Robot Operation

Calibration Procedure

Robot calibration saves the zero position of each encoder relative to a known physical pose, and is necessary any time that any encoder has moved relative to the physical robot. This should only happen after replacing or reassembling parts of the robot, and so the calibration procedure should not be performed unless you are instructed to do so by Agility support personnel. The procedure makes use of the calibration jig and hardware that the robot was shipped with.

1. Remove the shin protective shells as described here.
2. Remove the battery and replace the front shell
3. Set the calibration jig on a flat surface and place the robot on the jig such that the bottom of the pelvis fits into the vertical stand as shown below
4. Using the four M6x18 flat head screws provided with the robot, fasten the pelvis to the stand via the holes indicated in the picture below. Note: it can be tricky to get the pelvis mounting holes aligned with the calibration jig holes. Also, if the mating surfaces are not flush, the screws can bind, so take care with alignment

5. To access the rest of the mounting screws, carefully tilt the jig forward until robot is resting on its front cover. You may want to place something soft for the shell to rest on to prevent marring of the cover
6. The flat part of the knee joint is bolted down to the surface of the jig using the four M8x25 flat head screws provided. In the final configuration, the thigh segment will be oriented vertically, with the legs folded up behind the robot. The easiest way to move the legs into this configuration is to move the toe down against its hard stop, fold the leg up as far as it will go, and tilt the thigh forward and outward until it is vertical relative to the pelvis, but abducted away from the pelvis body and off of the stand. This configuration is shown below. From this position it is easy to rotate the thigh towards the pelvis into the correct position.

7. Line up the threaded holes on the knee with the through holes on the bottom of the calibration jig and start threading in the screws (do not tighten them yet)

8. Align the legs so that they are parallel to each other and to the calibration jig. It is easiest to compare the straight lines on the calibration jig (illustrated below) to ensure that the legs are parallel.

9. When the legs are parallel, tighten the screws from the bottom of the jig.
10. Move the toes downward all the way against the hard-stop. Since the toes will extend below the bottom of the calibration jig in this position, prop the back of the jig up on a small object. Do not prop it too high, as subjecting the leg compressing DOF to gravity will compress the springs and cause an offset in calibration. In the final configuration, the robot should look like the pictures below

11. Replace the battery, plug in a USB drive with the calibration model loaded (this was provided with the software package), and turn on the robot
12. Calibration should take less than a minute. To check progress, you can connect to the robot via Simulink Real Time Explorer (instructions here). If Cassie is set up as a target PC in slrtexplr, you can type the following from the Matlab command window to view the screen:

tg = slrt;
tg.viewTargetScreen;

When calibration is complete, there will be a message on the screen indicating calibration was successful. If you do not see the message after a minute, make sure the model you are using is correct. If you still have issues, seek assistance from Agility support.

If you are using the calibration software released June 2018, you can check the calibration status with the radio. From the Cassie telemetry screen, press the PAGE button once. When calibration is successfully completed, the upper right signal will change to 1.

Startup Procedure

1. Clip in the battery to the front of the robot. Make sure both switches are in the off position before connecting the power and data lines.
2. Replace the front shell
3. Insert the USB stick with desired control code into the slot for the development computer. The USB slots correspond to the stack order in the pelvis. For Gen. 1 Cassies (Fall 2017), the development computer is closer to the middle of the pelvis and the user computer is farther in the backward direction. For Gen. 2 Cassies (Spring 2018), this order is reversed.
4. If you are iterating on code through the host-target interface or transferring data, make sure the host computer is connected the the robot via the Ethernet jack on the top of the robot.
5. Turn on logic power (the small switch)
6. Turn on the remote control and long-press the PAGE button to get to the Cassie telemetry screen. If the robot logic power is on, you should see text saying "Cassie Connected, waiting for data"
7. Wait for the computers to boot. When the development computer boots, the telemetry screen will change to display the Agility logo, state of charge, and error messages.
8. Perform the homing procedure (outlined below)
9. Check that everything looks good: e.g. there are no errors, the robot is in a good starting position, and the STO is on.
10. Turn on motor power (large switch).
11. Enable the robot by toggling the STO switch.
12. The motor torques will ramp up over 8 seconds. Use this time to make sure the robot is doing what you expect it to. If anything looks strange, toggle STO and debug.

Homing Procedure

Video demonstration coming soon