Rock to Road

Features Columns Education
Purdue releasing research on improving fuel efficiency


September 25, 2013
By Purdue University

Topics

September 25, 2013, West Lafayette, Ind. – Researchers at
Purdue University have shown how to reduce fuel consumption while improving the
efficiency of hydraulic steering systems in heavy construction equipment.

September 25, 2013, West Lafayette, Ind. – Researchers at
Purdue University have shown how to reduce fuel consumption while improving the
efficiency of hydraulic steering systems in heavy construction equipment.

The new approach incorporates several innovations: It
eliminates valves now needed to direct the flow of hydraulic fluid in steering
systems and uses advanced algorithms and models to precisely control hydraulic
pumps. New designs might also incorporate textured microstructured surfaces
inside pumps to improve performance.

"Fuel consumption of heavy off-road equipment accounts
for a significant portion of total global fuel usage, so improving efficiency
is very important," said Monika Ivantysynova, Maha Fluid Power Systems
Professor in Purdue's School of Mechanical Engineering. "It's also
important from a commercial business point of view because money saved on fuel
improves a company's bottom line."

Advertisment

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.

In the new valveless design, each actuator has its own pump,
eliminating the need for valves. 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.

Findings are detailed in a research paper being presented
during the SAE 2013 Commercial Vehicle Engineering Congress on Oct. 1-3 in
Rosemont, Ill. The paper was authored by doctoral student Naseem Daher and
Ivantysynova, director of Purdue's Maha Fluid Power Research Center.

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.

Testing the new "electro-hydraulic power steering
system" on a front loader has shown a 15 percent fuel savings and 23
percent increased machine productivity, for a total fuel efficiency increase of
43 percent during steering maneuvers.

"The world's first pump-controlled steer-by-wire
prototype machine is now readily available for further research and
development," said Ivantysynova, who has a dual appointment in the
Department of Agricultural and Biological Engineering.

In previous projects, Maha researchers have shown that
valveless systems could reduce fuel consumption by 40 percent in an excavator
equipped with the technology. Measurements on the same excavator prototype also
showed 70 percent productivity improvement in terms of tons of soil removed per
kilogram of fuel consumed.

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," she said.
"We have developed the only code that models these lubricating interfaces
under extreme heat and high pressure."

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.

"Our prototypes are very close to commercial
prototypes, so they are readily adaptable to machines now in use and can be
easily industrialized when manufacturers decide to make the transition into
valveless systems," he said.