play_motion2
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A tool to play and handle pre-recorded motions in ROS2
PlayMotion2
This repository consists of play_motion2
, a tool to play and handle pre-recorded motions in ROS 2,
and its associated messages in play_motion2_msgs
.
PlayMotion2 allows executing simultaneous trajectories in multiple groups of joints.
Prerequisites
The motions yaml file should follow the following format:
/play_motion2:
ros__parameters:
motions:
motion_1:
joints: [joint1, joint2]
positions: [0.0, 0.0,
0.5, 0.25]
times_from_start: [0.5, 1.0]
meta:
name: Motion_1
usage: example
description: 'Example Motion'
motion_2:
...
motion_3:
...
The field positions
of the motion_1
there contains two rows and two columns:
- Each column corresponds to one joint, so the first column is for
joint1
and the second one forjoint2
- Each row is one position to reach. Then,
motion_1
consists of 2 trajectories for the specified joints:- Trajectory 1: both
joint1
andjoint2
move from their starting position until reach their respective point0.0
. - Trajectory 2:
joint1
goes from0.0
to0.5
andjoint2
moves from0.0
to0.25
.
- Trajectory 1: both
The field times_from_start
specifies the time to reach each position from the starting time
In case of motion_1
the joints will move to the first position in 0.5s, and to the second position in 0.5s.
However, since the starting position of the joint could be further than expected, an approach time to the first position is calculated for safety reasons. Then, if the calculated approach time for motion_1
is lower than 0.5
, the first trajectory will last 0.5s, but if it's higher, it will take the approach time calculated.
You can also configure the motion planner as follows:
/play_motion2:
ros__parameters:
motion_planner:
disable_motion_planning: false
planning_groups: # Sorted by order of preference
- planning_group_1
- planning_group_2
exclude_from_planning_joints:
- joint_1
- joint_2
- joint_3
joint_tolerance: 0.01
# Non-planning parameters
approach_velocity: 0.5
approach_min_duration: 0.5
The approach_velocity
and approach_min_duration
parameters are used for non-planned approaches.
-
approach_velocity
: Maximum velocity for the approach. The default value is0.5
. -
approach_min_duration
: Minimum duration for the approach. The default value is0.5
.
The parameter disable_motion_planning
is used to decide whether to use planning or not. The default value is false
, so the planning is enabled for the approach.
The rest of the parameters are used when planning is enabled:
-
planning_groups
: defines the MoveIt 2 groups to plan the approach of the motions. This parameter is mandatory when using planning. -
exclude_from_planning_joints
: List of joints that are excluded for planning. -
joint_tolerance
: Joint tolerance set when planning the approach. The default value is0.01
.
When using planning, the approach to the first position will be planned using MoveIt 2. Then, the planned trajectory is combined with the original motion in order to safely reach the first position of the motion and perform it.
Disclaimer: It is strongly recommended to use planning, otherwise there might be collisions when reaching the first position of the motion.
Usage
In order to use PlayMotion2, it has to be started with the following command
ros2 launch play_motion2 play_motion2.launch.py motions_file:=PATH_TO_MOTIONS_YAML motion_planner_config:=PATH_TO_MOTION_PLANNER_CONFIG [use_sim_time:=true]
Launcher parameters:
-
motions_file
: Path to motions file. This parameter is mandatory. -
motion_planner_config
: Path to motion planner configuration. This parameter is mandatory. -
use_sim_time
:true
orfalse
. Decide whether to use simulation time or not.
Once started, motion goals can be sent from another terminal:
ros2 action send_goal /play_motion2 play_motion2_msgs/action/PlayMotion2 "{motion_name: motion_1, skip_planning: false}"
Take in account that the goals will be planned or not depending on the following combinations:
disable_motion_planning |
skip_planning |
Result |
---|---|---|
false |
false |
Using planning |
false |
true |
Not planned |
true |
false |
Goal rejected |
true |
true |
Not planned |
PlayMotion2 also includes two services:
- To list the available motions
ros2 service call /play_motion2/list_motions play_motion2_msgs/srv/ListMotions
- To check if a motion is ready to be executed or not
ros2 service call /play_motion2/is_motion_ready play_motion2_msgs/srv/IsMotionReady "motion_key: motion_1"