Abstract:
A method of testing a component of a mobile platform without using an aircraft control system of the mobile platform, where the component forms a part of the aircraft control system. The method may involve using a test controller independent of the aircraft control system to initiate a test operation. The test operation is used to generate a test signal. The test signal is applied to a test subsystem carried on the mobile platform but operable independent of the aircraft control system. The test subsystem is used to act on the component of the aircraft control system. A response of the component may then be evaluated.

Description:
FIELD 
     The present disclosure relates to test and monitoring systems, and more particularly to a test and monitoring system for non-intrusively testing various components of a control system of a vehicle, device or apparatus. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
     Most modern aircraft have stability augmentation systems to enable fly-by-wire operation. Furthermore most, if not all, state-of-the-art high-performance military aircraft have advanced specialized control augmentation systems with selectable task-tailored control laws. Such systems enable the pilot to maneuver the aircraft to its performance limits and perform tasks such as precision tracking of targets. 
     It is extremely important that the aircraft and its subsystems, including the augmented control system, are accurately modeled to support design and performance assessment efforts. However, at the same time, most high-performance and precision flight applications are capable of generating control surface actuator performance requirements that exceed the capability of state-of-the-art actuator technology, which primarily involves electro-hydraulic actuators. 
     Performance limitations of present day electro-hydraulic and electromechanical actuators are predominantly bandwidth related. These performance limitations are typically due to size, weight, power and cost relating to such actuators. Such actuators also suffer from inherent characteristics such as high levels of backlash, hysteresis and nonlinearity due to variables such as gear heads, actuator linkages, hydraulic fluid viscosity, aging etc. Additionally, the ability to determine the health of the closed-loop actuators of the aircraft is highly important to achieving mission objectives and ensuring safe operation of the aircraft. 
     With present day systems, one specific drawback is the inability to identify a primary control surface malfunction before it can destabilize an aircraft. Another drawback is the inability to verify and validate aircraft control systems during flight. Design, verification and validation of aircraft require understanding the dynamic behavior of the aircraft and control system. This is traditionally achieved through ground vibration tests, wind tunnel tests, simulated hardware in the loop tests, and flight testing. These tests can be extremely expensive, require specialized equipment, and have limitations with respect to the feasibility of using excitation test signals that have sufficient bandwidth and that can be decoupled from the systems being measured. Existing solutions rely on the aircraft control system to generate test signals. Thus, there presently is no way to independently assess the aircraft&#39;s control system during these tests. 
     SUMMARY 
     In one aspect the present disclosure relates to a method of testing a component of a mobile platform without using an aircraft control system of the mobile platform, where the component forms a part of the aircraft control system. The method may comprise using a test controller independent of the aircraft control system to initiate a test operation. The test operation may be used to generate a test signal. The test signal may be applied to a test subsystem carried on the mobile platform but operable independent of the aircraft control system. The test subsystem may be used to act on the component of said aircraft control system. A response of the component may then be evaluated. 
     In another aspect the present disclosure relates to a method of testing a component of a mobile platform without using an on-board control system of the mobile platform. The method may comprise initiating a desired test control operation. The desired test control operation may be used to control a test signal generating subsystem independent of the on-board control system, but still present on the mobile platform, to generate a test signal. The test signal may be applied to a test subsystem carried on the mobile platform only for test purposes, and operable independently of the on-board control system of the mobile platform, the test subsystem acting on the component of the mobile platform. A response of the component of the mobile platform may be monitored to determine a performance of the component. 
     In another aspect the present disclosure relates to a system for testing a component of a mobile platform without using an on-board control system of the mobile platform. The system may comprise a controller, independent of the on-board control system, to generate a test operation. A perturbance test signal generating system, independent of the on-board control system, and responsive to the controller, may be used for generating a perturbance test signal. A test subsystem carried on the mobile platform but operable independent of the on-board control system, and being responsive to the perturbance test signal, may be used for influencing operation of the component of the mobile platform. The controller may be further adapted to evaluate a response by the component of the mobile platform. 
     Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
         FIG. 1  is a high level block diagram of a system in accordance with one embodiment of the present disclosure; 
         FIGS. 2A-2E  show various types of perturbance test signals that may be generated by the system when implementing a test operation on an existing component or subsystem of the mobile platform of  FIG. 1 ; 
         FIG. 3  is a flowchart illustrating exemplary operations that may be performed by the system of the present disclosure in carrying out a test of an existing component or subsystem of the mobile platform; 
         FIG. 4  is an alternative embodiment of the present disclosure in which a single hybrid controller is used to control both the existing components of the mobile platform as well as dedicated test components included on the mobile platform; 
         FIG. 5  is an alternative embodiment of the system of claim  4  in which a health assessment subsystem has been included for monitoring a health of the aircraft control system of the mobile platform; and 
         FIG. 6  is a flow diagram illustrating the operation of the system shown in  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. 
     The present disclosure describes novel systems and methods to non-intrusively characterize and model the dynamic response of individual hinged control surface effectors typically used on mobile platforms, and even more particularly on airborne mobile platforms such as aircraft. The systems and methods disclosed herein enable small magnitude, test commanded surface motions to be instantaneously countered by the same agile independent active flow control actuators used to characterize each surface of the mobile platform. This nullification of small magnitude test commands to electro-hydraulic actuators on the mobile platform enables determination of the health of backup control systems of the mobile platform without disturbing the states of the mobile platform (or other form of vehicle, device or apparatus) while in service, and advantageously is transparent to normal operation of the primary control system of the mobile platform, device or apparatus. 
     Referring to  FIG. 1  there is shown a system  10  for non-intrusively testing the performance of an aircraft control system  12  (i.e., an “on-board control system”) carried on a mobile platform  14 . The mobile platform  14  is illustrated merely for discussion purposes as a jet aircraft, and will be referred to throughout the following discussion as “the aircraft  14 ”. However, the present system  10  may be used with any form of mobile platform. Such other mobile platforms may be motor land vehicles, surface or underwater marine vessels, space vehicles, rotorcraft, as well as unmanned mobile vehicles. The system  10  is equally well adapted for use with fixed (i.e., non-mobile) systems where a desire to test or evaluate the operation of one or more subsystems of the non-mobile system is needed. Such non-mobile applications might involve, without limitation, manufacturing or robotic machinery. 
     The system  10  can be viewed as comprising a first portion  16  that forms a non-intrusive aircraft and control system verification and health assessment subsystem. A second portion  18  may be viewed as forming a continuous, non-intrusive aerodynamic control surface assessment subsystem. In this example the first portion is well suited for testing specific aircraft subsystems such as sensors, flaps, ailerons, valves, etc., while the second portion  18  is especially well suited for evaluating the control laws implemented by the aircraft control system  12 . 
     It will be understood that the aircraft control system  12  may be tailored to the specific type of mobile platform that is being used on. The aircraft control system  12  thus forms a permanent portion of the aircraft  14  and is used to control operation of the aircraft  14  and its diverse components and subsystems. Merely as an example, the aircraft control system  12  may include a summing junction  20  for receiving pilot inputs, a controller  22  and one or more actuators  24  controllable by the controller  22 . The one or more actuators  24  may control one or more aerodynamic control surfaces  26 , which in turn may control one or more aircraft sensors, and/or aircraft subsystems, and/or other component(s)  28 . For convenience, the following discussion will simply refer to component  28  as the “sensor”, although it will be appreciated that virtually any type of component, sensor or subsystem of the aircraft  14  may be tested. 
     First portion  16  of the system  10  includes a test controller  30  that is loaded with one or more specific algorithms  32 . The algorithms  32  are used to implement specific test operations to test and evaluate the performance of virtually any of the subsystems or components of the aircraft&#39;s control system  12 . The test controller  30 , which is independent of the aircraft&#39;s on-board control system  12 , also receives an input from the controller  22  that identifies important parameters of operation of the aircraft control system  12  that the test controller  30  may need to know to implement specific tests of various components of the aircraft control system  12 . Such specifics may be the specific types of flow control sensors or components being used and performance attributes of such components or systems. For example, a specific model number or type of sensor  28  may be supplied to the test controller  30  by the aircraft&#39;s controller  22 . 
     The first portion  16  further may include a perturbance test signal system or generator  34  that is responsive to the test controller  30  for generating a perturbance test signal. The perturbance test signal may be applied to a summing junction  36  and then to a test subsystem  38 , which may be termed for convenience an “aero flow control subsystem”. The aero flow control subsystem  38  influences operation of the aircraft sensors  28 . In practice the aero flow control subsystem  38  may comprise active flow control component such as an electromagnetic oscillatory jet actuator that is either built in to a structural portion of the aircraft  14  adjacent a component to be tested. The aero flow control subsystem  38  is controllable completely independently of the controller  22  so that the effect of its generated flow (i.e., aerodynamic influence) on the aircraft sensor(s) may be studied. A feedback signal represented by feedback line  38   a  is fed back into the test controller  30  to form a closed loop arrangement for controlling and monitoring the aero flow control subsystem  38 . 
     Various potential forms of the perturbance test signal that may be generated from the perturbance test signal generator  34  are shown in  FIGS. 2A-2E . Potential perturbance signals may comprise decaying oscillatory signals ( FIG. 2A ), transients ( FIG. 2B ), frequency constant sinusoidal waveforms ( FIG. 2C ), short sinusoidal like transients ( FIG. 2D ) and square wave signals ( FIG. 2E ). However, it will be appreciated that these waveforms are merely exemplary, and virtually any other form of input signal may be used as the component or subsystem being tested dictates. 
     The output of the aircraft sensor(s)  28  may be fed back to the summing junction  20  to thus modify the resulting signal applied to the aircraft&#39;s controller  22 . The output from the aircraft sensor(s)  28  may also be applied to a summing junction  40  of the second portion  18 . A near zero detection subsystem  42  may form a hardware or software implemented subsystem that generates a particular signal when the output from the summing junction  40  is zero or within an acceptable range around zero. It will be appreciated that subsystem  42  is particularly useful for those scenarios where the aircraft would be flying straight and level. However, it will be understood that subsystem  42  would not be active during dynamic aircraft maneuvers, and thus would not be needed while monitoring dynamic aircraft maneuvers. 
     The output of the near zero detection subsystem  42  may be fed back to the test controller  30  as well as to a continuous contra-surface command subsystem  44 . Subsystem  44  removes the effects of small steady-state control command off-sets from the test operations performed in the test controller  30 . The output of the continuous contra-surface command subsystem  44  may be applied to the summing junction  36  to further modify the perturbance test signal that is used to control the subsystem  28  that acts on the aircraft sensor(s)  28 . 
     Referring now to the flowchart  100  of  FIG. 3 , a sequence of operations that may be performed by the system  10  is set forth. At operation  102  the test controller  30  receives needed information from the controller  22  as to component and/or parameter identification, component condition, etc. that the test controller  30  requires to carry out the test operation. At operation  104  the test controller  30  sends an output signal to the perturbance test signal generator  34  to generate a specific type of perturbance test signal, for example one of the types of signals shown in  FIGS. 2A-2E . At operation  106  the perturbance test signal is applied to the aero flow control subsystem  38  which generates a flow control signal adjacent to the aircraft sensor or component being tested. At operation  108  the flow output from the aero flow control subsystem  38  acts on the aircraft  28 . At operation  110  the output from the aircraft sensor(s)  28  is fed to the summing junction  40  along with an output signal from the test controller  30 . At operation  112  the zero detection subsystem  42  detects whether or not the output from the summing junction  40  is essentially zero or within a small, predetermined range from zero, and if so generates a signal that is fed back to the test controller  30  indicating this condition, as indicated at operation  114 . Thus, a closed loop test control system is formed between the test controller  30  and the aircraft sensor(s)  28  being tested. Importantly, the testing is accomplished non-intrusively relative to the aircraft&#39;s control system  12 . Another significant advantage is that the controller  22  and other components of the aircraft control system  12  of the aircraft  14  are not used nor needed to implement the test. 
     At operation  116  the output signal from the zero detection subsystem  42  may also be applied to the continuous contra-surface command generator  44 . The continuous contra-command test generator  44  may then generate a signal that is applied to the summing junction  36  to modify the perturbance signal. 
     Referring to  FIG. 4 , a system  200  is shown in accordance with another embodiment of the present disclosure. The system  200  is carried by the aircraft  14  and makes use of a controller  202 , an existing actuator (or actuators)  204  of the aircraft  14 , an oscillatory jet actuator  206  that forms a dedicated test component, existing aircraft  208  (i.e., dynamic response of the aircraft airframe) of the entire aircraft  14  including the control system and existing sensor(s)  210 . In the embodiment  200  the controller  202  controls both the dedicated test functions as well as the normal operating functions required to manage the subsystems and components of the aircraft  14 . 
     Using active flow control (AFC) oscillatory jet actuation technology can result in a significant increase in control bandwidth that also enables independent control of airfoil lift, drag and pitching moments. Due to the high bandwidth capabilities of AFC-equipped aircraft, health assessment of the aircraft and its subsystems including its control system can be achieved if the behavior of these components or subsystems can be independently observed and processed. The much higher bandwidth of the oscillatory jet actuators enables the use of real-time broadband frequency response tests. These tests can be specifically synthesized to accentuate features in the observed frequency response of the aircraft dynamics and the aircraft&#39;s entire control system  12  (i.e., including controller, sensors, processors, actuators, and control surfaces), that are indicative and/or typical of degradation and failures. This may be accomplished by generating a specific synthesized reference signal carrying the test signal. 
     Once the observed behavior in the form of measured feedback is sampled, processed and decoupled using the embodiment  200 , component and subsystem performance specific information can be extracted to assess the capability and health of the entire system  200 . An embodiment  300  of the present disclosure for enabling health evaluation of various subsystems and components being carried by the aircraft  14  is shown in  FIG. 5 . System  300  is identical to system  200 , and thus components in common with the system  200  have been labeled with reference numbers increased by 100 over those used in  FIG. 4 . The system  300  makes use of an aircraft and control system health assessment subsystem  312 . In  FIG. 5 , the various signals being output by the subsystems and components are: 
     u, which is the controller output to the main actuators  304 ; 
     u AFC , which is the controller  302  AFC output to the oscillatory jet actuators  306 ; 
     r is the reference input to the aircraft control system; 
     ŷ is the measured feedback signal from the aircraft&#39;s sensors  310 ; 
     i is the computed aircraft and control system health assessment (for example: remaining actuator life, linkage wear, backlash, steady state offset, reduced rates, changes in airframe dynamics etc); and 
     r HA  is the synthesized reference input to the controller  302  replacing the initial reference input. 
     The value r HA  is synthesized and carries the specific test signals as well as the reference input to the controller  302 . 
     In operation as shown in the flow diagram of  FIG. 6 , the observed dynamic behavior of the aircraft  14  and the entire system  300  is shown. Controller  302 , sensors  310 , actuators  302 , and aircraft dynamics  308  are sampled in the form of measured feedback with the desired reference, control command (i.e., “u”) for the actuators  304  as well as air flow control (AFC) command (i.e., “j”) from the oscillatory jet actuators  306 , as indicated at operation  400 . Once the data is collected by the health assessment subsystem  312 , utilizing digital signal processing, the data is transformed from time-domain to frequency-domain, as indicated at operation  402 . This creates a dynamic signature portfolio with distinct component and subsystem profiles. Once the frequency-domain transformation is completed, a dynamic signature portfolio with magnitude and phase data components is extracted for further analysis, as indicated at operation  404 . The magnitude and phase data components are then further processed for decoupling. The decoupling process, as indicated at operation  406 , consists of selectively comparing known subsystem specific signatures with known magnitude and phase coefficients against sampled data components. Here, all system and subsystem specific frequency-domain magnitude and phase coefficients will be extracted and measured against the known and expected dynamic signatures. Therefore, any performance degradation or change in dynamic behavior will be detected by the health assessment subsystem  312  in the frequency-domain. Next, as indicated at operation  408 , based on the computed system and subsystem specific performance, capability and health assessment, and in order to maximize efficiency and coverage of the components, a customized test (i.e., reference) signal is generated. The customized test signal may be combinations of doublet, impulse, sinusoidal, and other test inputs as indicated in  FIGS. 2A-2E . The test signal is selected to confirm and to further assess the capability and the health of the entire system  300  or one or several specific subsystem(s) thereof. Finally, the signature of the test signal and the desired reference signal, both in the form of frequency magnitude and phase coefficients, will be mixed in order to synthesize and generate a new reference waveform. 
     The embodiments of the present disclosure all provide various significant advantages and benefits in non-intrusively monitoring and testing the various components and subsystems of a mobile platform, as well as enabling considerable cost savings over pre-existing system test arrangement: For example, the various embodiments described herein enable on-line identification of aircraft model parameters, thus shortening the time required for flight testing. The various embodiments enable independent determination of control system health condition, thus providing a means to shorten the time required to verify and validate aircraft control systems. The various embodiments also enable the application of adaptive control methods through real-time independent determination of aircraft dynamic characteristics and systems health. The various embodiments enable the application of reconfigurable methods through real-time independent determination of aircraft dynamic characteristics and systems health. The various embodiments enable the continued monitoring and parameter identification subsequent to control system reconfiguration. The various embodiments also enable the use of high bandwidth controlled excitation test signals, thus providing a means to quickly determine structural dynamics during flight at all flight and load conditions. The various embodiments enable a more accurate health assessment by using test signals customized for specific parameter identification and operating during flight under varying environmental conditions. Finally, the various embodiments enable real-time monitoring and control independent of control system degradation monitoring and fault identification. 
     While various embodiments have been described, those skilled in the art will recognize modifications or variations which might be made without departing from the present disclosure. The examples illustrate the various embodiments and are not intended to limit the present disclosure. Therefore, the description and claims should be interpreted liberally with only such limitation as is necessary in view of the pertinent prior art.