Sven Dahlman

A cube model for the classification of work with hand tools and the formulation of functional requirements

In an interdisciplinary research project, a model, visualized as a cube, was developed for the classification and analysis of work with hand tools and for communication of different ways of solving problems related to manual handling. The dimensions of the cube are demands of force, precision and time. Each dimension is divided into three levels of low, moderate and high demands respectively. Preliminary limits are proposed for acceptable and non-acceptable use situations and for situations that have to be investigated further. Using a case study of plate shears as a starting point, various measures of improving the position in the cube are discussed. The hand tool, the workplace, the work organization as well as the user of the hand tool are included in the analysis.

An approach to ergonomics evaluation of hand tools

Based on current knowledge of cumulative trauma disorders in the hand and forearm, related to the use of hand tools, an analysis was undertaken of variables to be considered in ergonomics evaluation of hand tools. Measurement methods were developed and an evaluation station was implemented. Measurement methods are physical, physiological or psychophysical. They focus on the tool, and on the effect of typical use of the tool on the operator. The evaluation station serves as a resource in the development, selection, and testing of tools for a given purpose.

Application of usability testing to the development of medical equipment. Usability testing of a frequently used infusion pump and a new user interface for an infusion pump developed with a Human Factors approach

Abstract In medical care, the infusion pump is one of the most common pieces of technical equipment often involved in incidents due to handling. In order to improve usability and reduce errors, a new user interface for an infusion pump has been designed based on an analysis of observations, interviews, heuristic evaluation, reported incidents and theory about mental capacity and human error. The purpose of this study was to determine whether or not the new interface would reduce the number of handling-errors and problems, and how it could be further improved. For this purpose usability tests were performed by 18 nurses from three different hospital wards. The results showed that the number of handling problems were reduced for the new interface compared to the existing interface, but the number of errors was still high. The tests indicated a need to further improve the new interface in terms of spring-loaded modes where the users are only in the desired mode as long as they actively hold down a button. In identifying user requirements for medical equipment it was found important to use different data collection techniques. In this study it was further found that the nature of the information from the different user groups in usability tests can differ widely. The experienced users had the competence and self-confidence to be critical and suggest improvements based on their practical experience. Whereas the novice users were important since they encountered most of the serious problems and made the most mistakes. Relevance for industry There is a need to develop viable techniques to enable manufacturers of medical equipment and hospital personnel to critically specify and evaluate usability qualities when formulating user requirements for new medical equipment.

Ergonomic development work: co-education as a support for user participation at a car assembly plant. A case study.

This study deals with the design, trials and evaluation of a co-education programme at the Volvo Uddevalla plant in Sweden. Involving operators, manufacturing engineers and managers, the programme served as a support for the creation of a participatory ergonomics process, intended for continuous use at the plant. It consisted of a basic ergonomics knowledge package, and a dialogue model defining the roles and relations of actors involved. As a practical part of the programme, trial development projects were also carried out by the participants. The main and long term objective of the project was to start the participants cooperating in a continuous change and development process on the shop-floor. The outcome of the co-education programme was evaluated immediately after the first two regular courses, and, as a longterm follow-up, after seven subsequent courses shortly after the closing of the Uddevalla plant. The co-education programme was shown to be successful. Later on, the expertize of both operators and manufacturing engineers became obvious to everyone at the plant, and the cooperation between operators and manufacturing engineers increased steadily. The main conclusion drawn was that the co-education programme is a good starting point for a process of participation and industrial change work. However, in order to get a permanent impact, the whole organization must nurse and nourish the further development, and implementation of the process.

Setting the Requirements for a User-Friendly Infusion Pump

The infusion pump is a commonly used piece of equipment at the Intensive Care Unit. The pumps often are from different manufacturers and have different handling characteristics. The ICU is a dynamic environment, with periods of calm interrupted by periods of very high activity and mental load. Infusion pumps are often involved in reported incidents. The purpose of this study was to set requirements for a user interface for an infusion pump, using a systematic human factors approach. The method used consisted of field studies at an ICU, a critical evaluation of two pumps presently used at this ICU and an analysis of reported incidents which involved infusion pumps. Both pumps in the evaluation had a number of latent errors. Two types of incidents relating directly to the user interface were found, both of which could be traced back to latent errors. A number of requirements were set with the purpose of reducing the risks of the two types of incidents occurring and reducing the mental load of the user. Using these requirements, a new interface for an existing volumetric pump was designed.

Articulation at shoulder level - A pilot experimental study on car seat comfort

This article reports on a pilot experimental study aimed at a first evaluation of the introduction of an articulation in the upper part of the seat backrest. The idea of introducing this articulation sprang from prevention of whiplash injuries and this study tentatively assesses its potential for improvement in comfort. This was done considering a pre-defined articulation height. A height for the articulation of 43.5 cm above the H-point of a reference seat was theoretically deduced based on a population with an average sitting height of 88 cm. Participants evaluated the articulated seat in comparison with the reference seat. Twelve participants were divided into three groups of sitting height. In a laboratory environment subjective comfort evaluations and preferred values of deployment of the articulation and of counter-tilting of the headrest were registered. Driving on the roads completed and validated the laboratory assessments. The reference seat was deemed less comfortable for the participants with short and medium sitting height than for the tall ones. There was a notable improvement in comfort for most of the medium and short sitting height participants when using the articulated seat. The articulation was fully deployed by most participants.

Usability Evaluation of a New User Interface for an Infusion Pump Developed with a Human Factors Approach

In medical care, the infusion pump is one of the most common pieces of technical equipment and it is often involved in handling-incidents. In order to improve usability and reduce errors, a new user interface for an infusion pump has been designed with a human factors approach. The purpose of this study was to determine if the new interface could reduce the number of handling-errors and problems, and to find out if the interface needed to be further developed. For this purpose usability tests were performed with nurses at three different hospital wards. The results showed that the number of mode errors and arisen problems were reduced for the new interface compared to the existing interface. However, the usability tests showed that there is still a potential to improve the new interface further. The results also showed that the number of errors was very high when handling these infusion pumps. This is an indication of that this area is important to study further. A conclusion was that usability testing is an important complement when redesigning interfaces with a human factors approach.

Evaluation of Methods, Approaches and Simulation Quality in the Experimental Evaluation of Car Seat Comfort and Functionality

This paper presents methodology, approaches and simulation actually used in the context of human factor studies designed to build knowledge on comfort and functionality of car seats. Backgrounds are literature and two own experimental studies. The methodology presented involves comparative studies with variation of one or several seat design factors. Scales for subjective evaluation of seat comfort and functionality, completing questionnaires and interviews are evaluated. Also compared are approaches to the design of sitting trials, involving real or simulated conditions. The simulations are qualified, in terms of what actually works. Physical data collection alternatives, namely, moving and still images and interface pressure data, are also commented upon. Anthropometric and other criteria for the selection of subjects are discussed together with sample size. Alternatives for tasks to be performed by trial persons are also discussed, along with the degree of freedom left to subjects. Alternative designs of standardized driving routes are compared. Driving tests validated the results arrived at in the laboratory tests, with both tests designed with methods and approaches presented in the paper.