Use of data-driven design for the development of knob-shaped handles in the context of impedance measurements.

It can be inferred from hand-arm impedance analyses that the grip forces of users have a great influence on the transmitted vibrations. To determine this influence on test benches, the state of research suggests a cylindrical measuring handle. Since this shape is not suitable for all power tool handles, we develop a design for a knob-shaped measuring handle. The grip force applied to an orbital sander was measured in a test person study. The recorded data was combined with a 3D scan and evaluated by an algorithm which determined the separation plane of the measuring handle to integrate the force sensors. This plane is perpendicular to the vector of the subjects' grip forces. Furthermore, it divides the knob-shaped handle of the sander primarily vertically. The determination of the separation plane enables the design of a knob-shaped measuring handle for grip force measurement to analyze the hand-arm impedance of an overlying hand position.

Analysis of factors influencing the productivity of hammer drilling - user forces, human fatigue, drilling direction, and drill bit.

In order to be able to develop a hammer drill with which the user can work as ergonomically and productively as possible, the relevant influencing factors must be known. In addition to the unknown influence of the drilling direction, there is a lack of understanding of the relations between user forces, human fatigue, and productivity. To analyze these relations, an experiment was carried out with 15 professional users. First, the influence of feed force, drilling direction, and drill bit on the rate of penetration was examined. Taking into account the rate of penetration and human fatigue, it was then investigated which of the three feed forces produces the highest productivity. Furthermore, the lateral forces applied by the participants during the drilling process were analyzed. Based on the study, it was found that the drilling direction (p < .001, r = -0.198) and the drill bit type (p < .041, r = -0.16) have a significant influence on the rate of penetration. Moreover, it was found that the rate of penetration tends to increase with higher feed forces, however, the theoretical cumulative drilling meters decrease when taking user fatigue into account. Finally, the experiment showed that the participating professionals applied lateral forces (Mdn = 16.7 N) of 13% to the feed force when working with a hammer drill. On the basis of this knowledge, investigations can be done to analyze the influences of lateral forces on the drilling process. The findings help drill and hammer drill manufacturers in testing and development processes. For craftsmen, on the other hand, the knowledge helps to perform the task as ergonomically and time-efficiently as possible.