Control Algorithm For Sine Excitation On Nonlinear Systems

Document type: Conference Papers
Peer reviewed: No
Full text:
Author(s): Andreas Josefsson, Martin Magnevall, Kjell Ahlin
Title: Control Algorithm For Sine Excitation On Nonlinear Systems
Conference name: IMAC XXIV
Year: 2006
Publisher: Society for Experimental Mechanics
City: St. Louis, USA
Organization: Blekinge Institute of Technology
Department: School of Engineering - Dept. of Mechanical Engineering (Sektionen för teknik – avd. för maskinteknik)
School of Engineering S- 371 79 Karlskrona
+46 455 38 50 00
Authors e-mail:,,
Language: English
Abstract: When using electrodynamic vibration exciters to excite structures, the actual force applied to the structure under
test is the reaction force between the exciter and the structure. The magnitude and phase of the reaction force is
dependent upon the characteristics of the structure and exciter. Therefore the quality of the reaction force i.e. the
force applied on the structure depends on the relationship between the exciter and structure under test.

Looking at the signal from the force transducer when exciting a structure with a sine wave, the signal will appear
harmonically distorted within the regions of the resonance frequencies. This phenomenon is easily observed when
performing tests on lightly damped structures. The harmonic distortion is a result of nonlinearities produced by the
shaker when undergoing large amplitude vibrations, at resonances.

When dealing with non-linear structures, it is of great importance to be able to keep a constant force level as well
as a non-distorted sine wave in order to get reliable results within the regions of the resonance frequencies. This
paper presents theoretical methods that can be used to create a non-distorted sinusoidal excitation signal with
constant force level.
Subject: Mechanical Engineering\Structural Dynamics
Keywords: control algorithm, sine excitation, shaker, nonlinear, harmonic distortion