This research aims to improve the efficiency of switch-mode hydraulic systems by developing an improved check valve design. Switch-mode hydraulics shows promise for higher efficiency but current check valve technology fails under high frequencies. The researchers are modeling check valve behavior under different conditions to understand failure points. Preliminary experiments using a laser to track poppet movement found rebound causes pressure anomalies and potentially leakage. Continued testing will validate models to enable a check valve design meeting the demands of switch-mode hydraulics and higher system efficiencies.

1. Who are the industry and university
collaborators?
How does the research fit into the
overall strategy and goals of the
Center?
Project: Modeling the Check Valve
Investigators: Alek Gust SJU, Alex Yudell UMN, Prof. James Van de Ven UMN
What progress has been made?
On which test bed will the research
be demonstrated?
What is the main idea?What fluid power-related question is
being answered?
Georgia Institute of Technology | Milwaukee School of Engineering | North Carolina A&T State University | Purdue University | University of Illinois, Urbana-Champaign | University of Minnesota | Vanderbilt University
Future Work
• Fluid Power has unparalleled power density compared
to other systems, however it is inefficient.
• Switch-mode or “Digital” hydraulics show great promise
for improving efficiency.
Accumulator
Check Valve
High Pressure Rail
On-Off Valve
• Switch-mode hydraulic circuits utilize the same concept
as digital electronics. Switch-mode hydraulics direct
short pulses of flow to either the load or the tank thus
avoiding wasting energy by metering. This improves
overall system efficiency.
• Unfortunately this new advancement in hydraulic
systems is being hindered by old technology. The check
valve, though simple and effective, begins to fail when
subjected to the high frequencies utilized by switch-
mode hydraulics.
• A better check valve must be engineered in order to
reach the necessary operating parameters. The first
step in the engineering process is to model the check
valve’s behavior to better understand why and when it
begins to fail.
The introduction of switch-mode hydraulics (which is
analogous to digital electronics) holds great promise for fluid
power systems to become more efficient. Unfortunately,
several challenges arise regarding switch-mode hydraulics
that are not present in digital electronics:
1. Electrons, being of very low mass and thus low inertia can
be forced to change directions very easily. Whereas fluids,
being much more massive, are very difficult to change
direction.
2. Switch mode hydraulics systems require a high speed
valve that can route flow quickly between the load and
tank.
A major component in a high speed valve is a one way check
valve. At high frequencies, check valves in hydraulic systems
have the tendency to allow leakage flow back to tank which
results in wasted energy and decreases efficiency. My
summer 2014 REU research program is to investigate and
measure the behavior of a check valve under different
conditions to better understand the root causes of leakage
during high speed operation.
How does a check valve perform under high speed (< 5 ms)
operation? How does a check valve perform under different
pressure differentials? Can this theory be experimentally
validated through means of a laser micrometer?
This set up allowed us to control the rate of flow as well as
the pressure differential across the check valve. The
displacement of the check valve poppet was recorded via a
high speed laser micrometer.
This research will be demonstrated on either TB1
(excavator), TB3 (hydraulic hybrid passenger vehicle), or
TBα (wind power).
• Custom machined hydraulic check valve manifold was
required. Manifold was designed to allow the laser
micrometer to view the check valve poppet during
operation. The following design has been machined and
is now operational for experimental testing.
• This manifold combined with
a high speed 3-way solenoid
valve allows for flow to be
rapidly directed through the
check valve at controlled
frequencies which in turn
controls poppet displacement.
Using this experimental set up, the preliminary data shown below was acquired at a
system pressure of 1500 psi and a duty cycle of .5 (50% tank 50% load) with a
switching frequency of .5 seconds.
The signal voltage from the laser micrometer and the actual displacement of the
check valve poppet are of linear relation, thus both show a rebound of the poppet as
the flow to the load is reverted back to tank.
• My theory suggests this rebound can be the cause of the
check valve’s reverse flow leakage attributed to switch-
mode hydraulics. The pressure sensor associated to the
load depicts a corresponding anomaly in the pressure
differential across the system and load pressures during
the time of the poppets rebound.
*This data is not conclusive as this was only a single (though repeatable) experiment.
Further investigation of the check valve’s poppet under
different operating parameters is required to accurately
validate our simulation model. Once the model has been
successfully verified, it can be used to create a modified
check valve that can meet the operating requirements set
forth by switch-mode hydraulics. Creating this new check
valve holds great promise for improving the efficiency of
switch-mode hydraulic systems. This new technology can
then be integrated into fluid power systems that utilize
switch-mode hydraulics. This incorporation can make many
new and existing systems more efficient.Excavator
Passenger Vehicle
Wind Power
Laser
Micrometer
Check Valve
Manifold
Relief Valve
Solenoid
Valve