Abstract
Hydraulic excavators combine closed-chain mechanisms, nonlinear hydraulic actuation, and interaction with terrain whose geometry and loading evolve during operation. Maintaining consistency among mechanical models, control, and simulation is therefore essential for evaluating complete earthmoving tasks. This paper extends the RoboCompiler-based workflow to a Doosan DX300LC-5 excavator with coupled hydraulic, soil, and material-transfer models. The physical graph retains four hydraulic cylinders, the bucket transmission, five mechanical loops, and the associated actuator effort ports. Compiled assembly, motion, and effort maps connect the mechanism to a reduced-dynamics controller and a MuJoCo plant with pressure-state actuators and a mobile undercarriage. A layered bank/loose-soil model couples cutting resistance, support, excavation, retention, spill, deposition, and terrain relaxation to bucket motion. Carried material updates the plant's bucket mass, centroid, and inertia, while a separate Pinocchio representation supports independent mechanics checks. The simulated mission combines travel, three grading stages, and two excavation cycles. The results demonstrate an integrated simulation workflow for examining excavator motion, changing payloads, and terrain modification through consistent mechanical interfaces.