Mechanical defects in washing machines and dishwashers are set to
be detected more quickly and accurately with a new automatic on-line
system. A multidisciplinary consortium comprising six partners
pooled their skills to produce and test a prototype of the system.
Once commercialised, the system will help improve manufacturers'
competitiveness and provide consumers with appliances that are
quieter and more reliable.
The household appliance manufacturing sector
is one of Europe's leading industries with an annual turnover of
between 25 and 30 billion ECU and 250,000 in its workforce. Some say
that the greatest technological breakthrough this century is in fact
the washing machine. It has significantly reduced the time it takes
to complete the chores of cleaning clothes. More recently, the
dishwasher has released even more of our time.
Due to manufacturing faults, these machines can be noisy. We, the
consumers, do not want to be disturbed from whatever it is we are
doing instead of washing! We also want to put the washing machine on
to run overnight when electricity is cheaper. And we want to be sure
that if we buy a new machine it will work as soon as it's plugged in
and carry on working for as long as possible.
Focus on qualityManufacturers realise this and they have
begun to consider quality control much more seriously. Human checks
have been in operation for years but they have mainly been
end-of-line checks which are inefficient and costly. If a machine
comes off the line with a fault, it takes a long time for someone to
detect the problem and then alter or halt production processes to
fix it. What's more, only a sample of each batch of machines is
tested so machines with faults could end up at the retailer.
Automatic systems for on-line testing of the functional and
electrical aspects of these appliances are available. However, until
recently, there were no solutions for testing the mechanical aspects
of washing machines and dishwashers on-line. The solutions that were
available were not reliable enough and depended too heavily on the
A team of two universities, a research institute and three SMEs
decided to design and build a prototype of an automatic system that
can detect a range of mechanical defects. In washing machines, this
includes missing or loose screws, incorrect shock absorber or
bearing assembly, misalignment of the drum and motor pulley and
incorrect belt tension. In dishwashers, improper spray arm rotation
can be detected.
Good vibrationsThe system consists of three main blocks.
The mechanical workstation automatically picks up the appliance from
the assembly line, lets it go through the testing cycle and then
returns it to the production line for the last stages of the
manufacturing process. The second part is the non-contact optical
sensor network which measures vibrations on several external points
on the washing machine or dishwasher. Finally, a diagnostic expert
system quickly determines whether the machine is defective or fully
functioning. It uses the most advanced digital processing techniques
including features extraction, neural networks and fuzzy logic. In
certain cases, this final system can identify specific faults and
this helps the operator repair the machine.
These computer-assisted diagnostic techniques have previously
been used in medicine, the military and power generation where the
technology has been used in very different ways. The appliances need
to be classified one by one according to vibration measurements in
the shortest possible time. In the other sectors, the system
predicts faults in a continuous monitoring system.
Tapping into a pool of knowledgeBringing together sensor
specialists, system integrators, software developers, integrated
optic chip manufacturers and laser vibration measurement experts
provided the range of skills required to develop the new system
which has been tested extensively. Gino Romiti, the project
coordinator from AEA says, "We may have begun the project on our own
but we wouldn't have had access to nearly as many resources and
competencies without the other partners. We intend to continue to
cooperate with each of the partners and we are already working with
some of them on other projects." The results will feed into other
work as well.
"We intend to use some of the intermediate results in similar
fields, especially for on-line mechanical defects detection in other
industrial products like electrical motors, compressors and pumps,"
continues Eng. Romiti.
All the partners have benefited from their experiences in the
project. "AEA will sell the test stations worldwide after having
engineered them. MIT and TUC will sell the software originating in
this project to us at AEA and also directly to other markets other
than electrical appliances. Similarly, LETI and CSO can do the same
with their vibration sensors," explains Eng. Romiti.
Of course, once the prototype has been developed into a
commercial product, the benefits will be spread more widely.
Appliance manufacturers will be able to increase the quality of
their production, have better control of their manufacturing
processes and thus increase their competitiveness. They can get
closer to their zero-defect goals. And we, the consumer, will be
able to buy quieter and more reliable appliances.