Secondary Control of a Digital Hydraulic Motor for Winch Applications

Master's thesis Mechatronics MAS500 - University of Agder 2018The reliable traditional hydraulic systems for industrial purposes is being challenged by an emerging technology called digital hydraulics. This technology shows promising improvements in regards to e ciency, especially in comparison to systems dependent on hydraulic pumps or motors with variable displacement. Digital hydraulic motors eliminate the need for a servo valve by connecting each individual motor cylinder directly to the high-pressure and low-pressure line by means of fast-acting on/o -valves. In this thesis, the potential of digital hydraulics is investigated by developing a control system intended for a digital displacement motor used on an industrial winch application. The expected operation modes of the winch system are analysed, and di erent control strategies are discussed. The developed control system is tested for the expected operation modes before it is simulated with a model of an industrial winch. The digital displacement motor performs well during simulated testing of typical load cases for a winch system. Some challenges are discovered when the motor switches operation mode and when the reference velocity is zero. Solutions for counteracting the mentioned challenges are implemented, and further possible improvements are proposed. The presented results prove that the suggested control strategy has the potential for good reference tracking and that the overall solution is suitable for a winch system