Design of an anti-tip-over control for counterbalance forklifts using bond graph models

摘要

Counterbalance forklifts are one of the most commonly used industrial vehicles when transporting and handling loads. However, due to the height of their center of gravity they are very unstable and prone to accidents. This paper studies a counterbalance forklift, specifically an automated guided forklift. As it is automatically controlled, it does not depend on the human factor and we can enhance safety by improving stability. The main purpose of this work is to improve forklifts' stability and, at the same time, to reduce the transportation times with the subsequent saving in operating costs. For this paper a bond graph model of a forklift has been designed and a simulation model has been developed. In this model it has been implemented a new concept of anti-tip-over controller, based on the control of the pitch angle. Several load conditions have been simulated, comparing a forklift equipped with the anti-tip-over controller developed and the same forklift without any stability controller. Comparing the transportation times in both cases, substantial improvements have been observed. In order to validate the results and ensure that the controller is perfectly feasible, a scaled prototype has been manufactured. The dynamic parameters have been also scaled, so the result can be extrapolated to the real model. Several experiments have been carried out and the controller has resulted to be perfectly stable against external disturbances, as the impact of an object when the load is raised.