Development of 2-DOF Active Seat Suspension System for Agricultural Tractor - Design of Mechanism and Controller

摘要

The drivers of agricultural tractors are exposed to a low frequency vibration during working. In order to improve the riding comfort of a driver, a passive seat suspension system mounted on a spring-damper assembly has been used fora long time. But the passive system isolates vibration only in certain frequency and amplifies other frequencies. It cannot realistically attenuate the entire frequency range of whole-body vibration, specifically in the range of 1-7 Hz. To solve this problem, in this studya 2-DOF (degree of freedom) active seat suspension system and its controller were designed to suppress vibrations better than the passive system in the entire harmful frequency range of whole-body vibration. A 2-DOF active suspension system was designedto isolate vertical and pitch angle vibration. The vertical motion of the designed active seat suspension system was achieved with a pair of parallel motion scissor mechanism on seat base frame. A tilting platform attached on upper frame of active seatsuspension was designed for pitch angle motion. Also the designed active seat suspension system was controlled by electro-hydraulic servo. And each DOF motion was controlled independently using hydraulic actuator. The response test was conducted in orderto verify the performance of the designed active seat suspension system. From the results of the test, the designed active seat suspension was working stably in the frequency range of 0~5Hz, and up to the maximum frequency of 10 Hz. Accurate vibration cancellation for the active seat suspension system and accurate excitation of vibration for the test stand were accomplished without deterioration of working performance.