Actuator displacement can be a cylinder extension or a local motor angle. Transmissions without a holonomic displacement map are included through an explicitly supplied velocity map and its effort dual.
Task and Actuator Maps
If actuator effort is conjugate to actuator displacement, virtual work gives the corresponding effort relationship.
Three Meanings of Reconfiguration
Model reconfiguration changes dimensions, attachments, or joint/module data between runs. It is handled by recompiling the affected paths, closures, transmissions, and inertia mappings from the edited physical records; the recompiled model describes the changed mechanism.
Computational reconfiguration changes a tree, cycle basis, or valid local velocity partition while preserving the physical mechanism. On an overlap, state and speed must be transferred through their actual coordinate transformations, including the applicable coordinate transformation. A new partition is accepted only after complete closure and rank conditions are re-established. The proposition applies to a valid switch.
Physical reconfiguration during motion adds or removes actual connections. Latching, grasping, impacts, and changing contact modes alter the admissible velocities. RoboCompiler compiles each support mode as a fixed-topology closure and schedules switches between compiled modes, as in the Go2 reference with 110 support transitions; in the reported executions, impacts and contact transitions are resolved by the contact models of the executing backends. Nonholonomic rolling constraints act at the velocity level and can enter through a separate motion layer.
Use of the Compiled Interfaces in Actuation
Feedforward derived from the same interface also reduces tracking error on Stewart and Panda. For Stewart, feedforward reduces nominal platform-position RMS from 2.375 to 0.717 mm in MuJoCo and direct PACDM–Pinocchio, and from 2.374 to 0.717 mm in PhysX. Increasing the actual payload from 8 to 14 kg while retaining the nominal feedforward model gives 0.960, 0.959, and 0.959 mm, respectively. All four PhysX cases, including timestep refinement, respect the stroke and force limits, with peak force below 152 N against the 900-N bound.
For Panda, the same-reference MuJoCo arm ablation reduces tool-position RMS from 6.224 to 0.152 mm; the removed terms include inverse dynamics, armature-acceleration compensation, and damping compensation. A separate Pinocchio tool-wrench execution gives 6.326 versus 0.150 mm. Across Kangaroo, Stewart, and Panda, these ablations show that the generated motion-to-effort interface directly supports model-based feedforward; computational savings are isolated elsewhere in the paper.
Frequently Asked Questions
What actuator displacements can RoboCompiler represent? They can be cylinder extensions or local motor angles. Transmissions without a holonomic displacement map can use an explicitly supplied velocity map and its effort dual.
What are the three meanings of reconfiguration? They are model reconfiguration, computational reconfiguration, and physical reconfiguration during motion. Each describes a different kind of change to the mechanism or its representation.
How does RoboCompiler handle physical reconfiguration during motion? It compiles each support mode as a fixed-topology closure and schedules switches between compiled modes. In the reported executions, the backends’ contact models resolve impacts and contact transitions.
How does feedforward affect the reported tracking errors? For Stewart, feedforward lowers nominal platform-position RMS to 0.717 mm in the reported MuJoCo, direct PACDM–Pinocchio, and PhysX cases. For Panda, the reported tool-position RMS falls to 0.152 mm in the MuJoCo ablation and 0.150 mm in the Pinocchio execution.