Distributed Receding Horizon Control with Application to Multi-Vehicle Formation Stabilization

We consider the control of interacting subsystems whose dynamics and constraints are uncoupled, but whose state vectors are coupled non-separably in a single centralized cost function of a finite horizon optimal control problem. For a given centralized cost structure, we generate distributed optimal control problems for each subsystem and establish that the distributed receding horizon implementation is asymptotically stabilizing. The communication requirements between subsystems with coupling in the cost function are that each subsystem obtain the previous optimal control trajectory of those subsystems at each receding horizon update. The key requirements for stability are that each distributed optimal control not deviate too far from the previous optimal control, and that the receding horizon updates happen sufficiently fast. The theory is applied in simulation for stabilization of a formation of vehicles

Feedback Controlled Software Systems

Software systems generally suffer from a certain fragility in the face of disturbances such as bugs, unforeseen user input, unmodeled interactions with other software components, and so on. A single such disturbance can make the machine on which the software is executing hang or crash. We postulate that what is required to address this fragility is a general means of using feedback to stabilize these systems. In this paper we develop a preliminary dynamical systems model of an arbitrary iterative software process along with the conceptual framework for stabilizing it in the presence of disturbances. To keep the computational requirements of the controllers low, randomization and approximation are used. We describe our initial attempts to apply the model to a faulty list sorter, using feedback to improve its performance. Methods by which software robustness can be enhanced by distributing a task between nodes each of which are capable of selecting the best input to process are also examined, and the particular case of a sorting system consisting of a network of partial sorters, some of which may be buggy or even malicious, is examined

Altitude free-jet investigation of dynamics of a 28-inch-diameter ram-jet engine

The dynamic response of a 28-inch-diameter ramjet engine was investigated for flight Mach numbers of 2.35 and 2.50 and altitudes of 50,000, 60,000 and 65,000 feet

Experimental Investigation of Diffuser Pressure-ratio Control with Shock-positioning Limit on 28-inch Ram-jet Engine

The performance of a control system designed for variable thrust applications was determined in an altitude free-jet facility at various Mach numbers, altitudes and angles of attack for a wide range of engine operation. The results are presented as transient response characteristics for step disturbances in fuel flow and stability characteristics as a function of control constants and engine operating conditions. The results indicate that the control is capable of successful operation over the range of conditions tested, although variations in engine gains preclude optimum response characteristics at all conditions with fixed control constants

Oxygen isotope analysis of corals from the Gulf of California and the Gulf of Panama: application and implications for coral-based paleoclimate reconstructions [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): Coral-based reconstruction of past variability of sea surface conditions is improving our understanding of the tropical ocean-atmosphere system. We present oxygen isotope records from corals collected near the tip of Baja California (Baja) and the Gulf of Panama (Saboga)

An investigation of Chromatium vinosum high-potential irondashsulfur protein by EPR and Mossbauer spectroscopy; evidence for a freezing-induced dimerization in NaCl solutions

The high-potential irondashsulfur protein (HiPIP) from Chromatium vinosum contains a cubane prosthetic group that shuttles between the [4Fe-4S]3+,2+ states. We find that the EPR spectra from this protein can be explained as a sum of two components, a major one with g=2.02; 2.04; 2.12, and a minor one with g=2.04; 2.07; ~2.13. In the presence of 0.1-2.0 M NaCl, freezing induces polymerization of the protein (presumably dimers), which is detected as intercluster spindashspin interaction in the EPR. The observed spindashspin interactions are interpreted as being due to two very similar dimeric structures in an approx. 1:2 ratio. Computer simulation of the X- and Q-band EPR spectra shows that the z-components of the g-tensors in each dimer pair must be co-linear, with center-to-center distances between the clusters of ~ 13 A and ~ 16 A. Inspection of possible dimeric structures of C. vinosum HiPIP by standard molecular graphics procedures revealed that the Fe/S cluster is exposed toward a flattened surface and is accessible to solvent. Moreover, the Fe/S clusters in two HiPIP molecules can easily achieve a center-to-center distance of ~ 14 A when approaching along a common 3-fold axis that extends through the S4 sulfur atom of the cubane; the z-component of the EPR g-tensor is co-linear with this symmetry axis.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29129/1/0000168.pd

Changes in Chemical Composition of ISS Archive Water Samples from Collection to Analysis

No abstract availabl