Innovative seat suspensions for whole body vibration control of heavy duty vehicles

The heavy duty vehicles have played a significant role in the construction, agriculture, mining and even military applications; they have greatly enhanced the work efficiency of human. In the meantime, the ride comfort and health of their operators have been more and more concerned; those operators need to be exposed in severe whole body vibration (WBV) for a long time. In the thesis, the seat suspensions which are regarded as the most direct way to isolate vibration to the driver are developed including the single-degree of freedom (single- DOF) one and the multiple-DOF one; the active vibration control and semi-active vibration control are both investigated. Three kinds of innovative single-DOF seat suspensions are proposed with the semi-active, active and hybrid control ways, respectively. The active seat suspension applies the rotary motor as actuator, and the scissors structure within a conventional passive seat suspension is applied to transform the rotary torque to a vertical force, thus, no additional transmission mechanism is required; three different control algorithms are designed with acceleration measurement for the active seat suspension. The semi-active seat suspension with MR damper can improve the ride comfort with less power consumption than an active seat suspension; by applying an additional active actuator with small force output, the hybrid seat suspension can greatly improve the performance of the semi-active one. The design concept is intuitive; the MR damper can suppress the high vibration energy in the resonance frequency, and then a small active force can further reduce the vibration magnitude. Different from a traditional semi-active seat suspension with MR or ER damper, an advanced semiactive seat suspension with controllable electromagnetic damper (EMD) system is proposed; two implementation methods for controlling the damping of the EMD are presented and tested. The multiple-DOF seat suspension for WBV control has been rarely reported; in this thesis, a two-layer multiple-DOF seat suspension is designed and manufactured. The proposed seat suspension can reduce the vibration of driver body in five DOFs except the yaw vibration, which has least effect on human, with only three actuators. Another advantage of a two-layer structure is that, the vertical vibration reduction can be decoupled from reducing the lateral trunk bending and forward flexion of the driver body, according to the fact that the most sensitive frequency contents of the vertical vibration to human are much higher than the frequency content of other DOFs vibrations. All the proposed seat suspensions are verified with experiments on a 6-DOF vibration platform; the experimental results indicate that all these seat suspension can improve the ride comfort and can be applied for the heavy duty vehicles