Ktisis Collection: Δημοσιεύσεις σε συνέδρια/ Conference papers

Sensor fault detection with low computational cost : a proposed neural network-based control scheme

Sat, 29 Oct 2011 22:58:59 GMT

Title: Sensor fault detection with low computational cost : a proposed neural network-based control scheme

Authors: Michail, Konstantinos; Deliparaschos, Kyriakos M

Abstract: The paper describes a low computational power method for detecting sensor faults. A typical fault detection unit for multiple sensor fault detection with modelbased approaches, requires a bank of estimators. The estimators can be either observer or artificial intelligence based. The proposed control scheme uses an artificial intelligence approach for the development of the fault detection unit abbreviated as ‘i-FD’. In contrast with the bank-estimators approach the proposed i-FD unit is using only one estimator for multiple sensor fault detection. The efficacy of the scheme is tested on an Electro-Magnetic Suspension (EMS) system and compared with a bank of Kalman estimators in simulation environment.

Dynamic assessment of a frp suspension footbridge

Wed, 29 Oct 2008 22:58:59 GMT

Title: Dynamic assessment of a frp suspension footbridge

Authors: Votsis, Renos; Stratford, Tim J.; Chryssanthopoułos, Marios K.

Abstract: In the past decade, the vibration serviceability of slender footbridges has become the subject of serious investigation. Despite the advantages that FRP materials offer in bridge engineering such as higher strength-to-weight ratio and ease of installation, their use in the construction of slender footbridges has raised concerns with regard to their dynamic response, due to the reduced mass and stiffness of these materials compared with their conventional counterparts. In this paper, the dynamic assessment of a FRP suspension footbridge (the Wilcott footbridge) is described. This is performed using dynamic field testing supported by finite element (FE) modelling: the field testing on the bridge produced values for frequencies, mode shapes and damping which were consequently used to calibrate the FE model. Using the calibrated FE model it was shown that the influence of semistructural or non-structural elements, such as parapets, on the dynamic properties of the structure can be significant. The dynamic response of the structure due to human excitation was also measured during the test. The results confirmed that suspension footbridges built from FRP materials are susceptible to vibrations induced by pedestrians. The response levels of the investigated bridge are lower than the threshold levels specified in the relevant code of practice.

Navigation functions in topologically complex 3-D workspaces

Sat, 29 Oct 2011 22:58:59 GMT

Title: Navigation functions in topologically complex 3-D workspaces

Authors: Loizou, Savvas

Abstract: Navigation Functions constructed according to the Koditschek-Rimon construction require the workspace to be topologically simple, i.e. homeomorphic to a sphere world. This paper proposes the first provably correct construction of Navigation Functions in 3D workspaces that are topologically complex. To achieve this construction, an extension of the recently introduced Navigation Transformation is proposed, that can handle any workspace and obstacle topology that can be categorized under the Classification Theorem of orientable 2-manifolds. The constructed Navigation Function is based on an underlying harmonic potential, that is guaranteed by construction to be free of local minima, hence tuning free in that aspect. In addition to the theoretical guarantees, a case study is presented along with a non-trivial computer simulation to demonstrate the effectiveness of the proposed solution. © 2012 AACC American Automatic Control Council).

Closed form navigation functions based on harmonic potentials

Fri, 29 Oct 2010 22:58:59 GMT

Title: Closed form navigation functions based on harmonic potentials

Authors: Loizou, Savvas

Abstract: This paper proposes a new class of smooth closed form Navigation Functions that are derived from harmonic functions. The resulting functions are by construction free of local minima. Utilizing the underlying structure of harmonic functions a tuning controller is proposed to establish the non-degeneracy of critical points. The construction of this new class of Navigation Functions was made possible due to the recently introduced Navigation Transformation. In addition to the theoretical guarantees, the effectiveness of the proposed Navigation Functions is demonstrated through non-trivial computer simulations with systems with first and second order dynamics in a non-trivial workspace.