Fluid power 20/20

Pressures to 20,000 psi? No external leaks? Self-tuning systems? Industry experts offer their vision for fluid power's future.

Without a crystal ball, seeing 15 years into the future of fluid power isn't easy. But thinking about tomorrow helps us makes plans for today. That's why H&P interviewed a range of people in the industry — professors, researchers, users, manufacturers, consultants — to find out what they think the future of fluid power holds.

A focus on systems

Some companies are already providing valves with the integrated controller and sensors. The step to the integrated electromechanical drive is already reality, such as with this Bosch Rexroth IAC-P valve.
The trend toward designing around systems, rather than individual components, has been underway for several years. And there seems to be widespread agreement that this trend will continue over the next decade and beyond.

"Systems that are simple to install, connect, and service — as well as components with modularity — are becoming more and more a priority," says Ed Bickel, district sales manager for Bosch Rexroth's Pneumatic Div.



Tom Wanke, Director of the Fluid Power Institute at the Milwaukee School of Engineering (MSOE), sees the complete integration of a hydraulic system into the actuator, including the prime mover, pump, and reservoir for true distributed operation and control.

The key to making this a reality is establishing and maintaining a true partnership between academia and industry, says Jack Johnson, noted author and contributing editor to H&P.

"The NFPA has launched a research program, however, it's focused on traditional academic definitions of what research should consist of, namely product development and enhancement. Industrialists have to understand the future of fluid power is enhanced when the greatest possible number of people understand systems on a quantitive level." This means academics must provide models, as well as modeling methods, that applications engineers can understand and implement with user-friendly software.

Computers and modeling
New design methods will be used in the future, many of which will involve computers to help engineers visualize their work, such as virtual design, virtual prototypes, and virtual testing. These processes will also tie into our increasingly global world, allowing designers and users in separate geographical locations to work on a project, transferring models through email or a computer network.

"A remarkable amount of development costs can be saved by building virtual prototypes instead of real ones. Hydraulically driven machines will develop more modularity, so the most suitable power, transmission, and modules can be easily connected," says Prof. Kari Koskinen of Finland's Tampere University of Technology. "Virtual prototypes also allow the testing of real hardware or software operation before building the whole system."

Jonny Carlos da Silva, of Brazil's University of Santa Catarina, agrees. "Due to the increasing complexity of fluid power systems, especially with integration of electronics and other domains, dynamic simulations will play an important role in improving the design process and reducing cost and time-to-market," he says.

Prof. Tom Labus, MSOE, adds that many competitive technologies have had these types of design and simulation tools for many years. "This has put fluid power at a disadvantage in being able to provide end-users with information other than simple package size and dimensions," he says.

But will all this modeling actually lead to any breakthroughs in the fluid power field? According to Johnson, it will. "Improved modeling will lead to new discoveries, especially regarding system efficiencies and control methods, which will produce system designs that aren't conceivable with the current models taught by our two-and four-year colleges."

Prof. Richard Burton of the University of Saskatchewan in Canada, thinks we're getting there. "With the understanding we have gained over the years from R&D, we have a good handle on some of the fundamental physical properties and characteristics of sliding and rotating parts. This will allow sophisticated modeling programs to be refined so that rapid prototyping can become a reality for most hydraulic applications."

This futuristic-looking handling system from Festo Corp. has horizontal and vertical axes, along with a gripper. The two motion axes are more rigid and precise than standard cylinders, and they offer internal sensor connections with easy terminations at the back. They also accommodate intermediate positions with an internal, pneumatic, mechanical stopper.

Prof. Wayne Book of Georgia Tech believes integration of fluid components with electronic sensors and controls is next. "Pressure and displacement sensors will be the basis for advanced control algorithms implemented inside the components and coordinated with digital networks." This will produce better control at a lower cost, with fewer complications or leakage, he says.

Another interesting way the computer may play a greater role in tomorrow's fluid power systems is from a tuning perspective. Peter Nachtwey, president of Delta Computer Systems, says that once basic functionality is established, motion systems can be tuned more precisely in less time if the performance of the system can be displayed and tuned using graphical tools.

"In the future, diagnostic tools won't be used solely for identifying problems, they will also be used for system setup, tuning, and ongoing production optimization. Ultimately, motion systems will be able to — within reason — tune themselves."

Frank Latino, product manager for valve terminals and electronics for Festo Corp., stresses that in pneumatics, the integration of web-based information technology into components will bring amazing results. "The service is primarily condition monitoring, predictive maintenance, and diagnostics," says Latino. "Pneumatic companies will provide web-enabled products. We will probably see more wireless-based Ethernet technology. End users will either monitor and maintain their own systems, or farm this responsibility out to a service provider."

Via web technologies, companies-will collect plant data related to pneumatic systems. This data will help in maintenance decisions, increase energy savings, and improve uptime and reliability.

Super components

Individual fluid power components will surely see remarkable advancements in the coming years. While conceding that it's a risky prediction, Book postulates that new small-scale applications could grow out of micro electromechanical systems (MEMS) and similar technologies. "MEMS technology is producing tiny actuators, sensors, and controllers. They are currently used in medical and similar applications. With the need for small-scale systems with somewhat larger motions, it seems that fluid power has some natural advantages," he says. Applications could include medical, prosthetics, and robotics.

Burton has an exciting view of embedded condition monitoring systems in all components. "The computer and microprocessor technology exists to physically do this, and the fundamental methods for the implementation of condition monitoring are well established for many applications."

Components will continue to see higher pressure while they become lighter and more compact. According to Labus, competitive pressures from alternate technologies will continue to require increases in powerto-weight and power-to-volume ratios. Increases in operating pressure will continue until other restrictions on component size, such as rod buckling for cylinders or manufacturing requirements, become the limiting criteria.

Wanke, too, sees the higher operating pressures, estimating them to reach the 10,000-20,000 psi range. "This would have to be accompanied by strong, lightweight composites or other types of materials that would ensure safe, reliable, and energy-efficient systems." He also foresees 100% zero external leakage systems down the proverbial road. These might be sealed with a non-toxic, contaminant-free fluid that would last as long as rest of the system.

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."

Improved efficiency

Koskinen points out that total efficiency of hydraulic driven machines is still very low — under 5% for some mobile hydraulic systems. He feels new control systems, materials, and design methods will boost efficiency, but a lot of R&D is still necessary.

Book thinks new valving concepts will overcome traditional constraints to efficiency and performance. "Some valve designs such as the use of poppet-type valves instead of spool valves, or inherently unstable valves for fast, direct actuation will be made practical by virtue of integrated sensors and controllers," he says.

Labus notes advanced lubrication design is another area of potential improvement. "The loss of volumetric efficiency at low displacements limits the use of hydraulic components over wide displacement ranges. Advanced contact materials could significantly reduce lubrication leakage losses and increase the overall efficiency across a wider displacement range."

Prof. Monika Ivantysynova of Purdue University sees displacement control replacing resistance control as a major trend in efficiency. "Variable pumps and motors must be used as the final control element of fluid power actuators and drives," she says.

Ivantysynova contends this will help make fluid power systems more efficient. Less energy dissipation means less heat generation. The replacement of control valves leads to simpler systems by reducing the number of interfaces and fittings. "Displacement control actuators are much easier to control than valve-controlled actuators, where two different control elements — the control valve of the actuator and the pump supplying the actuator — must be simultaneously managed."

Use of the flow control valve has to stop, says Burton. "New approaches to flow modulation must be attempted if we want to be competitive. Hydrostatic systems can meet this need, but more must be done to make them practical for smaller loading type conditions."

Trinkel sees variable-frequencydrive electric motors driving fixed volume pumps as a great step forward in energy use. This combination gives infinitely variable speed at any pressure with minimum energy waste and system shock. Leaks will be less, heat will be less, components will last longer and circuits will be less complicated.

Educating the engineer of the future

It is always dangerous to predict the future of anything. In 1977, Ken Olsen, the founder of Digital Equipment Corp., felt there was no reason for anyone to have a computer in his home. Even Bill Gates was heard to say in 1981 that "640 k ought to be enough for anybody." These men were experts and innovators in the field, and they still got it wrong. However, despite such uncertainty, it is essential that engineering education become more future oriented and less of an accumulation of reactions to the past.

When I was a student, you could always tell the engineers by the way they looked: crew cut, pocket protector, and a slide rule hanging from the belt. In those days, engineering graduates sought out a job at a great American company and worked there for their entire career.

Today, the lines between disciplines are becoming increasingly interwoven, and the time-honored understanding of engineering as a whole is becoming less distinct. To many, it's no longer clear where science stops and engineering starts, or even where engineering stops and business begins. It's enough to make one wonder whether the traditional engineer as a species will still exist fifty years from now, or whether engineering will become indistinguishable among the many overlapping disciplines and interdisciplinary combinations.

What is clear is that we cannot compete in this economic climate by offering the same old solutions. The advantages of our global competitors lie at the end of the spectrum where processes and products have been standardized and become routine. Our opportunity is at the other end of the spectrum with creative, innovative, high-end products and services that offer higher value. To lead the way at the high end of the economic spectrum, we need to build an economy based on innovation.

India and China are emerging as economic powers in part because they are steadfastly investing in building world-class education systems that produce skilled technology workers such as engineers. BusinessWeek recently reported that India's schools are pumping out 260,000 engineers a year who will work for salaries much lower than in this country. China is graduating more engineers than any other country in the world — more than twice as many as the U.S. — and Russia has a many high-quality engineers who are welcoming U.S. companies to open shop there.

In stark contrast, the number of American students earning engineering degrees began to decline in the early 1980s. For a while, we were able to offset that decline at the graduate level by attracting outstanding foreign students to fill our classrooms, and many of them stayed to take jobs in our workforce. However, those international students who still come are much more likely to return home because good jobs now await them in their own countries.

U.S. engineering education stands to be marginalized if we are passive. The education we provide to engineers must prepare them to move beyond merely fulfilling a technological function and become leaders in making wise decisions about technology and setting policies that will foster innovation.

Engineers have always been "doers," but the presence of technology in every aspect of life now calls for us to become "deciders," as well. The skills and perceptions of engineers make us well suited to play a broader leadership role in today's technological world, and the expectations of the world for engineers are higher than in the past.

We can no longer invent technology in a vacuum and put in on the shelf without concerning ourselves with the broader problems it might solve or create. The question is not merely how we can improve a piece of technology, but rather how we can change it to better serve society as a whole.

In an effort to imagine engineering's future role as a profession and suggest how engineering education can help prepare its graduates for that role, the National Academy of Engineering's Committee on Engineering Education launched the Engineer of 2020 initiative. In the traditional paradigm, change came to the engineering curriculum as an after-the-fact response to a development in industry or event in society. For example, engineering education responded to the successful launch of Sputnik by the Soviet Union by adding more science-based material to the curriculum. The Engineer of 2020 initiative wants to turn that process on its head by thinking creatively about the challenges of the future and examining bold and innovative ideas in engineering education.

Engineering educators have not been sitting on their hands. Dartmouth University and Smith College are pioneering a curriculum with a humanities focus. The military academies offer a model that incorporates strong leadership training. Institutions like Drexel, Northeastern, Kettering, and Georgia Tech incorporate a strong cooperative education component.

One way to address the challenges facing engineering educators is to develop multiple tracks, so that students choose a direction that fits their goals and abilities. The standard curriculum might be maintained as a straight technological track, while alternate tracks are developed to offer a stronger focus in other areas.

Another idea is to follow the trail already blazed before us by professions like architecture, business, and law of making the master's degree the first professional degree. This plan would provide more time for the educational process, making room to add important new elements and skills.

We also need to engage the help of the federal government. The past ten years have witnessed the decline of federal support for engineering research and the disappearance of scholarship and fellowship programs designed to encourage U.S. students to undertake advanced study. This is a critical problem, because we cannot generate the innovation on which our economy increasingly relies without new technology from research and without the help of an educated corps of students who have had advanced engineering studies.

Rather than allowing engineering to disappear in a sea of interdisciplinary fields, we can craft exciting education programs that enable it to move to the fore and offer the technological leadership and expertise the world needs to prosper.

Submitted by Wayne Clough, president, Georgia Institute of Technology, Atlanta.