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radhoo

Sat Apr 27 2013, 04:22PM

Registered Member #1938 Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 701

For some time now, I've been working on a Robot-dog, that should follow its user just like a ... dog. It seems trivial, but it gets complicated when putting everything into practice.
I started with a 4x4 rover:

The space inside the case was carefully distributed, placing the batteries in the center, because they are heavy:

The robot's brain is a Atmega128 microcontroller. I built a board that exposes the pins, for easier connectivity with the other modules:

At this point the plan is to mount a GPS module on the robot, and a bluetooth module (they are both connected using UART to the atmega128). The user should have a GPS and bluetooth capable phone (ex. an Android phone would do). The phone connects via bluetooth to the robot, and provides its own GPS location. The robot, using its own GPS, calculates the route that will make it get near the user, and follow him/her. The NMEA parser code has been successfully implemented:

The NMEA parser is also available as open source on Google code:

Then I built a dual h-bridge, to control the motors:

Here is first test:

An UART BLuetooth module has been added and I wrote a simple Android application that would allow me to remotely cotnrol the robot:

The design looks good, very compact, with an LCD placed in the front , to display various data and parameters (battery level, etc)

Some bad news at this point. The GPS errors are too big to allow the robot to carefully follow the user (tens of meters). This means that instead of correctly identifying the real user position, the robot would be placed randomly on a disc with a 10m radius, despite the quality GPS module used. Totally unacceptable for my project's goal.

I have decided to go for a different approach: the user will hold an ultrasonic beacon, and the robot, using a net of sensors, will detect the user position, and proceed in the user direction. Some nice PCBs were built, and the first results look promising:
300x199

The two frontal sensors can determine the direction of the incoming signal and so the user's position:

The tests shown the need to three additional sensors, one on the back, one on the left side and one to the right. The three will determine the rotation of the robot towards the source of the signal. Then the frontal sensors will command the robot's movement, carefully adjusting the direction according to the measured signal levels.
300x199

For the sake of aesthetics, I added white frontal leds and back red positioning leds. A sharp distance sensor (infrared) was also added to the front side, to help avoid obstacles. It looks so good:

The lights can be controlled remotely (I added changed the Android code for that).

Soon this work should be ready and hope to run a test outdoors. The movement's fluidity should be improved, and I'm working on that. Any suggestions are welcome!

Complete chronological project log available here:

More soon.

Legit_bacon

Sat Apr 27 2013, 09:07PM

Registered Member #4034 Joined: Thu Jul 28 2011, 10:41PM
Location: somewhere in the Southern hemisphere
Posts: 138

Wow great work! having built many a robots before i know how hard it can be to achieve a seemingly simple goal. I really like your Ultrasound beacon idea, i have experimented with IR beacons before and run into lots of trouble but using ultrasound never occurred to me.

overall a solid looking robot! Good work, keep us updated!

Legit_bacon

Sat Apr 27 2013, 09:32PM

Registered Member #4034 Joined: Thu Jul 28 2011, 10:41PM
Location: somewhere in the Southern hemisphere
Posts: 138

Have you considered using camera and blob detection on a specific colour, like lets say you've got a red shirt on. I've been playing around with this for better line following on my school team's robocup robot. We're using a raspberry pi with a simple USB webcam.
It is a very inexpensive solution in my opinion, and seems to be working very well, with raspberry pi doing all the logic and a Arduino as a "slave" unit controlling 2 stepper motors (we require preciseness for our application).

radhoo

Tue Apr 30 2013, 08:12AM

Registered Member #1938 Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 701

Hi!

I cannot rely on a camera feed, as the hardware can use an AVR microcontroller at its best, only.

A different robot that I built, was following a laser dot, using a camera, but I cannot do the same for this one:

(Other posts related to my robots:

)

Patrick

Wed May 01 2013, 04:01PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

how much was the sharp sensor? and where did you get it? I need several of those for my flying bot...

radhoo

Fri May 03 2013, 11:29AM

Registered Member #1938 Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 701

Hi Patrick,

I got them online, search for sharp infrared distance sensors.

I completed the Ultrasonic beacon , that the user needs to hold in his/her hands - quite comfortable, it is the size of a TV remote. It is also my first SMD PCB, and can say it was a lot of fun to build. Details , pics, eagle files, here:

And here are two demo videos, showing the robot outdoors:

With this , the project comes to an end, and my work is complete.

radhoo

Wed May 22 2013, 05:21PM

Registered Member #1938 Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 701

As I am a perfectionist with all that I build, I couldn't stay away and had to make this robot even better. So I did two things:
1) For the autonomous, human following software: I improved the ultrasonic detection algorithm, and the movement logic: Now the robot will follow its user more precisely, and the speed will vary with the detected signal: if the robots sees the user at a greater distance, will engage with a greater speed. If closer to the user, will proceed with smaller steps. The calculations are not linear, so I used some time to get the best formula. In the end I'm quite pleased, we can see some nice improvements when compared to previous two videos:

2) For the remote control software, where the user controls the robot using a phone, I had the idea to make the rover report its frontal sensor readings (that show the proximity in centimeters to any detected obstacle), to the smartphone. So the movement commands from phone to robot, and the sensor readings go the opposite way, from robot to phone. The Android software now allows the user to turn the lights on and off, and using the frontal distance sensor, I have drawn a red line showing the proximity to an obstacle. The robot can be controlled this way, without actually seeing what it is heading for, this radar will be enough to get a clean path. Here is another demo:

Complete story, and more build details have been posted here:

radhoo

Wed May 29 2013, 12:06PM

Registered Member #1938 Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 701

This project has been featured on Hack A Day:

This is my third project that gets there, after my capacitor discharge soldering tool (

) and my Gamma radiation monitoring station - uRADMonitor (

)

8)

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