DYNAMICS OF WASHING MACHINES: MBS MODELING AND EXPERIMENTAL VALIDATION

Paper in proceeding, 2007

As the competition amongst washing machine manufacturers is steadily increasing the urge for improvement of washing machine performance is bigger than ever. To help pushing the limits of spin speed and efficiency, in this paper the results of experimental studies and mathematical modeling of a washing machine are presented. The model describes a horizon-tal axis washing machine with suspension as a multi-body system. In the model the drum, the rotor and the container are modeled as rigid bodies. The main suspension consists of four identical struts connected between the bottom of the drum and the bottom of the machine. Each strut comprises an upper rubber bushing, a friction damper with a built-in coil spring and a lower rubber bushing which transmits the force to the bottom plate. The whole machine stands on four rubber feet. The commercial multi-body system software MSC.ADAMS was used to develop the model from design drawings. A test rig comprising sensors measuring transmitted force, as well as accelerations and movement of the drum has been built and is described in detail. In the paper results from both experimental and modeled data are pre-sented. The conditions for the performed experiments and simulations were spinning from 0 to 1400 rpm with an imbalance of 0.3 attached to the drum wall. Comparison of obtained results of simulations and measurements show good agreement of drum movement and agreement on level of force output under the tested conditions. Resonances have been found, modeled and their sources have been identified. The biggest resonance has been clearly recognized and identified to be at between 10.5 Hz and 12.5 Hz giving dynamic force amplitude of 40% of the force at static conditions. Future work which needs to be performed, including extension of suspension damper model, is outlined.