scholarly journals Experimental Study on the Dynamic Characteristics of Hydro-Pneumatic Semi-Active Suspensions for Agricultural Tractor Cabins

2020 ◽  
Vol 10 (24) ◽  
pp. 8992
Author(s):  
Kyujeong Choi ◽  
Jooseon Oh ◽  
Heung-Sub Kim ◽  
Hyun-Woo Han ◽  
Jung-Ho Park ◽  
...  
Keyword(s):  
Dynamic Characteristics ◽  
Test Method ◽  
Spring Constant ◽  
Damping Coefficient ◽  
Reciprocating Motion ◽  
Active Suspensions ◽  
Low Speed ◽  
Force Velocity ◽  
Force Displacement ◽  
Displacement Diagram

This study aims to establish a test method to obtain the dynamic characteristics of hydraulic-pneumatic semi-active suspensions used in tractor cabins. Because dynamic characteristics are utilized in simulation models for developing suspension control logic and must be secured to improve control performance, an accurate test method must be established. The dynamic characteristics of the suspension, i.e., the spring constant and damping coefficient, were obtained by changing the current and velocity conditions. An exciter was used as a test device to control the displacement and velocity of the hydraulic cylinder. In order to derive the spring constant of the suspension, a low-speed reciprocating motion test was performed to obtain the force-displacement diagram and to derive the damping coefficient; 48 tests were performed under 6 velocity conditions and 8 current conditions to obtain a force-velocity diagram for each result. The spring constant of the suspension was confirmed using the slope of the trend line in the force-displacement diagram obtained through the low-speed reciprocating motion test of the suspension. In addition, the damping coefficient was calculated using the force-velocity diagram obtained through the reciprocating motion test of the suspension under various current and velocity conditions.

Comparisons Between Dynamic Characteristics of Pneumatic, Magnetorheological, and Hydraulic Shock Absorbers

2012 ◽  
Author(s):  
A. M. Salem ◽  
S. Olutunde Oyadiji
Keyword(s):  
Dynamic Characteristics ◽  
Shock Absorber ◽  
Testing Machine ◽  
Mr Damper ◽  
Nonlinear Behaviour ◽  
Hydraulic Shock ◽  
Shock Absorbers ◽  
Wide Range ◽  
Force Velocity ◽  
Force Displacement

The dynamic performance of automotive vehicles is influenced by the suspension system design. Suspensions owing damping elements with a wide range of non-linear behaviour can provide higher mobility and better ride comfort performances. Pneumatic suspensions due to their inherent nonlinear behaviour can provide high mobility performance while suspensions with MR dampers can provide this nonlinearity through the controllable damping force produced by the control of the MR fluid. The pneumatic and MR suspension models are usually developed from experimental force-displacement and force-velocity characteristics. The purpose of this paper is to measure and compare the dynamic characteristics of pneumatic, magnetorheological, and hydraulic shock absorbers. The study is carried out through measuring the characteristics of the different types of dampers at different frequencies and amplitudes using an Electro-Servo Hydraulic (ESH) testing machine. The shock absorber is subjected to sinusoidal excitation of frequency varying from 0 to 10 Hz, and amplitude varying from 0 to 10 mm. In the case of the MR damper, the tests are also done at different current levels of between 0 and 2 amp. The input displacement and acceleration to the shock absorber were measured using an LVDT (Linear Voltage Displacement Transducer) and an accelerometer, respectively while the input velocity was derived from the measured displacement and acceleration. This dual identification of the input velocity was done in order to ensure accurate representation of the velocity. The output force response of the shock absorber was measured by means of a force transducer. The force-displacement and force-velocity characteristics of each shock absorber were subsequently derived from the measured data. The results show the tunability of the MR damper characteristics in comparison to those of the pneumatic and hydraulic dampers.

Decoupling Capability of Levitation Frames for Medium-Low Speed Maglev Trains

2021 ◽  
pp. 2150178
Author(s):  
Junxiong Hu ◽  
Weihua Ma ◽  
Shihui Luo ◽  
Wan Liu ◽  
Tianwei Qu ◽  
...  
Keyword(s):  
Structural Parameters ◽  
Stability Control ◽  
Test Method ◽  
Air Spring ◽  
Low Speed ◽  
End Set

Medium-low speed maglev trains (MSMTs) with a levitation gap of only 8–10[Formula: see text]mm need an adequate decoupling capability on the levitation frames to ensure stability control in levitation, while preventing the train from rolling sideways when in landing. Based on the geometric and kinematic relationships, two types of levitation frames are studied, i.e. levitation frame with end-set air spring (LFEAS) and levitation frame with mid-set air spring (LFMAS). For each levitation frame, the decoupling process and mechanism are analyzed, the analytical equations for the kinematic attitude are derived, the decoupling capability under different excitations is calculated, along with the effect of various structural parameters assessed. In addition, a test method is designed for the rolling of the levitation frame, particularly with the anti-rolling capability of the LFMAS measured. The results indicate that oscillation of the hanger rods and anti-rolling beams can compensate for displacement when the motion of the levitation frame is decoupled, which is the key to the decoupling capability. Also, the position of the anti-rolling devices and the length of hanger rods do not affect significantly the decoupling capability. However, a longer anti-rolling beam is more conducive to decoupling, but it does not affect the anti-rolling capacity of the levitation frame. The maximum roll computed of the LFMAS is 2.84[Formula: see text]mm, which meets the anti-rolling requirement.

scholarly journals Modelling and Sensitivity Analysis of Influencing Parameters in Displacement of Dynamic Bodies

2021 ◽  
Vol 06 (05) ◽  
Author(s):  
Yokesh K.S ◽  
Keyword(s):  
Dynamic Characteristics ◽  
Vertical Displacement ◽  
Suspension System ◽  
Damping Coefficient ◽  
Vehicle Body ◽  
Dominant Factor ◽  
Spring Stiffness ◽  
Variation Of Parameters ◽  
Important Challenge ◽  
Influencing Parameters

The mathematical modelling in relation to the Six-degree freedom system of train suspension is developed and simulated for their dynamic characteristics. The important challenge in the suspension system is vertical displacement obtained from the vehicle body. To reduce vertical displacement, an analysis of the model is done by variation of parameters such as stiffness of spring and damping coefficient. The model has been created by deriving the equations of a system using Newton’s law. The developed model has the potential to analyse the dynamic characteristics of the suspension system for both displacement of the vehicle body and displacement of the wheel. The outcome of this research revealed that Secondary spring stiffness is the most dominant factor to influence the displacement of the vehicle body; Primary damping coefficient is the most dominant factor to influence displacement of the wheel.

Numerical Investigation of Static and Dynamic Characteristics of Water Hydrostatic Porous Thrust Bearings

2011 ◽  
Vol 5 (6) ◽  
pp. 773-779 ◽  
Author(s):  
Yuki Nishitani ◽  
◽  
Shigeka Yoshimoto ◽  
Kei Somaya
Keyword(s):  
Porous Material ◽  
Dynamic Characteristics ◽  
Machine Tools ◽  
Measuring Equipment ◽  
Load Capacity ◽  
Damping Coefficient ◽  
Static And Dynamic Characteristics ◽  
Thrust Bearings ◽  
Hydrostatic Bearings ◽  
Aerostatic Bearings

A moving table supported by aerostatic bearings can achieve excellent accuracy of motion because of its noncontact support and, hence, it is used in various precision machine tools and measuring equipment. However, because of low viscosity of air, the damping coefficient of aerostatic bearings is not very high, causing vibration with nanometer-order amplitudes. The accuracy of machine tools and measuring equipment could deteriorate because of this vibration. It is expected that water hydrostatic bearings would have a higher damping coefficient than aerostatic bearings due to the higher viscosity of water. In addition, water, like air, does not pollute the environment. In this paper, the static and dynamic characteristics of water hydrostatic thrust bearings using porous material were numerically investigated and comparedwith conventional pocket hydrostatic bearings with a capillary restrictor. Hydrostatic porous bearings can be easily constructed because the porous material becomes a viscous restrictor itself. It was consequently found that water hydrostatic porous thrust bearings have higher maximum load capacity and slightly lower stiffness than water bearings with a capillary restrictor.

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