Eventos Anais de eventos
COBEM 2021
26th International Congress of Mechanical Engineering
System Identification and controller design for the high-dynamic double-crystal monochromator at Sirius
Submission Author:
Ricardo Caliari , SP
Co-Authors:
Ricardo Caliari, Niederauer Mastelari, Renan Geraldes
Presenter: Ricardo Caliari
doi://10.26678/ABCM.COBEM2021.COB2021-1808
Abstract
A 4th generation of storage ring light sources is emerging to push the X-rays brightness and coherence fraction to unprecedented levels. As a consequence, a breakthrough is expected in science opportunities in terms of temporal and spacial resolutions. Yet, in order to allow the experiments to profit from the progress of the storage rings, their experimental stations, the so-called beamlines, must evolve and perform accordingly. Then, after decades of well-established solutions, several beamline instruments may now need to go through a paradigm shift. With the construction of the new Sirius Storage Ring, since 2015 the Brazilian Synchrotron Light Laboratory (LNLS) has developed the High-Dynamic Double-Crystal Monochromator (HD-DCM) for X-rays. Indeed, understanding that the traditional approach of high-stiffness design and mitigation of disturbances would be close practical limitations in existing X-ray monochromators, the HD-DCM is the first to implement a low-stiffness mechanical design concept with high closed-loop mechatronics performance. Its development was based on predictive design to realize it “first time right" and deliver positioning performance improvements by factors of 4 and 100 with respect to state-of-the-art monochromators, in fixed and scanning modes, respectively. The project target numbers were 1nm RMS in position stability and 10 nrad RMS in pitch and roll stabilities, all integrated up to 2.5kHz. These could just be achieved by means of a closed loop control projected with the desired bandwidth of 250Hz. The real time system operates in an update rate of 10kHz, what makes it possible in use many well-known controller design techniques. For the purpose of this project, the loop-shaping technique was implemented to achieve the desired bandwidth with the phase and gain margin robustness targets. A detailed plant identification was essential to ensure a robust design and to guarantee a safe operation at different conditions. The plant identification methods and results are also discussed in this work. The final controller design is discussed with bode plots, open-loop, sensitivity and Nyquist diagrams. The in-position stability result is the major number to be compared for such a system designed to select energy in a Synchrotron radiation beamline. But in the case of this system, the scanning modes are discussed in a deeper level, because we proved to achieve much better stability with much higher scanning velocities than ever made for this kind of machine. These characteristics shall be beneficial for the Sirius scientists to achieve results never imagined before.
Keywords
System Identification, mechatronics analysis, Mechatronic Systems Design, Mechatronics, Synchrotron radiation, loop-shaping, Feedback Control
