In this study, the mechanical properties of the air spring used in secondary suspension systems in railway vehicles have been experimentally determined. Firstly, rubber recipes with different ...components were determined for the production of rubber material, the main raw material of the air spring. Afterward, the mechanical properties of the elastomer material to be used in the manufacture of the air spring were determined by uniaxial tensile tests and RPA (rubber process analyzer) tests were applied to the samples obtained from different types of rubber compound. The machines used for the production of air spring and the test machines used for determining the mechanical properties of the air springs were specially produced and commissioned within the scope of the study. Blasting, airtightness, lifting–expansion, vertical spring coefficient, horizontal spring coefficient and lifetime tests were carried out by using these test machines.
Dielectric elastomers represent a class of electroactive polymers that are capable of undergoing large reversible deformations when driven electrically. Pneumatically connected DE (PCDE) actuator is ...one of the prevalently used configurations, wherein an electrically driven DE membrane is connected to another passive DE membrane via an intervening air column. This paper outlines the development of a theoretical model, well-supported by experimental observations, for analyzing the dynamic electromechanical response of PCDE actuators. The underlying energetics of the model is developed in the setting of the Hamilton’s principle taking into account the effects of membrane pre-stretch, initial inflation pressure, membrane viscoelasticity, and time-dependent electric loading. An idea of pseudo air-spring, responsible for the transfer of deformation from the active to passive sides of the actuator, is introduced and the analytical expressions are developed for the coupling function. Both pressurized and depressurized states are considered in the analysis. The developed nonlinear dynamic model is then used for building insights into several influential parameters, such as initial inflation pressure, time-dependent (DC and AC) electric actuation, height of the confined air column, volume of the intervening chamber, etc. The proposed model predicts the transfer efficiency of about 80% between the active and the passive membranes. The predictive capability of the theoretical model is established through comparisons with the experimental observations. The proposed investigation can find its potential use in the design and analysis of interconnected DE actuators subjected to a dynamic electromechanical actuation.
•A theoretical model for analyzing the dynamic electromechanical response of PCDE actuator is developed.•The hypothesis of pseudo air-spring to couple the motion of two DE membranes is considered.•Euler–Lagrange’s (E–L) equation of motion is utilized to deduce the equation of motion of the PCDE actuator.•The predictive capability of the theoretical model is verified with the experimental observations.•A detailed parametric study highlighting the effect of various parameters on the dynamic response of PCDE actuator is presented.
•A novel modeling method for convoluted air springs is proposed to estimate the vertical stiffness.•Both the effects of bellow’s tensile deformation and the asymmetric structural features are ...considered in the proposed model.•The proposed model is fully solved and derived to a unified model as a function of the number of bellows.
The article presents a novel mathematical model to analyze the performance of convoluted air springs (CAS) with different numbers of bellows. The proposed mathematical model considers both the effects of bellow’s tensile deformation and the asymmetric structural features. Some key parameters such as effective area, volume, and their variation rates are derived based on geometric analysis to establish the analytical model of the vertical stiffness and maximum outer diameter. Three types of CAS with single, double, and triple bellows are designed and manufactured for testing the performances. The developed model presented in this paper is compared with another three analytical models based on different assumptions and simplified methods by comparing the estimated stiffness and maximum outer diameter. The comparison demonstrates that the proposed model in this paper has higher accuracy than that of the others and has a uniform formula as a function of the number of bellows to calculate performances of CAS. It is also shown that for the simplified model, ignoring the tensile deformation of the bellows or the asymmetry of the model will introduce large calculation errors for the stiffness up to 10.96%. The reasons for the estimated errors compared with experiment are analyzed at the end of the article.
This study proposes a novel air spring–friction pendulum system (FPS) three-dimensional isolation bearing composed of an FPS for horizontal isolation and an air spring for vertical isolation. The ...bearing has low vertical stiffness and a strong deformation capacity, which can effectively isolate long-period ground motions. A theoretical mechanical model of the three-dimensional isolation bearing is established, and mechanical behavior tests are conducted. Results show that the vertical bearing capacity of the three-dimensional isolation bearing increases linearly with the air pressure and as the applied compression increases, and the horizontal stiffness and force increase with an increase in the vertical load. This study then proposes a design method for the air spring-FPS three-dimensional isolation bearing in the large-span spatial structure. The vibration control effect of the large-span steel tubular truss structure with the three-dimensional isolation bearing under long-period ground motions is investigated. Results reveal that the bearing with low vertical stiffness can effectively isolate long-period ground motions. For the truss structure with air spring-FPS three-dimensional isolation bearing, the horizontal and vertical nodal peak accelerations decrease by 41.9%–87.0% and by 23.1%–43.1%, respectively. In addition, the member peak von Mises stress decreases by 9.8%–29.0%, and the displacement response of the bearing is within the working stroke.
•Develop a novel type of air spring-FPS three-dimensional isolation bearing.•The bearing can effectively isolate long-period ground motions.•Design method of the three-dimensional isolation bearing is proposed.•Reducing the transmission ratio can improve the isolation effect.
•A pneumatic vibration isolation platform (named VIP) with adjustable stiffness characteristics is proposed.•The stiffness model of the rubber air spring is analyzed and identified.•The dynamic ...response as well as isolation effectiveness are analyzed and simulated including: the amplitude-frequency relation, the vibration transmissibility, the frequency jump phenomena and bifurcation phenomenon of periodic solutions.•The comparing of the isolated behavior of the proposed model and equivalent linear isolator is also carried out.•The results of the simulation validate the excellent isolation effectiveness of the VIP.
This paper proposed a pneumatic vibration isolation platform (named VIP) with adjustable stiffness characteristics in which two opposite stiffness mechanisms are introduced. One with positive stiffness is formed by the wedge-roller mechanism used to support the load, which is named the load bearing mechanism (LBM), the other (called stiffness correction mechanism-SCM) generating negative stiffness in vertical direction, constructed by the cam-roller mechanism, is used for correction of the total stiffness of the VIP. Instead of using coil spring, the rubber air spring is employed, hence the stiffness of the VIP can be easily adjusted to adapt to the change of the isolated load as well as improve the isolation effectiveness in low frequency region. The force model of the rubber air spring generated by the compressed air, friction and viscoelastic is then built and identified via the experiment. Next, the dynamic stiffness model of the VIP will be established and analyzed. The primary resonant response of the proposed model subjected to harmonically excited base will be analyzed by employing the normal form technique. The effects of the configurative parameters on the amplitude-frequency curve are investigated. Furthermore, due to the nonlinear dynamical system, the complex dynamical analysis including coexistence solution, bifurcation and so on is necessary to explore in this work by using the numerical integration and Poincaré map. Finally, the isolation response of the VIP subjected to the random excitation is also evaluated and compared with that of the equivalent linear isolator (named ELI in which the SCM is removed). The result shows clearly the advantages of the VIP against the ELI. This work will furnish a useful insight into the design and manufacture of the low frequency vibration isolation systems.
In recent years, railway vehicles have become lighter since it corresponds not only to the improvement of the running speed but also to the reduction of running cost and environmental noise. On the ...other hand, this causes an increase in the vertical elastic vibration of the car body and the riding comfort has deteriorated. Therefore, various strategies to reduce vertical vibration have been studied. In this study, vertical vibration reduction, by controlling the internal pressure of the air spring using µ-synthesis control, is proposed. The merit of µ-synthesis control is that it can guarantee robust performance. A controller by µ-synthesis was designed for vibration reduction of a 1/6 scale railway model and compared nominal performance and robust performance with H
∞
control theory. Moreover, a feasibility study of this strategy was investigated for full-scale railway vehicles through simulation.
The air spring component with a damper inside is widely used in the commercial vehicle as a vibration isolator. The nonlinear dynamics of the air spring component is important for full vehicle ride ...comfort evaluation. This paper aims to develop a mechanical model of the air spring component which can reproduce the air spring characteristics correctly. The proposed model consists of three split force branches in parallel describing the nonlinear elastic characteristics based on thermodynamics, the asymmetrical hysteresis and amplitude dependence by variable Berg’s friction, and the frequency dependency with four-parameter fractional derivative model. The air spring component bench tests are conducted, and the procedure of model parameter identification and model verification is presented. The nonlinear dynamic responses of the proposed model are investigated under a large amplitude excitation and different pre-compressions/pre-elongations by comparing with the Berg’s model which uses a linear elastic force element. Additionally, the proposed model and the Berg’s model for the air spring component are separately integrated into a full vehicle multibody dynamic model to evaluate the ride comfort as application for further verification through the co-simulation method using MATLAB/Simulink and MSC.ADAMS. The proposed model is verified to be more accurate than the Berg’s model through comparison with the full vehicle ride comfort test results.
Abstract
While lifting a payload, boom machines perform a useless job to overcome gravitational forces of the working equipment gravity force. The piston spring, injected with compressed air to a ...pressure of
p
w
=10-15 MPa, ensures balancing gravitational forces of gravity during vertical movements and eliminates the indicated disadvantage. The piston air spring, independently mounted in the boom machine working equipment, represents an energy saving unit. A detailed analysis of physical processes of obtaining high-pressure compressed air for the injection into the air spring has been conducted, new solutions have been obtained, connected with the technology of air compression to high pressure, satisfying definite design requirements.
•A time domain model of the air spring with an auxiliary chamber (ASAC) system is developed and validated.•The proposed model disclosed the experimental phenomena of the orifice-type and pipe-type ...ASAC systems.•Key parameters determining the ASAC system step response are found.
The paper aims to establish analytical models for air spring with an auxiliary chamber (ASAC) to study the nonlinear characteristics of ASAC systems in the time domain. A test bench is built for measuring the dynamic characteristics of an ASAC, and the transmitted force of an ASAC is measured if harmonic and transient step displacements are applied. To calculate the transmitted force of orifice-type and pipe-type ASACs, lumped parameter models are developed, and the transmitted force are calculated by using convolution theory. Based on the established models and the measured data, model parameters are identified. The relative error for estimating transmitted force response using the proposed model is less than 6.1% compared with experiment under harmonic excitations. The characteristics that the transmitted force of an orifice-type air spring is monotonically attenuated while that of a pipe-type one is oscillating attenuated under step excitation are explained in the view of physical insight using the proposed models. Finally, a one-degree-of-freedom vibration system that assumes the stiffness and damping is provided with the proposed ASAC model is used to study the transmitted force of the mass element if step displacement excitation is applied to the base. The effects of designed parameters on the transmitted force responses of the vibration system are analyzed.
Abstract
This paper addresses the problem of dynamics of vehicle height adjustment for automobile with Double-wishbone electronically-controlled air suspension (ECAS) under considering the effects of ...suspension geometry and kinematics. The model of vehicle height adjustment consists of air spring model and suspension dynamics model. The air spring model was derived by thermodynamic theory for variable-mass gas charge/discharge system. The suspension dynamics model was formulated by kinematics analysis and dynamics modeling of double-wishbone suspension. Then, the influence of suspension geometry and kinematics on the model of vehicle height adjustment was quantitatively analyzed through simulation. Finally, Simulink-Adams co-simulation results show the accuracy of the model.
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