Hydraulic Cylinder Loads in an Automated Orchard Post-Driving Machine Determined from a Solid Model: A Basis for Selecting Control System Settings

In automated hydraulically driven agricultural machines, valve settings and motion limits are usually selected empirically, without knowing cylinder loads. These loads were predicted for the Horty AutoHammer orchard post-driving machine from its solid model, manufacturing drawings and operating manual. Forces in four hydraulic cylinders were derived using the principle of virtual work; the derivation was checked by numerical differentiation, link equilibrium and energy balance. The parallelogram linkage makes lifting force independent of tower inclination and hammer position. With the mast horizontal, the predicted tilting pressure increases linearly with hammer position from 27 to 189 bar, exceeding the 140 bar working limit above approximately 4.0 m, so mast lowering requires a hammer-position interlock. A Lagrangian model with oil compressibility yields hydraulic natural frequencies of 2.2–31 Hz. The classical ramp dynamic amplification factor, confirmed by nonlinear simulation, shows that at the full flow of one pump (56.1 L/min), tilting (hammer below mid-mast) and post lifting would require valve ramps of 3.8 and 5.2–7.4 s, exceeding the stroke times; limiting the flow to 15 and 8 L/min allows 1 s ramps. The predicted lifting pressure sensitivity of 11–58 mbar/kg indicates potential for pressure-based post detection. A validation test with predicted values is specified.