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Ball Balancer Environment

Simulation and control environment for the Quanser 2DoF Ball Balancer (ball-on-plate).

Package contents

  1. model.pdf physical model description
  2. base.py common functionality
  3. ball_balancer.py simulated environment
  4. ball_balancer_rr.py real robot environment
  5. ctrl.py simple controllers
  6. examples example scripts

Controlling the real robot

To control the real robot, you must be in the same local network with the control PC of the Ball Balancer. By default, the control PC has the IP address 130.83.164.119 (you should double-check this). The IP address passed to the BallBalancer's constuctor must match the one of the control PC.

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

  1. Start the control server on the control PC

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

  2. Launch the client application on your machine

     python3 quanser_robots/qube/examples/<SCRIPT_NAME>.py

  3. At the end of the day, shut down the control server

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

Control loop

The canonical way of using the real robot environment:

import gym
from quanser_robots import GentlyTerminating
env = GentlyTerminating(gym.make('BallBalancerRR-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 If you forget to reset the environment and then send an action after some time of inactivity, you will get an outdated observation.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.