ROS2-PiCAS

1. Implementation of Priority-Driven Chain-Aware scheduling

Setup

• ROS2-PiCAS is built on ros2-eloquent version.
• This repository includes the entire source code of ros2-eloquent with our priority-based scheduling.
• Before building source codes, required development tools and dependencies should be met (please see this link).
• Build source codes

  colcon build --symlink-install
  

How to use API

• Please see the example code in ros2-picas-example > picas_example > src > example.cpp

• Create executor and callbacks, e.g., timer_callback, regular_callback, exec1

  auto timer_callback = std::make_shared<StartNode>("callback_name", "pub_topic_name", trace_callbacks, exe_time(msec), period(msec), false);
  auto regular_callback = std::make_shared<IntermediateNode>("callback_name", "sub_topic_name", "pub_topic_name", trace_callbacks, exe_time(msec), true);
  rclcpp::executors::SingleThreadedExecutor exec1;
  

  • sub_topic_name: the name of subscription topic
  • pub_topic_name: the name of publishing topic
  • exe_time: execution time of callback in msec
  • period: period of timer callback in msec
  • trace_callbacks: print time stamp as a txt file (see ros2-picas-example > trace_picas)

• Enable priority-based scheduling

  exec1.enable_callback_priority();
  

• Set executor's rt priority (SCHED_FIFO in linux) and CPU assignment

  exec1.set_executor_priority_cpu(90, 5); // (90: rt priority, 5: cpu #)
  

• Set priority of callback

  exec1.set_callback_priority(timer_callback->timer_, 10); // 10: callback's priority (the higher, more critical callback)
  

• Spin executor (use spin_rt for real-time priority in linux)

  std::thread spinThread1(&rclcpp::executors::SingleThreadedExecutor::spin_rt, &exec1);
  

Run example

• Use sudo authority when running ros2 package to leverage rt priority in linux system.
  • Modify /etc/security/limits.conf as below then reboot the system

  <userid>  hard    rtprio  99
  <userid>  soft    rtprio  99

• Run example

  ros2 run picas_example example

2. Analysis framework

Case study example

• ros2-picas-example > picas-analysis > picas_casestudy.m

Schedulability test

• ros2-picas-example > picas-analysis > picas_schedulability_test.m

NOTE: Please reference our ROS2-PiCAS paper that was published in RTAS 2021.

@inproceedings{choi2021picas,
  title={PiCAS: New Design of Priority-Driven Chain-Aware Scheduling for ROS2},
  author={Choi, Hyunjong and Xiang, Yecheng and Kim, Hyoseung},
  booktitle={2021 IEEE 27th Real-Time and Embedded Technology and Applications Symposium (RTAS)},
  pages={251--263},
  year={2021},
  organization={IEEE}
}