Trash Robotic Router Platform

Taiksonprojects.blogspot.com
David Meléndez CanoDavid Meléndez Cano
@taiksontexas
TRASH ROBOTIC ROUTER
PLATFORM

2
¿What is TRRP?
➔
Low (or null) cost embedded platform
➔
“Internet of things”
➔
Use whatever is liying around
➔
“Trash” can be useful
➔
DO NOT RECYCLE!!! ->>> REUSE!!!

Use your old (or fancy new) router as robotic platform
➔
No initial investion. You already have the router!
➔
Change the firmware-> Embedded Linux OpenWRT
Created Robots using this philosiphy
ROVER Texas Ranger: Linksys
WRT54GL
Drone ATROPOS:
La Fonera 2201

Round one: ROV Texas Ranger

Round two!: Atropos Quadcopter
➔
Fonera 2201
➔
OpenWRT
➔
Stabilization process
➔
HTML5 telemetry and control

A-B-C for quad drones

Router platform: GPIOs for I2C
Led lights are driven by SoC CPU pins

Router platform: GPIOs for soft I2C and serial port
GPIO---> I2C / RS232
GPIO leds
Serial port

Router platform: Module load
rm /etc/modules.d/59i2cgpio
echo "i2cgpiocustom bus0=0,4,7 bus1=1,3,1"
>/etc/modules.d/59i2cgpiocustom
echo "i2cgpio" >/etc/modules.d/60i2cgpio
[reboot]
i2cdetect /dev/i2c0

Router platform: Serial port
stty -F /dev/ttyS0 raw
stty -F /dev/ttyS0 speed 115200

Router platform: Gyroscope
Wii Motion Plus
Triaxial gyroscope
I2C port
•
Gives angular velocity on each axis
•
Real angle: angular velocity * time ? → not so easy

Router platform: Accelerometer
Wii Nunchuck
Triaxial accelerometer
Puerto I2C
G forces in each axis.

Router platform: Magnetometer
- HMC5881L
-Units: Gauss
-Accelerometer only cancels gyro drif for pitch & roll
-Yaw gyro drif must be cancelled with a compass (magnetometer)

Router platform: Reading I2C sensors
#include <linux/i2cdev.h>
f_i2c0=open(I2C0, O_RDWR);
ioctl(f_i2c0, I2C_SLAVE, 0x52);
     write(f_i2c0, buff_out, data_size);

     read(f_i2c0, buffer,size);
. Ej Wii Motion+: 0x52
•
Petición de datos escribiendo al dispositivo
•
Lectura de datos en buffer

Imagen: “The Balance Filter” MIT
Gyroscopes
Accelerometer
Obteniendo ángulos absolutos con respecto a la Tierra

Mejor: Matriz de Cosenos Directores (DCM)

We will work with:
➔
Absolute angle: (rad) filtered value
➔
Angular velocity : (rad/sec) from gyroscopes
➔
Angullar acceleration: (rad/sec/sec) calculated from
angular velocity

Proportional Integral Derivative Controller

Proportional
error=current_value-last_value
Proportional_term=Proportional_term*error

Integral
accumulated_error=accumulated_erro
r+(error*time_between_samples)
Integral_term=Integral_term*accumu
lated_error

Derivative
error_speed=error-
last_error/time_between_samples
Derivative_term=Derivative_term*error_spee
d

Nested PID
P Controller
PID controller
Angle
Angular
Velocity
Router
Serial port

Router platform: Motor signal board (PWM)
-PIC Microcontroller receives motor speeds via router serial port
-It converts those values into 4 time-fixed digital signals (PWM)
Fonera
/dev/ttyS0 PIC16f876A
ESC
Motores

Router Platform: IMU (Inertial measurement Unit)
➔
Critical process that has to be executed in a time-fixed ratio
setitimer(ITIMER_REAL,&i_int,NULL);
(void)signal(SIGALRM ,timeout_real);
➔
It compites with the rest of the process for CPU time
➔
Changing priority with nice is not sufficent:
➔
Real Time scheduling → FIFO, Round Robin
#include <sched.h>
schedule.sched_priority=sched_get_priority_max(SCHED_FIFO);schedule.sched_priority=sched_get_priority_max(SCHED_FIFO);
sched_setscheduler(pthread_self(), SCHED_FIFO,&schedule);sched_setscheduler(pthread_self(), SCHED_FIFO,&schedule);

WATCHDOG process notifies to kernel that system is not hanged
●
It consumes SCHED_FIFO process time
●
What happens if router hangs during flight->
➔
ioctl(“/dev/watchdog”, WDIOC_KEEPALIVE, &dummywd);

Actuator hardware
Electronic Speed controller (ESC)
Brushless motors “Outrunner”.

HTTP CONTROL
Httpd.c:
[...]
if (strncmp(tptr, "cgibin/ajaxinput", 17) == 0) {
[...]
strcpy((char *)shmat(shmget(9998, 30, IPC_CREAT | 0666), NULL, 0),g_query);
exit(1);
}
[...]
Pilot commands can be transmitted via AJAX or UDP packets
-AJAX → uses DOM events and sends commands accordingly
-A separate program reads USB Joypad and resends via UDP
http://atropos/cgibin/ajaxinput?QQZ[GAS]Z[ALABEO]Z[CABECEO]Z[GUIÑADA]Z
Router Httpd.c is tweaked to process the query faster.

USB Joypad control (GNU/Linux with joydev.ko)
cat /dev/input/js0

pad=open(“/dev/input/js0”,O_RDONLY);
reads=read(pad,msg,MSG);
  (msg[7]==2)
      gas=((analog+127))*GAS_FACTOR;
    [...]
    (msg[7]==4)
      yaw=analog*YAW_FACTOR;
    [...]
    (msg[7]==1)
      pitch=analog*PITCH_FACTOR;
    [...]
    (msg[7]==0)
      roll=analog*ROLL_FACTOR;
    [...]

What about Android?

Zsun
Bully

HEADER
AP
“ATROPATROP”
COMMAND
Preamble
Gas
Pitch
Roll
Yaw
SEQUENCE
NUMBER
CHECKSUM
INIT.
VECTOR
Forged Beacon Frame injection
Protected with AES-128
BEACON FRAME PAYLOADBEACON FRAME PAYLOADHEADER

Demo?Vuelo Atropos Quadrocopter

Thank you!Thank you!
David Meléndez CanoDavid Meléndez Cano
@TaiksonTexas

Trash Robotic Router Platform

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