adayoegi's profile - activity

Environment and package:

Ubuntu 16.04, ros-kinetic, stage_ros branch lunar-devel

Problem encountered:

When a node keeps publishing a static geometry_msgs/Twist until desired time is over. Stage is expected to update robot's /odom to desired pose but it does not.
When I publish the msg from terminal once, stage seems keep moving the robot for a period of time.

Problem example:

A while loop publishes geometry_msgs/Twist with 3.03rad/s on z rotation for 0.12s, after that a geometry_msgs/Twist with 0 is published, which should result in 3.03*0.12=0.36 rad = 20 deg.
Stage either:
1. Turns the robot to an angle < 20 deg (ex: 17 deg)
2. Not turning at all

Question:

1. When publishing 3.03 rad/s for 0.12s, why the /odom of robot in stage simulation is not exactly 0.36 rad?
2. What can I do to make it work?

More details:

What I have checked:
1. The while loop indeed keeps publishing till the desired time is finished.
2. Verified the topic is published with rostopic echo
3. The default interval_sim of stage is 100ms, changing it to 1ms does not help much. (the final pose is different but still having the same problems)
4. By setting interval_sim to 1s and publish a geometry_msgs/Twist from terminal (publish only once), it seems stage will keep executing the command until 1s is over (the robot turns 3.03rad/s * 1s = 3.03rad).
5. When 2 different commands are sent, stage only execute the last one.
6. I was expecting a higher publish and subscribe rate helps (ex: publish and subscribe at 1000Hz), but it turns out the robot is not turning at all.
7. By setting interval_sim to 1ms and publish a geometry_msgs/Twist from terminal (publish only once), the /odom is correct (3.03rad/s * 1ms = 0.003rad = 0.17 deg), but the robot on the UI turns a lot more.

My doubt:
The cause of the problem might be timing/clock issue, but I do not know how to validate it or solve the problem. Based on point 4 & 5, I guess stage receives command periodically, and executes this command until next clock time.
If there are more than 1 commands received in this interval, it only executes the last one.

Thank you.

Edit 2019.0214:

Some more findings to get the desired pose.

1. peteblackerthe3rd 's answer is one of the keys, close loop control would be more precise
2. Set interval_sim in you world file, this is by default 100 (ms). ref
3. Set update_interval in your position model, this is also by default 100 (ms). ref
4. Set base_watchdog_timeout in your launch file, this is by default 0.2 (s) ref. Setting this too low will have more chances to miss subscriptions.

I have not yet implement close loop control, if anyone knows a good library please recommend me.

Currently still 1 problem that sometimes stage does not respond to commands. I am not sure if it is ... (more)