Scholarly Works - Wolfson College


Recent Submissions

Now showing 1 - 3 of 3
  • ItemOpen Access
    The Mediating role of E-assessment on Student Identity: A Sociocultural Analysis Through the Lens of Figured Worlds
    (2016-05) Westbury, Meg; Westbury, Meg [0000-0001-7443-7959]
    In the 2000s, many UK universities acquired access to Turnitin, an online text-matching system designed to detect cut-and-paste plagiarism. At the university in question, one department allows their students to view Turnitin’s ‘originality reports’ before submitting essays for marking, hoping that Turnitin’s feedback will improve students’ writing. Building on recent calls for more research into students’ perceptions of eassessment, I explore the mediating role that Turnitin’s originality reports plays on two students’ authorship of their identities using the sociocultural framework of identity formation called ‘figured worlds’ (Holland et al., 1998), and Gee’s (2014a, 2014b) related approach to discourse analysis. My findings show that students’ subjectivities are closely bound up, at least in the short term, with their perception of the neutrality and precision of Turnitin. Such findings are useful for framing discussions about links between technology and learning and circumstances which can lead to greater student engagement with eassessment.
  • ItemOpen Access
    Certification of a class of industrial predictive controllers without terminal conditions
    (IEEE, 2014) Dutta, A; Hartley, E; Maciejowski, J; De Keyser, R; Hartley, Edward [0000-0001-5491-229X]; Maciejowski, Jan [0000-0001-8281-8364]
    Three decades have passed encompassing a flurry of research and commercial activities in model predictive control (MPC). However, the massive strides made by the academic community in guaranteeing stability through a state- space framework have not always been directly applicable in an industrial setting. This paper is concerned with a priori and/or a posteriori certification of persistent feasibility, boundedness of industrial MPC controllers (i) based on input-output formu- lation (ii) using shorter control than prediction horizon (iii) and without terminal conditions.
  • ItemOpen Access
    Design and Certification of Industrial Predictive Controllers
    (2014-09-24) Dutta, Abhishek; Maciejowski, Jan; De Keyser, Robin; Ionescu, Clara; Hartley, Edward
    Three decades have passed since milestone publications by several industrial and academic researchers spawned a flurry of research and commercial, industrial activities on model predictive control (MPC). The improvement in efficiency of the on-line optimization part of MPC led to its adoption in mechanical and mechatronic systems from process control and petrochemical applications. However, the massive strides made by the academic community in guaranteeing stability through state-space MPC have not always been directly applicable in an industrial setting. This thesis is concerned with design and a posteriori certification of feasibility/stability of input-output MPC controllers for industrial applications without terminal conditions (i.e. terminal penalty, terminal constraint, terminal control). MPC controllers which differ in their modelling and prediction method are categorized into three major groups, and a general equivalence between these forms is established. Then an overview on robust set invariance is given as it plays a fundamental role in our analysis of the constrained control systems. These tools are used to give new tuning guidelines as well as a posteriori tests for guaranteeing feasibility of the suboptimal or optimal predictive control law without terminal conditions, which is fundamental towards stability of the closed loop. Next, penalty adaptation is used as a systematic procedure to derive asymptotic stability without any terminal conditions and without using set invariance or Lyapunov arguments. This analysis however is restricted to repetitive systems with input constraints. Then, predictive control without terminal conditions is considered for nonlinear and distributed systems. The invariance tools are extended to switching nonlinear systems, a proof of convergence is given for the iterative nonlinear MPC (NMPC), and a guarantee on overall cost decrease is developed for distributed NMPC, all without terminal conditions. Reference generation and parameter adaptation are shown to be effective mechanisms for NMPC and distributed NMPC (DNMPC) under changing environmental conditions. This is demonstrated on two benchmark test-cases i.e. the wet-clutch and hydrostatic drivetrain, respectively. Terminal conditions in essence are difficult to compute, may compromise performance and are not used in the industry. The main contribution of the thesis is a systematic development and analysis of MPC without terminal conditions for linear, nonlinear and distributed systems.