Analysis and design of quadratic parameter varying (QPV) control systems with polytopic attractive region

© . This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/This paper proposes a gain-scheduling approach for systems with a quadratic structure. Both the stability analysis and the state-feedback controller design problems are considered for quadratic parameter varying (QPV) systems. The developed approach assesses/enforces the belonging of a polytopic region of the state space to the region of attraction of the origin, and relies on a linear matrix inequality (LMI) feasibility problem. The main characteristics of the proposed approach are illustrated by means of examples, which confirm the validity of the theoretical results.Peer ReviewedPostprint (author's final draft

Characterization of seabed properties from Scholte waves acquired on floating ice on shallow water

Seismic surveying of the coastal areas in the Arctic is best facilitated during wintertime when the sea ice is land‐fast. This eases the logistics of the operation and assures that there is no damage made to the vulnerable tundra. Seismic experiments on floating ice on shallow water performed in a fjord in Svalbard in the Norwegian Arctic show prominent Scholte waves. The dispersion relation of Scholte waves can provide the shear wave velocities of the seabed sediments. Scholte wave data can potentially be obtained when the seismic source and geophone receivers are both placed on top of the floating ice. However, the Scholte wave data become more distinct by using an air gun lowered some metres below the ice. A rock physics model based on a two‐step differential effective medium scheme has been tuned to predict seismic properties found for very loose sediments, among these very high P‐wave to S‐wave velocity ratios. The rock physics model enables us to convert seismic velocities obtained from Scholte wave data to quantitative estimates of the sediment composition

Fault tolerant control of uncertain dynamical systems using interval virtual actuators

This is the peer reviewed version of the following article: Rotondo D, Cristofaro A, Johansen TA. Fault tolerant control of uncertain dynamical systems using interval virtual actuators. Int J Robust Nonlinear Control. 2018;28:611–624, which has been published in final form at https://doi.org/10.1002/rnc.3888. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.In this paper, a model reference fault tolerant control strategy based on a reconfiguration of the reference model, with the addition of a virtual actuator block, is presented for uncertain systems affected by disturbances and sensor noise. In particular, this paper (1) extends the reference model approach to the use of interval state observers, by considering an error feedback controller, which uses the estimated bounds for the error between the real state and the reference state, and (2) extends the virtual actuator approach to the use of interval observers, which means that the virtual actuator is added to the control loop to preserve the nonnegativity of the interval estimation errors and the boundedness of the involved signals, in spite of the fault occurrence. In both cases, the conditions to assure the desired operation of the control loop are provided in terms of linear matrix inequalities. An illustrative example is used to show the main characteristics of the proposed approach.Peer ReviewedPostprint (author's final draft

Fault tolerant control of uncertain dynamical systems using interval virtual actuators

This is the peer reviewed version of the following article: Rotondo D, Cristofaro A, Johansen TA. Fault tolerant control of uncertain dynamical systems using interval virtual actuators. Int J Robust Nonlinear Control. 2018;28:611–624, which has been published in final form at https://doi.org/10.1002/rnc.3888. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.In this paper, a model reference fault tolerant control strategy based on a reconfiguration of the reference model, with the addition of a virtual actuator block, is presented for uncertain systems affected by disturbances and sensor noise. In particular, this paper (1) extends the reference model approach to the use of interval state observers, by considering an error feedback controller, which uses the estimated bounds for the error between the real state and the reference state, and (2) extends the virtual actuator approach to the use of interval observers, which means that the virtual actuator is added to the control loop to preserve the nonnegativity of the interval estimation errors and the boundedness of the involved signals, in spite of the fault occurrence. In both cases, the conditions to assure the desired operation of the control loop are provided in terms of linear matrix inequalities. An illustrative example is used to show the main characteristics of the proposed approach.Peer ReviewedPostprint (author's final draft

Diagnosis of Wing Icing Through Lift and Drag Coefficient Change Detection for Small Unmanned Aircraft

This paper address the issue of structural change, caused by ice accretion, on UAVs by utilising a Neyman Pearson (NP) based statistical change detection approach, for the identi cation of structural changes of xed wing UAV airfoils. A structural analysis is performed on the nonlinear aircraft system and residuals are generated, where a generalised likelihood ratio test is applied to detect faults. Numerical simulations demonstrate a robust detection with adequate balance between false alarm rate and sensitivity.© 2015 Published by Elsevier Ltd. This is the authors' accepted and refereed manuscript to the article. Locked until 2017-01-01

Implementation and Test of a Low Cost GBAS Subset Airborne Receiver Experimental Platform for UAVs

A Ground Based Augmentation System (GBAS) provides differential corrections to Global Navigation Satellite Systems (GNSS) using VHF Data Broadcast (VDB) Equipment. This paper discusses development and test of an experimental low cost single frequency (GPS L1) GBAS airborne subset receiver. The objective of the design is to serve as a research platform for implementation and testing of different measurement processing architectures and integrity monitoring algorithms suitable for new potential user types such as small Unmanned Aerial Vehicles (UAVs). Following a brief discussion of platform architecture and component selection, preliminary results from a field test carried out near to the Zurich airport with its operational GBAS Approach Service Type (GAST) C GBAS station are presented. We describe an experimental low cost prototype receiver to implement GBAS with adaptive carrier smoothing for a single frequency Global Positioning System (GPS) and VDB receiver. Our results demonstrate how low cost GNSS receiver sensitivity can be increased to make it more robust, and viable via additional signal analyses focused on the receiver RF block’s messages.publishedVersio

Case study of combined marine- and land-based passive seismic surveying in front of Nordenskiöldbreen outlet glacier, Adolfbukta, Svalbard

Glaciers generate seismic waves due to calving and fracturing, meaning that recording and following event classification can be used to monitor glacier dynamics. Our aim with this study is to analyse seismic data acquired at the seabed and on land in front of Nordenskiöldbreen on Svalbard during 8 days in October 2020. The survey included 27 ocean bottom nodes, each equipped with 3 geophones and a hydrophone, and 101 land-based geophones. The resulting data contain numerous seismic P-, S- and Scholte wave events throughout the study period, as well as non-seismic gravity waves. The recording quality strongly depends on receiver type and location, especially for the latter wave types. Our results demonstrate that hydrophones at the seabed are advantageous to record gravity waves, and that Scholte waves are only recorded close to the glacier. The Scholte waves are used to estimate the near-surface S-wave profile of the seabed sediments, and the gravity wave amplitudes are converted to wave heights at the surface. We further discuss possible source mechanisms for the recorded events and present evidence that waves from earthquakes, calving and brittle fracturing of the glacier and icebergs are all represented in the data. The interpretation is based on frequency content, duration, seismic velocities and onset (emergent/impulsive) and is supported by source localization, which we show is challenging for this dataset. In conclusion, our study demonstrates the potential of using seismic observations for detecting glacier-related events and provides valuable knowledge about the importance of survey geometry, particularly the advantages of including seabed receivers in the vicinity of the glacier