Introduction

The research performed by the Perception Enhancement Systems group is based on the premise that many excellent engineering tools exist for designing products and machines, but that difficulties often arise when trying to quantify the interaction between the machines and their human users. Questions arise regarding what missions the machines must perform and regarding how human people respond to the machine’s outputs and emissions.

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The research therefore focuses on the inputs and outputs of the design process, namely the definition of the mission for the machine and the measurement or estimation of the human response to the machine’s stimuli.

The research is organised into four basic sectors which cover the key relevant technologies:

  • mission synthesis algorithms,
  • perception enhancement systems,
  • whole-body comfort evaluation methods and
  • local comfort evaluation methods for the hand-arm system.

Specific research projects are run in each of the four sectors. Funding is from a mixed portfolio of UK national, European Union and direct industrial sources.

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Mission Synthesis

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Vibro-Acoustic Mission Synthesis consists of the analysis of long time histories of acquired vibro-acoustic data with the objective of summarising the main features which affect human perception. All current data recorder technologies available internationally are defeated by the high data sampling rates which are characteristic of these stimulus modalities. A scientific approach is therefore being developed for intelligently selecting and saving the ambient features which affect humans.

Current applications are mostly automotive, but research is also under way to develop algorithms for health & safety monitoring and for medical epidemiological investigations. Several mission-synthesising black-box recorder algorithms have been produced. To date the two most significant are the Mildly Nonstationary Mission Synthesis algorithm (MNMS) and the Wavelet Bump Extraction algorithm (WBE). Both are based on the use of time-frequency wavelet analysis and feature selection methods. Algorithm output consists of both condensed summary signals and the “alphabet” of bump features which underlie the vibro-acoustic emission.

Perception Enhancement Systems

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Vibro-Acoustic Perception Enhancement Systems consist of algorithms or devices for optimising the information flow between machines and their human operators. While the science of virtual reality is well developed, that of perception enhancement systems is far less understood. The goal is to define the key parameters of vibro-acoustic signals which control the human identification of the associated real world scenario. This knowledge is then built into engineering systems which amplify the key environmental phenomena so that humans can better interact with their machines and automated assistants.

The scientific problem is multi-disciplinary, involving elements of receptor physiology, human psychophysics, cognitive psychology, digital signal processing and dynamic systems theory. Research performed to date includes studies of road surface recognition based on vehicle steering feedback, identifying optimal feedback bandwidths and gains. New research includes proposals for perception enhancing features for industrial welding work stations and assembly assistants.

Whole-Body Vibration

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One of the most common human vibration scenarios is that of whole-body vibration, which refers to the those vibration responses which involve extensive regions of the human body and which are caused by vibrational stimuli containing energy at relatively low frequencies, typically less than 100 Hz. An understanding of the human perception of this form of human vibration is important for the design of numerous consumer products and engineering systems, particularly transport systems.

Research performed in this area of human vibration includes the study of the human perception of the intensity and quality of stationary and non-stationary whole-body vibration stimuli. Several psychophysical test protocols are regularly employed including paired-comparisons, magnitude estimation, semantic differential and Borg Scales.

Numerous studies have been performed to determine both the global, and the body part localised, perceptual response to this form of human vibration. Studies performed to date include comparisons of short time and long time perception of whole-body human vibration, the development of Stevens’ Power functions for the perception of fore-and-aft whole-body human vibration and the measurement and modelling of the whole-body human vibration response of small children.

Local Vibration

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The research in the area of local vibration includes studies of the human perception of the intensity and quality of hand-arm vibration stimuli. Several psychophysical test protocols are regularly employed including paired-comparisons, magnitude estimation, semantic differential and Borg Scales. Numerous hand-arm vibration studies have been performed to determine both the global, and the body part localised, perceptual response to hand-arm vibration.

Psychophysical research performed to date has permitted the definition of a frequency weighting for the perception of hand-arm vehicular steering wheel vibration (Ws), and a metric for quantifying the hand-arm perceived intensity of modulated vibration signals of the type occurring in Diesel engined vehicles at idle. Studies of human cognitive response to hand-arm stimuli have been conducted using semantic differential methods to investigate both the language descriptors used by individuals and the dimensionality of the response. Several studies of the human response to combined hand-arm vibration and sound have also been performed. These studies have lead to the definition of a curve of subjective equivalence between the interior sound and the steering hand-arm vibration which occur in road vehicles.