The following Nav2 plugins provide basic 3D planning and control suitable for open water. They all
ignore the global and local costmaps. They all largely ignore yaw, though the
PurePursuitController3D will generate a value for yaw (angular.z) in cmd_vel.
Note for Humble: Nav2 now includes a velocity smoother node which takes cmd_vel output from the Nav2 controller(s) and does velocity, acceleration, and deadband smoothing. This node isn't 3D-aware, so it isn't used in Blue.
The StraightLinePlanner3D plugin is similar to the
StraightLinePlanner
plugin.
The planner can plan in two segments (vertical motion first, then horizontal) or one segment
(vertical and horizontal motion combined).
Parameters:
| Parameter | Type | Default | Notes |
|---|---|---|---|
| planning_dist | double | 0.1 | How far apart the plan poses are, m |
| z_before_xy | bool | false | If true plan in 2 segments: z then xy |
The PurePursuitController3D plugin is similar to the
PurePursuitController
plugin.
It limits horizontal, vertical and yaw acceleration to reduce pitching and drift.
The BlueROV2 frame is holonomic, but forward/backward drag is lower than the left/right drag, so the
controller generates diff-drive motion (linear.x, linear.z and angular.z).
Parameters:
| Parameter | Type | Default | Notes |
|---|---|---|---|
| xy_vel | double | 0.4 | Desired horizontal velocity, m/s |
| xy_accel | double | 0.4 | Max horizontal acceleration, m/s^2 |
| z_vel | double | 0.2 | Desired vertical velocity, m/s |
| z_accel | double | 0.2 | Max vertical acceleration, m/s^2 |
| yaw_vel | double | 0.4 | Desired yaw velocity, r/s |
| yaw_accel | double | 0.4 | Max yaw acceleration, r/s^2 |
| lookahead_dist | double | 1.0 | Lookahead distance for pure pursuit algorithm, m |
| transform_tolerance | double | 1.0 | How stale a transform can be and still be used, s |
| goal_tolerance | double | 0.1 | Stop moving when goal is closer than goal_tolerance. Should be less than the values in GoalChecker3D |
| tick_rate | double | 20 | The BT tick rate, used to calculate dt |
The ProgressChecker3D plugin is similar to the
SimpleProgressChecker plugin.
Parameters:
| Parameter | Type | Default | Notes |
|---|---|---|---|
| radius | double | 0.5 | Minimum distance to move, m |
| time_allowance | double | 10.0 | Time allowed to move the minimum distance, s |
The GoalChecker3D plugin is similar to the
SimpleGoalChecker plugin.
Parameters:
| Parameter | Type | Default | Notes |
|---|---|---|---|
| xy_goal_tolerance | double | 0.25 | Horizontal goal tolerance |
| z_goal_tolerance | double | 0.25 | Vertical goal tolerance |