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The research project: Battery-free sensors for the smart factory of the future

Networked Embedded Systems (NES) are the backbone of many sensor and communication systems today. Thanks to the awardee of the second ABB Research Award in Honor of Hubertus von Grünberg they now could become even more important. Flexibly designed, low-cost and battery-free sensor devices will help collect enormous amounts of data to accelerate the digital transformation of industries.

The world is full of them: NES comprise a class of devices that combine sensing and communication capabilities. Over the past two decades, there has been an enormous growth of NES devices to enable various sensing and Internet of Things (IoT) applications.

And this is just the beginning. The past several years have seen a significant interest to develop various machine learning techniques and apply them to different domains. An essential aspect of these tools and techniques is the collection and processing of large amounts of data. “This, we believe, will significantly accelerate the growth of NES even more”, says Ambuj Varshney, the 33-year-old awardee of the renowned ABB Research Award in Honor of Hubertus von Grünberg. “Machine learning techniques often require collection and processing of large amounts of data. For many applications, this would require a massive deployment of sensing devices.”

The ABB Ability Smart Sensor for low-voltage motors was introduced in 2016. It was the first data-gathering device for electric motors in an industrial environment and needs batteries to sense and transmit the data.

Many predictions already state that billions of such devices will be deployed in the near future. Though, as promising as the applications are, there is one major problem: Today NES devices are usually energy-constrained and commonly comprise of battery-operated, bulky devices which require a significant effort to deploy and maintain. “This severely challenges the vision of large-scale deployment of sensor devices for data collection”, the young researcher realized early on. 

The reasons for this are diverse: firstly, battery-operated devices require a significant maintenance effort to replace exhausted batteries. Secondly, batteries can also negatively impact the physical environment, as they often employ toxic chemicals which require proper disposal. Moreover, the devices’ large form factor also restricts their deployment, particularly in small or hard to reach places. And finally, of course, the most critical constraint for reliance on batteries is their considerable energy consumption.

What gives hope in this context, are some developments in which the current winner of the ABB Research Award had a significant share. Over the past few years, individual sensors have become exceedingly energy efficient. Today microphones or accelerometers consume just tens of microwatts of power. However, a typical radio transceiver used to communicate sensor readings, such as ZigBee, BLE or WiFi, remains energy-hungry, consuming several orders of magnitude of more power for their operation. “To overcome this limitation, we have made several significant contributions to the emerging area of backscatter communication”, Varshney says.

Backscatter technique enables wireless transmissions at much lower power consumption compared to conventional radios. It achieves this by using the fact that reflecting or absorbing wireless signals such as TV broadcast or cellular signals is much less energy expensive compared to locally generating them.

Based on this principle, as part of his doctoral thesis at the Department of Information Technology at Uppsala University, Varshney developed a system called “LoRea”. LoRea generates narrow bandwidth backscatter transmissions, which help it exploit receiver sensitivity and achieve large communication range. Further, it delegates carrier generation and reception to separate devices such as smartphones or WiFi routers, which improves the scalability of the system. Finally, it keeps the backscattered signal and the carrier signal apart in frequency, which helps to reduce the self-interference without requiring complicated and expensive hardware.

The development of LoRea represents hard work built on many failures and difficulties. But finally, Varshney´s presentation of LoRea at the highly selective ACM Conference on Embedded Networked Sensor Systems (SenSys 2017) was a complete success. “We have demonstrated the ability to communicate to distances as large as kilometres while just consuming tens of microwatts of power”, the young scientist explains. “This represents several orders of magnitude improvement in energy efficiency over conventional radio transceivers. The low-power consumption required for transmissions enables us also to radically rethink the design of NES.”

The potential to build flexible designed, low-cost and battery-free sensor devices finally opens up a wide range of valuable options for the future. “We imagine our sensors could be in the form factor of stickers operating on harvested energy from the ambient environment such as light, radio frequency signals or vibrations and could be placed on surfaces and other areas to enable extensive data collection”, the awardee describes his vision. 

Flexible, battery-free sensors could significantly drive the digital transformation of industries, as large scale deployment of such sensors will enable the collection of almost unlimited amounts of data to help with various machine learning tools as well as artificial intelligence methods. That is why Varshney is particularly pleased to receive the honored research award from a company that is a global leader in the ongoing transformation already. “Enabling smart factories is definitely one use case that we want to target”, he explains, when asked about which further research projects he will invest the US$ 300,000 grant over the next three years. “My expectations from this award is that it enables me to leverage more than a century of experience of ABB in developing innovative technologies”.