Patent Publication Number: US-8527180-B2

Title: Systems and methods for controlling aircraft electrical power

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a divisional of and claims priority to U.S. patent application Ser. No. 11/518,379 filed on Sep. 7, 2006. 
     The above stated application is hereby incorporated herein by reference in its entirety. 
    
    
     FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     [Not Applicable] 
     FIELD 
     The present disclosure is directed generally to systems and methods for controlling aircraft electrical power, including controlling the operation of motor controllers in a manner that depends upon the operational mode of the aircraft, and/or substituting one motor controller for another. 
     BACKGROUND 
     Aircraft manufacturers are under continual pressure to reduce the power required by commercial transport aircraft, and to improve the efficiency with which such aircraft are operated. One approach for achieving these goals has been to replace devices that historically have been driven by bleed air or shaft output from the aircraft engines, with devices that are electrically driven. For example, hydraulic pumps on newer generation aircraft are now driven by electric motors. Hydraulic pumps pressurize hydraulic fluid which is in turn used to power many aircraft systems, including landing gear, high lift devices (e.g., leading edge devices and trailing edge devices), ailerons, elevators, rudders, and/or other devices that are important for aircraft operation. Electrically-driven hydraulic pumps are expected to provide an improved measure of efficiency, flexibility, and/or reliability. 
     As a result of the migration to electrically-driven hydraulic pumps, the need for large electric pumps and associated electric motors and motor controllers has increased. Because the hydraulic pumps are sized to operate at conditions that the aircraft rarely encounters during normal flight, the pumps are generally operated below maximum output levels. The output of the pumps can be reduced by decreasing the speed of the pump during most flight conditions, and increasing the pump speed as demand for hydraulic pressure increases. 
     One drawback with the foregoing approach is that the electrically-driven pumps tend to cycle repeatedly between high and low output settings as the demand for hydraulic fluid pressure fluctuates. This can create a whining noise. Because the hydraulic pumps may be located directly beneath the passenger cabin, the whining noise can be audible and annoying to the passengers. Accordingly, there is a need to reduce the level of noise experienced by the passengers, while operating the hydraulic pumps in an efficient manner. 
     SUMMARY 
     The following summary is provided for the benefit of the reader only, and is not intended to limit in any way the invention as set forth by the claims. Aspects of the present disclosure are directed to systems and methods for controlling aircraft electrical power. An aircraft power system in accordance with one aspect includes an electric motor, an aircraft load (e.g., a hydraulic pump) coupled to the electric motor and powered by the electric motor, and a motor controller coupled to the electric motor to vary the output of the electric motor. The motor controller can be changeable among a fixed number of preset controller modes, with individual controller modes corresponding to an operation mode of the aircraft and to a non-zero output level of the electric motor. 
     The fixed number of preset controller modes can reduce the tendency for frequent fluctuations in the power put out by the electric motor. 
     In particular aspects, the motor controller can be changeable among five controller modes. A first controller mode can correspond to ground operations, a second controller mode can correspond to cruise operations, and a third controller mode can correspond to takeoff and descent operations. A fourth controller mode can correspond to thrust reverser operations, and a fifth controller mode can correspond to automatic flap gapping operations. 
     An aircraft power generation system in accordance with another aspect includes a first electric motor, a first device (including an on-board aircraft hydraulic pump) coupled to and powered by the first electric motor, and a first motor controller coupled to the first electric motor to direct its operation. The system can further include a second electric motor, a second device coupled to and powered by the second electric motor, and a second motor controller coupled to the second electric motor to direct its operation. A switching device can be coupled between the first and second motor controllers to decouple the first motor controller from the first motor, decouple the second motor controller from the second motor, and couple the second motor controller to the first motor in place of the first motor controller. Accordingly, the second motor controller can substitute for the first and can provide for system redundancy. 
     Certain aspects are also directed to methods for controlling an aircraft system. One method includes receiving an indication of an operation mode of the aircraft, automatically selecting a generally constant output level from among a fixed number of multiple, preset output levels, based at least in part on the operation mode, and directing an electric motor to produce the selected output level. In particular aspects, the electric motor can be directed to operate at a fixed speed as a load on the motor changes. In still a further particular aspect, the electric motor is coupled to a hydraulic pump and the method further comprises driving the pump while an audible noise output of the pump is at an approximately constant level, with the electric motor producing the selected output level. In still further particular aspects, the electric motor can be coupled to a hydraulic pump, and the indication of the operation mode of the aircraft can correspond to a change in deployment of a high lift device, a change in a setting of an engine throttle, an altitude indication, and/or an indication from a weight-on-wheels indicator that the aircraft has landed. 
     A method in accordance with still another aspect includes receiving an indication corresponding to an expected increase in load on an aircraft electric motor from a current load level to a subsequent load level. The method can further include automatically changing an output of the electric motor in response to the indication and prior to the load level changing from the current load level to the subsequent load level. For example, the output of the electric motor can change in response to an indication that a throttle setting of the aircraft is advanced to at least 90% of maximum thrust. In another aspect, the output of the electric motor can change in response to an indication of a change in a high lift device setting (e.g., a change to or from a deployed setting or a stowed setting). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic top plan view of an aircraft having power systems configured in accordance with an embodiment of the invention. 
         FIG. 2  is a flow diagram illustrating a process in accordance with an embodiment of the invention for changing an output level of an electric motor in response to a change in an operation mode of the aircraft. 
         FIG. 3  is a schematic illustration of changes in motor output level as a function of changes in aircraft operation modes. 
         FIG. 4  is a flow diagram illustrating a method for substituting one motor controller for another in accordance with an embodiment of the invention. 
         FIG. 5  is a schematic illustration of an arrangement for substituting one aircraft motor controller for another in accordance with another embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure describes systems and methods for controlling aircraft electrical power. Certain specific details are set forth in the following description and in  FIGS. 1-5  to provide a thorough understanding of various embodiments of the invention. Well-known structures, systems, and methods often associated with such systems have not been shown or described in detail to avoid unnecessarily obscuring the description of the various embodiments of the invention. In addition, those of ordinary skill in the relevant art will understand that additional embodiments of the invention may be practiced without several of the details described below. 
     Several embodiments of the invention described below may take the form of computer-executable instructions, including routines executed by a programmable computer. Those skilled in the relevant art will appreciate that the invention can be practiced on computer or analog systems other than those shown and described below. The invention can be embodied in a special-purpose computer or data processor that is specifically programmed, configured or constructed to perform one or more of the computer-executable instructions described below. Accordingly, the term “computer” as generally used herein refers to any suitable data processor, including processors used for existing aircraft, programmed to carry out some or all of the instructions described below. 
       FIG. 1  is a schematic illustration of an aircraft  100  carrying one or more power systems  110  configured in accordance with an embodiment of the invention. The aircraft  100  includes a fuselage  101 , wings  102 , and one or more engines  103  that provide power to propel the aircraft  100  and drive various aircraft subsystems or loads  120 . These subsystems can include high lift devices  121  (e.g., leading edge devices  122  and/or trailing edge devices  123 ) located on the wings  102  of the aircraft, and landing gear  127  carried by the wings  102  and/or the fuselage  101 . These devices can be hydraulically powered by one or more hydraulic pumps  124  (four are shown in  FIG. 1  as hydraulic pumps  124   a - 124   d ). Each hydraulic pump  124  can be driven by a corresponding electric motor  111  (four are shown as electric motors  111   a - 111   d ), and each motor  111  can be controlled by a corresponding motor controller  113  (four are shown as motor controllers  113   a - 113   d ). 
     The aircraft  100  also carries other electrically-driven devices, for example, an environmental control system (ECS) compressor  125  that provides pressurized air to the passenger, crew, and baggage compartments. Additional electrically-driven devices can include a nitrogen generation system  126  that extracts nitrogen from the ambient air and provides it to fuel tanks  104  to create an inert environment in which the likelihood for a fuel explosion is significantly decreased. Each of these devices can include a motor and an associated motor controller  113  (shown as motor controllers  113   e  and  113   f , respectively). As is described in greater detail below with reference to  FIGS. 2-3 , the motor controllers  113  can be configured to operate at a fixed number of preset controller modes to reduce the frequency with which the motor speed or other output parameter changes during the course of a typical aircraft flight. As is discussed in greater detail below with reference to  FIGS. 4 and 5 , the motor controllers can be configured to substitute for each other, for example, to provide a level of redundancy for the functions carried out by the devices driven by the corresponding motors. 
       FIG. 2  is a flow diagram illustrating a representative process  200  for operating an aircraft power system in accordance with an embodiment of the invention. The process  200  includes starting the aircraft engine(s) (process portion  201 ), and establishing an initial output level for an electric motor coupled to the engine or engines (process portion  202 ). The initial output level can correspond to a motor speed, power level, torque, or any other suitable measure. The output of the motor can be controlled by controlling a suitable input, e.g., input current and/or voltage level, signal frequency and/or other inputs. Process portion  203  includes receiving an indication of a change in an operation mode of the aircraft. A representative list of indications is shown at block  206 . For example, one indication can include a change in engine throttle setting. Another indication can include a change in the setting of a high lift device (e.g., deploying the device or stowing the device). Still another indication can include an indication that the aircraft has landed, for example, a signal transmitted by a weight-on-wheels sensor. In other embodiments, the indication can include other parameters, for example, a gear up indication or an altitude indication. 
     In an optional process portion  204 , the process  200  includes determining whether a change in the operation mode warrants a change in motor output level. For example, not every change in an operation mode need necessarily result in a change in motor output level. In a particular example, the change in motor output level is warranted if the change in operation mode is expected to produce either an upward or a downward change in the demand placed on the motor, assuming the change meets or exceeds a threshold level. If the change is warranted, the output level of the motor is changed in process portion  205 . If not, the process  200  returns to process portion  203  to await an indication of a change in operation mode. The foregoing process steps can be repeated until the engine is shut down. 
       FIG. 3  is a schematic illustration of an operating profile  130  for an aircraft during a typical flight. The operation of the aircraft includes a variety of operation modes, a representative number of which are indicated along the horizontal axis at the top of  FIG. 3 . These modes can include a ground mode, followed by a takeoff and climb mode, a cruise mode, and an approach and land mode, followed by another ground mode. Though not representative of a typical flight, a high performance mode is also shown in  FIG. 3  for purposes of illustration. In other embodiments, the system can include other modes, for example, additional ground modes or sub-modes for testing and/or maintenance. 
     A motor controller mode line  132  is also shown in  FIG. 3 . In this representative example, the motor controller mode for one or more motors that provide hydraulic power to the aircraft is selected from among five different modes, represented by numerals I-V. Each motor controller mode corresponds to an aircraft operation mode and to a motor output level, with mode I corresponding to the lowest of the selected five output levels, and mode V corresponding to the highest. Further details of the controller modes and manners in which the modes are changed are described below. 
       FIG. 3  also illustrates motor activation lines, including hydraulic motor activation lines  131 ,  133 , and non-hydraulic motor activation lines  134  and  135 . An outboard hydraulic motor activation line  131  corresponds to the operation of the first and second (e.g., left and right) motors  111   a ,  111   b  shown in  FIG. 1 . A center hydraulic motor activation line  133  illustrates the operation of the third and fourth centrally located motors  111   c ,  111   d  shown in  FIG. 1 . The non-hydraulic motor activation lines  134 ,  135  illustrate the operation of the ECS compressor  125  ( FIG. 1 ) and the nitrogen generation system  126  ( FIG. 1 ), respectively. 
     The operations of the motors and associated motor controllers during a representative flight are now described with reference to  FIG. 3 . As shown by the operating profile  130 , ground operations typically begin with the start of the aircraft auxiliary power unit (indicated by tick mark A on the operation profile  130 ), followed by activation of the ECS compressor (tick mark B) and then by the start of the aircraft main engines (tick mark C). At tick mark D, the electric motor driven hydraulic pumps are started, corresponding to a motor output level I, as indicated by the motor output level line  132 . The motor output can remain at level I during taxi maneuvers and engine run-up in preparation for takeoff (tick mark E). 
     Initiating engine run-up can provide a trigger for changing the output of the electric motor driving the hydraulic pump from level I to another level, for example, level III, as shown in  FIG. 3 . The trigger can be identified by a change in the aircraft throttle setting, for example, when the aircraft throttle setting exceeds 90% of maximum thrust. In other embodiments, other triggers can be used to identify a change in the operation mode and trigger a corresponding change in the controller mode and motor output level. 
     One feature of an embodiment of the triggering event, for example, the engine run-up triggering event described above, is that it triggers an increase in motor output prior to an increase in the load on the motor that would require such an increase in output. For example, increasing the throttle setting on the engine, by itself, may not require additional output by the hydraulic motor pumps, but the subsequent loads placed on the aircraft as it leaves the ground typically will. Accordingly, in one aspect of the invention, the motor controller changes modes automatically in response to a trigger, prior to a change in demand on the device that is driven by the electric motor. 
     The motor controller mode can remain at mode III during takeoff (tick mark F), and gear retraction (tick mark G). If a high performance event occurs (e.g., if the aircraft approaches stall and requires an automatic flap gapping operation), then the motor mode can shift to mode V, as indicated at tick mark H, and the associated motor output can increase accordingly. This is typically a short duration segment, after which the motor controller mode returns to mode III. Because the high performance requirement is typically not predicted, in this instance, the change from one controller mode to another may not precede or anticipate a change in load on the motor, as was the case for the take-off operation described above. 
     At tick mark I, the flaps, slats and/or other high lift devices are fully retracted, indicating a gradual transition to cruise conditions. The retraction of the high lift devices can trigger a change in controller mode to mode II, which can remain in effect throughout the cruise mode and during the initial descent. At tick mark J, the high lift devices are deployed, and the controller mode returns to mode III. The gear can be deployed at tick mark K, without an effect on the controller mode. At tick mark L, the aircraft touches down, and this can provide an automatic trigger for the controller mode to change to mode IV, in anticipation of the thrust reversers being deployed (tick mark M). The change in controller mode can be automatically triggered by a signal received from a weight-on-wheels sensor, or other signal corresponding to aircraft touchdown. The touchdown itself is not expected to create an increased demand on the hydraulic pump motor, but instead precedes the expected deployment of the thrust reversers. At tick mark N, the thrust reversers are stowed, and the controller mode returns to mode I for the remainder of ground operations until the engine is shut down (tick mark O). 
     One feature of embodiments described above with reference to  FIGS. 1-3  is that the motor controller and the motor which it directs change among several preset modes. Each mode is selected to correspond to a motor output that provides sufficient power for the associated aircraft operation mode, and can include a margin for load fluctuations. As shown in  FIG. 3 , changes in motor and motor controller mode correspond to changes in aircraft operation mode and are limited during a typical flight. In a representative example shown in  FIG. 3 , the hydraulic motors change mode six times during the course of a normal flight, eight times if a high performance mode is required. This is unlike some existing motor arrangements, in which the motor and associated hydraulic pump can cycle repeatedly back and forth between output levels. Alternatively, other existing arrangements include operating the hydraulic pump continuously at a high output level, which can waste energy. An advantage of embodiments of the arrangement described above is that reducing the number of instances in which the hydraulic pump changes output (e.g., pump speed) reduces the likelihood for “whining” or other annoying noise to be transmitted to the passenger cabin. As a result, the foregoing arrangement is expected to increase passenger comfort. 
     Another aspect of at least some of the embodiments described above is that the change in controller mode, and therefore motor and pump output, can automatically precede a change in demand on the hydraulic system. For example, as discussed above, the hydraulic pump available power can increase prior to takeoff in anticipation of increased loads experienced during takeoff, and can increase after touchdown in anticipation of higher loads required during thrust reverser deployment. An advantage of this arrangement is that it allows the motor and pump time to increase output prior to an increased load being placed on the system, which in turn results in the increased load demands being met more quickly. 
     One aspect of an embodiment shown in  FIG. 3  is that the controller mode for each of the four motors coupled to the hydraulic system can be the same. For example, during takeoff and climb, all four motor controllers  111   a - 111   d  are at mode III. In other embodiments, different motor controllers can have different modes at the same time. This arrangement can allow for additional flexibility in establishing hydraulic pump output. 
     As is also shown in  FIG. 3 , not all the hydraulic pumps need be active at the same time. For example, during mode I, only the centrally-located motors  111   c - 111   d  need be active, and the outboard motors  111   a - 111   b  can be shut down. During mode II, only one of the centrally-located motors  111   c - 111   d  need be operational, as indicated by dashed line  133   a . During descent, both the centrally-located motors  111   c - 111   d  can be active, and optionally, only one of the outboard motors  111   a - 111   b  can also be activated (indicated by dashed line  133   b ), and then joined by the other outboard motor during approach and landing. 
     In other embodiments, motor controllers associated with non-hydraulic loads can substitute for failed or otherwise inactive motor controllers that normally direct the operation of motors coupled to hydraulic pumps, to provide a measure of redundancy for the hydraulic system. For example,  FIG. 4  illustrates a process  400  that includes directing a first motor to drive a hydraulic pump via commands from a first motor controller (process portion  401 ) and directing a second motor to produce power via a command from a second motor controller (process portion  402 ). The second motor can provide power to a non-hydraulic system, for example, an ECS compressor or nitrogen generation system. Process portions  401  and  402  correspond to a first mode of operation. In process portion  403 , a request is received for a change in this mode, which, in this case, can be independent of the overall operation mode of the aircraft described above with reference to  FIG. 3 . For example, the request for a mode change can correspond to an indication that the first motor controller has failed. In response to this request, the first motor controller can be decoupled from the first motor (process portion  404 ) and the second motor controller can be decoupled from the second motor (process portion  405 ). In process portion  406 , the first motor is directed to drive the hydraulic pump via commands from the second motor controller. Accordingly, the second motor controller is substituted for the first motor controller. 
       FIG. 5  is a schematic illustration of a system for substituting a motor controller associated with a non-hydraulic load for a failed or otherwise inactive motor controller associated with a hydraulic pump. The system can include one or more buses  112  (shown as a first bus  112   a  and a second bus  112   b ), each of which provides power to a corresponding first hydraulic motor controller  113   a  and a second hydraulic motor controller  113   b . The first bus  112   a  also provides power to a backup or non-hydraulic motor controller  513   a  and the second bus  112   b  also provides power to a corresponding second backup or non-hydraulic motor controller  513   b . During normal operations, the first hydraulic motor controller  113   a  controls a first hydraulic pump motor  111   a , the second hydraulic motor controller  113   b  controls a second hydraulic pump motor  111   b , the first backup motor controller  513   a  controls a first non-hydraulic load  520   a , and the second backup motor controller  513   b  controls a second non-hydraulic load  520   b . A switch device  514  is coupled between the motor controllers and the loads to selectively couple motor controllers with the appropriate loads. Accordingly, the switch device  514  can include first and second primary switches  515   a ,  515   b  that are normally closed to couple the corresponding hydraulic motor controllers with the corresponding hydraulic pumps. Third and fourth primary switches  515   c ,  515   d  are also normally closed to provide a connection between the backup motor controllers  513   a ,  513   b  and the corresponding non-hydraulic loads  520   a ,  520   b . If either of the hydraulic motor controllers  113   a ,  113   b  fail or are otherwise deactivated, then the corresponding primary switch  515   a ,  515   b  is opened, as shown in  FIG. 5 , and corresponding backup switch  516   a ,  516   b  is closed, as is also shown in  FIG. 5 . Accordingly, the second backup motor controller  513   b  controls the first hydraulic pump motor  111   a , and/or the first backup motor controller  513   a  controls the second hydraulic pump motor  111   b.    
     One advantage of embodiments of systems having the features described above with reference to  FIGS. 4 and 5  is that the backup or non-hydraulic motor controllers can substitute for the hydraulic motor controllers in the event of a failure in the hydraulic motor controllers. Accordingly, the backup motor controllers can decouple from a less important load and provide power to a more important load in the event that such power is needed. The backup motor controllers can accordingly be of the same size and/or capability as the hydraulic motor controllers, or can have a size and/or capability that is larger than that of the hydraulic motor controllers in order to support this substitution. 
     As illustrated in  FIGS. 1-5  and the accompanying text, a method is disclosed for controlling an aircraft system. In this method, in an aircraft power system, the method includes receiving an indication of an operation mode of the aircraft, automatically selecting a generally constant output level from among a fixed number of multiple, preset output levels, based at least in part on the operation mode. In one variant, the method may include directing an electric motor  111   a - 111   d  to produce the selected output level. In another variant, the method may include directing the electric motor  111   a - 111   d  to operate at a fixed speed as a load on the electric motor  111   a - 111   d  changes. In one additional variant, the method may include directing the electric motor  111   a - 111   d  to produce the selected output level before the selected output level is required by a load device coupled to and driven by the electric motor  111   a - 111   d.    
     In one alternative, the method may include directing the electric motor  111   a - 111   d  to produce the selected output level in excess of an output level required by a load, coupled to the electric motor  111   a - 111   d . In another alternative, the step of wherein automatically selecting a generally constant output level is based at least in part on a change in a position of a high lift device of the aircraft. In another variant, receiving an indication includes receiving an indication of a change in a high lift device position and changing an output includes increasing the output if the high lift device is moved to a deployed setting and decreasing the output if the high lift device is moved to a stowed setting. In yet another variant, wherein automatically changing the output of the electric motor  111   a - 111   d  includes automatically changing the output to one of a fixed number of preset values, based at least in part on a change in the operation mode of the aircraft. 
     In still another alternative, wherein the electric motor  111   a - 111   d  is a first electric motor  111   a  directed by a first motor controller  113   a , and wherein the method further includes the steps of during a first mode of operation: directing the first motor  111   a  to drive a hydraulic pump  124   a  via a command from the first motor controller  113   a  (process portion  401 ); and directing a second electric motor  520   b  to produce power, via a command from a second motor controller  513   b ; and during a second mode of operation (process portion  402 ): decoupling the first motor controller  113   a  from the first electric motor  111   a  (process portion  404 ); decoupling the second motor controller  513   b  from the second electric motor  520   b  (process portion  405 ); coupling the second motor controller  513   b  to the first electric motor  111   a ; and directing the first electric motor  111   a  to drive the hydraulic pump  124   a  via commands from the second motor controller  513   b  (process portion  406 ). 
     In another alternative, wherein directing the second electric motor  520   b  includes directing the second electric motor  520   b  to drive a fan for an aircraft environmental control system. In another variant, wherein directing a second electric motor  520   b  includes directing a second electric motor  520   b  having an output capability at least approximately the same as an output capability of the first electric motor  111   a.    
     From the foregoing, it will be appreciated that specific embodiments of the invention have been described herein for purposes of illustration, but that various modifications may be made without deviating from the invention. For example, the motor controllers may have more or fewer than the number of fixed modes described in certain embodiments above. The modes may correspond to different flight regimes than those discussed above. Certain embodiments were described in the context of particular systems (e.g., hydraulic pump motors, ECS systems, and nitrogen generation systems), but may be applied to other systems and/or combinations of systems in other embodiments. Aspects of the invention described in the context of particular embodiments may be combined or eliminated in other embodiments. For example, aspects of the backup motor controller functions may be provided in combination with motor controllers operating with a fixed number of predetermined modes. Further, while advantages associated with certain embodiments of the invention have been described in the context of those embodiments, other embodiments may also exhibit such advantages, and not all embodiments need necessarily exhibit such advantages to fall within the scope of the invention. Accordingly, the invention is not limited except as by the appended claims.