Jared M. Porter

INTERFACE PRESSURE AND THE PREDICTION OF CAR SEAT DISCOMFORT

The technique of interface pressure measurement has generated considerable interest in the automotive industry as a method, which could be used to predict driver discomfort during the development of prototype seat designs. Two repeated measures experiments were carried out to evaluate the practical application of the technique. The variables of foam density and posture were used to create discomfort, the whole emphasis of the work being to generate results with real-world applicability. A clear, simple and consistent relationship between interface pressure and driving discomfort was not identified. Future studies using this technique should provide information regarding such factors as gender, body mass, anthropometric data, posture and foam hardness due to the confounding nature of these variables.

SEAT PRESSURE MEASUREMENT TECHNOLOGIES: CONSIDERATIONS FOR THEIR EVALUATION

Interface pressure measurement has generated interest in the automotive industry as a technique which could be used in the prediction of driver discomfort for various car seat designs, and provide designers and manufacturers with rapid information early on in the design process. It is therefore essential that the data obtained are of the highest quality, relevant and have some quantitative meaning. Exploratory experimental work carried out with the commercially available Talley Pressure Monitor is outlined. This led to a better understanding of the strengths and weaknesses of this system and the re-design of the sensor matrix. Such evaluation, in the context of the actual experimental environment, is considered essential.

Using HADRIAN for eliciting virtual user feedback in 'design for all'

Abstract ‘Design for all’ is an approach to product, environment or service design that aims to maximize the usability of a particular design. However, a key concept of this approach is not to tailor designs to the user in a bespoke fashion, but rather to provide a single solution that accommodates the needs of all users, including those who are older or are disabled. In order to support the designer/design team in ‘design for all’ a computer aided design and analysis tool has been developed. The tool, known as HADRIAN, has been developed to address two critical factors. The first factor is the provision of accurate and applicable data on the target users, including a broad spectrum of size, shape, age and ability. The second factor is an efficient and effective means of utilizing the data for ergonomics evaluations during the concept stages of design. HADRIANs database and task analysis tool work in combination with the existing human modelling system SAMMIE. The system as a whole allows assessment of a design against the population in the database, providing a means to elicit some of the feedback that might be gained by real user trials at a stage in the design process when physical mock-ups and user group selection would be prohibitively time consuming and expensive.

A TASK BASED 'DESIGN FOR ALL' SUPPORT TOOL

Abstract The ‘design for all’ philosophy promotes the development of products that meet the requirements of a broader section of the population, including those who are older or disabled, to minimise the need for bespoke designs and individual customisations. Such an approach begins to meet the needs of a population containing an ever increasing proportion of these excluded groups, whilst providing opportunities to manufacturers to maximise the available market for any given product. Most design activity embodies some form of task analysis that involves identifying users and the tasks they perform. Computer based human modelling systems are becoming increasingly important in this task analysis role combined with the established ergonomics technique of fitting trials, in which a product or environment is evaluated through trials using a carefully selected user group. This research addresses the lack of existing data necessary for the accurate representation of human form and capability in the older and disabled populations for use in these modelling systems. A small-scale survey is being undertaken to collect this important information. In addition, existing modelling systems in this area rely on expert ergonomics knowledge in performing task based analysis, which in addition can be a time consuming and repetitive task. Methods are being developed to streamline this process and to place the emphasis on good design and ergonomics principles as opposed to ‘driving’ the system. These methods involve the development of a simplified process for computer based task analysis and a means of determining the percentage accommodated by any given design. Further research will eventually focus on extending the data collection, refining the task model and look at a means of suggesting design solutions in response to the analysis results.

Exercise and sleep behaviour A questionnaire approach

This study investigated the effects of daily physical activity levels, including the time of day when the activity was taken and subject fitness, upon sleep behaviour using questionnaires. Three questionnaires were designed, namely a subject screening questionnaire and pre-sleep and post-sleep questionnaires. The pre-sleep questionnaire was completed immediately before the subjects retired to bed and was used to record their daily activity levels and to assess pre-sleep tiredness. The post-sleep questionnaire was designed to obtain information concerning the quantity and quality of sleep as well as post-sleep tiredness. Eighty volunteers were selected, following screening for ill-health and sleeping problems, and were asked to complete the sleep questionnaires for seven consecutive days. Fifty-one returned their questionnaires and a total of 332 days of data were used for analysis. Subjects were enlisted from sports centres, and all reported a measurable degree of variation in their daily activity levels ...

Computer aided modelling of the human spine

Abstract The human spine is the main structure to support human body weight and external loads, to allow the torso to reach to a variety of positions and to protect the spinal nervous system. Lumbar back pain and disorders may be related to spinal curvature and disc pressure, and it is an ultimate objective of the work reported here to include consideration of these issues in computer aided ergonomics design systems for evaluating a wide range of situations including manual handling and car seat design. Several methods from structural analysis have previously been used to model the human spine, principally lever and beam structures, but these have frequently shown discrepancies when compared with experimental data. As an alternative, an arch representation for the spine is considered here and allows the establishment of a criterion for the failure of the spine that may be useful in determining absolute maximum loading conditions. However, the main interest is in submaximal loading conditions where damage or discomfort are the concerns rather than fracture. It is proposed that the location of the thrust line in relation to the centre-line of the spine is a useful predictor, and optimization techniques have been developed to find the ‘best-fitting’ thrust line for the statically indeterminate structure. Further work is concerned with adding muscle and ligament forces to the loading system of the model, extension of the two-dimensional model into three dimensions, validation against experimental data and integration with the SAMMIE computer aided ergonomics design system.

Spine modelling and ‘safe to use’ equipment design

Computer human modelling has for sometime been developed and used but even the most sophisticated commercially available human modelling packages do not have an effective spine model. Although some packages have a geometric representation of the spine, they have no analytic or design application functionality. On the other hand back pain and back injuries are well-known to be a major problem and lead to substantial costs to manufacturing industry through enforced absenteeism. The main objective is to provide an answer to the need for a design tool which can consider the range of postures and predict the loads that will be imposed on the spine.