Dynamic stiffness evaluation for reconfigurable machine tools including weakly non-linear joint characteristics

A systematic procedure is proposed to evaluate the dynamic characteristics of design alternatives for a reconfigurable machine tool (RMT). The procedure is intended to be used in an automated design environment where various design alternatives are generated by kinematic synthesis based on a given task and specification. The evaluation procedure makes use of a substructuring method called non-linear receptance coupling. The coupling method includes the effects of weakly non-linear compliant joints through the use of describing functions for the non-linearities involved. Experimental data obtained from a prototype RMT are used to show the validity of the coupling method. To demonstrate the utility of the proposed evaluation procedure design alternatives are generated based on a lumped parameter model of the RMT and examined with respect to the proposed criteria. It is shown that joint non-linearities may affect dynamic stiffness considerably. It is also shown that the suggested criteria can distinguish various design alternatives with respect to their expected dynamic behaviour.