Note: This tutorial assumes you already know how to run the dashboard.
(!) Please ask about problems and questions regarding this tutorial on Don't forget to include in your question the link to this page, the versions of your OS & ROS, and also add appropriate tags.

Power system

Description: This tutorial teaches you about the PR2 power system

Tutorial Level: BEGINNER

Next Tutorial: Using the PR2 run stops


  1. Power system

Power system

The PR2 power system is divided in three parts:

  • Left arm
  • Base
  • Right arm

Each of these parts has a button on the dashboard:

  • system?action=AttachFile&do=get&target=power.png


  • As a first exercise, press on the Left arm power button, and choose to put it in standby. That button should show up in yellow. When you touch both the left and right arm, you'll notice that the left arms are not controlled any more, even though only the left arm is in standby. This happens because the Motor Controller Boards (every motor has its own MCB) detected a problem with one of the motors, and shut down all motors into a 'safety lockout' mode.
  • Now enable the power to the left arm again (by clicking the Left arm power button and choosing Enable). Now feel the left and right arms. They are still not controlled, although the power is up again. This is because the MCBs are still in safety lockout.
  • Since you know why the power was lost, it is safe to tell the MCBs to start up again. The button in the image below allows you to reset the MCBs. The MCBs will detect that the power is back, and will resume normal operation.

  • system?action=AttachFile&do=get&target=motors.png

Power off

  • Now, let's go a step further. Instead of just putting the power in standby, let's completely disable the power this time. So click the left arm power button again, and choose disable.
  • Again, you'll see that the MCBs go into safety lockout, and the arms are not controlled any more. So, go back and enable the power again.
  • Now that the power is back up, tell the MCB's to reset. Now you'll see that the MCBs won't come up any more. Why? When you disable the power completely, the MCBs are completely shut down, and lose all their state. Before, when you put the power in standby, the MCBs still had enough power to keep running, there just wasn't enough power any more to run the motors. When you disable the power, the MCBs completely shut down.
  • To recover from this state, the only thing you can do is stop the robot and start it again. Before you start the robot, make sure the power is enabled or in standby, otherwise the software won't be able to communicate with the MCBs. Also, you'll need to restart the dashboard when you restart the robot.

Wiki: pr2_robot/Tutorials/Power system (last edited 2014-01-21 22:29:41 by gustavogoretkin)