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A revolution is under way in the world of hydraulics

Tampere University of Technology
Simple on/off valves are revolutionising the world of hydraulics. Smart digital systems based on these valves offer significantly improved response times and reliability compared to conventional load-sensing technology, as well as major energy savings, according to Adjunct Professor Matti Linjama.

Digital hydraulic technology was invented at the Tampere University of Technology’s department of intelligent Hydraulics and automation (IHA) some 10 years ago. inspired by professor Matti Vilenius’ call to ‘think differently’, Matti Linjama, now an adjunct professor at IHA, came up with the idea of applying digital principles to the world of hydraulics and using simple on/off valves controlled via software instead of traditional proportional valves.

“Rather than steplessly regulating the opening of a valve, digital hydraulics is based on valves that are either on or off – open or closed,” explains Linjama. “When a sufficient number of these valves are connected in parallel, you have a wide range of options. Determining which valves are open and which are closed is handled by the software.”

Valves connected in parallel in this way can completely replace conventional analogue servo and proportional control valves.

“A single package of small on/off valves can do the work of all the hundreds of different types of valves manufacturers offer today.”

This loader developed at IHA is the first piece of mobile equipment based on digital hydraulics. All its boom movements are operated by digital hydraulic lines.

Reliable and energy-saving

Digital hydraulic systems are significantly faster and more reliable than conventional technology. Simple on/off valves are very durable and can operate in even dirty mediums. The built-in redundancy that comes from connecting large numbers of these valves in parallel means that a production process, for example, does not need to be shut down simply because of one faulty valve. Repair work can easily be carried out during the next regular overhaul.

Studies by Linjama’s research team have also shown that digitalisation can save on energy consumption, and significantly so.

“We expected some savings, but our tests have confirmed reductions of as much as 30-40%. Conventional valves are always a compromise, and compromises waste energy, by definition. A digitally controlled valve, on the other hand, is much more ‘energy-aware’, as it can be optimised to prevailing load requirements.”

Massive savings are possible, with the right computing muscle

Work over the last few years has shown that digital hydraulics can be applied to hydraulic pumps and other equipment as well – to create a virtually lossless hydraulic system that can route just the right amount of hydraulic power to precisely where it is needed in real time. Energy can also easily be recovered in return movements, which can result in valuable fuels savings, particularly in the case of mobile machinery.

“We estimate that 20-40% fuel savings are possible. Machines can also be simpler and lighter. If all mobile machinery were to be digitised, the benefit would be equivalent to cutting the fuel consumption of all the cars on the road by 5-10%. And this can be done without increasing the price of machinery either.”

Controlling valve behaviour is the biggest challenge in digital hydraulics. The number of calculations needed grows exponentially as more on/off valves are added to a system. Computing power is also needed to optimise performance and energy efficiency.

Linjama emphasises, however, that this is compensated for by the fact that digitalisation and smart control systems bring significant improvements in overall performance and efficiency. Procurement costs are also lower, as on/off valves are much cheaper to produce than conventional fine mechanical servo valves.

Digital hydraulic technology can reduce losses by as much as around 70%.

Positive industry response

Industry has already seen the potential benefits offered by digital hydraulics and around 10 companies are currently involved in IHA’s research work.

“One of our partners replaced their conventional hydraulic system with a digital one and was able to achieve energy savings of 98%! They were also able to eliminate the need for a machine room and achieve a solution that was cheaper, more compact and energy-efficient, and offered much better performance as well,” says Linjama.

“Bosch Rexroth is just one of the companies that are investing a lot in digital hydraulics, and this has been reflected in better component availability in the field.”

Pooling engineering expertise

Tampere University of Technology is one of the 11 organisations and 17 companies behind Finnish Metals and Engineering Competence Cluster Oy (FIMECC, www.fimecc.com), an initiative designed to bridge the gap between academic research and the business world.

“As part of FIMECC’s research programme, we’ve produced a series of new-generation digital microhydraulic valves,” says Adjunct Professor Matti Linjama of TUT and a recipient of the annual FIMECC Prize. “Our goal is to achieve a breakthrough in performance, fault tolerance, as well as size and price. Nothing has come up so far that indicates we won’t be able to do so.

”Digital hydraulics research at TUT also takes place through the Academy of Finland’s Generic Intelligent Machine (GIM) Centre of Excellence. Finland’s Strategic Centres for Science, Technology and Innovation – coordinated by Tekes, the Finnish Funding Agency for Technology and Innovation – are public-private partnerships designed to speed up innovation processes by creating new industry clusters and radical innovations.

FIMECC’s strategic research is focused on service businesses, the user experience, global networks, intelligent solutions, and breakthrough materials.

> Katja Ayres
(Published in HighTech Finland 2011)