An application of eigenspace methods to symmetric flutter suppression

An eigenspace assignment approach to the design of parameter insensitive control laws for linear multivariable systems is presented. The control design scheme utilizes flexibility in eigenvector assignments to reduce control system sensitivity to changes in system parameters. The methods involve use of the singular value decomposition to provide an exact description of allowable eigenvectors in terms of a minimum number of design parameters. In a design example, the methods are applied to the problem of symmetric flutter suppression in an aeroelastic vehicle. In this example the flutter mode is sensitive to changes in dynamic pressure and eigenspace methods are used to enhance the performance of a stabilizing minimum energy/linear quadratic regulator controller and associated observer. Results indicate that the methods provide feedback control laws that make stability of the nominal closed loop systems insensitive to changes in dynamic pressure

Integrated airframe propulsion control

Perturbation equations which describe flight dynamics and engine operation about a given operating point are combined to form an integrated aircraft/propulsion system model. Included in the model are the dependence of aerodynamic coefficients upon atmospheric variables along with the dependence of engine variables upon flight condition and inlet performance. An off-design engine performance model is used to identify interaction parameters in the model. Inclusion of subsystem interaction effects introduces coupling between flight and propulsion variables. To analyze interaction effects on control, consideration is first given to control requirements for separate flight and engine models. For the separate airframe model, feedback control provides substantial improvement in short period damping. For the integrated system, feedback control compensates for the coupling present in the model and provides good overall system stability. However, this feedback control law involves many non-zero gains. Analysis of suboptimal control strategies indicates that performance of the closed loop integrated system can be maintained with a feedback matrix in which the number of non-zero gains is small relative to the number of components in the feedback matrix

Anaerobic Dechlorination of Polychlorinated Dibenzo-p-dioxins in Passaic River Sediments

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) are persistent, bioaccumulative and toxic pollutants found in the environment. The Passaic River in New Jersey is highly contaminated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TeCDD), one of the most toxic of the PCDD/F congeners. Our on-going research at Rutgers is intended to better understand PCDD/F dichlorination by anaerobic organohalide respiring bacteria (OHRB). Results will be presented from various anaerobic enrichment cultures (including from the Passaic River) enriched on alternate organohalides such as trichloroethene and dichlorobenzene to stimulate OHRB. Activity against three PCDD congeners: 1,2,3,4-tetrachlorodibenzo-p-dioxin, a well-studied model PCDD congener; 2,3,7,8-TeCDD; and 2,7-dichlorodibenzo-p-dioxin, a potential metabolite of 2,3,7,8- TeCDD, have been investigated. After 1.5 years, dechlorination of all tested dioxin congeners was observed in one or more replicate of each Passaic River sediment treatment. Preliminary 16S rRNA gene sequencing indicates dominance of a specific Dehalococcoidia phylotype in the 2,3,7,8-TeCDD dechlorinating enrichment. Further characterization of the bacteria could provide methods for monitoring dechlorination in contaminated sites and lead to new in situ treatment technologies

Flutter suppression using eigenspace freedoms to meet requirements

A constrained optimization methodology has been developed which allows specific use of eigensystem freedoms to meet design requirements. A subset of the available eigenvector freedoms was employed. The eigenvector freedoms associated with a particular closed-loop eigenvalue are coefficients of basis vectors which span the subspace in which that closed-loop vector must lie. Design requirements are included as a vector of inequality constraints. The procedure was successfully applied to develop an unscheduled controller which stabilizes symmetric flutter of an aeroelastic vehicle to a dynamic pressure 44 percent above the open-loop flutter point. The design process proceeded from full-state feedback to the inclusion of a full-order observer to the selection of an eighth-order controller which preserved the full-state sensitivity characteristics. Only a subset of the design freedoms was utilized (i.e., assuming full-state feedback only four out of 26 eigenvectors were used, and no variations were made in the closed-loop eigenvalues). Utilization of additional eigensystem freedoms could further improve the controller

AMPTE/CCE‐SCATHA simultaneous observations of substorm‐associated magnetic fluctuations

This study examines substorm-associated magnetic field fluctuations observed by the AMPTE/CCE and SCATHA satellites in the near-Earth tail. Three tail reconfiguration events are selected, one event on August 28, 1986, and two consecutive events on August 30, 1986. The fractal analysis was applied to magnetic field measurements of each satellite. The result indicates that (1) the amplitude of the fluctuation of the north-south magnetic component is larger, though not overwhelmingly, than the amplitudes of the other two components and (2) the magnetic fluctuations do have a characteristic timescale, which is several times the proton gyroperiod. In the examined events the satellite separation was less than 10 times the proton gyroradius. Nevertheless, the comparison between the AMPTE/CCE and SCATHA observations indicates that (3) there was a noticeable time delay between the onsets of the magnetic fluctuations at the two satellite positions, which is too long to ascribe to the propagation of a fast magnetosonic wave, and (4) the coherence of the magnetic fluctuations was low in the August 28, 1986, event and the fluctuations had different characteristic timescales in the first event of August 30, 1986, whereas some similarities can be found for the second event of August 30, 1986. Result 1 indicates that perturbation electric currents associated with the magnetic fluctuations tend to flow parallel to the tail current sheet and are presumably related to the reduction of the tail current intensity. Results 2 and 3 suggest that the excitation of the magnetic fluctuations and therefore the trigger of the tail current disruption is a kinetic process in which ions play an important role. It is inferred from results 3 and 4 that the characteristic spatial scale of the associated instability is of the order of the proton gyroradius or even shorter, and therefore the tail current disruption is described as a system of chaotic filamentary electric currents. However, result 4 suggests that the nature of the tail current disruption can vary from event to event

A new, temporarily confined population in the polar cap during the August 27, 1996 geomagnetic field distortion period

On August 27, 1996, a two-hour energetic heavy ion event (∼1 MeV) was detected at 8:25 UT at apogee (∼9 Re and an invariant latitude of ∼80°), by the Charge and Mass Magnetospheric Ion Composition Experiment onboard POLAR. The event, with a maximum spin averaged peak flux of ∼150 particles/(cm²-sr-s-MeV), showed three local peaks corresponding to three localized regions; the ion pitch angle distributions in the three regions were different from an isotropic distribution and different from each other. No comparable flux was observed by the WIND spacecraft. The appearance of lower energy He++ and O \u3e +2 during the event period indicates a solar source for these particles. From region 1 to 2 to 3, the helium energy spectra softened. A distorted magnetic field with three local minima corresponding to the three He peak fluxes was also observed by POLAR. A possible explanation is that the energetic He ions were energized from lower energy helium by a local acceleration mechanism that preferred smaller rigidity ions in the high altitude polar cusp region

CO2 capture and storage (CCS) cost reduction via infrastructure right-sizing

Carbon capture and storage (CCS) will be a critical component of a portfolio of low-carbon energy technologies required to combat climate change (Technology Roadmap, 2013). As such, an extensive transportation infrastructure will be required to transport captured CO2 from different sources to the available sinks. Several studies in the literature suggest that shared oversized pipeline networks may be the most efficient long term option compared to single source to sink pipelines, based on increased CCS deployment over the years and therefore increased CO2 flowrate to the transport network. However, what is neglected in this vision is that the deployment of intermittent renewable energy tends to displace thermal power generation. This directly reduces the amount of fossil fuel burned, CO2 produced, captured and transported through the network. This paper presents an optimisation methodology to “right-size” CO2 transport infrastructure, explicitly accounting for the transient flow of CO2 arising from the co-deployment of intermittent renewable energy generators. By application of this methodology, we demonstrate that capital cost reductions of up to 28% are possible relative to a business-as-usual design case