Ex Parte Luedtke

Patent Trial and Appeal Board

Jun 22, 2017

13607005 (P.T.A.B. Jun. 22, 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.
13/607,005 09/07/2012 Daniel Luedtke 83257451 9388
28395 7590 06/26/2017
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
06/26/2017 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 2016-004510
Application 13/607,0051
Technology Center 2800
Before GEORGE C. BEST, CHRISTOPHER L. OGDEN, and
CHRISTOPHER C. KENNEDY, Administrative Patent Judges.
OGDEN, Administrative Patent Judge.
DECISION ON APPEAL
Appellant appeals under 35 U.S.C. § 134(a) from the Examiner’s final
decision rejecting claims 1—7 and 10-14 in the above-identified application.2
We have jurisdiction pursuant to 35 U.S.C. § 6(b).
We AFFIRM-IN-PART.
1 According to Appellant, the real party in interest is Ford Global
Technologies, LLC. Appeal Br. 2 (Aug. 28, 2015).
2 Final Office Action (Apr. 23, 2015) [hereinafter Final Action]; Examiner’s
Answer (Feb. 4, 2016) [hereinafter Answer],
Appeal 2016-004510
Application 13/607,005
BACKGROUND
Appellant’s invention “relates to control of electric motors.” Spec.3
11. Independent claim 1 is representative:
1. A vehicle comprising:
an electric machine;
an inverter; and
a controller configured to
operate the electric machine in pulse width
modulation mode at a speed and torque of the machine and an
input voltage of the inverter, the speed and the voltage related
by a ratio, and
maintain operation in pulse width modulation
mode as speed and voltage increase proportionately according
to the ratio while maintaining the torque.
Appeal Br. App. 1 (key limitation emphasized). Independent claim 10
contains substantially the limitations emphasized above. See id. at 2—3.
The Examiner maintains the following grounds of rejection:
I. Claim 1 is rejected under 35 U.S.C. § 103(a) as being
unpatentable over Chen4 in view of Abolhassani.5 See Final Action 6—7.
II. Claims 2—6 are rejected under 35 U.S.C. § 103(a) as being
unpatentable over Chen in view of Abolhassani and further in view of
Cheng.6 See F inal Action 7—10.
III. Claim 7 is rejected under 35 U.S.C. § 103(a) as being
unpatentable over Chen in view of Abolhassani, and further in view of
Hashimoto.7 See Final Action 10—11.
3 Specification, Sept. 7, 2012 [hereinafter Spec.].
4 Chen et al., US 2004/0036434 A1 (published Feb. 26, 2004).
5 Abolhassani et al., US 2007/0267990 Al (published Nov. 22, 2007).
6 Cheng, US 2006/0138994 Al (published June 29, 2006).
7 Hashimoto et al., US 2011/0115318 Al (published May 19, 2011).
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Appeal 2016-004510
Application 13/607,005
IV. Claims 10-14 are rejected under 35 U.S.C. § 103(a) as being
unpatentable over Chen in view of Cheng. See Final Action 11—16.
DISCUSSION
Claims 1 and 7
Chen is directed to a “closed-loop permanent magnet motor control
method,” which includes determining “[a] maximum limit for allowable
torque current and a minimum threshold for the maximum torque current,”
and the comparison of these values affects the method of operating the
motor. See Chen Abstract; see also id. 11 8-9. Chen provides a formula for
the maximum limit for allowable torque current ax as Equation 14, which
is reproduced below:
Chen 178. This equation relates the maximum value of torque current i^ax
in an electric motor to the flux current command i*d and other variables
including the direct current bus voltage VDC and the synchronous speed cnr.
See id. 27, 46, 52, 78. Lq and Ld are motor inductances in the q (torque)
and d (flux) axes, respectively, and XPM is the permanent magnet rotor flux.
See id. H 34, 39, 49.
Equation 14 relates to Chen’s Figure 4, reproduced below:
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Application 13/607,005
Id (Amps)
Fig. 4
Figure 4 is a graph of iq (torque current) vs. id (flux current), depicting a
“voltage limit ellipse” 10 corresponding to the value of ax in Equation 14
plotted against the flux current command i*d in the x-axis for a given speed
(or and bus voltage VDC. See id. ]Hf 15, 29-30, 73—78. The figure also shows
two constant torque lines 12 and 14. Phase current trajectory 16 represents a
line reflecting peak torque per ampere (PTPA) for a given torque command
7*. See id. 15, 75.
Citing Equation 14, the Examiner finds that Chen teaches a vehicle
that maintains speed and voltage in a proportionally increasing relation
while the vehicle maintains constant torque. Final Action 6—7. According to
the Examiner, “[Ejquation 14 clearly indicates that in order to maintain the
torque current (i^ax), the ratio of (VDC/o)r) must be constant for a given
value of flux current (id).'n Final Action 7 (formatting added); accord id. at
12 (regarding independent claim 10).
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Application 13/607,005
Appellant argues that i^ax is only a maximum value of the torque
current, and is not the torque current command iq that is responsible for
producing torque in the electric machine. See Appeal Br. 4. Appellant also
argues that the maximum torque value i^ax only remains constant for
constant VDC/(jor if id is also constant; however, id “is not constant, but
rather ‘is increased to move the operating point to the left along the ellipse
boundary 10.’” in Chen’s Figure 4. See id. at 4—5. According to Appellant,
Chen teaches that “[w]hile operating at any given torque, as the motor speed
increases ... the DC bus voltage is reduced.” Id. at 5 (quoting Chen 179.).
We find Appellant’s arguments regarding Chen persuasive. The
Examiner has not shown that the torque current command iq is at the
maximum i^ax while flux current command id is held constant. Thus, the
Examiner has not shown that Chen teaches an operating mode in which
Equation 14 requires the speed a)r and voltage VDC to increase
proportionally.
However, the Examiner also finds that “Abolhassani teaches operating
the electric machine . . . while maintaining torque with a constant slope of
speed and voltage.” Final Action 7 (citing Abolhassani 139). In the
Answer, the Examiner clarified this by reference to Abolhassani’s Figure 6,
reproduced below:
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Application 13/607,005
PHM Duly Cycle Field Weakening
Figure 6 “shows a curve 120 representing the power output and phase
voltage of the motor ... at various motor speeds, as well as an exemplary
torque/flux curve 121 representing different torque and flux generated by the
motor at different motor speeds.” Abolhassani 139. It also shows two
operating ranges, one labeled “PWM Duty Control Range,” in which the
motor is controlled by pulse width modulation. See id. The Examiner finds
that the slope of curve 120 “is a ratio of voltage (U) over speed which is
increasing proportionally.” Answer 4 (citing Abolhassani 139).
In response, Appellant argues that “the curve the Examiner points to
in Figure 6 shows that the ratio [between voltage and speed] increases
steadily as speed increases.” Reply Br. 2. We do not find this argument
persuasive because it reflects a misinterpretation of the Examiner’s finding.
The Examiner identifies the variable U as the voltage, not as the ratio of
voltage to speed. Thus, Figure 6 shows that in the PWM duty control range,
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Application 13/607,005
voltage U increases proportionally with speed over a range in which torque
T is held constant.
Thus, while we agree that the Examiner erroneously relies on Chen
for teaching a controller configured to “maintain operation ... as speed and
voltage increase proportionately according to the ration while maintaining
the torque,” this error is harmless in view of the Examiner’s persuasive
showing that Abolhassani teaches this limitation.
The Examiner also determines that Abolhassani teaches that pulse
width modulation is maintained during the range in which torque and the
ratio of speed to voltage are held constant (corresponding to the “PWM Duty
Control Range” of Figure 6). See Final Action 7; Answer 5. Appellant does
not dispute the Examiner’s finding that pulse width modulation is
maintained in this range. See Appeal Br. 5—6; Reply Br. 2.
For the above reasons, the preponderance of the evidence on this
record supports the Examiner’s rejection of claim 1. Claim 7 depends
directly from claim 1, and Appellants do not present specific arguments that
the Examiner erred in rejecting claim 7. See Appeal Br. 4—6. Therefore, we
affirm the Examiner’s rejection of claims 1 and 7.
Claims 2—6 and 10—14
Claim 2 depends from claim 1 and requires that “the controller is
further configured to transition from pulse width modulation mode to six-
step mode in response to any decrease in voltage while maintaining the
speed and torque.” Appeal Br. App. 1. Independent claim 10 recites
substantially the same limitation. See id. at 3.
The Examiner finds that Cheng teaches a controller that transitions
between pulse width modulation mode and six-step mode, and that “[t]he
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Application 13/607,005
motor can rotate much more smoothly at low speed using [the] PWM
technique whereas Six-step mode at high speed reduces switching loss hence
provides good cooling.” Final Action 8—9. Thus, the Examiner concludes
that “[i]t would have been obvious to one of ordinary skill in the art at the
time of the invention to use six-step mode in high speed operation as taught
by Cheng in Chen’s/Abolhassani’s teachings in order to reduce switching
loss.” Id. at 8, 13.
As to the requirement that this switch be made “while maintaining the
voltage and torque,” the Examiner notes that Chen teaches it is easy to
manipulate variables such as voltage and torque. See id. at 8, 13—14. Thus,
the Examiner determines that “the system could be easily operated at any
given torque value while manipulating speed, voltage and flux current values
and one ordinary skilled in the art could easily relate when to switch from
PWM to six-step and vice versa using Cheng reference.” Id. at 8, 14;
Answer 6.
Appellants argue that Cheng’s general disclosure does not provide a
skilled artisan with a specific reason to switch from pulse width modulation
to six-step mode while maintaining voltage and torque, and that Chen also
provides no such specific teaching. We find this argument persuasive. It is
not enough that a person of ordinary skill in the art could modify the prior
art to arrive at the claimed invention, the Examiner must show that a skilled
artisan would have had reason to do so. Belden Inc. v. Berk-TekLLC, 805
F.3d 1064, 1073 (Fed. Cir. 2015). The Examiner has not shown, by use of
Equation 14 or otherwise, that Chen teaches a skilled artisan to maintain
voltage and torque during a transition from pulse width modulation mode to
six-step mode as required by claims 2 and 10.
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Application 13/607,005
For the above reasons, the Examiner has failed to establish a prima
facie case of obviousness with respect to claims 2 and 10. The Examiner’s
rejections of dependent claims 3—6 (which depend directly or indirectly from
claim 2) and 11—14 (which depend directly or indirectly from claim 10) do
not cure this error. Therefore, we reverse the Examiner’s rejections of
claims 2—6, and 10—14 under 35 U.S.C. § 103(a).
DECISION
The Examiner’s rejection of claims 1 and 7 is affirmed.
The Examiner’s rejection of claims 2—6, and 10—14 is reversed.
No time period for taking any subsequent action in connection with
this appeal maybe extended. See 37 C.F.R. § 1.136(a)(l)(iv) (2016).
AFFIRMED-IN-PART
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