Olof Lindgärde

Performance and robust frequency response for multirate sampled-data systems

Multirate, sampled-data control systems are analyzed in the frequency domain, taking the inter-sample behavior into account. The focus of the analysis is both on the rejection of disturbances within a certain frequency region, and on the robust stability properties. Due to the periodic behavior of such systems, a distinction is made between the performance frequency response (PFR) and the robust frequency response (RFR). The RFR is related to current frequency response approaches for sampled-data systems.

Comparing frequency analysis methods for sampled-data control

In this paper frequency analysis methods for sampled-data control are compared. The relation between the analysis tools that take the inter-sample behavior into consideration and the traditional discrete-time analysis is investigated. It is shown how the plant, the controller design, and the anti-alias filter affect the inter-sample behavior. Both analytical results and numerical examples are included.

Frequency Analysis for Continuous-Time Systems Under Multirate Sampled-Data Control

Abstract Performance analysis in the frequency domain is presented for single and multirate sampled-data control systems. The main idea is to compute the input to output power gain for a single sinusoidal input with a specific frequency. This method is therefore closely related to the maximum principal gain for continuous-time MIMO systems. However, in contrast to the continuous-time case, we observe that the maximum gain of a single sinusoidal input does not equal the H ∞ -norm for sampled-data systems. This implies that robust stability and performance can not be determined by the same kind of frequency analysis. The suggested method for performance analysis, is illustrated on a multirate sampled-data controlled packed-bed distillation column.

Frequency analysis for single and multirate sampled-data control

A frequency analysis procedure for single and multirate sampled-data control systems is presented. The method is taking the inter-sample behaviour into account, and for a sinusoidal input the system power gain is calculated. Also the close correspondence between this method and the principal gain for continuous-time MIMO systems is discussed. Finally our method is illustrated on a sampled-data SISO system.

H/sub /spl infin//-control and frequency analysis for systems with mixed continuous-time and discrete-time measurements

Feedback control using both continuous-time and discrete-time measurements is considered. A design method including both H/sub /spl infin//-synthesis and frequency analysis is suggested. It includes a strategy for selecting weighting filters in the control design. The presented frequency analysis method is then a powerful tool in the design process.

Modeling an Industrial Lime Slaking Process

Abstract In this work a semi-physical model is developed for an industrial dry lime slaking process. The model is based on mass and heat balances for two non-stationary ideal stirred tank reactors in series. The mass balance equations are described by two partial differential equations. It is shown how the total reaction rate is derived from the conversion rate for lime particles. The evaporation model is based on experimental data from the pilot plant slaker. The slaker model is simulated and compared to a step response experiment performed on the slaker.

Mixed continuous-time and multirate sampled-data /spl Hscr//sub /spl infin//-control

For periodic systems including continuous and sampled data measurements, a controller which minimizes the H/sub /spl infin// criterion is formulated. An algorithm for the periodic solution of the Riccati differential equation with jumps, associated with the filtering update, is also presented.<<ETX>>