Kris Smolders

Identification of nonlinear systems using Polynomial Nonlinear State Space models

In this paper, we propose a method to model nonlinear systems using polynomial nonlinear state space equations. Obtaining good initial estimates is a major problem in nonlinear modelling. It is solved here by identifying first the best linear approximation of the system under test. The proposed identification procedure is successfully applied to measurements of two physical systems.

Average Speed Control of Reciprocating Machinery

This paper introduces average speed control (ASC), a novel way of controlling heavy-duty reciprocating machinery, such as weaving machines. Its main goal is to reduce the power consumption of such machine, by only regulating their average speed, and thus allowing for instantaneous drive speed fluctuations. Its basic structure combines a linear phase FIR-filter, which calculates a moving average, with a low-bandwidth PI controller. The paper also discusses an extension of the basic controller. That is a feedforward algorithm in order to meet the stringent transient behavior specifications for a weaving machine. Validation by means of simulations and experiments show that the controller meets all specifications

Comparison of Different Multivariable Control Design Methods Applied on Half Car Test Setup

The multivariable tracking accuracy on an automotive vibration test rig can be improved by extending the current industrial off-line iterative feedforward procedure with a real time feedback controller. This article compares three MIMO feedback control design procedures with respect to design complexity and obtained performance: (1) DK-iteration, the most common μ-synthesis method to design robust MIMO-controllers, (2) a control design based on static decoupling, which is a combination of a static input – output transformation to decouple the system, and independent SISO-controllers designed for the diagonal elements of the transformed system and (3) an inverse-based control design, which is also based on a decoupling transformation, but the decoupling is performed by a dynamic precompensator. The performance of these controllers is compared experimentally on a half car test setup. The tracking performance of the controller designs based on static or dynamic decoupling is comparable with the performance of the controller based on μ-synthesis. The decoupling-based controller designs, using standard SISO H∞ techniques, are however much simpler and more straightforward.

Multivariable control for reference tracking on half car test rig

The multivariable tracking accuracy on an automotive vibration test rig can be improved by extending the current industrial off-line iterative feedforward procedure with a real time feedback controller. This paper compares two MIMO feedback controller design procedures in practice. First DK-iteration is used. This is the most common μ-synthesis method to design robust MIMO-controllers. Secondly a controller based on decoupling design is tested. This is a two step procedure. Step one is the calculation of a transformation of the inputs and the outputs to decouple the system as accurately as possible. Step two is the design of a decentralized controller (combination of independent SISO-controllers) for the transformed system. While the control design based on decoupling, using standard SISO H∞techniques is much simpler and more straightforward, the performance is comparable to that of the controller based on μ-synthesis.

Nonparametric MIMO FRF matrix estimation using a single periodic broadband excitation

This paper presents a new method to estimate the FRF matrix of a MIMO linear time-invariant system using periodic broadband excitation. The main advantage of this method lies in the fact that a full MIMO FRF matrix can be estimated using only one experiment in contrast to other approaches that require at least as many experiments as there are inputs (Dedene et al., 2002; Guillaume et al., 1996; Pintelon and Schoukens, 2001). This yields a reduction of the experiment duration if the excitation signals are properly designed. Experimental validation of this new method on a multivariable test setup is presented