Magnetorheological Fluid Engine Mounts: A Review on Structure Design of Semi Active Engine Mounting

The demand for low cost, quiet operation, and increased operator comfort in automobiles and other applications requires new techniques to be developed for noise and vibration isolation. One approach to reduce noise vibration and harshness (NVH) is to develop a small low cost vibration isolator that can be used to mount components that generate vibration. Passive, semi-active and active control methods as well as different types of smart materials were studied to develop this isolator. Based on this study, the most promising approach seems to be a semi-active magnetorheological isolator. In this paper, an overview of recent advances in semi active engine mounts are presented, in term of working operation of Magnetorheological (MR) Fluid namely flow mode, shear mode, squeeze mode and mix mode. The issues are discussed with regard to the design and performance as vibration isolator device. The finding of this paper proposed the new semi active engine mounts design

Modelling and control of magnetorheological dampers for vehicle suspension systems

Magnetorheological (MR) dampers are adaptive devices whose properties can be adjusted through the application of a controlled voltage signal. A semi-active suspension system incorporating MR dampers combines the advantages of both active and passive suspensions. For this reason, there has been a continuous effort to develop control algorithms for MR-damped vehicle suspension systems to meet the requirements of the automotive industry. The overall aims of this thesis are twofold: (i) The investigation of non-parametric techniques for the identification of the nonlinear dynamics of an MR damper. (ii) The implementation of these techniques in the investigation of MR damper control of a vehicle suspension system that makes minimal use of sensors, thereby reducing the implementation cost and increasing system reliability. The novel contributions of this thesis can be listed as follows: 1- Nonparametric identification modelling of an MR damper using Chebyshev polynomials to identify the damping force from both simulated and experimental data. 2- The neural network identification of both the direct and inverse dynamics of an MR damper through an experimental procedure. 3- The experimental evaluation of a neural network MR damper controller relative to previously proposed controllers. 4- The application of the neural-based damper controller trained through experimental data to a semi-active vehicle suspension system. 5- The development and evaluation of an improved control strategy for a semi-active car seat suspension system using an MR damper. Simulated and experimental validation data tests show that Chebyshev polynomials can be used to identify the damper force as an approximate function of the displacement, velocity and input voltage. Feed-forward and recurrent neural networks are used to model both the direct and inverse dynamics of MR dampers. It is shown that these neural networks are superior to Chebyshev polynomials and can reliably represent both the direct and inverse dynamic behaviours of MR dampers. The neural network models are shown to be reasonably robust against significant temperature variation. Experimental tests show that an MR damper controller based a recurrent neural network (RNN) model of its inverse dynamics is superior to conventional controllers in achieving a desired damping force, apart from being more cost-effective. This is confirmed by introducing such a controller into a semi-active suspension, in conjunction with an overall system controller based on the sliding mode control algorithm. Control performance criteria are evaluated in the time and frequency domains in order to quantify the suspension effectiveness under bump and random road excitations. A study using the modified Bouc-Wen model for the MR damper, and another study using an actual damper fitted in a hardware-in-the-loop- simulation (HILS), both show that the inverse RNN damper controller potentially gives significantly superior ride comfort and vehicle stability. It is also shown that a similar control strategy is highly effective when used for a semi-active car seat suspension system incorporating an MR damper.EThOS - Electronic Theses Online ServiceEgyptian GovenmentGBUnited Kingdo

Soft sensors in automotive applications

2017 - 2018In this work, design and validation techniques of two soft sensors for the estimation of the motorcycle vertical dynamic have been proposed. The aim of this work is to develop soft sensors able to predict the rear and front stroke of a motorcycle suspension. This kind of information are typically used in the control loop of semi‐active or active suspension systems. Replacing the hard sensor with a soft sensor, enable to reduce cost and improve reliability of the system. An analysis of the motorcycle physical model has been carried out to analyze the correlation existing among motorcycle vertical dynamic quantities in order to determine which of them are necessary for the development of a suspension stroke soft sensor. More in details, a first soft sensor for the rear stroke has been developed using a Nonlinear Auto‐Regressive with eXogenous inputs (NARX) neural network. A second soft sensor for the front suspension stroke velocity has been designed using two different techniques based respectively on Digital filtering and NARX neural network. As an example of application, an Instrument Fault Detection (IFD) scheme, based on the rear stroke soft sensor, has been shown. Experimental results have demonstrated the good reliability and promptness of the scheme in detecting different typologies of faults as losing calibration faults, hold‐faults, and open/short circuit faults thanks to the soft sensor developed. Finally, the scheme has been successfully implemented and tested on an ARM microcontroller, to confirm the feasibility of a real‐time implementation on actual processing units used in such context. [edited by Author]XXX cicl

Hybrid Torsional Damper for Semi-Active Control of Torsional Vibrations in Rotating Machines

Rotating machinery systems experience torsional vibrations with varying frequencies to some degree during normal operation. These vibrations if not controlled properly may cause severe system performance limitation and reduction of the fatigue life. Attenuation of torsional vibrations in these systems is a challenging engineering problem and raises several important issues in industrial applications. The present research aims at developing a novel hybrid torsional vibration damper incorporating a conventional Centrifugal Pendulum Vibration Absorber (CPVA) with the Magnetorheological (MR) damper capable of suppressing torsional vibrations at different excitation frequencies. In fact, CPVA and torsional MR damper have been investigated separately in previous research, however, there has been no study reported on integrating the two systems for the attenuation of torsional vibration. In this research study, first, the governing equations of motion for both horizontal and vertical CPVA have been derived using Lagrange’s principle to investigate the effect of gravity on the dynamics and performance of CPVA. Moreover, softening nonlinear behavior of the pendulum absorber and its effect on the natural frequency of the system has been investigated. Next, a rotary MR damper prototype was optimally designed, manufactured and tested. The design process of the rotary MR damper included several critical factors, particularly, analysis and design of the magnetic circuit of the MR damper. In order to ensure efficient design of the proposed damper, a finite element (FE) model of the rotary MR damper was developed to accurately evaluate the magnetic field distribution in the MR fluid and electromagnet core generated by the built-in electromagnet. The developed FE model enables to verify the effectiveness of the proposed design configuration as well as the selected material for the MR damper components. In addition, the equation of transmitted torque has been derived and utilized to evaluate the MR damper performance. In order to obtain the optimum geometric dimensions of the designed MR damper, an optimization problem has been formulated. The combined Genetic Algorithm (GA) and Sequential Quadratic Programming (SQP) have been employed to accurately capture the global optimum solution. An experimental test set up has been designed to evaluate the fabricated rotary MR damper performance by measuring the generated damping torque and to validate simulation results obtained from the model. Subsequently, the hybrid torsional MR damper incorporating both conventional CPVA and rotary MR damper has been proposed. The CPVA has been connected to the cylindrical housing of the MR damper. The governing equations of motion of the system consisting of a rotor with attached hybrid torsional dampers have been derived to evaluate the performance of the system under current off and maximum current applied to the MR damper’s electromagnet. The results are also compared with those obtained from rotor systems with only attached CPVA and rotary MR damper. Finally, a feedback control system using the semi-active skyhook control algorithm has been developed to adaptively control the proposed hybrid torsional damper under varying external excitations. It has been shown that the suggested closed-loop feedback control algorithm can significantly improve the damper performance compared with the open-loop (current off and on) system

DEVELOPING NEW ANALYTICAL AND NUMERICAL MODELS FOR MR FLUID DAMPERS AND THEIR APPLICATION TO SEISMIC DESIGN OF BUILDINGS

Magnetorheological (MR) and Electrorheological (ER) fluid dampers provide a fail-safe semi-active control mechanism for suppressing vibration response of structures as these smart fluids can change their apparent viscosity immediately under the influence of magnetic and electrical fields, respectively. MR based damping devices have recently received appropriate attention as they have less power demand, provide better dynamic range and are less sensitive to the temperature and external contaminants as compared to their ER counterparts. This thesis studies physics-based modeling of MR fluid dampers and their application in seismic design of buildings. In the first part of thesis, MR damper modeling and its related subject are studied, while in the second part of the thesis, application of MR dampers in tuned mass damper and bracing system is investigated. The existing models, namely the phenomenological models for simulating the behavior of MR and ER dampers rely on various parameters determined experimentally by the manufacturers for each damper configuration. It is of interest to develop mechanistic models of these dampers which can be applied to various configurations so that their fundamental characteristics can be studied to develop flexible design solutions for smart structures. This research presents a formulation for dynamics analysis of ER and MR fluid dampers in flow and mix mode configurations under harmonic and random excitations. The procedure employs the vorticity transport equation and the regularization function to deal with the unsteady flow and nonlinear behaviour of ER/MR fluid in general motion. Using the developed approach, the damping force of ER/MR damper can be evaluated under any type of excitations. While tuned mass dampers are found to be effective in suppressing vibration in a tall building, integrating them with semi-active MR based control system enables them to perform more efficiently under varying external excitations. To study the application of MR damper in tuned mass damper, a forty-storey tall steel-frame building assumed to be located in the Pacific Coast region of Canada (Vancouver), designed according to the relevant Canadian code and standard, has been studied with and without semi-active and passive tuned mass dampers. The response of the structure has been studied under a variety of ground motions with low, medium and high frequency contents to investigate the performance of the optimally designed semi-active MR based tuned mass damper in comparison to that of a passive tuned mass damper. It has been shown that the semi-active MR based system modifies structural response more effectively than the conventional passive tuned mass damper in both mitigation of the maximum displacement and reduction of the settling time of the building. Finally, the effectiveness of MR damper in structural bracing has been examined. Two steel building structures, five and twenty-storey building designed according to Canadian national building code, have been modeled using the finite element method. These building structures have been equipped with MR dampers in different floors appropriately based on the seismic floor-shear distribution. The governing equations of motion of the structures integrated with MR dampers have been cast into the state space representation for the implementation of the full state LQR combined with clipped optimal control strategies. The response of building structures under passive on and active controlled modes have been obtained for low, medium and high frequency content seismic records and compared

14th Conference on Dynamical Systems Theory and Applications DSTA 2017 ABSTRACTS

From Preface: This is the fourteen time when the conference “Dynamical Systems – Theory and Applications” gathers a numerous group of outstanding scientists and engineers, who deal with widely understood problems of theoretical and applied dynamics. Organization of the conference would not have been possible without a great effort of the staff of the Department of Automation, Biomechanics and Mechatronics. The patronage over the conference has been taken by the Committee of Mechanics of the Polish Academy of Sciences and the Ministry of Science and Higher Education. It is a great pleasure that our invitation has been accepted by so many people, including good colleagues and friends as well as a large group of researchers and scientists, who decided to participate in the conference for the first time. With proud and satisfaction we welcome nearly 250 persons from 38 countries all over the world. They decided to share the results of their research and many years experiences in the discipline of dynamical systems by submitting many very interesting papers. This booklet contains a collection of 375 abstracts, which have gained the acceptance of referees and have been qualified for publication in the conference proceedings [...]

Neurofuzzy controller based full vehicle nonlinear active suspension systems

To design a robust controller for active suspension systems is very important for guaranteeing the riding comfort for passengers and road handling quality for a vehicle. In this thesis, the mathematical model of full vehicle nonlinear active suspension systems with hydraulic actuators is derived to take into account all the motions of the vehicle and the nonlinearity behaviours of the active suspension system and hydraulic actuators. Four robust control types are designed and the comparisons among the robustness of those controllers against different disturbance types are investigated to select the best controller among them. The MATLAB SIMULINK toolboxes are used to simulate the proposed controllers with the controlled model and to display the responses of the controlled model under different types of disturbance. The results show that the neurofuzzy controller is more effective and robust than the other controller types. The implementation of the neurofuzzy controller using FPGA boards has been investigated in this work. The Xilinx ISE program is employed to synthesis the VHDL codes that describe the operation of the neurofuzzy controller and to generate the configuration file used to program the FPGA. The ModelSim program is used to simulate the operation of the VHDL codes and to obtain the expected output data of the FPGA boards. To confirm that FPGA the board used as the neurofuzzy controller system operated as expected, a MATLAB script file is used to compare the set of data obtained from the ModelSim program and the set of data obtained from the MATLAB SIMULINK model. The results show that the FPGA board is effective to be used as a neurofuzzy controller for full vehicle nonlinear active suspension systems. The active suspension system has a great performance for vibration isolation. However the main drawback of the active suspension is that it is high energy consumptive. Therefore, to use this suspension system in the proposed model, this drawback should be solved. Electromagnetic actuators are used to convert the vibration energy that arises from the rough road to useful electrical energy to reduce the energy consumption by the active suspension systems. The results show that the electromagnetic devices act as a power generator, i.e. the vibration energy excited by the rough road surface has been converted to a useful electrical energy supply for the actuators. Furthermore, when the nonlinear damper models are replaced by the electromagnetic actuators, riding comfort and the road handling quality are improved. As a result, two targets have been achieved by using hydraulic actuators with electromagnetic suspension systems: increasing fuel economy and improving the vehicle performance

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