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Getting started with the quad A1

Safety

The mjbots quad A1 is a high performance robot capable of very fast and powerful motions. It is not recommended for use in the vicinity of untrained personnel and especially not children or others who do not appreciate what it is capable of.

Minimize physical handling of the robot while the power switch is on, as malfunctions may cause legs to to move rapidly, creating pinch hazards.

Turn on

  1. Ensure the switch is in the "off" position. When off, the LED side of the switch is not depressed.

  2. Insert a 4Ah ONE+ battery. It may be necessary to apply a moderate tap with your fist in order to get both retaining clips to latch.

  3. Flip the quad A1 over to be right side up and extend legs to be maximally stretched out, flat against the ground. This is the "turn-on" position.

  • NOTE: The software is able to detect some but not all invalid turn-on positions.

  1. Activate the power switch. This means pressing the side with the LED down.

  2. After ~30s, the robot's wifi access point will become available. Connect to it.

  3. Using Chrome, the only currently supported browser, navigate to http://192.168.16.47:4778

Joystick

The web control application supports a connected gamepad, which is the simplest means of controlling the robot. The "Y/4" button on the gamepad enables mode select, while the d-pad up and down allow you to cycle between modes. Once you pick a mode that is not "Stop", the quad A1 will stand up.

While moving, the left analog stick controls translation, while the left and right motion of the right analog stick controls yaw.

When stopped, the left trigger can be pulled to enable "emote mode". In that mode, the analog sticks control the attitude of the body.

Keyboard

It is also possible to operate the robot with a mouse and keyboard. The mouse can be used to click and select a mode. WASDQE keys can be used to pilot the quad A1 as per the on-screen display.

Maintenance

Belt tension

The leg belts need to be kept appropriately tensioned to minimize the possibility of belt skipping, while not overly stressing the 3d printed upper leg structure. The M3 adjustment bolt in each leg can be used to adjust that tension. As the belts stretch with age, it will likely be necessary to use a longer bolt than the M3x12 initially installed. M3x14 is the longest suitable bolt.

Rezeroing leg

If the leg is disassembled or re-assembled, or the belt skips, then that leg will need to be re-zeroed. This can be accomplished as follows:

  1. Lay the quad A1 upside down on a flat surface.
  2. Install the leg zeroing fixtures on the leg in question. The lower leg qdd100 rests on the curved part of the large fixture, and the upper part restrains the upper leg.
  3. The smaller fixture registers the upper and lower leg together. Slide it down as far as possible, then attempt to get the lower leg as centered as possible in any remaining play.
  4. Connect to the robot and stop the existing software:
ssh -i mjmech/utils/ssh/mjbots.ssh [email protected]
sudo screen -r
<CTRL-c>
  1. Determine the leg number of the leg to be rezeroed. When looking from the top, the legs are numbered as follows. The "front" side is the one with the power switch. (note the robot is upside down now, so this will be mirrored):
   1      2

     FRONT

     BACK

   3      4
  1. Rezero the leg, using the leg number from above.
./zero_leg.py -l 1

This will report the current position of each three leg servos. Press when the leg is in position to zero that leg.

  1. If more legs need to be rezeroed, the fixture can be moved between legs and the step 6 command run more as necessary.

  2. Shutdown the computer, wait 15s, then turn off the power switch.

shutdown -h now
  1. At this point the quad A1 can be set in the "turn-on" position and started up as normal.

Change ssh key

The quad A1 is initially provisioned with an ssh key that is common to all machines. This is not normally a problem, as the SSID is unique and the password is secret. If you wish to expose the quad A1 to a wider network, first contact [email protected] to discuss your risk profile. Second, you may wish to change the default ssh access key.

First, use ssh-copy-id to install a new key on the quad A1:

ssh-copy-id -o "-i utils/ssh/default.ssh" [email protected]

Then, ssh in, and remove the old key.

ssh [email protected]
vi .ssh/authorized_keys  # remove the [email protected] line

Upgrading software

  1. Compile:
tools/bazel build --config pi -c opt //mech:quad_deploy.tar
  1. Copy it to the robot:
rsync -Pv -e "ssh -i utils/ssh/default.ssh"  \
  bazel-out/armeabihf-opt/bin/mech/quad_deploy.tar [email protected]:
  1. Perform the upgrade and restart the software.

NOTE: If any configurations have been modified, you will want to manually capture those now, as this process will reset all configuration to factory default.

ssh -i utils/ssh/default.ssh [email protected]
sudo screen -r
<CTRL-c>
cd /home/pi
sudo -u pi tar xvf quad_deploy.tar
sync
cd mech
./start-robot.sh
<CTRL-a d>