Gaussian Process Repetitive Control for Suppressing Spatial Disturbances

Motion systems are often subject to disturbances such as cogging, commutation errors, and imbalances, that vary with velocity and appear periodic in time for constant operating velocities. The aim of this paper is to develop a repetitive controller (RC) for disturbances that are not periodic in the time domain, yet occur due to an identical position-domain disturbance. A new spatial RC framework is developed, allowing to attenuate disturbances that are periodic in the position domain but manifest a-periodic in the time domain. A Gaussian process (GP) based memory is employed with a suitable periodic kernel that can effectively deal with the intermittent observations inherent to the position domain. A mechatronic example confirms the potential of the method

A Gaussian Process approach to multiple internal models in repetitive control

Disturbances that come from multiple originating domains, e.g., time, position, or commutation-angle domain, are often encountered in practice due to the increasing complexity of mechatronic systems. The aim of this paper is to present a generalized approach that enables asymptotic rejection of multi-dimensional disturbances which are periodic in the different originating domains, e.g., if speed changes, then spatially-periodic disturbances manifest themselves differently in the time domain. A multi-dimensional Gaussian process (GP) based internal model is employed in conjunction with a traditional repetitive control (RC) setting using non-equidistant observations, allowing to learn a multidimensional buffer for RC. A case study with a spatio-temporal disturbance confirms the benefit of this method

Systematic feedback control design for scattered light noise mitigation in Virgo's MultiSAS

Gravitational Wave (GW) detectors are used to gather knowledge on violent cosmic events like the merger of pairs of black holes. These waves are measured using large-scale interferometers, which detect the undulations in spacetime resulting from GWs. Scattered light noise resulting from the horizontal RMS velocity of auxiliary optics limits the attainable sensitivity of GW detectors. A systematic approach for the design of a feedback controller in the suspension systems of these auxiliary optics is presented in this paper. Experimental validation shows a substantial reduction in the RMS velocity compared to the feedback strategy currently employed in these suspension systems

Suppressing Position-Dependent Disturbances in Repetitive Control: With Application to a Substrate Carrier System

Positioning systems are often subject to position-domain disturbances: these are periodic in the position domain yet can appear a-periodic in the time domain. The aim of this paper is to develop a position-domain repetitive control approach that allows to attenuate disturbances with arbitrary varying period. The key idea is to implement a memory loop in the position domain on the basis of non-equidistantly distributed observations, which are inherent to the position domain. An experimental validation on an industrial substrate carrier shows a major performance improvement for a large range of velocities