Build instructions

This pendulum control demo is available in the default ROS 2 install. Follow the instructions to build ROS 2 from source: https://docs.ros.org/en/rolling/Installation/Linux-Development-Setup.html

Running the demo

. install/setup.bash
. install/pendulum_control/bin/pendulum_demo

A few command line arguments related to real-time performance profiling are provided by rttest. See https://github.com/ros2/rttest/blob/master/README.md for more information.

Running with real-time performance

The demo will print out its performance statistics continuously and at the end of the program.

Example final output:

rttest statistics:
  - Minor pagefaults: 0
  - Major pagefaults: 0
  Latency (time after deadline was missed):
    - Min: 2414 ns
    - Max: 45949 ns
    - Mean: 8712.12 ns
    - Standard deviation: 1438.74

Ideally you want to see 0 minor or major pagefaults and an average latency of less than 30,000 nanosceonds (3% of the 1 millisecond update period).

If you see pagefaults, you may not have permission to lock memory via mlockall. You need to adjust the system limits for memory locking.

Add to /etc/security/limits.conf:

<user>    -   memlock   <limit in kB>

A limit of -1 is unlimited. If you choose this, you may need to accompany it with ulimit -l unlimited after editing the file.

After saving the file, log out and log back in.

If you see a high mean latency in the results, you may need to adjust the maximum priority for processes.

Add to /etc/security/limits.conf:

<user>    -   rtprio   <maximum priority>

The range of the priority is 0-99. However, do NOT set the limit to 99 because then your processes could interfere with important system processes that run at the top priority (e.g. watchdog). This demo will attempt to run the control loop at priority 98.

With these settings you can get decent average performance even if you don’t have the RT_PREEMPT kernel installed, but you will likely see an unacceptably large maximum latency and periodic latency spikes.

Dynamic allocation

The demo will also print to the console whenever malloc is called, along with debug symbols from the backtrace for that stack.

If you search the output of the demo, you will see that malloc is only called during the initialization phase of the program.

This is consistent with the requirements of real-time programming (to prevent non-determinstic blocking in the allocator).

However, without memory locking, you may still see some pagefaults due to reading memory that was allocated but not read into cache.

Changelog for package pendulum_control

0.35.0 (2024-10-03)

0.34.2 (2024-07-29)

0.34.1 (2024-06-17)

0.34.0 (2024-04-26)

0.33.2 (2024-03-28)

• Update maintainer list in package.xml files (#665)
• Contributors: Michael Jeronimo

0.33.1 (2024-02-07)

0.33.0 (2024-01-24)

0.32.1 (2023-12-26)

0.32.0 (2023-11-06)

0.31.1 (2023-09-07)

0.31.0 (2023-08-21)

0.30.1 (2023-07-11)

0.30.0 (2023-06-12)

0.29.0 (2023-06-07)

• [pendulum_control Install targets to project lib (#624)
• Contributors: Yadu

0.28.1 (2023-05-11)

0.28.0 (2023-04-27)

0.27.0 (2023-04-13)

0.26.0 (2023-04-11)

0.25.0 (2023-03-01)

0.24.1 (2023-02-24)

0.24.0 (2023-02-14)

• Update the demos to C++17. (#594)
• [rolling] Update maintainers - 2022-11-07 (#589)
• Contributors: Audrow Nash, Chris Lalancette

0.23.0 (2022-11-02)

0.22.0 (2022-09-13)

0.21.0 (2022-04-29)

0.20.1 (2022-04-08)

0.20.0 (2022-03-01)

0.19.0 (2022-01-14)

• Fix include order and relative paths for cpplint (#551)
• Contributors: Jacob Perron

0.18.0 (2021-12-17)

• Remove the malloc_hook from the pendulum_demo. (#544)
• Update maintainers to Audrow Nash and Michael Jeronimo (#543)
• Additional fixes for documentation in demos. (#538)
• Fix documentation for pendulum_control. (#537)
• Contributors: Audrow Nash, Chris Lalancette

0.17.0 (2021-10-18)

0.16.0 (2021-08-11)

0.15.0 (2021-05-14)

0.14.2 (2021-04-26)

0.14.1 (2021-04-19)

0.14.0 (2021-04-06)

0.13.0 (2021-03-25)

• Replace rmw_connext_cpp with rmw_connextdds (#489)
• Contributors: Andrea Sorbini

0.12.1 (2021-03-18)

0.12.0 (2021-01-25)

• Remove ineffective log output (#450) (#477)
• Contributors: y-okumura-isp

0.11.0 (2020-12-10)

• Update the package.xml files with the latest Open Robotics maintainers (#466)
• Contributors: Michael Jeronimo

0.10.1 (2020-09-21)

• Remove deprecated warning (#459)
• Contributors: Anas Abou Allaban

0.10.0 (2020-06-17)

• Follow API/file name changes (ros2/realtime_support#94) (#451)
• Contributors: y-okumura-isp

0.9.3 (2020-06-01)

0.9.2 (2020-05-26)

0.9.1 (2020-05-12)

0.9.0 (2020-04-30)

• avoid new deprecations (#442)
• fix CMake warning about using uninitialized variables (#439)
• Fix pendulum_control tests to use stdout stream. (#430)
• code style only: wrap after open parenthesis if not in one line (#429)
• Contributors: Chris Lalancette, Dirk Thomas, William Woodall

0.8.4 (2019-11-19)

0.8.3 (2019-11-11)

0.8.2 (2019-11-08)

0.8.1 (2019-10-23)

• Replace ready_fn with ReadyToTest action (#404)
• Contributors: Peter Baughman

0.8.0 (2019-09-26)

• Fixes to pendulum_control demo (#385)

  • Add asserts to ensure that the latency is never negative
  • Switch last_sample to int64_t to match new rttest interface
  • Allow any number of spaces
  • Make sure to expect the extra newline for the pendulum_demo
  • Only publish statistics if they are available.
  • Remove some unused functions from rtt_executor.hpp

• Fix armhf build warnings (#372)
• Contributors: Chris Lalancette, Prajakta Gokhale

0.7.6 (2019-05-30)

0.7.5 (2019-05-29)

0.7.4 (2019-05-20)

0.7.3 (2019-05-10)

0.7.2 (2019-05-08)

• changes to avoid deprecated API's (#332)
• Corrected publish calls with shared_ptr signature (#327)
• Migrate launch tests to new launch_testing features & API (#318)
• Contributors: Michel Hidalgo, William Woodall, ivanpauno

0.7.1 (2019-04-26)

0.7.0 (2019-04-14)

• Removed unused lambda capture. (#315)
• Added launch along with launch_testing as test dependencies. (#313)
• Dropped legacy launch API usage. (#311)
• Contributors: Emerson Knapp, Michel Hidalgo

0.6.2 (2019-01-15)

0.6.1 (2018-12-13)

0.6.0 (2018-12-07)

• Updated package maintainer. (#286)
• Updated to match rmw_fastrtps_dynamic_cpp (#271)
• Fixed spacing to comply with uncrusity 0.67 (#267)
• Fixed no return code for main() in several files (#266)
• Contributors: Dirk Thomas, Michael Carroll, Mikael Arguedas, testkit

0.5.1 (2018-06-28)

• make Mikael Arguedas the maintainer (#263)
• Contributors: Mikael Arguedas

0.5.0 (2018-06-27)

• Updated launch files to account for the "old launch" getting renamespaced as launch -> launch.legacy. (#239)
• Fixed the pendulum's inertia in the physic model. (#220)
• Contributors: Dirk Thomas, Thomas de Candia, William Woodall, dhood