Vibration damping for a hydraulic driven luffing cylinder at a boom crane using feedforward control

Oscillations in the cylinder force of a boom crane effect the high-cycle fatigue of the cylinder and hence decrease the life-time of the whole crane structure resulting in higher maintenance. Thus it is desired to reduce the stress cycles in the cylinder force due to unwanted dynamics in the hydraulic driven luffing cylinder of the boom crane. To suppress the oscillations in the cylinder force due to the hydraulic eigendynamics and excited through motions of the crane's boom two different control approaches are proposed and compared in the paper. It is required that the controller only consists of feedforward terms, since feedback controllers depend on sensor signals which must fulfill certain security requirements in industrial applications resulting in higher costs. The control approaches are a Finite Impulse Response (FIR) filter suppressing one nominal frequency and a flatness based feedforward controller inverting the system dynamics. Both control approaches are evaluated and compared with simulation and measurement results obtained at a real harbor mobile crane of Liebherr.