Hydraulic Systems Get Smarter, Less Noisy

Add Brains to the Brawn: Machine Builders Incorporate Electronics Into Hydraulic Controls

By Hank Hogan

Long the muscles of machines, hydraulic systems were seen as a dirty, noisy, and not smart. That's changed, though, with the incorporation of electronics into hydraulic controls.

"It's not dirty anymore," says Jan Komsta, manager of new technologies and simulations, Bosch Rexroth "It's not noisy anymore. It's intelligent. It's a high-tech drive technology."

As example, Komsta points to one of the company's Sytronix SVPs (speed variable pumps), in which a variable-frequency drive allows the pump speed to be adjusted on-the-fly to match the flow demand. Indeed, the pump only runs when needed. The payoff is that both pump and motor operate more often at a preferred working point.

SEE ALSO: Electro-Hydraulic Motion Controllers Enable Breakthroughs in Machine Productivity and Reduce Lifecycle Costs

Another benefit can be elimination of proportional control valves, which is possible because of the high dynamic response of the pump. It can accelerate from a standstill to 3,000 rpm in 50 ms, Komsta says. That same control can help reduce noise by as much as 20 dB by allowing the pump to run at a slower speed during partial load and pressure-holding operation. This reduction can make it possible to carry on a conversation nearby.

At Eaton, hydraulics are made more intelligent through improvements in the valves and their controllers. In particular, this is evident in smart control valves, says Steve Zumbusch, Eaton's advanced systems director. "The company's ZTS valve has onboard electronics and sensors," he says. "This combination allows important parameters such as pressure and flow to be monitored internally. The valve itself can take action to bring these back to a set point, and adjust them as needed in order to get a machine to perform desired actions, or to operate a system at an optimum."

The valve has built in algorithms to handle this. It also offers machine builders the ability to configure the valve to a particular situation by adjusting such parameters as ramp rate. Beyond that, machine builders can also add their own control touch via valve programmability.
"We give them some white space on the valve control as well, so they can write their own algorithms, if they choose to," Zumbusch says.

This unused capacity also provides another plus. The space gives Eaton room to load firmware updates and upgrades, so the devices have a degree of future proofing. New algorithms and capabilities can be rolled out to devices in the field, keeping them technologically fresh.

Such a capability means that, over time, hydraulic system performance might be made more efficient, while offering greater accuracy and control over movement. Often, greater control and more efficiency are the two most desired improvements in hydraulics, according to Zumbusch.

Where and how to add intelligence has to be balanced against other considerations. For instance, Atlantic Industrial Technologies, a custom hydraulic system builder, is installing a 94-louver system as a moving sun shade for a large central skylight in a building on the campus of Florida Polytechnic University in Lakeland, Fla.

Moving a louver can take up to 50 tons of force, and Atlantic Industrial chose to manage this with dumb components that communicate with a sophisticated centralized controller. This moves against the trend toward greater local intelligence, and was done, says Atlantic, for a particular reason. "These components are going to be exposed to harsh weather on top of the building," says Thomas Behling, Atlantic Industrial's controls engineer.

Given this environment, the decision was made to keep the valves simple, and put the intelligence in a remote, watertight and corrosion-resistant NEMA 4X box, unaffected by Florida's weather, which can include the occasional hurricane.

The valves for the project come from Sun Hydraulics. Sometimes the intelligence can be built into hydraulics without the use of electronics, according to Sun's Rich Arter. He reports that the company has a new line of mechanically self-settling products called LoadMatch that dynamically react to changes in conditions, such as when a lift is fully loaded going up, but carries a much lighter burden when coming down.

Intelligently and automatically adjusting for these changes can bring some significant performance benefits, Arter says. "Early tests demonstrate up to 20% fuel savings are achievable compared to more conventional approaches."

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