Special Coverage

Home

General Methodology for Designing Spacecraft Trajectories

A methodology for designing spacecraft trajectories in any gravitational environment within the solar system has been developed. The methodology facilitates modeling and optimization for problems ranging from that of a single spacecraft orbiting a single celestial body to that of a mission involving multiple spacecraft and multiple propulsion systems operating in gravitational fields of multiple celestial bodies. The methodology consolidates almost all spacecraft trajectory design and optimization problems into a single conceptual framework requiring solution of either a system of nonlinear equations or a parameter-optimization problem with equality and/or inequality constraints.

Posted in: Information Sciences, Briefs

Read More >>

Pattern Recognition Algorithm for High- Sensitivity Odorant Detection in Unknown Environments

In a realistic odorant detection application environment, the collected sensory data is a mix of unknown chemicals with unknown concentrations and noise. The identification of the odorants among these mixtures is a challenge in data recognition. In addition, deriving their individual concentrations in the mix is also a challenge.

Posted in: Information Sciences, Briefs

Read More >>

Method for Pre-Conditioning a Measured Surface Height Map for Model Validation

This method can be implemented in most optical modeling and simulation software. This software allows one to up-sample or down-sample a measured surface map for model validation, not only without introducing any re-sampling errors, but also eliminating the existing measurement noise and measurement errors. Because the re-sampling of a surface map is accomplished based on the analytical expressions of Zernike-polynomials and a power spectral density model, such re-sampling does not introduce any aliasing and interpolation errors as is done by the conventional interpolation and FFT-based (fast-Fourier-transformbased) spatial-filtering method. Also, this new method automatically eliminates the measurement noise and other measurement errors such as artificial discontinuity.

Posted in: Information Sciences, Briefs

Read More >>

Recursive Branching Simulated Annealing Algorithm

The algorithm can be applied to a wide variety of optimization problems. This innovation is a variation of a simulated- annealing optimization algorithm that uses a recursive-branching structure to parallelize the search of a parameter space for the globally optimal solution to an objective. The algorithm has been demonstrated to be more effective at searching a parameter space than traditional simulated- annealing methods for a particular problem of interest, and it can readily be applied to a wide variety of optimization problems, including those with a parameter space having both discrete-value parameters (combinatorial) and continuous-variable parameters. It can take the place of a conventional simulated-annealing, Monte- Carlo, or random-walk algorithm.

Posted in: Information Sciences, Briefs

Read More >>

Rotorcraft Diagnostics

Health management (HM) in any engineering systems requires adequate understanding about the system’s functioning; a sufficient amount of monitored data; the capability to extract, analyze, and collate information; and the capability to combine understanding and information for HM-related estimation and decision-making. Rotorcraft systems are, in general, highly complex. Obtaining adequate understanding about functioning of such systems is quite difficult, because of the proprietary (restricted access) nature of their designs and dynamic models. Development of an EIM (exact inverse map) solution for rotorcraft requires a process that can overcome the abovementioned difficulties and maximally utilize monitored information for HM facilitation via employing advanced analytic techniques.

Posted in: Information Sciences, Briefs

Read More >>

Sampling and Reconstruction of the Pupil and Electric Field for Phase Retrieval

This technology is based on sampling considerations for a band-limited function, which has application to optical estimation generally, and to phase retrieval specifically. The analysis begins with the observation that the Fourier transform of an optical aperture function (pupil) can be implemented with minimal aliasing for Q values down to Q = 1. The sampling ratio, Q, is defined as the ratio of the sampling frequency to the band-limited cut-off frequency. The analytical results are given using a 1-d aperture function, and with the electric field defined by the band-limited sinc(x) function. Perfect reconstruction of the Fourier transform (electric field) is derived using the Whittaker-Shannon sampling theorem for 1

Posted in: Information Sciences, Briefs

Read More >>

Stiffness and Damping Coefficient Estimation of Compliant Surface Gas Bearings for Oil-Free Turbomachinery

Initial applications include design of turbochargers, blowers, compressors, pumps, and turbine engines. Foil gas bearings are a key technology in many commercial and emerging oilfree turbomachinery systems. These bearings are nonlinear and have been difficult to analytically model in terms of performance characteristics such as load capacity, power loss, stiffness, and damping. Previous investigations led to an empirically derived method to estimate load capacity. This method has been a valuable tool in system development. The current work extends this tool concept to include rules for stiffness and damping coefficient estimation. It is expected that these rules will further accelerate the development and deployment of advanced oil-free machines operating on foil gas bearings.

Posted in: Information Sciences, Briefs

Read More >>

White Papers

Drive On – E-Bikes Shift into High Gear
Sponsored by HP
How to Choose the Right Sensor for Your Measurement System
Sponsored by National Instruments
Future Advances in Body Electronics
Sponsored by Freescale
Inclinometers for Motion Control
Sponsored by Fraba Posital
PICO xMOD Data Sheet
Sponsored by Nordson EFD
Back to Basics of Electrical Measurement
Sponsored by Keithley

White Papers Sponsored By: