Safety first¶
The GOAT Racer is a real robot car. It can move fast. Read this page before you power it on.
Three rules cover almost everything
- Read the Traxxas safety sheet in the box. It covers the chassis, the motor, the charger, and the battery pack. Everything below adds to it. Nothing replaces it.
- Do not over-charge or over-discharge the pack. Charge with the balance charger on its LiPo setting. Stop at the cell limit. Stop driving when the low-battery warning sounds.
- Unplug the battery when you store the car for longer than 24 hours. The low-voltage cutoff saves the pack during a run, not on the shelf.
The RF kill switch¶
The kill switch is your hand brake. It is a radio remote, independent of Wi-Fi and of all the software. It works when everything else is stuck.
| Button | Action | Sound |
|---|---|---|
| A | Arms the car. | Rising pair of beeps. |
| B | Brakes the car. | Falling pair of beeps. |
The receiver sits on the motor controller. Disarm cuts the motor at the controller, below any software. The Jetson cannot override it. The robot software only reports ready with the switch armed.
Keep the remote in your hand whenever the car can move. B is the answer to everything unexpected.
Battery¶
The car runs on a 2S LiPo pack. The motor controller watches it.
| Level | What happens |
|---|---|
| Warning, at or below 6.8 V | Three mid beeps when stopped. Three long high chirps while driving, repeating. Finish the run and charge. |
| Cutoff, at or below 6.6 V | Drive cuts on the spot. The car beeps low-high-low every 5 seconds until power-off. Steering still works. Drive does not. Power-cycle the car to clear the latch. |
Both are automatic and battery-driven. The kill switch is separate and manual.
On the bench, for long stints, power the Jetson from its own adapter. Unplug the barrel jack from the battery harness and plug the adapter in. The motor controller has its own switch. Leave it off unless you need the motor.
Arming and control modes¶
The car boots in teleop mode. The gamepad has a deadman button. Nothing moves unless you hold it. Release the deadman, or lose the link, and the car coasts with centered steering.
One process controls the motor at a time.
| Mode | Who drives |
|---|---|
| Teleop | The gamepad. |
| Policy | The trained policy. |
| None | Nobody. Losing the producer commands coast, never the last value. |
Select a mode on the dashboard. The car stops the active producer before it starts another one. Stopping the policy does not start teleop.
Motor modes and people¶
The gamepad picks how the motor holds a command: current, speed (eRPM), or duty. eRPM and duty modes do not care what is in the way. A blocked wheel in eRPM mode pulls current to the limit and can damage the motor or the controller. Use current mode when you are close to the car or to people. See Teleop controls.
Where to drive¶
- Keep a clear floor. Remove cables, bags, and feet.
- Stay within 10 feet of the car. Past that the gamepad link drops and the car coasts.
- Never leave a powered car unattended with the battery plugged in.
TODO (Rob): add the recommended track surface and the minimum clear area for a first lap.