New valveless electro-hydraulic steering system for off-road equipment shows significant fuel savings and productivity benefits
Researchers at Purdue University have developed a new valveless hydraulic steering system for heaving construction equipment that improves efficiency and reduces fuel consumption. The new approach eliminates valves now needed to direct the flow of hydraulic fluid in steering systems and uses advanced algorithms and models to control hydraulic pumps precisely. New designs might also incorporate textured “micro-structured” surfaces inside pumps to improve performance.
Testing the new “electro-hydraulic power steering system” on a front loader has shown a 15% fuel savings and 23% increased machine productivity, for a total fuel efficiency increase of 43% during steering maneuvers. The findings are detailed in a research paper being presented during the SAE 2013 Commercial Vehicle Engineering Congress (1-3 October). The paper was authored by doctoral student Naseem Daher and Monika Ivantysynova, Maha Fluid Power Systems Professor in Purdue’s School of Mechanical Engineering, and director of Purdue’s Maha Fluid Power Research Center.
In previous projects, Maha researchers have shown that valveless systems could reduce fuel consumption by 40% in an excavator equipped with the technology. Measurements on the same excavator prototype also showed 70% productivity improvement in terms of tons of soil removed per kilogram of fuel consumed.
Fuel consumption of heavy off-road equipment accounts for a significant portion of total global fuel usage, so improving efficiency is very important. It’s also important from a commercial business point of view because money saved on fuel improves a company’s bottom line.—Monika Ivantysynova
In the new valveless design, each actuator has its own pump. The actuator motion can be precisely controlled by adjusting the pump displacement, which changes the amount of fluid being delivered to the actuator. Being able to adjust the pump displacement makes it possible to run the machinery’s diesel engine at optimal speeds, resulting in additional fuel savings.
Typical hydraulic systems in heavy equipment use a central variable displacement pump that delivers fluid, and valves that throttle the flow of fluid to linear and rotary actuators that move tools such as shovels, buckets and steering mechanisms. This throttling causes energy to be dissipated as heat and wasted.
Present hydrostatic steering systems are plagued by poor energy efficiency, and industry is developing new steer-by-wire technologies to reduce fuel consumption and improve performance. However, the steer-by-wire systems being developed still require energy-wasting valves.
The new steering system also may help reduce operator fatigue while improving safety by controlling the level of steering-wheel torque feedback. Steer-by-wire technology removes all torque—the twisting force required to turn the steering wheel. However, removing the torque is potentially dangerous because the driver lacks the tactile feedback needed to properly control the vehicle.
In the new system, torque feedback is regulated according to parameters such as steering wheel angle and turning speed, vehicle speed and the angle of a rotating joint that connects the vehicle’s two subframes.
New thermodynamic modeling by the group also has found that steel parts in the pump undergo significant deformations from high heat during operation.
The deformation due to heat can be as large as the thickness of the lubricating film, and this is very important. We have developed the only code that models these lubricating interfaces under extreme heat and high pressure.—Monika Ivantysynova
The research paper includes details of the system’s layout, the hardware and electronic controller developed through the use of modeling. The researchers developed and used the modeling to simulate the system’s performance.
The Purdue laboratory is working with industry partners on applied research projects, said Anthony Franklin, the Maha lab’s manager.