Study on pitching vibration control for forklift truck

Abstract

Forklift trucks, a typical distribution vehicle, have a vibration problem in the vertical direction between 2 and 3 Hz, which is induced by surface roughness of the road. This vibration reduces not only the comfort of the operator, but also the distribution efficiency due to load collapse during travelling. Mainly because this type of vehicle deals with heavy loads, conventional elastic suspension cannot be adopted on these vehicles. Therefore, effective design improvement could not be proposed and applied to the whole-body vibration of the vehicle. Recently, with a view to improving working conditions and reducing the environmental impact from exhaust gas, many battery-powered electric forklift vehicles are replacing conventional diesel engine ones. This allows for larger scope to suggest design improvements that could reduce vibration by using some electric devices. In this paper, we propose a new type of control system using the induction motor which drives front tire to reduce pitching vibration by observing the pressure of the lift cylinder. In order to develop this system, we built a fundamental mathematical model to investigate the control rule, and then verified the performance of the controller on both system design and computer simulation of multibody dynamics. Finally, we measured a large increase in damping for an actual vehicle with a prototype of the control system.