Abstract

Several development objectives need to be considered when developing drill hammers. Besides achieving the highest possible power-to-weight ratio, the health and safety features of the tools are becoming increasingly important. In particular, it must be ensured that the transmission of vibrations to the operator is minimized or lies within the limits of health and safety regulations. Modelling the vibration behavior of drill hammers, there is a strong interaction between the biomechanical operator, the tool and the application. To enable an appropriate prediction accuracy of the vibration level, both the dynamics of the hammering mechanism as well as the dynamics of the operator model must be understood and modelled correctly. Hereby, the complexity of the hand-arm-models reaches from simple 3-mass-spring systems to detailed biomechanical operator models. The number of required input parameters often increases with the complexity of the models. The goal of this study has been to enhance the system understanding of the various model parameters. For this purpose, the system dynamics have been validated based on measurement data capured for different drill hammers, operator poses and anthropometrics. To simulate complex mechanical systems, the multi-body simulation has proven to be an efficient method. In this study, the software Simpack has been used. The computation time for a system time of two seconds took 15 minutes using a single core solver and can be reduced to four minutes computation time using parallel solving on 4 cores. Due to the high dimension of the parameter space, the interactive parameter identification has shown to be error prone as well as the documentation has been cumbersome and therefore often incomplete or difficult to reproduce. In order to choose a more targeted approach, the simulation process has been extended by the automation tool Isight which is able to perform design of experiments, optimizations and sensitivity analysis. Doing so, a better parameter safety and prediction accuracy could be provided.