1,721,158 research outputs found
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
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
On the implementation of hydraulic-interconnected-suspensions at the primary suspension stage of high-speed rail vehicles
Full text linkIn 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
Full text linkAn H2 norm approach for the actuator and sensor placement in vibration control of a smart structure
No full textIn active vibration control of smart structures, the actuator and sensor placement is a key point
of the control system design. Even the most robust control logics could easily make a structure
unstable if the actuators and sensors were not correctly positioned. The objective of this paper
is to propose an H2 norm approach for the actuator and sensor placement. Unlike most modal
H2 norm actuator and sensor placement methodologies, this work aims not only to maximize
the norms of the controlled modes but also to reduce spillover problems by taking into account
the residual modes and minimizing their H2 norms. It discusses the optimal actuator and
sensor configuration in a finite element model of a square plate fixed on three sides with
piezoelectric patch actuators and acceleration sensors. Finally, downstream of the actuator and
sensor positioning, IMSC, PPF and NDF controls have been tested and discussed
An optimal approach in negative derivative feedback control gain synthesis
No full textVibration control logics based on the modal approach allow to increase damping on a certain number of modes. The main limit associated with these strategies is represented by spillover on non modeled modes. Negative Derivative Feedback shows to be particularly robust against spillover since modal velocity is fed back through a band-pass filter so that undesired effects can be limited both at high and low frequencies. In this paper a design strategy for NDF controller based on an optimal approach is proposed for single and multi-degrees of freedom systems and tested on a cantilever beam finite element model
metodo di trattamento di una soletta per un'attrezzatura di scivolamento
No full textMetodo di trattamento di una soletta (11) atta ad essere utilizzata in
un'attrezzatura di scivolamento (10) e provvista di almena una superficie
di scorrimento (21); il metodo comprende almena una prima fase di
5 incisione della soletta (11) mediante la quale viene realizzata sulla
superficie di scorrimento (21) una pluralita di crateri (22) di profondita
(P) e diametro (D) controllati ed almena una seconda fase di
strutturazione e finitura di tale superficie di scorrimento (21) in zone di
tale superficie di scorrimento (21) definite all' intemo dei crateri (22) e/o
lOin zone di tale superficie di scorrimento (21) definite tra un cratere (22) e
l'altro, in modo da ottenere una pluralita di rilievi (24) distribuiti sulla
superficie di scorrimento (21) della soletta (11) in tali crateri (22) e/o tra
un cratere (22) e l' altro.
Fig.
A negative derivative feedback design algorithm
Full text linkVibration control logics based on the modal approach allow damping to be increased on a certain number of modes. The main limit associated with these strategies is represented by spillover on non-modelled modes. Negative derivative feedback (NDF) proves particularly robust against spillover since modal velocity is fed back through a band-pass filter so that undesired effects can be limited both at high and low frequencies. Unfortunately, the definition of the control gains for this logic is generally more difficult than other resonant controls owing to the lack of physical meaning. In this paper a design strategy for an NDF controller based on an optimal approach is proposed for single and multi-degrees of freedom systems and is tested on a cantilever beam finite element model
The active modal tuned mass damper (AMTMD) for vibration suppression in flexible structures
No full textAn Application of the IMSC on a Non-linearFlexible Structure: Numerical Analysis and Experimental Validation
No full textThe independent modal control to suppress the
vibration of nonlinear flexible structures is applied in this
paper. Technological improvements in the mechanical field
showed during the recent years have led to high-performance
systems with low weight and, as a consequence, high flexibility
and low damping. Here active control quickly bettered the
traditional passive damping systems. The structure
investigated in this paper is a multi-body flexible boom moved
by hydraulic actuators. The nonlinear system dynamic was
numerically modeled and a control strategy, based on the use
of the same actuators, was developed. Finally a test rig was
created to experimentally validate the proposed approach
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