An Active-Seat Suspension for Farm Vehicles (1)

Suspension with Electro-Hydraulic Servo-mechanism

Abstract

An active-seat suspension for farm vehicles with electro-hydraulic servo-mechanism was built as a trial and its characteristics were tested using a vibrator.
1. The active-seat suspension consisted of a seat, a servo-amplifier, a servo valve, a hydraulic cylinder, a hydraulic power source and a vibration sensing transducer (vibrometer).
2. For a vibration-sensing system, two methods of an acceleration-sensing system and a velocity-sensing system were used.
3. The vibrometer for the velocity-sensing system consisted of a horizontal pendulum, a spring supporting the pendulum and a relative velocity pick-up. There was a small difference in the mass of the pendulum about the axis of rotation. The natural frequency of the vibrator (ω₀) became low by the moment of inertia of the pendulum. The principle was applied to the vibrometer that the relative velocity of the pendulum was proportional to the input absolute velocity when ω₀²<<ω². It showed sufficient ability across the frequency band lower than 10Hz.
4. The response of the active-seat suspension was tested for sinusoidal and random vibration (the acceleration signals on the chassis of tractors and combines). In both of the accelerations sensing system and the velocity-sensing system, the acceleration of the seat showed a considerable decrease in comparison with the acceleration of the vibrator in the frequency range of 1 to 10Hz. In particular, acceleration transmissibilities were 0.1-0.5 in the frequency range of 2.0-5.0Hz.