Stability analyses of a vertical axis automatic washing machine with a hydraulic balancer

This paper analyzes non-linear vibration characteristics associated with the spin drying process of a vertical axis automatic washing machine with a hydraulic balancer. A two-ball model is employed to describe the effect of the hydraulic balancer and a mathematical model is built for the washing machine. Based on a rotating coordinate transformation, this model is then converted to an autonomous form for stability analyses. The continuation package AUTO [1] is employed and two unstable regions of the spin drying process denoted by M and N are identified. The unstable region N is discussed in detail because it has an essential effect on the spin drying process. At last, the existence of the unstable region N is proved by both simulations and experiments.