This article presents vibration control performances of a semi-active railway vehicle suspension system using a magnetorheological damper tested on the roller rig. In order to evaluate control performances, a mathematical railway vehicle model with 15 degrees of freedom is first derived to represent the lateral, yaw and roll motions of the car body, bogie frame, and wheel set, respectively. Based on the formulated model, the design parameters of magneto-rheological damper are determined to undertake a compatible comparison with dynamic performances of conventional (existing) passive railway vehicle suspension system. The designed magneto-rheological damper is manufactured and its field-dependent damping force characteristics are experimentally evaluated. Subsequently, in order to enhance the ride quality of a railway vehicle suspension equipped with magneto-rheological damper, a skyhook controller associated with an extended Kalman filter is designed in a state space representation. The railway suspension system incorporated with the car body and two bogies is then experimentally set up on the roller rig in order to evaluate the ride quality. It is demonstrated from experimental realization of the controller that the ride quality of the suspension system with magneto-rheological damper can be significantly enhanced compared with the existing passive suspension system.
This work presents experimental assessment of the improvements to the horizontal ride quality of a railway vehicle equipped with a semi-active magneto-rheological (MR) suspension system. The assessment includes the development of a mathematical model and magnetic circuit analysis of the MR damper, the design and manufacture of MR damper, and field test on the railway. After evaluating the field-dependent damping force characteristics, the conventional passive dampers of the operational railway vehicle are replaced with the MR dampers to evaluate horizontal dynamic characteristics that directly indicates the ride quality of the railway vehicle. Various sensors are installed in the vehicle and a skyhook controller with semi-active condition is implemented to produce an appropriate input current for the generation of the desired damping force. Three periods of testing are undertaken on the railway bridge at 120 km/h and the measured data of acceleration level are recoded and presented. It is demonstrated from the measured results that the vibration can be effectively controlled by the proposed semi-active MR suspension system associated with the skyhook controller. Finally, from the vibration control responses the horizontal ride quality of railway vehicle is evaluated and presented in frequency domain.
Velopharyngeal dysfunction in cleft palate patients following the primary palate repair may result in nasal air emission, hypernasality, articulation disorder and poor intelligibility of speech. Among conservative treatment methods, speech aid prosthesis combined with speech therapy is widely used method. However because of its long time of treatment more than a year and low predictability, some clinicians prefer a surgical intervention. Thus, the purpose of this report was to increase an attention on the effectiveness of speech aid prosthesis by introducing a case that was successfully treated. In this clinical report, speech bulb reduction program with intensive speech therapy was applied for a patient with velopharyngeal dysfunction and it was rapidly treated by 5months which was unusually short period for speech aid therapy. Furthermore, advantages of pre-operative speech aid therapy were discussed.
Ride quality became a very important factor in the performance of railway vehicles according to the expansion of high-speed railways and speedup of velocity of railway vehicles. In this study, the results of applying the MR (magnetorheological) lateral damper on the secondary suspension to reduce the vibration of the car body, directly relating to the ride quality of railway vehicles, were mentioned. In order to verify the control performance of MR dampers, a 1/5 scaled railway vehicle model was constructed, and numerical simulation and experimental tests were conducted. The MR damper for the experimental tests was produced and was attached between the car body and bogie of a full scaled vehicle, and a vibration controlling test was performed to improve ride quality on a roller rig. The skyhook control algorithm was used as the controlling technique, and regarding the test results, the RMS (root mean square) value was found by compensating the frequency of the lateral vibration based on the UIC 513 R Standard about the ride quality of railway vehicles. As a result of the test, it could be confirmed that vibration was reduced by approximately 24% when attaching the MR damper between the bogie and the car body compared to when applying a passive damper.
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