Building an Autonomous Vehicle: The Batmobile

Contributors: Nate

Problems

As with any project, we had a large number of problems and hurdles to overcome along the way. Here are a few that really hurt.

** EMI and GPS **

The Laser tape measures caused significant interference with GPS reception. We eventually moved the GPS module to the rear of the car, which improved positional accuracy. However, the motor caused interference with the compass.

** DC Motor EMF **

DC motors produce a ton of electromagnetic noise. We originally had the 48V battery powering the entire car. However, when the motor would kick on, it would cause enough ripple to make the Brain glitch and reset. We tried powering the I²C bus separately, but, because the Locomotion Controller needed to be attached to the motor controller, a GND connection had to be shared. The noise eventually found its way over the I²C bus. In the future we will optically isolate the I²C bus.

** Lack of EEPROM **

Because the SAMD21 doesn’t have internal EEPROM, we were unable to store GPS waypoints on the board. We fixed this by using an I²C-based EEPROM.

** Switching Steering Between Driver/Driverless **

It was difficult to attach and detach the linear actuator from the rack and pinion steering. Once the actuator was attached to the steering, a driver could not actively steer (for example, to the starting line). This could be fixed with a different actuator that could be back-driven, or we could go full monty and detach the steering column from the steering and have it control a trimpot that, in turn, controls the linear actuator (drive by wire).