maxb's profile - activity

Assuming the wifi is indeed the problem: Do you know any tricks to make the connection more reliable? Both in-ROS (maybe decrease number of topics/messages) and 'outside' of ROS?

I do have multiple callbacks in almost all nodes (7 nodes and up to 5 callbacks) but there are no sleep or other time consuming functions in the callbacks. The nodes are connected by ssh over Wifi so this might be the reason. I also found out that the machines are properly synchronized.

Hi there :)

I've got a little problem running ROS on two machines and I don't really know how to find out what could cause the problem: Setup: I'm running nodes on two machines at different but constant frequencies (e.g. IMU at 50 Hz, controller at 10 Hz, ...). Most of the time it works perfectly well but just sometimes it seems that all nodes stop running for short instants (see plot of IMU measurements here: https://postimg.org/image/g3p3n4xtz/ ). You can see in the plot that it's running well until about 10.5 seconds, then slower and then there's a pretty long break of no data being published/received. I'm suspecting two problems:

1. Wrong synchronization of the machines (I'm using chrony but I can't guarantee that everything is set up perfectly right)
2. Too high CPU workload which does not allow all nodes to be executed (which would be weird since it's running fine at other times)

Have you ever observed a similar problem or do you know what could cause it? And if not - which tools or methods would you suggest to find the problem?

Any help will be much appreciated, thank you very much in advance!

Best, Max

Thank you for your answer! I've spent some more time on going through Kalman theories and I think I understand it now. There are actually ways to combine different models (by weighting them differently) but they normally yield systems that are more difficult to understand.

Hi guys :)

I've got a very theoretical Kalman-filter-related question that and I hope that someone has an idea how to solve this: How is it possible to use 'different' state equations for the same states?

In detail: I have an RC-car and I can use a Kalman filter to fuse GPS and IMU data to an estimate of position, velocity and heading. However, the basic Kalman-equations do not account for the car dynamics! Instead, they only integrate IMU acceleration and find an optimal estimate together with orientation and GPS. Since I know the car's dynamics (e.g. it can only move longitudinally) I would like to use this information as well. Problem: I'm getting multiple equations for the same states.

It would be awesome if you have any ideas! I can't be the only one dealing with this issue but I can't find anything about it in literature. Please also let me know if my problem is not clear enough and I'll be glad to give some more information.

Thank you very much in advance for any help!

Hi,

I'm working on a robot that is remotely controlled by my computer (via a launch-script that defines different 'machines'). Messages are published and received by different nodes on different machines and the machines are connected by a local Wifi-network.

I am not sure if my available bandwidth is limiting the data transfer (or execution times) and since I don't need all messages on all topics I have the following question: Is it possible to define that only specific topics are published across multiple machines while keeping other topics only on one machine, "invisible" to others?

Thank you very much in advance!

Best, Max

Cool thank you, just what I was looking for!!

Hi

I'm running multiple nodes (started by one launch-file) and a few of them are logging data at the same time independently. In the end I'd like to evaluate these different log-files in another program (lets say MATLAB). The issue is the following: If I'm creating 3 different logfiles in 3 different nodes I don't want to enter 3 different filenames in MATLAB later. So here the question: Can I somehow find a value that is unique for every simulation (every start of the launch-file) and that every node has access to? I was thinking about constant values like the start time of the core and then put this value into each logfile-name, e.g.

log1-10-18-09-30-30.txt # created by node 1

log2-10-18-09-30-30.txt # created by node 2

log3-10-18-09-30-30.txt # created by node 3

with October 18th, 09:30:30 the start time of the core. It doesn't necessarily need to be the start time though, it just needs to be the same value for every node. (Nodes are written in Python and Julia).

Thank you for any advice or ideas!

Best, Max