Four-Quadrant Analysis and System Design for Single-Rod Hydrostatic Actuators

In this paper, we present a novel design for single-rod hydrostatic actuators that produces a stable response in all operation quadrants. The new design, which can have different embodiments, is built upon compensating for the differential flows coming in and out of single-rod actuators, by alternately connecting cap and rod sides of the cylinder to a flow source in accordance with the energy flow direction between the circuit and the load. We show that previous quadrant division definitions result in either geometric quadrants that do not coincide with motoring and pumping operation, or misrepresentations of the actual energy exchange between the load and the cylinder. The proposed quadrant representation gives the exact information about the right operation of compensating flow valves. The efficacy of the new design has been tested on an instrumented John Deere JD-48 backhoe. Precise redirection of the compensation flow allowed for nonoscillatory motions in all quadrants of operation and various loading conditions.