sturo

An attempt to automate the RC-Car Traxxas Summit using a Raspberry Pi.

Overview

Sturo provides a framework allowing to automatically drive a RC-Car, specifically the Traxxas Summit (but trying to be configurable so it can be used with other models, too). It uses the Adafruit PWM-driver to control the servos and a Raspberry Pi to execute the code.

Helpful / Technical Documentation

by Pascal Ernst, FH Ostfalia Suderburg; pascal.cc.ernst@gmail.com, p.ernst@ostfalia.de

Used for modifications to the control system of the Traxxas Summit

Beginning from scratch

Where to start

A good place to start how the radio control works: http://www.rc-airplane-world.com/radio-control-gear.html

General terms

Tx / radio : Transmitter Rx : Receiver (for example Traxxas Link)

Servos

Servo-connectors have three wires:

Servos are controlled by PWM (Pulse width modulation). Two wires supply the Servo with a DC power supply and one (The "Signal" or S) controls the Servo with PWM.

The neutral position of a Servo normally is around 1.5 ms of the PWM. Higher or lower values change the position of the servo. Generally the minimum pulse will be about 1 ms wide and the maximum pulse will be 2 ms wide.

Traxxas Link servo-channels

Channel 5 - Rear locker (Summit), also supplies power to Led-lights front and back
Channel 4 - Front locker (Summit)
Channel 3 - Transmission control
Channel 2 - Esc-control; Forward / reverse-movement
Channel 1 - Steering servo(s)
Channel 1 - Same as above (parallel port; eliminates need for Y harness)

Connection with Raspberry Pi

The connection is made possible with connecting the Raspberry Pi to a PWM driver, preferably the Adafruit one. For more information on how to use the Chip with the Raspberry Pi, visit the Adafruit documentation. You will also need a power-converter to supply the Raspberry Pi with power, since the Raspberry Pi needs 5V, but the Batteries have 8,6V.

Useful Information for the Adafruit PWM Driver:

Maximum Current flowing through: 5 Amp (For comparison: The two big servos in charge for steering the Summit need roundabout 1.5A to work properly)
The esc build into the Summit (EVX-2) has built-in bec, so there is no need for an additional power-cycle to control the servos
esc and all servos are controlled by standard 50 Hz pwm. Be careful: some servos do not want / need the full range of pwm-control, especially the front-locker! TODO: Give some estimated ranges for the servos

Contact