New Procedures for Detecting Imbalance in Automatic Washing Machines

New Procedures for Detecting Imbalance in Automatic Washing Machines 

In the most frequently used type of domestic washing machine, the drum containing the washing turns in a suds container. The suds container is spring-mounted in a housing with shock absorbers connecting it to the bottom of the housing in order to attenuate vibrations (Fig. 5.55). 

The easiest way of measuring movement of the suds container is with distance sensors. Chapter 5.5 describes some typical examples. The advantage of these sensors is that they are also used to monitor the washing load. Their drawback is the high price. 

Movement of the suds container always results in a change in length of the springs, thus the same information can also be obtained by measurement of the force at the suspension points of the springs. Up till now, this type of solution has not been used for cost reasons. 

As a result of sensor development in the automotive industry, low-priced acceleration sensors are now available. Acceleration sensors are fundamentally also suited to observing excursion (Fig. 5.57) of the suds container caused by imbalance. However, static measurement of the weight of the washing, as achieved with a distance sensor, is not possible with acceleration sensors. 

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