Search

This article proposes an alternative for robust control of synchronous reluctance motors using linear matrix inequalities to obtain fixed gains that ensure current and speed regulation, under parameter uncertainties and variations. The proposed design procedure is based on a polytopic model, which takes into account: i) uncertainties and variations of the mechanical and electrical parameters of the motor, ii) one step delay from digital implementation of the control law, and iii) internal model based controllers to guarantee reference tracking. Less conservative linear matrix inequalities, relying on slack variables, ensure robust pole location and certify the closed-loop stability for the entire domain of uncertain and time-varying motor parameters, based on parameter-dependent Lyapunov functions. The linear matrix inequalities ensure a fast and systematic computation of the control gains, that are also easy to be implemented, not adding computational complexity when compared, for instance, to usual strategies based on PI controllers. Experimental results for a 2.2 kW commercial motor are provided, validating the proposed procedure, and illustrating good tracking of currents and speed references, with suitable dynamic responses and reduced cross-coupling effects, when compared to sliding mode and PI controllers. [ABSTRACT FROM AUTHOR]

This paper investigates the digital redesign of proportional integral (PI) controllers implemented under a delay of one sampling period. The usual digital redesign based on state matching cannot be directly applied here. The digital control gains are obtained by means of linear matrix inequalities that minimize the H ∞ norm associated with an error signal defined as the difference between the closed-loop system with continuous-time controller and the closed-loop system with the discrete-time controller implemented under the delay. Three synthesis conditions are given, exploring extra matrix variables and suitable matrix structures to provide more efficient redesigns that can deal even with large control delays in the implementation of the redesigned controller. As a contribution, the proposed conditions provide a theoretical guarantee that digital PIs, operating under delay, will perform very close to originally designed continuous-time PIs. A numerical example illustrates the efficiency of the proposed conditions, and a practical application for permanent magnet synchronous motor speed regulation shows good experimental results, illustrating the viability of the proposal. [ABSTRACT FROM AUTHOR]