Fixed-point Digital Controllers Research Articles

Verification of fixed-point digital controllers using direct and delta forms realizations

The extensive use of fixed-point digital controllers demands a growing effort to prevent design errors that appear in the discrete-time domain. The present article describes a novel verification methodology, which employs bounded model checking (BMC) based on satisfiability modulo theories (SMT) to verify the occurrence of the design errors, because of the finite word-length (FWL) format, in fixed-point digital controllers. Here, the performance realizations of the digital controllers realizations that use delta operators are compared to those that use traditional direct forms. The experimental results show that the delta-form realization substantially reduces the digital controllers' fragility when compared to the direct-form realization. Additionally, the proposed methodology can be very effective and efficient to verify real-world digital controllers, where conclusive results are obtained in nearly 98 % of the benchmarks.

Adaptive Real-time Power Measurement Based on IEEE Standard 1459-2010

This article presents the theoretical development and implementation of an adaptive algorithm for real-time measurement of electrical powers under sinusoidal, non-sinusoidal, balanced, and unbalanced conditions according to the definitions given by IEEE Standard 1459-2010. The algorithm is based on adaptive filter notch filter implementation, where the parameters are adjusted by tracking the amplitude and phase variations to improve the accuracy of the power measurement. The algorithm uses the filter coefficients to calculate powers, resulting in low computational burden. The results of computer simulation and practical implementation using a fixed-point digital signal controller are shown in detail, proving the accuracy and efficiency of the algorithm.

Small roundoff noise realization of fixed-point digital filters and controllers

A method for finding digital realizations of discrete-time transfer functions by fixed-point arithmetic is presented. The obtained realizations attain very small roundoff-noise intensity. This intensity is significantly smaller than the intensities that have been achieved so far. The method applies many 0-1 coefficients in the realization. It therefore requires a small number of multiplications and additions, and it is significantly faster than many other realization methods. A detailed comparison is made between this method and other existing methods for digital realization. Two different cases are investigated: a Butterworth filtering realization and the realization of an LQG (linear quadratic Gaussian) optimal controller.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A limitation to the use of a constructive approach in the stability analysis of fixed-point digital controllers

A limitation to the application of a constructive algorithm to the stability analysis of fixed-point digital controllers is demonstrated by an example. The particular system analyzed consists of a fixed-point PI digital controller regulating a first order process.