Waypoint actuator

This actuator reads the coordinates of a destination point, and moves the robot towards the given point, with the robot restricted to moving only forward, turning around its Z axis, and possibly going up and down. This controller is meant to be used mainly by non-holonomic robots.

While a robot is moving towards a given waypoint, a property of the MorseRobotClass will be changed in indicate the status of the robot. The movement_status property will take one of these values: Stop, Transit or Arrived.

The movement speed of the robot is internally adjusted to the Blender time measure, following the formula: blender_speed = given_speed * tics, where tics is the number of times the code gets executed per second. The default value in Blender is tics = 60.

This actuator also implements a simple obstacle avoidance mechanism. The blend file contains the Motion_Controller empty, as well as two additional Empty objects: Radar.L and Radar.R. These detect nearby objects to the left or right of the robot, and will instruct the robot to turn in the opposite direction of the obstacle. If the radar objects are not present, the controller will not have any obstacle avoidance, and the robot can get blocked by any object between it and the target.

Note

For objects to be detectable by the radars, they must have the following settings in the Physics Properties panel:

  • Actor must be checked
  • Collision Bounds must be checked

This will work even for Static objects

Files

  • Blender: $MORSE_ROOT/data/actuators/waypoint.blend
  • Python: $MORSE_ROOT/src/morse/actuators/waypoint.py

Local data

  • x: (float) Destination X coordinate
  • y: (float) Destination Y coordinate
  • z: (float) Destination Z coordinate
  • tolerance: (float) Radius around the target destination where the robot is considered to have reached the goal
  • speed: (float) Movement speed. Rotation speed is used as speed/2

Note

Coordinates are given with respect to the origin of Blender’s coordinate axis.

Configurable parameters

  • Speed: (float) movement speed for the robot, given in meters per second
  • Target: (string) name of a blender object in the scene. When specified, this object will be placed at the coordinates given to the actuator, to indicate the expected destination of the robot
  • ObstacleAvoidance: (boolean) if true (default), will activate obstacle avoidance if the radars are present
  • FreeZ: (boolean) if false (default), the robot is only controlled on ‘X’ and heading; if true, ‘Z’ is also controlled (for aerial or submarine robots)
  • Ignore: (string) List of property names. If the object detected by the radars has any of these properties defined, it will be ignored by the obstacle avoidance, and will not make the robot change its trajectory. Useful when trying to move close to an object of a certain kind

These properties can be changed directly from a Builder API script, as in the following example:

An example of how to change the arc object using the Builder API is show below:

from morse.builder.morsebuilder import *

# Create a waypoint controller
Motion_Controller = Actuator('waypoint')
Motion_Controller.properties(Speed = 10.0)
Motion_Controller.properties(Ignore="Victim_Tag")

Services

  • goto: (Asynchronous service) This method can be used to give a one time instruction to the actuator. When the robot reaches the destination, it will send a reply, indicating that the new status of the robot is “Stop”. The function can be called with 3 to 5 parameters, corresponding to the variables in local_data. The coordinates are mandatory, while the values for tolerance and speed can be omitted.

    Parameters

    x

    float

    y

    float

    z

    float

    tolerance

    float (optional)

    speed

    float (optional)

    Parameters: (x, y, z[, tolerance[, speed]])

  • stop: (Synchronous service) This method will instruct the robot to set its speed to 0.0, and reply immediately. If a goto request is ongoing, it will remain “pending”, as the current destination is not changed.

  • resume: (Synchronous service) Restores the speed to the same value as before the last call to the stop service. The robot will continue to the last waypoint specified.

  • get_status: (Synchronous service) Ask the actuator to send a message indicating the current movement status of the parent robot. There are three possible states: Transit, Arrived and Stop.

Applicable modifiers

  • UTM modifier: Will add an offset to the Blender coordinates according to the parameters set on the scene.
  • NED: Changes the coordinate reference to use North (X), East (Y), Down (Z)