Eigenspace design techniques for active flutter suppression

The application of eigenspace design techniques to an active flutter suppression system for the DAST ARW-2 research drone is examined. Eigenspace design techniques allow the control system designer to determine feedback gains which place controllable eigenvalues in specified configurations and which shape eigenvectors to achieve desired dynamic response. Eigenspace techniques were applied to the control of lateral and longitudinal dynamic response of aircraft. However, little was published on the application of eigenspace techniques to aeroelastic control problems. This discussion will focus primarily on methodology for design of full-state and limited-state (output) feedback controllers. Most of the states in aeroelastic control problems are not directly measurable, and some type of dynamic compensator is necessary to convert sensor outputs to control inputs. Compensator design are accomplished by use of a Kalman filter modified if necessary by the Doyle-Stein procedure for full-state loop transfer function recovery, by some other type of observer, or by transfer function matching

Eigenspace techniques for active flutter suppression

Eigenspace (ES) techniques were used to design an active flutter suppression system for the DAST ARW-2 flight test vehicle. The ES controller meets control surface activity specifications and at the flutter test condition provides reduced wing root torsion at the gust test condition, and results in improved flutter boundaries. The ES controller is compared with a controller designed using Linear Quadratic (LQ) techniques. The LQ controller exhibits better phase margins at the flutter condition than does the ES controller but the LQ design requires large feedback gains on actuator states while the ES does not. This results in reduced overall actuator gain for the LQ design

Suboptimal compensation of gyroscopic coupling for inertia-wheel attitude control

Suboptimal compensation of gyroscopic coupling for inertia-wheel attitude control by mathematical technique

Eigenspace techniques for active flutter suppression

Mathematical models to be used in the control system design were developed. A computer program, which takes aerodynamic and structural data for the ARW-2 aircraft and converts these data into state space models suitable for use in modern control synthesis procedures, was developed. Reduced order models of inboard and outboard control surface actuator dynamics and a second order vertical wind gust model were developed. An analysis of the rigid body motion of the ARW-2 was conducted. The deletion of the aerodynamic lag states in the rigid body modes resulted in more accurate values for the eigenvalues associated with the plunge and pitch modes than were obtainable if the lag states were retained

Active flutter control for flexible vehicles, volume 1

An active flutter control methodology based on linear quadratic gaussian theory and its application to the control of a super critical wing is presented. Results of control surface and sensor position optimization are discussed. Both frequency response matching and residualization used to obtain practical flutter controllers are examined. The development of algorithms and computer programs for flutter modeling and active control design procedures is reported

Preparation of thin polymer films for infrared reaction rate studies

Procedure for preparing thin films for infrared spectrophotometric analysis involves pressing of a neat mixture of reactants between nonreactive thin polymer films with noninterfering absorption bands. Pressing is done under a pressure that gives desirable thickness. Following this process, the film sandwich is cut to accommodate the laboratory instrument

On the synthesis of suboptimal, inertia-wheel attitude control systems

Suboptimal systems synthesis using motor-driven inertia wheels for attitude contro

A comparison of handwritten and computer-assisted prescriptions in an intensive care unit

BACKGROUND: We conducted a prospective comparative study to evaluate the potential benefit of computer-assisted prescribing (CAP). We compared the accuracy, completeness and time use of CAP with that of conventional handwritten prescribing at the intensive care unit (ICU) of the John Radcliffe Hospital, Oxford, UK. RESULTS: Twenty-five clinicians and 2409 drug entries were evaluated for accuracy, completeness, legibility and time spent prescribing. One hundred and twenty-eight handwritten and 110 CAP charts were monitored. One hundred percent of CAP charts were complete compared to 47% of handwritten charts.Drug prescriptions were divided into three categories: intravenous fluids, intravenous infusions and intermittent drugs. Percentage of correct entries in each category were 64%, 47.5% and 90% for handwritten, compared to 48%, 32% and 90% for CAP charts, respectively.The mean time taken to prescribe was 20 s for hand written prescribing and 55 s for CAP. CONCLUSIONS: Computer-assisted prescriptions were more complete, signed and dated than handwritten prescriptions. Errors in prescribing, including failure to discontinue a drug were not reduced by CAP. Handwritten prescribing was quicker than CAP. Simple enhancements of the computer software could be introduced which might overcome these deficiencies. CAP was successfully integrated into clinical practice in the ICU