Ferdinand Svaricek

Strong structural controllability of linear systems revisited

Recently, the concept of strong structural controllability has attracted renewed attention. In this context the existing literature to strong structural controllability has been revisited and some of the previous results have been found to be incorrect. Therefore, in this paper an overview of the previous results on strong structural controllability, counter-examples and a new graph-theoretic characterization of strong structural controllability are given.

On strong structural controllability of linear systems

Both a novel graphic-theoretic condition and novel algebraic conditions are presented for the strong structural controllability of linear MIMO (multiple-input multiple output) systems. These conditions can be checked by a given algorithm with a complexity O(n/sup 3/). Whereas the graph-theoretic approach is very useful for low-order systems allowing a visual inspection, the algebraic approach is especially suited for computer-aided analysis of large-scale systems. A new efficient algorithm is also given.<<ETX>>

Automotive applications of active vibration control

This paper presents results of an unique active absorber system for broad band vibration compensation where the used controller is based on an adaptive feedforward/feedback control scheme. The experimental results show that an enhanced ride comfort can be achieved by eliminating fatigue from low frequency noise and vibrations.

Strong Structural Controllability and Observability of Linear Time-Varying Systems

In this note we consider continuous-time systems ẋ(t)= A(t)x(t)+B(t)u(t), y(t)=C(t)x(t)+D(t)u(t) as well as discrete-time systems ẋ(t+1)=A(t)x(t)+B(t)u(t), y(t)= C(t)x(t)+D(t)u(t) whose coefficient matrices A, B, C and D are not exactly known. More precisely, all that is known about the systems is their nonzero pattern, i.e., the locations of the nonzero entries in the coefficient matrices. We characterize the patterns that guarantee controllability and observability, respectively, for all choices of nonzero time functions at the matrix positions defined by the pattern, which extends a result by Mayeda and Yamada for time-invariant systems. As it turns out, the conditions on the patterns for time-invariant and for time-varying discrete-time systems coincide, provided that the underlying time interval is sufficiently long. In contrast, the conditions for time-varying continuous-time systems are more restrictive than in the time-invariant case.

Self-tuning control design strategy for an electronic throttle with experimental robustness analysis

In this paper a self-tuning control design strategy for the electronic throttle is introduced. The proposed control design consists of a modified PID controller and an additional nonlinear controller that helps to compensate the nonlinearities of the plant. The control parameters are calculated automatically using an appropriate process identification algorithm. The efficiency of the proposed control design strategy is shown by experimental results. In a next step the performance loss due to aging effects is analyzed. Finally, the robustness properties with regards to environmental influences are investigated.

An improved graph-theoretic algorithm for computing the structure at infinity of linear systems

The author presents an improved graph-theoretic algorithm for computing the generic infinite zero structure of a linear system. The proposed algorithm is shown to be superior to existing algorithms for multivariable systems.<<ETX>>

Multiple sliding surface control of idle engine speed and torque reserve with load torque estimation

A novel controller based on multiple sliding surface control is adopted to automotive engine control at idle condition. The control task is to maintain the engine speed and the torque reserve at their reference values despite parameter uncertainties and variations in the intake-to-torque-production delay. Additionally, a disturbance estimator is applied to reconstruct unknown load torque disturbances based on measurements of the engine speed. A validated nonlinear simulation model is used to evaluate the performance of the closed-loop system and it is shown that the system is robust with respect to the mentioned uncertainties and disturbances.

Rapid control prototyping of active vibration control systems in automotive applications

This paper discusses the rapid controller prototyping approach used at Continental and the University of the German Armed Forces for the design and implementation of active vibration control systems. Continental has developed and implemented prototypes of active engine mounting systems on various test vehicles and demonstrated that significant reductions in noise and vibration levels are achievable.

Sufficient conditions for strong structural controllability of uncertain linear time-varying systems

In this paper, we extend the notion of strong structural controllability of linear time-invariant systems, a property that requires the controllability of each system in a specific class given by the zero-nonzero pattern of the system matrices, to the linear time-varying case ẋ (t) = A(t) · x(t) + B(t) · u(t), where A and B are matrices of analytic functions. It is demonstrated that the requirements for strong structural controllability of linear time-invariant systems are not sufficient for strong structural controllability of linear time-varying systems. Moreover, in the main result of this paper, sufficient conditions for strong structural controllability of linear time-varying systems are given and an algorithm for verifying this property is provided. Since time-invariant systems are included in the class of time-varying system, these conditions are also new sufficient conditions for strong structural controllability of time-invariant systems. Finally, the results are illustrated by means of an example.

Parameter Reduction for Disturbance Attenuation with a Discrete-Time LPV Controller

Abstract This paper considers the application of a discrete-time LPV controller technique to active noise and vibration control (ANC/AVC) based on dilated LMIs. The goal of the controller design is to reduce the excitations induced by the combustion engine and transmitted through the chassis into the passenger compartment. These vibration disturbances are quite specific and consist of a varying nominal frequency and several multiples of it. The main contribution of this paper focuses in the modeling of the multisine disturbance. A parametrization of the cosine-function is proposed requiring only two parameters for L different frequencies. This reduction is based on a least square approximation. By separating the Lyapunov matrix and the system matrix in the controller design it is possible to use a Lyapunov function with dependent Lyapunov matrices leading to less conservative results. Simulations show the benefit of this method by attenuating six predefined frequencies with only two varying parameters.