Vibration reduction in vertical washing machine using a rotating dynamic absorber

Most of the vibration problems in vertical washing machines occur during the water extraction process (spinning stage), when high unbalance forces act on the system. The unbalance forces result from the combination of high rotating velocities and the uneven, and unpredictable, mass distribution of the clothing in the machine basket. Hence, reducing system response to unbalance is a way of improving not only the vibration performance of the washing machine, but also customer satisfaction. One of the ways of reducing system response is via dynamic absorbers which work in a passive way, thus not requiring a control system, but excitation frequency must be constant and known. In this work, a rotating vibration absorber is tested for reducing lateral vibration during the spinning process of an 8-kg capacity washing machine. The vibration absorber is mounted on the rotating basket of the machine, whirling at the same velocity of the basket. A model for the rotating dynamic absorber is proposed and coupled to the model of the washing machine. Numerical and experimental results are obtained concerning unbalance response in the conditions of the spinning process. A comparison between the systems with and without the rotating dynamic absorber shows significant reduction in the lateral vibration of the machine basket when the absorber is used. Because the efficiency of vibration absorbers does not depend on the amplitude of excitation forces, vibration reduction occurs irrespective of the unbalance condition.