Intensive research in the field of mathematical modelling of the pneumatic cylinder has shown that its mathematical model is nonlinear and that a lot of important details cannot be included in the model. Selection of the model and the identification method have been conditioned by the following facts:(a) The nonlinear model of the system can be approximated by a linear model with time-variant parameters. (b) There is the influence of the combination of heat coefficient, unknown discharge coefficient and change of temperature on the pneumatic cylinder model. Therefore it is assumed that the parameters of the pneumatic cylinder are random (stochastic parameters). (c) In practical conditions, observations have a non-Gaussian distribution.Due to the abovementioned reasons, it is assumed that the pneumatic cylinder model is a linear stochastic model with variable parameters. The Masreliez-Martin filter (robust Kalman filter) was used for identification of parameters of the model. For the purpose of increasing the practical value of the filter, the following two heuristic modifications were performed:(1) It was adopted that T (k) = 1 holds for the scalar transformation of residuals. (2) Fisher information was approximated by a derivative of the Huber's function.The proposed modifications were confirmed through intensive simulations. In order to provide persistent excitation, V. Filipovic · N. Nedic · V. Stojanovic ( ) the autocovariance function "1/f " of the signal was used.The behaviour of the new approach to identification of the pneumatic cylinder is illustrated by simulations. Robuste Identifikation von pneumatischen Servo-Aktuatoren in der realen SituationenZusammenfassung Intensive Forschung auf dem Gebiet der mathematischen Modellierung des pneumatischen Zylinders hat gezeigt, dass sein mathematisches Modell nichtlinear ist und dass viele wichtige Details nicht in das Modell einbezogen werden können. Die Auswahl des Modells und die Art der Identifikation werden durch folgende Tatsachen bedingt: (a) Das nichtlineare Modell des Systems kann durch ein lineares Modell mit zeitvarianten Parametern angenähert werden. (b) Es besteht ein Einfluss der Kombination von Wärme-durchgangs-Koeffizient, unbekanntem Durchflusskoeffizienten und Änderungen der Temperatur auf das pneumatischen Zylinder-Modell. Es wird daher angenommen, dass die Parameter des pneumatischen Zylinders zufälligen Charakters sind. (c) Unter praktischen Bedingungen haben die Beobachtungsergebnisse eine nicht-Gaußsche Verteilung. Aufgrund der vorgenannten Gründe wird davon ausgegangen, dass das Pneumatikzylinder Modell ein lineares, stochastisches Modell mit variablen Parametern sein muss. Der Masreliez-Martin-Filter (robust Kalman-Filter) wurde für die Identifizierung von Parametern des Modells verwendet. Zur Erhöhung des praktischen Werts des Filters, wurden die beiden folgenden heuristischen Modifikationen durchgeführt: 184 Forsch Ingenieurwes (2011) 75:183-196 (1) Es wird angenommen, dass T (k) = 1 für das skalare Transformation der Residuen hält. (2...

No abstract

No abstract

No abstract

Tin is a rare metal that is essential for making bronze, the defining technology of the Bronze Age. The source(s) of tin for Aegean bronze is undetermined but several small Bronze Age tin mines have been documented in the circum‐Aegean region. The discovery of Bronze Age archaeological sites in West Serbia near a tin placer deposit on the flanks of Mt. Cer led to an investigation of this site as a potential additional Bronze Age tin mine in the region. Geochemical prospecting of stream sediments flowing from Mt. Cer allowed for categorization of streams based on relative tin grade. Tin grade is highest in the Milinska River, a likely combination of a broad catchment area with multiple ore‐bearing tributaries, and a topographic profile that favors the accumulation of placer deposits. A survey of cornfields along the southern pluton margin discovered archaeological sites spanning the Neolithic to the Iron Age. Unlike older and younger sites, those of the Bronze Age were found only along the Milinska and Cernica Rivers where placer tin grades are highest, but appear to be absent where tin is scarce or absent. This suggests that these sites were associated with the exploitation of the tin ore.

No abstract

This paper proposes a method for exponential m-stability analysis of stochastic switched systems. The models, in a finite set of models, are non-linear stochastic models. It is assumed that there is no jump in the state at switching instants and there is no Zeno behaviour, ie, there is finite number of switches on every bounded interval. The stochastic hybrid systems have wide applications: transmission control protocol flows with congestion avoidance and slow-start modes; estimation in distributed networked systems; air traffic control; process control and communication networks for control systems. For analysis of stochastic switched system the multiple Lyapunov functions are used and exponential m-stability is proved. From the main result of the paper: 1) the exponential m1 -stability of stochastic switched systems whereby m1 ∈ (0, m); 2) the stability in probability. The exponentially stable equilibrium of system is relevant for practice because such systems are robust to perturbations.

No abstract