A low fluctuation control strategy for PMSM direct drive system targeting Particle Beam Instrumentation Application

Particle accelerators have a singular environment where multiple constraints are driving the engineering of equipment. Designers have to deal with the destructive effects of charged particles, high vacuum requirements, large temperatures and particular system architectures due to large-scale installations such as the Large Hadron Collider (LHC) at the CERN laboratory. At the same time, there is a continuous challenge to produce, measure and control smaller particle beams to increase the discovery potentials of large physics experiments. In this context, an innovative actuator has been built to measure precisely the size of beams down to 150$\mu$m sigma, by moving a thin carbon wire of 30$\mu$m at about 20m·$\mathrm{s}^{-1}$ through particle beams. Called Beam Wire Scanner (BWS), this system uses direct drive coupling to actuate a shaft inside a vacuum vessel without moving parts outside it. We are reporting on the design and validation of its control system based on torque control feedback as the only on-line closed-loop system to operate this instrument. The proposed strategy keeps the smoothest action as possible on the system avoiding speed and position corrections that would lead to undesired torque variations, increasing the uncertainty of the carbon wire position.