German researchers introduce precision electromagnetic valve control

The ‘sensor-free’ technology uses an electromagnetic field to control the position of a bolt and determine its position.

Scientists at Saarland University have developed a technique to precisely control valves via an electromagnetic current, and say that it improves on conventional electromagnetically controlled valves that only have ‘on’ and ‘off’ settings.

Using a magnetically permeable metal bolt moving within a coil of wound copper wire, they apply a patent-pending control methodology that they say is ‘sensor-free’ to control the volume of fluid passing through a valve. Operators can determine the position of the bolt by analysing the electric current that flows through the coil and then adjust its position.

‘We monitor how the current flowing in the coil changes with time. Specifically, we record the fluctuations in the electric current over a certain period of time and analyse them. These current fluctuations change depending on the position of the bolt. This allows us to determine exactly where the bolt is at any particular time. Knowing where the bolt is means that we have an effective means of controlling its movement,’ said Professor Matthias Nienhaus, who developed the system with his team at the university.

To overcome noise in the electromagnetic signal, the team developed a method (covered by their patent application) to refine the signal and extract meaningful information. ‘It’s a little bit like continuously calculating the average velocity when the speed of the car you’re driving is varying from one instant to the next,’ said Nienhaus.

‘Our method provides us with a measurement signal that is practically noise free. We use the signal to position the bolt where we need it, and we can even position it a little bit beyond the end of the coil.’

The team will be at Hannover Messe 2018, demonstrating their technology by precisely levitating a steel ball within an electromagnetic field.

‘The demonstration clearly shows the speed and precision of our new control technology. We are effectively juggling a steel ball using nothing more than the device’s own current signal – without the need for any additional position sensors.’