Modelling the effect of sensory dynamics on a driver’s control of a nonlinear vehicle

In previous work a linear model of driver steering control was developed which takes account of human sensory dynamics and limitations. In this paper various approaches to modelling a driver’s control of a nonlinear vehicle are compared. In contrast to research focussed on modelling the optimal driver, the aim of this work is to develop a realistic model of driver steering behaviour. Simulations were run to compare various nonlinear state estimators and controllers. In general a trade-off was found between simulation time, which could also represent mental load, and controller performance. Experiments are planned to compare the results of these simulations against measured steering behaviour from human drivers

Rail efficiency: Cost research and its implications for policy

In this paper we first consider alternative measures of efficiency. We explain why simple partial productivity measures are inadequate as the basis of overall measures of efficiency, and outline two alternative approaches. The first is technical efficiency - the degree to which output is maximised for a given level of inputs (or conversely inputs are minimised for a given output) - and the second is cost efficiency, the degree to which costs are minimised for a given level of output. Cost efficiency implies technical efficiency but also allocative efficiency - choosing a cost minimising mix of inputs. We explain why we prefer to measure cost efficiency, both in terms of what governments and regulators are interested in and in terms of practical data problems. We then examine applications of cost function analysis to two areas. The first is rail privatisation in Britain. British experience has seen a large increase in traffic, but also a similar increase in costs. We review attempts to understand and explain both the increase in passenger train operating cost and infrastructure cost using cost function analysis. The second is European rail reform. Countries in Europe have adopted a wide variety of approaches to rail reform, and studies using a mix of European and other countries should be able to shed light on the important question of what works best in different circumstances. Finally we consider how efficiency analysis techniques need to develop in future to address current weaknesses and tackle new challenges

Inverting Supervised Representations with Autoregressive Neural Density Models

We present a method for feature interpretation that makes use of recent advances in autoregressive density estimation models to invert model representations. We train generative inversion models to express a distribution over input features conditioned on intermediate model representations. Insights into the invariances learned by supervised models can be gained by viewing samples from these inversion models. In addition, we can use these inversion models to estimate the mutual information between a model's inputs and its intermediate representations, thus quantifying the amount of information preserved by the network at different stages. Using this method we examine the types of information preserved at different layers of convolutional neural networks, and explore the invariances induced by different architectural choices. Finally we show that the mutual information between inputs and network layers decreases over the course of training, supporting recent work by Shwartz-Ziv and Tishby (2017) on the information bottleneck theory of deep learning.Comment: Accepted for publication by AISTATS 201

A review of human sensory dynamics for application to models of driver steering and speed control.

In comparison with the high level of knowledge about vehicle dynamics which exists nowadays, the role of the driver in the driver-vehicle system is still relatively poorly understood. A large variety of driver models exist for various applications; however, few of them take account of the driver's sensory dynamics, and those that do are limited in their scope and accuracy. A review of the literature has been carried out to consolidate information from previous studies which may be useful when incorporating human sensory systems into the design of a driver model. This includes information on sensory dynamics, delays, thresholds and integration of multiple sensory stimuli. This review should provide a basis for further study into sensory perception during driving.This work was supported by the UK Engineering and Physical Sciences Research Council (EP/P505445/1) (studentship for Nash).This is the published version. It first appeared from Springer at http://dx.doi.org/10.1007/s00422-016-0682-x

Fields of conflict: journalism in the construction of Sydney as a global city 1983-2008

This thesis examines the relationship between media reporting and Sydney's construction as a global city over the period 1983-2008. Following Friedmann, Sassen and others it views globalisation as a process of consolidation in command and control functions in the global economy, financed through the massive creation of liquidity via expanding debt, and enabled by producer services located in a network of ‘global cities’. Theoretically, it considers major debates in urban sociology and the sociology of journalism and seeks to reconcile approaches in the two fields to achieve a theoretically coherent framework for analysis that can encompass the changing political economy of Sydney and the ways in which media representation is related to this process. In globalisation studies it examines the meta-theoretical post-industrial/ network society arguments associated with Bell and Castells, and compares them with the neo-Marxist spatiality theses associated with Harvey and Arrighi, and Foster and Magdoff on financialisation. It then discusses the global cities literature in the context of Australian urban studies. In media sociology it starts with the debate about source-journalist power relations. Following Schlesinger and Benson, it offers a critical evaluation of Bourdieu's field theory. It then adopts a framework drawing on Bourdieu, together with Harvey and Lefebvre on spatiality and Gell on temporality, to consider the complexity of dynamic power relations between journalists and other sources of power. There follow two complementary empirical case studies of communication contests over (i) debt-induced growth in the Sydney residential real estate market and (ii) the demutualisation of the largest Australian general insurer, NRMA Insurance Group Ltd. The case studies examine the differing field relations of journalistic reporting and investigation of those activities in select newspapers. It argues that the journalism was deeply engaged with and/or influenced by the interests and activities of its sources in the primary field of concern, with power being exercised in both directions but overall in the structural interests of powerful sources, though not necessarily in their personal interests. The thesis concludes with an assessment of Bourdieu's field theory in the light of the analyses, and advocates a more reflexive understanding of relations within and among fields, particularly with respect to orthodoxy/heterodoxy, autonomy/heteronomy and symbolic violence

Measurement and Modelling of Human Sensory Feedback in Car Driving

Data supporting this thesis is available at https://doi.org/10.17863/CAM.9741With the growing complexity of vehicle control systems it is becoming increasingly important to understand the interaction between drivers and vehicles. Existing driver models do not adequately characterise limitations resulting from drivers’ physical systems. In particular, sensory dynamics limit the ability of drivers to perceive the states of real or simulated vehicles. Therefore, the aim of this thesis is to understand the impact of sensory dynamics on the control performance of a human driver in real and virtual environments. A new model of driver steering control is developed based on optimal control and state estimation theory, incorporating models of sensory dynamics, delays and noise. Some results are taken from published literature, however recent studies have shown that sensory delays and noise amplitudes may increase during an active control task such as driving. Therefore, a parameter identification procedure is used to fit the model predictions to measured steering responses of real drivers in a simulator. The model is found to fit measured results well under a variety of conditions. An initial experiment is designed with the physical motion of the simulator matching the motion of the virtual vehicle at full scale. However, during more realistic manoeuvres the physical motion must be scaled or filtered, introducing conflicts between measurements from different sensory systems. Drivers are found to adapt to simple conflicts such as scaled motion, but they have difficulty adapting to more complicated motion filters. The driver model is initially derived for linear vehicles with stochastic target and disturbance signals. In later chapters it is extended to account for transient targets and disturbances and vehicles with nonlinear tyres, and validated once again with experimental results. A series of simulations is used to demonstrate novel insights into how drivers use sensory information, and the resulting impact on control performance. The new model is also shown to predict difficulties real drivers have controlling unstable vehicles more reliably than existing driver models.This work was funded by the UK Engineering and Physical Sciences Research Council (EPSRC), under studentship EP/P505445/1

Vertical plane response of surface ships in close proximity towing

The purpose of this thesis is to analyze the vertical plane response of surface ships in close proximity towing. The problem is formulated by using the heave and pitch equations of motion in regular waves. The vertical motion of the leading and trailing ship attachment points is calculated. The relative motion between these points is then matched through a notional spring/damper model of the connection. This allows calculation of the complete response amplitude operators for the two ships in terms of their relative motion and connection force. Parametric studies are conducted in terms of connection spring and damper characteristics, speed, and sea direction. Regular wave results are extended in standard fully developed random seas. A notional example provides insight into future studies necessary to validate the close-proximity towing concept.http://archive.org/details/verticalplaneres109451099