Development of generation mechanism of synchronous vibration suitable for hand-held vibrating tools (investigation for impact model with two oscillators)

It is known that the hand-arm vibration syndrome characterized by Raynaud's disease is caused by long-term use of hand-held vibrating tools. The purpose of this research is to newly develop vibrating tools utilizing self-synchronized phenomena in order to reduce the hand-arm vibration. In this paper, an elementary model having the generation mechanism of synchronous vibration suitable for a tamping rammer used to compact cohesive soils on the ground is contrived. This model consists of upper and lower blocks coupled by coil-springs, and two rotor-type oscillators are mounted individually on the lower blocks. The nonlinearity due to the impact behavior between the lower block and the ground is approximated by piecewise linear characteristics. The self-synchronized solutions and the stability are analyzed by applying the improved shooting method for impact vibration analysis. The analytical and experimental results confirm that the stable self-synchronized solutions which are able to achieve a good balance between vibration control and excitation exist. It is also proven that the existence region of the stable solutions can be expanded by setting the system parameters appropriately.