38 research outputs found
An experimental methodology to support development of yaw damper prototypes based on a hardware-in-the-loop test bench
No full textResearch and development of innovative suspension components for rail vehicles have involved huge investments in recent years. Research efforts have focussed on designing and optimising suspension systems to deal with the new challenges introduced in railway dynamics by the continuous increase in vehicle speed. In particular, yaw dampers have been a relevant research topic due to their influence on vehicle stability. In this context, this paper aims to propose a Hardware-In-the-Loop (HIL) methodology for testing yaw dampers under experimental conditions close to real operating scenarios, comparing the influence of different prototypes on the stability of high-speed rail vehicles. A reduced vehicle model is proposed for real-time integration in HIL tests. This model provides a reference stroke to be imposed on the prototype tested, considering the actual damping force provided by the device being analysed. Two yaw damper prototypes are introduced to validate the proposed methodology by means of comparative analysis at different vehicle speeds. The experimental results provided by the HIL test bench are then compared with corresponding analysis done using Multi-Body (MB) simulations. The proposed HIL methodology has proved to be able to test physical prototypes and define guidelines to assist damper manufacturers developing and optimising yaw damper components
A robust and fail-safe semi-active vertical damper to improve ride comfort
No full textIn recent years, the technical progress in railway engineering has led to the integration of electronic elements in suspension components that once were purely mechanical. Many studies have been carried out, developing active and semi-active suspensions. Among these, semi-active suspensions are particularly attractive due to their simpler design compared to fully active ones. In this context, this paper proposes a semi-active vertical damper to be implemented on the secondary suspension stage of rail vehicles. A prototype is developed by modifying a pre-existing passive damper through the addition of an external servo-valve which manages an additional by-pass channel between the compression and rebound chambers. The prototype is characterised on a dedicated test rig. A reduced vehicle model is then developed as the starting point in developing a sliding mode controller to manage the semi-active feature of the damper. A time-varying sliding surface containing the state of the system and car body accelerations is proposed. Finally, the damper prototype is tested on a hardware-in-the-loop test rig, focusing the experimental campaign on quantifying the damper performance, the evaluation of the controller robustness and a failure analysis to study the behaviour of the proposed solution even in the case of unexpected failures
On the implementation of hydraulic-interconnected-suspensions at the primary suspension stage of high-speed rail vehicles
No full textIn recent years, huge investments have been made to improve the dynamic performance of high-speed trains. Research into innovative suspension components has been part of the development of this transport system for decades. Innovative devices can allow rail vehicles to deal with the constantly increasing speed required by the global market. Among the most innovative suspension layouts proposed in railway dynamics in past years, limited attention has been given to Hydraulic Interconnected Suspensions (HIS). This layout is composed of two hydraulic cylinders with external hydraulic connections. Hydraulic Interconnected Suspensions allow promising tuning capabilities due to their ability to offer different responses based on the specific inputs given to the cylinders. This layout is rarely considered for rail vehicles, and the few previous works related to this topic considered the HIS layout to be applied at the secondary suspension stage. In this context, this paper proposes applying an HIS layout to the primary suspension stage of rail vehicles, in order to overcome the trade-offs between ride comfort, running safety and maximum car body displacement that need to be considered by bogie manufacturers when designing and optimising these mechanical systems. A nonlinear physical model of the HIS is proposed for co-simulation with a Multi-body (MB) model of a high-speed train. The improvement provided implementing an HIS at the primary suspension stage is then compared to similar enhancements that could be made when tuning and varying the standard suspension components of a bogie
Ride comfort assessment of high-speed rail vehicles: influence of yaw dampers installation angle
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A SMART PASSIVE YAW DAMPER FOR THE REDUCTION OF LATERAL CONTACT FORCES IN LOW-RADIUS CURVED TRACKS
No full textHigh-speed trains are equipped with yaw dampers to prevent the arising of hunting motion. These suspension components play an important role in improving the vehicle stability. However, the presence of yaw dampers increases the steering resistance of the bogies, especially in transient curve track segments. For this reason, passive yaw dampers are designed according to a tradeoff between improvement of high-speed stability and limitation of curving performance degradation. This paper introduces an innovative passive smart yaw damper, the Position Dependent Yaw Damper, able to overcome the typical limitations of standard passive components. The damper can variate its dynamic performances according to the operating conditions of the vehicle. In this paper, a PDYD prototype will be experimentally characterized. Then, a numerical model of the damper will be tuned on the experimental data. The model aims at predicting the influence of the PDYD on the dynamic performances of a rail vehicle, simulated with a Multibody model. A sensitivity analysis will assess the relationship between different PDYD layouts and the vehicle curving performances co-simulating damper and vehicle models. The numerical comparison will be focused on the low-speed negotiation of low radius curves. Finally, the best PDYD layout will be implemented in a numerical simulation of a high-speed high-radius curve to verify its effectiveness in reducing the arising of hunting unstable motion
Improving curving performances of high-speed rail vehicles with semi-active yaw dampers
No full textYaw dampers are equipped on rail vehicles to prevent the arising of hunting motion at high-speed running. Nevertheless, standard devices must respect a design tradeoff due to their detrimental action on the curving performances of the vehicle. In fact, the steering resistance imposed by the yaw dampers on the bogies during the low-speed negotiation of sharp curves increases the guiding contact forces with negative effects on both running safety and wheel/rail wear. This paper introduces a Switchable Yaw Damper (SYD), a semi-active on/off device designed to overcome the design tradeoff of yaw dampers by means of an additional controlled valve implemented to reduce the damping force during curve negotiation. The SYD has been prototyped, experimentally characterized, and modelled. To quantify the SYD influence on the curving performances of a rail vehicle, a multibody model has been introduced to simulate a set of real operating conditions. The curving performances of the vehicle with SYD have been compared with the ones obtained with standard yaw dampers. The comparison shows that the SYD damper technology is a simple and robust way to overcome the tradeoff that limits the design of standard yaw dampers
Influence of the yaw damper modelling on multibody simulations of rail vehicles
No full textYaw dampers are mainly characterized by dissipative behaviour. Although they are generally idealized as linear elements, they are characterized by asymmetries and nonlinearities. They also present elastic force contributions which depend on the excitation frequency. Therefore, rheological models are widely implemented in multibody co-simulation to assess the influence of on the dynamic performance of rail vehicles. Indeed, choosing specific damper models affects the results of the numerical simulations. This work aims at studying the influence of different yaw damper models on assessment of vehicle dynamic performances through multibody simulations. Two models are proposed and calibrated on a yaw damper with spool valves. A generic multibody model of a rail vehicle is introduced to study the vehicle dynamics at different operating conditions. Then, the most representative dynamic indexes related to stability, ride comfort, and curving are compared to assess their sensitivity on the damper modelling approach
Numerical modelling of a loudspeaker sound radiation and its dynamic interaction with the host structure
No full textLoudspeakers play a key role in defining the sound field and quality in various environments. Their mounting on structures with different dynamic properties affects acoustic radiation. This study presents an innovative approach that combines the equivalent sources method (ESM) with dynamic considerations to model the interaction between the loudspeaker and its support. The model decouples the loudspeaker's acoustic emission from the host structure's radiation, allowing simulations in different configurations without re-synthesizing the equivalent sources, a limitation of traditional ESM. The approach is tested on a loudspeaker mounted on a dedicated test rig with adjustable dynamic properties to measure acoustic emission under varying conditions. To contextualize its performance, the model is benchmarked against the widely used Thiele-Small model for loudspeaker simulation in complex environments. Results show that the proposed model outperforms traditional methods in predicting sound pressure and directivity, providing a reliable tool for simulating loudspeaker behavior in complex scenarios. Its simplicity and versatility make it suitable for various numerical simulation applications
Experimental analysis of a car loudspeaker model based on imposed vibration velocity: effect of membrane discretization
No full textNowadays, the research about the improvement of the interior sound quality of road vehicles is a relevant task.
The cabin is an acoustically challenging environment due to the complex geometry, the different acoustic
properties of the materials of cabin components and the presence of audio systems based on multiple loudspeaker
units. This paper aims at presenting a simplified modelling approach designed to introduce the boundary condition
imposed by a loudspeaker to the cabin system in the context of virtual acoustic analysis. The proposed model is
discussed and compared with experimental measurements obtained from a test-case loudspeaker
