Abstract
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.
Highlights
To reduce ride vibration, existing tractors mainly use rubber mounts between the tractor body and the cabin in which the operator is seated
To establish an accurate test method for deriving the spring constant and damping coefficient of a suspension, this study performed a characteristic test on a semi-active hydro-pneumatic suspension under changing velocity and current conditions, and generated force-displacement and force-velocity curves representing suspension characteristics for input into a simulation model for control logic development
A semi-active hydro-pneumatic suspension combines a hydraulic spring whose performance is determined by the characteristics of the accumulator and a semi-active damper technology controlled by the flow rate inside the suspension
Summary
To reduce ride vibration, existing tractors mainly use rubber mounts between the tractor body and the cabin in which the operator is seated. These rubber mounts have a large spring constant and a small damping coefficient, which makes them suitable for supporting weight but unsuitable for absorbing vibration transmitted to the cabin [1]. Developed large tractors are increasingly equipped with cabin suspension instead of rubber mounts to reduce cabin vibration. Sci. 2020, 10, 8992 maximum driving speed of a 100 kW-class tractor recently developed in the Republic of Korea can reach 40 km/h, there has been increasing demand for cabin suspension that reduces the impact from the ground during high-speed driving. Studies have shown that vibration is reduced when rubber mounts are replaced with cabin suspension [2]; there has been minimal research analyzing the characteristics of cabin suspension and the optimization of design factors
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