FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
CONTROL DEVICE, ELECTRICAL RAILWAY VEHICLE, AND CONTROL
METHOD;
MITSUBISHI ELECTRIC CORPORATION, A CORPORATION
ORGANISED AND EXISTING UNDER THE LAWS OF JAPAN, WHOSE
ADDRESS IS 7-3, MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 1008310,
JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED
2
DESCRIPTION
Technical Field
[0001] The present disclosure relates to a control device, an electric railway vehicle,
and a control method.
5 Background Art
[0002] Electric railway vehicles (hereinafter referred to as “electric vehicles”)
include motors and control devices for feeding electric power to the motors. Some of
the control devices include inverter units for converting DC current fed from the outside
into three-phase AC power and feeding the three-phase AC power to the motors.
10 [0003] The control of the motors executed by the control devices may be subject to
various abnormalities. For the purpose of detection of such abnormalities, for example,
a control device disclosed in Patent Literature 1 determines that an abnormality occurs
when a pulse width modulation (PWM) factor of an inverter unit is higher than a
reference value in a vehicle running at a low velocity.
15 Citation List
Patent Literature
[0004] Patent Literature 1: Unexamined Japanese Patent Application Publication
No. 2018-93724
Summary of Invention
20 Technical Problem
[0005] The control device controls the operations of motors on the basis of
feedback of rotational speeds of the motors. The motors are thus typically provided
with rotational speed sensors for measuring the rotational speeds of the motors. The
rotational speed sensors having any abnormality prevent the control device from properly
25 controlling the operations of the motors. The control device is required to detect such an
abnormality in the rotational speed sensors. The control device disclosed in Patent
3
Literature 1, however, is not able to determine the occurrence of an abnormality in the
rotational speed sensors.
[0006] An objective of the present disclosure, which has been accomplished in
view of the above problems, is to determine the occurrence of an abnormality in the
5 rotational speed sensors for measuring rotational speeds of motors.
Solution to Problem
[0007] In order to achieve the above objective, a control device according to the
present disclosure controls operations of a plurality of motors of an electric railway
vehicle running in accordance with an operation command signal. The control device
10 includes a power converter, a suspected abnormal sensor determiner, a reference
rotational speed obtainer, a command value determiner, a modulation factor obtainer, and
an abnormality determiner. The power converter feeds electric power to each of the
plurality of motors. The suspected abnormal sensor determiner determines, based on
signals that are output from a plurality of rotational speed sensors provided for the
15 plurality of motorsin one-to-one correspondence and that indicate rotational speeds of the
plurality of motors, whether the plurality of rotational speed sensors include a suspected
abnormal sensor suspected of having an abnormality. Each of the signals is output from
a corresponding rotational speed sensor of the plurality of rotational speed sensors and
indicates a rotational speed of a corresponding motor of the plurality of motors. The
20 reference rotational speed obtainer obtains a reference rotational speed, based on one or
more signals that are output from the plurality of rotational speed sensors other than the
suspected abnormal sensor and that each indicate the rotational speed, when the suspected
abnormal sensor determiner determines that the plurality of rotational speed sensors
include the suspected abnormal sensor. Each of the one or more signals is output from a
25 corresponding rotational speed sensor of the plurality of rotational speed sensors other
than the suspected abnormal sensor. The command value determiner determines a
command value of voltage to be output from the power converter, based on the operation
4
command signal, the reference rotational speed, and values of current fed from the power
converter to the motors. The modulation factor obtainer obtains a modulation factor
based on the command value of voltage. The abnormality determiner determines that a
motor of the plurality of motors that corresponds to the suspected abnormal sensor has an
5 abnormality, when the difference between the modulation factor and a comparative
modulation factor that is set in advance is larger than or equal to a modulation-factor
threshold. The abnormality determiner determines that the suspected abnormal sensor
has an abnormality, when the difference between the modulation factor and the
comparative modulation factor is smaller than the modulation-factor threshold.
10 Advantageous Effects of Invention
[0008] According to the present disclosure, the suspected abnormal sensor
determiner determines whether the plurality of rotational speed sensors include a
suspected abnormal sensor suspected of having an abnormality. The abnormality
determiner determines whether the difference between the modulation factor obtained
15 based on the command value and the comparative modulation factor that is set in advance
is larger than or equal to the modulation-factor threshold, and can thus determine the
occurrence of an abnormality in the plurality of rotational speed sensors.
Brief Description of Drawings
[0009] FIG. 1 is a schematic diagram illustrating a configuration of an electric
20 railway vehicle according to Embodiment 1;
FIG. 2 is a block diagram illustrating configurations of a control device, motors,
and rotational speed sensors according to Embodiment 1;
FIG. 3 is a block diagram illustrating a configuration of a controller according to
Embodiment 1;
25 FIG. 4 is a flowchart illustrating the first half of a control process according to
Embodiment 1;
FIG. 5 is a flowchart illustrating the second half of the control process according to
5
Embodiment 1;
FIG. 6 is a graph illustrating a variation in an output current with and without
current feedback according to Embodiment 1;
FIG. 7 is a graph illustrating a variation in a modulation factor with and without
5 current feedback according to Embodiment 1;
FIG. 8 is a schematic diagram illustrating a configuration of an electric railway
vehicle according to Embodiment 2; and
FIG. 9 is a block diagram illustrating a configuration of a controller according to
Embodiment 3.
10 Description of Embodiments
[0010] The following describes a control device, an electric railway vehicle, and a
control method according to embodiments of the present disclosure, with reference to the
accompanying drawings. The electric railway vehicle is hereinafter referred to as
“electric vehicle”.
15 [0011] Embodiment 1
As illustrated in FIG. 1, an electric vehicle 100 according to Embodiment 1
includes a vehicle body 1, wheels 2 provided to the vehicle body 1, motors 3 to rotate the
wheels 2, rotational speed sensors 4 to measure rotational speeds of the motors 3, a
control device 5 to control the rotation of the motors 3, and a driver cab 6 to output an
20 operation command signal. The cab 6 is manipulated by a train operator, and includes a
master controller 61 to output an operation command signal. The electric vehicle 100
runs in accordance with an operation command signal. The operation command signal
contains a power running command, a braking command, or another command, to
indicate a direct or indirect instruction for a velocity of the electric vehicle 100 and
25 rotational speeds of the motors 3.
[0012] The wheels 2 support the vehicle body 1 and rotate in accordance with
driving forces of the motors 3. The rotating wheels 2 cause the vehicle body 1 to run.
6
This embodiment assumes that each car of the electric vehicle has four pairs of wheels 2.
Each pair of wheels is fixed at both ends of an axle.
[0013] The motors 3 rotate in response to application of three-phase AC voltage,
and rotate the wheels 2 via the corresponding axles. Examples of the motors 3 include a
5 three-phase induction motor.
[0014] The electric vehicle 100 is made of motor cars each having the motors 3 and
trailers having no motors 3. The motors 3 are provided for the respective axles of the
motor car. Each motor car has four motors 3 in this embodiment.
[0015] The rotational speed sensors 4 are provided for the motors 3 in one-to-one
10 correspondence. Each of the rotational speed sensors 4 outputs, to the control device 5,
a signal indicating a rotational speed of the corresponding motor 3. The signals
indicating rotational speeds of the motors 3 are hereinafter referred to as “rotational speed
signals”. The rotational speed sensors 4 include rotary encoders, tachogenerators, pulse
generators, or the like. The rotational speed sensors 4 in this embodiment are each a
15 pulse generator to output a pulse signal having a pulsed waveform in response to every
rotation of the rotational axis of the corresponding motor 3 by a predetermined angle.
The rotational speed signals, that is, pulse signals output from the rotational speed sensors
4 are fed to the control device 5.
[0016] The control device 5 controls operations of the motors 3 on the basis of the
20 operation command signal and the rotational speed signals. The control device 5 drives
the motors 3, and determines the occurrence of an abnormality in the motors 3 or the
rotational speed sensors 4.
[0017] The control device 5 has a configuration, which is described in detail below
with reference to FIG. 2. The control device 5 is installed in the vehicle body 1 of each
25 motor car having the motors 3. That is, the vehicle body 1 of each motor car has a
single control device 5, four motors 3, and four rotational speed sensors 4 in this
embodiment.
7
[0018] The control device 5 includes a power converter 51 to convert electric power
into another electric power and feed the converted electric power to each of the four
motors 3, a controller 52 to control the operation of the power converter 51, and current
measurers 53 to measure values of current flowing between the power converter 51 and
5 the motors 3, that is, values of current fed from the power converter 51 to the motors 3.
[0019] The power converter 51 includes an inverter unit to convert DC power, fed
from a DC overhead wire via a current collector, into three-phase AC power and to feed
the three-phase AC power to the motors 3. The power converter 51 controls the
operation of the inverter unit and can thus perform control of the electric power to be fed
10 to the motors 3 with respect to effective voltage, effective current, frequency, phase, and
the like.
[0020] The current measurers 53 measure values of current flowing through the
respective phases between the power converter 51 and the motors 3, and output current
value signals indicating the current values to the controller 52. The current measurers
15 53 are not necessarily provided for all the three phases like those illustrated in FIG. 2, and
may be provided for only two of the three phases.
[0021] The controller 52 receives the operation command signal output from the
master controller 61, which is described above with reference to FIG. 1, the current value
signals output from the current measurers 53, and the rotational speed signals output from
20 the rotational speed sensors 4. The controller 52 executes vector control of the motors 3
on the basis of the current value signals and the rotational speed signals. The controller
52 determines rotational speeds and rotational torques of the motors 3, and determines
parameters, such as voltage value, current value, and frequency, of electric power to be
output from the power converter 51. This command value of voltage to be output from
25 the power converter 51 is hereinafter referred to as “voltage command value”. The
controller 52 performs control for applying a voltage indicated by the determined voltage
command value to the motors 3 and thus drives the motors 3.
8
[0022] The following describes a configuration of the controller 52 in detail with
reference to FIGS. 2 and 3.
[0023] The controller 52 includes a suspected abnormal sensor determiner 521 to
determine whether any of the rotational speed sensors 4 is suspected of having an
5 abnormality, a selector 522 to select rotational speed signals to be transferred to the
reference rotational speed obtainer 523 among the rotational speed signals output from
the four rotational speed sensors 4, a reference rotational speed obtainer 523 to obtain a
reference rotational speed on the basis of the rotational speed signals selected by the
selector 522, a command value determiner 524 to determine a command value of electric
10 power to be output from the power converter 51, a power controller 525 to control the
operation of the power converter 51, a modulation factor obtainer 526 to obtain a
modulation factor on the basis of the command value of electric power, and an
abnormality determiner 527 to determine whether the four motors 3 or the four rotational
speed sensors 4 have any abnormality on the basis of the modulation factor.
15 [0024] The suspected abnormal sensor determiner 521 receives pulse signals from
the four rotational speed sensors 4. On the basis of the received pulse signals, the
suspected abnormal sensor determiner 521 determines whether any of the four rotational
speed sensors 4 is suspected of having an abnormality. Being suspected of having an
abnormality is hereinafter referred to as “suspected abnormal”, and a rotational speed
20 sensor 4 suspected of having an abnormality is referred to as “suspected abnormal
sensor”. The definition of abnormalities encompasses failures and means a state of
being unable to perform an expected function or performance.
[0025] The suspected abnormal sensor determiner 521 determines whether the
frequency of a pulse signal output from each of the four rotational speed sensors 4 is
25 larger than or equal to a reference frequency during a measurement period that is set in
advance, and thus determines whether the four rotational speed sensors 4 include a
suspected abnormal sensor. The measurement period is one minute, for example. The
9
reference frequency is set, in advance, to a value equal to or lower than the frequencies of
pulse signals that are to be output from the rotational speed sensors 4 in normal states
while the motors 3 are rotating properly. The suspected abnormal sensor determiner
521 determines a rotational speed sensor 4 that outputs a pulse signal having a frequency
5 equal to or higher than the reference frequency to be normal. When determining all the
rotational speed sensors 4 to be normal, the suspected abnormal sensor determiner 521
determines that no rotational speed sensor 4 is suspected of having an abnormality. In
contrast, when determining that any of the rotational speed sensors 4 outputs a pulse
signal having a frequency lower than the reference frequency, the suspected abnormal
10 sensor determiner 521 determines this rotational speed sensor 4 as suspected abnormal,
and determines that the four rotational speed sensors 4 include a suspected abnormal
sensor.
[0026] The suspected abnormal sensor determiner 521 regards a rotational speed
sensor 4 as a suspected abnormal sensor, (i) in the case where the rotational speed sensor
15 4 actually has an abnormality or failure, or (ii) in the case where the motor 3
corresponding to the rotational speed sensor 4 fails to properly rotate due to jamming in
the motor 3 regardless of the normal state of the rotational speed sensor 4. The state in
which "jamming occurs" is a state in which the motor 3 is inhibited from achieving
smooth rotation, for example, because of anchoring of the output shaft of the motor 3.
20 The state in which "jamming occurs" is a state in which the motor 3 is implied by, for
example, a rotational speed of the motor 3 lower than a threshold speed defined by a
designer or an engineer.
[0027] The suspected abnormal sensor determiner 521, when determining that the
rotational speed sensors include a suspected abnormal sensor, outputs a determination
25 signal, containing information indicating the existence of a suspected abnormal sensor
and information for identifying the suspected abnormal sensor, to the selector 522, the
power controller 525, and the abnormality determiner 527. The suspected abnormal
10
sensor determiner 521 also determines whether the pulse signals include a pulse signal
corresponding to the suspected abnormal sensor. When determining that the pulse
signals include a pulse signal corresponding to the suspected abnormal sensor, the
suspected abnormal sensor determiner 521 outputs a determination signal further
5 containing information indicating that this pulse signal corresponds to the suspected
abnormal sensor as well as the above-mentioned information.
[0028] The selector 522 receives the pulse signals output from the respective
rotational speed sensors 4, and the determination signal output from the suspected
abnormal sensor determiner 521. When receiving a determination signal indicating the
10 existence of a suspected abnormal sensor, the selector 522 provides the reference
rotational speed obtainer 523 with the pulse signals received from the rotational speed
sensors 4 other than the suspected abnormal sensor indicated by the determination signal.
When receiving a determination signal indicating that the pulse signals contain a pulse
signal corresponding to the suspected abnormal sensor, the selector 522 does not provide
15 the reference rotational speed obtainer 523 with the pulse signal corresponding to the
suspected abnormal sensor indicated by the determination signal.
[0029] The selector 522 completes the selection of pulse signals to be provided to
the reference rotational speed obtainer 523, and then outputs a selection completion
signal indicating completion of selection of pulse signals. The selection completion
20 signal is fed to the power controller 525.
[0030] The reference rotational speed obtainer 523 receives the pulse signals
selected by the selector 522. On the basis of the received pulse signals, the reference
rotational speed obtainer 523 obtains a reference rotational speed for determining a
voltage to be output from the power converter 51. In detail, the reference rotational
25 speed obtainer 523 obtains, on the basis of the received pulse signals, the rotational
speeds of the motors 3 indicated by the respective values of the received pulse signals.
The reference rotational speed obtainer 523, upon obtaining the rotational speeds of the
11
motors 3, calculates an average of the obtained rotational speeds. This average
rotational speed is hereinafter referred to as “reference rotational speed”. The reference
rotational speed may be, instead of the average of the rotational speeds of the motors 3
calculated from the pulse signals output from the rotational speed sensors 4 determined to
5 be normal, the median or a representative value of the rotational speeds of the motors 3,
for example.
[0031] In response to the determination that the four rotational speed sensors 4
include a suspected abnormal sensor, the reference rotational speed obtainer 523 obtains a
reference rotational speed on the basis of the pulse signals output from the respective
10 rotational speed sensors 4 other than the suspected abnormal sensor. In specific, in the
case where the rotational speed sensors 4 are determined to include a single suspected
abnormal sensor and three normal sensors, the reference rotational speed obtainer 523
obtains a reference rotational speed from the pulse signals output from the three rotational
speed sensors 4 determined to be normal. In contrast, in response to the determination
15 that the four rotational speed sensors 4 include no suspected abnormal sensor, the
reference rotational speed obtainer 523 obtains a reference rotational speed on the basis of
the pulse signals output from the four rotational speed sensors 4. The reference
rotational speed obtained on the basis of the pulse signals output from the respective
rotational speed sensors 4 other than the suspected abnormal sensor is hereinafter referred
20 to as “first reference rotational speed”. The reference rotational speed obtained on the
basis of the pulse signals output from all the rotational speed sensors 4 is referred to as
“second reference rotational speed”. The first reference rotational speed corresponds to
the “reference rotational speed”. The reference rotational speed obtainer 523 outputs
reference rotational speed information indicating the first reference rotational speed or the
25 second reference rotational speed.
[0032] The command value determiner 524 receives the operation command signal
output from the master controller 61 illustrated in FIG. 1, the reference rotational speed
12
information output from the reference rotational speed obtainer 523, and the current value
signals output from the current measurers 53. On the basis of the operation command
signal, the reference rotational speed information, and the current value signals, the
command value determiner 524 determines a command value of voltage to be output
5 from the power converter 51. The command value of voltage is hereinafter referred to
as “voltage command value”.
[0033] The command value determiner 524 refers to different pieces of information
to determine a voltage command value, depending on a velocity of the vehicle body 1.
In an exemplary case where the vehicle velocity or the velocity of the vehicle body 1 is
10 lower than a vehicle velocity threshold that is set in advance, that is, the rotational speeds
of the motors 3 are lower than a threshold, the command value determiner 524
determines a voltage command value within such a range that the fed-back current values
are at most a “overcurrent set value” that is set in advance. The voltage command value
is determined to minimize the deviation between the present vehicle velocity and the
15 vehicle velocity instructed by an operation command indicated by the operation
command signal. The vehicle velocity is obtained on the basis of the reference
rotational speed information, for example. The vehicle velocity threshold and the
overcurrent set value are stored in a storage area of the controller 52, for example. The
threshold velocity is 30 km/h, for example.
20 [0034] In another exemplary case where the vehicle velocity is equal to or higher
than the threshold velocity, the command value determiner 524 determines a voltage
command value that minimizes the deviation between the present vehicle velocity and the
vehicle velocity instructed by the operation command, without using the values of current
measured by the current measurers 53, which are smaller than the back electromotive
25 forces generated by rotation of the motors 3.
[0035] The command value determiner 524 provides the power controller 525 and
the modulation factor obtainer 526 with command value information indicating the
13
determined voltage command value.
[0036] The power controller 525 controls the operation of the inverter unit of the
power converter 51 on the basis of the voltage command value, and performs pulse width
modulation (PWM) of a DC voltage. The power controller 525 thus causes the power
5 converter 51 to output the effective voltage indicated by the voltage command value.
[0037] The power controller 525 halts the operation of the power converter 51
when the determination signal fed from the suspected abnormal sensor determiner 521
indicates the existence of a suspected abnormal sensor.
[0038] The modulation factor obtainer 526 receives the command value
10 information output from the command value determiner 524, and obtains a modulation
factor on the basis of the voltage command value indicated by the command value
information. In detail, the modulation factor obtainer 526 obtains a modulation factor
by dividing the voltage command value indicated by the command value information by
the maximum output voltage of the control device 5. A large modulation factor implies
15 a higher voltage required for actual rotation of the motors 3 relative to the maximum
output voltage. A small modulation factor implies a lower voltage required for actual
rotation of the motors 3 relative to the maximum output voltage. The modulation factor
obtainer 526 outputs modulation factor information indicating the obtained modulation
factor.
20 [0039] The abnormality determiner 527 receives the modulation factor information
obtained by the modulation factor obtainer 526. The abnormality determiner 527 also
receives the determination signal from the suspected abnormal sensor determiner 521.
When the determination signal from the suspected abnormal sensor determiner 521
indicates the existence of a suspected abnormal sensor, the abnormality determiner 527
25 determines whether the difference between the modulation factor and a comparative
modulation factor, which is a modulation factor in the case of no jamming in the motors 3,
is larger than or equal to a first modulation-factor threshold that is set in advance. The
14
first modulation-factor threshold is a threshold for determination of whether jamming
occurs in the motors 3 and is an example of “jamming-modulation-factor threshold”.
The first modulation-factor threshold is set to a value contributing to determination of the
occurrence of jamming in the motors 3. The first modulation-factor threshold is stored
5 in the storage area of the controller 52, for example.
[0040] The abnormality determiner 527 locates the abnormality on the basis of a
result of determination. In detail, the abnormality determiner 527 determines whether
the difference between the modulation factor obtained on the basis of the first reference
rotational speed and the comparative modulation factor is larger than or equal to the first
10 modulation-factor threshold.
[0041] When determining that the difference between the modulation factor and the
comparative modulation factor is larger than or equal to the first modulation-factor
threshold, the abnormality determiner 527 determines that jamming as an abnormality
occurs in the motor 3 corresponding to the suspected abnormal sensor.
15 [0042] When determining that jamming occurs in the motor 3, the abnormality
determiner 527 outputs first abnormality occurrence information S1 indicating that
jamming occurs in the motor 3. The first abnormality occurrence information S1 is fed
to the power controller 525. The power controller 525, when receiving the first
abnormality occurrence information S1, halts the operation of the power converter 51.
20 [0043] In contrast, when determining that the difference between the modulation
factor and the comparative modulation factor is smaller than the first modulation-factor
threshold, the abnormality determiner 527 determines that the rotational speed sensor 4
corresponding to the suspected abnormal sensor has an abnormality. In this case, the
abnormality determiner 527 outputs second abnormality occurrence information S2
25 indicating that the rotational speed sensors 4 have an abnormality. The second
abnormality occurrence information S2 is fed to the driver cab 6, which is described
above with reference to FIG. 1. The driver cab 6, upon receiving the second
15
abnormality occurrence information S2, causes a monitor in the driver cab 6 to display
information indicating an abnormality in the rotational speed sensors 4, for example.
[0044] The following describes a process of controlling the operations of the
motors 3 executed by the control device 5 having the above-described configuration, with
5 reference to FIGS. 1 to 5.
[0045] The control device 5 initiates the control process illustrated in FIGS. 4 and 5,
for example, when the master controller 61 outputs an operation command signal
indicating a power running command in response to manipulation of a train operator on
the master controller 61 in the electric vehicle 100 standing still. The following assumes
10 that the operation command signal indicating a power running command is being
continuously fed to the controller 52 during the control process.
[0046] In response to feeding of the operation command signal to the command
value determiner 524 and determination of the voltage command value at the command
value determiner 524, the power controller 525 controls the operation of the power
15 converter 51. In detail, the reference rotational speed obtainer 523 obtains the second
reference rotational speed, which is a reference rotational speed based on the pulse
signals from all the rotational speed sensors 4, and the command value determiner 524
determines a voltage command value, on the basis of the operation command signal
indicating a power running command, the reference rotational speed information
20 indicating the second reference rotational speed, and current value signals. The power
controller 525 causes the power converter 51 to apply a voltage having a value equal to
the voltage command value to the motors 3 and thus feed electric power to the motors 3
in a power feeding step (Step S101). The fed power rotates the motors 3 and provide
driving forces to the corresponding wheels 2, thus causing the vehicle body 1 to start
25 running in a running step (Step S102).
[0047] The suspected abnormal sensor determiner 521 determines the existence of a
suspected abnormal sensor, on the basis of the pulse signals output from the respective
16
rotational speed sensors 4, in a suspected-abnormal-sensor determining step (Step S103).
[0048] In the suspected-abnormal-sensor determining step, the suspected abnormal
sensor determiner 521 waits until the four rotational speed sensors 4 are determined to
include a suspected abnormal sensor (Step S103; No). When determining that the four
5 rotational speed sensors 4 include a suspected abnormal sensor, the suspected abnormal
sensor determiner 521 outputs a determination signal containing information indicating
the existence of a suspected abnormal sensor and information for identifying the
suspected abnormal sensor (Step S103; Yes). The determination signal is fed to the
selector 522, the power controller 525, and the abnormality determiner 527.
10 [0049] In response to the determination that the rotational speed sensors include a
suspected abnormal sensor, the power controller 525 halts the operation of the power
converter 51 in a halting step (Step S104).
[0050] In parallel to Step S104, the selector 522 selects pulse signals output from
the rotational speed sensors 4 other than the suspected abnormal sensor, in a selecting
15 step (Step S105). In detail, the selector 522 stops providing the reference rotational
speed obtainer 523 with the pulse signals output from all the rotational speed sensors 4,
and starts providing the reference rotational speed obtainer 523 with the pulse signals
output from the rotational speed sensors 4 other than the suspected abnormal sensor.
Upon completion of the selection of the pulse signals to be provided to the reference
20 rotational speed obtainer 523, the selector 522 feeds a selection completion signal
indicating completion of selection of the rotational speed sensors 4 to the power
controller 525.
[0051] Upon the completion of selection of the pulse signals to be provided to the
reference rotational speed obtainer 523, the reference rotational speed obtainer 523 is
25 provided with only the pulse signals output from the rotational speed sensors 4 other than
the suspected abnormal sensor. On the basis of the pulse signals output from the
rotational speed sensors 4 other than the suspected abnormal sensor, the reference
17
rotational speed obtainer 523 obtains a first reference rotational speed in a
reference-rotational-speed obtaining step (Step S106). In detail, on the basis of the pulse
signals output from the rotational speed sensors 4 other than the suspected abnormal
sensor, the reference rotational speed obtainer 523 obtains, as a first reference rotational
5 speed, the average of the rotational speeds of the motors 3 corresponding to the rotational
speed sensors 4 other than the suspected abnormal sensor. Upon obtaining the first
reference rotational speed, the reference rotational speed obtainer 523 outputs reference
rotational speed information indicating the first reference rotational speed.
[0052] On the basis of the operation command signal, the reference rotational speed
10 information, and the current value signals, the command value determiner 524 determines
a command value of voltage to be applied to the motors 3 in a command value
determining step (Step S107).
[0053] The power controller 525, upon receiving the selection completion signal
output from the selector 522, causes the power converter 51 to output electric power on
15 the basis of the voltage command value determined by the command value determiner
524. This control resumes the operation of the power converter 51 in a resuming step
(Step S108).
[0054] In response to the resumption of the operation of the power converter 51, the
modulation factor obtainer 526 obtains a modulation factor on the basis of the voltage
20 command value indicated by the command value information output from the command
value determiner 524, in a modulation factor obtaining step (Step S109). In detail, the
modulation factor obtainer 526 obtains a modulation factor by dividing the voltage
command value indicated by the command value information by the maximum output
voltage of the control device 5, that is, the maximum output voltage of the power
25 converter 51. The modulation factor obtainer 526 outputs modulation factor
information indicating the obtained modulation factor.
[0055] The abnormality determiner 527 then determines whether the difference
18
between the modulation factor and the comparative modulation factor is larger than or
equal to the first modulation-factor threshold on the basis of the modulation factor
information output from the modulation factor obtainer 526, and thus determines whether
the four motors 3 or the four rotational speed sensors 4 have an abnormality in an
5 abnormality determining step (Step S110). In detail, the abnormality determiner 527
determines whether the difference between the modulation factor, based on the first
reference rotational speed obtained without the pulse signals output from the suspected
abnormal sensor, and the comparative modulation factor is larger than or equal to the first
modulation-factor threshold.
10 [0056] In an exemplary case where jamming occurs in any of the motors 3, an
increase in load on the motor 3 raises the values of current in the motor 3, that is, the
current values measured by the current measurers 53, which are described above with
reference to FIG. 2, in comparison to the values of current in the case of no jamming in
the motors 3. Such increases in the current values provide a lower voltage command
15 value determined by the command value determiner 524 than the voltage command value
in the case of no jamming in the motors 3. The modulation factor is accordingly smaller
than the modulation factor in the case of no jamming in the motors 3, because the
modulation factor is calculated by dividing the voltage command value by the maximum
output voltage of the control device 5. The modulation factor has no deviation from the
20 comparative modulation factor provided that no jamming occurs in the motors 3. The
determination of whether the difference between the modulation factor and the
comparative modulation factor, which is the modulation factor in the case of no jamming
in the motors 3, is larger than or equal to the first modulation-factor threshold, thus leads
to determination of whether the four motors 3 or the four rotational speed sensor 4 have
25 an abnormality.
[0057] When determining that the difference between the modulation factor and the
comparative modulation factor is larger than or equal to the first modulation-factor
19
threshold (Step S110; Yes), the abnormality determiner 527 determines that jamming
occurs in any of the motors 3, and outputs the first abnormality occurrence information
S1 to the power controller 525 (Step S111). The power controller 525, when receiving
the first abnormality occurrence information S1, halts the operation of the power
5 converter 51. The first abnormality occurrence information S1 may also be fed to the
driver cab 6, which is described above with reference to FIG. 1. The driver cab 6, upon
receiving the first abnormality occurrence information S1, may cause the monitor in the
driver cab 6 to display information indicating jamming in the motors 3, for example.
[0058] In contrast, when determining that the difference between the modulation
10 factor and the comparative modulation factor is smaller than the first modulation-factor
threshold (Step S110; No), the abnormality determiner 527 determines that any of the
rotational speed sensors 4 has an abnormality, and outputs the second abnormality
occurrence information S2 (Step S112). The second abnormality occurrence
information S2 is fed to the driver cab 6, which is described above with reference to FIG.
15 1. The driver cab 6, upon receiving the second abnormality occurrence information S2,
causes the monitor in the driver cab 6 to display information indicating an abnormality in
the rotational speed sensors 4, for example.
[0059] The output of the first abnormality occurrence information S1 or the second
abnormality occurrence information S2 from the abnormality determiner 527 is followed
20 by termination of the control process.
[0060] As described above, a modulation factor is obtained on the basis of the first
reference rotational speed in response to the determination that the rotational speed
sensors 4 include a suspected abnormal sensor, in this embodiment. The abnormality
determiner 527 determines whether the difference between the modulation factor
25 obtained on the basis of the first reference rotational speed and the comparative
modulation factor is larger than or equal to the first modulation-factor threshold, and can
thus determine whether the motors 3 or the rotational speed sensors 4 have an
20
abnormality. That is, the embodiment can achieve determination of occurrence of an
abnormality in the rotational speed sensors 4.
[0061] As illustrated in FIG. 6, an output current has a constant value lower than
the “overcurrent set value” during feedback of the output current to the command value
5 determiner 524, regardless of jamming in the motors 3, as is described above with
reference to FIG. 3. FIG. 6 is a graph illustrating a variation in a value of current output
from the power converter 51 with and without current feedback of the output current to
the command value determiner 524. The vertical axis in FIG. 6 represents a value of
current output from the power converter 51, and the horizontal axis represents a time
10 from feeding of an operation command signal indicating a power running command
signal. The dashed line in FIG. 6 indicates a value of current output from the power
converter 51 in the case of no jamming in the motors 3.
[0062] In contrast, the velocity of the vehicle body 1 increases with time and
reaches the vehicle velocity threshold, followed by stop of the feedback of the output
15 current to the command value determiner 524. In the case where jamming occurs in any
of the motors 3, the value of output current accordingly rises and exceeds the
“overcurrent set value”. That is, the value of current actually output from the power
converter 51 can contribute to detection of jamming in the motors 3, during no feedback
of an output current to the command value determiner 524 in the vehicle body 1 running
20 at a velocity equal to or higher than the vehicle velocity threshold. The value of output
current, however, cannot contribute to determination of whether jamming occurs in the
motors 3, during feedback of an output current to the command value determiner 524 in
the vehicle body 1 running at a velocity lower than the vehicle velocity threshold.
[0063] In contrast, the modulation factor is obtained on the basis of the voltage
25 command value and the maximum output voltage of the control device 5, as is described
above with reference to FIG. 3. The modulation factor thus deviates from the
comparative modulation factor in the case where jamming occurs in any of the motors 3,
21
with or without the feedback of an output current to the command value determiner 524,
as illustrated in FIG. 7. FIG. 7 is a graph illustrating a variation in the modulation factor
with and without the feedback of an output current to the command value determiner 524.
The vertical axis in FIG. 7 represents a modulation factor, and the horizontal axis
5 represents a time from the feeding of an operation command signal indicating a power
running command signal. The dashed line in FIG. 7 indicates the modulation factor in
the case of no jamming in the motors 3, that is, the comparative modulation factor.
[0064] As described above, the embodiment can achieve determination of whether
the motors 3 or the rotational speed sensors 4 have an abnormality, even during feedback
10 of output currents to the command value determiner 524. The embodiment can thus
achieve determination of whether the difference between the modulation factor and the
comparative modulation factor is larger than or equal to the first modulation-factor
threshold, even during feedback of the output currents to the command value determiner
524 in the vehicle body 1 running at a velocity lower than the vehicle velocity threshold,
15 thus achieving determination of whether the motors 3 or the rotational speed sensors 4
have an abnormality.
[0065] The motors 3 in this embodiment require no current detection sensors at the
shafts to measure current values of the motors 3. This feature can provide simple
structures around the motors 3.
20 [0066] Although the suspected abnormal sensor determiner 521 in this embodiment
determines the existence of a suspected abnormal sensor on the basis of whether the
frequencies of pulse signals output from the four rotational speed sensors 4 are larger than
or equal to the reference frequency in the measurement period, this determination
procedure is a mere example. The suspected abnormal sensor determiner 521 may
25 determine the existence of a suspected abnormal sensor through comparison of the pulse
signals output from the four rotational speed sensors 4 with one another, for example.
In specific, the suspected abnormal sensor determiner 521 may regard the rotational
22
speed sensor 4 that outputs a pulse signal indicating the minimum rotational speed as a
suspected abnormal sensor, when the difference in the rotational speed between one
rotational speed sensor 4 that outputs the pulse signal indicating the maximum rotational
speed and another rotational speed sensor 4 that outputs the pulse signal indicating the
5 minimum rotational speed is larger than a value that is set in advance.
[0067] Embodiment 2
The following describes an electric vehicle 100 according to Embodiment 2 with
reference to FIG. 8.
[0068] Fundamental configuration and operations of the electric vehicle 100
10 according to Embodiment 2 are similar to those of the electric vehicle 100 according to
Embodiment 1. Embodiment 2 differs from Embodiment 1 in that the electric vehicle
100 includes multiple vehicle bodies 1 each provided with a control device 5, and the
control device 5 in each vehicle body 1 determines whether jamming occurs in the
motors 3 through comparison with the modulation factor obtained in the control device 5
15 in another vehicle body 1 that is different from the vehicle body 1. That is, in
Embodiment 2, the comparative modulation factor described above in Embodiment 1 is
replaced with a modulation factor obtained in the control device 5 in the other vehicle
body 1. The following focuses on the differences from Embodiment 1.
[0069] One of two vehicle bodies 1 provided with separate control devices 5 is
20 hereinafter referred to as “first vehicle body 1a”, and the other of the vehicle bodies 1 is
referred to as “second vehicle body 1b”. The control device 5 provided to the first
vehicle body 1a is referred to as “first control device 5a”, and the control device 5
provided to the second vehicle body 1b is referred to as “second control device 5b”.
That is, the first control device 5a and the second control device 5b are provided to
25 separate vehicle bodies 1. The second control device 5b has configuration similar to
that of the first control device 5a. The configuration of the first control device 5a and
the configuration of the second control device 5b are each similar to that of the control
23
device 5, which is described above with reference to FIGS. 2 and 3.
[0070] The description of Embodiment 2 assumes that the suspected abnormal
sensor determiner 521 determines that the rotational speed sensors 4 provided for the
motors 3 in the first vehicle body 1a in one-to-one correspondence include a suspected
5 abnormal sensor. Similarly to Emobodiment1, the first vehicle body 1a and the second
vehicle body 1b in Embodiment 2 each include four motors 3 and four rotational speed
sensors 4.
[0071] The suspected abnormal sensor determiner 521 determines that the four
rotational speed sensors 4 provided for the four motors 3 in the first vehicle body 1a
10 include a suspected abnormal sensor. In response to this determination, the abnormality
determiner 527 of the first control device 5a compares the modulation factor in the first
control device 5a and the modulation factor in the second control device 5b serving as the
comparative modulation factor, and thus determines whether the motors 3 or the
rotational speed sensors 4 have an abnormality. In detail, the abnormality determiner
15 527 determines whether the difference between the modulation factor obtained by the
modulation factor obtainer 526 of the first control device 5a and the modulation factor
obtained by the modulation factor obtainer 526 of the second control device 5b is larger
than or equal to a second modulation-factor threshold that is set in advance. The second
modulation-factor threshold is a threshold for determination of whether jamming occurs
20 in the motors 3, as an abnormality in the motors 3, and is another example of
“jamming-modulation-factor threshold”. The second modulation-factor threshold is
stored in the storage area of the controller 52, for example. The modulation factors in
the first control device 5a and the second control device 5b are obtained in a procedure
similar to that described above in Embodiment 1.
25 [0072] When determining that the difference between the modulation factor in the
first control device 5a and the modulation factor in the second control device 5b is larger
than or equal to the second modulation-factor threshold, the abnormality determiner 527
24
of the first control device 5a determines that jamming occurs in the motor 3
corresponding to the suspected abnormal sensor, that is, the motor 3 has an abnormality.
In contrast, when determining that the difference between the modulation factor in the
first control device 5a and the modulation factor in the second control device 5b is
5 smaller than the second modulation-factor threshold, the abnormality determiner 527
determines that the rotational speed sensor 4 has an abnormality.
[0073] Embodiment 2 described above can achieve determination of whether the
motors 3 or the rotational speed sensors 4 have an abnormality through comparison with
the modulation factor obtained in the control device 5 in the other vehicle body 1 of the
10 electric vehicle 100.
[0074] In general, jamming in a motor 3 scarcely occurs. The comparison with
the modulation factor obtained in the control device 5 in the other vehicle body 1 can thus
further improve the accuracy of determination of whether the motors 3 or the rotational
speed sensors 4 have an abnormality.
15 [0075] The second modulation-factor threshold may be equal to or different from
the first modulation-factor threshold.
[0076] Embodiment 3
The following describes an electric vehicle 100 according to Embodiment 3 with
reference to FIG. 9. Fundamental configuration and operations of the electric vehicle
20 100 according to Embodiment 3 are similar to those of the electric vehicle 100 according
to Embodiment 1 or 2. Embodiment 3 differs from Embodiment 1 or 2 in that
Embodiment 3 is aimed at determination of the occurrence of a sign of jamming as an
abnormality in the motors 3. The following focuses on the differences from
Embodiment 1 or 2. The sign of jamming means a sign appearing prior to the actual
25 occurrence of jamming. The state in which the sign of jamming occurs is a state in
which the motor 3 is implied by, for example, a rotational speed of the motor 3 within a
speed range defined by a designer or an engineer of the electric vehicle 100. The speed
25
range is defined on the basis of the difference in diameters of the wheels 2, for example.
In an exemplary case where the difference in diameters of the wheels 2 is equal to or
smaller than 6 mm, the speed range is set to be a range of speed lower than the normal
rotational speed of the motors 3 by at least 1%. In the case of occurrence of the sigh of
5 jamming, a motor 3 rotates at a higher rotational speed than in the case of occurrence of
jamming.
[0077] In order to determine a sign of jamming in the motors 3, the suspected
abnormal sensor determiner 521 in Embodiment 3 determines the existence of a
suspected abnormal sensor on the basis of the pulse signals output from the respective
10 rotational speed sensors 4. In detail, the suspected abnormal sensor determiner 521
regards the rotational speed sensor 4 that outputs a pulse signal indicating the minimum
rotational speed as a suspected abnormal sensor, when the difference between the
maximum and minimum rotational speeds among the rotational speeds of the motors 3 is
larger than or equal to a rotational-speed threshold that is set in advance. Information
15 indicating the rotational-speed threshold is stored in the storage area of the controller 52,
for example. Similarly to Embodiments 1 and 2, four motors 3 and four rotational speed
sensors 4 are included in Embodiment 3.
[0078] The suspected abnormal sensor determiner 521 obtains the maximum and
minimum rotational speeds on the basis of the pulse signals output from the respective
20 rotational speed sensors 4. The suspected abnormal sensor determiner 521 determines
whether the difference between the maximum and minimum rotational speeds is larger
than or equal to the rotational-speed threshold.
[0079] When determining that the difference between the maximum and minimum
rotational speeds is larger than or equal to the rotational-speed threshold, the suspected
25 abnormal sensor determiner 521 regards the rotational speed sensor 4 that outputs the
pulse signal indicating the minimum rotational speed as a suspected abnormal sensor.
[0080] When determining that the rotational speed sensors include a suspected
26
abnormal sensor, the suspected abnormal sensor determiner 521 outputs information
indicating the existence of a suspected abnormal sensor in the form of a determination
signal. The determination signal is fed to the selector 522, the power controller 525, and
the abnormality determiner 527.
5 [0081] The abnormality determiner 527, upon receiving the determination signal
indicating the existence of a suspected abnormal sensor from the suspected abnormal
sensor determiner 521, determines whether the difference between the modulation factor
and the comparative modulation factor is larger than or equal to a third modulation-factor
threshold that is set in advance. The third modulation-factor threshold is a threshold for
10 determination of whether a sign of jamming occurs in the motors 3, as an abnormality in
the motors 3, and is an example of “sign-modulation-factor threshold”. The third
modulation-factor threshold is stored in the storage area of the controller 52, for example.
The third modulation-factor threshold is set in advance by a designer or an engineer, for
example, depending on the level of a sign of jamming in the motors 3. The third
15 modulation-factor threshold is smaller than the first modulation-factor threshold.
[0082] In an exemplary case where a sign of jamming occurs in any of the motors 3,
an increase in load on the motor 3 raises the values of current in the motor 3, which are
measured by the current measurers 53 and actually output from the power converter 51 as
described above with reference to FIG. 2. Such increases in the current values provide a
20 lower voltage command value determined by the command value determiner 524
illustrated in FIG. 9 than the voltage command value in the case of no sign of jamming in
the motors 3. The modulation factor is accordingly smaller than the modulation factor
in the case of no jamming in the motors 3. The modulation factor has no deviation from
the comparative modulation factor provided that no jamming occurs in the motors 3.
25 [0083] The abnormality determiner 527, when determining that the difference
between the modulation factor and the comparative modulation factor is larger than or
equal to the third modulation-factor threshold, determines that a sigh of occurrence of
27
jamming in the motors 3 exists, and outputs third abnormality occurrence information S3
indicating the existence of a sign of jamming in the motors 3. The third abnormality
occurrence information S3 in this embodiment is fed to the driver cab 6, similarly to the
second abnormality occurrence information S2. The driver cab 6, upon receiving the
5 third abnormality occurrence information S3, causes the monitor in the driver cab 6 to
display information indicating the occurrence of a sign of jamming in the motors 3, for
example.
[0084] Embodiment 3 described above can achieve determination of whether the
difference between the modulation factor and the comparative modulation factor is larger
10 than or equal to the third modulation-factor threshold that is set in advance, thus
achieving determination of whether a sign of jamming occurs in the motors 3.
[0085] The above-described embodiments are not to be construed as limiting the
scope of the present disclosure. Other embodiments as a result of appropriate
modifications are also available.
15 [0086] For example, Embodiments 1 to 3 may be appropriately combined with one
another. In detail, the abnormality determiner 527 may determine whether a sign of
jamming occurs in the motors 3 as in Embodiment 3, through comparison with the
modulation factor obtained in the control device 5 in the other vehicle body 1 as in
Embodiment 2. The suspected abnormal sensor determiner 521 may output a
20 determination signal containing both pieces of information described in Embodiments 1
and 3. In this case, the abnormality determiner 527 outputs the first abnormality
occurrence information S1, when receiving a determination signal indicating the
existence of a suspected abnormal sensor implying occurrence of jamming, from the
suspected abnormal sensor determiner 521. The abnormality determiner 527 outputs the
25 third abnormality occurrence information S3, when receiving a determination signal
indicating the existence of a suspected abnormal sensor implying a motor 3 showing a
sign of jamming. These two types of abnormality occurrence information enable the
28
control device 5 to discriminate the occurrence of jamming in the motors 3, the
occurrence of a sign of jamming in the motors 3, and the occurrence of an abnormality in
the rotational speed sensors 4 from one another.
[0087] Although each control device 5 feeds electric power to four motors 3 in the
5 present disclosure, this configuration is a mere example. The number of motors 3 fed
with electric power from each control device 5 may be any number at least two.
[0088] Although the power converter 51 includes the inverter unit, this
configuration is a mere example. The power converter 51 may include any power
conversion unit.
10 [0089] Although the control devices 5 are installed in motor cars, this configuration
is a mere example. The control devices 5 may also be installed in the vehicle bodies 1
other than motor cars. In this case, the control devices 5 are connected to the motors 3
and the rotational speed sensors 4 with cables, for example.
Reference Signs List
15 [0090] 1 Vehicle body
1a First vehicle body
1b Second vehicle body
2 Wheel
3 Motor
20 4 Rotational speed sensor (first suspected abnormal sensor, second suspected
abnormal sensor)
5 Control device
6 Driver cab
51 Power converter
25 52 Controller
53 Current measurer
5a First control device
29
5b Second control device
61 Master controller
100 Electric vehicle
521 Suspected abnormal sensor determiner
5 522 Selector
523 Reference rotational speed obtainer
524 Command value determiner
525 Power controller
526 Modulation factor obtainer
10 527 Abnormality determiner
S1 First abnormality occurrence information
S2 Second abnormality occurrence information
S3 Third abnormality occurrence information

We Claim:
[Claim 1] A control device for controlling operations of a plurality of motors of
an electric railway vehicle running in accordance with an operation command signal, the
5 control device comprising:
a power converter to feed electric power to each of the plurality of motors;
a suspected abnormal sensor determiner to determine, based on signals that are
output from a plurality of rotational speed sensors provided for the plurality of motors in
one-to-one correspondence and that indicate rotational speeds of the plurality of motors,
10 whether the plurality of rotational speed sensors include a suspected abnormal sensor
suspected of having an abnormality, each of the signals being output from a
corresponding rotational speed sensor of the plurality of rotational speed sensors and
indicating a rotational speed of a corresponding motor of the plurality of motors;
a reference rotational speed obtainer to obtain a reference rotational speed, based
15 on one or more signals that are output from the plurality of rotational speed sensors other
than the suspected abnormal sensor and that each indicate the rotational speed, when the
suspected abnormal sensor determiner determines that the plurality of rotational speed
sensors include the suspected abnormal sensor, each of the one or more signals being
output from a corresponding rotational speed sensor of the plurality of rotational speed
20 sensors other than the suspected abnormal sensor;
a command value determiner to determine a command value of voltage to be
output from the power converter, based on the operation command signal, the reference
rotational speed, and values of current fed from the power converter to the plurality of
motors;
25 a modulation factor obtainer to obtain a modulation factor, based on the command
value of voltage; and
an abnormality determiner to
31
determine that a motor of the plurality of motors that corresponds to the
suspected abnormal sensor has an abnormality, when a difference between the
modulation factor and a comparative modulation factor that is set in advance is larger
than or equal to a modulation-factor threshold, and
5 determine that the suspected abnormal sensor has an abnormality, when the
difference between the modulation factor and the comparative modulation factor is
smaller than the modulation-factor threshold.
[Claim 2] The control device according to claim 1, wherein
10 the suspected abnormal sensor determiner
obtains a maximum value and a minimum value of the rotational speeds,
based on the signals that are output from the plurality of rotational speed sensors and that
each indicate the rotational speed, and
when determining that a difference between the maximum value and the
15 minimum value of the rotational speeds is larger than or equal to a rotational-speed
threshold, regards a rotational speed sensor that outputs a signal indicating the minimum
value of the rotational speeds as the suspected abnormal sensor.
[Claim 3] The control device according to claim 1 or 2, wherein
20 the modulation-factor threshold includes a jamming-modulation-factor threshold
designed for determination of whether jamming occurs in the plurality of motors as an
abnormality in the plurality of motors, and
when the difference between the modulation factor and the comparative
modulation factor is larger than or equal to the jamming-modulation-factor threshold, the
25 abnormality determiner determines that jamming occurs in the motor corresponding to
the suspected abnormal sensor.
32
[Claim 4] The control device according to claim 2, wherein
the modulation-factor threshold includes a sign-modulation-factor threshold
designed for determination of whether a sign of jamming occurs in the plurality of motors
as an abnormality in the plurality of motors, and
5 when the difference between the modulation factor and the comparative
modulation factor is larger than or equal to the sign-modulation-factor threshold, the
abnormality determiner determines that a sign of jamming occurs in the motor
corresponding to the suspected abnormal sensor.
10 [Claim 5] The control device according to any one of claims 1 to 4, wherein,
when the rotational speeds of the plurality of motors are lower than a threshold speed, the
command value determiner determines the command value of voltage, based on the
operation command signal, the reference rotational speed, and the values of current fed
from the power converter to the plurality of motors, within such a range that the values of
15 current fed from the power converter to the plurality of motors are equal to or lower than
a reference value.
[Claim 6] An electric railway vehicle, comprising:
a plurality of the control devices according to any one of claims 1 to 5, the plurality
20 of control devices including a first control device and a second control device different
from the first control device, wherein
the abnormality determiner included in the first control device determines whether
the plurality of motors or the plurality of rotational speed sensors have an abnormality,
through comparison between (i) a modulation factor in the first control device as the
25 modulation factor and (ii) a modulation factor in the second control device as the
comparative modulation factor.
33
[Claim 7] A control method for controlling operations of a plurality of motors of
an electric railway vehicle running in accordance with an operation command signal, the
control method comprising:
a power feeding step of feeding electric power to each of the plurality of motors;
5 a suspected-abnormal-sensor determining step of determining, based on signals
that are output from a plurality of rotational speed sensors provided for the plurality of
motorsin one-to-one correspondence and that indicate rotational speeds of the plurality of
motors, whether the plurality of rotational speed sensors include a suspected abnormal
sensor suspected of having an abnormality, each of the signals being output from a
10 corresponding rotational speed sensor of the plurality of rotational speed sensors and
indicating a rotational speed of a corresponding motor of the plurality of motors;
a reference-rotational-speed obtaining step of obtaining a reference rotational
speed, based on one or more signals that are output from the plurality of rotational speed
sensors other than the suspected abnormal sensor and that each indicate the rotational
15 speed, when the plurality of rotational speed sensors are determined to include the
suspected abnormal sensor, each of the one or more signals being output from a
corresponding rotational speed sensor of the plurality of rotational speed sensors other
than the suspected abnormal sensor;
a command value determining step of determining a command value of voltage to
20 be applied to the plurality of motors, based on the operation command signal, the
reference rotational speed, and values of current fed to the plurality of motors in the
power feeding step;
a modulation factor obtaining step of obtaining a modulation factor, based on the
command value of voltage; and
25 an abnormality determining step of
determining that a motor of the plurality of motors that corresponds to the
suspected abnormal sensor has an abnormality, when a difference between the
34
modulation factor and a comparative modulation factor that is set in advance is larger
than or equal to a modulation-factor threshold, and
determining that the suspected abnormal sensor has an abnormality, when
the difference between the modulation factor and the comparative modulation factor is
5 smaller than the modulation-factor threshold