Load control of a knuckle boom crane for forestry machines.

Abstract

For the purpose of using knuckle boom cranes, which are standard manipulators of forestry machines, for tasks besides handling and felling, locus and load control equipment for a knuckle boom crane has been developed. Functioning without a load-cell sensor, this control equipment interpolates the load value in the boom tip from position sensors and pressure gages installed in hydraulic cylinders of the knuckle boom crane. Load-cell sensors are not used because they are too expensive. Therefore, the load value in the tip is interpolated using equations of motion of the knuckle boom crane, and the measurement error is only 1kN or less at the speculation load value. In a control experiment using this speculation value, it was possible to manipulate the knuckle boom crane, while keeping the load error within 0.5kN and locus error within several cm. These errors are sufficiently small to use for forestry work. Therefore, load control of the knuckle boom crane is possible, even if a load-cell sensor is not used.