Sensors for waveform control in a Lorentz force based actuator system for turbulence research

This work discusses the use of analog light barrier and Hall sensors for waveform control in an actuator system for turbulence research. The system shall produce up to 80 Hz, 80 mm wavelength running surface wave with amplitudes from 50 to 1000 μm. To ensure both, waveform and amplitude, the control algorithm requires real time amplitude measurements of all 20 actuators. Techniques are described to extend the limited measurement range of analog light barriers and to reduce impact of mechanical disturbances on the measurement process by placement and compensation. Also a small bar permanent magnet together with Hall sensors to track position are employed and a method for reducing impact of the strong magnetic stray fields affecting Hall sensors in this actuator system is developed.