I'd like to build a little "pet" robot on wheels that follows me around the house. I might have some kind of radio transmitter in my pocket. I thought about it for a while but I can't think of any sensors that can make it recognize where I am. Do you guys have a good idea?
PIR sensors are what are usually used for detecting/tracking warm-bodied lifeforms.
Do a search at http://images.google.com/ for "PIR Sensors", and you will see tons of
them as used in robots.
About the first robot to use this idea was Genghis, but you can probably get by with
fewer sensors.
You'd be surprised how often this question comes up here, and how difficult it is to achieve in the real world.
Simple PIRs detect movement, but singly give no indication of direction.
As noted, Genghis used many PIRs, but fewer will probably work. Wide-beams for
detection, narrow-beams for tracking. That solves one problem, but will have
other issues if used in a crowded location.
I'm only willing to share ideas if you promise that you're making the waffle bot from Harold and Kumar.
On a less serious note, have you thought about RFID? I'm not sure if that would do the trick but maybe it could follow around an RFID chip or something that was in your back pocket.
They use ultrasonic sensors which are better for short-distance detection and more directional than radio.
But can't discriminate between following you or some pretty chick that walks by. Well, I'd follow her, too.
On a less serious note, have you thought about RFID? I'm not sure if that would do the trick but maybe it could follow around an RFID chip or something that was in your back pocket.
He said he wanted the robot to follow him, not be sniffing his butt all the time. RFID doesn't have a useful enough range, except for very expensive versions, for this purpose.
How do dogs follow a scent, presumably the scent lingers on physical objects along the path?
RFID isn't directional enough either
Could the robot have a pair of ears able to detect ultrasound that would permit the robot to determine the direction of an ultasonic source carried by the person? The spacing of the ears would need have to be realistic but match the processing capability of the Arduino.
Otherwise the person could wear IR light sources, or feducials reflective of a light emitted by the robot.
Some of these would need to be visible to the robot whatever the person's orientation to the robot.
They use ultrasonic sensors which are better for short-distance detection and more directional than radio.
But can't discriminate between following you or some pretty chick that walks by. Well, I'd follow her, too.
If you had looked at the project you would have seen that the person being followed had a radio-triggered ultrasonic sender and the luggage had two ultrasonic receivers and a radio sender. The luggage radio commands the transponder on the human to send out a ping. The two receivers time the transit of the ping. This gives distance to the transponder and relative direction, enough to maintain a constant follow distance.
johnwasser's luggage link is pretty good but it is over 20min long. Fast forward 18min to the final product then go back if interested.
The ultrasonic "ears" obviously work.
Pauly's library chairs seem to only be a concept so there is no technical solution there. Having robot chairs follow you round a library does not sound very green. However I found the idea of masses of chairs following the "manager" then forming themselves into a seating plan for an audience quite amusing - I would love to see it.
Wow, I did't expext so many replies in this short time. Thank you!
And especially thank you johnwasser, awesome link! This is pretty much what I had in mind, eventhough I didn't think of splitting a ultrasonic unit. Very good idea. And it looks fun to build, I'm gonna give it a try.
I built a follow me robot a while back, after a night out on the town, I can't remember the software, or even the firmware, but it follows me faithfully from office to lab, even to the shops, and for the life of me I can't remember what batteries I used - but they are still going after 6 years !
I am building a robot with the same goals - follow a person around.
Independently of this thread or any of the links in it, I decided to use 2 ultrasonic mics on the robot and an ultrasonic driver worn by the person - great minds think alike! The mics will be mounted on a rotating head to allow the robot to re-acquire the signal even if the robot is not facing in the right direction.
For obstacle avoidance I am using 3 ultrasonic sensor arrays (left, forward, right).
Currently I have an obstacle avoidance sketch that has no following capability to prove out talking with the obstacle sensors and controlling the drive motors. I need to build a mic amplifying circuit and work out the math to determine the beacon direction based on the mic inputs.