Pareto Optimization of a Nonlinear Tuned Mass Damper to Control Vibrations in Hand Held Impact Machines

摘要

Large amplitude vibrations from hand held impact machines might bring serious health problems for users in long term. Here, a vibration absorber which works based on the nonlinear tuned mass damper concept is applied to mitigate unpleasant vibrations in a hand held impact machine. A global sensitivity analysis is carried out using multiplicative dimensional reduction method to scrutinize the effects of different components on the hand held impact machine dynamics response and attenuate the number of input parameters for optimization. Based on the global sensitivity analysis results, the nonlinear tuned mass damper components are chosen as the design parameters subject to optimization. A multiobjective optimization problem is formulated and solved using genetic algorithm to reduce vibrations and total weight of the machine. The Pareto optimized solutions are robust against the exciting force amplitude and frequency. The global sensitivity analysis results revealed that it is possible to run the simulations with a constant exciting force amplitude and extend the obtained solutions for the case with a variable exciting force amplitude while the same order of accuracy in the results can be observed. This significantly reduced the computational burden of the optimization. Closed form expressions for the optimal values of the tuned mass damper parameters as well as system response in terms of the auxiliary mass are developed by using the nonlinear least squares method. The results revealed that the proposed technique can significantly suppress the vibrations induced by the hand held impact machine. This makes it possible for users to operate the machine for a longer time period with lower health risks.