Observer-Based Hybrid Position Holding for an Electrohydraulic Agricultural Hitch: A Two-Chamber Virtual-Prototype Stress Test

Electrohydraulic holding is evaluated as a trade-off between accuracy, main-source throughput and finite storage. A symmetric virtual plant represents chamber pressures, spool lag, leakage, friction and gas storage. Component ablations and equal-budget comparisons distinguish sensing, dwell and controller effects. Corrected active sliding-mode control has lower nominal means on the four previously evaluated objectives than the earlier hybrids. A separate resource-oriented search gives each policy nine gain pairs and three complete development paths. On four independent normal-supply validation seeds, the selected hybrid/sliding-mode boundary resource is 22.47/209.32 kJ, with RMSE 1.208/0.309 mm; both pass the declared 10 mm screen. Chamber continuity explains why stationary piston/pressure holding during supply disconnection requires storage inflow and a return path. A separately frozen 88-path study includes eight new joint parameter/sensing vectors with a 1200 s supply interruption in 1800 s simulations. Scalar and availability-aware hybrids each pass 8/8 with storage and 1/8 without under the declared error/drop screens. The availability rule reduces mean within-interruption maximum error from 3.571 to 1.173 mm while increasing mean storage use from 286.68 to 409.74 mL. Both-port-blocked failures remain archived. These conditional theoretical results establish neither total-energy savings, globally resource-optimal tuning, physical reliability nor global nonlinear stability.