Vibrations in load handling machines can manifest at different levels: at the structure of the machine directly connected to the hydraulic actuators; at the cabin of the machine; or — for machines carrying payload not rigidly connected to the structure — at the payload. These oscillations negatively affect productivity, safety and operator comfort. Several techniques have been proposed to smooth the operation of the mechanical arms of hydraulic machines, but limited attention was so far dedicated specifically to the oscillations of the payload.
This paper introduces a frequency-based approach to reduce payload oscillation applicable for load handling machines. The proposed controller generates proper signal to the flow control valves of the hydraulic system, on the basis on the frequency analysis of pressure sensors used as feedback. The controller is composed by a series of dynamic peak filters. A first stage of frequency transformation through the FFT identifies the payload frequency and adjusts the poles of the peak filter. Then, a modulation stage is used to select the proper harmonic suitable to quantify the payload oscillation. Another peak filter enables the generation of the control. This controller has a low computational cost and it is suitable for the implementation to industrial controllers.
After describing the controller, the paper presents experimental results suitable to quantify the effectiveness of the proposed procedure, considering a particular truck mounting crane available at the authors’ research center.