Lego Mindstorms NXT

Lego Mindstorms NXT is a construction and robotics game presented by Lego in 2006. It succeeds the Lego Mindstorms RCX range . In 2010, Mindsorms NXT is in its version 2.0. He will be succeeded a few years later by Lego Mindstorms EV3 .

History

The range Mindstorms NXT is the generation of Lego Mindstorms , which was submitted on 4 January 2006 at the Consumer Electronics Show in Las Vegas in the United States . The main changes are the use of a CPU 32 bit of ARM-type and adding new sound sensors and ultrasonic. In addition, it is now possible to use Bluetooth technology to control the robot (with a mobile phone for example).

The Lego Mindstorms NXT robot is widely used for teaching and teaching science and technology. Numerous student competitions are based on the Lego robot such as the First Lego League or the French Cup of Robotics [ref. Required] . International competitions also exist on the basis of this robotic kit.

The Lego Mindstorms NXT kit evolved into EV3 in 2013.

Characteristic

General Features

The main features of the new Lego Mindstorms NXT range are:

  • NXT programmable intelligent brick 4 input ports and 3 output ports of shape close to the RJ12 standard (only the non-return tab is offset)
  • connections USB and Bluetooth
  • Three interactive servo motors
  • Several dozen sensor models (four sensors per box): ultrasound, sound, light, contact, color, infrared, gyroscopic, infrared, accelerometer, compass …
  • NXT-G, graphic programming software, very intuitive based on Labview compatible with Windows and Mac
  • Many additional accessories (not supplied in the main box) such as a USB Bluetooth key , a rechargeable battery , Wi-Fi, XBee communication means, multiplexers, solar panels, relay drivers, holonomic wheels. .

Technical characteristics of the intelligent brick NXT

  • Microprocessor 32 bit ARM7 from Atmel ,
  • Bluetooth function (connection to other NXT or PC and possibility to control the NXT with a mobile phone or other Bluetooth device),
  • A USB 2.0 port ( 12 Mbps ),
  • Four input ports for connection of the sensors 1, 2, 3 and 4,
  • Three output ports for motors A, B and C,
  • Liquid crystal display 100 × 64 pixels ,
  • Built-in speaker ( 8 kHz sound quality – 8 bit – 2-16 kHz sampling ),
  • Power: six AA batteries ( 1.5V ); A 9 V battery is marketed by Lego.
  • Dimensions: 112 × 72 × 40 mm

It is possible to connect 3 NXT smart bricks at the same time to another via Bluetooth, but communication can only be done with one at a time.

It is possible to connect the NXT with sensors and motors range RCX with adapter cables.

Characteristics of the sensors

Lego provides only 4 sensors: Contact sensor, sound sensor, ultrasonic sonar, light sensor or color sensor. Other existing sensors are created by third-party companies that rely on the open technical specifications of the Lego Mindstorms NXT robot. Lego promotes the emergence of an ecosystem around its product. Companies that provide sensors for Lego are:

  • Hitechnic
  • Mindsensors
  • Humarobotics
  • Dexter Industries
  • Codatex

Here is a description of the sensors available (not exhaustive):

  • Touch sensor: Reacts to a contact.
  • Photosensitive sensor: Measures the light intensity sensed.
  • Sound sensors: Measures the sound intensity in decibels.
  • Ultrasonic sensors : Detects obstacles and measures distances (sonar principle).
  • Compass: Allows you to know the position of the north in relation to the robot. This type of sensor is very useful in robotics because it provides a fixed marker.
  • Color sensor: Distinguishes different colors (6 with NXT-G, the software supplied by LEGO).
  • Accelerometer sensor: Measures variations in speed. It allows the robot to identify itself in space, to detect shocks and to recognize robot movements and accelerations.
  • Infrared infrared detector: Allows detection of infrared sources, strength and direction.
  • Gyroscopic sensor: Used to detect rotations.
  • Infrared Sensor: Communicates with other infrared devices.
  • Infrared Detector: Measures distances to obstacles (similar to ultrasonic sonar).
  • GPS: provides a measure of spatial position thanks to the GPS system
  • Temperature sensors: Sensors exist in rigid or flexible form, they make it possible to measure the temperature of the objects.
  • IMU: inertial unit
  • Bending sensor: tongue measuring its deformation. This type of sensor makes it possible, for example, to reproduce the mustaches or vibrisses of certain animals such as rats or cats.
  • RFID Sensor : Detects RFID transponders
  • PIR sensor: This passive infrared sensor is analogous to the sensors found in motion detectors of home alarm systems.
  • Barometric sensor: measures the atmospheric pressure which is useful to create a weather station or to measure the altitude of the place.
  • Magnetic field sensor
  • Angle or rotation sensor
  • Thermal sensor
  • Geiger sensor

Programming

There are many possibilities for programming the Mindstorms NXT: In the consumer kit, a graphical programming software is provided. It is called NXT-G. It is Labview-based but requires no LabView skills. It is very easy to start using NXT-G.

The NXT-G software is not included in the education version of the Lego kit.

  • Text programming:
    • .NET languages , such as C sharp or Visual Basic .NET , using Microsoft Robotics Studio
    • The NBC , assembly language
    • The NXC , who is a close language C . It is free and open-source.
    • RobotC is another C-based programming language developed by Carnegie Mellon University in the United States
    • Lejos is an open-source API based on the Java language
    • Urbiscript: the language of the Urbi ( Universal Real-Time Behavior Interface )
    • In Ada (complete or Ravenscar profile )
    • An ROS library also exists for the Lego robot
    • A Matlab library created by the University of Aachen 1 also exists.
  • Graphic programming:
    • NXT-G, the Lego version of LabVIEW for easy handling
    • Microsoft Robotics Studio
    • DialogOS allows to control the robots by the voice
    • Robolab is a possible programming of the National Instrument Group

Notes and references

  1. Matlab Library [ archive ] , rwth-aachen.de