MODELING AND OPTIMIZATION OF WASHING MACHINE VIBRATION DYNAMICS DURING SPINNING

Licentiate thesis, 2009

A washing machine as a product is familiar to almost everyone in all developed countries. This thesis deals with the dynamics of modern washing machines of household type. From technical and scientific point of view a modern washing machine is an example of electromechanical system with many degrees of freedom, sensors and controller making the machine a mechatronic system. The aim with the work presented in this thesis is to develop mathematical and computational models of a washing machine of modern type to be used in system dynamics analysis and in optimization routines to make improvements in the machine suspension structure. This should be done by changing geometry, changing the passive component parameters or/and incorporate active or semi-active mechanical actuators. The aim is also to evaluate existing and to find new suspension concepts and corresponding control strategies (if applicable) to reduce the vibration output of a washing machine to its surroundings whilst keeping or increasing load capacity. From this point of view experimental validation of the developed models and proposed concepts is one of the important tasks of the project. In the thesis a MBS model of a commercial front loaded washing machine implemented in MSC. Software/Adams is presented and used for analysis of the vibration dynamics. Several test rigs for component and whole-system tests have been developed and are presented. The experimental data obtained are used for validation of developed mathematical and computational models. A methodology for optimization of washing machine vibration dynamics is presented together with results of a structural optimization of some features of a future suspension system. The existence and possibility of utilization of semi-active control for the current suspension system are investigated. A suggested solution has been validated by incorporation into a washing machine suspension system a magnetorheological damper. The semi-actively controlled suspension has shown good potential for reduction of the vibration output of a washing machine. Key words: Washing machine, Suspension system, Modeling, Experiment, Spinning, Vibration dynamics, Optimization, Semi-active control, Magnetorheological damper.