U.S. patent application number 09/357341 was filed with the patent office on 2001-11-29 for electromechanical braking system with power distribution and redundancy.
Invention is credited to BROWN, ROLLIN W., BRUNDRETT, ROBERT L., CORIO, LAWRENCE F., RALEA, MIHAI.
Application Number | 20010045771 09/357341 |
Document ID | / |
Family ID | 23405200 |
Filed Date | 2001-11-29 |
United States Patent
Application |
20010045771 |
Kind Code |
A1 |
CORIO, LAWRENCE F. ; et
al. |
November 29, 2001 |
ELECTROMECHANICAL BRAKING SYSTEM WITH POWER DISTRIBUTION AND
REDUNDANCY
Abstract
An electromechanical braking system utilizes redundancy features
to provide safe and reliable braking. The braking system is
configured to operate on power provided by multiple power sources.
Different modes of braking are available based on whether a failure
has occurred in one or more power sources. Additionally, system
redundancy allows for failure in one or more primary components
without total loss of braking capacity. Proportional braking is
provided even in an emergency braking mode.
Inventors: |
CORIO, LAWRENCE F.; (TROY,
OH) ; BRUNDRETT, ROBERT L.; (TROY, OH) ;
RALEA, MIHAI; (BOONTON, NJ) ; BROWN, ROLLIN W.;
(COLCHESTER, VT) |
Correspondence
Address: |
MARK D SARALINO
RENNER OTTO BOISSELLE & SKLAR PLL
1621 EUCLID AVENUE
NINETEENTH FLOOR
CLEVELAND
OH
44115
|
Family ID: |
23405200 |
Appl. No.: |
09/357341 |
Filed: |
July 14, 1999 |
Current U.S.
Class: |
303/20 ;
303/121 |
Current CPC
Class: |
B60T 8/885 20130101;
B60T 2270/414 20130101; B64C 25/42 20130101; B60T 8/1703
20130101 |
Class at
Publication: |
303/20 ;
303/121 |
International
Class: |
B60T 008/32 |
Claims
What is claimed is:
1. An electromechanical braking system, comprising: at least one
electromechanical brake actuator for effecting a braking torque on
a wheel of a vehicle; and a plurality of brake controllers for
providing drive control signals to the at least one
electromechanical brake actuator in response to an input brake
command signal to effect the braking torque, the plurality of brake
controllers being configured to function redundantly so as to
provide the drive control signals to effect the braking torque even
in the event one of the plurality of brake controllers becomes
inoperative.
2. The electromechanical braking system of claim 1, wherein each
brake controller comprises a brake control unit (BSCU) and at least
one electromechanical actuator controller (EMAC) in a common
housing, the BSCU converting the input brake command signal into a
brake clamp force command signal provided to the at least one EMAC,
and the at least one EMAC providing the drive control signals to
the at least one electromechanical brake actuator in response to
the brake clamp force command signal.
3. The electromechanical braking system of claim 1, wherein the
vehicle is an aircraft.
4. The electromechanical braking system of claim 1, wherein the
input brake command signal is proportional.
5. The electromechanical braking system of claim 1, wherein the
brake controllers each perform antiskid operations in relation to
the input brake command signal.
6. The electromechanical braking system of claim 1, wherein full
braking is available even in the event one of the plurality of
brake controllers becomes inoperative.
7. The electromechanical braking system of claim 1, wherein
substantially full braking torque is maintained by temporarily
overdriving individual actuator motors in the event one of the
plurality of brake controllers becomes inoperative.
8. The electromechanical braking system of claim 1, wherein the
system includes a plurality of electromechanical brake actuators
controlled by the plurality of brake controllers.
9. The electromechanical braking system of claim 8, wherein in the
event one of the brake controllers becomes inoperative, a maximum
brake torque applied by one of the electromechanical brake
actuators via another of the brake controllers is increased.
10. The electromechanical braking system of claim 1, wherein the
brake controllers are configured to operate on power received from
both an AC power buss and a DC power buss.
11. An electromechanical braking system, comprising: a plurality of
brake actuators for effecting a braking torque on wheels of a
vehicle; a plurality of electromechanical actuator controllers
(EMACs) for providing drive control of the brake actuators in
response to brake clamp force command signals; and at least one
brake control unit (BSCU) for converting an input brake command
signal into the brake clamp force command signals which are
provided to the EMACs, wherein at least two of the plurality of
EMACs are configured to function redundantly in providing drive
control to the brake actuators in response to the brake clamp force
command signals.
12. The system of claim 11, wherein in an event one of the
plurality of EMACs becomes inoperative braking torque still is
effected on the wheels of the vehicle by virtue of another of the
plurality of EMACs and the plurality of brake actuators.
13. The system of claim 12, wherein each of the plurality of EMACs
provide drive control to a same set of the brake actuators on a
given wheel of the vehicle.
14. The system of claim 12, wherein each of the plurality of EMACs
provide drive control to a corresponding different set of the brake
actuators on a given wheel of the vehicle.
15. The system of claim 14, wherein if one of the plurality of
EMACs becomes inoperative, a maximum brake torque applied by one of
the electromechanical brake actuators driven via another of the
EMACs is increased.
16. The system of claim 11, wherein the vehicle is an aircraft.
17. The system of claim 11, wherein the system includes a plurality
of BSCUs, and at least two of the BSCUs function redundantly in
providing brake clamp force command signals to the EMACs.
18. An electromechanical braking system, comprising: a plurality of
brake actuators for effecting a braking torque on wheels of a
vehicle; at least one electromechanical actuator controller (EMAC)
for providing drive control of the brake actuators in response to
brake command signals; and a plurality of brake control units
(BSCUs) for converting an input brake command signal into the brake
clamp force command signals which are provided to the at least one
EMAC, wherein at least two of the plurality of BSCUs are configured
to function redundantly in providing brake clamp force command
signals to the at least one EMAC in response to the input brake
command signal.
19. The system of claim 18, wherein each of the plurality of BSCUs
functions to provide antiskid control in relation to the input
brake command signal.
20. The system of claim 18, wherein the vehicle is an aircraft.
Description
TECHNICAL FIELD
[0001] The present invention relates generally to brake systems for
vehicles, and more particularly to an electromechanical braking
system for use in aircraft.
BACKGROUND OF THE INVENTION
[0002] Various types of braking systems are known. For example,
hydraulic, pneumatic and electromechanical braking systems have
been developed for different applications. In the past, however, it
has not been shown to employ reliably an electromechanical braking
system in a vehicle such as an aircraft.
[0003] An aircraft presents a unique set of operational and safety
issues. For example, uncommanded braking due to failure can be
catastrophic to an aircraft during takeoff. On the other hand, it
is similarly necessary to have virtually fail-proof braking
available when needed (e.g., during landing).
[0004] If one or more engines fail on an aircraft, it is quite
possible that there will be a complete or partial loss of
electrical power. In the case of an electromechanical braking
system, issues arise as to how the brakes will be actuated in an
emergency landing.
[0005] In view of such shortcomings associated with conventional
electromechanical braking systems, there is a strong need in the
art for an electromechanical braking system which may be employed
reliably even on a vehicle such as an aircraft.
SUMMARY OF THE INVENTION
[0006] An electromechanical braking system utilizes redundancy
features to provide safe and reliable braking. The braking system
is configured to operate on power provided by multiple power
sources. Different modes of braking are available based on whether
a failure has occurred in one or more power sources. Additionally,
system redundancy allows for failure in one or more primary
components without total loss of braking capacity. Proportional
braking is provided even in an emergency braking mode.
[0007] According to one aspect of the invention, an
electromechanical braking system is provided which includes at
least one electromechanical brake actuator for effecting a braking
torque on a wheel of a vehicle; and a plurality of brake
controllers for providing drive control signals to the at least one
electromechanical brake actuator in response to an input brake
command signal to effect the braking torque. The plurality of brake
controllers are configured to function redundantly so as to provide
the drive control signals to effect the braking torque even in the
event one of the plurality of brake controllers becomes
inoperative.
[0008] In accordance with another aspect of the invention, an
electromechanical braking system is provided which includes a
plurality of brake actuators for effecting a braking torque on
wheels of a vehicle; a plurality of electromechanical actuator
controllers (EMACs) for providing drive control of the brake
actuators in response to brake clamp force command signals; and at
least one brake control unit (BSCU) for converting an input brake
command signal into the brake clamp force command signals which are
provided to the EMACs. At least two of the plurality of EMACs are
configured to function redundantly in providing drive control to
the brake actuators in response to the brake command signals.
[0009] According to still another aspect of the invention, an
electromechanical braking system is provided which includes a
plurality of brake actuators for effecting a braking torque on
wheels of a vehicle; at least one electromechanical actuator
controller (EMAC) for providing drive control of the brake
actuators in response to brake clamp force command signals; and a
plurality of brake control units (BSCUs) for converting an input
brake command signal into the brake clamp force command signals
which are provided to the at least one EMAC. At least two of the
plurality of BSCUs are configured to function redundantly in
providing brake clamp force command signals to the at least one
EMAC in response to the input brake command signal.
[0010] To the accomplishment of the foregoing and related ends, the
invention, then, comprises the features hereinafter fully described
and particularly pointed out in the claims. The following
description and the annexed drawings set forth in detail certain
illustrative embodiments of the invention. These embodiments are
indicative, however, of but a few of the various ways in which the
principles of the invention may be employed. Other objects,
advantages and novel features of the invention will become apparent
from the following detailed description of the invention when
considered in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is an environmental view of an electromechanical
braking system in an aircraft in accordance with the present
invention;
[0012] FIG. 2 is a general block diagram of the electromechanical
braking system in accordance with the present invention;
[0013] FIG. 3 is a detailed block diagram of the electromechanical
braking system in accordance with the present invention;
[0014] FIG. 4A is a timing diagram illustrating operation of the
electromechanical braking system in a first alternate braking mode
in which a primary AC power source has failed;
[0015] FIG. 4B is a timing diagram illustrating operation of the
electromechanical braking system in a second alternate braking mode
in which an essential primary AC power source has failed;
[0016] FIG. 4C is a timing diagram illustrating operation of the
electromechanical braking system in an emergency braking mode in
which all primary power sources have failed;
[0017] FIG. 4D is a timing diagram illustrating operation of the
electromechanical braking system in a park (ultimate) braking mode
in which all primary power sources are unavailable;
[0018] FIG. 5A is a timing diagram illustrating operation of the
electromechanical braking system during failure of a brake system
control unit;
[0019] FIG. 5B is a timing diagram illustrating operation of the
electromechanical braking system during failure of an
electromechanical actuator controller;
[0020] FIG. 6 is a detailed block diagram of a particular
embodiment of an electromechanical braking system in accordance
with the present invention;
[0021] FIG. 7 is a detailed block diagram of a particular
embodiment of a brake system control unit in accordance with the
present invention;
[0022] FIG. 8 is a detailed block diagram of a particular
embodiment of an electromechanical actuator controller in
accordance with the present invention;
[0023] FIG. 9 is a detailed block diagram of an electromechanical
braking system in accordance with another embodiment of the present
invention;
[0024] FIG. 10 is a detailed block diagram of an electromechanical
braking system in accordance with a third embodiment of the present
invention; and
[0025] FIG. 11 is a detailed block diagram of an electromechanical
braking system in accordance with a fourth embodiment of the
present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] The present invention will now be described with reference
to the drawings, wherein like reference labels are used to refer to
like elements throughout.
[0027] Referring initially to FIG. 1, an electromechanical braking
system 30 in accordance with the present invention is shown within
a jet aircraft 32 (illustrated in phantom). As will be explained in
more detail below, the system 30 is designed as a brake-by-wire
system compatible with the performance, safety, electrical and
mechanical interfaces, redundancy, and other requirements of an
aircraft such as a commercial transport. The system 30 operates
based on power provided from a plurality of power sources. Power is
segregated within the system 30 such that the system 30 is capable
of providing satisfactory braking even upon failure of one or more
power sources. Moreover, the system 30 has built in redundancy
which allows the system 30 to continue to operate satisfactorily
even in the case of failure of one or more system components.
[0028] In the exemplary embodiment, the system primary components
include four electromechanical brakes 34. The aircraft 32 in the
present embodiment includes a pair of wheels 36 mounted to a
landing gear under the left wing of the aircraft and a pair of
wheels 36 mounted to a landing gear under the right wing of the
aircraft. Each wheel 36 includes a respective brake 34 for
providing braking action thereto.
[0029] The system 30 further includes two redundant digital brake
system control units (BSCUs) 40. As will be described in more
detail below, the BSCUs 40 carry out the brake control and antiskid
processing functions. The BSCUs 40 are located in the electronics
bay 42 of the aircraft 32, and preferably are packaged into one
enclosure with a firewall therebetween.
[0030] The system 30 also includes four redundant electromechanical
actuator controllers (EMACs) 44 which convert brake clamp force
commands from the BSCUs 40 to servo motor control signals which
ultimately provide actuator braking forces. The EMACs 44 preferably
are packaged similar to the BSCUs 40, with two EMACs 44 per
enclosure located near the top of the gear strut of each respective
landing gear.
[0031] A pilot of the aircraft 32 provides brake commands to the
braking system 30 via a pair of left and right brake pedal
transducers 46 included in the cockpit. The transducers 46 provide
brake command signals to the BSCUs 40 which are proportional to the
desired amount of braking. The output of each transducer 46 is
coupled to the BSCUs 40 via a cable 48. Communications between the
BSCUs 40 and the EMACs 44 occur over a communication bus 50
connected therebetween.
[0032] Each of the EMACs 44 is designed to provide electrical power
to the electromechanical actuators within the corresponding brakes
34 via a respective power cable 52. In addition, each brake 34 has
an associated torque sensor and wheel speed sensor as described
below. The outputs of the sensors are provided to the respective
EMACs 44 via cables 54. The EMACs 44 condition the signals and
provide them to the BSCUs 40 as feedback signals to carry out the
brake control and antiskid processing functions.
[0033] FIG. 2 is a simplified block diagram of the braking system
30 as employed within the aircraft 32. The BSCUs 40 and the EMACs
44 are shown collectively as an electromechanical braking
controller 60. The controller 60 receives as its primary inputs the
brake command signals from the transducers 46, and the outputs of
the torque and wheel speed sensors 62 included as part of the brake
34 on each wheel 36.
[0034] The braking system 30 receives power from three primary
power busses and a secondary power buss included within the
aircraft 32. As is known, an aircraft 32 oftentimes will include
multiple power busses. In the exemplary embodiment, the aircraft 32
includes primary power busses PWR1, PWR2 and PWRess. Each power
buss preferably is independent of one or more of the other power
busses to provide a level of redundancy. For example, the power
buss PWR1 consists of an alternating-current (AC) power source AC1
and a commonly generated direct-current (DC) power source DC1.
Similarly, the power buss PWR2 consists of an AC power source AC2
and a commonly generated DC power source DC2; and the power buss
PWRess consists of an AC power source ACess and commonly generated
DC power source DCess.
[0035] The power buss PWR1 (i.e., AC1 and DC1) may be derived from
power generated by the left wing engine in the aircraft 32, for
example. Similarly, the power buss PWR2 (i.e., AC2 and DC2) may be
derived from power generated by the right wing engine 34. In this
manner, if the left wing engine or the right wing engine fails,
power is still available to the system 30 via the power buss
corresponding to the other engine.
[0036] The power buss PWRess (i.e., ACess and DCess) may be derived
from power generated by the parallel combination of the left wing
engine and the right wing engine. In such manner, power from the
power buss PWRess will still be available even if one of the
engines fail.
[0037] The aircraft 32 further includes an emergency DC power buss
represented by a DChot power source. The DChot power source is a
battery supply on board the aircraft 32. The battery may be charged
via power from one of the other power sources, or may be charged
separately on the ground.
[0038] As will be appreciated, various circumstances can arise
where power from one or more of the power busses will become
unavailable. For example, the left wing engine or the right wing
engine could fail causing the PWR1 (AC1/DC1) and PWR2 (AC2/DC2)
power sources to go down, respectively. Alternatively, power
generating equipment such as a generator, inverter, or other form
of power converter could fail on one of the respective power busses
resulting in the AC1/DC1, AC2/DC2 and/or ACess/DCess power sources
becoming unavailable. In addition, a failure can occur in the
cabling providing the power from the respective power sources to
the system 30, thus effectively causing the respective power source
to no longer be available. For this reason, the routing of the
power cables for the different busses preferably occurs along
different routes throughout the plane to avoid catastrophic failure
on all the power buss cables at the same time.
[0039] Turning now to FIG. 3, the braking system 30 is illustrated
in more detail. As noted above, the system 30 includes two BSCUs 40
designated BSCU1 and BSCU2, respectively. BSCU1 and BSCU2 are
redundant and are both configured to provide an input/output
interface to the aircraft 32 electronics within the cockpit, for
example, via a bus 70. In addition, BSCU1 and BSCU2 each contain
circuitry for performing top level brake control and antiskid
algorithm processing functions. BSCU1 and BSCU2 each receive
proportional brake command signals from the transducers 46 via
cable 48.
[0040] BSCU1 and BSCU2 are each designed to receive the
proportional brake command signals from the transducers 46 and
process the signals based on the aforementioned brake control and
antiskid algorithms to produce a brake command signal which is
provided to the EMACs 44. The particular brake control and antiskid
algorithms employed by the BSCUs 40 can be conventional, and hence
further detail based thereon is largely omitted in the present
description for sake of brevity. BSCU1 and BSCU2 each provide brake
commands and otherwise communicate with the EMACs 44 via the
aforementioned communication bus As noted above, the system 30
includes four redundant EMACs 44 respectively labeled EMAC Left1,
EMAC Left2, EMAC Right1 and EMAC Right2. As shown in FIG. 3, each
EMAC 44 is coupled to the communication bus 50 so as to be able to
receive brake commands from each of the BSCUs 40 and otherwise
communicate with the other devices coupled to the bus 50. The EMACs
44 receive the left and right brake commands from the BSCUs 40 and
provide control signals to actuator modules within the brakes 34 as
discussed below to drive the actuator modules to their commanded
position or clamp force. In this manner, controlled braking may be
effected.
[0041] Each brake 34 included in the system 30 includes four
separate actuator modules (designated by numerals 1-4), although a
different number may be employed without departing from the scope
of the invention. Each actuator module 1-4 includes an electric
motor and actuator (not shown) which is driven in response to
electrical control signals provided by a respective EMAC 44 to
exert mechanical braking torque on a respective wheel 36. Each EMAC
44 controls half of the actuator modules 1-4 for the wheels 36 on
either the left wing landing gear or the right wing landing gear.
Thus, EMAC Left1 provides control to actuator modules 1 and 3 of
each of the wheels 36 in the left side landing gear (representing
the left brakes) via cable 52. Similarly, EMAC Left2 has its output
coupled to the remaining actuator modules 2 and 4 of the wheels 36
in the left side landing gear via cable 52. EMAC Right1 similarly
provides power to the actuator modules 1 and 3 for the wheels 36 in
the right side landing gear (representing the right brakes), and
EMAC Right2 provides power to the remaining actuator modules 2 and
4 in the right side landing gear via another cable 52.
[0042] Thus, when the system 30 is fully operational (i.e., during
normal operation) each of the EMACs 44 receives brake commands from
BSCU1 and BSCU2 which will be generally redundant. Nevertheless,
the EMACs 44 may be configured to give commands provided by BSCU1
priority or vice versa. In the event commands are not received from
one of the BSCUs 40, the EMACs 44 are configured to default to the
other BSCU 40. During normal operation, all four actuator modules
1-4 will receive brake control signals from their respective EMAC
44 to provide full braking.
[0043] Although not shown in FIG. 3, the outputs of the wheel speed
and torque sensors 62 (if used) for each brake 34 are coupled to
the respective EMACs 44 via the cables 54 (FIG. 2). The EMACs 44
are configured to condition the signals and provide the measured
wheel speed and torque to the BSCUs 40 via the communication bus
50. The BSCUs 40 in turn use such information in a conventional
manner for carrying out brake control and antiskid processing.
[0044] As is shown in FIG. 3, EMAC Left2 and EMAC Right2 differ
from the remaining EMACs in that they also receive left and right
proportional brake commands directly from the transducers 46 via a
separate cable 72 (not shown in FIG. 1). As is discussed in more
detail below, such direct input of the brake commands from the
transducers 46 is used during emergency braking operations. Also,
EMAC Left2 and EMAC Right2 receive a parking brake control signal
from a switch located in the cockpit via the cable 72 for carrying
out a parking brake operation as described below.
[0045] Continuing to refer to FIG. 3, both BSCU1 and BSCU2 are
designed to operate on DC power. However, BSCU1 is coupled to the
DC1 power source and BSCU2 is coupled to a different power source,
namely the DC2 power source. Thus, different power busses (e.g.,
PWR1 and PWR2) are used to supply operating power to the respective
BSCUs 40. Similarly, EMAC Left1 and EMAC Right1 are designed to
operate on power from the different power busses PWR1 and PWR2,
respectively. Specifically, EMAC Left1 receives AC operating power
from the AC1 source and DC operating power from the DC1 source.
EMAC Right1 receives AC operating power from the AC2 source and DC
operating power from the DC2 source.
[0046] EMAC Left2 and EMAC Right2 are configured to operate on
power from the PWRess power buss. Specifically, both EMAC Left2 and
EMAC Right2 receive AC operating power from the ACess source and DC
operating power from the DCess source. In addition, EMAC Left2 and
EMAC Right2 are designed to operate in an emergency mode based on
power provided by the DChot bus as discussed below.
[0047] The system 30 is designed to carry out built-in testing
among the EMACs 44 to detect the loss of power from any of the
primary power busses PWR1, PWR2 and PWRess. Such built-in testing
can be carried out by configuring the EMACs 44 to poll each other
via the communication bus 50, for example. If an EMAC 44 fails to
respond to polling by another, for example, it can be assumed that
power from the particular power buss servicing the EMAC 44 is
unavailable or that the EMAC 44 itself has failed. The polling
EMACs 44 then communicate such information to the BSCUs 40 via the
bus 50. The BSCUs 40 in turn command the functioning EMACs 44 to
revert to an alternate mode of braking. Other techniques for
detecting the loss of power on one of the power busses or the
failure of one of the components can be used without departing from
the scope of the invention as will be appreciated.
[0048] For example, the BSCUs 40 may instead be configured to poll
each EMAC 44 via the communication bus 50. If an EMAC 44 fails to
respond, the BSCU(s) 40 recognize the problem EMAC 44 and in turn
command the functioning EMACs 44 to revert to an alternate mode of
braking.
[0049] Braking Modes
[0050] The braking system 30 includes five primary operating modes
for purposes of the present invention, including a normal mode,
alternate mode 1, alternate mode 2, emergency mode and park
(ultimate) mode. In each mode braking is available despite failure
of a power buss, etc., as will now be explained with reference to
FIGS. 4A-4D and 5A-5B.
[0051] FIGS. 4A-4D and 5A-5B illustrate the state of respective
power busses and components within the system 30 with respect to
time during different failure modes. A line level "A" in the
figures indicates that the power buss or component is available and
operational. A line level "IN" indicates that the power buss or
component is inactive or unavailable. With respect to a line level
between "A" and "IN", this indicates that the brakes or components
are partially available or operational as will be further described
below.
[0052] Normal Mode
[0053] Normal mode operation is defined as operation during which
power from all the primary power busses PWR1, PWR2 and PWRess is
available, and the BSCUs 40 and EMACs 44 are functional. Referring
initially to FIG. 4A, normal mode operation is shown at a time
prior to a failure time tf. As is shown, all of the power busses
are available, the BSCUs 40 and EMACs 44 are receiving power and
are operational. Moreover, each of the actuator modules 1-4 in the
left brakes and right brakes are powered and operational.
[0054] Alternate Mode 1
[0055] Alternate mode 1 is defined as operation during which the
power buss PWR1 or PWR2 is unavailable due to failure, for example,
but the power buss PWRess remains available.
[0056] FIG. 4A illustrates a particular example where, at a failure
time tf, the power buss PWR1 (AC1/DC1) fails. As noted above, such
failure may occur due to engine failure, power converter failure,
broken power cable, etc. Since BSCU1 is powered by the power buss
PWR1, BSCU1 will stop functioning at time tf as represented in FIG.
4A. However, since BSCU1 and BSCU2 are redundant and BSCU2 still
receives operating power from the power buss PWR2 (AC2/DC2), brake
control operation and antiskid processing may still be carried
out.
[0057] Since EMAC Left1 receives power from the power buss PWR1, it
also becomes unavailable at time tf. Because EMAC Left1 becomes
unavailable, the actuator modules 1 and 3 controlled by the EMAC in
the left brakes are disabled. Nevertheless, each of the remaining
EMACs 44 remain operational. Accordingly, two of the four actuator
modules (i.e., 2 and 4) remain available for braking as controlled
by the EMAC Left2. Ordinarily this would result in a loss of 50% of
the total available braking force on the left wheels 36. However,
the EMACs 44 are designed to increase the upper force limit exerted
by the respective actuator modules 1-4 in the alternate mode.
[0058] For example, the limit for the maximum braking force applied
by each of the remaining two actuators 2 and 4 is increased by the
EMAC Left2 by 60%. Hence, the total braking force for the left
brakes can achieve 80% of the normal braking capability. In another
example, the maximum braking force limit can be adjusted by some
other amount.
[0059] The aforementioned built-in testing detects the loss of the
power buss PWR1. This results in the BSCU2 informing the EMAC Left2
to increase the braking force limit. Even absent such compensation,
50% braking is still available. Thus, as is shown in FIG. 4A,
partial braking for the left brakes is available even after time
tf.
[0060] Similar operation to that shown in FIG. 4A would occur if
the power buss PWR2 (AC2/DC2) failed rather than the power buss
PWR1. In such case, however, BSCU1 would remain operational and
BSCU2 would fail. Similarly, EMAC Right 1 would fail and the
remaining EMACs 44 would continue to operate. The actuator modules
1 and 3 in the right brakes would be disabled, but the EMAC Right2
would increase the maximum force limit of the actuator modules 2
and 4, similar to that previously described.
[0061] Alternate Mode 2
[0062] Alternate mode 2 is defined as operation during which the
power buss PWRess is unavailable due to failure, for example, but
the power busses PWR1 and PWR2 remain available.
[0063] For example, FIG. 4B illustrates how the power buss PWRess
fails at time tf while power busses PWR1 and PWR2 remain active. In
such case, EMAC Left2 and EMAC Right2 are considered unavailable by
the system 30 as shown. Although EMAC Left2 and EMAC Right2 receive
power from the DChot bus, such power is utilized only in the
emergency mode discussed below.
[0064] Since EMAC Left2 and EMAC Right2 are not operational, the
actuator modules 2 and 4 for each of the brakes 34 for the left and
right wheels 36 are disabled. In this case, only 50% of the
actuator modules 1-4 are active for each of the brakes 34.
Nevertheless, failure of the PWRess is detected and the BSCUs 40
instruct the remaining EMAC Left1 and EMAC Right1 to increase the
force limits of the active actuator modules 1 and 3 so as to
provide a higher percentage of the normal braking force. Again,
this reduced braking function in the left and right brakes is
reflected in FIG. 4B.
[0065] Emergency Mode
[0066] The emergency mode is defined as failure of all the primary
power sources PWR1, PWR2 and PWRess. Only the DChot power source
remains available.
[0067] FIG. 4C illustrates the emergency mode where all the primary
power sources PWR1, PWR2 and PWRess fail at or before time tf. In
such case, both BSCUs 40 become disabled as does EMAC Left1 and
EMAC Right1. Only EMAC Left2 and EMAC Right2 remain active on a
limited basis by virtue of the DChot power source. EMAC Left2 and
EMAC Right2 are configured to recognize such condition and are
designed to operate under condition on the brake commands provided
directed thereto from the transducers 46 via cable 72.
[0068] Under such condition, only actuator modules 2 and 4 remain
active in each brake 34. EMAC Left2 and EMAC Right2 are designed to
use the pedal input commands received directly from the transducers
46 to achieve proportional brake force application using the
actuator modules 2 and 4 in each brake 34. Such pedal input
commands may derive power from the DChot source via the connecting
cables 72 and 48, and the system 30 preferably is designed to
provide the most direct electrical path between the transducers 46
and the brakes 34 to minimize the number of intermediate
components, and hence decrease the possibility of component failure
in that path.
[0069] Since only actuator modules 2 and 4 remain active in each
brake, it is preferable that EMAC Left2 and EMAC Right2 be
configured to control the upper force limit of each actuator module
under such condition in order to optimize braking while avoiding
wheel lock-up since antiskid protection is not available. In
addition to controlling the upper force limit, or in the
alternative, the EMACs 44 may be configured to operate the actuator
modules in a pulse mode to avoid wheel lock-up. It is noted that in
the emergency mode, both BSCUs 40 are disabled, and hence antiskid
protection is not available.
[0070] Park (Ultimate) Mode
[0071] In the park (ultimate) mode, only power from the DChot
source is available as represented in FIG. 4D. This may be because
the aircraft 32 is on the ground with the remaining power systems
shut down. Alternatively, all the primary power busses PWR1, PWR2
and PWRess may have failed similar to the emergency mode discussed
above.
[0072] For the same reasons discussed above in relation to FIG. 4C
and the emergency mode, only EMAC Left2 and EMAC Right2 remain
active in the park (ultimate) mode. Moreover, these particular
EMACs are only partially active in the sense that they are
operating based on power from the DChot source. Operation differs
from the emergency mode in the following respects.
[0073] As mentioned above, the cockpit includes a parking brake
switch selectively activated by the pilot. The parking brake switch
is coupled to EMAC Left2 and EMAC Right2 via the cables 48 and 72,
for example. EMAC Left2 and EMAC Right2 are both configured to
provide a predetermined fixed braking force via the enabled
actuator modules 2 and 4 in each of the brakes 34 upon closing of
the parking brake switch. Power from the DChot source is used only
to actuate the actuator modules 2 and 4 into position. Thereafter,
a mechanical holding device within the actuator module holds the
actuator mechanism in place so as to no longer require power from
the DChot source. In this manner, the park mode uses power only
during activation or when the park brake is released in order to
conserve power in the aircraft battery.
[0074] Release of the parking brake is implemented by removing the
brake clamping force as a result of the EMAC Left2 and EMAC Right2
disabling the mechanical holding device and driving each actuator
module 2 and 4 to a running clearance position. Specifically, the
parking brake switch in the cockpit being moved to a release
position causes the EMAC Left2 and EMAC Right2 to release the
parking brake.
[0075] The park (ultimate) mode is considered to be a final means
of applying brakes in an aircraft emergency situation in order to
stop the aircraft. The EMACs are configured preferably such that
the park mode overrides any normal braking commands unless the
normal braking command torque level is higher than the park torque
level. If the remainder of the system 30 fails due to the BSCUs 40
or the main power busses PWR1, PWR2 and PWRess failing, for
example, it is noted that operation of the park (ultimate) mode is
neither prevented nor delayed.
[0076] Referring now to FIG. 5A, a case where one of the BSCUs 40
fails is illustrated. For example, FIG. 5A shows how BSCU1 may fail
at time tf due to component failure. Since BSCU1 and BSCU2 are
redundant, the EMACs 44 will continue to receive brake commands
from BSCU2. Hence, the system 30 will continue to operate in a
normal mode. Although not shown, if BSCU2 were also to fail for
some reason (e.g., component failure), the EMACs 44 are configured
to revert to emergency mode operation. More specifically, in the
absence of commands from the BSCUs 40, EMAC Left2 and EMAC Right2
are configured to operate proportionally in the emergency mode
based on the direct inputs from the brake pedal transducers 46 as
described above.
[0077] FIG. 5B illustrates how if EMAC Right1 fails at time tf1 due
to component failure, for example, the remaining EMACs 44 continue
to operate such that the right brakes continue to provide at least
partial braking. If EMAC Left1 were to then fail at time tf2, for
example, partial braking would again still be available in the left
brakes. Thus, the present invention provides protection against
component failure much in the same way as protection against
failure of the power systems.
[0078] FIG. 6 illustrates in detail the particular configuration of
the braking system 30 in accordance with one example of the present
invention. FIG. 7 represents an exemplary architecture for the
BSCUs 40. However, it will be appreciated that each BSCU 40 can
have a variety of configurations yet still satisfy the objects of
the invention. FIG. 8 represents an exemplary design of an EMAC 44
and actuator 34 for carrying out the above described functions.
Again, however, the particular design illustrated in FIG. 8 is not
intended to limit the scope of the invention. For example, the
actuator 34 may utilize force sensors in place of position
sensors.
[0079] Turning now to FIGS. 9-11, alternative embodiments of the
present invention will now be discussed. Referring initially to
FIG. 9, an electromechanical braking system which incorporates
redundant centralized controllers with power drive circuits is
designated 80. In the exemplary embodiment, the system 80 includes
two identical centralized controllers 82a and 82b. Each controller
82a and 82b includes a BSCU controller as discussed above, combined
with power drive circuits (EMACs) for each brake actuator to be
driven by the BSCU controller. Thus, in the embodiment of FIG. 9
the BSCU 40 and EMACs 44 are combined into a centralized controller
82.
[0080] As shown in FIG. 9, the controllers 82a and 82b are
redundant in that each receives brake commands from the transducers
46 via cable 48. The output of each controller 82a and 82b is
coupled to the brake actuator modules 1 and 2 for each wheel 36 in
both the left wheel brakes and the right wheel brakes. The outputs
from the torque and wheel speed sensors 62 for each of the wheels
36 is coupled to both controllers 82a and 82b.
[0081] Each controller 82a and 82b processes the brake commands
received via cable 48 and outputs brake actuator drive signals to
the actuator modules 1 and 2 for each wheel, thus providing a
fundamental form of redundancy. If the BSCU in one of the
controllers (e.g., 82a) was to fail, the BSCU in the other
controller (e.g., 82b) would still function to provide full braking
capabilities. If a given EMAC within one of the controllers 82 was
to fail, the corresponding EMAC in the other controller would still
be available to provide the necessary drive signals to the
respective brake actuator module.
[0082] The controllers 82a and 82b preferably are contained in
their own respective enclosures within the aircraft. Power is
provided to the respective controllers 82a and 82b via different
power busses as in the previous embodiment, or via the same power
buss. The advantage of providing power via different power busses
is that if one power buss was to fail, the controller 82 driven by
the other power buss would remain active.
[0083] FIG. 10 shows an electromechanical braking system 84 which
utilizes redundant BSCUs 40 as in the embodiment of FIG. 3. In
addition, the left brakes and the right brakes each include
redundant EMACs 44. In this embodiment, however, the EMACs 44 are
located within the landing gear adjacent the actuators 34.
Moreover, power is provided from a centralized power converter
located withing the root of the wing of the aircraft.
[0084] More particularly, redundant BSCUs 1 and 2 receive brake
command signals from the transducers 46 via cable 48 as in the
previous embodiments. The BSCUs 1 and 2 provide brake control
signals to each of a plurality of redundant EMACs 44 included for
each of the left wheel brakes and the right wheel brakes. In the
exemplary embodiment, the left wheel brakes are controlled by two
EMACs, namely EMAC1 and EMAC2. The right wheel brakes are
controlled by two EMACs, namely EMAC3 and EMAC4. EMAC1 and EMAC2
each receive brake control signals from both BSCUs 1 and 2, and
provide redundant drive signals to each of actuators 1 and 2 for
both left wheels 36. Similarly, EMAC3 and EMAC4 each receive brake
control signals from both BSCUs, and provide redundant drive
signals to each of actuators 1 and 2 in both right wheels 36.
[0085] If one of the BSCUs (e.g., BSCU1) was to fail in the
embodiment of FIG. 10, full brake control would still be available
by virtue of the other BSCU (e.g., BSCU2). If one of the EMACs
(e.g., EMAC3) was to fail, the other EMAC (e.g., EMAC4) would still
be available to provide the appropriate drive signals to the
actuators.
[0086] Power is provided to the BSCUs via different power busses as
in the embodiment of FIG. 3, or the same power buss as discussed
above. In the exemplary embodiment, power is provided to the EMACs
via a power converter 88 located in the wing root of the aircraft.
The converter 88 receives AC and DC power from one or more power
busses and converts the power into a operating line voltage Vemac
which is delivered to EMACs 1 thru 4. Preferably, the converter 88
is designed to receive power from two or more different power
busses in order to provide redundancy in the event one of the power
busses was to fail.
[0087] FIG. 11 illustrates another embodiment of an
electromechanical braking system which is designated 90. Similar to
the embodiment of FIG. 10, the system 90 includes redundant BSCUs 1
and 2 for processing brake commands received from the pedal
transducers via cable 48. The EMACs 44 are again located in the
landing gear adjacent the brake actuator modules which, in this
example, consist of three actuator modules 1-3 per wheel 36. EMAC1
receives brake control signals from both BSCU1 and BSCU2, and in
turn drives actuators 1 thru 3 for the left wheels. EMAC2 also
receives brake control signals from both BSCU1 and BSCU2, and
instead drives actuators 1 thru 3 in connection with the right
wheels. In this example, the EMACs are located at the bottom of the
landing gear, closer to the respective actuator modules 1-3. This
allows the length of the power cables between the EMACs and the
actuator modules to be minimized.
[0088] The various embodiments described herein provide for
different levels of redundancy in the event of equipment failure,
power failure, or both. In many instances a particular number of
redundant BSCUs, EMACs, etc. are described. However, it will be
appreciated that different numbers of redundancy in BSCUs, EMACs,
etc., are possible depending upon the number of wheels, brakes,
actuators, etc. The present invention is intended to include any
and all such possible numbers.
[0089] Although the invention has been shown and described with
respect to certain preferred embodiments, it is obvious that
equivalents and modifications will occur to others skilled in the
art upon the reading and understanding of the specification. For
example, although the present invention has clear utility in
connection with an aircraft, the braking system described herein
can also be used on other type vehicles without departing from the
scope of the invention. The present invention includes all such
equivalents and modifications.
* * * * *