Laser Lock Control for Photothermal Spectroscopy in an Industrial Environment

Mario Willaredt

Endress+Hauser Digital Solutions

Thursday, June 27, 2024, 13:00

Room 02-012, Georges-Köhler Allee 102, Freiburg 79110, Germany

In this thesis a control structure to perform a laser lock for photothermal spectroscopy for the application of gas sensing is presented. In order to be applied in industrial applications, the control structure needs to be robust against disturbances detuning the resonance of the measurement cell without eliminating the measurement signal. A model for the control plant is identified and a PID controller is implemented on an FPGA. Additionally, a digital bandstop filter is implemented which is included in the control loop in order to preserve the measurement signal. Finally, it is shown experimentally that the proposed control structure achieves satisfactory disturbance rejection without impairing measurement performance compared to a control structure without bandstop filter.