Estimating unbalance mass of vertical axis washing machine by measuring current ripple of PMSM motor

Abstract

Lately, as the desire for comfortable and pleasant living environments has grown because of improvements in the standard of living, interest in the reduction of vibration and noise of electric appliances has increased. In the case of washing machines, in particular, the drum of the machine rotates at a high speed during the dehydration mode, and thus, the problem of vibration arises. The vibration of rotary machines not only shortens their lifecycle and produces noise, but also causes discomfort to those nearby. Therefore, a great deal of effort has been devoted to reducing this vibration. The load of the washing machine is primarily dependent on the weight of the laundry. However, unbalance mass is not determined as a simple function of the increase in weight. During the washing process, laundry is often driven to one side of the machine because of a tangle. In general, such a change in the load alters the magnitude of the current flowing through the electric motor, and thus, proper control would necessarily depend on the size of the change. Additionally, structural sources of unbalance mass inevitably exist in the steps of designing and manufacturing washing machines and the unbalance mass of the laundry causes the vibration in the spin-dry mode.