> ## Documentation Index > Fetch the complete documentation index at: https://docs.generalrobotics.dev/llms.txt > Use this file to discover all available pages before exploring further. # Composite Rig > The Composite Rig as GRID drives it The Composite Rig as GRID drives it — what this robot actually implements, with the signatures it actually accepts. `make_robot("")` returns a `RemoteRobot`. Its attributes are the methods and subcomponents below, and every call runs on the robot; the driver behind it is `Rig`. Connecting neither starts nor moves the robot — it attaches to one that is already up. A method that fails on the robot arrives as `RuntimeError` naming the original error in its message. The client packages this page uses are preinstalled in every GRID session workspace and in the Python environment the GRID CLI prepares when you run a program with `skill run`; there is nothing to install. ```python theme={null} from grid_nexus_client import make_robot robot = make_robot("") ``` ## Methods on the robot Called as `robot.(...)`. ### `getState()` ```python Signature theme={null} getState(keys: Optional[Union[str, List[str]]] = None) -> Dict[str, Any] ``` Get a live state snapshot of this component's tree. Recursive walk owned by the base class, following the lifecycle template: each class contributes only the protected local hook `_local_state`, and the walk composes the per-component results into one nested mapping. Subclasses must not replace this method — per-component state belongs in `_local_state`. With no `keys`, returns this component's local state merged with one nested node per subcomponent name — the tree structure is the nesting itself, and the names mirror `subcomponents` (and therefore `serialize()` and edge introspection): a two-arm rig returns `{"left_arm": {"joint_positions": ...}, "right_arm": {...}}`, and a leaf component returns its local state alone. A component whose state could not be read (dead telemetry, not yet started, already shut down) carries an `"error"` entry — `{"error": "<ExceptionType>: <message>"}`, with its children still nested alongside — instead of its state keys. Errors are contained per node: one failing component never loses the rest of the snapshot, and the walk still descends into the failing component's children. `"error"` is reserved for that purpose, and local state keys must not collide with subcomponent names; a hook violating either is reported as that node's error. With `keys`, returns a flat mapping with one entry per match. Each key is a `/`-separated path through the component tree: every segment names a subcomponent, and the final segment may instead name an entry in that component's local state. Because structure is the nesting, a literal path is the same as plain indexing — `getState(["left_arm/joint_positions"])` returns the value of `getState()["left_arm"]["joint_positions"]` — and a path ending on a subcomponent yields that component's full nested node. Segments may use shell-style wildcards over subcomponent names — `*` matches within one chunk and `**` matches any chain of chunks — so `"*_arm/joint_positions"` fans out to one entry per arm, keyed by the concrete matched path. Wildcards never match state entries; only a literal final segment does. A key that matches nothing raises, so a typo is loud rather than silently absent. A matched component whose state read failed yields `{"error": "..."}` at its path. Keyed reads are lazy: a hook runs only where a key lands — a literal path executes the final component's hook alone (not the nodes traversed on the way), a glob executes only the matched nodes, and each component's hook runs at most once per call however many keys reach it. Components with a selective-read hook (`_local_state_entries` — every `Robot` with registered state getters) go further and execute only the getters a key names, so a `**` glob probes their registries without touching hardware. The caller pays only for the state actually requested; `**` and the no-`keys` form visit the whole tree because that is the request. State is cheap by convention: local state carries kinematics, status, and health — never bulk sensor payloads (camera frames, point clouds, scans), which stay in their dedicated methods (`getImage`, `getPointCloud`, ...). Callable on a stopped tree — reading state after a soft e-stop is when it matters most — and on a partially started one, where unstarted components report a per-node error instead of failing the call. **keys** State paths to read, or None for the full nested snapshot. A single string is shorthand for a one-element list. **Returns:** The nested state snapshot when `keys` is None, otherwise a flat mapping of matched path to state value or nested node. **Raises:** TypeError: If `keys` is neither None, a string, nor a list/tuple of strings. ValueError: If a key is empty, has an empty path segment, or matches no subcomponent path or state entry. ### `stop()` ```python Signature theme={null} stop() -> None ``` Halt all motion across this component's tree (soft e-stop). Recursive walk owned by the base class: every subcomponent is stopped first (children before their parent, leaf-to-root; siblings in `subcomponents` insertion order), then this component's own `_stop_self` hook runs. The walk is best-effort — a failing component never prevents the rest of the tree from being stopped; failures are collected and raised together after the walk completes. Components (and their subtrees) that have already been shut down are skipped. Safe to call repeatedly: stopping an already-stopped tree re-runs the hooks, which must tolerate that. Blocks until every hook has returned. Stops motion only; resources stay live and the component remains usable — telemetry and every other public method keep working on a stopped tree. Use `shutdown` to release resources. Stopping re-arms each visited component, so a later `start` re-runs the bring-up hooks — that is the stop-then-start restart path — but it does not revoke callability: only `shutdown` does that. Subclasses must not replace this method — per-component stop behavior belongs in `_stop_self`. An override may only *extend* the walk (adding a driver-specific mode, as `UR5e` does with its `immediate` escape hatch) and must delegate to `super().stop()` for the normal path; it must never re-implement the recursion. **Raises:** ComponentStopError: If one or more stop hooks raised. The walk still visited every component; the exception carries every `(component_path, exception)` pair. ## Configured children This robot owns no hardware of its own. Every robot, sensor and teleop device in it comes from the `subcomponents` block of its configuration and is reached as `robot.`, keeping the methods of its own page in this reference. ## Lifecycle and configuration The driver's own bring-up and configuration hooks. The edge runs them when the robot comes up; do not call them from a program. Note that `robot.shutdown()` on the proxy is not the method below — it is `RemoteRobot.shutdown()`, which closes your connection and leaves the robot as it was. * `addSubcomponent()` — Attach a child component under a name. * `builtin_subcomponents()` — Declare the children this class always ships with (customization point). * `configHash()` — Hash this component's serialized config subtree. * `from_config()` — Construct this component and its config-declared subtree. * `getIdentity()` — Get this component's own hardware identity (serial, model, version, MAC). * `getRobotId()` — Stable, readable identifier for a robot or rig, for a database key. * `serialize()` — Serialize this component tree back to its config envelope. * `setup_shutdown_handlers()` — Register the process-wide atexit and signal handlers for safe teardown. * `shutdown()` — Shut down this component's tree, halting motion and releasing resources. * `start()` — Bring this component's tree online (connect, enable, arm). The contract these methods implement is **Robot interface**; values returned are **grid-types** (camera reads return `Image` — call [`decode()`](/v2.3/python-api/grid-types/image) for an ndarray). You reach the robot through [`make_robot`](/v2.3/python-api/grid-nexus-client/make_robot). ## Related topics - [Python APIs](/v2.3/python-api/overview.md) - [AirGenCar](/v2.3/python-api/airgen-robots/airgencar.md) - [AirGenDrone](/v2.3/python-api/airgen-robots/airgendrone.md) - [AirGenQuad](/v2.3/python-api/airgen-robots/airgenquad.md) - [IsaacHumanoid](/v2.3/python-api/isaac-robots/isaachumanoid.md) This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.