Simulation Container
docker pull bedrockdynamics/substrate-sim:ros2-nav2
| Port | Protocol | Purpose |
|---|
| 8090 | HTTP | MCP tool server |
| 9090 | gRPC | ros2-bridge (odometry streaming + twist relay) |
navigate_to
Sends a goal pose to Nav2’s NavigateToPose action server. Nav2 plans a path and drives the robot to the target, handling obstacle avoidance.
| Parameter | Type | Description |
|---|
x, y | float | Target position in meters (map frame) |
yaw | float | Target heading in radians |
follow_waypoints
Sends a sequence of waypoints to Nav2’s FollowWaypoints action server. The robot visits each waypoint in order.
| Parameter | Type | Description |
|---|
waypoints | array | List of {x, y, yaw} objects |
WASM Channels
The ChannelManifest::diff_drive() manifest defines 2 twist command channels and 3 odometry state channels at 100Hz.
Command Channels (2)
| Index | Name | Unit | Limits | Max Rate of Change |
|---|
| 0 | base/linear.x | m/s | -1.0 to 1.0 | 0.5 m/s per tick |
| 1 | base/angular.z | rad/s | -2.0 to 2.0 | 1.0 rad/s per tick |
geometry_msgs/Twist message used by differential-drive robots. linear.x is forward/backward velocity, angular.z is rotational velocity (positive = counter-clockwise).
State Channels (3)
| Index | Name | Unit | Type |
|---|
| 0 | base/odom.x | m | Position |
| 1 | base/odom.y | m | Position |
| 2 | base/odom.yaw | rad | Position |
Twist Publishing
The gRPC bridge publishes WASM velocity commands as geometry_msgs/Twist messages on the /cmd_vel topic via gz-transport. This bypasses Nav2 — when a WASM controller is active, it has direct control of the robot’s motors.
If both Nav2 and a WASM controller are sending velocity commands, the results are undefined. Use MCP tools or WASM controllers for a given task, not both simultaneously.
Example
A WASM controller that drives the robot in a slow arc:
;; Drive forward at 0.3 m/s
(call $set_command (i32.const 0) (f64.const 0.3))
;; Turn left at 0.5 rad/s
(call $set_command (i32.const 1) (f64.const 0.5))
Source Code
