2003 (Volume 13)
Frequency analysis of nonlinear dynamical systems and the control of vibration
|Stephen P. Banks and Maria Tomas-Rodriguez|
(University of Sheffield, UK)
In this paper we shall consider nonlinear vibrating systems which can be written in form
. We shall introduce a sequence of linear, time-varying approximations which can be studied in the frequency domain. A spectral optimal control theory will be developed.
keywords: nonlinear vibrating systems, approximation theory, optimal control.
Control system of a rotating Timoshenko beam
(Academy of Mining and Metallurgy, Poland)
(Delphi Technical Center, Poland)
In this paper the control problem of a slowly rotating Timoshenko beam is considered. Control system contains DC motor and Timoshenko beam which is attached to the disc of the machine. An algorithm for the determination of the dynamical feedback is proposed. The results of numerical computation are presented.
keywords: Timoshenko beam, parallel compensator, stability, dynamical feedback.
The influence of the friction force model on the results of the modelling and simulation tests of an active, electropneumatic vibration isolation system
|Roman Korzeniowski, Janusz Kowal and Janusz Pluta|
(University of Mining and Metallurgy, Poland)
The focus of the paper is set on modelling of active vibration isolation systems utilising electropneumatic units. Unlike the models employed to date, the presented model involves all the relationships describing the pneumatic supply system performance and takes into account all possible leaks in the pneumatic amplifier in the servovalve. The main focus is on modelling friction forces in the structural nodes of the actuator unit. The dynamic model of friction was selected. Results of numerical experiments run in MATLAB-Simulink environment were most promising and the selected model proved adequate.
keywords: vibroisolation, modelling, simulation, friction, electropneumatic control system.
Comparison of Control Strategies for Active Vibration Control of Flexible Structures
|C. Ehmann and R. Nordmann|
(Darmstadt University of Technology, Germany)
In recent years several strategies for active vibration control of weakly damped flexible structures have been presented. Depending on the type and location of actuator and sensor different control strategies lead to different performance and robustness behaviour of the closed loop. The aim of the paper is to present convenient actuator-sensor-controller combinations and to compare their closed loop performance. A test rig representing a gantry milling machine allows to validate practical applicability.
keywords: active vibration control, robust control, flexible structures, lightweight design, milling machines, piezo actuator, proof mass actuator.
Active control of vibrations of gyroscope on rocket deck
|Zbigniew Koruba and Izabela Krzysztofik|
(Kielce University of Technology, Poland)
The paper discusses errors of astatic gyroscope, located on board of a homing missile, suspended on Cardan joint. The impact of friction in suspension bearings, the base kinematic input and linear accelerations on the gyroscope axis position are also investigated. The paper gives the algorithm for the optimum correction control. Its role is to minimise the impact of rocket vibrations and manoeuvres on the gyroscope work accuracy.
keywords: homing missile, gyroscope, dynamics, control, optimisation.
Active reduction of resonant vibration in rotating shafts made of piezoelectric composites
|Piotr M. Przybylowicz|
(Warsaw University of Technology, Poland)
The paper concerns dynamic properties of rotating shafts, subjected to structural unbalance that excites transverse vibration. The shaft is made of an active composite containing piezoceramic fibers (so-called Piezoelectric Fiber Composites - PFCs). Efficiency of the applied method of active reduction of the vibration is discussed in the paper. Theoretical fundamentals of the method based on the proportional and velocity feedbacks are presented. Simulation results are shown in the form of amplitude-frequency characteristics. The investigations prove that the application of the active laminates, as elements structurally integrated with piezoelectric actuators, is an efficient tool for reducing resonant vibration amplitude in rotating shafts.
keywords: rotating shaft, resonant vibration, active damping, piezoelectric composites.
Sub-optimal fuzzy controller synthesis method taking into account control signal amplitude constraints
A method for a sub-optimal fuzzy controller synthesis taking into account the control signal amplitude constraint is presented in the paper. The control system evaluation utilizes a quadratic factor based on the vector of the state variables exclusively. An assumption is made that variations of any control signal component fall in the predetermined range. The synthesis method was developed for a TSK (Takagi-Sugeno-Kanga) fuzzy controller. The inference rules contain fuzzy antecedents and functional consequents. The fuzzy controller synthesis method requires the knowledge of the nonlinear model of the plant. The paper provides the example of synthesis of fuzzy controller for vibroisolation system, taking into account the constraints imposed on the control signal amplitude. Antecedents and consequents of inference rules are determined on the basis of an already known model of the plant to be vibro-isolated.
keywords: fuzzy control, identification, fuzzy models.
Control system of beam vibration using piezo elements
|Zdzislaw Gosiewski and Arkadiusz Sochacki|
(The Military University of Technology, Poland)
In modern mechanical constructions active damping seems to be essential. But real mechanical constructions are complicated in shape and are composed of components with distributed parameters. That is why advanced modeling techniques should be implemented in the process of designing of vibration control system. In this paper we design a vibration control system for cantilever beam. As a sensor of the beam movement and as an actuator we use piezoelectric elements coupled with hardware of dSpace and software of Matlab- Simulink. The relations describing influence of piezo-actuator on the beam bending has been found. Measurement equation for piezo sensor was also prepared. Control system was designed for a few controlled modes. The influence of control system on non-controlled modes is considered.
keywords: beam vibrations, active damping, control system, piezo element, modal control.
Autonomous control system with fuzzy capabilities for MR seat damper
(AGH - University of Science and Technology, Krakow, Poland)
The aim of the paper was to present an autonomous control system for a vehicle driver’s seat where suspension was equipped with a linear magnetorheological fluid damper (MR damper). The fuzzy controller for MR seat damper was developed on the expert knowledge acquired in the course of experimental tests of the seat, and implemented on a digital microcontroller with a fuzzy set processing unit. Then the performance of the autonomous control system with fuzzy capabilities for MR seat damper was investigated experimentally.
keywords: MR damper, driver’s seat, vibration, semi-active system, control, fuzzy logic