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Hi everybody.
I just controlled two motors using ROS, however it is not a real time process.
I am just wondering what is the best easy way to make a pthread that runs in real time, which control the motors and can easily send messages to other ROS nodes.
Any help will be appreciate it
If you create an RTT component, you can make a given input/output port use some ROS message type, and then use the tools in the rtt_ros_integration package to connect that port up to a ROS topic ( http://www.ros.org/wiki/rtt_ros_integration ). The default way to interact with an RTT component is through the OCL Deployer interface, and you can write interpreted scripts for this interface that specify how to connect RTT ports up to ROS topics. The line of script to connect an RTT port to a ROS topic looks something like this:
stream("YourComponentName.YourRTTPortName", ros.topic("/topic_name"))
http://www.orocos.org/wiki/orocos/ i recommend to read RTT wiki and toolchain and follow the examples in http://www.orocos.org/wiki/orocos/toolchain/getting-started/toolchain-tutorials (RTT 2.x Exercises). To get a good in site of rtt-components and real time processes
what is the C++ equivalent of the script line you passed to link a port to the topic?
For real time control tasks the most commonly used tool is Orocos. http://www.ros.org/wiki/orocos
If you really want to run a real-time thread in your application, skip pthread and just use boost::thread instead. You can find the docs here. It's simple, clean, and ROS uses it all over the place.
EDIT:
You can run as many threads in a process as you want, but there are only certain conditions under which these threads will run at full performance. boost::thread will use multiple cores by default, but if your threads do less work than scheduling the thread then you won't see any benefit from multithreading. Also, if you have more threads than cores, you won't see much performance increase.
Other than that, there's no reason that you can't run multiple threads in a single process.
Just an aside: ROS runs each node as a separate process to enable maximum operating system optimization (processes are typically handled and scheduled better than threads). You could look into splitting your real-time process into multiple nodes.
Asked: 2012-05-23 21:04:26 -0500
Seen: 4,210 times
Last updated: May 25 '12
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