BB.Message.Actuator.Command.Trajectory (bb v0.15.0)

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Command an actuator to follow a trajectory defined by waypoints.

A trajectory specifies exact position, velocity, and acceleration at each point in time, enabling smooth coordinated motion.

Fields

  • waypoints - List of waypoint maps defining the trajectory
  • repeat - Number of times to repeat: positive integer or :forever (default 1)
  • command_id - Optional reference for correlating with feedback messages

Waypoint Structure

Each waypoint is a map with:

  • position - Position at this waypoint (radians or metres)
  • velocity - Velocity at this waypoint (rad/s or m/s)
  • acceleration - Acceleration at this waypoint (rad/s² or m/s²)
  • time_from_start - Time from trajectory start (milliseconds)

Examples

alias BB.Message
alias BB.Message.Actuator.Command.Trajectory

waypoints = [
  %{position: 0.0, velocity: 0.0, acceleration: 0.5, time_from_start: 0},
  %{position: 0.1, velocity: 0.3, acceleration: 0.2, time_from_start: 100},
  %{position: 0.3, velocity: 0.4, acceleration: 0.0, time_from_start: 200},
  %{position: 0.5, velocity: 0.3, acceleration: -0.2, time_from_start: 300},
  %{position: 0.6, velocity: 0.0, acceleration: -0.5, time_from_start: 400}
]

{:ok, msg} = Message.new(Trajectory, :shoulder,
  waypoints: waypoints
)

# Repeat 5 times
{:ok, msg} = Message.new(Trajectory, :shoulder,
  waypoints: waypoints,
  repeat: 5
)

# Repeat forever (until stopped)
{:ok, msg} = Message.new(Trajectory, :shoulder,
  waypoints: waypoints,
  repeat: :forever
)

Summary

Types

t()
waypoint()

Functions

new(frame_id, attrs)

Types

t()

@type t() :: %BB.Message.Actuator.Command.Trajectory{
  command_id: reference() | nil,
  repeat: pos_integer() | :forever,
  waypoints: [waypoint()]
}

waypoint()

@type waypoint() :: %{
  position: float(),
  velocity: float(),
  acceleration: float(),
  time_from_start: non_neg_integer()
}

Functions

new(frame_id, attrs)

@spec new(
  atom(),
  keyword()
) :: {:ok, BB.Message.t()} | {:error, term()}