With the innovative procedure of the drive technicians of Saarland University, valves can dose liquids like a tap and close door latches gently and silently. All the researchers need is a magnetically conductive metal bolt that moves back and forth in a coil of wound copper wire, and its patent pending sensorless drive.
In order to hold the bolt in any position, Professor Matthias Nienhaus and his team manage without separate position sensors: Only by evaluating the current that flows through the coil can they recognize the position of the bolt and can control it with lightning speed.
At the Hanover Fair at the Saarland Research Stand (Hall 2, Stand B 46) from April 23 to 27, the engineers will demonstrate the potential of their sensorless process by levitating a steel ball.
Today common valves or closing devices, which are controlled electromagnetically, switch fast, but they mostly know only the states “open” and “closed”. If, for example, the power is turned on in such a door lock, the bolt hits the stop with force. When switched off, a spring pulls him back. If the component can do more – hold the valve about an intermediate position or gently strike a lock – so far this is an expensive endeavor: Additional sensors and a complex control technology are used.
Without any additional sensors, the new process developed by the drive engineer Professor Matthias Nienhaus and his team from the University of the Saarland. With this, the bolt lands both “soft” at the stop, as well as precise and free in any desired position: So not only in “open” and “closed”, but also in everything in between – similar to a tap, sometimes more, sometimes more.
The researchers need to do this alone the information that provides the current itself, with which the bolt is controlled. “We use the temporal course of the current in the winding, which means that we look at fluctuations over a certain period of time and evaluate them. The current fluctuations change depending on the position of the bolt. As a result, we know exactly where the bolt is at all times. At the same time, this position recognition enables us to control the bolt effectively, “explains Matthias Nienhaus.
The signals that the researchers initially receive here are anything but meaningful: they are considerably noisy. “We smooth these signals using a newly developed, integrating process that we have patented,” says Nienhaus.
The drive engineers use the novel method to filter out the actual measurement signals neatly. “You can compare it to something like being in a car, in which the car sometimes fast, sometimes slow driving, constantly calculate the average speed,” says Nienhaus. From the results, the researchers can pinpoint exactly where the bolt is currently in the winding. “A practically undistorted measurement signal is created. And this we can use to position the bolt, even a bit outside the coil, “he explains.
The Saarbrücken drive engineers show what they understand by “clean control” at the Hannover Messe: They playfully demonstrate their engineering skills and the potential of their development by controlling a steel ball so precisely and skillfully that it floats up and down as desired. “This shows the speed and precision our technology is capable of. We just juggle the ball with current control signals without a separate position sensor, “says Matthias Nienhaus.
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