EP0856937A2
Expired / Lapsed
EP
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Improved commutation position detection system and method
Assignee: Advanced Motion Controls Inc
•
Filing: 1997-08-11
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Granted: —
•
Expires: 2017-08-11
Abstract
Abstract An improved commutation position detection system for accurately determining commutation position within polyphase brushless motors without employing proximity sensors or transducers. The present invention determines commutation position by differentiating the current flowing within the stator coils and comparing the differentiated current waveforms to one another (absolute commutation position detection) or a predetermined threshold (incremental commutation position detection) to obtain a real-time assessment of commutation position. <IMAGE>
Inventors
- 👤 George Holling
- 👤 Michael Schmitt
- 👤 Mark Yeck
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-31 09:03
CPC Classifications
H; H02; H02P; H02P6/00; H02P6/14; H02P6/16; H02P6/20; H02P6/18; H02P6/185; H02P6/34
Claims Analysis
Total Claims: 30
Claim 1
Independent Claim
151 words
A method of starting a polyphase brushless
motor, said brushless motor having a plurality of field
coils disposed about a rotor, comprising the steps of: (a) simultaneously energizing each of said
plurality of field coils with a driving signal while said
rotor is maintained in a fixed position within said
motor; (b) continuously monitoring the current waveform
for each of said plurality of field coils during said
step of simultaneously energizing; (c) continuously differentiating said current
waveform for each of said plurality of field coils to
define a current rate of change waveform for each of said
plurality of field coils; (d) comparing said current rate of change waveform
for each of said plurality of field coils to a predetermined
voltage threshold to determine commutation
position; and (e) applying a driving signal to an active field
coil based on said commutation position to initiate said
rotor into motion within said motor.
Claim 2
Dependent Claim
49 words
The method as set forth in claim 1 and further
wherein said step (b) comprises the steps of: (i) providing current sensing means associated with
each of said plurality of field coils; and (ii) sensing the current waveform of each of said
plurality of field coils during step (a).
Claim 3
Dependent Claim
57 words
The method as set forth in claim 2 and further
wherein said step (c) comprises the steps of: (i) providing differentiation means associated with
said current sensing means; (ii) differentiating said current waveform of each
of said plurality of field coils to define a current rate
of change waveform for each of said plurality of field
coils.
Claim 4
Dependent Claim
90 words
The method as set forth in claim 3 and further,
wherein said step (d) comprises the steps of: (i) providing means for adjustably setting said
predetermined voltage threshold associated with said
differentiation means; (ii) setting said means for adjustably setting such
that said predetermined voltage threshold provides a
reference upon which to compare said current rate of
change waveform for each of said plurality of field
coils; and (iii) comparing said current rate of change waveform
for each of said plurality of field coils to determine
said active field coil.
Claim 5
Dependent Claim
48 words
The method as set forth in claim 3 and further,
wherein said step (e) comprises the further steps of: (i) providing commutation means for generating said
driving signal; and (ii) applying said driving signal to said active
field coil to initiate said rotor into motion within said
motor.
Claim 6
Dependent Claim
27 words
The method as set forth in claim 1 and further,
wherein step (b) includes the further step of continuously
normalizing the current waveform within said stator
coil.
Claim 7
Dependent Claim
52 words
The method as set forth in claim 6 and further,
comprising the further steps of: (i) providing normalization means associated
with said differentiation means; and (ii) employing said normalization means to
remove unwanted noise artifacts from one of said current
waveform and said current rate of change waveform of said
stator coil.
Claim 8
Dependent Claim
40 words
The method as set forth in claim 1 and further,
wherein step (e) includes the further step of providing
sample and hold means for selectively sampling and
holding the commutation position signal generated in step
(d) to eliminate switching transients.
Claim 9
Independent Claim
99 words
A method of starting a brushless polyphase
motor having a rotor and a plurality of field coils,
comprising the steps of: (a) applying a driving signal to each of said
plurality of field coils while said rotor is stationary; (b) continuously differentiating the current
waveform within each of said plurality of field coils
during step (a); (c) continuously comparing the differentiated
current waveforms from step (b) to a predetermined
voltage threshold; and (d) selectively energizing at least one of said
plurality of field coils based on the comparisons from
step (c) to force said rotor into proper rotational
motion.
Claim 10
Dependent Claim
62 words
The method set forth in claim 9 and further
wherein step (b) comprises the steps of: (i) providing current sensing means for sensing
the current waveform within each of said plurality of
field coils; (ii) providing differentiation means associated
with said current sensing means; and (iii) differentating said current waveform within
each of said plurality of field coils via said
differentiation means.
Claim 11
Dependent Claim
73 words
The method set forth in claim 10 and further,
wherein step (c) comprises the substeps of: (i) providing means for adjustably setting said
predetermined voltage threshold; (ii) providing comparing means for comparing each of
said differentiated current waveforms to said
predetermined voltage threshold; and (iii) comparing said differentiated current
waveforms from step (b) to said predetermined threshold
to determine the relative position of each of said
plurality of field coils to said rotor.
Claim 12
Dependent Claim
51 words
The method set forth in claim 11 and further
wherein step (d) comprises the steps of: (i) determining which of said plurality of field
coils is in the closest positional alignment with said
rotor to define an active field coil; and (ii) applying said driving signal to said active
field coil.
Claim 13
Independent Claim
128 words
A method for detecting the position of a rotor
with respect to a plurality of field coils in a polyphase
brushless motor, comprising the steps of: (a) continuously injecting at least a predetermined
nominal exciting current into each of said plurality of
field coils; (b) continuously monitoring the current waveform
for each of said plurality of field coils during said
step of continuously injecting; (c) continuously differentiating said current
waveform for each of said plurality of field coils to
define a current rate of change waveform for each of said
plurality of field coils; and (d) comparing the magnitude of at least two of said
current rate of change waveforms to one another to
produce an absolute reference indicative of the position
of said rotor within said motor.
Claim 14
Dependent Claim
49 words
The method as set forth in claim 13 and further
wherein said step (b) comprises the steps of: (i) providing current sensing means associated with
each of said plurality of field coils; and (ii) sensing said current waveform of each of said
plurality of field coils during step (a).
Claim 15
Dependent Claim
59 words
The method as set forth in claim 13 and further
wherein said step (c) comprises the steps of: (i) providing differentiation means associated with
each of said current sensing means; (ii) differentiating said current waveform of each
of said plurality of field coils to define a current rate
of change waveform for each of said plurality of field
coils.
Claim 16
Dependent Claim
59 words
The method as set forth in claim 13 and
further, wherein said step (d) comprises the further
steps of: (i) providing comparator means associated with at
least two of said plurality of differentiation means; (ii) comparing together the magnitude of said
current rate of change waveform of each of said at least
two of said plurality of differentiation means.
Claim 17
Dependent Claim
34 words
The method as set forth in claim 16 and
further, wherein said step (d)(i) comprises the step of
providing a plurality of comparators associated with at
least two of said plurality of differentiation means.
Claim 18
Dependent Claim
66 words
The method as set forth in claim 16 and
further, wherein said step (d)(i) comprises the steps of: (a) providing at least two multiplexers having
inputs coupled to each of said plurality of differentiation
means and an output coupled to a comparator; and (b) controlling said at least two multiplexers
to selectively submit two of said plurality of current
rate of rate waveforms to said comparator.
Claim 19
Independent Claim
105 words
A method for determining commutation position
within a brushless motor having a plurality of stator
coils disposed about a rotor, comprising the steps of: (a) applying at least a predetermined nominal
electric current to each of said plurality of stator
coils; (b) continuously differentiating the electric
current flowing within each of said plurality of stator
coils during step (a) to produce a current rate of change
waveform for each of said plurality of stator coils; and (c) continuously comparing together at least two of
said current rate of change waveforms to determine an
absolute reference indicative of the position of said
rotor within said motor.
Claim 20
Dependent Claim
62 words
The method set forth in claim 19 and further
wherein step (b) comprises the steps of: (i) providing current sensing means for sensing
said electric current within each of said plurality of
field coils; (ii) providing differentiation means associated
with said current sensing means; and (iii) differentating said electric current within
each of said plurality of field coils via said
differentiation means.
Claim 21
Dependent Claim
37 words
The method set forth in claim 19 and further,
wherein step (c) comprises the substeps of: (i) providing comparator means associated with said
differentiation means; (ii) comparing at least two of said current rate of
change waveforms.
Claim 22
Dependent Claim
28 words
The method as set forth in claim 21 and
further, wherein said step (c)(i) comprises the step of
providing a plurality of comparators associated with said
differentiation means.
Claim 23
Dependent Claim
95 words
The method as set forth in claim 21 and
further, wherein said step (c)(i) comprises the step of
providing a comparator, a first multiplexer for
selectively submitting at least one of said plurality of
current rate of change waveforms to said comparator, and
a second multiplexer for selectively submitting at least
one of said plurality of current rate of change waveforms
to said comparator, and step (c)(ii) comprises the step
of controlling said first and second multiplexers to
selectively submit at least two of said plurality of
current rate of change waveforms to said comparator.
Claim 24
Independent Claim
163 words
An apparatus for controlling the operation of a
polyphase brushless motor having rotor and a plurality of
stator coils, comprising: (a) commutation position detection means for determining
the position of said rotor relative to said
plurality of stator coils, said commutation position
detection means including: (i) current sensing means for sensing the amount of
electric current flowing within each of said
plurality of stator coils; (ii) differentiation means for differentiating said
amount of electric current flowing within each
of said plurality of stator coils; and (iii) comparator means for comparing together said
differentiated electric current of at least two
of said plurality of stator coils to determine
an absolute reference indicative of a position
of said rotor within said motor; and (b) commutation means for selectively applying at least
a predetermined nominal electric current to each of
said plurality of stator coils and selectively
applying a driving signal to one or more of said
plurality of stator coils depending upon said
absolute reference.
Claim 25
Dependent Claim
28 words
The apparatus as set forth in claim 24 and
further, wherein said comparator means comprises at least
two comparators coupled between said differentiation
means and said commutation means.
Claim 26
Dependent Claim
42 words
The apparatus as set forth in claim 24 and
further, said comparator means comprising multiplexing
means and a comparator, said multiplexing means for
selectively passing said differentiated electric current
for at least two of said plurality of stator coils to
said comparator.
Claim 27
Dependent Claim
60 words
The apparatus as set forth in claim 24 and
further, said commutation position detection means
including sample and hold means disposed between said
comparator means and said commutation means, said sample
and hold means for selectively sampling and holding the
commutation position signal generated by said comparator
so as deliberating block out the transient-laden portions
of said commutation position signal.
Claim 28
Independent Claim
94 words
An apparatus for determining commutation
position within a brushless motor having a rotor and
plurality of stator coils, comprising: (a) current sensing means for sensing the amount of
electric current flowing within each of said plurality of
stator coils; (b) differentiation means for differentiating said
amount of electric current flowing within each of said
plurality of stator coils; and (c) comparator means for comparing together said
differentiated electric current of at least two of said
plurality of stator coils to determine an absolute
reference indicative of a position of said rotor within
said motor.
Claim 29
Dependent Claim
28 words
The apparatus as set forth in claim 28 and
further, wherein said comparator means comprises at least
two comparators coupled between said differentiation
means and said commutation means.
Claim 30
Dependent Claim
42 words
The apparatus as set forth in claim 28 and
further, said comparator means comprising multiplexing
means and a comparator, said multiplexing means for
selectively passing said differentiated electric current
for at least two of said plurality of stator coils to
said comparator.
References Cited (Backward Citations)
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