Measurement and Evaluation of the Interaction Forces of Specific Hammer Drilling Strategies to Determine Requirements for Dynamic Hand-Arm Models

Abstract

In the development of hand-held technical systems, it is crucial to consider the relevant subsystems (user, technical system, environment). As there are confounders for each of the three subsystems, acquiring the necessary knowledge about their interaction for product development is difficult. Test benches can replace individual subsystems with functionally equivalent structures and are subject to the actual loads from the applications like power tools. To reduce human influence, mechanical hand-arm models are used. These models exhibit vibration characteristics that can be proven to be equivalent to those of the human hand-arm system via mechanical impedance (MI) measurement, provided they are exposed to identical vibration excitations. Current research considers the influence of grip force to be more significant than factors such as anthropometry or push force. However, the influence of push and grip forces, which vary over time, on mechanical impedance is not considered. The objective of this work was to investigate this influence. To investigate this influence, a study is conducted with ten test subjects who used a hammer drill. The grip and push forces were measured. The test subjects performed three drilling strategies from the skilled crafts sector: one hole, a vent hole and five holes in row. The data show a grip force for single drilling that increases constantly during drilling. The same effect was also found for vent drilling. An opposite trend for the grip force was measured for five holes drilled in a row. Here, the grip force decreases on average over the five holes. These results form the starting point for developing the 'IPEK Hand-Arm Model of the Saurbier Generation' (IPEK-HAMS), as they reveal the fundamental requirements for a dynamic hand-arm model. In particular, these include the recording of time-varying force curves, which is a prerequisite for deriving the vibration behavior of the human hand-arm system. Building on the state-of-the-art HAM, this model enables the reproducible evaluation of power tools during application-oriented operation by taking grip and push forces that change over time into account.

Keywords: Hand-arm-vibration, Interaction Forces, Hand-arm-model, Power-tools, Grip And Push Forces, Human-machine-system

DOI: 10.54941/ahfe1007978