FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
BRAKE CONTROL DEVICE AND BRAKE 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 100-8310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.
2
DESCRIPTION
TITLE OF THE INVENTION:
BRAKE CONTROL DEVICE AND BRAKE CONTROL METHOD
5
Field
[0001] The present disclosure relates to a brake control
device and a brake control method to be used in a railway
vehicle.
10
Background
[0002] When a strong brake is applied to a traveling
railway vehicle to lock a wheel, the wheel slides on a rail
and wears, and a flat surface, that is, a flat is formed on
the wheel. When the flat is formed on the wheel, it15
becomes difficult for the wheel to rotate smoothly, which
causes noise, vibration, and the like. An anti-lock brake
system is a system that prevents locking of wheels by
adjusting a braking force for each axle or each truck of a
railway vehicle in order to prevent wear of wheels due to20
such wheel locking. Patent Literature 1 discloses a
technique for an anti-lock brake system for a railway
vehicle capable of preventing a wheel from locking, and
adequately braking the wheel according to a kind of the
brake while maintaining brake performance by maintaining a25
brake cylinder pressure at high value to give a braking
force.
Citation List
Patent Literature30
[0003] Patent Literature 1: JP 2005-289172 A
Summary of Invention
3
Problem to be solved by the Invention
[0004] However, according to the above-described related
art, wear of the wheel is prevented by weakening the
braking force. Therefore, there has been a problem that an
actual braking distance may extend with respect to a target5
braking distance until the railway vehicle stops.
[0005] The present disclosure has been made in view of
the above, and an object thereof is to obtain a brake
control device capable of preventing sliding of a wheel
while preventing extension of a braking distance.10
Means to Solve the Problem
[0006] In order to solve the above problem and achieve
the object, the present disclosure is a brake control
device for controlling a first brake device that presses a15
friction material against a wheel to obtain a braking force
and a second brake device that does not use the friction
material, in a railway vehicle. The brake control device
includes: a wheel load estimation unit to estimate a wheel
load that is a load received by the wheel from the friction20
material, based on a wheel speed and a brake force applied
to the wheel by the friction material; a friction surface
state quantity estimation unit to estimate a friction
coefficient of current time of the friction material from a
state of a friction surface of the friction material based25
on the wheel load, the wheel speed, and a brake force
command, and output a mirror-surfacing signal indicating
that the friction surface is in a mirror-surfaced state
when the friction coefficient is less than a prescribed
first threshold value; and a brake control unit to control30
operations of the first brake device and the second brake
device, based on the brake force command and presence or
absence of the mirror-surfacing signal.
4
Effects of the Invention
[0007] The brake control device of the present
disclosure has an effect of preventing sliding of a wheel
while preventing extension of a braking distance.5
Brief Description of Drawings
[0008] FIG. 1 is a diagram illustrating a configuration
example of a brake control device according to an
embodiment.10
FIG. 2 is a flowchart illustrating an operation of the
brake control device according to the embodiment.
FIG. 3 is a diagram illustrating a configuration
example of a friction surface state quantity estimation
unit according to the embodiment.15
FIG. 4 is a flowchart illustrating an operation of the
friction surface state quantity estimation unit according
to the embodiment.
FIG. 5 is a diagram illustrating a configuration
example of processing circuitry in a case where processing20
circuitry included in the brake control device according to
the embodiment is implemented by a processor and a memory.
FIG. 6 is a diagram illustrating a configuration
example of processing circuitry in a case where processing
circuitry included in the brake control device according to25
the embodiment is implemented by dedicated hardware.
Description of Embodiments
[0009] Hereinafter, a brake control device and a brake
control method according to an embodiment of the present30
disclosure will be described in detail with reference to
the drawings.
[0010] Embodiment.
5
FIG. 1 is a diagram illustrating a configuration
example of a brake control device 10 according to the
present embodiment. The brake control device 10 is a
device to be mounted on a railway vehicle 70. In the
railway vehicle 70, the brake control device 10 controls a5
first brake device 50 and a second brake device 60 to
obtain a desired brake force.
[0011] The first brake device 50 is a brake device that
presses a friction material 51 against a wheel 71 of the
railway vehicle 70 to obtain the braking force. The first10
brake device 50 is, for example, a pneumatic brake device.
The friction material 51 is a brake shoe that presses a
tread surface of the wheel 71, a friction pad that presses
a side surface of the wheel 71 or a disk attached to an
axle of the wheel 71, or the like. The second brake device15
60 is a brake device that obtains a braking force without
using the friction material 51 as described above. The
second brake device 60 is, for example, a regenerative
brake device. Note that the railway vehicle 70 may include
a plurality of second brake devices 60 of different types.20
In this case, the brake control device 10 controls the
first brake device 50 and the plurality of second brake
devices 60 to obtain a desired brake force. The brake
control device 10 controls individual brake devices such
that a total value of brake forces obtained from the25
individual brake devices becomes a desired brake force.
[0012] A configuration and an operation of the brake
control device 10 will be described. As illustrated in
FIG. 1, the brake control device 10 includes a wheel load
estimation unit 20, a friction surface state quantity30
estimation unit 30, and a brake control unit 40. FIG. 2 is
a flowchart illustrating an operation of the brake control
device 10 according to the present embodiment.
6
[0013] The wheel load estimation unit 20 estimates a
wheel load Q which is a load received by the wheel 71 from
the friction material 51, on the basis of a wheel speed and
a brake force applied to the wheel 71 by the friction
material 51 (step S101). The brake force is a braking5
force obtained by pressing the friction material 51 against
the wheel 71 in the first brake device 50. Note that the
braking force obtained by pressing the friction material 51
against the wheel 71 actually varies depending on a state
of a friction surface of the friction material 51, but10
here, it is assumed that the state of the friction surface
of the friction material 51 is in a constant state. The
state in which the friction surface of the friction
material 51 is in a constant state is a state in which a
friction coefficient μ is within a prescribed range in the15
entire region of the friction surface of the friction
material 51 that actually presses the tread surface of the
wheel 71, the side surface of the wheel 71, the disk
attached to the axle, and the like. The wheel load
estimation unit 20 acquires the brake force and the wheel20
speed from a vehicle control device (not illustrated) or
the like that is mounted on the railway vehicle 70 and
controls traveling of the railway vehicle 70.
[0014] The friction surface state quantity estimation
unit 30 estimates a friction surface state quantity W,25
which is a state of the friction surface of the friction
material 51, on the basis of the wheel load Q estimated by
the wheel load estimation unit 20, the wheel speed, and a
brake force command (step S102). The friction surface
state quantity W is expressed by a numerical value, and can30
be obtained by computation as described later. The
friction surface state quantity estimation unit 30
estimates a current friction coefficient μ of the friction
7
material 51 from the estimated friction surface state
quantity W. In a case where the estimated friction
coefficient μ is less than a prescribed first threshold
value, the friction surface state quantity estimation unit
30 outputs a mirror-surfacing signal indicating that the5
friction surface of the friction material 51 is in a
mirror-surfaced state. The brake force command is a
command output from the above-described vehicle control
device or the like, and is a brake command indicating
deceleration or the like, a brake release command for10
releasing the brake command, and the like. The first
threshold value is a threshold value to be used when the
friction surface state quantity estimation unit 30
determines whether or not to output the mirror-surfacing
signal. The friction surface state quantity estimation15
unit 30 estimates the friction surface state quantity W of
the friction material 51 on the basis of an integrated
value of a workload in a period from the current time to a
prescribed time in the past, and determines a sign of
mirror surfacing of the surface state of the friction20
material 51 in accordance with the estimated friction
surface state quantity W. The detailed configuration and
operation of the friction surface state quantity estimation
unit 30 will be described later.
[0015] The brake control unit 40 controls operations of25
the first brake device 50 and the second brake device 60 on
the basis of the brake force command and presence or
absence of the mirror-surfacing signal (step S103).
Specifically, upon acquiring the mirror-surfacing signal,
the brake control unit 40 performs control such that, in30
the next braking operation, a brake force of the first
brake device 50 increases with respect to a ratio of the
brake force of the first brake device 50 and a brake force
8
of the second brake device 60 in a brake force applied to
the railway vehicle 70 when the mirror-surfacing signal is
not acquired. Upon acquiring the mirror-surfacing signal,
the brake control unit 40 performs control such that a
brake cylinder pressure for pressing the friction material5
51 against the wheel 71 in the first brake device 50
increases as compared with a case where the mirror-
surfacing signal is not acquired. Upon acquiring the
mirror-surfacing signal, the brake control unit 40 performs
control such that a brake force obtained by the second10
brake device 60 decreases as compared with a case where the
mirror-surfacing signal is not acquired. For example, a
brake force of the first brake device 50 applied to the
railway vehicle 70 when the mirror-surfacing signal is not
acquired is defined as R1, and a brake force of the second15
brake device 60 applied to the railway vehicle 70 when the
mirror-surfacing signal is not acquired is defined as R2.
In addition, a brake force of the first brake device 50
applied to the railway vehicle 70 when the mirror-surfacing
signal is acquired is defined as R3, and a brake force of20
the second brake device 60 applied to the railway vehicle
70 when the mirror-surfacing signal is acquired is defined
as R4. In this case, the brake control unit 40 controls
operations of the first brake device 50 and the second
brake device 60 so as to satisfy (R3/R4)>(R1/R2).25
[0016] In the brake control device 10, the brake control
unit 40 improves a surface state of the friction material
51 by increasing a ratio of the first brake device 50, that
is, the pneumatic brake device, and prevents mirror
surfacing of the friction material 51 by recovering the30
friction coefficient μ. Generally, when the wheel load Q
is small, the friction surface of the friction material 51
is to be mirror surfaced, so that the friction coefficient
9
μ decreases. Whereas, by applying a large wheel load Q to
the friction material 51 for a certain period of time, the
friction surface of the friction material 51 becomes
moderately rough and the friction coefficient μ increases.
The state of the friction surface of the friction material5
51 changes depending on a brake braking history during
traveling of the railway vehicle 70. Therefore, the
friction surface state quantity estimation unit 30
periodically estimates the friction surface state quantity
W of the friction material 51 during traveling of the10
railway vehicle 70.
[0017] The detailed configuration and operation of the
friction surface state quantity estimation unit 30 will be
described. FIG. 3 is a diagram illustrating a
configuration example of the friction surface state15
quantity estimation unit 30 according to the present
embodiment. The friction surface state quantity estimation
unit 30 includes a traveling determination unit 31, a
friction surface state quantity update amount computation
unit 32, a friction surface state quantity update unit 33,20
and a mirror-surfacing determination unit 34. FIG. 4 is a
flowchart illustrating an operation of the friction surface
state quantity estimation unit 30 according to the present
embodiment. The flowchart illustrated in FIG. 4
illustrates details of the operation in step S102 of the25
flowchart illustrated in FIG. 2.
[0018] The traveling determination unit 31 determines
whether or not the railway vehicle 70 is traveling, on the
basis of a wheel speed (step S201). The traveling
determination unit 31 outputs a determination result to the30
friction surface state quantity update amount computation
unit 32. When the acquired wheel speed is equal to or
larger than a preset threshold value, the traveling
10
determination unit 31 determines that the railway vehicle
70 is traveling. The threshold value used by the traveling
determination unit 31 is, for example, 5.0 [km/h].
[0019] When the friction surface state quantity update
amount computation unit 32 acquires a determination result5
indicating that the railway vehicle 70 is not traveling
from the traveling determination unit 31 (step S202: No),
the friction surface state quantity update amount
computation unit 32 finishes the operation. When the
friction surface state quantity update amount computation10
unit 32 acquires a determination result indicating that the
railway vehicle 70 is traveling from the traveling
determination unit 31 (step S202: Yes), the friction
surface state quantity update amount computation unit 32
computes a friction surface state quantity update amount ΔW15
of the friction material 51 on the basis of the wheel load
Q (step S203). The friction surface state quantity update
amount computation unit 32 outputs the computed friction
surface state quantity update amount ΔW to the friction
surface state quantity update unit 33. The friction20
surface state quantity update amount computation unit 32
sets a second threshold value for the wheel load Q, and
computes the friction surface state quantity update amount
ΔW on the basis of a comparison result between the wheel
load Q and the second threshold value. The second25
threshold value is a threshold value to be used when the
friction surface state quantity update amount computation
unit 32 computes the friction surface state quantity update
amount ΔW. The friction surface state quantity update
amount computation unit 32 computes the friction surface30
state quantity update amount ΔW=A×Q when the wheel load Q
is equal to or larger than the second threshold value, and
computes the friction surface state quantity update amount
11
ΔW=B×Q when the wheel load Q is less than the second
threshold value. Here, A and B are correction
coefficients. The correction coefficients A and B are set
in advance from material properties of the friction
material 51 and the like. In a case where it is defined5
that the friction coefficient μ is to be in a high and
favorable state as the friction surface state quantity W
increases, the correction coefficient A≥0 and the
correction coefficient B≤0 are satisfied. Note that the
case where the correction coefficients A and B are 0 is a10
case where update of the friction surface state quantity W
by the wheel load Q is ignored. In this way, when the
wheel load Q is equal to or larger than the prescribed
second threshold value, the friction surface state quantity
update amount computation unit 32 sets, as the friction15
surface state quantity update amount ΔW, a value obtained
by multiplying the wheel load Q by the correction
coefficient A, which is a first coefficient equal to or
larger than 0. Further, when the wheel load Q is less than
the prescribed second threshold value, the friction surface20
state quantity update amount computation unit 32 sets, as
the friction surface state quantity update amount ΔW, a
value obtained by multiplying the wheel load Q by the
correction coefficient B, which is a second coefficient
equal to or less than 0.25
[0020] The friction surface state quantity update unit
33 updates the friction surface state quantity W, which is
a state of the friction material 51, on the basis of the
friction surface state quantity update amount ΔW and the
brake force command (step S204). The friction surface30
state quantity update unit 33 outputs the friction surface
state quantity W desired to be updated, to the mirror-
surfacing determination unit 34. The friction surface
12
state quantity update unit 33 internally holds the friction
surface state quantity W, and updates the friction surface
state quantity W by setting W←σW+ΔW, on the basis of the
friction surface state quantity update amount ΔW acquired
from the friction surface state quantity update amount5
computation unit 32. Here, σ is a forgetting factor and is
set to σ ≤ 1. In order to prevent a controller (not
illustrated) of the railway vehicle 70 from becoming
unstable due to a fluctuation of the friction coefficient μ
when the brake command is output, the friction surface10
state quantity update unit 33 updates the friction surface
state quantity W at a timing when the brake force command
changes from the braking command to the brake release
command. In this manner, the friction surface state
quantity update unit 33 updates the friction surface state15
quantity W as a new friction surface state quantity W, by
multiplying the friction surface state quantity W obtained
in the previous computation by the prescribed forgetting
factor σ and adding the friction surface state quantity
update amount ΔW to the multiplication result.20
[0021] The mirror-surfacing determination unit 34
estimates the friction coefficient μ from the friction
surface state quantity W (step S205). The mirror-surfacing
determination unit 34 outputs a mirror-surfacing signal to
the brake control unit 40 when the friction coefficient μ25
is less than the first threshold value. Specifically, the
mirror-surfacing determination unit 34 compares the
estimated friction coefficient μ with the preset first
threshold value (step S206). When the friction coefficient
μ is less than the first threshold value (step S206: Yes),30
the mirror-surfacing determination unit 34 outputs the
mirror-surfacing signal to the brake control unit 40 (step
S207). The mirror-surfacing determination unit 34 may
13
output information about the friction coefficient μ or
information about a degree of mirror surfacing, to the
brake control unit 40 together with the mirror-surfacing
signal. When the friction coefficient μ is equal to or
larger than the first threshold value (step S206: No), the5
mirror-surfacing determination unit 34 finishes the
operation without outputting the mirror-surfacing signal.
[0022] As a result, in the brake control device 10, the
brake control unit 40 having acquired the mirror-surfacing
signal increases a ratio of the brake force of the first10
brake device 50, that is, the pneumatic brake device at the
time of the brake command, so that the surface state of the
friction material 51 can be improved and the friction
coefficient μ of the friction material 51 can be recovered.
When the brake control device 10 further acquires the15
information about the friction coefficient μ or the
information about the degree of mirror surfacing, the brake
control device 10 may change the ratio of the brake force
of the pneumatic brake device in accordance with the
friction coefficient μ or the degree of mirror surfacing.20
[0023] Next, a hardware configuration of the brake
control device 10 according to the present embodiment will
be described. In the brake control device 10, the wheel
load estimation unit 20, the friction surface state
quantity estimation unit 30, and the brake control unit 4025
are implemented by processing circuitry. The processing
circuitry may be a memory that stores a program and a
processor that executes the program stored in the memory,
or may be dedicated hardware. The processing circuitry is
also referred to as a control circuit.30
[0024] FIG. 5 is a diagram illustrating a configuration
example of processing circuitry 90 in a case where
processing circuitry included in the brake control device
14
10 according to the present embodiment is implemented by a
processor 91 and a memory 92. The processing circuitry 90
illustrated in FIG. 5 is a control circuit, and includes
the processor 91 and the memory 92. In a case where the
processing circuitry 90 is configured with the processor 915
and the memory 92, each function of the processing
circuitry 90 is implemented by software, firmware, or a
combination of software and firmware. The software or the
firmware is described as a program and stored in the memory
92. In the processing circuitry 90, the processor 91 reads10
and executes the program stored in the memory 92 to
implement each function. That is, the processing circuitry
90 includes the memory 92 for storage of a program by which
processing of the brake control device 10 is executed as a
result. This program can also be said as a program for15
causing the brake control device 10 to execute each
function implemented by the processing circuitry 90. This
program may be provided by means of a storage medium in
which the program is stored, or may be provided by means of
other means such as a communication medium.20
[0025] The program described above can also be said as a
program for causing the brake control device 10 to execute:
a first step, by the wheel load estimation unit 20, of
estimating a wheel load Q which is a load received by the
wheel 71 from the friction material 51, on the basis of a25
wheel speed and a brake force applied to the wheel 71 by
the friction material 51; a second step, by the friction
surface state quantity estimation unit 30, of estimating a
friction coefficient μ of current time of the friction
material 51 from a state of the friction surface of the30
friction material 51 on the basis of the wheel load Q, the
wheel speed, and a brake force command, and outputting a
mirror-surfacing signal indicating that the friction
15
surface is in a mirror-surfaced state when the friction
coefficient μ is less than a prescribed first threshold
value; and a third step, by the brake control unit 40, of
controlling operations of the first brake device 50 and the
second brake device 60 on the basis of the brake force5
command and presence or absence of the mirror-surfacing
signal.
[0026] Here, the processor 91 is, for example, a central
processing unit (CPU), a processing device, an arithmetic
device, a microprocessor, a microcomputer, a digital signal10
processor (DSP), or the like. Further, the memory 92
corresponds to a nonvolatile or volatile semiconductor
memory such as a random access memory (RAM), a read only
memory (ROM), a flash memory, an erasable programmable ROM
(EPROM), or an electrically EPROM (EEPROM, registered15
trademark), a magnetic disk, a flexible disk, an optical
disk, a compact disk, a mini disk, or a digital versatile
disc (DVD).
[0027] FIG. 6 is a diagram illustrating a configuration
example of processing circuitry 93 in a case where20
processing circuitry included in the brake control device
10 according to the present embodiment is implemented by
dedicated hardware. The processing circuitry 93
illustrated in FIG. 6 corresponds to, for example, a single
circuit, a composite circuit, a programmed processor, a25
parallel-programmed processor, an application specific
integrated circuit (ASIC), a field programmable gate array
(FPGA), or a combination thereof. Note that a part of the
processing circuitry 93 may be implemented by dedicated
hardware, and a part may be implemented by software or30
firmware. In this manner, the processing circuitry 93 can
implement the individual functions described above by
dedicated hardware, software, firmware, or a combination
16
thereof.
[0028] As described above, according to the present
embodiment, the brake control device 10 has estimated the
friction surface state quantity W of the friction material
51 of the first brake device 50 that is a pneumatic brake,5
and increased a ratio of the first brake device 50, that
is, a pneumatic braking ratio to a preset value when the
brake is applied next time in the railway vehicle 70, when
there is a sign of mirror surfacing on the friction surface
of the friction material 51. As a result, the brake10
control device 10 can improve the surface state of the
friction material 51 and prevent mirror surfacing of the
friction material 51. As a result, the brake control
device 10 can achieve a target braking distance without
weakening a braking force, by preventing occurrence of15
sliding of the wheel 71 of the railway vehicle 70 in
advance. The brake control device 10 can prevent sliding
of the wheel 71 while preventing extension of the braking
distance of the railway vehicle 70.
[0029] The configurations illustrated in the above20
embodiment illustrate one example and can be combined with
another known technique, and it is also possible to combine
embodiments with each other and omit and change a part of
the configuration without departing from the subject matter
of the present disclosure.25
Reference Signs List
[0030] 10 brake control device; 20 wheel load
estimation unit; 30 friction surface state quantity
estimation unit; 31 traveling determination unit; 3230
friction surface state quantity update amount computation
unit; 33 friction surface state quantity update unit; 34
mirror-surfacing determination unit; 40 brake control
17
unit; 50 first brake device; 51 friction material; 60
second brake device; 70 railway vehicle; 71 wheel.
18
We Claim :
[Claim 1] A brake control device for controlling a first
brake device that presses a friction material against a
wheel to obtain a braking force and a second brake device
that does not use the friction material, in a railway5
vehicle, the brake control device comprising:
a wheel load estimation unit to estimate a wheel load
that is a load received by the wheel from the friction
material, based on a wheel speed and a brake force applied
to the wheel by the friction material;10
a friction surface state quantity estimation unit to
estimate a friction coefficient of current time of the
friction material from a state of a friction surface of the
friction material based on the wheel load, the wheel speed,
and a brake force command, and output a mirror-surfacing15
signal indicating that the friction surface is in a mirror-
surfaced state when the friction coefficient is less than a
prescribed first threshold value; and
a brake control unit to control operations of the
first brake device and the second brake device, based on20
the brake force command and presence or absence of the
mirror-surfacing signal.
[Claim 2] The brake control device according to claim 1,
wherein25
when the brake control unit acquires the mirror-
surfacing signal, the brake control unit performs control
such that a brake force of the first brake device increases
with respect to a ratio of the brake force of the first
brake device and a brake force of the second brake device30
in a brake force applied to the railway vehicle when the
mirror-surfacing signal is not acquired.
19
[Claim 3] The brake control device according to claim 1 or
2, wherein
the friction surface state quantity estimation unit
includes:
a traveling determination unit to determine whether or5
not the railway vehicle is traveling based on the wheel
speed, and output a determination result;
a friction surface state quantity update amount
computation unit to compute a friction surface state
quantity update amount of the friction material based on10
the wheel load, upon acquiring a determination result
indicating that the railway vehicle is traveling;
a friction surface state quantity update unit to
update a friction surface state quantity that is a state of
the friction material, based on the friction surface state15
quantity update amount and the brake force command; and
a mirror-surfacing determination unit to estimate the
friction coefficient from the friction surface state
quantity and output the mirror-surfacing signal when the
friction coefficient is less than the first threshold20
value.
[Claim 4] The brake control device according to claim 3,
wherein
the friction surface state quantity update amount25
computation unit sets, as the friction surface state
quantity update amount, a value obtained by multiplying the
wheel load by a first coefficient of 0 or more when the
wheel load is equal to or larger than a prescribed second
threshold value, and sets, as the friction surface state30
quantity update amount, a value obtained by multiplying the
wheel load by a second coefficient of 0 or less when the
wheel load is less than a prescribed second threshold
20
value, and
the friction surface state quantity update unit
updates the friction surface state quantity as the friction
surface state quantity that is new, by multiplying the
friction surface state quantity obtained by previous5
computation by a prescribed forgetting factor and adding
the friction surface state quantity update amount.
[Claim 5] A brake control method for a brake control device
to control a first brake device that presses a friction10
material against a wheel to obtain a braking force and a
second brake device that does not use the friction
material, in a railway vehicle, the brake control method
comprising:
a first step, by a wheel load estimation unit, of15
estimating a wheel load that is a load received by the
wheel from the friction material, based on a wheel speed
and a brake force applied to the wheel by the friction
material;
a second step, by a friction surface state quantity20
estimation unit, of estimating a friction coefficient of
current time of the friction material from a state of a
friction surface of the friction material based on the
wheel load, the wheel speed, and a brake force command, and
outputting a mirror-surfacing signal indicating that the25
friction surface is in a mirror-surfaced state when the
friction coefficient is less than a prescribed first
threshold value; and
a third step, by a brake control unit, of controlling
operations of the first brake device and the second brake30
device, based on the brake force command and presence or
absence of the mirror-surface state signal.
21
[Claim 6] The brake control method according to claim 5,
wherein
in the third step, when the brake control unit
acquires the mirror-surfacing signal, the brake control
unit performs control such that a brake force of the first5
brake device increases with respect to a ratio of the brake
force of the first brake device and a brake force of the
second brake device in a brake force applied to the railway
vehicle when the mirror-surfacing signal is not acquired.
10
[Claim 7] The brake control method according to claim 5 or
6, wherein
the friction surface state quantity estimation unit
includes a traveling determination unit, a friction surface
state quantity update amount computation unit, a friction15
surface state quantity update unit, and a mirror-surfacing
determination unit, and
the second step includes:
a traveling determination step, by the traveling
determination unit, of determining whether or not the20
railway vehicle is traveling based on the wheel speed, and
outputting a determination result;
a friction surface state quantity update amount
computation step, by the friction surface state quantity
update amount computation unit, of computing a friction25
surface state quantity update amount of the friction
material based on the wheel load, upon acquiring a
determination result indicating that the railway vehicle is
traveling;
a friction surface state quantity updating step, by30
the friction surface state quantity update unit, of
updating a friction surface state quantity that is a state
of the friction material, based on the friction surface
22
state quantity update amount and the brake force command;
and
a mirror-surfacing determination step, by the mirror-
surfacing determination unit, of estimating the friction
coefficient from the friction surface state quantity and5
outputting the mirror-surfacing signal when the friction
coefficient is less than the first threshold value.
[Claim 8] The brake control method according to claim 7,
wherein10
in the friction surface state quantity update amount
computation step, the friction surface state quantity
update amount computation unit sets, as the friction
surface state quantity update amount, a value obtained by
multiplying the wheel load by a first coefficient of 0 or15
more when the wheel load is equal to or larger than a
prescribed second threshold value, and sets, as the
friction surface state quantity update amount, a value
obtained by multiplying the wheel load by a second
coefficient of 0 or less when the wheel load is less than a20
prescribed second threshold value, and
in the friction surface state quantity updating step,
the friction surface state quantity update unit updates the
friction surface state quantity as the friction surface
state quantity that is new, by multiplying the friction25
surface state quantity obtained by previous computation by
a prescribed forgetting factor and adding the friction
surface state quantity update amount.