Electrohydraulics: Boon or bane?
It's difficult to think very far ahead without weighing in on the role of hydraulics and electronics integration. Some say purely electrical systems will one day completely replace fluid power. Others insist electrics will instead play a vital role in keeping fluid power meaningful.
Labus thinks fluid power will see continued electrical integration. "The intelligence provided by electronics will continue to form the basis for smart fluid power systems. For example, using low-cost automotive sensor technology can improve the intelligence of fluid power systems."
But Bud Trinkel, fluid power consultant and frequent contributor to H&P, thinks too much emphasis is put on the mingling of the two technologies. "It's a great thing, but it's not what will save fluid power ... it will replace it in industry in all but high force applications," he says.
Roland Keller, market application engineer for Bosch Rexroth, feels momentum is clearly on the side of electrical integration. "Using smart hydraulics enables you to position and control force at a lesser cost than electromechanical drives," he says. He notes that in linear applications, cylinders are superior to ballscrews. Ballscrew wear affects the ability to control an axis, degrading system performance.
"Typical wear items of cylinders are rod seals, which don't affect system performance," he explains. "If used with gland drain ports, the seal wear can be monitored and become part of preemptive maintenance."
Products get in the mix
Prof. Hubertus Murrenhoff of IFAS in Aachen, Germany, says more product integration is inevitable. "We'll see valves with integratedsensors and electromechanicaldrives. Digital electronics itself will become more integrated, but will also be integrated into the next level — meaning the cylinders and other actuators." Murrenhoff feels this can also translate into fluid power systems with micro turbines to drive pumps in mobile equipment or the integration of pumps and electric motors.
Johnson also sees many components going electronic. "The use of electronics to control will continue to grow and become the dominant mode of performing logic functions," he says. "The use of hydraulic logic will continue to decline and will be used where it's the only feasible method."
Johnson also believes that electrohydraulically controlled pumps will replace valves as the control method of choice because of the inherent energy loss of valves.
"Electronically controlled, variable-displacement pumps will benefit from reduced manufacturing costs born of economies of scale, forcing the retirement of valves as controllers." Johnson sees a potential for huge return on investment, which will encourage pump designers to develop new control methods while increasing their dynamic bandwidths. This could bring these pumps into even the most critical applications.
Book notes a side benefit to electrohydraulics. "With electrohydraulics being the norm and user satisfaction and productivity paramount, haptic [tactile] control sticks with a more natural correspondence to the task will be expected and provided. Engineered feel and safety constraints will be automatically provided."
Eye on the environment
Environmental effects are at the forefront of everyone's mind these days, especially in fluid power, where the potential damage is great if a system is improperly designed. But designing in environmental safety doesn't have to mean sacrificing performance. Johnson thinks a whole new world of low-pressure water hydraulic systems will arise, including consumer products — all made from plastics and composites. He feels some new materials will find their way into oil hydraulics as they demonstrate greater stress capabilities.
Along the same lines, Labus argues that the use of nontraditional fluids with improved properties in the areas of bulk modulus, vapor pressure, and thermal conductivity could improve component/ system dynamic response, enhance cavitation resistance allowing a wider bandwidth, and shrink or eliminate the need for a separate heat exchanger.
Book notes the mitigation of noise and leakage are equally important. "Some applications will be lost due to these issues before it happens," he says. "Active control of pump pulsations might be viable as an alternative."
Whatever happens, environmental issues will still be a strong controller of technology development in the future because sustainable growth is a global issue, says Koskinen. "The use of water-based fluids and water hydraulics will increase slowly due to tightening environmental laws and insurance costs. Also growing production of water hydraulic components will decrease prices, which are still quite high."