ANTI-WINDUP LPV CONTROL DESIGN OF MR DAMPERS FOR STRUCTURAL VIBRATION SUPPRESSION

ABSTRACT Magneto-rheological (MR) dampers that belong to the family of semi-active devices are widely used for vibration atten

On the Influence of Piecewise Defined Contact Geometries on Friction Dampers

Diese Arbeit betrachtet Dämpfer, die sich nicht auf eine Schwingungsreduktionsstrategie beschränken, sondern mehrere kombinieren, um optimale Ergebnisse zu erzielen. Die Möglichkeiten herkömmlicher Reibungsdämpfer werden durch stetige, stückweise definierten Kontaktgeometrien erweitert. Dies führt zu Reibungsdämpfern, die ihr Verhalten je nach Amplitude der Schwingungen ändern. Der passive, abgestimmte Keildämpfer wird entworfen und untersucht. Dieser Dämpfer bringt Dämpfung bei hohen Schwingungsamplituden in System ein und nutzt Tilgung bei niedrigen Schwingungsamplituden aus. Es werden numerische und analytische Untersuchungen durchgeführt. Um das qualitative Verhalten des Dämpfers zu validieren, wird ein Dämpferprototyp konstruiert und erprobt. Zudem wurde auch eine aktive Variante des abgestimmten Keildämpfers betrachtet. Es werden zwei Regelstrategien entworfen, die adaptive Mehrmodellregelung und die langsame, frequenzbasierte Regelung. Diese werden mit einer State-of-the-Art- Regelungsstrategie in transienten, quasistationären und Anwendungsszenarien verglichen. Die Untersuchungen zum passiven, abgestimmten Keildämpfer zeigen, dass Dämpfung und Tilgung entkoppelt werden. Eine Optimierung der Dämpferparameter ergibt im Frequenzgang eine Reduktion der Maximalamplitude von 87.47% unter Beibehaltung der Tilgung. Die Experimente validieren den Entkopplungseffekt sowie den qualitativen Einfluss der Parameter. Die aktiven Systeme erreichen mit Amplitudenabsenkungen von 91.11% das beste Ergebnis

Blasting Vibration Monitoring and a New Vibration Reduction Measure

Vibration waves generated by blasting can cause shock to buildings. Different responses occur in different parts of the building. Therefore, a single standard is inaccurate. At the same time, methods to reduce vibration are needed. In this paper, the variation of peak particle velocity (PPV) and principal frequency was analyzed. The energy variation of blast vibration waves was analyzed by wavelet packet decomposition. A numerical model was established to verify the new vibration reduction measure. The results showed that the PPV on the walls increases with their height. The PPV and principal frequency of different structures of single-story brick-concrete buildings are different. The amplification factor of PPV does not change much when the principal frequency ratio is larger than 0.75. Measuring points at different heights have different sensitivities to blasting vibration waves of different principal frequencies. Therefore, different structures will respond differently to the same blasting operation. The PPV can be reduced by waveform interference. However, the cycle of blasting vibration waves decreases with increasing distance. Therefore, it is necessary to determine a reasonable interval to reduce the PPV. This requires further research

Blasting Vibration Monitoring and a New Vibration Reduction Measure

Vibration waves generated by blasting can cause shock to buildings. Different responses occur in different parts of the building. Therefore, a single standard is inaccurate. At the same time, methods to reduce vibration are needed. In this paper, the variation of peak particle velocity (PPV) and principal frequency was analyzed. The energy variation of blast vibration waves was analyzed by wavelet packet decomposition. A numerical model was established to verify the new vibration reduction measure. The results showed that the PPV on the walls increases with their height. The PPV and principal frequency of different structures of single-story brick-concrete buildings are different. The amplification factor of PPV does not change much when the principal frequency ratio is larger than 0.75. Measuring points at different heights have different sensitivities to blasting vibration waves of different principal frequencies. Therefore, different structures will respond differently to the same blasting operation. The PPV can be reduced by waveform interference. However, the cycle of blasting vibration waves decreases with increasing distance. Therefore, it is necessary to determine a reasonable interval to reduce the PPV. This requires further research

Design and analysis of magnetorheological dampers for train suspension.

Lau Yiu Kee.Thesis (M.Phil.)--Chinese University of Hong Kong, 2004.Includes bibliographical references (leaves 142-146).Abstracts in English and Chinese.LIST OF TABLES --- p.viiiLIST OF FIGURES --- p.xChapter 1. --- INTRODUCTION --- p.1Chapter 1.1 --- Motivation --- p.1Chapter 1.2 --- Railway Vehicle Suspension --- p.2Chapter 1.3 --- Semi-Active Magnetorheological Fluid Damper --- p.3Chapter 1.4 --- Research Objectives --- p.4Chapter 1.5 --- Thesis Outline --- p.5Chapter 2. --- BACKGROUND --- p.7Chapter 2.1 --- MR Fluids --- p.7Chapter 2.1.1 --- Composition of MR fluids --- p.7Chapter 2.1.2 --- Properties and characteristics of MR fluids --- p.8Chapter 2.1.3 --- Literature review --- p.13Chapter 2.2 --- MR Devices --- p.13Chapter 2.2.1 --- Advantages of MR devices --- p.13Chapter 2.2.2 --- Common device geometries --- p.14Chapter 2.2.3 --- MR fluid based applications --- p.15Chapter 2.2.4 --- Literature review --- p.19Chapter 2.3 --- Overview of Railway Vehicles --- p.21Chapter 2.3.1 --- "Passive, active and semi-active suspensions" --- p.21Chapter 2.3.2 --- Basic railway vehicle structure --- p.23Chapter 2.3.3 --- Literature review --- p.25Chapter 2.4 --- Railway Vehicle Suspension Systems --- p.25Chapter 2.4.1 --- Primary vertical suspension --- p.25Chapter 2.4.2 --- Secondary vertical suspension --- p.27Chapter 2.4.3 --- Secondary lateral suspension --- p.27Chapter 2.4.4 --- Yaw suspension --- p.28Chapter 3. --- DESIGN CONSIDERATIONS FOR MR DAMPERS --- p.29Chapter 3.1 --- Overview of Existing MR Dampers --- p.29Chapter 3.1.1 --- Monotube MR fluid damper --- p.29Chapter 3.1.2 --- Double-ended MR damper --- p.31Chapter 3.1.3 --- Bellow type MR damper --- p.35Chapter 3.2 --- Optimal Design and Configuration of Magnetic Circuit --- p.35Chapter 3.2.1 --- Magnetic circuit and magnetic field orientation --- p.35Chapter 3.2.2 --- Physical dimension of MR damper --- p.38Chapter 3.2.3 --- Connection polarity of electromagnetic circuit --- p.40Chapter 3.3 --- Basic Geometry Design Considerations --- p.43Chapter 3.3.1 --- Controllable force and dynamic range --- p.43Chapter 3.3.2 --- Geometry constraints --- p.45Chapter 3.3.3 --- Magnetic circuit design --- p.47Chapter 4. --- DEVELOPMENT AND FABRICATION OF MR DAMPERS --- p.51Chapter 4.1 --- Pneumatic Air Cylinder --- p.51Chapter 4.2 --- Fabrication Process of Double-Ended MR Dampers --- p.55Chapter 4.2.1 --- Modifications on the pneumatic air cylinder --- p.55Chapter 4.2.2 --- Manufacturing processes of the piston sleeve --- p.56Chapter 4.2.3 --- Modification processes of the original piston rod --- p.59Chapter 4.2.4 --- Modification of the piston staging area --- p.60Chapter 4.2.5 --- Copper wire wrapping and damper assembling --- p.63Chapter 5. --- EXPERIMENTAL SETUP AND RESULTS --- p.66Chapter 5.1 --- Experimental Setup for the Double-Ended MR Damper --- p.66Chapter 5.1.1 --- Instron 8801 loading machine --- p.66Chapter 5.1.2 --- Experimental setup for testing the MR damper --- p.67Chapter 5.2 --- Force-Lag Phenomenon of MR Damper --- p.70Chapter 5.2.1 --- Force-lag phenomenon --- p.70Chapter 5.2.2 --- Reasons of the force-lag phenomenon --- p.73Chapter 5.2.3 --- Methods to eliminate the force-lag phenomenon --- p.76Chapter 5.2.4 --- Setup for hydraulic pump system --- p.77Chapter 5.2.5 --- Results and effects of the pressurized MR damper --- p.79Chapter 5.3 --- Experimental Results for Testing the MR Damper --- p.83Chapter 6. --- SIMULATION RESULTS OF SEMI-ACTIVE TRAIN SUSPENSION --- p.87Chapter 6.1 --- MR Damper Model --- p.87Chapter 6.2 --- Rail Vehicle Model --- p.92Chapter 6.3 --- Semi-Active Railway Suspension --- p.94Chapter 6.3.1 --- Lateral vibration on the train --- p.94Chapter 6.3.2 --- Semi-active control strategy --- p.95Chapter 6.4 --- Simulation Results --- p.98Chapter 6.4.1 --- Lower sway mode excitation --- p.99Chapter 6.4.2 --- Upper sway mode excitation --- p.105Chapter 6.4.3 --- Mixed sway mode excitation --- p.110Chapter 6.4.4 --- BR high speed assault course --- p.116Chapter 6.4.5 --- Discussions --- p.124Chapter 6.5 --- Effects of Vibration on Ride Comfort --- p.128Chapter 7. --- CONCLUSIONS --- p.134APPENDIX --- p.136BIBLIOGRAPHY --- p.14

Control of large-scale structures with large uncertainties

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 279-300).Performance-based design is a design approach that satisfies motion constraints as its primary goal, and then verifies for strength. The approach is traditionally executed by appropriately sizing stiffnesses, but recently, passive energy dissipation systems have gained popularity. Semi-active and active energy dissipation systems have been shown to outperform purely passive systems, but they are not yet widely accepted in the construction and structural engineering fields. Several factors are impeding the application of semi-active and active damping systems, such as large modeling uncertainties that are inherent to large-scale structures, limited state measurements, lack of mechanically reliable control devices, large power requirements, and the need for robust controllers. In order to enhance acceptability of feedback control systems to civil structures, an integrated control strategy designed for large-scale structures with large parametric uncertainties is proposed. The control strategy comprises a novel controller, as well as a new semi-active mechanical damping device. Specifically, the controller is an adaptive black-box representation that creates and optimizes control laws sequentially during an excitation, with no prior training. The novel feature is its online organization of the input space. The representation only requires limited observations for constructing an efficient representation, which allows control of unknown systems with limited state measurements. The semi-active mechanical device consists of a friction device inspired by a vehicle drum brakes, with a viscous and a stiffness element installed in parallel. Its unique characteristic is its theoretical damping force reaching the order of 100 kN, using a friction mechanism powered with a single 12-volts battery. It is conceived using mechanically reliable technologies, which is a solution to large power requirement and mechanical robustness. The integrated control system is simulated on an existing structure located in Boston, MA, as a replacement to the existing viscous damping system. Simulation results show that the integrated control system can mitigate wind vibrations as well as the current damping strategy, utilizing only one third of devices. In addition, the system created effective control rules for several types of earthquake excitations with no prior training, performing similarly to an optimal controller using full parametric and state knowledge.by Simon Laflamme.Ph.D

Automotive suspension system modelling and controlling

In both academic and industrial fields, suspension system modelling and associated control design influence vehicle response. Ideal hydraulic force models have been used in active suspension studies for decades, but few studies have investigated hydraulic effects, which are the core of system force generation. Accurate mathematical subsystem modelling is essential in representing physical subsystems and enhancing design estimation control. This thesis details the mathematical modelling of both passive and active suspension and controller design for a quarter-car test rig. When using a conventional passive model, a significant difference between the experimental and simulation results was found for improved modelling of body movements. This led to an investigation in how to resolve this issue, accordingly, the consideration of a new term (friction force) was researched. Establishing a nonlinear friction force became a vital aspect of this work. In addition, emphasis was placed on hydraulic modelling and unknown model parameters that were experimentally identified. This experimental work is unique and helpful for advancing knowledge of any system. A new approach to implementing the friction force was used to identify the system through the transformation of a ¼ car model to one Degree of Freedom (DOF) and two-DOF models. This reduced the model complexity and allowed the parameters to be identified from a series of transfer functions linking vehicle parts and the hydraulic models. Simulation and experimental results were then compared. The hydraulic component model is crucial to the formulation of accurate active control schemes. Full-state feedback controls were realised by Pole-Assignment (PA) and Linear Quadratic (LQ) optimal method. Simulation results suggest that even though the performance of active suspension designed by the PA method is superior to that of passive suspension, it still possesses a design constraint, similar to a passive system, as the design is a compromise between the effects of natural frequency and transmissibility. With a different design concept, the LQ method provided a better solution as it reduced energy consumption by 65% and effectively shifts the dominant natural frequency to a very low-frequency range. Thus, allowing the damping rate to be increased to its critical value with the smallest effect on transmissibility. iv It was estimated for experimental work that the identified model with the LQ controller might be used to predict the dynamic responses of the actual system within a certain range of the design parameters due to the considerable difference between the initial condition of the test rig and the linearised operating design. The servovalve produced issues that did not allow validation of the controller. Both simulation and experimental results, with several conditions, showed consistent agreement, between experimental and simulation output, consequently confirming the feasibility of the newly approved model for passive and active suspension systems that accounted for the actual configuration of the test rig system. These models, that subsequently implemented the nonlinear friction forces that affect the linear supported body bearings, are entirely accurate and useful. The nonlinear friction model captures most of the friction behaviours that have been observed experimentally. Additionally, the models of the nonlinear hydraulic actuators, covered by the dynamic equation for the servovalve, are moderately precise and practical. The suggested Proportional Integral (PI) control successfully guided the road hydraulic actuator and validated the control strategy. The suggested PA and LQ controllers for active systems successfully guided the system to achieve the targets. Ride comfort and handling response are close to that expected for the passive suspension system with road disturbances, whereas there were clear response enhancements for the active system