Moving Targets

This repo contains ROS/Gazebo models and plugins for the purpose of moving lifelike objects in simulation.

Usage

Note that the namespace targets/<model name> is hardcoded and that the parameters must be available within the targets/<model name> namespace in the rosparam server.

Demo

To see it in action, run roslaunch moving_targets test.launch.

Set up Trajectories

There are five types of trajectories that can be created: goToPoint, waypoints, circle, ellipse, and random_waypoints. You specify the type of trajectory and trajectory parameters in the roslaunch file. For a complete example see test.launch. For information about each parameter read the descriptions below.

Notice that in test.launch that the waypoints used in the trajectories are relative, i.e., when spawning the mover in Gazebo, you may specify a non-zero starting location:

<!-- Spawn in Gazebo -->
<include file="$(find moving_targets)/launch/spawn_mover.launch">
    <arg name="name"    value="$(arg mover_name)" />
    <arg name="model"   value="$(find moving_targets)/models/moving_person_walking/model.sdf" />
    <arg name="x"       value="1"/>
    <arg name="y"       value="0"/>
    <arg name="z"       value="0"/>
    <arg name="yaw"     value="0"/>
</include>

The waypoints param used for defining the trajectory will be relative to this starting point.

Parameters

Name	Description	Type
trajectory_type	Specifies the type of trajectory goToPoint : 0 waypoints: 1 circle: 2 ellipse : 3	int
acceleration	horizontal acceleration m/s/s	float
v	horizontal velocity m/s	float
move_target	indicates if the agent should be moving or not.	bool
waypoints_x	x-coordinate waypoints relative to starting position. First element must be 0.	float array
waypoints_y	x-coordinate waypoints relative to starting position. First element must be 0.	float array
waypoints_z	x-coordinate waypoints relative to starting position. First element must be 0.	float array
lambda	The direction for circular orbit. The possible values are -1 (counter-clockwise) and 1 (clockwise).	int
radius	The radius of the orbit.	float
half_plane	Uses the more sophisticated half-plane path manager (Algorithm 5, p191, UAVBook) (default: false)	bool
collisions	Turn off collisions for the agent so it can't run into things and be knocked down (default: true)	bool

goToPoint

Moves the agent from the initial position to the desired position. Once reached, it will stop moving.

Example setup

<group ns="targets/$(arg mover_name)">
    <param name="trajectory_type" type="int" value="0" />
    <param name="v" type="double" value="1" />
    <param name="move_target" type="bool" value="true"/>
    <rosparam param="waypoints_x">[0, 5]</rosparam>
    <rosparam param="waypoints_y">[0, 0]</rosparam>
    <rosparam param="waypoints_z">[0, 0]</rosparam>
</group>

Waypoints

Moves the agent to the waypoints. Once at the final waypoint, it will loop through them again.

Example setup

<group ns="targets/$(arg mover_name)">
    <param name="trajectory_type" type="int" value="1" />
    <param name="v" type="double" value="2" />
    <param name="move_target" type="bool" value="true"/>
    <rosparam param="waypoints_x">[0, 5, 5, 0, 0]</rosparam>
    <rosparam param="waypoints_y">[0, 0, 5, 5, 0]</rosparam>
    <rosparam param="waypoints_z">[0, 0, 0, 0, 0]</rosparam>
</group>

Circle

Moves the agent in a circle. No waypoints needed.

Example setup

<group ns="targets/$(arg mover_name)">
    <param name="trajectory_type" type="int" value="2" />
    <param name="radius" type="double" value="3" />
    <param name="lambda" type="double" value = "-1"/>
    <param name="v" type="double" value="2" />
    <param name="move_target" type="bool" value="true"/>
</group>

Elipse

Moves the agent in an elipse. Use only two waypoints.

<group ns="targets/$(arg mover_name)">
    <param name="trajectory_type" type="int" value="3" />
    <param name="v" type="double" value="1" />
    <param name="move_target" type="bool" value="true"/>
    <rosparam param="waypoints_x">[0, 5]</rosparam>
    <rosparam param="waypoints_y">[0, 0]</rosparam>
    <rosparam param="waypoints_z">[0, 0]</rosparam>
</group>

Constrained Random Waypoints

Moves the agent with randomly sampled waypoints within a bounding box specified by two waypoints. The first waypoint is the bottom-left of the box while the second waypoint is the top-right. Each random waypoint is generated by sampling an (x,y) from two independent uniform distributions parameterized by the min and max as dictated by the bounding box. Note that even the starting position of the mover is randomized within this bounding box---when spawning the mover as described in test.launch, the origin listed for the mover becomes the origin of the bounding box.

<group ns="targets/$(arg mover_name)">
    <param name="trajectory_type" type="int" value="4" />
    <param name="v" type="double" value="1" />
    <param name="move_target" type="bool" value="true"/>
    <rosparam param="waypoints_x">[0, 5]</rosparam>
    <rosparam param="waypoints_y">[0, 0]</rosparam>
    <rosparam param="waypoints_z">[0, 0]</rosparam>
    <param name="half_plane" type="bool" value="true"/>
    <param name="collisions" type="bool" value="false"/>
    <rosparam param="waypoints_x">[-5, 5]</rosparam>
    <rosparam param="waypoints_y">[-5, 5]</rosparam>
    <rosparam param="waypoints_z">[0, 0]</rosparam>
</group>

Note: For best performance with random waypoints mover, use the half_plane path manager with no collisions (especially with lots of random movers!).

Use Plugin

The plugin has several parameters that will need to be set.

Name	Description	Type
kpPsi	Heading proportional gain for PD control	float
kpZ	Altitude proportional gain for PD control	float
kdPsid	Heading differential gain for PD control	float
kdZ	Altitude differential gain for PD control	float
maxVPsi	Maximum velocity about z axis	float
maxVZ	Maximum linear velocity parallel to z axis	float
k_orbit	Gain for orbital trajectory	float
k_path	Gain for linear trajectory	float
chi_infinity	Gain for linear trajectory	float
update_rate	The target update rate in Hz	float

Example setup

<plugin name="TargetMotion" filename="libTargetMotion.so">
  <kpPsi>2</kpPsi>
  <kpZ>2</kpZ>      
  <kdPsi>1</kdPsi>
  <kdZ>1</kdZ>
  <maxVPsi>1</maxVPsi>
  <maxVZ>1</maxVZ>
  <k_orbit>2</k_orbit>
  <k_path>3</k_path>
  <chi_infinity>0.7853975</chi_infinity>
  <update_rate>30</update_rate>
</plugin>

Exposed Services

The plugin advertises a ROS service that allows the user to reset the agent at any time, or to tell the agent to stop or move. The service is defined in srv/MovingTargets.srv.