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Robust Speed Controller Design for Torsional Vibration Damping on Variable Torque Drive Systems


Michail Tsopelas

Master Thesis, FS13 (10230

The problem of torsional vibrations in electromechanical systems, such as Variable Torque Drive (VTD) systems, remains a challenge since many years. Due to interactions between the electrical and mechanical parts of the system, the natural torsional frequencies (eigenfrequencies) of the shaft are excited, producing oscillations and causing strain and fatigue to the mechanical parts. This, results in reduced lifetime for the shaft, complete failure of components and the need for more frequent maintenance. Therefore, the Oil & Gas Industry is still looking for effective and easy to use solutions that can reduce or even eliminate such problems. Damping such oscillations is a challenge itself and many methods have been proposed. For example, black-box solutions such as the Integrated Torsional Mode Damping, which attempts to keep oscillations within safety margins. Also, high-level speed controllers are currently been used: such controllers, designed on traditional methods appealing to industry due to their simplicity, such as PID controllers, have proved insufficient. Other, more elegant methods such as a Model Based Predictive Control, Flatness Based Control, full state-output feedback control, even Neural Networks have been proposed with mixed results. However, rarely do such methods focus on the mechanical part of the system, and even rarer do they consider uncertainty, which is an important issue in such systems. In this Master Thesis, we consider a robust H1 approach for designing high level outputfeedback speed controllers that provide suitable torque references for speed tracking and damping torsional vibrations on a VTD system. We also study a promising alternative, Multi-objective Output-Feedback Control via LMI optimization and H1. Both methods are taking into account the mechanical model, together with an uncertainty model based on H1 perturbations. Our study is based on a real ABB VTD project and our controllers are compared to an existing solution of ABB, a finely tuned PID controller together with its auxiliary blocks. iii


Type of Publication:

(12)Diploma/Master Thesis

R. S. Smith

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% Autogenerated BibTeX entry
@PhdThesis { Xxx:2013:IFA_4536
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