Level luffing control system for crawler cranes

A level luffing control system for crawler cranes has been developed. By using this system, an operator can safely keep suspended loads level at elevated spots or on sites where visual operation is impossible. This system consists of a microcomputer-based controller, sensors (boom angle, rope length, boom lever pressure, engine speed) and hydraulic actuators. The control algorithm is the combination of feedback and feedforward control. Nonlinear compensation and gain scheduling by engine speed are also added. The effect of this algorithm was verified by numerical simulations and experimental tests. We could keep the suspended load level in the accuracy within 0.15 m by only boom operation. And the system has been put to practical use.