Jessica Alvarenga

Strain-Based Deformation Shape-Estimation Algorithm for Control and Monitoring Applications

A new deformation shape-sensing methodology is investigated for the purposes of real-time condition assessment, control, and health monitoring of flexible lightweight aerospace structures. The fiber optic strain sensing technology was recently proposed by the NASA Dryden Flight Research Center. The methodology implements the use of fiber optic sensors to obtain strain measurements from the target structure and to estimate the corresponding displacement field. In this paper, the methodology is investigated through an experimental aluminum winglike swept-plate model. The proposed algorithm is implemented for three distinct loading cases and compared to a well-established modal-based shape-estimation algorithm. The estimation results from both methods are also compared to reference displacements from photogrammetry and computational analyses. The estimation error for each method is quantified using the root-mean-square measure, and the range of validity of the approach for damage detection is established. Fu...

Survey of Unmanned Helicopter Model-Based Navigation and Control Techniques

Unmanned Aircraft Systems(UAS) have seen unprecedented levels of growth during the last two decades. Although many challenges still exist, one of the main UAS focus research areas is in navigation and control. This paper provides a comprehensive overview of helicopter navigation and control, focusing specifically on small-scale traditional main/tail rotor configuration helicopters. Unique to this paper, is the emphasis placed on navigation/control methods, modeling techniques, loop architectures and structures, and implementations. A ‘reference template’ is presented and used to provide a basis for comparative studies and determine the capabilities and limitations of algorithms for unmanned/autonomous flight, as well as for navigation, and control. A detailed listing of related research is provided, which includes model structure, helicopter platform, control method and loop architecture, flight maneuvers and results for each. The results of this study was driven by and has led to the development of a ‘one-fits-all’ comprehensive and modular navigation controller and timing architecture applicable to any rotorcraft platform.

Computational studies of a strain-based deformation shape prediction algorithm for control and monitoring applications

A modal approach is investigated for real-time deformation shape prediction of lightweight unmanned flying aerospace structures, for the purposes of Structural Health Monitoring (SHM) and condition assessment. The deformation prediction algorithm depends on the modal properties of the structure and uses high-resolution fiber-optic sensors to obtain strain data from a representative aerospace structure (e.g., flying wing) in order to predict the associated real-time deflection shape. The method is based on the use of fiber-optic sensors such as optical Fiber Bragg Gratings (FBGs) which are known for their accuracy and light weight. In this study, the modal method is examined through computational models involving Finite-Element Analysis (FEA). Furthermore, sensitivity analyses are performed to investigate the effects of several external factors such as sensor locations and noise pollution on the performance of the algorithm. This work analyzes the numerous complications and difficulties that might potentially arise from combining the state-of-the-art advancements in sensing technology, deformation shape prediction, and structural health monitoring, to achieve a robust way of monitoring ultra lightweight flying wings or next-generation commercial airplanes.

Control of a simulated wing structure with multiple segmented control surfaces

The main objective of this paper is to demonstrate that a wing with segmented control surfaces can redistribute its load, inboard or outboard, in order to perform active shape control while still maintaining level flight. Methods will be presented for controlling the plunge deflections of an aircraft wing structure. One possible solution to improving the flight envelope is a wing design with multiple segmented control surfaces all along its span. This will give an aircraft far more control over its lift distribution in comparison to a typical wing. In order to construct a wing with segmented trailing edges, it must first be shown that deflections under lift loads can be controlled. This paper introduces the research performed by the Structures, Propulsion, and Controls Engineering (SPACE) Center using a Fiber-Optic Strain-Sensing (FOSS) system that is currently implemented on the Odyssey UAV. The research will use a set of strain-based Displacement Transfer Functions (DTF) and the FOSS System both of which were developed at the NASA Dryden Flight Research Center (DFRC). Aerodynamic loads are obtained through the use of the software Athena Vortex Lattice (AVL). In addition, structural modeling is carried out with the use of finite element software. The results indicate that the shape of a wing structure can be controlled through the manipulation of segmented control surfaces to re-distribute lifting loads.

Scaled control performance benchmarks and maneuvers for small-scale unmanned helicopters

The paper proposes a methodology for designing trajectories to form a basis for evaluating and comparing performance of navigation controllers on any small-scale helicopter platforms, as there currently exist no benchmarks for small-scale helicopters. Consideration is given to maneuvers designed to evaluate full-scale helicopter/pilot combinations adapting them to the dynamics of small-scale helicopters. Two helicopter models are used as experimental testbeds: the DU2SRI Bergen Industrial Turbine and Raptor SE90 helicopters. Three different controllers, ℋ∞, LQR, and PID, are tested against the scaled maneuvers in order to evaluate and compare the performance of each controller. Trajectories are designed according to the proposed scaling laws and they are chosen to be outside and well within the capabilities of the helicopter dynamics to demonstrate the importance of selecting trajectories that both exploit the controller weaknesses while remaining within the flight capabilities of the helicopter.

Ray tracing visualization using LabVIEW for Precision Pointing Architecture of a segmented reflector testbed

For deep space exploration, it is important for telescopes to have a high accuracy and precision in pointing at objects far in space. In addition, a large segmented space telescope requires high precision and accuracy in mirror shape. The Segmented Space Telescope Testbed at the Structures, Propulsion, and Control Engineering (SPACE) Laboratory at California State University, Los Angeles utilizes segmented mirror panels to mimic a parabolic mirror and a series of lasers and mirrors to demonstrate pointing control. This paper discusses a LabVIEW based visualization that is used for pointing simulation of the SPACE Testbed. The Visualization allows for simulation of the physical Precision Pointing Architecture (PPA) that allows for visual verification of pointing control.

LabVIEW calibration linearity visualization for precision sensors used in shaping control of a segmented reflector test bed

A large, segmented space telescope requires high precision and accuracy in its mirror shape to obtain clear images. In order for control of such complex structures to be achieved to high precision and accuracy, it is important for sensing equipment involved in shape control to be constantly checked for deviations from their required calibration. The Segmented Space Telescope Testbed at the Structures, Propulsion, and Control Engineering (SPACE) Laboratory at California State University, Los Angeles, utilizes segmented mirror panels and a network of 42 sensors to mimic a monolithic paraboloid mirror shape to high accuracy and precision. For such a high precision system, regular checking of sensor calibration is crucial to performance. This paper describes a LabVIEW — based visualization subsystem that has been implemented and used for sensor calibration of the SPACE Testbed. The subsystem allows for linearity check for each sensor. In addition, the visualization subsystem provides a real-time means of system monitoring. The visualization also reduces the time to check all 42 sensors while at the same time improve the precision and accuracy of the measurements. By reducing the time required, it is easier to verify sensor linearity at regular interval.

An actuated platform FEA model used for precision pointing control

A large, segmented space telescope requires high precision and accuracy in its mirror shape to obtain clear images. The Structures, Propulsion, and Control Engineering (SPACE) telescope testbed at the NASA sponsored University Research Center must maintain a pointing control accuracy of 2 arc seconds. A Peripheral Pointing Architecture (PPA) has been designed to demonstrate the testbed pointing accuracy. A finite element model of the PPA is developed. Normal mode analysis is performed to establish the PPAs natural frequencies, mode shapes, mass and stiffness matrices. Utilizing H-infinity controllers developed for figure maintenance, the pointing control of the testbed structure is achieved.

Validation of a Strain-Based Wing Shape Prediction Algorithm for Control and Monitoring of an Uninhabited Air Vehicle

Recent improvements in technology has enabled the use of very sophisticated sensors such as embedded fiber bragg gratings (FBGs) to obtain strain measurements from a variety of structural types. Conventional strain gauges tend to be heavy and bulky. Because of their accuracy, light weight, small size and flexibility these fiber optic sensors have big potential to be used in space exploration and the aerospace industry especially for flying aircraft that have strict weight and size limitations. These strain measurements can be used to predict the deformation shape of aircraft during real-time flights. The development of such methods for monitoring and control can potentially reduce the risk of in-flight breakups, such as that of the Helios Wing.The Structures, Propulsion, And Control Engineering (SPACE) NASA sponsored University Research Center (URC) of excellence has concentrated in the development of small, lightweight Uninhabited Air Vehicles (UAVs) that have excelled in the area of endurance. Today, the UAV project is focused on the design of a multi-mission multipurpose air system that can operate autonomously. The configuration is a twin boom, pusher, and conventional wing design. In this paper, methods developed by the National Aeronautic and Space Administration (NASA)’s Dryden Flight Research Center for real-time deformation shape prediction of lightweight unmanned flying aerospace structures for the purposes of Structural Health Monitoring (SHM) and condition assessment are investigated. SHM may allow for useful monitoring that would prevent such an event by providing wing shape information and structural monitoring to either a pilot or the flight system, allowing for evasive maneuvers before the breakup would occur. These methods also have the potential for increasing safety, allowing monitoring of structural integrity, detecting damages, and providing real-time flight control feedback. These methods are applied to the SPACE Center UAV for the purpose of assessing the effectiveness of the method and the potential for both SHM and control applications. In this paper, a computational finite element model of the SPACE Center UAV is developed and used to examine the method.Copyright