Intro to Mechatronics from Strasbourg University.pdf

7/30/2019 Intro to Mechatronics from Strasbourg University.pdf

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Introduction to Mechatronics

Discover robots with the Lego Mindstorms

Loc Cuvillon, Bernard Bayle

Ecole Nationale Suprieure de Physique de StrasbourgStrasbourg University

March 13, 2009

Introduction to Mechatronics 1 / 97
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You are free to copy, to modify, to adapt and distribute this document.

Latex sources of this document should be available on the authors webpage.

LEGO and Mindstorms NXT are trademarks of the LEGO Group, which does

not sponsor, authorize or endorse this document.

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Lego Mindstorms Hardware NXT Programming with NBC/NXC Bluetooth communication

Part I

Hardware and Programming under Linux

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Outline

1 Lego Mindstorms HardwareOverviewNXT Brick Hard/Firm-ware

2 NXT Programming with NBC/NXCNBC/NXC basicsNXC structure and statementsNXC I/O API

3 Bluetooth communication

Bluetooth ProtocolBluetooth communication with PCBluetooth communication between NXT

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Outline

1 Lego Mindstorms Hardware

Overview

NXT Brick Hard/Firm-ware

2 NXT Programming with NBC/NXCNBC/NXC basics

NXC structure and statements

NXC I/O API


Bluetooth Protocol

Bluetooth communication with PC

Bluetooth communication between NXT


L Mi d t H d NXT P i ith NBC/NXC Bl t th i ti
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References

NXC Programming

[NXC07] J.C. Hansen, NXT Power Programming, Variant Press, 2007

[NXC] J.C Hansen, Not eXactly C Programmers Guide,

http://bricxcc.sourceforge.net/nbc/

[NXCT] D. Benedettelli. , Programming LEGO NXT Robots using NXC,http://bricxcc.sourceforge.net/nbc/nxcdoc/NXC_tutorial.pdf

NXT Bluetooth and USB communication

[LINXT] Lego Mindstorms NXT brick in Linux via USB,

http://sourceforge.net/projects/linxt/

[BLUE] J. Schultz, Lego, Bluetooth and Linux, http://www.cs.uleth.ca/benkoczi/3720/data/NXT_Bluetooth_handout-jeremy.pdf

[NXTLIBC] Lego Mindstorms NXT Bluetooth library in C,

http://www.quietearth.us/nxtlibc.htm


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References

LEGO resources and documentation

[LEGO] Bluetooth Developer Kit and Hardware Developer Kit,

http://mindstorms.lego.com/eng/Overview/NXTreme.aspx


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Overview

Outline


Overview




NXC I/O API


Bluetooth Protocol




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Overview

Lego Mindstorms Overview

NXT Inputs

NXT Outputs

Sound Sensor

Touch Sensor

Light Sensor

Servo Motors

Ultrasonic Sensor

with position encoders

(contact switch)

(pressure in dB)(distance in cm)

(light intensity in %)

LCD screen

Buttons

NXT processorwith Bluetooth




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Overview

NXT brick

battery level

NXT brick name(configurable)

USB 2.0 connectorbluetooth indicatorB : ON, invisible

B< : ON, visible

B : ON, connected

usb indicatorusb : connected, working

][ : connected, not working

loudspeaker

On/Enter button

Clear/Go back buttonNaviguation buttons

S4S1 S2 S3Sensor port

OUT_A OUT_B OUT_CServo outputs


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g g g

Overview

NXT brick Menus

On/off

Connections

Visability

Search

to bluetooth device)

(search and connect

Motor rotation

Sound dBA

Ultrasonic cm

Sound files

Software File

(bytecode executable

upload from computer)

(LCD display

distance from sensor)

Delete Files

Volume

NXT version

(firmware

version)

NXT ProgramSettingsBluetoothMy files View(testing)

NXT Program Example :

= "Forward until an object detection, then turn left. Repeat"

NXT files

saved

in




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g g g

Overview

NXT-G (LabView)

advance graphical interface for programming NXT

functional block and control flow


http://./play-movie-nxtghttp://find/


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Overview

Some fun NXT Projects

Rubiks Cube Solver

by Daniele Benedettelli

NXTway GSby Y. Yamamoto


http://./play-movie-segwayhttp://./play-movie-utopyhttp://find/


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Outline


Overview




NXC I/O API


Bluetooth ProtocolBluetooth communication with PC



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Hardware specification

S1 S2 S3 S4

PWM signal generator

8bit AVR CoProcessor

A/D converter for analogic sensor

(light,sound,touch )

USB 2.0 connector

high speed communication line

on Port S4 (for future use)

RS485 UARTBluetooth Chip

class 2

10 meters range

Amtel 32 bit ARM Processor

48MHz, 64KB RAM

256KB FLASH

I2C interface with AVR proc.

and digital sensor (ultrasonic)

single and double Hbridge

(OUT_A and OUT_BC)

LB1930 & LB1836

AT91SAM7S256


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Hardware specification

I2C: Inter-Integrated

Communication need 3 lines

(data,clock,ground)

UART: Universal Asynchronous

Receiver Transmitter(serial line/port)

Note:

-each sensor port (S1-4) can be used

with digital or analog sensor.-6 wires by port: 3 for I2C + 3 for

analog signals


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NXT Firmware

Memory

Boot Recovery

(SAMBA)ROM

FLASH

RAM

64K

Firmware

(sound, .rxe...)

Files

Running

executables

256K

Processor

Boot loader/boot code

LEGO firmware

with CodeByte interpreter

Executables (.rxe)

Software

Boot code/loaderinitialization of the hardware

load the firmware

Firmware : a basic operating system

multi-thread (thread: light task)provides an API for I/O

(displays the menus)

interprets ByteCode executables

(.rxe)

firmware and files stored in

FLASH memory

BOOT CODE stored in RAM

allow to update firmware


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Outline


Overview


2

NXT Programming with NBC/NXCNBC/NXC basics


NXC I/O API







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NBC/NXC basics

Outline


Overview


2



NXC I/O API





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NBC/NXC basics

NBC/NXC

NBC: Next Byte Codes

name of an assembly language

name of an open source assembler available under MPL license

produce executable code for the native LEGO firmware

NXC: Not eXactly C

high level programming language: C-like syntax

compiler built upon nbc

produce ByteCode executables (.rxe)

NBC and NXC available for Linux, MAC OS, Windows

custom Firmwares to replace LEGO firmwares are available : LeJOS

(JAVA-VM) for Java programming


http://goforward/http://find/http://goback/


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NBC/NXC basics

Compilation and Execution

Compilation under linux

nbc compiler available from [NXC]

options of nbc available with nbc -help

compilation of a source file *.nxc

nbc toto.nxc -O toto.rxe

Run execution

toto.rxe available in Program Files folder via menus after upload

start/stop via buttons

3Upload of .rxe file

USB cable

1Source editing

2Compilation

4Execution

Crosscompilation process


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NBC/NXC basics

USB Upload

Detection of the NXT brick

lsusb: listing of connected USB device

Bus 002 Device 004: ID 0694:0002 Lego Group

via NXC

need complex configuration of linux device manager (udev)upload command

nbc -d -S=usb toto.rxe

via LiNXT (prefered method, [LINXT])

LiNXT: Perl script with automatic search of the brickcommand to upload, download and get NXT information

to get help linxt -h

to upload a file (as root user):

linxt -u toto.rxe


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Outline


Overview


2



NXC I/O API





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Statements 1

comments:

//This is a comment

/*This is a comment*/

variablesbool, byte, unsigned char, char 8 bit

unsigned int, short, int 16 bitunsigned long, long 32bit

string Array of byte

struct User define

Arrays Array of any type

declaration of variable

int i;

int x=0x10; // 16 in hexadecimal

int y=10; // 10

string msg=toto;


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Statements 2

assignment

x=y+2;

x+=y; // equivalent to x=x+y;

arrays (no pointers)

byte myvector[2]; // 2 byte arrayint myarray[]; // int array (no dimension)

ArrayInit(myarray,0,10); // alocation of 10 null entries

myarray[0]= 15;

conditions= equal

!= not equaltrue

false

Expr True if Expr!=0&& logical AND between conditions

|| logical OR between conditions


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Control structures

if, if . . . else

if (x==1)

{x=2; z=3;}

elsey=4;

for

for (i=1; i


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Control structures

switch

switch (x)

{

case 1 :

z=3;

break;

case 2 :

// some code

break;

default:

// some code

break;}

repeat and until control structure available but not C standard



NXC t t d t t t
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Program structure: Tasks

task music (){ PlayTone(440,3000); }

task motion ()

{

while(true)

{ OnFwd(OUT_A,50);Wait(1000); }

}

task main ()

{ // motion

start music; //and musicstart motion; //in parallel

} // execution

multithreading in NXT

=concurrent execution of tasks

number of task and function must

be < 256

at least an init task called mainneeded

API

precedes(task1,task2,..);

launch the task after end of main

start task1 or StartTask(task1) ;

StopAllTasks();



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Program structure: Functions

parameter passed by value

return for non-void function

void foo (int x)

{

x++;}

task main

{

int y=1;

foo(y);//y still equal to 1

}

parameter passed by reference

void foo (int &x) // !!

{

x++;

}

task main

{

int y=1;

foo(y); //y now equal to 2

foo(2); // ERROR(one-variable)

}



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Preprocessor

Preprocessor directive

include files

#include foo.h#include //error no libray path

macro and define (recommended!)

#define TIMEOUT 200 //0.2 ms timeout

#define NORMAL_SPEED 50



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NXC I/O API

Outline


Overview


2 NXT Programming with NBC/NXC

NBC/NXC basics


NXC I/O API






NXC I/O API
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NXC I/O API

some functions of the API

Timings

wait(2000);

// sleep for 2s

x=CurrentTick();

// sys time in ms

Math Functions

-Cos, Sin, Abs, Acos in degree

-returns 100 times the value

x=cos(60); //returns 50

Strings

msg=numToStr(i)

// convert number in string

msg=StrCat(str1,str2)// concatenation

Sound

Play tone (440,500);

//440: frequency

//500: duration



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LCD API

task main ()

{

int i=1;

TextOut(0,LCD_LINE1,"toto:");

// display toto on line 1

NumOut(20,LCD_LINE1,i);//display i on line 1 and column 20

Wait(3000);

ClearScreen();

LineOut(40,40,60,60);

//plot a line from (40,40) to (60,50) coordinates

Wait(3000);

}



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Output Control API : Servo-motor

Unregulated mode

no regulation (speed can vary according to the load)

reference = power in % , output selection= OUT_A, OUT_BC, OUT_ABC

. . .

task main(){

OnFwd(OUT_AC,85); //motor AC fwd at 85% of power

Wait(1500); // run for 1.5 s

OnRev(OUT_A,90); //motor A reverse at 90%,

//C still going fwd at 85%

Float(OUT_C); //motot C power off, free decelerationWait(1500);

Off(OUT_ABC); //motor ABC power off with braking

}



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Regulated mode

PID regulation of the motor speed (power will increase if load increases)

reference = speed in % of maximal speed

task motor_status(){while(1)

NUMOUT(0,LCD_LINE1,MotorActualSpeed(OUT_A));//diplay not speed but power!!}

task main() {start motor_status;

OnFwdReg(OUT_A, 40, OUT_REGMODE_IDLE);//same as OnFwd, no regulationWait(5000);OnFwdReg(OUT_A,40,OUT_REGMODE_SPEED); //speed regulationWait(5000);Off(OUT_A);StopAllTasks();

}



NXC I/O API
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Synchronized mode

only for a pair of motors (OUT_xy)

synchronized the rotation (useful to go in straight line for mobile robot)

if one motor slow down, the other adapts

last parameter: steering or turn percentage

task main() {

OnFwdSync(OUT_AC, 50, 0); //same as OnFwd, no regulation

Wait(2000);

OnFwdSync(OUT_AC, 40 , 50); //motor A stop

Wait(2000);

OnFwdSync(OUT_AC, 40 , 100);

//motor A speed opposite of C

Wait(2000);

Off(OUT_AC);

}



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Position-based mode

regulation of rotation position in degree

#define degree 180

task main() {

RotateMotor(OUT_AC,56, degree);

//rotation of 180 degree at 56% of power

}



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Advance Output API : Write File

Position-based mode

wite written in flash memory

return value of the API: LDR_FILEEXIST, LDR_FILEISFULL,. . .

read file API : OpenFileRead(), Read()

task main() {byte handle;

int result;

result=CreateFile("test_write.rxe",256,handle);

//file of 256 bytes

if (result==LDR_SUCCESS)

{ int i=3;result=Write(handle,i);

}

CloseFile(handle);

}



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Input API : Sensors

Configuration of the input ports

1 a TYPE (TOUCH,SOUND. . . ) with SetSensorType(port,TYPE)

2 a MODE (RAW, BOOL. . . ) with SetSensorMode(port,MODE)

TYPE Description

SENSOR_TYPE_TOUCHSENSOR_TYPE_LIGHT_ACTIVE light sensor with LED on

SENSOR_TYPE_LIGHT_INACTIVE light sensor with LED offSENSOR_TYPE_SOUND_DB sound pressure in dB

SENSOR_TYPE_TOUCH I2C sensor (Ultrasonic)

MODE DescriptionSENSOR_MODE_RAW value between 0 < x < 1024

SENSOR_TYPE_BOOL 0 if x


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Input API : Sensors

Default configuration of the input ports

high-level functions with the default mode : SetSensorXXXX(port)

task main() {

SetSensorType(S1,SENSOR_TYPE_TOUCH);SetSensorMode(S1,SENSOR_MODE_BOOL)

SetSensorTouch(S1); //idem than the 2 previous line

SetSensorSound(S3);

//Sound sensor on port 3, default pourcent?

SetSensorLight(S4); // port 4, default mode : percentSetSensorLowSpeed(S2);

// I2C sensor (Ultrasonic,..) on port 2

}



NXC I/O API
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Input API : Sensors and rotation

Reading

analog sensor: SensorValue(SX) or the equivalent macro SENSOR_X

for I2C ultrasonic sensor: SensorUS(port)

rotation count on servo_motor: MotorRotationCount(OUT_X)

task main() {

bool cont; int dist;

SetSensorTouch(S1);SetSensorLowspeed(S2);ResetRotationCount(OUT_A);

while(1)

{ cont=SENSOR_1; // or cont=SensorValue(S1);dist=SensorUS(S2);if (cont==1)

TextOut(0,LCD_LINE1,"Pressed");else TextOut(0,LCD_LINE1,"Release");if (MotorRotationCount(OUT_A) > 180)

TextOut(0,LCD_LINE2,"Half-rotation!"); } }



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One example : 3 implementation

Move forward but avoid obstacles

#define NEAR 15 //cm

task main(){

SetSensorLowspeed(S4);

while(true){OnFwd(OUT_AC,50);

while(SensorUS(S4)>NEAR);//do nothing: waitOff(OUT_AC);OnRev(OUT_C,40); //turn

//angle linked to wait timeWait(800);

}

}


task main(){SetSensorLowspeed(S4);

while(true){

OnFwd(OUT_AC,50);

if (SensorUS(S4)


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One example : 3 implementation


mutex motor_mutex;

task obstacle_test(){ while(1)

{if (SensorUS(S4)


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Outline


Overview



NBC/NXC basicsNXC structure and statements

NXC I/O API






Bluetooth Protocol

O tli
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Outline


Overview




NXC I/O API






Bluetooth Protocol

Bluetooth
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Bluetooth

wireless protocolfor electronics (phone headset), computer peripherals (WiiMote,

keyboard)

2.4 GHz short-range radio frequency bandwidth : unlicensed frequency

Classclass 1: 100 mW 100meters

class 2: 2.5 mW 10 meters (LEGO NXT)

Search and Pairing

search service available to find new Bluetooth device

pairing: trust communication by learning of a common passkey

-input of the passkey on both device

-key used to encrypt communication



Bluetooth Protocol

Bluetooth piconet
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Bluetooth piconet

Master and slaves devices (max: 7 slaves)

on master by piconet (slaves synchronized on his clock)

slaves can not initiate a data packet transfer

slaves can send a response packet right after the master one

(synchronous communication)

slaves can not communicate between them



Bluetooth Protocol

Bluetooth NXT Communication Protocol
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Bluetooth NXT Communication Protocol

NXT Direct Command (also for USB communication)

direct command interpreted by the NXT Slave firmware and translatedinto functions

any Bluetooth device (phone, PC, NXT,..) can send command via

Bluetooth packets

NXT Direct Command Telegramlength of the datagram (without the 2 Length bytes)

command type

0x00: Direct command, response required0x80: Direct command, no response0x02: Means a response datagram from slave

command code (Ex: 0x0B=GetBatteryLevel 0x03=PlayTone)

parameters of the command, or return value

byte 1

Length, LSB Length, MSBCommand

TypeCommand

byte 2 byte 3 byte 4 byte 5 byte 6 byt..

Parameters..................




Outline
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Outline


Overview




NXC I/O API







Pairing between PC and NXT -1
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Get NXT Bluetooth address

each Bluetooth as an unique address on 6 bytes (MAC address)

1 command hcitool : give name and Bluetooth address of available device

>hcitool scanScanning ...

00:16:53:04:B3:46 NXT

2 LiNXT -i , while NXT connected by USB

>sudo ./linxt -i

Device information:

NXT name: NXT02

Bluetooth address: 00:16:53:02:f3:31




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Pairing between PC and NXT 2

Pairing under ubuntu Linux1 set the key in the pop-up when using the following connect program

2 use NXT search and Linux Bluetooth-applet:

Linux: right click on the Bluetooth-applet > preferencesset a Bluetooth name for the PC dongleNXT: menu Bluetooth > search

select your PC name and validatevalidate the default passkeyLinux: a pop-up ask for the passkey, give the same

3 it is a one time operation, NXT now appears in Bluetooth-applet >

preferences > known devices




Programming of Direct Commands
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Programming of Direct Commands

Socket

a socket is an abstraction for an inter-process communication (over

network)

a socket can be bind to an IP or Bluetooth address

then we can read, write on the socket data between 2 process

Compilation with gcc

gcc -o executable_name -lm -lbluetooth source_name.c

to link with Bluetooth library: -lbluetooth (math: -lm)

Example: play_tone.copening of a socket bind to NXT Bluetooth address

write of the direct command PlayTone 0x03

read of the response (status)




play tone.c
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play_tone.c

#include

#include #include //socket lib#include #include //bluettoh lib#include #define max_message_size 59

int nxtsocket; //on declare la socket

void init_bluetooth(char *btAddress) {struct sockaddr_rc addr={0};//structure du type sockaddr_rcint status;

nxtsocket = socket(AF_BLUETOOTH, SOCK_STREAM, BTPROTO_RFCOMM);

addr.rc_family = AF_BLUETOOTH;addr.rc_channel = (uint8_t) 1;str2ba(btAddress, &addr.rc_bdaddr);// convertit un string en adresse

status = connect(nxtsocket, (struct sockaddr *)&addr, sizeof(addr) )//connection }




play tone.c
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play_tone.c

void nxt_tone(void) {/**0x06 0x00 : length =6 bytes

0x00 : direct command with response0x03 : Playtone commande0x5B 0x1C : parameter 1 - 7259 (200-14000Hz)0x88 0x13 : parameter 2 - 0x1388=5000 (ms)**/

char cmd[8]={0x06, 0x00, 0x00, 0x03,0x5B ,0x1C ,0x88,0x13};char reply[max_message_size];

write(nxtsocket, cmd, 8); //send PlayTone command

read(nxtsocket, reply, 5); //read response

// check responseif (reply[2] != 0x02) fprintf(stderr, "not a response datagramm");if (reply[3] != 0x03) fprintf(stderr, "not the reply to play tone");if (reply[4] != 0x00) fprintf(stderr, "status not ok");

}




play tone.c
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p y_

int main (void) {int blevel;

char btaddress[18] = "00:16:53:02:f3:31"; //NXT adressinit_bluetooth(btaddress); //open connectionnxt_tone(); //direct commandclose(nxtsocket);return 0;

}




NXTlibC
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A simple library to perform Direct Command

wrap the previous code in nice function

compilation:

gcc -lm -lbluetooth -lnxtlibc test.c -o test

API of NXTlibC : samples

nxt_bluetooth_initialize() , nxt_bluetooth_done()

get_battery_level(),play_tone()

set_touch_sensor(), get_touch_value()

message_write(), message_read() (see next section)




play_tone.c with NXTlibC
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p y

#include #include

#define MAC "00:16:53:02:f3:31"

int main (void){int ret;

// * * * * * Connection a la brique * * * * * //nxt_bluetooth_initialize(MAC);

play_tone(500, 2000);

// * * * * * Verification de la batterie * * * * * //ret = get_battery_level();

// *** all motor at 10% of power in regulate mode**//ret = _set_output_state(ALL_WHEEL,10,

MODE_MOTORON|MODE_BRAKE|MODE_REGULATED,REGULATION_MODE_MOTOR_SPEED|REGULATION_MODE_MOTOR_SYNC,0x00, MOTOR_RUN_STATE_RUNNING, 1000000);

nxt_bluetooth_done();

return 0; }




Outline
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Overview




NXC I/O API







Connection between NXT
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Via the Bluetooth menu

search for others NXTconnect it on one of the free channel 1, 2 or 3 (up to 3 slave)

Master

Channel 0

Up to 3 slavesChannel 13

Nxt

Piconet




NXC Bluetooth API
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Via the Bluetooth menu

10 mailbox on each NXT to exchange messages

if there is no read program while sending = message lost

direct commands available to control the slave

Example of message exchange

master : check slave connection, send message to mailbox 5 on slave,

read again message in mailbox 1 on slave,

slave : check master connection, read its mailbox 5,

put an message in its mailbox 1




Message exchange
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//MASTER#define INBOX 1

#define OUTBOX 5

sub BTCheck(int conn){if (!BluetoothStatus(conn)==NO_ERR){

TextOut(5,LCD_LINE2,"Error");Wait(1000);Stop(true); }

}

task main(){string in,out="hello from master!";

BTCheck(1); //check slave connectionTextOut(10,LCD_LINE1,"Master Test");

SendRemoteString(BT_CONN,OUTBOX,out);

while (1){ ReceiveRemoteString(INBOX, true, in);TextOut(10,LCD_LINE3,in); }

}




Message exchange
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//SLAVE#define INBOX 5

#define OUTBOX 1


TextOut(5,LCD_LINE2,"Error");Wait(1000);Stop(true);

}}

task main(){string in,out="thanks, master!";

BTCheck(0); //check slave connection

TextOut(10,LCD_LINE1,"Slave Test");

while(1){ ReceiveRemoteString(INBOX, true, in);SendResponseString(OUTBOX,out); // Not SendRemote !!TextOut(10,LCD_LINE3,in); }

}




NXC Bluetooth API
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Example of Direct Command

master : check slave connection,

send play_tone command,

wait for response status,

send reset position on motor A

wait for response status,

send full speed command on motor A with speed regulation




NXC Bluetooth API
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//MASTER


TextOut(5,LCD_LINE2,"Error");Wait(1000);Stop(true); }

}

task main(){BTCheck(1);

RemotePlayTone(BT_CONN, 4000, 100);until(BluetoothStatus(BT_CONN)==NO_ERR);Wait(1100);

RemoteResetMotorPosition(BT_CONN,OUT_A,true);until(BluetoothStatus(BT_CONN)==NO_ERR);

RemoteSetOutputState(BT_CONN, OUT_A, 100,OUT_MODE_MOTORON+OUT_MODE_BRAKE+OUT_MODE_REGULATED,OUT_REGMODE_SPEED, 0, OUT_RUNSTATE_RUNNING, 0)

}


Mobile robots Wheeled Mobile Robots Technology Navigation
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Part II

Introduction to Mobile Robotics



Outline
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4 Mobile robotsClassification and applicationsIssues

5 Wheeled Mobile Robots TechnologyMechanical architecture

Embedded systemActuatorsSensors

6 NavigationLocalizationMappingPlanningControl



Outline
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4 Mobile robotsClassification and applications

Issues

5 Wheeled Mobile Robots Technology

Mechanical architecture

Embedded systemActuators

Sensors

6 Navigation

Localization

MappingPlanning

Control



Classification and applications

Outline
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4 Mobile robotsClassification and applications

Issues




Sensors

6 Navigation

Localization

MappingPlanning

Control




Mobile robots classification
http://find/


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Mobile robots

Robots with a moving base, by opposition with robotic manipulators.

Classificationbased on the locomotion type.

Wheeled robots




http://goforward/http://find/http://goback/


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Mobile robots



Legged robots




http://find/


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Mobile robots



Legged robots




http://find/


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Wheeled robots, legged robots+

flying robots, undersea robots.




Wheeled mobile robots applications
http://find/


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A few industrial applications

Automatic Guided Vehicles (AGV)

FMC Technologies

http://www.fmcsgvs.com




http://find/


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More and more general public applications

ToysTribot, WowWee

http://www.wowwee.com

Automatic vacuum cleanersDirtyDog, iRobot

http://www.irobot.com




http://find/


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Education and research

Khepera II , K-team

http://www.k-team.com

1 h autonomy, 1 m/s max

7x3 cm, 80g (payload


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A few High-Tech applications

Spatial exploration robots

Sojourner mission to Mars

http://mars.jpl.nasa.gov/MPF/rover/sojourner.html






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A few High-Tech applications

Inspection

http://crasar.csee.usf.edu



Issues

Outline
http://find/


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4

Mobile robotsClassification and applications

Issues




Sensors

6 Navigation

Localization

MappingPlanning

Control



Issues

Issues


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Technology

Issues:

mechanical architecture

embedded system

actuators

sensors

Navigation

Issues:

localization

mapping

planning

control



Outline
http://find/


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4


Issues




Sensors

6 Navigation

Localization

MappingPlanning

Control




Outline
http://find/


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4


Issues




Sensors

6 Navigation

Localization

MappingPlanning

Control




Mobile robots mechanical architecture


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A large amount of systems

several types of wheels

articulated platforms

caution: all the architectures are

not kinematically consistent

Lego Tribot: a simple differential drive

mobile robot

simple to build: 2 fixed wheels,

with 2 independent actuators

differential drive locomotion

nonholonomic, nonlinear. . . not so

simple




Mobile robots mechanical architecture


83/106

A large amount of systems

several types of wheels

articulated platforms

caution: all the architectures are

not kinematically consistent

Lego Tribot: a simple differential drive

mobile robot

simple to build: 2 fixed wheels,

with 2 independent actuators

differential drive locomotion

nonholonomic, nonlinear. . . not so

simple




Lego TriBot modelling

Wheels velocities (!angles


84/106

O

y

xx

y

CIR

O

L

v

vd

vg

r

l

Wheels velocities (!angles

convention) :

vr = rr = ( + L)

vl = rl = ( L)

and then:

v =

vr + vl

2

=r( r + l)

2L

Differential kinematics:

x = vcos y = vsin

=



Embedded system

Outline
http://find/


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4 Mobile robots


Issues




Sensors

6 Navigation

Localization

MappingPlanning

Control



Embedded system

Lego TriBot embedded system
http://find/


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NXT Block

The core of the robot, which enables to get measurements and to control theactuators.

Refer to the first part of the talk for more details. . .

NXT Inputs

NXT Outputs

Sound Sensor

Touch Sensor

Light Sensor

Servo Motors

Ultrasonic Sensor

with position encoders

(contact switch)

(pressure in dB)(distance in cm)

(light intensity in %)

LCD screen

Buttons

NXT processorwith Bluetooth



Actuators

Outline


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4 Mobile robots


Issues




Sensors

6 Navigation

Localization

MappingPlanning

Control

Introduction to Mechatronics 80 / 97 Mobile robots Wheeled Mobile Robots Technology Navigation

Actuators

LEGO Mindstorms Servo-motor


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Encoder wheel andwith optical sensor

Gear train (1:48)

Running_modes

ON: power control

open loop controlreference: % of the max power

ON & REGULATED:speed regulationuse of position sensor signalsclosed loop with PID controller

ON & BRAKE: electronic braking

OFF: coasting (free motion)


Actuators

LEGO Mindstorms Servo-motor driving
http://find/


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O V

9 V

90% duty cycle

O V

9 V

10% duty cycle

Power control

PWM (Pulse Width Modulation) ofa 8 kHz signal

90% duty cycle 8.1 V20% duty cycle 1.8 V

+Vcc

0V

In2

In2In1

M

In1

+

In1=High, In2=Low In1=Low, In2=High

+Vcc

0V

In1 In2

In2In1

M+

Direction and braking

H-bridge with DC motorsIN1 IN2 Action

H L Forward

L H Reverse

L L Brake


Actuators

Electronic braking
http://find/


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e

i

U

R

L

= Ki

= Ke

e : back e.m.f

: motor torque

: motor angular speed

Braking

1 motor motion: e= 0

2 short circuit current i eR

in opposition


Sensors

Outline
http://find/


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4 Mobile robots


Issues




Sensors

6 Navigation

Localization

MappingPlanning

Control


Sensors

Ultrasonic Telemeters


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http://www.pages.drexel.edu/ kws23/tutorials/ultrasonic/ultrasonic.html

Properties:alternate emission/reception

sounds not heard by human

ear (ultrasound=20kHz to

200kHz)

minimal measurementdistance and variable

maximal frequency=f(maximal

distance)

different drawbacks

(directivity, reflectivity,

ambient conditions sensitivity)


Sensors

Lego TriBot Ultrasonic Telemeter


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Outline
http://find/


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4 Mobile robots


Issues




Sensors

6 Navigation

Localization

MappingPlanning

Control


Localization

Outline
http://find/


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4 Mobile robots


Issues




Sensors

6 Navigation

Localization

MappingPlanning

Control


Localization

Dead reckoning

Odometry
http://find/


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Odometry

Computation of the configuration by velocities integration:

x(t) =

Zt0

x()d, y(t) =

Zt0

y()d, (t) =

Zt0

()d.

The TriBot example, with a Te sampling period:

x(k + 1) = x(k) + v(k)Te cos (k)

y(k + 1) = y(k) + v(k)Te sin (k)

(k + 1) = (k) + (k)Te

Remark

Odometry: current configuration relative to the initial configuration.


Mapping

Outline
http://find/


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4 Mobile robots

Classification and applicationsIssues




Sensors

6 Navigation

Localization

MappingPlanning

Control


Mapping

Environment mapping

Occupancy grid: discrete map of the environment
http://find/


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Occupancy grid: discrete map of the environment

Cell decomposition, with probability of collision from sensors measurements.

The simplest case: binary grid, without filtering, trusting the odometry

localization.


Planning

Outline
http://find/


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4 Mobile robots




Embedded system

Actuators

Sensors

6 Navigation

Localization

MappingPlanning

Control


Planning

Configuration space

Definition
http://find/


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Configuration space = set of all the accessible configurations of the robot:robot represented as a point: obstacles augmentation

robot with complex shapes and kinematics: more difficult problem. Over

pessimistic obstacle augmentation can close doors !



Planning

Roadmaps

Visibility roadmap


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y p

Graph capturing the environment topology from the polygonal obstaclesvertices.

link initial point and goal to visible vertices



Planning

Roadmaps

Visibility roadmap
http://find/


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y p


apply the same to the new vertices



Planning

Roadmaps

Visibility roadmap
http://find/


103/106

y p


search for a path in the graph



Control

Outline

4 Mobile robots
http://find/


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4 Mobile robots




Embedded system

Actuators

Sensors

6 Navigation

Localization

MappingPlanning

Control



Control

Path following problem

Problem
http://find/


105/106

Find such that d(P, C) decreases to zero, with v imposed.

x

y

Ox

O

C

r

Or

xr

yr

y

P

d

a

e

It can be showna that:

s =vcos e a sin e

1 dc(s)

,

d = vsin e + a cos e,

e = sc(s).

a|d c(s)|


106/106

d vsin e + a cos e

It comes that:

= vsin e

acos e

v

cos ek(d, e)d,

with k(d, e) 0 such that k(d,

2) = 0 gives:

d = vak(d, e)d.

Consequence

If a, v et k(d, e) > 0: |d| decreases along any path.

Restrictions

No control of the orientation.

Can be solve at the planning step.

http://find/

Intro to Mechatronics from Strasbourg University.pdf

Documents

Transcript of Intro to Mechatronics from Strasbourg University.pdf