Abstract
The analytical model of an air spring can be effectively used for the design of air spring equipped vehicles to provide better ride and handling characteristics along with various functions for passenger convenience. However, establishing a general model of an air spring poses particular difficulties due to the severe nonlinearities in the stiffness and the hysteresis effects, which are hardly observed in conventional coil springs. The purpose of this study is to develop a general analytic model of an air spring — one which represents the main characteristics of stiffness and hysteresis and which can be connected to a model of pneumatic systems desigined to control air spring height. To this end, the mathematical model was established on the basis of thermodynamics with the assumptions that the thermodynamic parameters do not vary with the position inside the air spring, that the air has the ideal gas property, and that the kinetic and potential energies of the air are negligible. The analysis of the model has revealed that the stiffness is affected by the volume variation, the heat transfer, and the variation of the air mass and the effective area. However, the hysteresis is mainly affected by the heat transfer and the variation of the effective area. In particular, it was revealed that the increase of the volume due to the cross-sectional area increases the stiffness, while the increase of the volume due to the other reason decreases it. In addition, the model was used to develop the sufficient stability condition, and the stability of the model was analyzed. The paper also presents the comparison between the simulation and experimental results to validate the established model and demonstrates the potential of the model to be usefully employed for the development of the air spring and its algorithm for use in a pneumatic system.
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Abbreviations
- ṁ in :
-
air mass flow rate flowing into air spring
- ṁ out :
-
air mass flow rate flowing out of air spring
- m cv :
-
air mass inside air spring
- V cv :
-
control volume of air spring
- q̇ heat :
-
heat transfer rate
- A heat :
-
area of heat transfer
- h c :
-
heat transfer coefficient
- W :
-
work performed on air spring
- h in :
-
enthalpy flowing into air spring
- h out :
-
enthalpy flowing out of air spring
- U cv :
-
internal energy inside air spring
- P cv :
-
pressure inside air spring
- P atm :
-
pressure of environment
- T cv :
-
temperature inside air spring
- T in :
-
temperature of air flowing into the air spring
- T env :
-
temperature of environment around air spring
- c v :
-
specific heat at constant volume
- c p :
-
specific heat at constant pressure
- k :
-
specific heat ratio
- R :
-
ideal gas constant
- F as :
-
force applied to vehicle body by air spring
- A eff :
-
effective area of air spring
- z :
-
vertical displacement
- z 0 :
-
magnitude of displacement sinusoid
- f :
-
frequency of displacement sinusoid
- t :
-
time
- V cv0 :
-
fixed volume of air spring
- A cs :
-
cross-sectional area of the air spring
- z max :
-
maximum displacement of bottom of air spring
- z curr :
-
current displacement of bottom of air spring
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Lee, S.J. Development and analysis of an air spring model. Int.J Automot. Technol. 11, 471–479 (2010). https://doi.org/10.1007/s12239-010-0058-5
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DOI: https://doi.org/10.1007/s12239-010-0058-5