The eyes and ears of the smart factory

Cyber-physical systems need to be aware of their surroundings. That is only possible with sensors which are becoming more and more intelligent as Industry 4.0 advances.

Sensors are indeed the sensory organs of Industry 4.0, because without them production plant would be deaf and blind. The trend towards decentralisation in automation – culminating (for the time being) in the Smart Factory – is driving the demand for more and more smart sensors. In its recent study “Sensor Trends 2014”, the German Association for Sensors and Measurement AMA found that previously quite simple sensors are increasingly being developed into more highly integrated and intelligent sensor systems. And the range of functionality which sensors provide is continually increasing: they perform their own error correction computations, monitor themselves, or have their own communications interfaces. In distributed sensor networks, they are even able to generate their own power, using energy harvesting to draw power from light, heat or vibration.
Image processing and the associated imaging sensors play a key role in Industry 4.0. Production and imaging are already closely interlinked today. Image processing systems collect, interpret and evaluate data. With appropriate configuration and preparation, they are able to identify trends and potential sources of defects in the production process at an early stage. The possible applications for image processing systems will increase even more in future, in areas such as classic quality assurance procedures, automated parts feed, completeness monitoring, and in helping robots to see.

MEMS in focus

Thanks to their capabilities and their compact form factor, micro-electro-mechanical systems (MEMS) are a key factor for Industry 4.0. They are tiny devices usually combining one or more sensors, actuators and control electronics on a single chip. MEMS sensors contain micro-structures made of silicon which shift when their housings are moved even fractions of a thousandth of a millimetre, and change their electrical properties as a result. That change can be measured, and converted into a data stream. State-of-the-art MEMS sensors are able to measure an increasingly wide range of variables – such as pressure, acceleration, rotary motion, mass flow or the earth’s magnetic field – in a single module, and are becoming steadily more intelligent too.

Only relevant information is transmitted

They are tiny, with some components measuring just four micrometres – that’s a seventeenth of the breadth of a human hair. Because micro-mechanical sensors transmit only weak electrical signals, the modules house integrated electronics alongside the sensor – or in some cases even directly on the same chip. The electronics unit processes the small signals, amplifying them and converting them into digital data. This enables MEMS sensors to send data directly to control units. Dedicated software is enabling MEMS increasingly to evaluate data as well as merely processing signals. The aim is not to transmit raw data, but only the actually relevant information. So instead of lots of measurements, only limit values or disturbance variables are sent. Here’s an example: Whereas conventional temperature sensors continuously transmit the current temperature, a smart sensor only reports if a critical temperature is exceeded. That is a key factor in minimising network data volumes, especially in view of the large number of interconnected cyber-physical systems in the Smart Factory.

A key technology

MEMS units comprising sensors, signal processing, power supply and transmitter components are now so small, energy-saving and cheap that billions of them can be deployed. Consequently, MEMS represent the key technology when it comes to interconnecting the Internet of Things. They have found a strong market in recent years particularly in smartphones and tablets. But for MEMS also to be used in the industrial environment, they must be made more robust.

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