Electricity: motive power systems – Plural – diverse or diversely controlled electric motors – Plural linear-movement motors
Reexamination Certificate
2001-03-23
2003-02-11
Ramirez, Nestor (Department: 2834)
Electricity: motive power systems
Plural, diverse or diversely controlled electric motors
Plural linear-movement motors
C318S135000, C318S700000, C318S687000, C318S715000
Reexamination Certificate
active
06518718
ABSTRACT:
BACKGROUND OF THE INVENTION
i) Field of the Invention
The present invention relates to a control system for a linear synchronous motor vehicle, and more particularly to a speed electromotive force phase control system adapted to low speed.
ii) Description of Related Art
A known example of conventional control systems for a linear synchronous motor (hereinafter referred to as “LSM”) vehicle comprises, as shown in
FIG. 7
, a propulsion coil
61
provided along a guideway on a ground; a field coil
62
a
provided on a vehicle
62
so as to face the propulsion coil
61
; a speed controller
63
for outputting a current command value I* computed by proportional-integral operation of the deviation between a speed command value v* and the actual speed v; a converter controller
64
for performing proportional-integral operation of the deviation between the current command value I* and a coil current I flowing through the propulsion coil
61
and outputting a voltage command value V* with a sine wave in synchronism with a position detecting phase &thgr;p as a phase reference to indicate the position of the vehicle; a power converter
65
for outputting a three-phase output voltage V in accordance with the voltage command value V* to the propulsion coil
61
through a feeder
66
; a current detector
67
for detecting the coil current I flowing through the propulsion coil
61
; a cross induction line
68
a
arranged along the track so as to obtain information about the vehicle position; a position detector
68
for detecting a relative position of the field coil
62
a
to the propulsion coil
61
based on a signal generated in the cross induction line
68
a
and outputting the position detecting phase &thgr;p; and a speed detector
69
for performing operation of an actual speed v necessary for speed control from the position-detecting phase &thgr;p and outputting the actual speed.
The propulsion coil
61
, particularly as shown in
FIG. 8A
, is composed of coil sections, such as
71
A
1
,
71
B
1
, and
71
C
1
having a prescribed length and a plurality of groups of coils for propulsion therein, which are arranged on both sides of the vehicle
62
such that respective coil sections on one side are shifted by half of their length relative to respective coil sections on the other side. As shown in
FIG. 8B
, each coil section comprises a plurality of groups of coils for propulsion of three phases, i.e. U-phase, V-phase, and W-phase, respectively, which groups are arranged along the forward direction of the vehicle. By supplying three-phase alternating current to these groups of coils, shifting magnetic field is generated. A phase reference is predetermined by using the length of a group of coils for propulsion of 2.7 m as one cycle (360°) of an electrical angle, and information about the vehicle position is obtained by detecting the phase reference with the position detector
68
.
The feeder
66
for supplying electricity, or outputting output voltage V, from the power converter
65
to each coil section consists of three feeder cables corresponding to three inverters
65
A,
65
B, and
65
C, respectively, contained in the power converter
65
. By controlling feeder section switches such as
72
A
1
,
72
B
1
72
C
1
. . . (omitted in
FIG. 7
) separately, electricity is supplied only to the three lines of coil sections in the vicinity of the running vehicle
62
.
For example, when the vehicle
62
runs in the right direction as shown in
FIG. 8A
, three feeder section switches
72
C
1
,
72
A
2
, and
72
B
2
are closed and electricity is supplied to the coil section
71
C
1
through a C-line inverter
65
C, to the coil section
71
A
2
through an A-line inverter
65
A, and to the coil section
71
B
2
through a B-line inverter
65
B, respectively. When the vehicle
62
reaches the position corresponding to the coil section
71
B
2
, a feeder section switch
72
C
2
is closed while the feeder section switch
72
C
1
is opened, with the result that power supply is stopped for the coil section
71
C
1
and started for the coil section
71
C
2
instead.
An LSM vehicle is driven by propulsion force generated by the interaction between a magnetic field generated by the field coil
62
a,
which is a superconductive coil, and a magnetic field generated in the propulsion coil
61
due to the three-phase output voltage V outputted from the power converter
65
. To control driving of the LSM vehicle, the position detecting phase &thgr;p is inputted into the converter controller
64
as a phase reference indicating the position of the vehicle
62
, and an actual speed v is computed by the speed detector
69
based on the position detecting phase &thgr;p. Therefore, accurate detection of the position detecting phase &thgr;p, i.e. the vehicle position, is required.
To fulfill this requirement, the cross induction line
68
a
is laid along the length of the track and a signal (an electric wave) is transmitted from the vehicle
62
to the cross induction line
68
a.
By processing a sine wave signal, which is generated in the cross induction line
68
a
due to the signal transmission from the vehicle
62
, with the position detector
68
, the position detecting phase &thgr;p is obtained. Thus, substantially accurate position detection is achieved.
However, the above-described method of detecting the position of the vehicle
62
requires accurate laying of the cross induction line
68
a
along the length of the track and maintenance thereof as well. It leads to a large amount of labor and high cost for construction and maintenance of the vehicle position detecting system.
To solve this problem, a method of detecting the vehicle position without providing a ground installation such as the cross induction line
68
a
has been thought out. In this method, electromotive force induced in the propulsion coil
61
due to the running of the vehicle
62
(hereinafter referred to as “speed electromotive force”) is estimated, and a phase indicating the vehicle position (hereinafter referred to as “speed electromotive force phase”) &thgr;e is obtained based on the estimated value. Specifically, as shown in
FIG. 9
, three-phase/&agr;&bgr; converters
81
a,
81
b
convert the output voltage V outputted from the power converter
65
and the coil current I flowing through the propulsion coil
61
to voltages V&agr;, V&bgr; and currents I&agr;, I&bgr;, respectively, in &agr;-&bgr; coordinate system. A speed electromotive force observer
82
estimates the speed electromotive force from the voltages V&agr;, V&bgr;, currents I&agr;, I&bgr;, and a vehicle angular speed &ohgr;, to obtain estimated speed electromotive force values Z &agr;, Z&bgr;. Resistance R and inductance L peculiar to the coil sections located in the neighborhood of the running vehicle
62
are further inputted as control constants to the speed electromotive force observer
82
, and then, speed electromotive force phase calculator
83
computes the speed electromotive force phase &thgr;e by an equation (i) below.
θ
e
=
tan
-
1
Z
β
Z
α
(
i
)
As described above, by computing the speed electromotive force phase &thgr;e and using the same as the phase reference instead of the position detecting phase &thgr;p, ground installations such as the cross induction line
68
a
and the position detector
68
become unnecessary. However, when the speed electromotive force phase &thgr;e, obtained by estimating the speed electromotive force as shown in
FIG. 9
, is used as the phase reference, there is a problem that the stable speed electromotive force phase &thgr;e cannot be obtained when the running speed of the vehicle is low (for example, the speed under 15 km/h).
Specifically, because the speed electromotive force phase &thgr;e is directly calculated by the above equation (i), it is likely to be affected by the control constants such as the resistance R and the inductance L of the coil sections. In short, this method has no robust stability against changes of the control constants, and wh
Kitano Junichi
Koga Syunsaku
Central Japan Railway Company
Davis & Bujold P.L.L.C.
Jones Judson H.
Ramirez Nestor
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