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Certain off-road vehicles are equipped with a type of clutches referred to as differential locks. A driver may engage/disengage these locks to switch between two distinct operating modes: the closed mode is charac- terized by greater off-road traversability, while the open mode allows better manueverability. Many drivers lack the education and experience required to correctly judge the terrain ahead of the vehicle and therefore engage/disengage the locks in a suboptimal fashion. An automatic differential locking strategy is hence desired. This paper compares three such traction control algorithms of the on/off variety, all derived from the same underlying kinematic vehicle model but each relying on the availability of different output signals. The validity of the kinematic model and the algorithms’ sensitivity to the values assumed by a couple of unobservable states, the wheel slip angles, is in- vestigated by comparison to an existing articulated hauler model in ADAMS— an environment for simulation of multibody dynamics. Godkänd; 2010; 20110628 (ysko) Optimerad framkomlighet för tunga terrängfordon

The contents of this thesis can be divided into two main parts. The first one is the development of an identification methodology for the modelling of complex industrial processes. The second one is the application of this methodology to the curl and twist problem. The main purpose behind the proposed methodology is to provide a schematic planning, together with some suggested tools, when confronted with the challenge of building a complex model of an industrial process. Particular attention has been placed to outlier detection and data analysis when building a model from old, or historical, process data. Another aspect carefully handled in the proposed methodology is the identifiability analysis. In fact, it is rather common in process modelling that the model structure turns out to be weakly identifiable. Consequently, the problem of variable selection is treated at length in this thesis, and a new algorithm for variable selection based on regularization has been proposed and compared with some of the classical methods, yielding promising results. The second part of the thesis is about the development of a curl predictor. Curl is the tendency of paper of assuming a curved shape and is observed mainly during humidity changes. Curl in paper and in paperboard is a long-standing problem because it may seriously affect the processing of the paper. Unfortunately, curl cannot be measured online, but only in the laboratory after that an entire tambour has been produced. The main goal of this project is then to develop a model for curl and twist, and eventually to implement it as an on-line predictor to be used by the operators and process engineers as a tool for decision/control. The approach we used to tackle this problem is based on grey-box modelling. The reasons for such an approach is that the physical process is very complex and nonlinear. The influence of some inputs is not entirely understood, and besides it depends on a number of unknown parameters and unmodelled/unmesurable disturbances. Simulations on real data show a good agreement with the measurement, particularly for MD and CD curl, and hence we believe that the model has an usable accuracy for being implemented as an on-line predictor. QC 20100928

This thesis describes a grey-box model for the dimensionalstability properties (i.e. curl and twist) of the carton boardproduced at AssiDomän Frövi paper mill in Sweden.AssiDomän Frövi AB is one of Sweden major cartonboard manufacturer, and produces some 350000 ton of board peryear. Curl is defined as the departure from a at form, and it mayseriously affect the processing of the paper. For this reason,customers impose quite restrictive limits on the allowedcurvatures of the board. So, it is becoming more and moreimportant to be able to produce a carton board with a curlwithin certain limits. Due to the economic significance of thecurl problem, much research has been performed to find sheetdesign and processing strategies to eliminate or reducecurl. The approach we used to tackle this problem is based ongrey-box modelling. The reasons for such an approach is thatthe physical process is very complex and nonlinear. The inuenceof some inputs is not entirely understood, and besides itdepends on a number of unknown parameters andunmodelled/unmesurable disturbances. One of the main part of the model is based on classicallaminate theory which is used to model the dimensionalstability of multi-ply board. The main assumption is that eachlayer is considered as an homogeneous elastic medium. The model is then complemented with a sub-model forunmodelled/umeasurable disturbances which are described asstates of a dynamical system, and estimated by means of anextended Kalman filter. The simulated curvatures show a general agreement with themeasurements. However, the prediction errors are too large forthe model to be used in an effective way, and a bigger efforthas to be carried out in order to improve the physicalsub-models. A chapter of this thesis discusses the modelling of thewet-end part of the paper machine with Dymola, a modelling toolfor simulation of large systems based on Modelica language. NR 20140805