Energy Cost of Avoiding Pressure Oscillations in a Discrete Fluid Power Force System

In secondary valve controlled discrete fluid power force systems the valve opening trajectory greatly influences the pressure dynamics in the actuator chambers. For discrete fluid power systems featuring hoses of significant length pressure oscillations due to fast valve switching is well-known. This paper builds upon theoretical findings on how shaping of the valve opening may reduce the cylinder pressure oscillations. The current paper extents the work by implementing the valve opening characteristics reducing the pressure oscillations on a full scale power take-off test-bench for wave energy converters. Further the energy losses introduced during the shiftingperiod is investigated and compared for two valve opening algorithms. The investigation of the energy loss is utilised to quantify the importance of a fast valve switching and the energy cost of reducing pressure oscillations.The paper will present measurements comparing pressure dynamics for two valve opening algorithms. In addition the paper will give a theoretical investigation of the energy loss duringvalve shifting and finally measurements of average power output from the power take-off system in various sea states are compared for the three pressure shifting times