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Qube environment

Simulation and control environment for the Quanser Qube (Furuta Pendulum).

To see Qube in action, start the simulated swing-up demo

python3 quanser_robots/qube/examples/swing-up.py

Package contents

  1. model.pdf physical model description
  2. base.py common functionality
  3. qube.py simulated environment
  4. qube_rr.py real robot environment
  5. ctrl.py energy-based swing-up controller
  6. examples example scripts

Controlling the real robot

To control the real robot, you must be in the local network with the Qube control PC. There are two ways to get into the same network:

  1. Ethernet connection. Assume Qube control PC has the IP address 192.168.2.17 (see quanser_robots/qube/__init__.py); then your PC should have the IP e.g. 192.168.2.1 to be in the same network. Try ping 192.168.2.1 on the Windows PC to check the setup.

  2. Wireless connection. If your laptop doesn't have an Ethernet port, you can connect to the Windows PC via WiFi.

    • For that, connect the Windows PC to the Internet (you might need to modify Network adapter settings for IPv4, set everything to automatic there).
    • Go to Start -> Settings -> Network & Internet -> Mobile hotspot and turn on the mobile hotspot.
    • Connect to the WiFi network that you just created. Adjust the IP in quanser_robots/qube/__init__.py.

To run the swing-up demo on the real robot, perform the following steps:

  1. Start the control server on the control PC (pick frequency 100, 250, or 500)

     quarc_run -r Desktop\servers\qube\quarc_py_bridge_qube_100.rt-win64

  2. Launch the client on your computer (use matching freq e.g. 'QubeRR-100-v0')

     python3 quanser_robots/qube/examples/swing-up_rr.py

  3. When you are done with experiments, shut down the control server

    quarc_run -q Desktop\servers\qube\quarc_py_bridge_qube_100.rt-win64

Control loop

The canonical way of using the real robot environment:

import gym
from quanser_robots import GentlyTerminating
env = GentlyTerminating(gym.make('QubeRR-v0'))
ctrl = ...  # some function f: s -> a
obs = env.reset()
done = False
while not done:
    act = ctrl(obs)
    obs, rwd, done, info = env.step(act)

Pay attention to the following important points:

  • Reset the environment env.reset() right before running env.step(act) in a loop. If you forget to reset the environment and then send an action after some time of inactivity, you will get an outdated observation.

  • Wrap the environment in the GentlyTerminating wrapper to ensure that a zero command is sent to the robot after an episode is finished. Qube always keeps executing the last command it received, which may damage the motor if constant voltage is applied for too long.