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← Part of the SO-101 module

Simulated Models

Model devrel:so101:simulated

The simulated arm component emulates the SO-101 arm entirely in software, with no hardware required. It shares the same kinematics as the devrel:so101:arm model, so it is useful for developing and testing configs, motion plans, and the 3D scene viewer without a physical robot.

When commanded to a joint configuration, the simulated arm interpolates its joints toward the target over time at a configurable speed, like rdk's builtin simulated arm. It also serves 3D meshes for each link, so it renders as an SO-101 in the visualizer.

Configuration

{}

All attributes are optional, so the simulated arm works with an empty configuration.

Attributes

The following attributes are available for the simulated arm component:

Name Type Inclusion Description
speed_degs_per_sec float Optional How fast each joint travels toward its target, in degrees per second. Default is 90.
motion string Optional Name of the motion service used to plan MoveToPosition requests. Default is "builtin".
simulate_time bool Optional Whether a background goroutine advances the arm's position in real time. Default is true. (Tests set it to false to drive the simulated clock.)
visualize_ee_frame bool Optional When true, serves a colored XYZ coordinate-frame marker at the end-effector for the 3D viewer. Default is false.
use_urdf bool Optional When true, sources kinematics and collision geometry from the bundled assets/urdf/so101.urdf instead of the embedded so101.json, and requires VIAM_MODULE_ROOT (viam-server sets this). A drop-in swap — frame names, TCP, and kinematics are identical; only the collision geometry upgrades from primitive shapes to per-link meshes. Default false.
mesh_decimation_ratios []float Optional Per-mesh simplification ratios, one per arm link in document order (base, shoulder, upper_arm, lower_arm, wrist). Only values strictly inside (0, 1) decimate; lower is more aggressive. Used only with use_urdf. Defaults to 0.9 for all five.
orientation_tolerance_deg float Optional Half-angle, in degrees, of the cone of acceptable end-effector approach directions around the goal orientation, used by MoveToPosition. Roll about that axis is NOT constrained. Range [0, 180]; 0/unset means 30. See Approach-axis orientation planning.
position_tolerance_mm float Optional Per-axis positional leeway, in millimetres, of the MoveToPosition goal cloud. Default 1.0. See Approach-axis orientation planning.
Example configuration with attributes: 
{
  "speed_degs_per_sec": 60
}

DoCommand

Get Motion Parameters

Retrieve the configured joint speed:

{
  "command": "get_motion_params"
}

Behavior

  • MoveToJointPositions, MoveThroughJointPositions, and GoToInputs interpolate the joints toward each target over time; the calls block until the arm arrives.
  • MoveToPosition plans through the motion service. As with the devrel:so101:arm model, it attaches an approach-axis cone (orientation_tolerance_deg/position_tolerance_mm) to the goal by default instead of ignoring orientation — see Approach-axis orientation planning above for the config attributes, the extra escape hatches, and the viam-server version requirement.
  • JointPositions, EndPosition, Geometries, and IsMoving report the simulated state.

Model devrel:so101:simulated-gripper

The simulated gripper emulates the SO-101 gripper entirely in software, with no hardware required. It serves the gripper meshes (a static body plus a moving jaw/trigger) to the 3D scene viewer, with the moving part posed by the gripper's opening — useful for developing and previewing without a physical robot.

Open opens the gripper and Grab closes it, interpolating the jaw open/closed over time so it animates in the 3D viewer (like the simulated arm). Both block until the motion finishes, and IsMoving reports true while the jaw is travelling. A simulated gripper never grasps an object, so Grab always reports false.

Configuration

{}

All attributes are optional, so the simulated gripper works with an empty configuration.

Attributes

Name Type Inclusion Description
gripper_type string Optional Which gripper meshes to serve: follower (moving jaw, the default) or leader (thumb-loop handle + trigger).
mesh_detail string Optional Gripper mesh resolution: low (decimated, the default) or high (full resolution). The mesh is also the motion-planning collision geometry, so low keeps planning fast; set high on a second gripper for a visual side-by-side.

The simulated gripper reports the same TCP reference frame as the hardware gripper — see Reference frame (TCP).

DoCommand

Set Position

Set a target opening percentage (0 = closed, 100 = open); the jaw interpolates toward it:

{
  "command": "set_position",
  "percentage": 50
}

Get Position

{
  "command": "get_position"
}