Magneto rheological (MR) fluid based dampers are very promising for semi-active or adaptive suspension control system which is filled with MR fluid. Its huge advantages attract the researchers to use it in more advanced application. MR damper's damping force can be controlled by changing the viscosity of its internal magneto-rheological fluids (MRF). However the requirement of external power source is one of the major concerns. Self-powered MR damper is one of the recent advancement which is accomplished only for double ended MR damper. In this work an energy generated mono tube MR damper has been designed and investigated with power generation which has a huge demand in the vehicle suspension system. This damper combines the advantages of energy harvesting (reusing wasted energy) and MR damping (controllable damping force). This multifunctional integration would bring great benefits such as energy saving, size and weight reduction, lower cost, high reliability, and less maintenance for the MR damper systems. The proposed MR damper model consists permanent magnet and coil combination of energy generation. Two magnetic fields are induced inside this damper. One is in the outer coil of the power generator and another is the piston head coils. A 2-D Axisymmetric model of energy generated MR damper is developed in COMSOL Multiphysics where it is analyzed extensively by finite element method and its hardware model is tested by Universal Testing Machine (UTM). The complete magnetic isolation between these two fields is accomplished here, which can be seen in the finite element analysis and damper characteristic analysis. The energy generation ability of the MR damper model is tested by UTM and oscilloscope combination and the maximum output voltage is measured around 0.8 volts by oscilloscope. Finally, experimental dampers characteristic analysis is performed by using RD-8041-1 MR Damper. These results are compared with the hardware model experimental results, which clearly validate the hardware model damper characteristic.

Better ride comfort and controllability of vehicles are pursued by automotive industries by considering the use of suspension system which plays a very important role in handling and ride comfort characteristics. Comprehensive comparison on half car model was conducted to analyze the effect of active suspension system, namely, Robust H-infinity and LQR controller on the model. Passive suspension system is also compared with active suspension technique for the purpose of benchmarking. Parametric uncertainties were also considered to model the non-linearities associated in the system. Sprung mass vertical acceleration and pitch acceleration responses were analyzed for measurements of ride quality and road handling. Suspension deflection and tire deflection responses were analyzed to identify any compromise in other aspects of vehicle dynamics. Results show that the Robust and LQR controller successfully controlled the active suspension, improving both the ride quality and handling of the vehicles without compromising the rattle-space requirement and road holding performance of the vehicles. Comparison of all models also shows that in spite of adding uncertainties in the system, the designed Robust H-infinity controller achieved better settling time than the traditional passive suspension system.

The main purpose of vehicle suspension system is to isolate the vehicle main body from any road geometrical irregularities in order to improve the passengers ride comfort and to maintain good handling characteristics subject to different road profile. This dissertation aim at establishing a mathematical model and a control strategy for a nonlinear hydraulically actuated active suspension system. A model of nonlinear, four Degree of Freedom (DOF) half vehicle active suspension system with hydraulic actuator dynamics and a similar nonlinear, four DOF half vehicle passive suspension system model was developed using Matlab/Simulink environment. A control system consisting of two controller loops was also developed, namely inner loop controller for force tracking control of the hydraulic actuator and outer loop controller to resist the effects of road induced disturbances. The outer loop controller employed a proportional integral and differential (PID) control strategy. On the other hand, a proportional integral and differential (PID) force feedback control scheme was employed in the inner loop controller to stabilize the hydraulic actuator in such a way that it is able to supply the actual force as close as possible with the optimum targeted force supplied by the PID controller. Two types of road (discrete and random) inputs were employed and a simulation study using Matlab/Simulink environment was performed to test the effectiveness and robustness of the control scheme. The performance of the active suspension system was assessed by comparing it response to that of passive suspension system. Results obtained shows that, the active suspension system developed a good dynamic response and a better ride comfort when compared to the conventional passive suspension system.

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Since the passive suspension system is not enough for creating good compromise between the road handling and ride comfort for off-road vehicles, this thesis presents a study on the application of an active suspension system. The system is considered under the Neuro-Fuzzy controller (NFC) for two and three-axle half-car off-road vehicle models. In this work, two methods are studied and employed as benchmarks for the NFC. The two methods are fuzzy logic control (FLC) method and neural networks control (NNC) method based on NARMA-L2 neurocontroller. The system designed for this study takes in two types of road disturbances as inputs, namely pothole and random road inputs. The sprung mass vertical and pitch accelerations are the criteria employed for the evaluation of the ride comfort, while the tire deflection is used for the road handling. The work's results demonstrates that, the NFC has a superior performance over the FLC and the NNC in terms of the ride comfort without compromising the rattle-space requirement, since the NFC improved the vertical acceleration of the sprung masses of the two-axle and three axle vehicle models for both the pitch and the random road disturbances more than the NNC and the FLC. On the other hand, the NFC requires higher control effort than the FLC and NNC as it gives the best performance that requires more control effort. The results are compared as well with the responses of the passive suspension system.

Nowadays, researchers are concentrating in light weight vehicle with higher speed requirement due to the increasing of competitions in all sectors of transportation industries without reducing the passenger ride comfort. But maintaining the ride quality in high speed vehicle with existing passive suspension has reached its limits. So it suggests that to overcome this problem, active suspension system should be used. The previous studies over the last few decades suggest that active suspension technology can provide better solutions to overcome the passive suspension limitation with improved passengers ride quality. The aim of this research is to concentrate on actuator technology in the active secondary suspension system of railway vehicle. This research investigated the possibilities to develop controller solution to control the actuators across the secondary suspension of a railway vehicle. After extensive literature review the electromechanical actuator is chosen across the secondary suspension of railway vehicle. To improve the performance of the actuator, a PI plus Phase advance compensator was designed before placing the actuator in the secondary suspension system. After introducing the actuator inside the suspension system, the performance of the actuator was reduced to a certain level. So to overcome this problem, retuning of the actuator controller was necessary. Additionally, to improve the performance of the total suspension system and actuator, a conventional PID and fuzzy-PID controllers were developed and implemented in the secondary suspension. These two controllers were designed to control the suspension and also actuator outputs. After simulation, an existing test rig is selected for the quarter car railway suspension system experiment. After that an electromechanical damper is designed and constructed in the laboratory. The finite element analysis (FEA) analysis of electromechanical dampers 2-D axisymmetric model has also accomplished before constructing the damper. Then, the others additional parts such as sensory systems, an arduino controller device and a relay module were installed to the test rig. Finally, the electro-dynamic shaker was introduced to complete the setup of the quarter car suspension system with proper controllers and power amplifiers. By using the shaker total three excitation inputs (sinusoidal, random and chirp) were created to test the performance of the active secondary suspension system. The overall experiment is carried out by both passive and active condition under the same (sinusoidal, random and chirp) excitation inputs. The results indicate that active suspension system provides better performance than passive suspension system in terms of vehicle body acceleration and displacement. So the ultimate outcome of this research is that after introducing active controller and electromechanical damper to the secondary suspension system, the ride quality and vehicle safety has improved over passive suspension system.

A vehicle damping characteristics is shown to be nonlinear. An empirical investigation of a simple passenger full-car model is presented. Experiments are performed on a passive damper suspension and a friction damper to obtain the characteristics of a nonlinear damper, namely, the backbone of Force versus Velocity curves in which describes nonlinear effects that depend on varying frequencies and amplitudes of the road profile. This backbone curve is applied to determine the necessary nonparametric equations. Results using the experimental parameters and the simulation models are obtained so that comparisons with respect to the performance of the damper are made. A road profile is then used to simulate a quarter car models using these nonlinear equations. Analysis of the results includes vertical acceleration of the center of gravity of sprung mass of the model in a range of frequencies.

The design of vehicle suspension systems is an active research field in which one of the objectives is to improve the passenger's comfort through the vibration reduction of the internal engine and external road disturbances. Comfort and road handling in car can be improved by including a semi-active suspension system, controlled by varying the damping based on measurements of the vehicle motions. This research deals with design and development of a quarter-car suspension using magneto-rheological damper (MR). A quarter-car of two degree-of-freedom (DOF) system is designed and constructed on the basis of the concept of a four-wheel independent suspension to simulate the actions of a semi-active vehicle suspension system. The selection of an appropriate MR damper model is crucial, since it provides the suitable current and force relationship and allows finding the appropriate force to the system. The behavioral characteristic of selected MR damper model is simulated and analyzed with different current input. An effective control structure is a key function of this research to determine the complexity of the control design and parameter tuning process. The performance of Proportional Integral Derivative (PID) and Linear Control Regulator (LQR) controller is designed based on the system requirements. In this research, the PID controller is verified experimentally under different road excitations to improve the ride quality and vehicle safety.

In designing passive suspensions, a compromise has to b~ made between ride comfort and car handling. For an off-road vehicle that requires both good ride comfort and good handling capability, a passive suspension alone is not enough. Therefore, there is a need to introduce active elements to further improve vehicle suspensions, which could offer both better ride comfort and car handling to this type of vehicle. This work deals with dynamics and control methods analysis of active suspension systems for off-road vehicles. Comprehensive comparison on three different configurations; 2- axle, 3-axle and 4-axle half-vehicle models were conducted to analyze the effect of using active control methods. The application of two control methods, namely LQR and fuzzy logic controls have been analyzed and compared with passive systems. Sprung mass vertical and pitch acceleration responses were analyzed for measurements of ride quality and road handling. Suspension deflection and tire deflection responses were observed to identify any compromise in the other aspects of vehicle dynamics. Results show that the LQR and FLC successfully controlled the active suspension, improving ride quality and handling of the vehicles without compromising the rattle-space requirement and road holding performance of the vehicles. Comparison of all models also shows that in general, improving ride quality performance will also improve vehicle handling. Moreover, it is observed that FLC control requires less amount of actuator force compared to LQR control to achieve the desired performances.