Fluid power often is thought of as mature technology. But it’s gaining fresh life from new engineering trends, such as vehicle electrification, innovative simulations and experimental research, to develop ways to boost power output and energy efficiency. New research holds promise in areas like agriculture (making farm equipment more efficient to grow more food for an expanding population); construction and material handling (reducing exhaust emissions); biomedical devices (assisting with movement); and autonomous systems (where fluid power’s flexibility and compactness can help make robots’ range of motion and application capabilities more humanlike).
What is fluid power? It’s the technology that uses fluids under pressure to transmit mechanical power, for example, moving a robot arm or propelling a vehicle. Its primary advantages are flexibility (for instance, you can use hoses to navigate corners), and power density (you can transfer more power than with electrical components of the same weight).
These attributes make fluid power ideal for machines that need to generate a lot of power and force, such as off-road vehicles in construction or agriculture, or industrial presses. Fluid power enables lightweight systems in airplanes, like landing gear and flight control flaps. Additionally, fluid-powered systems are simple to control, with respect to actuator torque, direction, speed and force.
Fluid power is seeing increased use in human-size applications, such as biomedical devices to hydraulically activate things like wearable exoskeletons to reduce worker loads and injuries, or to assist with movement for people with physical challenges. It’s finding use in robotic surgical platforms, as well as in surgeries that involve magnetic resonance imaging, for which the use of electrical components is limited by interference with the magnetic field.
As human society progresses, fluid power has been evolving continually. Future fluid-powered machines will differ greatly from those today, meeting human needs for more energy-efficient and environmentally friendly technology. Fluid-powered systems also will become more and more suitable for autonomous machines.
I am principal investigator in two U.S. Department of Energy projects for improving the efficiency of off-road vehicles. In one project, we are creating a novel technology that integrates electric machines and hydraulic machines to enable smart and efficient actuations on construction vehicles. In the other project, we are aiming to double the energy efficiency of the hydraulic system that powers agricultural tractors and attached implements like planters and balers.
Vehicles such as wheel loaders and tractors, as well as their implements, are expensive and considered productivity machines. They also have an intensive use, so energy efficiency to reduce fuel consumption is a big issue. On average, today’s hydraulic systems for off-road applications have about 20 percent energy efficiency — providing a tremendous opportunity in redesigning these fluid power systems.
Besides addressing energy efficiency aspects of fluid power systems, the research activities of Purdue’s Maha Fluid Power Research Center, which I direct, also target such elements as controllability, condition monitoring, and hydraulic component design. We collaborate with many leading hydraulic component manufacturers and original equipment manufacturers in developing the future generation of fluid power systems.
At Maha, we build innovative simulation and computer strategies to analyze the operating details of such key components as hydraulic pumps and motors, and of the entire hydraulic actuation systems of a machine. Our tools allow us to optimize the component design or study entirely new concepts.
We also have a strong educational focus, working to overturn the image of fluid power as old-fashioned technology by teaching it and its cutting-edge applications via advanced touchscreen hydraulic training devices that students use to build working hydraulic systems.
As part of our educational emphasis, we make fluid power fun. Undergraduate students regularly enter the NFPA Fluid Power Vehicle Challenge, sponsored by the National Fluid Power Association. Students must design a hydraulic bicycle such that when it’s pedaled, the rider doesn’t move a chain but rather uses pressurized fluid to transmit power to the wheels. This competition reproduces all the challenges students would encounter in a lab, from designing parts to increasing overall system efficiency in terms of inputs versus outputs.
We won the contest in 2017, and have placed second a couple of times. Along with being instructive, the competition is a lot of fun for the students, especially when they do well.
Andrea Vacca, PhD
Maha Fluid Power Faculty Chair
Professor of Mechanical Engineering and Agricultural and Biological Engineering
College of Engineering, Purdue University