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Backends

FIGAROH's algorithms (regressor construction, calibration, identification) are written once against an abstract DynamicsBackend interface, not against a specific simulator. Swapping the simulator underneath a workflow is a config change, not a rewrite.

Available backends

Backend Formats Status Best for
Pinocchio URDF Always available (core dependency) Research & identification, CPU
MuJoCo URDF, MJCF Optional (pip install mujoco) Contact dynamics, optimal control, sparse ops
Genesis URDF, MJCF, USD Optional (pip install genesis-world) GPU, large-scale parallel/multi-robot
Isaac Sim USD, URDF Optional, requires NVIDIA Omniverse Sim-to-real, RL, synthetic data 
from figaroh.backends import get_backend, list_backends

print(list_backends())
# {'pinocchio': True, 'mujoco': True, 'genesis': False, 'isaacsim': False}

backend = get_backend("mujoco", model_path="robot.urdf")

The DynamicsBackend interface

Every backend implements the same set of rigid-body dynamics primitives, so identification/calibration code never branches on which simulator is active:

  • compute_mass_matrix(q) — M(q) in the equation of motion
  • compute_coriolis_matrix(q, v) — C(q, v̇)
  • compute_gravity_vector(q) — g(q)
  • compute_forward_kinematics(q) — per-frame position/orientation
  • compute_jacobian(q, frame) — stacked [linear; angular] geometric Jacobian
  • compute_regressor(q, v, a) — the linear-in-parameters regressor W such that τ = W(q, v̇, a) · θ; this is the core computation identification builds on
  • compute_inverse_dynamics(q, v, a) / compute_forward_dynamics(q, v, τ) — RNEA / ABA
  • nq, nv, model_format properties

A handful of methods are optional (default to NotImplementedError) because not every backend can implement them efficiently: compute_dynamics_derivatives, get_joint_names, get_frame_names, get_inertias, compute_difference/ compute_integrate (Lie-group operations for free-flyer bases), random_configuration, and get_model_object() — an escape hatch that returns the underlying pin.Model or mj.MjModel for advanced features not yet abstracted (e.g. PseudoInertia, collision models).

See figaroh.backends.base.DynamicsBackend for the full signatures.

Choosing a backend

  • Research & identification → Pinocchio or MuJoCo
  • Contact-rich tasks → MuJoCo or Genesis
  • Large-scale / parallel → Genesis (GPU)
  • Sim-to-real → Isaac Sim

Next steps