Meaningful Prediction Parameters for Evaluating the Suitability of Power Tools for Usage

Abstract

During the usage of power tools, user and power tool are interacting strongly with each other, which is why the working result depends heavily on the usability of a power tool depending on the application (Suitability of Usage (SoU)). The optimization of power tools, in terms of the user-centered design, therefore aims at an increase of the SoU. So far, the acquisition of the SoU is done within broad application tests, with several users and different application situations. Hereby, problems occur because it is often difficult to find an adequate mix of professional trained participants, which are able to evaluate the SoU objectively. To investigate the differences between professional power tool users and trained non-professional users, a study has been performed. In this study, 20 professional and 19 non-professional users tested power tools (cordless screwdrivers and impact wrenches, three different manufacturer each) and evaluated the handles of these systems according to fourteen test items, divided into an observation and a usage phase. By the use of statistical variance analysis, the captured data has been analyzed to investigate the influence on the evaluation through the usage experience of the users. Results indicates a strong influence within the evaluation categories where evaluations are done which rely on long term experiences, like the evaluation of the distributed force on the fingers. To produce further increase in efficiency and objectivity, a categorical regression by the use of Lasso models has been performed to identify the most meaningful influencing predictors for the SoU level. The investigation is carried out using the example of the evaluation of discomfort on the handle. Results indicates that the most meaningful predictor for the evaluation of the handle is the circumference of the handle at the position of the middle finger.