7-12.)
The Examiner makes no findings regarding the applied references that
cure these defects with respect to independent claim 1. The weight of the
evidence supports Luedtke. Accordingly, we reverse the rejections based on
Gallegos-Lopez.
Claim 8; anticipation by Lim
Luedtke urges that claim 8 requires three steps, in order, because
successive steps operate in turn on results of the earlier steps. (Br. 9,11. 2—
6.) Luedtke “concede[s] that Lim discloses in Figure 2 adjusting a torque
request based on temperature and calculating direct and quadrature currents
based on the adjusted torque request.” {Id. at 11. 8—10.) “However,” Luedtke
emphasizes, “at no point does Lim adjust the calculated direct component
based on temperature.” {Id. at 11. 10-11.) Thus, in Luedtke’s view, the
rejections in view of Lim should be reversed.
11 Reply Brief filed 27 January 2015 (“Reply”).
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Application 13/607,013
The Examiner responds that Lim describes “two instances where the
temperature affects the direct current.” (Ans. 4,11. 6—8, citing Lim, col. 2,
11. 24—36 and col. 3,11. 45-61.)
The Examiner, however, fails to explain how the “two instances” cited
comprise both [a] adjustments of a torque request based on the temperature,
and [c] a subsequent adjustment, based on the temperature, of the
calculated Id. Instead, Lim describes a method in which changes in torque
arising in response to changes in temperature are compensated, while the
time to produce a current control map and the complexity of the control
algorithm are reduced significantly. (Lim, col. 2,11. 52—57.) It has not
escaped our notice that Lim describes—in portions not cited by the
Examiner—a prior art process involving two separate adjustments
depending on temperature (Lim, figure 5 (not reproduced here), and col. 1,
1. 54, to col. 2,1. 6). However, the Examiner does not explain, nor is it clear,
how the determination of N control maps at N temperatures can be mapped
onto steps [a] and [c] of the claimed method.
The Examiner makes no findings regarding the additional applied
references that cure these defects with respect to independent claim 8. On
the present record, the weight of the evidence is that Luedtke has
demonstrated harmful error in the rejections of claim 8. Accordingly we
reverse the rejections based on Lim.
C. Order
It is ORDERED that the rejection of claims 1—13 is reversed.
REVERSED
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