Patent Publication Number: US-2020285207-A1

Title: Distributed Control Modules with Cumulating Command References

Description:
FIELD 
     The present disclosure generally pertains to distributed control systems, and more particularly to distributed control systems that include distributed control modules configured to provide cumulating command references and corresponding cumulating control commands. 
     BACKGROUND 
     Distributed control systems generally provide increased reliability by localizing control commands to various distributed control modules associated with corresponding controllable components. A distributed control system may include a main processing unit that sends nominal command references to various distributed control modules. In some implementations, a distributed control module may have a faster clock than that of a main processing unit. Differences in unit time intervals between a main processing unit and a distributed control module may introduce noise into a control loop. Such noise may be introduced, for example, when a distributed control module attempts to output control commands at a faster unit time interval than the unit time interval at which nominal command references are provided by the main processing unit. While the distributed control module could be slowed to reduce noise, this may reduce the responsiveness of a control loop implemented by the distributed control module to control the controllable component. 
     Accordingly, there exists a need for improved distributed control systems, including distributed control systems with distributed control modules that have improved capabilities to operate at unit time intervals that are faster than that of a main processing unit. 
     BRIEF DESCRIPTION 
     Aspects and advantages will be set forth in part in the following description, or may be obvious from the description, or may be learned through practicing the presently disclosed subject matter. 
     In one aspect, the present disclosure embraces methods of controlling a controllable component. An exemplary method may include receiving a nominal command reference from a main processing unit, determining a series of cumulating command references based at least in part on the nominal command reference, and outputting a series of cumulating control commands to a controllable component. The series of cumulating control commands may be based at least in part on the series of cumulating command references. 
     In another aspect, the present disclosure embraces distributed control systems. An exemplary distributed control system may include a main processing unit, a distributed control module, and a controllable component. The distributed control module may be configured to receive a nominal command reference from the main processing unit, determine a series of cumulating command references based at least in part on the nominal command reference; and output a series of cumulating control commands to the controllable component. The series of cumulating control commands may be based at least in part on the series of cumulating command references. 
     In yet another aspect, the present disclosure embraces computer readable medium. Exemplary computer readable medium may include computer-executable instructions, which, when executed by one or more processors of a distributed control module, cause the distributed control module to: receive a nominal command reference from the main processing unit; determine a series of cumulating command references based at least in part on the nominal command reference; and output a series of cumulating control commands to the controllable component. The series of cumulating control commands may be based at least in part on the series of cumulating command references. 
     These and other features, aspects and advantages will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary embodiments and, together with the description, serve to explain certain principles of the presently disclosed subject matter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended Figures, in which: 
         FIG. 1  shows a block diagram depicting an exemplary distributed control system; 
         FIG. 2  shows a block diagram depicting an exemplary distributed control module that may be included in a distributed control system; 
         FIG. 3  shows a block diagram depicting an exemplary controller of a distributed control module; 
         FIGS. 4A and 4B  show block diagrams depicting exemplary aspects of a control command module of a distrusted control module, including aspects of a command reference generation module; 
         FIGS. 5A-5C  graphically show exemplary nominal command references input to a command reference generation module and corresponding cumulating command references output by the command reference generation module; 
         FIG. 6  shows a block diagram depicting exemplary aspects of a control command module of a distrusted control module, including aspects of a control logic module; 
         FIGS. 7A-7E  shows block diagrams depicting aspects of exemplary methods of controlling a controllable component; and 
         FIG. 8 . shows a schematic, cross-sectional view of a turbofan engine that includes a distributed control system with a distributed control module configured according to the present disclosure. 
     
    
    
     Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the present disclosure. 
     DETAILED DESCRIPTION 
     Reference now will be made in detail to exemplary embodiments of the presently disclosed subject matter, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation and should not be interpreted as limiting the present disclosure. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the scope or spirit of the present disclosure. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present disclosure covers such modifications and variations as come within the scope of the appended claims and their equivalents. 
     The present disclosure generally provides distributed control systems and distributed control modules that are configured to control controllable components according to a series of control commands that are based on a series of cumulating command references. A distributed control module may provide a series of cumulating command references by upsampling a nominal command reference from a main processing unit. In exemplary embodiments, the distributed control module (DCM) may have a faster DCM unit time interval (t) than that of the main processing unit (MPU), allowing the distributed control module to provide control commands at a faster unit time interval than the MPU unit time interval (u) associated with nominal command references from the main processing unit. The presently disclosed cumulating command references may reduce noise in a control loop, for example, by providing a series cumulating control commands that distribute a nominal command reference from the main processing unit across a DCM unit time interval (t). The cumulating control commands may be provided based on a series of cumulating command references, which may be generated by a command reference generation module or other aspect of a distributed control module. 
     While a DCM may be configured to operate with a DCM unit time interval (t) that is faster than an MPU unit time interval (u), in general, the nominal command references from the main processing units may preferably be distributed across the DCM unit time interval (t) rater than applying the nominal command references in a single step-change because such a step-change may introduce an undesired transient response. Such transient response may be attributable to the faster unit time interval of the DCM versus the MPU, and the magnitude of the transient response may be proportionate to such difference in DCM and MPU unit time intervals. The nominal command references from the MPU may be distributed across the DCM unit time interval (t) evenly or substantially evenly (e.g., according to the nearest integer or non-integer value). 
     Exemplary embodiments may be configured to automatically handle both synchronous and asynchronous time domains. When the DCM and the MPU have synchronous time domains, the nominal command references may be distributed evenly according to the nearest integer value. When the DCM and the MPU have asynchronous time domains, the nominal command references may be distributed substantially evenly according to the nearest integer value. 
     Distributed control modules may be configured according to the present disclosure so as to allow for “plug and play” installation of the distributed control module into a distributed control system. This includes distributed control modules configured to self-configure for providing cumulating command references and corresponding cumulating control commands. Exemplary distributed control modules may be configured to compatibly provide cumulating command references and corresponding cumulating control commands using nominal command references provided at any MPU unit time interval (u). This includes distributed control system configurations in which a DCM unit time interval (t) and an MPU unit time interval (u) have synchronous time domains, as well as configurations in which a DCM unit time interval (t) and an MPU unit time interval (u) have asynchronous time domains. 
     It is understood that terms “upstream” and “downstream” refer to the relative direction with respect to fluid flow in a fluid pathway. For example, “upstream” refers to the direction from which the fluid flows, and “downstream” refers to the direction to which the fluid flows. It is also understood that terms such as “top”, “bottom”, “outward”, “inward”, and the like are words of convenience and are not to be construed as limiting terms. As used herein, the terms “first”, “second”, and “third” may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components. The terms “a” and “an” do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item. 
     Here and throughout the specification and claims, range limitations are combined and interchanged, and such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise. For example, all ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other. 
     Approximating language, as used herein throughout the specification and claims, is applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about”, “approximately”, and “substantially”, are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value, or the precision of the methods or machines for constructing or manufacturing the components and/or systems. 
     Exemplary embodiments of the present disclosure will now be described in further detail.  FIG. 1  shows an exemplary distributed control system  100 . The distributed control system  100  may include a control system for a turbomachine or any other engine, machine, process, or plant, and may include a large number of distributed control modules distributed throughout the distributed control system  100 . By way of example, a distributed control system  100  may include or be incorporated into a full authority direct engine control (FADEC) system or an engine control unit (ECU) for a turbomachine and/or an aircraft. 
     As shown, an exemplary distributed control system  100  may include a main processing unit  102 , one or more distributed control modules  104 , and one or more controllable components  112  respectively associated with corresponding distributed control modules  104 . The distributed control system  100  distributes control processing among the distributed control modules  104 . Typically, the main processing unit  102  provides centralized, supervisory control for the distributed control modules  104 , and the respective distributed control modules  104  implement one or more control loops for controlling one or more controllable components  112  associated with the corresponding distributed control module  104  according to the supervisory control from the main processing unit  102 . A main processing unit  102  may include a data warehouse and a server configured to transmit data from the data warehouse to distributed control modules  104  and/or to receive data from the distributed control modules  104  and to store the received data in the data warehouse for further purposes. 
     Operations and methods associated with a distributed control system  100 , including operations and methods associated with a distributed control module  104 , may be implemented within the context of a turbomachine  800  ( FIG. 8 ), such as a turbomachine  800  installed on an aircraft. The operations and methods described herein may be carried out, for example, during flight, as well as during pre-flight and/or post-flight procedures. 
     Any number of distributed control modules  104  may be provided. By way of example, the exemplary distributed control system  100  shown in  FIG. 1  includes a first distributed control module  106 , a second distributed control module  108 , and an Nth distributed control module  110 . A distributed control module  104  may be associated with one or more controllable components  112 . By way of example, the exemplary distributed control system  100  shown in  FIG. 1  includes a first controllable component  114  associated with the first distributed control module  106 , a second controllable component  116  associated with the second distributed control module  108 , and an Nth controllable component  118  associated with the Nth distributed control module  110 . However, it will be appreciated that a plurality of controllable components  112  may be associated with an individual distributed control module  104 , and/or that an individual controllable component  112  may be associated with a plurality of distributed control modules  104 . 
     By way of example, a controllable component  112  may include an actuator or a servo-actuator, and a sensor may include a position sensor configured to measure a position of the actuator or servo-actuator. As another example, a controllable component  112  may include a variable-geometry component, or an actuator or servo-actuator coupled to a variable-geometry component. Exemplary variable-geometry components include fuel valves, variable-position fan blades, variable-position guide vanes, variable-position compressor blades, and variable-position turbine blades. 
     An exemplary distributed control module  104  is shown in  FIG. 2 . As shown, a distributed control module  104  may include one or more controllers  200  communicatively coupled to a main processing unit  102  and one or more controllable components  112 . The controller may be configured to control the one or more controllable components  112  by implementing a control loop or combination of control loops under supervisory control from the main processing unit  102 . Exemplary control loops that may be implemented by the controller  200  include open-loop control, closed-loop control, as well as a combination thereof. 
     As used herein, the terms “open-loop” or “open-loop control” generally refer to a control loop or control command that does not receive feedback from a measured output variable of a system subject to such control loop or control command. 
     As used herein, the terms “closed-loop” or “closed-loop control” generally refer to a control loop or control command that utilizes as an input or depends on feedback from, a measured output variable of a system subject to such control loop or control command. Such a measured output variable may include a measurement from a sensor configured to measure a system variable that depends on an input by such control loop or control command. A controller  200  that utilizes closed-loop control may compare a measured output variable to a setpoint to determine an error value, which may be used, for example, in a PID control model or any other desired control model. 
     An exemplary distributed control module  104  may include a communication interface  204  configured to communicatively couple the distributed control module  104  and the main processing unit  102  via wired or wireless communication lines  205 . The communication lines  205  may include a data bus or a combination of wired and/or wireless communication links. The communication interface  204  may include any suitable components for interfacing with one or more network(s), including for example, data busses, transmitters, receivers, ports, controllers, antennas, and/or other suitable components. An exemplary distributed control module  104  may additionally include a power supply interface  206  operably coupled to a power supply unit  208 , and a sensor interface  210  operably coupled to one or more sensors  212 . 
     Now turning to  FIG. 3 , an exemplary controller  200  of a distributed control module  104  will be described. As shown, an exemplary controller  200  may include a control command module  300 , a command reference generation module  302 , and a control logic module  304 . The command reference generation module  302  and/or the control logic module  304  may be included as part of the control command module or as separate modules of the controller  200 . 
     The control command module  300  may also include one or more control modes, including one or more closed loop control modes, one or more open loop control modes, and/or a disconnect control mode. The control command module  300  may be configured to output control commands to one or more controllable components. The control commands may be based at least in part on a series of cumulating command references as described herein. 
     The command reference generation module  302  may be configured to generate and/or select a command reference for use in control logic of a control loop handled by the controller  200  or the distributed control module  104 . The command reference generation module  302  may generate a series of cumulating command references as described herein. Additionally, or in the alternative, the command reference generation module  302  may be configured to select from among a number of possible command references for use in the control loop, or to cause another module associated with the controller  200  to utilize one of a number of possible command references in the control loop. 
     The control logic module  304  may be configured to process control logic associated with one or more control loops handled by the controller  200  or the distributed control module  104 , including control logic for one or more closed-loop and/or open-loop control regimes. The control logic may include machine-executable instructions that can be executed by one or more processors associated with the controller  200  or the distributed control module  104 . 
     The controller  200  may include one or more computing devices, including one or more processors  306  and one or more memory devices  308 , and such computing devices are preferably located locally to the distributed control module  104 . The one or more processors  306  may include any suitable processing device, such as a microprocessor, microcontroller, integrated circuit, logic device, and/or other suitable processing device. The one or more memory devices  308  may include one or more computer-readable media, including but not limited to non-transitory computer-readable media, RAM, ROM, hard drives, flash drives, and/or other memory devices  308 . 
     The one or more memory devices  308  may store information accessible by the one or more processors  306 , including machine-executable instructions  310  that can be executed by the one or more processors  306 . The instructions  310  may include any set of instructions  310  which when executed by the one or more processors  306  cause the one or more processors  306  to perform operations. In some embodiments, the instructions  310  may be configured to cause the one or more processors  306  to perform operations, including operations for which the controller  200 , the distributed control module  104 , and/or the one or more computing devices are configured. More particularly, such operations may include operations of the command reference generation module  302 , operations of the control logic module  304 , and/or operations of the control command module  300 . Operations of the command reference generation module  302  may include generating a series of cumulating command references as described herein. 
     Processor  306  operations may additionally include controlling the one or more controllable components  112  according to a control loop, for example, using a series of cumulating command references  406 . Such operations may additionally or alternatively include receiving inputs from the one or more sensors  212  and controlling the one or more controllable components  112  responsive to the one or more sensors  212  according to a control loop. Such operations may additionally or alternatively be carried out according to supervisory control provided by the main processing unit  102 . The machine-executable instructions  310  can be software written in any suitable programming language or can be implemented in hardware. Additionally, and/or alternatively, the instructions  310  can be executed in logically and/or virtually separate threads on processors  306 . 
     The memory devices  308  may store data  312  accessible by the one or more processors  306 . The data  312  can include current or real-time data, past data, or a combination thereof. The data  312  may be stored in a data library  314 . As examples, the data  312  may include data  312  associated with or generated by the main processing unit  102 , the one or more sensors  212 , and/or the distributed control module  104 , including data  312  associated with or generated by a controller  200  or a processor  306 . The data  312  may also include other data sets, parameters, outputs, information, associated with the distributed control module  104  or the distributed control system  100 . 
     The communication interface  204  may additionally or alternatively allow the distributed control module  104  and/or the main processing unit  102  to communicate with a user interface  316 . 
     Now referring to  FIGS. 4A and 4B , and exemplary command reference generation module  302  will be described. As shown in  FIG. 4A , an exemplary command reference generation module  302  may include a delay line module  400  and an accumulator module  402 . The command reference generation module  302  may be configured to receive a nominal command reference  404  and to determine a series of cumulating command references  406  based at least in part on the nominal command reference  404 . The series of cumulating command references  406  may be determined at least in part using the delay line module  400  and/or the accumulator module  402 . 
     The main processing unit  102  may operate according to an MPU unit time interval (u), with (u) representing a unit of time of an MPU clock. The distributed control module  104  may operate according to a DCM unit time interval (t), with (t) representing a unit of time of a DMC clock. The command reference generation module  302  may automatically generate cumulating command references  406  regardless of whether the DCM unit time interval (t) and the MPU unit time interval (u) may have synchronous or asynchronous time domains. The MPU unit time interval (u) may exceed the DCM unit time interval (t). Generally, the command reference generation module  302  may be configured to augment the nominal command reference  404  from the main processing unit  102  based at least in part on a difference between the unit of time of the DMC clock (t), and the unit of time of the MPU clock, (u). For example, in exemplary embodiments the unit of time of the DMC clock (t) may have a shorter duration than the unit of time of the MPU clock (u), such that the distributed control module  104  may be capable of operating faster than the main processing unit  102 . In one scenario, a distributed control module may be capable of determining and/or outputting command references and/or control commands to a controllable component  112  at a rate that exceeds the rate at which nominal command references  404  are provided by the main processing unit  102 . In this scenario, the command reference generation module  302  may be configured to upsample, expand, or interpolate the nominal command reference  404  so as to provide more frequent command references and/or more frequent control commands, such as the cumulating command references  406  and/or the cumulating control commands described herein. 
     As shown in  FIGS. 4A and 4B , the command reference generation module  302  may include a delay line module  400  configured to provide incremental command references  408 , and an accumulator module  402  configured to provide cumulating command references. The incremental command references  408  may be incremented by a command reference reciprocal (K)  410 , in which (K) represents a real number. In exemplary embodiments, a command reference reciprocal (K)  410  may be an integer; however, in other embodiments a command reference reciprocal (K)  410  may also be a non-integer factor. The command reference reciprocal (K)  410  may be input or selected by a user, such as via a user interface  204 . Additionally, or in the alternative, the command reference reciprocal (K)  410  may be determined or selected by a distributed control module  104  without requiring a user input. The nominal command reference  404  may include an MPU command reference from a main processing unit divided by the command reference reciprocal (K)  410 . 
     In exemplary embodiments, the command reference reciprocal (K)  410  may be input, determined, or selected such that a product of a DCM unit time interval (t) and the command reference reciprocal (K)  410  may be proportional to an MPU unit time interval (u) to within one unit of the DCM unit time interval (t). In some embodiments, the DCM unit time interval (t) and the MPU unit time interval (u) may have synchronous time domains, for example, such that (K)-increments of the DCM unit time interval (t) equals one increment of the MPU unit time interval (u). Alternatively, in other embodiments the DCM unit time interval (t) and the MPU unit time interval (u) may have asynchronous time domains. However, regardless of whether such time domains are synchronous or asynchronous, in exemplary embodiments, the command reference reciprocal (K)  410  may be input, determined, or selected such that a product of the DCM unit time interval (t) and the command reference reciprocal (K)  410  is proportional to the MPU unit time interval (u) to within one unit of the DCM unit time interval (t). 
     In some embodiments, a command reference reciprocal (K)  410  may be input, determined, or selected such that (K)-increments of the DCM unit time interval (t) may fall within one increment of the MPU unit time interval (u) by less than one increment of the DCM unit time interval (t). For example, a command reference reciprocal (K)  410  may be input, determined, or selected such that (K)-increments of the DCM unit time interval (t) exceeds one increment of the MPU unit time interval (u) by less than one increment of the DCM unit time interval (t), or such that one increment of the MPU unit time interval (u) exceeds (K)-increments of the DCM unit time interval (t) by less than one increment of the DCM unit time interval (t). Alternatively, in some embodiments the command reference reciprocal (K)  410  may be input, determined, or selected such that (K)-increments of the DCM unit time interval (t) equals one increment of the MPU unit time interval (u). 
     The delay line module  400  may include one or more delay lines  412 , and a delay line  412  may be selected or configured based at least in part on the command reference reciprocal (K)  410 . For example, as discussed with reference to  FIG. 4B , a delay line  412  may include a series of (K)-unit delay operators  420 . A delay line  412  having a desired number of unit delay operators  420  may be determined, selected, generated, or configured by a distributed control module  104  and/or input or selected by a user. For example, as shown in  FIG. 4A , a delay line module  400  may include a plurality of delay lines  412  from which a distributed control module  104  and/or a user may select, such as a first delay line  414 , a second delay line  416 , and an Nth delay line  418 . 
     The distributed control module  104  and/or the delay line module  400  may determine or select a delay line  412  from among a plurality of delay lines  412 , for example, based at least in part on a command reference reciprocal (K)  410 . For example, a delay line  412  may be determined or selected that includes a series of (K)-unit delay operators  420 . By way of example, the first delay line  414  may include two delay lines  412 . The first delay line  414  may be determined or selected when the command reference reciprocal (K)  410  is 2. The second delay line  416  may include three delay lines  412 . The second delay line  416  may be determined or selected when the command reference reciprocal (K)  410  is 3. The Nth delay line  418  may include N delay lines  412 , and the Nth delay line  418  may be determined or selected when the command reference reciprocal (K)  410  is N. 
     In some embodiments, when the command reference reciprocal (K)  410  is a non-integer, the delay line  412  that has a number of unit delay operators  420  that most closely approximates the non-integer value of the command reference reciprocal (K)  410  may be determined or selected. For example, the first delay line  414  having two delay lines  412  may be selected when the command reference reciprocal (K)  410  is a non-integer of between 1.1 and 2.5. As another example, the second delay line  416  having three delay lines  412  may be selected when the command reference reciprocal (K)  410  is a non-integer of between 2.5 and 3.5. Further, the third delay line  418  having N delay lines  412  may be selected when the command reference reciprocal (K)  410  is a non-integer of between (N−0.5) and (N+0.5). 
     Alternatively, a distributed control module  104  and/or the delay line module  400  may generate or configure a delay line  412  so as to provide a series of (K)-unit delay operators  420 . For example, a distributed control module  104  may determine an MPU unit time interval (u) and a DCM unit time interval (t), and then the distributed control module  104  may determine a command reference reciprocal (K). The distributed control module  104  may then generate or configure a delay line  412  having a series of (K)-unit delay operators  420 . 
     Now turning to  FIG. 4B , an exemplary delay line module  400  and exemplary operations thereof will be further described. An exemplary delay line  412  may include (K)-unit delay operators  420 . By way of example, the command reference reciprocal (K)  410  may be three (3), and as shown, a corresponding delay line  412  may include three (3) unit delay operators  420 . Each of the unit delay operators  420  may be configured to delay the nominal command reference  404  input thereto by one DCM unit time interval (t), such as by perform a z-transform. The delay line module  400  may determine a series of K(t)-incremental command references  408  sequentially corresponding to one of (K)-increments of the DCM unit time interval (t), in which K(t) represents (K) increments as a function of (t). The series of K(t)-incremental command references  408  may be determined by the delay line module  400  at least in part using the delay line  412  and the command reference reciprocal (K)  410 . 
     The delay line  412  may be configured to delay the nominal command reference  404  using the series of (K)-unit delay operators  420  so as to provide a series of K(t)-delayed nominal command references  404 . The K(t)-delayed nominal command reference  404  may be sequentially delayed by one of the (K)-increments of the DCM unit time interval (t). For example, a first unit delay operator  422  may receive the nominal command reference  404  at an initial DCM unit time (t+0) and delay the nominal command reference  404  by a first increment of the DCM unit time interval (t). The first unit delay operator  422  may provide the nominal command reference  404 , as delayed (t+1), to a second unit delay operator  424  at the first increment of the DCM unit time interval (t). The second unit delay operator  424 , having received the nominal command reference  404 , as delayed (t+1), may further delay the nominal command reference  404  by a second increment of the DCM unit time interval (t+2). The second unit delay operator  424  may provide the nominal command reference  404 , as delayed (t+2), to a third unit delay operator  426  at the second increment of the DCM unit time interval (t+2). The third unit delay operator  426 , having received the nominal command reference  404 , as delayed (t+2), may further delay the nominal command reference  404  by a third increment of the DCM unit time interval (t+3). The third unit delay operator  426  may provide the nominal command reference  404 , as delayed (t+3), to a subtraction operator  428  at the third increment of the DCM unit time interval (t+3). 
     Meanwhile, the first unit delay operator  422  may sequentially receive subsequent nominal command references  404  at sequentially subsequent increments of the DCM unit time interval (t), with such sequentially subsequent nominal command references  404  passing through the series of unit delay operators  420  at sequential DCM unit time intervals (t) to the subtraction operator  428 . The nominal command reference  404  may be updated by the main processing unit  102  at MPU unit time intervals (u). 
     The subtraction operator  428  may be configured to sequentially subtract respective ones of the series of K(t)-delayed nominal command references  404  from the nominal command reference  404  corresponding to respective ones of the (K)-increments of the DCM unit time interval (t), providing a series of K(t)-reference differences  430  sequentially corresponding to one of the (K)-increments of the DCM unit time interval (t). For example, at an initial DCM unit time (t+0), the subtraction operator  428  may subtract an initial condition from the nominal command reference  404 . At the initial DCM unit time (t+0), the series of (K)-unit delay operators  420  would have not yet provided the nominal command reference  404  to the subtraction operator  428 , because the series of (K)-unit delay operators  420  would delay the nominal command reference  404  by the (K)-increments of the DCM unit time interval (t). 
     To illustrate, if a nominal command reference  404  has a value of 5 and an initial condition has a value of zero (0), the subtraction operator  428  may subtract zero (0) from  5  at an initial DCM unit time (t+0). At (K)-increments of the DCM unit time interval (t+K), the series of (K)-unit delay operators  420  may provide the nominal command reference  404 , as delayed (t+K), to the subtraction operator  428 , and the subtraction operator  428  may subtract the nominal command reference  404  at (t+K) from the nominal command reference  404  as delayed (t+K). For example, if the nominal command reference  404  still has a value of 5 at a DCM unit time (t+K), the subtraction operator  428  may subtract 5 from  5  at the DCM unit time (t+K). As another example, if the nominal command reference  404  has a value of 10 at a DCM unit time (t+K), the subtraction operator  428  may subtract 5 from  10  at the DCM unit time (t+K). 
     Still referring to  FIG. 4B , the subtraction operator  428  may provide a series of K(t)-reference differences  430 . A multiplier  432  may be configured to sequentially multiply respective ones of the series of K(t)-reference differences  430  by the command reference reciprocal (K)  410  corresponding to respective ones of the (K)-increments of the DCM unit time interval (t). Such sequential multiplying by the multiplier  432  may provide a series of K(t)-incremental command references  408  sequentially corresponding to one of the (K)-increments of the DCM unit time interval (t). 
     Referring again to  FIG. 4A , the accumulator module  402  may receive the series of K(t)-incremental command references  408  and determine a series of K(t)-cumulating command references  406  sequentially corresponding to one of the (K)-increments of the DCM unit time interval (t). The series of K(t)-cumulating command reference  406  may be determined based at least in part on the series of K(t)-incremental command references  408 . The accumulator module  402  may be configured to accumulate the series of K(t)-incremental command references  408  sequentially corresponding to one of the (K)-increments of the DCM unit time interval (t). For example, the accumulator module  402  may add or sum (a) a K(t+0)-incremental command reference  408  corresponding to a K(t+0)-DCM unit time interval (t+0) and (b) a K(t−1)-incremental command reference  408  corresponding to a K(t−1)-DCM unit time interval (t). 
     In an exemplary embodiment, as shown in  FIG. 4A , an accumulator module  402  may include a resampler  434  and an addition operator  436 . The resampler  434  may be configured to sequentially resample the series of K(t)-cumulating command references  406  and sequentially delay the K(t)-cumulating command references  406  by an increment of the DCM unit time interval (t). For example, the resampler  434  may be configured to resample the K(t+0)-cumulating command reference  406  corresponding to the K(t+0)-DCM unit time interval (t+0), and to delay the K(t+0)-cumulating command reference  406  by the DCM unit time interval (t). The resampler  434  may provide to the addition operator  436 , the (t+0)-cumulating command reference  406 , as delayed (t+1). Meanwhile the delay line module  400  may provide to the addition operator  436 , a K(t+1)-incremental command reference  408  corresponding to a K(t+1)-DCM unit time interval (t). The addition operator  436  may add or sum (a) the K(t+1)-incremental command reference  408  corresponding to the K(t+1)-DCM unit time interval (t) and (b) the K(t+0)-cumulating command reference after having been delayed, at the resampler  434 , by the DCM unit time interval (t). 
     Now referring to  FIGS. 5A-5C , graphically depicted are exemplary nominal command references  404  input to a command reference generation module  302  and corresponding cumulating command references  406  output by the command reference generation module  302 .  FIG. 5A  corresponds to a distributed control module  104  that has a DCM clock providing a DCM unit time interval (t) that is synchronous with an MPU clock providing an MPU unit time interval (u), such that the DCM unit time interval (t) and the MPU unit time interval (u) may have synchronous time domains. As shown, the MPU unit time interval (u) is three times longer than the DCM unit time interval (t). In the example depicted in  FIG. 5A , the command reference reciprocal (K)  410  has been accordingly set to 3. As a result, the command reference generation module  302  provides a series of K(t)-cumulating command references  406  that cumulate over three intervals of the DCM unit time interval (t), matching the nominal command reference  404  at intervals of the MPU unit time interval (u). 
       FIGS. 5B and 5C  correspond to a distributed control module  104  that has a DCM clock providing a DCM unit time interval (t) that is asynchronous with an MPU clock providing an MPU unit time interval (u), such that the DCM unit time interval (t) and the MPU unit time interval (u) may have asynchronous time domains. In the scenarios depicted in  FIGS. 5B and 5C , the MPU unit time interval (u) is approximately three times longer than the DCM unit time interval (t), and the command reference reciprocal (K)  410  has been set to 3. As shown in  FIG. 5B , the MPU unit time interval (u) is slightly greater than three times the DCM unit time interval (t). As shown in  FIG. 5C , the MPU unit time interval (u) is slightly less than three times the DCM unit time interval (t). In both of these scenarios, the next K(t)-cumulating command reference  406  following an interval of the MPU unit time interval (u) may be delayed by a fraction of the DCM unit time interval (t). Such delay may be accepted and still realize advantages of the present disclosure, for example, because the delay is less than an interval of the MPU unit time interval (u). Alternatively, the command reference reciprocal (K)  410  may be set to a non-integer value, which may eliminate such asynchronous time domain. 
     Now referring to  FIG. 6 , an exemplary control logic module  304  will be described. As shown in  FIG. 6 , an exemplary control logic module  304  may include a plurality of control regimes which may be selected. By way of example, a control logic module  304  may include one or more variations of closed-loop control logic  600  and/or one or more variations of open-loop control logic  602 . The control logic module  304  may select from among one or more variations of closed-loop or open-loop control logic  600 ,  602 , based on any desired criterion. For example, control logic  600 ,  602  may be selected based on an input from the main processing unit  102  and/or based at least in part on an input from one or more sensors  212 . The control logic module  304  may be configured to receive a series of cumulating command references  406 , such as from the command reference generation module  302 . Using selected control logic  600 ,  602 , the control logic module  304  may be configured to determine a series of cumulating control commands  604 . The series of cumulating control commands  604  may be determined based at least in part on the series of cumulating command references  406 . The control logic module  304  and/or the control command module  300  may further be configured to output the series of cumulating control commands  604  to a controllable component  112 . 
     Now turning to  FIGS. 7A-7E , exemplary methods  700  of controlling a controllable component  112  will be discussed. As shown in  FIG. 7A , an exemplary method  700  may include, at block  702 , receiving a nominal command reference  404  from a main processing unit  102 ; at block  704 , determining a series of cumulating command references  406  based at least in part on the nominal command reference  404 ; and at block  706 , determining a series of cumulating control commands  604  for a controllable component  112 . The series of cumulating control commands  604  may be based at least in part on the series of cumulating command references  406 . An exemplary method  700  may additionally include, at block  708 , outputting the series of cumulating control commands  604  to a controllable component  112 . 
       FIG. 7B  shows exemplary aspects of determining a series of cumulating command references  406  based at least in part on the nominal command reference  404 , at block  704 . As shown, in an exemplary method  700 , block  704  may include, at block  710 , determining a command reference reciprocal (K)  410 . In exemplary embodiments, (K) may represent a real number, including an integer or a non-integer value. An exemplary method  700  may additionally include, at block  712 , determining a series of K(t)-incremental command references  408  sequentially corresponding to one of (K)-increments of a DCM unit time interval (t), in which (t) represents a unit of time of a DMC clock, and K(t) represents (K) increments as a function of (t). Further, an exemplary method may include, at block  714 , determining a series of K(t)-cumulating command references  406  sequentially corresponding to one of the (K)-increments of the DCM unit time interval (t). The series of K(t)-cumulating command reference  406  may be determined based at least in part on the series of K(t)-incremental command references  408 . 
       FIG. 7C  shows exemplary aspects of determining a series of K(t)-incremental command references  408  sequentially corresponding to one of (K)-increments of a DCM unit time interval (t), at block  712 . As shown, in an exemplary method  700 , block  712  may include, at block  716 , delaying the nominal command reference  404  by a delay line  412 . The delay line  412  may include a series of (K)-unit delay operators  420 . The series of (K)-unit delay operators  420  may be configured to provide a series of K(t)-delayed nominal command references  404 , with the K(t)-delayed nominal command reference  404  sequentially delayed by one of the (K)-increments of the DCM unit time interval (t). An exemplary method  700  may additionally include, at block  718 , sequentially subtracting respective ones of the series of K(t)-delayed nominal command references  404  from the nominal command reference  404  corresponding to respective ones of the (K)-increments of the DCM unit time interval (t), providing a series of K(t)-reference differences  430  sequentially corresponding to one of the (K)-increments of the DCM unit time interval (t). At block  720 , an exemplary method  700  may include sequentially multiplying respective ones of the series of K(t)-reference differences  430  by the command reference reciprocal (K)  410  corresponding to respective ones of the (K)-increments of the DCM unit time interval (t), providing the series of K(t)-incremental command references  408  sequentially corresponding to one of the (K)-increments of the DCM unit time interval (t). 
       FIG. 7D  shows an exemplary embodiment of determining a series of K(t)-cumulating command references  406  sequentially corresponding to one of the (K)-increments of the DCM unit time interval (t), at block  714 . As shown, in an exemplary method  700 , block  714  may include, at block  722 , accumulating the series of K(t)-incremental command references  408  sequentially corresponding to one of the (K)-increments of the DCM unit time interval (t). The accumulating may include summing a K(t+0)-incremental command reference  408  corresponding to a K(t+0)-DCM unit time interval (t+0) and a K(t−1)-incremental command reference  408  corresponding to a K(t−1)-DCM unit time interval (t). 
       FIG. 7E  shows another exemplary embodiment of determining a series of K(t)-cumulating command references  406  sequentially corresponding to one of the (K)-increments of the DCM unit time interval (t), at block  714 . As shown in  FIG. 7E , and exemplary method  700  may include, at block  724 , determining a K(t+0)-cumulating command reference  406  corresponding to a K(t+0)-DCM unit time interval (t+0). The K(t+0)-cumulating command reference  406  may include the K(t+0)-incremental command reference  408  corresponding to the K(t+0)-DCM unit time interval (t+0). An exemplary method may further include, at block  726 , resampling the K(t+0)-cumulating command reference  406  corresponding to the K(t+0)-DCM unit time interval (t+0), and at block  728 , delaying the K(t+0)-cumulating command reference  406  by the DCM unit time interval (t). At block  730 , an exemplary method  700  may include determining a K(t+1)-cumulating command reference  406  corresponding to a K(t+1)-DCM unit time interval (t). The K(t+1)-cumulating command reference  406  may include the sum of (a) a K(t+1)-incremental command reference  408  corresponding to a K(t+1)-DCM unit time interval (t) and (b) the K(t+0)-cumulating command reference  406  after having been delayed by the DCM unit time interval (t). 
     It will be appreciated that while the exemplary embodiments are generally depicted as a linear system, it will be appreciated that the scope of the present disclosure also embraces non-linear, higher-order, and otherwise more complex system. For example, it will be appreciated that the z-transforms depicted with respect to the command reference generation module  302  (e.g., the z-transforms for the unit delays in the delay line module  400  and/or for resampling in the accumulator module  402 ) may be implemented using other methods of Fourier transform, all of which are within the scope of the present disclosure. As another example, it will be appreciated that operations of the command reference generation module  302  may be implemented using other signal processing techniques, including, without limitation, recursive filters such as infinite impulse response filters or finite impulse response filters. 
     Aspects of the presently disclosure may be incorporated into, or otherwise utilized with, any process, system, or machine where a distributed control system  100  and/or distributed control module  104  may be desirable. By way of example, the present disclosure may be implemented with a turbomachine, such as a turbofan engine  800 .  FIG. 8  provides a schematic, cross-sectional view of a turbofan engine  800  in accordance with an exemplary embodiment of the present disclosure. The engine  800  may be incorporated into a vehicle, such as an aircraft, a marine vessel, or a land vehicle. For example, the engine  800  may be an aeronautical engine incorporated into an aircraft. Alternatively, however, the engine may be any other suitable type of engine for any other suitable vehicle. 
     For the embodiment depicted, the engine is configured as a high bypass turbofan engine  800 . As shown in  FIG. 8 , the turbofan engine  800  defines an axial direction A (extending parallel to a longitudinal centerline  801  provided for reference), a radial direction R, and a circumferential direction (extending about the axial direction A; not depicted in  FIG. 8 ). In general, the turbofan  800  includes a fan section  802  and a turbomachine  804  disposed downstream from the fan section  802 . 
     The exemplary turbomachine  804  depicted generally includes a substantially tubular outer casing  806  that defines an annular inlet  808 . The outer casing  806  encases, in serial flow relationship, a compressor section including a booster or low pressure (LP) compressor  810  and a high pressure (HP) compressor  812 ; a combustion section  814 ; a turbine section including a high pressure (HP) turbine  816  and a low pressure (LP) turbine  818 ; and a jet exhaust nozzle section  820 . The compressor section, combustion section  814 , and turbine section together define at least in part a core air flowpath  821  extending from the annular inlet  808  to the jet nozzle exhaust section  820 . The turbofan engine further includes one or more drive shafts. More specifically, the turbofan engine includes a high pressure (HP) shaft or spool  822  drivingly connecting the HP turbine  816  to the HP compressor  812 , and a low pressure (LP) shaft or spool  824  drivingly connecting the LP turbine  818  to the LP compressor  810 . 
     For the embodiment depicted, the fan section  802  includes a fan  826  having a plurality of fan blades  828  coupled to a disk  830  in a spaced apart manner. The fan blades  828  and disk  830  are together rotatable about the longitudinal axis  801  by the LP shaft  824 . The disk  830  is covered by rotatable front hub  832  aerodynamically contoured to promote an airflow through the plurality of fan blades  828 . Further, an annular fan casing or outer nacelle  834  is provided, circumferentially surrounding the fan  826  and/or at least a portion of the turbomachine  804 . The nacelle  834  is supported relative to the turbomachine  804  by a plurality of circumferentially-spaced outlet guide vanes  836 . A downstream section  838  of the nacelle  834  extends over an outer portion of the turbomachine  804  so as to define a bypass airflow passage  840  therebetween. 
     Referring still to  FIG. 8 , the turbofan engine  800  additionally includes a fuel delivery system  842 . The fuel delivery system  842  generally includes a fuel source  844 , such as a fuel tank, and one or more fuel lines  846 . The one or more fuel lines  846  provide a fuel flow through the fuel delivery system  842  to the combustion section  814  of the turbomachine  804  of the turbofan engine  800 . The fuel delivery system may include one or more controllable components  112 , such as a fuel valve or an actuator or servo-actuator coupled to a fuel valve. One or more sensors  212  may be operable coupled, respectively, to the one or more controllable components  112 . The one or more controllable components  112  may be controlled using a distributed control module  104 , which may be communicatively coupled to a distributed control system  100 . The one or more sensors  212  may be communicatively coupled to the distributed control module  104 , for example, so as to provide a closed-loop control regime. Alternatively, the distributed control module  104  may provide an open-loop control regime. 
     It will be appreciated that the exemplary turbofan engine  800  depicted in  FIG. 8  is provided by way of example only. In other exemplary embodiments, any other suitable engine may be utilized with aspects of the present disclosure. For example, in other embodiments, the engine may be any other suitable gas turbine engine, such as a turboshaft engine, turboprop engine, turbojet engine, etc. In such a manner, it will further be appreciated that in other embodiments the gas turbine engine may have any other suitable configuration, such as any other suitable number or arrangement of shafts, compressors, turbines, fans, etc. Further, still, in alternative embodiments, aspects of the present disclosure may be incorporated into, or otherwise utilized with, any other suitable type of gas turbine engine, such as an industrial gas turbine engine incorporated into a power generation system, a nautical gas turbine engine, etc. any other type of engine, such as reciprocating engines. 
     Further, although not depicted herein, in other embodiments an exemplary engine  800  may include any number of distributed control modules  104  configured to control various controllable components  112  of the engine  800 , including variable-geometry components include variable-position fan blades, variable-position guide vanes, variable-position compressor blades, and variable-position turbine blades. Such distributed control modules  104  may be part of a single distributed control system  100  or part of a plurality of distributed control systems  100 . 
     An exemplary distributed control system  100  may include a main processing unit  102 , a distributed control module  104 , and a controllable component  112 . The distributed control module  104  may be configured according to the present disclosure, for example, to receive a nominal command reference  404 , such as from the main processing unit  102 ; to determine a series of cumulating command references  406 , for example, based at least in part on the nominal command reference  404 ; and to determine a series of cumulating control commands  604  based at least in part on the series of cumulating command references  406 . The distributed control module  104  may additionally be configured to output the series of cumulating control commands  604  to a controllable component  112 . 
     In some embodiments, an exemplary distributed control system  100  may additionally include a sensor  212  configured to measure a system variable of the controllable component  112 . For example, the sensor  212  may include a position sensor configured to measure a position of an actuator or servo-actuator. The distributed control module  104  may be configured to receive sensor feedback from the sensor  212 , and to use the sensor feedback in a closed-loop control regime that includes the series of cumulating control commands  604 . Additionally, or in the alternative, the distributed control module  104  may be configured to provide an open-loop control regime. 
     The distributed control system  100  may include any suitable controllable components  112 . An exemplary controllable component  112  may include an actuator or a servo-actuator, which may be coupled to a variable-geometry component. By way of example, a variable-geometry component may include a fuel valve, a variable-position fan blade, a variable-position guide vane, a variable-position compressor blade, or a variable-position turbine blade. 
     Aspects of the present disclosure may also be implemented in computer readable medium. Exemplary computer readable medium may include computer-executable instructions  310  configured according to the present disclosure. For example, computer-executable instructions  310 , when executed by one or more processors  306  of a distributed control module  104 , may cause the distributed control module  104  to: receive a nominal command reference  404  from a main processing unit  102 ; determine a series of cumulating command references  406  based at least in part on the nominal command reference  404 ; and determine a series of cumulating control commands  604  based at least in part on the series of cumulating command references  406 . Exemplary computer-executable instructions  310  may additionally be configured to cause the distributed control module  104  to output the series of cumulating control commands  604  to a controllable component  112 . Exemplary computer readable medium may be incorporated into or utilized with a FADEC system or an ECU, such as for a turbomachine or turbofan engine  800  and/or an aircraft. 
     This written description uses exemplary embodiments to describe the presently disclosed subject matter, including the best mode, and also to enable any person skilled in the art to practice such subject matter, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the presently disclosed subject matter is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.