Paweł Martynowicz

MR damper based implementation of nonlinear damping for a pitch plane suspension system

Suppression of vibration transmission from working machineries and other sources is important for the normal operation of a wide range of engineering systems. Traditionally, viscous dampers with approximately linear characteristics are often used to address the issue. However, this solution can have the problem of not being able to reduce the vibration transmission over the whole range of frequencies. In recent studies, the authors have revealed, by both theoretical analysis and experimental test, that nonlinear damping can be applied to resolve the problem. The present study is concerned with the exploitation of this beneficial effect of nonlinear damping to the vibration control of a pitch plane suspension system. A magneto-rheological (MR) damper based implementation of nonlinear damping is applied to provide a novel solution to the pitch plane system vibration control problem. Simulation studies are conducted to demonstrate the effectiveness of the MR damper implementation, and the beneficial effect of nonlinear damping on the pitch plane suspension system vibration control.

Special Application Magnetorheological Valve Numerical and Experimental Analysis

The paper addresses analytical, numerical and experimental aspects of the design of magnetorheological (MR) fluid valve. Magnetic flux in valve’s cross-section is analysed with the help of finite element method (FEM) software. Based on the magnetic field intensity distribution within valve’s MR fluid annular gap, simulation model of the shock absorber equipped with newly designed MR valves is developed. Prototypes of MR valve are built and embedded in the stationary barrier of the rotary shock absorber, instead of standard, passive check valves. Simulation and preliminary experimental results comprising resistance force values as a function of angular displacement and angular velocity are presented.

Rotary Shock-Absorber with Magnetorheological Valves

The paper analyses the problem of design of the magnetorheological (MR) fluid valve to be constrained within the cylindrical hole in the stationary barrier of rotary shock-absorber. The main objective is to maximise valve’s dynamic range (i.e. controllable/passive ratio of shock-absorber’s resistance torque) thus to maximise controlled part of the pressure drop along the MR valve. To obtain this, a special type of two-winding configuration with annular fluid gap is proposed.

Vibration control of wind turbine tower-nacelle model with magnetorheological tuned vibration absorber:

Wind turbine tower dynamic load is related to the fatigue and reliability of the structure. This paper deals with the problem of tower vibration control using specially designed and built numerical and laboratory model. The regarded wind turbine tower-nacelle model consists of vertically arranged stiff rod (representing the tower), and a stiff body fixed at its top representing nacelle assembly that is equipped with horizontally aligned tuned vibration absorber (TVA) with magnetorheological (MR) damper. To model tower-nacelle dynamics, Comsol Multiphysics finite element method environment was used. For time and frequency domain numerical analyses (including first and second bending modes of vibration) of system with TVA and MR damper models, MATLAB/Simulink environment was used with Comsol Multiphysics tower-nacelle model embedded. Force excitation sources applied horizontally to the nacelle, and to the tower itself were both considered. The MR damper real-time control algorithms, including ground hook control and its modification, sliding mode control, linear and nonlinear (cubic and square root) damping, and adaptive solutions are compared to the open-loop case with various constant MR damper input current values and system without MRTVA (i.e. MRTVA in ‘locked’ state). Comprehensive numerical analyses results are presented along with Vensys 82 full-scale tower-nacelle model validation. Finally, preliminary results of laboratory tests are included.

Development of Laboratory Model of Wind Turbine's Tower-Nacelle System with Magnetorheological Tuned Vibration Absorber

The paper addresses the consecutive development stages of laboratory model of wind turbines tower-nacelle system with horizontally aligned tuned vibration absorber at its top. To cope with system uncertainties and possibly multiple modes of vibration, tuned vibration absorber is equipped with MR damper instead of passive viscous one. Several laboratory model constraints have to be fulfilled. Discrete frequency-based and Comsol-Simulink analyses were conducted to determine and verify model parameters. Finally, sketch of laboratory test rig design was presented.

An Investigation of The Behaviour of Magnetorheological Fluids in the Rotary Shock-Absorber

The main aim of the article was to present the investigation results of created megnetorheological fluids using carbonyl iron (CI) particles and analyse their behaviour in terms of the internal structure formation by a control of external magnetic field. Results of the experimental studies of a prototype magnetorheological rotary shock-absorber at various magnitudes of control current was presented in this paper.

Control of a magnetorheological tuned vibration absorber for wind turbine application utilising the refined force tracking algorithm

This work covers selected control issues, including refined force tracking algorithm formulation, concerning the wind turbine tower-nacelle laboratory model equipped with a magnetorheological damper based tuned vibration absorber. The objective of the current research is a development and experimental implementation of the control algorithm that couples basic adaptive stiffness solution with stock magnetorheological damper force tracking concept to obtain a quality tower vibration reduction system. The experiments were conducted assuming monoharmonic, horizontal excitation applied to the assembly modelling the nacelle. The frequency range comprised the neighbourhood of the first bending mode of the tower-nacelle system. The results proved the effectiveness of the adopted algorithm referring to other high-performance solutions.

Dynamic Similarity of Wind Turbine's Tower-Nacelle System and its Scaled Model

A paper presents analysis of dynamic similarity between full-scale wind turbines tower-nacelle system and its laboratory model. As a reference real-world structure, Vensys 82 wind turbine was assumed. Complete and partial similarity criteria were both introduced. Considering laboratory model to be equipped with tuned mass damper horizontally arranged at the top, partial similarity of one pair of points (tower tips) motions will be satisfactory. On the basis of similarity conditions, laboratory model parameters were determined so that data acquired for the model may be referred to real-world structure.

Real-time implementation of nonlinear optimal-based vibration control for a wind turbine model

In the present paper, a real-time implementation of a previously introduced nonlinear optimal-based vibration control method is presented. A vibrating structure, namely a wind turbine tower-nacelle laboratory model equipped with a tuned vibration absorber, is analysed. For control purposes, a magnetorheological damper is used in a tuned vibration absorber system. Force constraints of a magnetorheological damper are an intrinsic part of the implemented nonlinear technique. The aim of the current research is to experimentally investigate the influence of nonlinear optimal-based vibration control law quality index elements’ weights on the vibration attenuation effectiveness along with the magnetorheological damper stroke amplitude, maximum control current or force. As a reference, simple, optimal-based, modified ground-hook law with the sole control objective of primary structure deflection minimisation is used in addition to the passive systems with constant magnetorheological damper current values, proving the benefits of the proposed solution.