You might have heard of magnetic-levitation (maglev) transportation vehicles that use magnetic fields to suspend a vehicle and in some cases propel it. In collaboration with the Technical University of Vienna, researchers from the Corporate Technology division of Siemens demonstrated the basis for a future sensorless magnetic bearing that uses active electromagnets to suspend and keep in place a rotating shaft. Magnetic-type bearings offer advantages over conventional bearings. Because they operate without friction, they do not wear or deteriorate from physical contact. As a result active-magnetic bearings can increase bearing life, have a long service life, require little maintenance, and operate at more than 200,000 rpm. The lack of lubricant could make this type of bearing well suited for vacuum-pump shafts, where leaking oil could contaminate an environment, such as that in a clean room.
The demonstrator comprised a ball held suspended by magnetic fields without any sensors. To me, the lack of sensors makes a big difference. Traditionally, active magnetic levitation requires sensors to measure fields so a controller can adjust the fields in real time to keep a body properly suspended. An active-magnetic bearing requires a similar type of real-time control to keep a shaft centered and suspended in a surrounding magnetic field. The controller relies on sensors that measure the shaft’s position. These sensors require extra space and increase bearing costs, so today’s active-magnetic bearings find limited use.
So, how did the researchers at Siemens and the Technical University of Vienna measure a shaft’s position without sensors? They took advantage of how the shaft alters the magnetic field used to suspend the shaft. The movement of the shaft changes the inductance of the electromagnetic coils, which in turn alter the current and voltage at the electromagnets. The measurements–made at the electromagnet power supply–require no extra wires or connections with the electromagnets themselves. As a result, magnetic bearings would become smaller and less expensive. The researchers developed a technique that uses the voltage and current measurements to determines the position of the shaft quickly and accurately and control the surrounding magnetic fields to keep the shaft in position. That technique should give sensorless active-magnetic bearings a good future. –Jon Titus
Advertised as the "Most Powerful Tablet Under $100," the Kindle Fire HD 6 was too tempting for the team at iFixit to pass up. Join us to find out if inexpensive means cheap, irreparable, or just down right economical. It's teardown time!
The increased adoption of wireless technology for mission-critical applications has revved up the global market for dynamic electronic general purpose (GP) test equipment. As the link between cloud networks and devices -- smartphones, tablets, and notebooks -- results in more complex devices under test, the demand for radio frequency test equipment is starting to intensify.
Much of the research on lithium-ion batteries is focused on how to make the batteries charge more quickly and last longer than they currently do, work that would significantly improve the experience of mobile device users, as well EV and hybrid car drivers. Researchers in Singapore have come up with what seems like the best solution so far -- a battery that can recharge itself in mere minutes and has a potential lifespan of 20 years.
Some humanoid walking robots are also good at running, balancing, and coordinated movements in group settings. Several of our sports robots have won regional or worldwide acclaim in the RoboCup soccer World Cup, or FIRST Robotics competitions. Others include the world's first hockey-playing robot and a trash-talking Scrabble player.
Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.