ABSTRACT This paper presents the results of a study to evaluate the effect of semiactive dampers ... more ABSTRACT This paper presents the results of a study to evaluate the effect of semiactive dampers in reducing track dynamic loading at the interface between the rail and moving wheel in rail vehicles. Considering an elastic foundation for the track, the study derives a simplified dynamic model for a railcar primary suspension, attached to the wheelset (unsprung mass) and car body (sprung mass). The performance of the system for different semiactive control strategies is presented and compared with conventional passive suspensions. Different system excitations, caused by track irregularities, are considered and the performance of the system is investigated in both time and frequency domains. Simulation results show that displacement-based groundhook control strategies can reduce the dynamic loads caused by the moving wheel in the vertical direction, therefore lessening the track damage caused by high wheel loads.
Several control policies of Q-car 2-DOF semiactive system, namely skyhook, groundhook and hybrid ... more Several control policies of Q-car 2-DOF semiactive system, namely skyhook, groundhook and hybrid controls are presented. Their ride comfort, suspension displacement and road-holding performances are analyzed and compared with passive system. The analysis covers both transient and steady state responses in time domain and transmissibility response in frequency domain. The results show that the hybrid control policy yields better comfort than a passive suspension, without reducing the road-holding quality or increasing the suspension displacement for typical passenger cars. The hybrid control policy is also shown to be a better compromise between comfort, road-holding and suspension displacement than the skyhook and groundhook control policies.
In general, a vehicle suspension system can be characterized as a nonlinear dynamic system that i... more In general, a vehicle suspension system can be characterized as a nonlinear dynamic system that is subjected to unknown vibration sources, dependent on road roughness and vehicle speed. In this paper, we will present a nonlinear-model-based adaptive semiactive control algorithm developed for nonlinear systems exposed to broadband non-stationary random vibration sources that are assumed to be unknown or not measurable. If there exist unknown and/or varying parameters of the dynamic system such as mass and stiffness, then the adaptive algorithm can include a recursive least square (RLS) method for on-line system identification. Since the adaptive algorithm is developed for semiactive systems, stability is guaranteed based on the fact that the system is energy conservative. The convergence of the adaptive system, however is not guaranteed, and is investigated through a numerical approach for a specific case. The simulation results for a magneto-rheological seat suspension system with t...
Investigation of the response time of magnetorheological fluid dampers. [Proceedings of SPIE 5386... more Investigation of the response time of magnetorheological fluid dampers. [Proceedings of SPIE 5386, 63 (2004)]. Jeong-Hoi Koo, Fernando D. Goncalves, Mehdi Ahmadian. Abstract. The primary purpose of this paper is to investigate ...
This paper presents a review of the state of the art in magnetorheological technology. As magneto... more This paper presents a review of the state of the art in magnetorheological technology. As magnetorheological fluids continue to gain attention, the research and development of these fluids must keep pace. Since their invention in 1948, MR fluid development has made significant advancements. Throughout this time, MR fluids have been faced with many challenges and today, after many years of development, MR fluid formulations appear to have overcome many of these challenges. The fluids have proven to be commercially viable and well suited for many applications. The intent of this study is to provide a review of the state of the art in MR fluid technologies. To limit the scope, this study will focus on three common concerns associated with MR fluids; namely the strength of the fluid (i.e., the achievable yield stress), the stability of the fluid, and the durability of the fluid. When considering the use of a MR fluid in a particular application, it is these three areas that fall under the greatest scrutiny. The literature is rich in works devoted to addressing these concerns. Furthermore, with the great success of MR fluids and MR fluid devices, a number of the models used to describe the behavior of the fluid are also reviewed; specifically, works related to the visco-plastic modeling of MR fluids are reviewed. Models used to describe the physics behind the formation of the field induced yield stress are also reviewed.
Dynamic game theory brings together different features that are keys to many situations in contro... more Dynamic game theory brings together different features that are keys to many situations in control design: optimisation behaviour, the presence of multiple agents/players, enduring consequences of decisions and robustness with respect to variability in the environment, etc. In the presented methodology, vehicle stability is represented by a cooperative dynamic/difference game such that its two agents (players), namely the driver and the direct yaw controller (DYC), are working together to provide more stability to the vehicle system. While the driver provides the steering wheel control, the DYC control algorithm is obtained by the Nash game theory to ensure optimal performance as well as robustness to disturbances. The common two-degrees-of-freedom vehicle-handling performance model is put into discrete form to develop the game equations of motion. To evaluate the developed control algorithm, CarSim with its built-in nonlinear vehicle model along with the Pacejka tire model is used....
... SMART MATERIALS AND STRUCTURES Smart Mater. Struct. 15 (2006) 13701384 doi:10.1088/0964-1726... more ... SMART MATERIALS AND STRUCTURES Smart Mater. Struct. 15 (2006) 13701384 doi:10.1088/0964-1726/15/5/026 Application of the extended Kalman filter to control of a shape memory alloy arm Mohammad H Elahinia1 and Mehdi Ahmadian2 ...
This paper will investigate the feasibility of adopting innovative design concepts that could dec... more This paper will investigate the feasibility of adopting innovative design concepts that could decrease the dependence on bonded insulated joints for railway track monitoring. First, the purpose of insulated joints and their historical usage are examined. Next, designs that utilize track circuits are discussed. This will be followed by a section on acoustic methods, reflectometry, and robotics.
The objective of this work is to characterize the performance of MR fluid at high shear rates and... more The objective of this work is to characterize the performance of MR fluid at high shear rates and high velocities. A slit-flow rheometer has been built which allows for high speed testing of MR fluid under varying field strengths. Fluid velocities range from 3.9 m/s to 27 m/s with resulting shear rates ranging from 0.23×105 s -1 to 1.6×105 s -1. In order to evaluate the performance of the fluid, the force required to drive the fluid through the slit is measured and force-velocity characteristics are generated. The zero-field viscosity is found and results indicate that shear thinning is still present even at these high shear rates. Two magnetic field strengths were considered for the field testing (50 kA/m and 100 kA/m). Results indicate that a yield stress is still being developed in the fluid. However, as fluid velocity increases, the yield stress being developed in the fluid decreases. This reduction in the yield stress could be attributed to the dwell time, or the amount of time...
In order to develop a compact and lightweight controllable damper for space truss structures vibr... more In order to develop a compact and lightweight controllable damper for space truss structures vibration suppression, a novel double-piston magnetorheological (MR) damper is proposed. Working principle of this damper has been analyzed. One prototype damper have been designed and fabricated according to the analysis results. A series of experiments have been performed to get this prototype damper's dynamical properties. Hyperbolic tangent model have been used to describe damper's nonlinear hysteresis. After model optimization using the nonlinear least squares method, the relationship between damper force and drive currents have been acquired under different excitation conditions. Comparison between the reconstructed results and testing data indicates that the optimized model shows enough accuracy to not only present the experimental data, but also forecast the hysteretic properties of this damper.
ABSTRACT This paper presents the results of a study to evaluate the effect of semiactive dampers ... more ABSTRACT This paper presents the results of a study to evaluate the effect of semiactive dampers in reducing track dynamic loading at the interface between the rail and moving wheel in rail vehicles. Considering an elastic foundation for the track, the study derives a simplified dynamic model for a railcar primary suspension, attached to the wheelset (unsprung mass) and car body (sprung mass). The performance of the system for different semiactive control strategies is presented and compared with conventional passive suspensions. Different system excitations, caused by track irregularities, are considered and the performance of the system is investigated in both time and frequency domains. Simulation results show that displacement-based groundhook control strategies can reduce the dynamic loads caused by the moving wheel in the vertical direction, therefore lessening the track damage caused by high wheel loads.
Several control policies of Q-car 2-DOF semiactive system, namely skyhook, groundhook and hybrid ... more Several control policies of Q-car 2-DOF semiactive system, namely skyhook, groundhook and hybrid controls are presented. Their ride comfort, suspension displacement and road-holding performances are analyzed and compared with passive system. The analysis covers both transient and steady state responses in time domain and transmissibility response in frequency domain. The results show that the hybrid control policy yields better comfort than a passive suspension, without reducing the road-holding quality or increasing the suspension displacement for typical passenger cars. The hybrid control policy is also shown to be a better compromise between comfort, road-holding and suspension displacement than the skyhook and groundhook control policies.
In general, a vehicle suspension system can be characterized as a nonlinear dynamic system that i... more In general, a vehicle suspension system can be characterized as a nonlinear dynamic system that is subjected to unknown vibration sources, dependent on road roughness and vehicle speed. In this paper, we will present a nonlinear-model-based adaptive semiactive control algorithm developed for nonlinear systems exposed to broadband non-stationary random vibration sources that are assumed to be unknown or not measurable. If there exist unknown and/or varying parameters of the dynamic system such as mass and stiffness, then the adaptive algorithm can include a recursive least square (RLS) method for on-line system identification. Since the adaptive algorithm is developed for semiactive systems, stability is guaranteed based on the fact that the system is energy conservative. The convergence of the adaptive system, however is not guaranteed, and is investigated through a numerical approach for a specific case. The simulation results for a magneto-rheological seat suspension system with t...
Investigation of the response time of magnetorheological fluid dampers. [Proceedings of SPIE 5386... more Investigation of the response time of magnetorheological fluid dampers. [Proceedings of SPIE 5386, 63 (2004)]. Jeong-Hoi Koo, Fernando D. Goncalves, Mehdi Ahmadian. Abstract. The primary purpose of this paper is to investigate ...
This paper presents a review of the state of the art in magnetorheological technology. As magneto... more This paper presents a review of the state of the art in magnetorheological technology. As magnetorheological fluids continue to gain attention, the research and development of these fluids must keep pace. Since their invention in 1948, MR fluid development has made significant advancements. Throughout this time, MR fluids have been faced with many challenges and today, after many years of development, MR fluid formulations appear to have overcome many of these challenges. The fluids have proven to be commercially viable and well suited for many applications. The intent of this study is to provide a review of the state of the art in MR fluid technologies. To limit the scope, this study will focus on three common concerns associated with MR fluids; namely the strength of the fluid (i.e., the achievable yield stress), the stability of the fluid, and the durability of the fluid. When considering the use of a MR fluid in a particular application, it is these three areas that fall under the greatest scrutiny. The literature is rich in works devoted to addressing these concerns. Furthermore, with the great success of MR fluids and MR fluid devices, a number of the models used to describe the behavior of the fluid are also reviewed; specifically, works related to the visco-plastic modeling of MR fluids are reviewed. Models used to describe the physics behind the formation of the field induced yield stress are also reviewed.
Dynamic game theory brings together different features that are keys to many situations in contro... more Dynamic game theory brings together different features that are keys to many situations in control design: optimisation behaviour, the presence of multiple agents/players, enduring consequences of decisions and robustness with respect to variability in the environment, etc. In the presented methodology, vehicle stability is represented by a cooperative dynamic/difference game such that its two agents (players), namely the driver and the direct yaw controller (DYC), are working together to provide more stability to the vehicle system. While the driver provides the steering wheel control, the DYC control algorithm is obtained by the Nash game theory to ensure optimal performance as well as robustness to disturbances. The common two-degrees-of-freedom vehicle-handling performance model is put into discrete form to develop the game equations of motion. To evaluate the developed control algorithm, CarSim with its built-in nonlinear vehicle model along with the Pacejka tire model is used....
... SMART MATERIALS AND STRUCTURES Smart Mater. Struct. 15 (2006) 13701384 doi:10.1088/0964-1726... more ... SMART MATERIALS AND STRUCTURES Smart Mater. Struct. 15 (2006) 13701384 doi:10.1088/0964-1726/15/5/026 Application of the extended Kalman filter to control of a shape memory alloy arm Mohammad H Elahinia1 and Mehdi Ahmadian2 ...
This paper will investigate the feasibility of adopting innovative design concepts that could dec... more This paper will investigate the feasibility of adopting innovative design concepts that could decrease the dependence on bonded insulated joints for railway track monitoring. First, the purpose of insulated joints and their historical usage are examined. Next, designs that utilize track circuits are discussed. This will be followed by a section on acoustic methods, reflectometry, and robotics.
The objective of this work is to characterize the performance of MR fluid at high shear rates and... more The objective of this work is to characterize the performance of MR fluid at high shear rates and high velocities. A slit-flow rheometer has been built which allows for high speed testing of MR fluid under varying field strengths. Fluid velocities range from 3.9 m/s to 27 m/s with resulting shear rates ranging from 0.23×105 s -1 to 1.6×105 s -1. In order to evaluate the performance of the fluid, the force required to drive the fluid through the slit is measured and force-velocity characteristics are generated. The zero-field viscosity is found and results indicate that shear thinning is still present even at these high shear rates. Two magnetic field strengths were considered for the field testing (50 kA/m and 100 kA/m). Results indicate that a yield stress is still being developed in the fluid. However, as fluid velocity increases, the yield stress being developed in the fluid decreases. This reduction in the yield stress could be attributed to the dwell time, or the amount of time...
In order to develop a compact and lightweight controllable damper for space truss structures vibr... more In order to develop a compact and lightweight controllable damper for space truss structures vibration suppression, a novel double-piston magnetorheological (MR) damper is proposed. Working principle of this damper has been analyzed. One prototype damper have been designed and fabricated according to the analysis results. A series of experiments have been performed to get this prototype damper's dynamical properties. Hyperbolic tangent model have been used to describe damper's nonlinear hysteresis. After model optimization using the nonlinear least squares method, the relationship between damper force and drive currents have been acquired under different excitation conditions. Comparison between the reconstructed results and testing data indicates that the optimized model shows enough accuracy to not only present the experimental data, but also forecast the hysteretic properties of this damper.
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