The Evolution of Hydraulics

The Evolution of Hydraulics

By Ted Freeman, Director of Manufacturing, Vertex Aerospace and Industry Consultant

My first career-type job as a new Mechanical Engineer out of college was with one of the largest hydraulics companies in the United States. Thrilled with the opportunity to take all the theory and apply to everyday tasks that need to be completed via off-highway mobile valves and pumps. As a new design and development engineer, I was rapidly put onto the shop floor to learn the manufacturing side prior to touching new designs. Only after this several demonstrations of an understanding of manufacturing was, I allowed to design new products and opened my mind to the industry of fluid power.

The evolution of hydraulics has seen more sophistication with electronic controls, and smart applications that have benefitted the OEMs as the cost of electronic signals and controls has dropped dramatically. The clear path in the evolution has become to replace as much of the hydraulic system, usually an open looped system, with a closed-looped system utilizing electronics. Hence the term electro-hydraulics. Typically, the hydraulic system had fluid power feedback into the valve or pump as needed, but those feedback systems (pilots) are expensive and have been replaced with newer applications of pressure sensors and wiring. Furthermore, piezoelectric applications could soon usurp current state feedback pressure systems electronic feedback systems specifically for servo-valves with varying loads. These systems being developed are much more stable under a variety of loads that the old “pilot hole” feedback that is subject to hydraulic pressure pulses from varying loads.

My hydraulics career thrust me into aerospace applications and quickly found the design factors very different from the off-highway mobile hydraulics market. The design factors in aerospace is performance, dependability, and reduced weight. In the off-highway mobile hydraulics market, weight was a nonfactor. However, in aerospace, it is the second question at a design review after it will meet the performance. My first application experience in aerospace was on a design team for the Joint Strike Fighter. Performance and weight were critical. In aerospace, performance and weight are not mutually exclusive. There are tradeoffs between higher pressure systems and less weight, due mainly to the reduction in the size of fluid lines and volume of fluid needed to perform the task. While the defense side tends to help push these performance parameters needed to achieve the savings like Parker hydraulics. In-service applications of higher pressure (5000 psi) military aircraft are the Bell Boeing V-22 Osprey and F/A-18. These systems designed well over 20 years ago has allowed for newer commercial applications to apply these system efficiencies. The most widely known 5000 psi system on the commercial side is the Airbus A380 that was designed more recently.

Newer technologies in manufacturing, such as additive manufacturing, can greatly improve weight as well. With newer Titanium, Stainless Steel, and Aluminum additive approaches, this unlocks several design constraints among the design teams and engineers in aerospace. With additive manufacturing, short production runs and lack of otherwise necessary tooling for the casting market appears positioned to be upset. Additive also invites complexity into designs that otherwise conventional manufacturing techniques, whether casting a mold or machining internal chambers of a valve, are challenged. Since the highly publicized GE nozzle has taken flight, the excitement around the additive manufacturing is now also in the designer’s toolkit to further reduce weight in aerospace applications.

From initial work on tractors, forklifts, and sprayer applications to the next advanced aircraft, the excitement around the higher pressure systems, additive manufacturing, smart electro-hydraulics, and potential piezoelectric industrialization keeps the industry agile for those companies willing to integrate these advancements.

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