Contribution on Control Strategies of Flow-On-Demand Hydraulic Circuits

The development of an innovative flow-on-demand electrohydraulic system for mobile forestry cranes is described in the present paper. To overcome functional principle related weaknesses of conventional hydraulic-mechanical Load-Sensing systems, this work breaks up the control pressure difference related dependence of the delivered oil flow. Rather the swiveling angle of the displacement pump is calculated by summing up the single consumer oil flows corresponding to the velocity requests of the machine operator. For the electrohydraulic spool valves, several advanced control strategy concepts are discussed, each of which leading to an energy efficient
artificial but controlled undersupply. The energy saving potentials are derived from a characteristic
forestry crane duty cycle via dynamic simulation methods. Further on, the system shall be
set up in a prototype crane to validate simulation results and to pave the way to the market by
demonstrating the system performance.