Patent ID: 12252993

System100acan be used in vehicles where a gas turbine is interfaced with an electrical power system. Such systems may extract power from the gas turbine engine to generate electric power to feed, for example, electric propulsors. The power system may also be used to augment the engine's thrust production.FIG.1Ashows system100aconsisting of two spools, each consisting of a compressor and a turbine mechanically connected to an electric machine. The low-pressure spool consists of low-pressure compressor (LPC)102a, low pressure turbine (LPT)102b, and electric machine103a. The high-pressure spool consists of high-pressure compressor (HPC)101a, high pressure turbine (HPT)101b, and electric machine103b. The electric machines103aand103bare each mechanically powered from their respective shaft. The electrical power system may be used to stabilize functioning of fluid actuators in system100a.

System100afunctions as a gas turbine where at least a portion of the propulsive power is converted to electrical power. System100aincludes two shafts enabling each to rotate at different speeds. System100aincludes high pressure components HPC101aand HPT101b. The HPC101aprovides high pressure fluid (e.g., air) to the HPT101bso that the latter can function at a different speed than LPT102b. System100aalso includes a low-pressure compressor (LPC)102aand a LPT102b.

The LPC102afeeds fluid to the HPC101a. The system100acreates propulsive fluid power by combining high pressure flow with combustor output at COMB104. Both turbines HPT101band LPT102bconvert fluid power to mechanical shaft power. The electric machines103aand103bare considered to be generators and each may convert mechanical shaft power to electric power for the purpose of supplying a power grid connected to electrical loads. Both electric machines103aand103bare controlled by electronics105. Electronics105may include control systems, power electronics, and power transmission hardware, as well as various computer systems.

In a typical configuration, electric machines103aand103bmay provide power to one electric machine EM_P106. EM_P106may interface with the system100athrough a power grid that includes machines103aand103b. Under this configuration, however, EM_P106is coupled to the HPT101band LPT102b, and subject to varying loads. Because EM_P106may be subject to varying power supply and demand, the fluid actuators (101a,101b,102a, and102b) and any propulsor connected to EM_P106may be subjected to vagaries and transients related to a stiff power supply that is challenging to manage with precision. If instabilities manifest and propagate, this can cause damaging and/or catastrophic circumstances for the operation of the actuators. Instabilities in power supply can potentially cause a loss of vehicle thrust, for example.

Other instabilities can lead to similar problems in operation of system100a. For example, variations in fluid flow and pressure in compressors, fans, or pumps can lead to undesirable erratic operation. Stall or surge of these components can lead to sudden and, potentially, catastrophic loss of thrust due to undesired blocked/choked flow, loss of pressure rise, and inability to sustain combustion. Mismatches in compressor rotational speed and fluid flow can results in higher than desired loading, typically associated with a low fluid flow rate for a given pressure ratio across the component. In the gas path, this can manifest as significant off-incidence flow impinging on the compressor blades. If severe enough, stall or surge can occur. Moreover, mechanical components in system100a, and other systems designed for acculturating fluid (e.g., those for ventilation or climate control) generally have precision designs with relatively small tolerances. Since systems100atend to operate at high temperatures, and experience large swings in temperature, thermal expansion or contraction of components can impact flow paths subject to those relatively small tolerances. Restriction or expansion of flow can cause pressure changes similar to those described above, with similar consequences on compressor functioning. Where different materials are used for different components, differences in thermal expansion of the different materials can exacerbate the issue.

Because of this potential for operational variation, and the need to maintain operational stability, designs of propulsors and other fluid actuating systems tend to include a “stability margin.” This is a designed-in ability to accommodate a window of operating conditions at near optimal or high performance. The stability margin can account and compensate for maintaining performance while the system experiences a change in operating point and distortion (e.g., a deviation of the fluid flow from ideal uniform expectations). Including a stability margin in a design can improve safe operation and can prevent shut down. However, building in too much operational tolerance and safety sacrifices engine performance. Therefore, a way to reduce the required stability margin without adversely impacting safety improves efficiency and performance is desired.

FIG.1Brepresents this stability margin concept schematically in the context of a hypothetical system that can actively adjust or control fluid actuator operation to prevent stall.FIG.1Bis reproduced in large part from Strazisar, Anthony J., Michelle M. Bright, Scott Thorp, Dennis E. Culley, and Kenneth L. Suder. “Compressor stall control through endwall recirculation.” In Turbo Expo: Power for Land, Sea, and Air, vol. 41707, pp. 655-667. 2004. More specifically, the plot100binFIG.1Bshows a region stabilized with active flow control110on a plot100bof pressure rise vs. mass flow through a propulsor system. Pressure rise is the pressure on the fluid actuator itself, output pressure minus input pressure. Mass flow measures the flow of fluid through the actuator. A stall line with control120forms the left boundary of the region stabilized with active control110, indicating a region where the propulsor systems would stall without active engine flow control. Stalling indicates loss of thrust provided by a propulsor and high stresses on the fluid actuator. Forming the right boundary of region110is a stall line without control130. This indicates the region where the propulsor system may stall even with engine control. The constant speed line140represented inFIG.1B, represents how the mass flow varies with pressure rise at a constant fluid actuator speed. This is typically accomplished by changing the exit pressure through a valve far downstream. In operation, distortion and transient events can have the fluid actuator run inadvertently near a stall boundary so one operated to the right of that boundary. When a stabilizing system operates, it can move the operating point of the propulsor system from the operating point without control150, located within one of the stall regions, to the actively stabilized operating point160within the region stabilized with active control110. As shown inFIG.1B, this action represents a performance improvement170for the propulsor system. In addition, there is typically an efficiency improvement.

Known fluid actuator systems typically trade-off response time to maintain stability margin in this way to maintain high stability110. Other than the aforementioned designed-in stability margin and traditional control through the limiting of control inputs the determine system responsiveness, there is currently no other method to reduce the resulting transient from the above-mentioned operating point instabilities. Yet these approaches have multiple disadvantages. For one, large stability margins must be included in the system design. The size of the stability margin correlates to the ability to correct or adjust operation of the actuator according to changes in conditions. Specifically, if the ability to adjust operation of the actuator is limited, the stability margin will have to be relatively large. Second, variable geometry such as Variable Bleed Valves (VBV)s and Variable Stator Vanes (VSV)s are typically utilized to keep the components at points which are stable. This can add weight and cost. It can also reduce efficiency. Third, known systems to actively control fluid actuator stability are limited by the speed at which they operate and provide mitigation. Often conditions in the system can change faster than the control system can respond. This can result in stall or other problems despite efforts to actively control these systems with the traditional suite of actuators.

SUMMARY

Given the above, there is an unmet need to provide a stabilization for fluid actuator systems. There is a further unmet need to provide stabilization or corrective measures on a time scale sufficient to increase the operating efficiency of the fluid actuator systems.

In particular, corrective systems need to respond on time scales that are at least as fast as changes in fluid flow in the actuator system that might cause destabilization. Doing so will, amongst other things, decrease stability margins that need to be designed into these systems. The time scale of these changes can be on order of 10 μs for fluid flow, greater for changes due to mechanical reasons (e.g., changes in engine shaft speed and thermal expansion of component of the system). There is an unmet need for active control systems that can respond to and mitigate changes in fluid flow on this time scale.

One of the limiting features in the response time of any electrical motor is the timescale for delivery of power and/or the uptake of excess power by a local power source powering the motor. Conventional battery systems, e.g., lithium-ion battery systems, have power charging response times that can absorb power on time scales on the order of 100 ms. Therefore, control systems that can respond faster, on order of changes in mechanical operation of turbines or changes in fluid flow conditions, would be advantageous. In addition, improved capacity to store and deliver energy generally results in an increase in weight, which can be detrimental to propulsion systems utilized in aircraft. Systems that can deliver increased power without a corresponding weight increase are desirable.

Supercapacitors allow for very fast discharge (about 600 times that of a lithium-ion battery) and storage of energy that can change the torque and speed (rpm) of an electric motor. In addition, supercapacitors are relatively light weight. If an electric motor is attached directly or through a drive train to a fluid actuator (fan, compressor, pump, etc.), stall can be avoided when precursors to stall are detected with instrumentation. The propulsor could be in a tail cone thruster, distributed propulsion or as part of an Urban Mobility Vehicle, for example. A feedback control system combined with a power control device is used to prevent an undesirable fluid flow condition. For these and other reasons, the present disclosure introduces systems providing active control, based in part, on power provided by fast response energy storage systems including supercapacitors.

Other systems that can provide and store power quickly include flywheels. Flywheels have high power density and have also been called Kinetic Energy Recovery Systems (KERS) and have been used in automotive and space application. In propulsion system with multiple rotating components, power management control can be utilized to shift power between components as needed, essentially treating the other component(s) in the system like flywheels. Batteries could be applicable if they are relatively large. That could be the case in hybrid electric aircraft applications where large amounts of energy storage are present to augment thrust.

More specifically, disclosed herein is a system for actuating fluid flow. The system includes a fluid actuator, an electric motor for driving the fluid actuator, a motor controller for controlling the motor, a local energy storage device for powering the motor, a stability monitor that assesses instability of operation of the fluid actuator, and a mitigation control that mitigates instability of the fluid actuator via the motor controller based on the assessment of the stability monitor, wherein a response time of the mitigation is faster than changes in fluid flow in the system during fluid actuation.

The disclosure also includes a method for actuating fluid flow. The method includes actuating the fluid via a fluid actuator, driving the fluid actuator via an electric motor, controlling the electric motor via a motor controller, powering the electric motor via a local energy storage device, assessing stability of operation of the fluid actuator, and mitigating stability of the fluid actuator based on the assessment, wherein a response time of the mitigation is faster than changes in fluid flow in the system during fluid actuation.

BRIEF DESCRIPTION OF DRAWINGS

FIG.1Ashows a schematic of an exemplary engine design with dual electric engine control of compressors and turbines that may be subject to instabilities in fluid flow;

FIG.1Bis a schematic representation of a stability margin in the design of fluid actuating systems like system100a;

FIG.1Cis a schematic showing potential effect of a mitigation system to correct for operational uncertainty and instability in a fluid actuator system;

FIG.2Ashows an exemplary fluid actuation system200including instability mitigation that may be used in the context of the present disclosure;

FIG.2Bshows an exemplary vehicle that may use a fluid actuator like system200according to aspects of the present disclosure;

FIG.3shows an exemplary sensor setup300on a fluid actuator that may inform the stability monitor250a;

FIG.4Ashows an exemplary method400to implement the exemplary fluid actuation system200shown inFIG.2A;

FIG.4BcontinuesFIG.4A; and

FIG.5shows a method500that maintains actuation in system200according to method400.

DETAILED DESCRIPTION

Overview

As discussed above, the following describes a control system for, among other things, overcoming uncertainty in design and operation of the fluid actuator systems. For the best results, a fast response actuator system (e.g., quick change of rpm to prevent a disruption in pressure and mechanical unsteadiness) is advantageous. As also discussed above, faster response time can be provided by a stabilization system that includes an improved method of power delivery (e.g., including a supercapacitor or other fast acting energy storage device) over conventional systems. Such faster response could better address uncertainties created by variances in operation and operating condition of the fluid actuator system. The sum of such variances will be referred to herein as the “transient stack.” Stability control and mitigation can allow relatively small stability margin even when uncertainties from multiple sources add up to a large transient stack. For a typical fluid actuator system (e.g., having a fan, compressor, and propulsor) less stall margin needed could mean a higher loaded compressor with fewer stages, higher efficiency, or extra thrust/actuation capability.

FIG.1Cis a schematic showing potential effect of a mitigation system to correct for operational uncertainty and instability in a fluid actuator system. The plot100cis roughly comparable to the plot100binFIG.1B, except that it shows the cumulative effect of both uncertainties in operation (“uncertainty stack”) and transients (“transient stack”).FIG.1Cshows an “operating line,” which represents a region in which the actuator system can operates as intended without substantial stall or surge. Implicit in the operating line is a concept called “stall margin,” which is defined as a parameter that estimates how close the compressor of the system is to stall. The stall margin accounts for transient flow through the system. Here, stall margin represents the quality of flow condition in the gas flow path within the actuator system.FIG.1Cshows how mismatches in pressure relative to flow through gas path in the system, so-called off-nominal conditions, threaten overall actuator stability. The “transient stack” is needed because the acceleration and deceleration of a shaft changes the point of operation. Also on this plot are contours of constant efficiency. Efficiency of a fluid actuator could be increased if a higher stall margin is available through active control. In principle, one can design a mitigation system that can provide feedback and selective power to the actuator system to ensure operation close to the operating line. The system should be responsive to precursors that may be indicative of imminent stall or surge.

Such precursors (e.g., excessive turbulence in fluid flow, spike in power draw, etc.) can be directly monitored by a control system. Precursor sensing devices, for example, may include high response pressure transducers or power electronics attached to the actuator. Detected rapid power changes and/or actuator speed changes could mean stall is imminent. In addition, issues caused by thermal expansion of certain components, particularly those having small radii with high clearance can be detected by sensors either embedded in the casing and/or actuator. Expansion due to rpm changes in actuator/rotor operation can be rapid, sometimes nearly instantaneous. More generally, the time between the precursor and change in actuator functioning (e.g., stall) can be very short, e.g., on order of ms or less. Therefore, it is advantageous to sense these precursors in real time using sensors deployed in the actuator system. Disclosed systems herein may detect certain stall precursors up to 2000 actuator/rotor revolutions ahead of stall. This may allow sufficient time for mitigation depending on the particulars of the mitigation/control system.

To mitigate imminent stall that may follow a sensor indicating a rapid decrease in gas flow pressure (or other pressure fluctuations, speed or motor torque/current unsteadiness, for example) through the system and to the actuator, the control system can rapidly increase rotations per minute of the actuator. This rapid increase in rpm can avoid stabilize the compression system, for example. Generally, an increase in actuator speed/rpm may prevent the actuator system from exceeding stress limits of the system at lower pressure. In multi-spool engines (e.g.,100a), deceleration of one of the motor shafts driving the actuators that is not near stall can also be effectuated rapidly. Torque can be applied selectively between the connecting shafts by an additional electric control beyond the primary drive. In principle, all these can be mitigated to prevent stall by a control system. However, mitigation effectiveness depends on the speed at which power can be supplied to the system (e.g., to increase rpm, in the example). This problem can be particularly difficult since the momentum/inertia of the actuator can cause its speed of rotation to lag behind abrupt changes in the flow of gas. This momentum should be dealt with by the control system adding or subtracting power to the system.

As discussed above, power supplied in control system via traditional batteries or other energy storage systems have power supply limitations regarding the time scale over which they can apply power. Adding fast response energy storage (e.g., one or more supercapacitors and/or a flywheel) as part or all of the energy storage and power delivery system can enable more rapid changes in rpm and power. In particular, supercapacitors can also source/sink energy very rapidly, unlike typical batteries that have a limited ability to absorb energy. The fast response energy storage can provide more greater ability to quickly absorb and add power. As disclosed herein, fluid actuation systems connected to electric motors/generators can benefit from the use of fast response energy storage in engine control systems.

Exemplary Fluid Actuation System200

FIG.2Ashows an exemplary fluid actuation system200that may be used in the context of the present disclosure. In system200, a rotor205provides fluid flow for an application. Applications for the provided fluid flow can include, for example, providing propulsion either to an aircraft or a seacraft (e.g., a jet ski, ferry, or submarine).FIG.2Bshows an exemplary vehicle260, NASA's Subsonic Single After Engine (SUSAN) transport aircraft with wing-mounted electrical propulsors. Vehicle260may use fluid actuation according to aspects of the present disclosure, in particular those shown inFIG.2A. Other applications can use fluid flow for reasons other than propelling a vehicle. These include circulated gas or other fluid in, for example, a ventilation control system (e.g., a system for maintaining airflow through a vehicle or building). Still others include climate control systems, computer cooling fans, pumps in industrial applications, or other systems that have compressors, fans, or pumps driven by electric motors.

As shown inFIG.2A, a fluid actuator system may include a rotor205and stator210. The rotor205and other components of system200may be driven or controlled by the same intelligent actuator system220. In the exemplary configuration, gas flow is in the direction F shown in the figure, i.e., so the flow encounters rotor205prior to stator210. Blades205band205con the rotor205propel flow along axis AR and create rotational flow around axis AR. Blades on stator210(e.g., blade210a) can channel the flow actuated by rotor205so as to minimize rotational flow around axis AR and convert energy from rotational into axial momentum along AR. Blades210amay form an Outlet Guide Vane (OGV), for example, or an Exit Guide Vanes (EGV).

AlthoughFIG.2Ashows a rotor205/stator210configuration that may be used in the context of the present disclosure, it is to be understood that this configuration is merely exemplary. Any of the fluid actuation systems discussed herein may be used in place of rotor205/stator210in conjunction with system200. For example, actuating components in system100a(e.g., HPC101a, HPT101b, LPC102a, and LPT102b) can be used in conjunction with system200. In general, any suitable compressor, fan, pump, or other fluid actuator system may be used in conjunction with system200. It is to be understood that system200illustrates mitigation, actuation, power, and control systems that can be applied generally to fluid actuation systems used in applications as diverse as propulsion, ventilation, and climate control, as well as other applications.

As shown inFIG.2A, the intelligent actuator system220may include a dedicated motor control225, analogous to electronics105inFIG.1A. The motor control225may drive a motor or motors that drive the rotor205. More specifically, the motor control225may provide power to rotor205and/or any other active components in the fluid actuation system200. Motor control225may provide power independently to these components. Typically, it is advantageous to provide differing amounts of power to different components to allow them to act independently.

Motor control225may draw power from a local energy storage device230. Motor control225may also draw power from electric power source235. Electric power source235may be a system-wide power source that, for example, provides power to other portions of a vehicle (not shown) using the fluid actuation system200to provide thrust. In some ways, electric power source can operate in an analogous manner to EM_P106inFIG.1A. In contrast, energy storage device230is generally a local power system dedicated to the intelligent actuator system220. Energy storage device230may draw power from electric power source235periodically, continuously, or in other ways. Electrical storage device230may draw said power to power a number of suitable energy storage devices. Electrical storage device230may then provide power to the rotor205according to the motor control225. Providing power locally via device230, as opposed to via global source235, protects rotor205(and any other fluid actuator that may be used in conjunction with system200) from sudden changes in loading and power that can introduce catastrophic instability in these components, as described in the context ofFIG.1A.

Electrical storage device230may include a number of energy storage mechanisms, including supercapacitors and batteries. Inclusion of supercapacitors, in particular, in storage device230may allow power delivery to motor(s) driving rotor205on a very quick time scale, e.g., providing at least the amount of power to overcome system inertia and losses during momentary accelerations and decelerations where energy is sourced discharge rate requirements will be subject to the application. In general, any suitable type of energy storage device may be used in device230that can provide power to rotor205on a time scale appropriate to address changes in operating conditions described in the context of the stability monitor240. This includes both power supply and acquiring and storing excess power that may be unused or produced by the rotor205.

Suitable energy storage mechanisms in device230include various types of supercapacitors, devices with capacitance often six orders of magnitude larger than conventional capacitors but with limited voltage capability. Typically, the elements are connected in various series and parallel configurations to meet voltage and energy requirements, much like the elements used in hybrid automotive applications. Supercapacitors that may be used are sometimes called ultracapacitors. They include those use electrostatic double-layer capacitance, e.g., electrostatic double-layer capacitors (EDLCs), and electrochemical pseudocapacitance. Suitable capacitors may include those using carbon electrodes with charge separation on order of angstroms. Suitable capacitors include electrochemical capacitors with metal oxide and/or conductive polymer electrodes. In addition, hybrid capacitors (e.g., lithium-ion capacitors) may be used. Hybrid capacitors may include an electrode exhibiting mostly electrostatic capacitance and another exhibiting mostly electrochemical capacitance, for example.

Other suitable components that may be included in device230include any suitable type of battery, such lithium-ion batteries. Others include alkaline and nickel metal hydride (NIMH) batteries. Device230may further include a fuel cell. For example, one type of fuel cell that may be included in device230is a polymer electrolyte membrane (PEM) fuel cells, solid oxide fuel cells, direct methanol fuel cells, alkaline fuel cells, phosphoric acid fuel cells, carbonate fuel cells, and other suitable types of fuel cells. Still others include other methods of energy storage.

Still others include other methods of energy storage. One such example is a flywheel, where a mass in the form of a disk or wheel rotating about its axis at relatively high speed is used to store kinetic energy. Another example is superconducting magnetic energy storage where electrical current circulating in a lossless circuit at cryogenic temperatures is used to store electrical energy. Both methods require additional equipment and electronics to add or remove energy from the energy storage device.

One purpose of device230is to store power from source235such that rotor205and other active components can be isolated from source235since power source235may be subject to instabilities. For example, if the intelligent actuator system220is part of a vehicle, source235would provide power to other parts of the vehicle. These other parts could include any system drive or computing system mounted to operate the vehicle. Other components could include lighting systems, ventilation systems, environmental systems, communication systems, etc. If source235is mounted in an extra-terrestrial vehicle, for example, the other components powered via source235may include systems for environment or pressure maintenance, or any of the other systems discussed above. In any event, regardless of the additional systems powered by source235, the load created by these systems will burden source235. The burden may cause surges or decreased power. Such intermittences could perturb the rotor205if either one is fed directly from source235. Therefore, local device230can improve performance and smoothness of operation of the intelligent actuator system220.

In addition to external source235, the system may also include an external actuation control240external to the system220. External actuation control240can include, for example, a vehicle thrust control that can, via local actuation control245and motor control275, control rotor205sufficiently to provide thrust to the vehicle. Alternatively, in the case that system220provides actuation for a purpose other than providing thrust to a vehicle, control240may actuate that function. For example, in the case that system200provides ventilation to an interior space, actuation control240may control rotor205to provide the ventilation. In either case, actuation control240would be subject to external input to control aspects of the system200.

System220further includes local actuation control245that can interact with motor control225, and the stability control250. More specifically, local actuation control245translates thrust or actuation requests from the external actuation control240and mitigates them according to the input from the stability control250. Local actuation control245then commands the motor control225accordingly to create the desired thrust or actuation by selectively powering rotor205.

Stability Control250includes the methods of detecting instabilities in system220and mitigating those instabilities by providing dynamic perturbations of the local actuation control245.

As discussed above, the stability control250can interact with the local actuation control245primarily to provide the local activation control245with stability mitigation information. Therefore, one purpose of the stability control250is to ascertain information regarding the stability of operation of the rotor205. More specifically, the stability monitor250aof the stability control250assesses whether or not operation of the rotor205show instability in operation (e.g., pressure or current instability). Such instabilities may arise due to separation of fluid flow within the fluid actuation device. Changes in dynamic pressure measurements or aerodynamic loading as reflected in current measurement of the motor controller are examples of potential indications of instabilities.

FIG.3shows an exemplary sensor setup300that may inform the stability monitor250a. In particular,FIG.3shows arrays of circumferential sensors310mounted along the circumference of rotor205and its casing305. The circumferential sensors310can, for example, monitor local instability in pressure applied by the rotor205. Coordinating instabilities measured by the circumferential sensors310with their location can provide spatially resolved instability information for the stability monitor250a. Similarly, arrays of axial sensors320can measure pressure instabilities and or power distribution along the rotation axis AR of the rotor205. It is to be understood that, whileFIG.3shows only circumferential310and axial320sensors, any suitable type of sensor or configuration can be used to measure stability (or instability) of operation of the rotor205and fluid flow through casing305or other parts of system200. Moreover, whileFIG.3shows sensors310and320mounted to rotor205, stator210, and casing305, it is to be understood that sensors310and320may be mounted on other components. In particular, sensors310and320may be mounted on any components of system200where fluid flow instabilities and/or other instabilities related to providing power may arise.

Stability monitor250aobtains information from sensors related to the rotor205and/or stator210(e.g., sensors310and/or320). Stability monitor250amay then process the sensor information to, for example, detect and locate (spatially, or within wiring or within detector array) any issues or instability. Other types of processing are possible. For example, stability monitor250amay determine suggested mitigation steps based on any detected instabilities. If no instabilities are detected, stability monitor250amay then determine a stable condition. Subsequent to analyzing the stability sensor data, the stability monitor250athen forwards the information regarding instabilities to the mitigation control system250bportion of the stability control system250.

The mitigation control250bthen receives the processed stability data from the stability monitor250a. The mitigation control250bdetermines mitigation actions based on the stability data. For example, if the stability data indicates that one of the circumferential sensors310indicates a sudden drop in pressure or senses pressure signatures indicative of approaching stall/surge, the mitigation control250bmay prescribe, as a mitigation action, to change the rotor205speed. Such changes may initiate a rapid change in the rpm of the rotor205, for example, to offset pressure changes indicative of instabilities. The mitigation control250bmay follow a similar protocol with respect to any instabilities detected via one or more of the array of axial sensors320. In each case, where the mitigation control250breceives information concerning an instability, the mitigation control250bcan decide 1) if the instability is of sufficient magnitude to require correction and 2) what the appropriate correction should be.

As discussed above, the mitigation control250band the external actual control240provide actuation control and mitigation control, respectively, to the local actuation control245. The local actuation control245then translates this information into commands for the motor control225to operate the rotor205. As discussed above, mitigation actions may result in performance improvements in the overall system (e.g., performance improvement170shown inFIG.1A).

Exemplary Implementation400

FIGS.4A and4Bshow an exemplary implementation400of the exemplary fluid actuation system200shown inFIG.2A.FIGS.4A and4Bdescribe steady state of actuation system200(e.g., excluding system startup or shut down). Shutting down or starting up system200can be done by conventional means.

Turning toFIG.4A, in step402, system200is assumed to be actuating fluid in a steady state. This can correspond to, for example, a vehicle undergoing propulsion (e.g., an aircraft in flight) or a ventilation system in full operation (e.g., ventilating an interior space). In this step, local actuation control245has sent instructions to motor control225for operating rotor205. The instructions can combine a request from the external actuation control240(e.g., for a specific amount of thrust in the case that system200is operating a vehicle) and mitigation information from mitigation control250b. Given the importance to maintain operability of the fluid actuation device, the controller may limit the operation of the device as commanded by external actuation control240or leverage the use of other actuators in the fluid actuation system to achieve both goals in a coordinated manner.

Note that assuming the system200is actuating fluid in a steady state in step402does not mean that system200must be actuating fluid in a steady state. Rather, this assumption simply provides a starting point for analysis of the stability of fluid flow and propulsion so that any detected deviations from stability can be diagnosed and mitigated. Included in step402is actuation of rotor205to move fluid. Actuation may be requested by the external actuation control240and implemented by the local actuation control245. As discussed above, the local actuation control245may use a combination of information from the stability control system250and the external actuation control240. The actuation may be, as described above, implemented via the motor control225using power provided by the energy storage device230.

At step404, the stability control system250performs an initial check on the gathered sensor information provided by the stability monitor250a. In this step, stability monitor250ainquires a series of sensors (e.g., sensors310and/or320shown inFIG.3) to monitor pressure differences, expected or not, and other variables such as electrical current and power provided in the rotor205and other components. Any measured pressure differences may relate directly to mechanical loading on rotor205, stator210, or other components. The stability information gathered from the sensors by system250in this step may also, or alternatively, relate to current or power usage by various portions of the rotor205or other components. The latter may indirectly relate to mechanical loading on the rotor205in the sense that drawing more or less power than expected may be indicative of an unexpected change in mechanical loading. In these and other ways, the stability information gathered by system250, and specifically stability monitor250a, provides insight into the stability of mechanical loading on the rotor205. As discussed above, any instabilities may be caused by pressure changes and/or unexpected aerodynamic forces.

At step406, the stability control system250evaluates the stability information to, among other things, determine whether the rotor205is operating under stable conditions. For example, if the sensors310/320sense rapid changes in pressure or power provided to different portions of the rotor205(or other components), rotor205may be operating under unstable conditions.

In this step, the stability monitor may, for example, compare the latest sensor data with previously acquired and stored sensor data to detect changes in operation. In particular, the rate of such changes may be ascertained. If, for example, a rapid pressure drop is detected at this step, the stability monitor250amay flag this as an indication of imminent stall. Stability monitor250amay further indicate that the detected drop in pressure may be a candidate for mitigation and provide a recommended time frame for mitigation (e.g., during the next cycle of the stability monitor, over the next few milliseconds, or over another set time period, which could, for example, relate to the rate of detected change in pressure). Similar determinations can be made by analyzing other data (either instantaneous or time resolved) from the sensors, for example power distribution and/or current. In this case, rapid changes in this data can be used to deduce stall conditions.

Any suitable algorithm at this step may be employed to analyze the sensor data. Examples of suitable algorithms include least squares analysis, other statistical analysis, and machine learning algorithms. Suitable machine learning algorithms may include one or more of the following: an artificial neutral network (ANN), a deep neural network (DNN), a recurrent neural network (RNN), a long short-term memory (LSTM) RNN, or a convolutional neural network (CNN), and a graphical neural network (GNN). The machine learning algorithm may also be or include a support vector machine (SVM), a Bayesian classifier, or other suitable classifier. The machine learning algorithm may be or include a decision tree or a random forest.

At step408, the stability control system250considers potential mitigation steps based on based on analysis of sensor data in step406. More particularly, the mitigation control250bmay perform an analysis of the sensor data and/or any analysis or recommendations provided to it by the stability monitor250a. This step may include similar analysis as that discussed above in the context of step406. Any of the algorithms or analytical routines discussed above in the context of step406may also be used in the context of step408.

In step408, the mitigation control250bmay identify a particular mediation step. Such steps can include, for example, applying more power to the rotor205in response to detected pressure drop. As discussed above, this selective application of power can prevent a stall or surge in the rotor205operation according to, for example, the response dynamic shown inFIG.1C. Other mitigation steps can include decreasing power applied or supplied to the rotor205. This can also mitigate, for example, a power surge associated with a sudden increase in pressure causing the rotor205to revolve without using 100% of the applied power. Still other steps may include actively removing excess power from the motor control225, rotor205or other components. Excess power in the rotor205may be facilitated by a supercapacitor, or other similar device, included in device230. Supercapacitors, in particular and unlike most batteries, can quicky intake and store excess power. The stored excess power can be used, for example, in further mitigation steps and/or powering the rotor205in steady state (e.g., as in step402). Here power applied may also be “dithered” (e.g., by imposing periodic fluctuations of power/torque with a frequency and magnitude chose to, for example, counteract instabilities).

In certain instances, the mitigation control250bmay decide not to perform a mitigation step. This could happen when, for example, the condition to be mitigated, as detected by the stability monitor250ain step406, is not severe enough to warrant intervention. In some cases, the mitigation contemplated by the mitigation control250bmay be counterproductive given other tradeoffs in the system. For example, increasing power to the rotor205at the expense of other components may, in some cases, cause the system to stall. The mitigation control250bcan, in certain cases, weight the propensity of an adverse effect arising from the mitigation against the adverse effect it seeks to mitigate. This analysis may take into account the evolution of the condition (e.g., a pressure drop) over time. In other instances, there may be the potential for the potential problem to self-correct without active mitigation by the system250. In those cases, the mitigation control250bshould weigh the cost of mitigation against the probability of self-correction before deciding to mitigate. The mitigation control250bmay also evaluate the degree to which any detected condition is merely transient and will dissipate on its own quickly enough to prevent adverse effects on system200.

In deciding mitigation steps, mitigation control250bmay take into account what power may be available to the system220and from which source. For example, if the energy storage device230has sufficient power available in a fast-discharging device, e.g., one or more of the supercapacitors or flywheels mentioned above, the control250bmay elect to perform mitigation steps requiring such a quick response. If, on the other hand, a certain mitigation response calls for delivery of a quantity of power on a time scale that the device230cannot provide at the required time, the control250bmay elect to forgo the mitigation. In this and other ways, the control250bmay select among possible mitigations based on the amount of power stored in device230, how that power is stored (e.g., on which storage device), and how it can be delivered.

Each of the above-described determinations may be facilitated by training a machine learning algorithm to make mitigation decisions, including any algorithm described in the context of step406above. The training may be, for example, based on actual data collected from a system like system200inFIG.2A. The training may also be facilitated by simulation or calculation, e.g., simulated data may be used to train the machine learning algorithm. Any suitable training algorithm may be used, including those used to train any model or algorithm described herein.

Turning toFIG.4B, in step410, the stability control system250provides the proposed mitigation steps to the local actuation control245. In this step, the local actuation control245may also receive requested actuation from the external actuation control240. In step412, the local actuation control245then generates commands for the motor control225to implement the received mitigation steps, the requested actuation, or both. In this step, the local actuation control245may decide on specific implementation of the proposed mitigation, for example, by using certain aspects of the energy storage device230to power the motor control225. The local actuation control245may further decide on the timing of mitigation and/or actuation and set a protocol for mitigation. In order to perform this analysis, the local actuation control245may rely upon any algorithm described herein, including the machine learning algorithms described in the context of step406.

In step414, the motor control receives commands generated in step412. These commands include any mitigation steps and actuation requests. In step416, the motor control225implements the commends by, among other things, powering the motor driving the rotor205and/or the compressor310by sending power from the energy storage device230according to the commands.

Continuous or Near Continuous Cycling Method500

FIG.5shows a method500that maintains actuation in system200according to method400. More particularly, method500can iterate method400as long as system200seeks to maintain substantially continuous fluid actuation (e.g., propulsion). The continuous actuation state can be indicative of, for example, maintaining thrust in a vehicle (e.g., an aircraft). It can also be indicative of maintaining other conditions, such as consistent ventilation in a ventilation or climate control system.

In step502, system200is engaged. Engagement could be, for example, powering up system200. It could also represent engaging the rotor205of system200in operating status (e.g., to provide thrust or other fluid actuation).

In step504, system200achieves an operational state. This generally denotes overcoming transients associated with engaging the system in step502. Such transients could result from, for example, ramping rotor205up from zero angular velocity to an angular velocity capable of providing thrust. Conditions for achieving the operational state defined in step504need not be fixed and can be determined by user specific for the application. It should be understood that the operational state is merely a state in which the system200is reasonably close to the conditions necessary to become operational and provide actuation of fluid flow for the purpose of system200.

In step506, the system200determines whether it should maintain a continuous actuation. In this state, the system200may be, for example, providing thrust to a vehicle. Continuous actuation would be needed such that the vehicle has propulsion. In another example, the system200would be ready to provide continuous ventilation to a climate or ventilation system. If the system200determines in step506(“YES”) that it will maintain continuous operation, it proceeds to step508. Otherwise (“NO”), it will proceed to step501.

In step508, the system performs method400. As discussed above, performing method400provides actuation via system200. Method400also provides continuous stability monitoring and mitigation in its provision of fluid actuation. Once method400is performed in step508, the system returns to step506to re-evaluate whether it should maintain continuous actuation. Therefore, the system200loops through steps506and508continuously until receives an indication it is no longer to maintain continuation actuation (“NO” in step506). In that case, the system200proceeds to step510.

In step510, the system200is determined not to maintain continuous actuation. Generally, the system (and rotor205) will then maintain an idle state. In the idle state, the system200will be able to re-engage (i.e., return to step502to provide actuation) when needed. If re-engagement is not needed, the system200may be powered down at this point.

While various inventive aspects, concepts and features of the inventions may be described and illustrated herein as embodied in combination in the exemplary embodiments, these various aspects, concepts and features may be used in many alternative embodiments, either individually or in various combinations and sub-combinations thereof. Unless expressly excluded herein all such combinations and sub-combinations are intended to be within the scope of the present inventions. Still further, while various alternative embodiments as to the various aspects, concepts and features of the inventions—such as alternative materials, structures, configurations, methods, circuits, devices and components, software, hardware, control logic, alternatives as to form, fit and function, and so on—may be described herein, such descriptions are not intended to be a complete or exhaustive list of available alternative embodiments, whether presently known or later developed. Those skilled in the art may readily adopt one or more of the inventive aspects, concepts or features into additional embodiments and uses within the scope of the present inventions even if such embodiments are not expressly disclosed herein. Additionally, even though some features, concepts or aspects of the inventions may be described herein as being a preferred arrangement or method, such description is not intended to suggest that such feature is required or necessary unless expressly so stated. Still further, exemplary or representative values and ranges may be included to assist in understanding the present disclosure, however, such values and ranges are not to be construed in a limiting sense and are intended to be critical values or ranges only if so expressly stated. Still further, exemplary or representative values and ranges may be included to assist in understanding the present disclosure, however, such values and ranges are not to be construed in a limiting sense and are intended to be critical values or ranges only if so expressly stated. Parameters identified as “approximate” or “about” a specified value are intended to include both the specified value and values within 10% of the specified value, unless expressly stated otherwise. Further, it is to be understood that the drawings accompanying the present application may, but need not, be to scale, and therefore may be understood as teaching various ratios and proportions evident in the drawings. Moreover, while various aspects, features and concepts may be expressly identified herein as being inventive or forming part of an invention, such identification is not intended to be exclusive, but rather there may be inventive aspects, concepts and features that are fully described herein without being expressly identified as such or as part of a specific invention, the inventions instead being set forth in the appended claims. Descriptions of exemplary methods or processes are not limited to inclusion of all steps as being required in all cases, nor is the order that the steps are presented to be construed as required or necessary unless expressly so stated.