Error minimising gradients for improving cerebellar model articulation controller performance

In motion control applications where the desired trajectory velocity exceeds an actuator’s maximum velocity limitations, large position errors will occur between the desired and actual trajectory responses. In these situations standard control approaches cannot predict the output saturation of the actuator and thus the associated error summation cannot be minimised.An adaptive feedforward control solution such as the Cerebellar Model Articulation Controller (CMAC) is able to provide an inherent level of prediction for these situations, moving the system output in the direction of the excessive desired velocity before actuator saturation occurs. However the pre-empting level of a CMAC is not adaptive, and thus the optimal point in time to start moving the system output in the direction of the excessive desired velocity remains unsolved. While the CMAC can adaptively minimise an actuator’s position error, the minimisation of the summation of error over time created by the divergence of the desired and actual trajectory responses requires an additional adaptive level of control.This thesis presents an improved method of training CMACs to minimise the summation of error over time created when the desired trajectory velocity exceeds the actuator’s maximum velocity limitations. This improved method called the Error Minimising Gradient Controller (EMGC) is able to adaptively modify a CMAC’s training signal so that the CMAC will start to move the output of the system in the direction of the excessive desired velocity with an optimised pre-empting level.The EMGC was originally created to minimise the loss of linguistic information conveyed through an actuated series of concatenated hand sign gestures reproducing deafblind sign language. The EMGC concept however is able to be implemented on any system where the error summation associated with excessive desired velocities needs to be minimised, with the EMGC producing an improved output approximation over using a CMAC alone.In this thesis, the EMGC was tested and benchmarked against a feedforward / feedback combined controller using a CMAC and PID controller. The EMGC was tested on an air-muscle actuator for a variety of situations comprising of a position discontinuity in a continuous desired trajectory. Tested situations included various discontinuity magnitudes together with varying approach and departure gradient profiles.Testing demonstrated that the addition of an EMGC can reduce a situation’s error summation magnitude if the base CMAC controller has not already provided a prior enough pre-empting output in the direction of the situation. The addition of an EMGC to a CMAC produces an improved approximation of reproduced motion trajectories, not only minimising position error for a single sampling instance, but also over time for periodic signals

'Voyaging in': colonialism and migration

A major reference chapter on the history of the literature of colonialism and migration 1945-70. The book marks an intervention into conventional histories of British Literature. The chapter illustrates and analyses the influential formation of alternative modernities by migrant writers resident in Britain during this period; it also extends the gaze to the period before 1945 earlier in the twentieth century. Maps new ways of reading literary history; broad and wideranging discussion of migration during this period

Reservoir quality of Cenozoic carbonate buildups and coral reef terraces

Almost half of SE Asia's considerable hydrocarbon reserves are contained in carbonates. The majority of these reservoirs are Miocene buildups up to tens of kilometres across. However, with the exception of a few fields, there is little detailed data on how local depositional and diagenetic conditions influence the considerable heterogeneities in reservoir quality often encountered. This study focuses on factors influencing the facies, diagenetic and reservoir variability of comparable Modern, Quaternary and Neogene reef associated deposits from the Tukang Besi Archipelago, Central Indonesia.The Archipelago includes large atolls, a number of smaller buildups and 4 main islands each with modern rimmed shelves or fringing reefs. On the islands, over ten late Neogene and Quaternary coral reef terraces have been uplifted to maximum heights of ~300 m. Analysis of the modern deposits allows initial reservoir potential to be assessed and related to local environmental conditions. The influence of diagenesis on final reservoir quality is evaluated for the depositional facies exposed in the uplifted terraces. The overall spatial distribution of effective porosity across the area is strongly dependent on local energy conditions, water depth, carbonate producers, size of atolls or islands, climate and local meteoric diagenetic processes. This evaluation of spatial variability in carbonate reservoir characteristics provides much needed analogue data as the hydrocarbon industry focuses on improving recovery from existing fields and exploring for new reserves

Scottish literature: second renaissance

No abstract available

Ending the century: literature and digital technology

Book synopsis: This Cambridge History is the first major history of twentieth-century English literature to cover the full range of writing in England, Scotland, Wales, and Ireland. The volume also explores the impact of writing from the former colonies on English literature of the period and analyses the ways in which conventional literary genres were shaped and inflected by the new cultural technologies of radio, cinema, and television. In providing an authoritative narrative of literary and cultural production across the century, this History acknowledges the claims for innovation and modernization that chracterise the beginning of the period. At the same time, it attends analytically to the more profound patterns of continuity and development which avant-garde tendencies characteristically underplay. Containing all the virtues of a Cambridge History, this new volume is a major event for anyone concerned with twentieth-century literature, its cultural context, and its relation to the contemporary