Robot operation

Running the robot

1. Plug in your 2S Lipo battery.

   • If you followed the instructions above, the code will automatically start running on boot.

   • If you want to turn this feature off, ssh into the robot, go into rw mode, and then do:

     sudo systemctl disable robot
     

2. Connect the PS4 controller to the Pi by putting it pairing mode.

   • To put it into pairing mode, hold the share button and circular Playstation button at the same time until it starts making quick double flashes.
   • If it starts making slow single flashes, hold the Playstation button down until it stops blinking and try again.

3. Wait until the controller binds to the robot, at which point the controller should turn a dim green (or whatever color you chose in pupper/HardwareConfig.py for the deactivated color).

4. Press L1 on the controller to “activate” the robot. The controller should turn bright green (or again, whatever you chose in HardwareConfig).

5. You’re good to go! Check out the controls section below for operating instructions.

Robot controls

• L1: Press to toggle active mode and deactivate mode.

  • Note: the PS4 controller’s front light will change colors to indicate if the robot is deactivated or activated.

• R1: Press to transition between Rest mode and Trot mode

• Left joystick

  • Forward/back: moves the robot forward/backwards when in Trot mode
  • Left/right: moves the robot left/right when in Trot mode

• Right joystick

  • Forward/back: pitches the robot forward and backward
  • Left/right: turns the robot left and right

• D-Pad

  • Forward/back: raises and lowers the body
  • Left/rights: rolls the body left/right

• “X” button: Press it three times to complete a full hop

Important Notes

• PS4 controller pairing instructions (repeat of instructions above)

  • To put it into pairing mode, hold the share button and circular Playstation button at the same time until it starts making quick double flashes.
  • If it starts making slow single flashes, hold the Playstation button down until it stops blinking and try again.

• Battery voltage

  • If you power the robot with anything higher than 8.4V (aka >2S) you’ll almost certainly fry all your expensive servos!
  • Also note that you should attach a lipo battery alarm to your battery when running the robot so that you are know when the battery is depleted. Discharging your battery too much runs the risk of starting a fire, especially if you try to charge it again after it’s been completely discharged. A good rule-of-thumb for know when a lipo is discharged is checking whether the individual cell voltages are below 3.6V.
  • The robot will walk much more poorly when the battery is mostly discharged since a lower voltage is going to the motors.

• Feet!

  • Using the bare carbon fiber as feet works well for grippy surfaces, including carpet. If you want to use the robot on a more slippery surface, we recommend buying rubber grommets (McMaster #90131A101) and fastening them to the pre-drilled holes in the feet.

Tuning

• You can play around with different walking parameters by changing the config file StanfordQuadruped/pupper/Config.py

  • self.max_x_velocity [m/s]: The maximum forward/back trotting velocity
  • self.max_y_velocity [m/s]: Max left/right trotting velocity
  • self.max_yaw_rate [rad/s]: Max turning velocity
  • self.z_clearance [m]: How how the robot tries to lift each leg off the ground during swing. It’s called z_clearance because it’s the maximum distance in the z-axis between the foot and ground during swing. You can increase this value to make the robot step higher.
  • self.overlap_time [s]: Amount of time per step that the robot has all of its legs on the ground. Increase this value for more stable walking.
  • self.swing_time [s]: Amount of time the robot has each foot in the air for.