Anatomie d’un robot

Généralement, qu’il soit fait par NASA, ACME ou Degrassi High School, un robot se compose:

1. D’un cerveau, qui contrôle les actions du robot

2. De circuits électriques, qui alimentent les composants en ayant besoin

3. De mécanismes, qui bougent le robot et lui permettent d’interagir avec le monde physique

4. D’un châssis, qui tient toutes les autres parties ensemble.

Circuits électriques

Pour comprendre comment le CrcDuino (cerveau du robot) fonctionne, regardons d’abord les composants électriques du circuit de puissance 12V et du circuit de contrôle 5V, qui sont les deux grandes parties du circuit électrique:

What does a robot brain do?

Robot sensors and remote controller: gathering information

Just like a human body with its senses, a robot needs to figure out what’s going on around it. It needs brain inputs: sensors and the remote controller.

Robot sensors

They measure something and feedbacks that measurement to the brain. They are part of the 5V control circuit.

There are 2 main sensor types:

But there are three ways for sensors to feedback its measurement to be brain:

*Motor encoders are a type of sensor that uses a set of 2 “flashing” digital electrical signal to measure the angular displacement of a motor shaft. Signals are sent so fast that they need to be read by a special type of brain input called “interrupt-capable digital input”.

Remote controller

It’s a way for a human to directly interact with the robot: It sends the state of its button (pressed or not pressed - a digital signal) and its joystick (an x-axis and y-axis position - an analog signal) to the brain over a wireless link provided by a CrcConnect module. Some robots are not externally controlled: they are called autonomous robots.

Robot program: deciding what to do

The robot program is a set of code lines that is executed by the brain. These lines of code are written into a .ino file using a computer software called Arduino IDE, and then uploaded into the robot brain from the computer. Once powered up, the brain executes these lines sequentially and repeatedly ad vitam aeternam.

The robot brain is called a CrcDuino: it is a custom Arduino board designed by Crc Robotics that is very similar to the standard Arduino Mega2560 board. Arduino is a very popular ecosystem of electronics board meant for rapid prototyping.

The lines of code must respect a certain syntax to be understood by the brain. The syntax used is called the C/C++ programming language. The robot program uses functions to perform tasks. There are three types of functions that can be used:

• CrcLib functions, written by CRC Robotics especially for the CrcDuino and detailed in this wiki

• Native Arduino functions (also called Arduino programming language), written by the Arduino collective.

• Custom functions, written by yourself in the .ino file, if needed

Robot motors and servos: executing the decisions

Just like a human body with its muscles, a robot needs to interact with its surroundings. It needs brain outputs: 12V motors, 5V servos and other actuators. An actuator is a device that moves a mechanism.

12V motors

They are made of a fast rotating electrical motor coupled with a gearbox. Since they run on 12V power current coming from the main battery, but the robot brain only delivers 5V control signals, they need a motor controller to be able to run.

A motor controller is a “PWM device” and requires two wires to be connected to the robot brain: a PWM signal wire and a GND wire.

5V servos

Servos are small rotating actuators that are divided in two categories:

• Standard type servos: Their rotation is bounded to a minimum and a maximum angle (usually 0° to 180°), and the signal sends to them represents the angle were we want it to position itself.

• Continuous type servos: Their rotation is not bounded. Instead of an angular position, the signal sent to them represents the desired rotation speed and direction.

Both servo types are “PWM devices” and requires three wires to be connected to the robot brain: a PWM signal wire, a 5V supply wire and a GND wire.

Other actuators

Other actuators can be used on a robot like electromagnets, LEDs, lights, buzzers, etc. These are ON-OFF actuators, meaning that they are activated when a 5V voltage supply is fed to them, and not activated when no voltage is given to them.

These other actuators are “ON-OFF devices” and require two wires to be connected to the robot brain: a SIG wire providing either 5V or 0V and a GND wire

In a nutshell…