Researchers at Siemens have developed a small but powerful piezohydraulic actuator. Although it is only about nine centimeters long, it can apply a force of more than 150 newtons - equivalent to a weight of 15 kilograms. Such actuators are used to operate valves and flaps, for example, and can also be employed in robots.
The concept combines piezomechanics with hydraulics. A voltage causes tiny deflections in a piezoelectric crystal and an internal hydraulic system combines these small movements to generate a rise of two centimeters. Purely electromagnetic actuators loose efficiency if they are very small.
Another advantage of the new actuator is its metallic enclosure, which ensures that all of the required hydraulic fluid is contained in the system so that the actuator only has to be supplied with electricity and not with fluid. Moreover, the actuator is protected against external influences such as dust, humidity, and chemicals.
Piezoelectric crystals expand in a particular direction as soon as a voltage is applied. These crystals are used to drive injection valves in combustion engines, for example. One of their advantages is their dynamic response. Due to their great stiffness, they respond with almost no lag. By contrast, a conventional hydraulic system needs to have a central pump compress the hydraulic fluid in all of the system's pipes before it can generate a mechanical motion.
The piezohydraulic actuator developed by Siemens' global research department Corporate Technology (CT) achieves a high level of stiffness because it only needs six milliliters of hydraulic fluid. The enclosed hydraulic system consists of three adjacent metallic bellows that can expand along an axis and are connected to one another by non-return valves. If the piezoelectric crystal is excited, it expands into the central chamber, where it creates pressure.
This pressure opens the valve to the adjacent chamber, which has an actuator stem attached to its front. The inflowing fluid slightly expands the bellows and the actuator stem is extended. Using a patented integration solution, the developers achieve a total rise of two centimeters:
They operate the piezoelectric crystal with a high-frequency sawtooth voltage and combine the rapid succession of small expansions to create a completely smooth motion of the actuator stem. The concept has two advantages:
If the reverse voltage waveform is applied, the pumping direction and the motion are reversed as well. In addition, the actuator maintains its extension once it has been set. By contrast, the actuators used in conventional gears to transmit power cannot withstand vibrations and other influences over the long-run.
The system is a further development of a piezohydraulic actuator that CT created for controlling the valves of large-scale combustion engines such as gas turbines. According to the developers, the new actuator might also be used for other applications such as in robots, in the operation of aircraft ailerons, and in medical and cleanroom technology.
Dr. Norbert Aschenbrenner | Siemens InnovationNews
It Takes Two: Structuring Metal Surfaces Efficiently with Lasers
15.03.2017 | Fraunhofer-Institut für Lasertechnik ILT
FOSA LabX 330 Glass – Coating Flexible Glass in a Roll-to-Roll Process
07.03.2017 | Fraunhofer-Institut für Organische Elektronik, Elektronenstrahl- und Plasmatechnik FEP
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
24.03.2017 | Materials Sciences
24.03.2017 | Physics and Astronomy
24.03.2017 | Physics and Astronomy