Best method for identifying direction of master

Help & Support Robot Parts
1

Hi, I’m relatively new to robotics, but am fairly tech oriented.

To sum up my situation, my body is a pickle-bucket with motors on the sides on the bottom,
and a change-able head (currently a plastic dome bowl) for a head on top.

The hardware is a Raspberry Pi and a PicAxe 28 with the corresponding board,
connected to each other through I2C.
The Pixaxe is currently using 4 output rows, all 4 motor jacks, and one analog in for a SHARP.

What I need to do is figure out a way to make the robot know what direction I’m in,
relatively cheaply and accurate.

I currently have a USB and WiFi dongle installed, and was going to use the Bluetooth for this.
I wanted put make an aluminum cone around it to make a directional antenna,
to move it left and right, but the RSSI signal I get still jumped +/-2
(possibly because WiFi which runs on the same frequency)
which about the same difference of if it was looking at me vs 45 degrees away at about 6ft.

I considered using an infrared beacon on me, with a sensor in the head,
this one specifically: robotshop.com/dagu-compound-infrared-sensor-4.html

But I’m concerned of if it’s best idea in a crowd.
I was thinking of having it follow my last known location,
also stopping if someone’s in front of it, when it loses line of site to my beacon.
However, I’d also prefer it to see me outside in the sun: would a 940nm LED be overpowered?

Lastly, I was considering using 2 RFID chip sensors (unless only 1 may be needed?)
I was looking at one “5dBi PCB UHF RFID 902-928 Mhz”, but what would it’s typical range be?
I know UHF can bounce off walls but be obstructed by people,
so I plan to use that for my benefit, if it’s the best option.

So these are just some of my own thoughts,
but I’m looking for any input of how I can get it to find my direction to follow me,
for a pretty low cost, because we only have about $50 or so playing money,
to last us for the next two weeks, and I may actually be off on that.

And input and experience is appreciated!

2

Making a robot follow you like that can be a difficult project, but it seems you’re on a the right track. Using an infrared LED can work, depending on the quantity of sun. If one LED is overpowered, perhaps making a cluster can help.

I’m not familiar with doing triangulation using RFID sensors, so I don’t know how well that would work. You could also do triangulation using ultrasonic sensors: the CaddyTrek uses a similar system where their remote has a ultrasonic emitter and the robot has two ultrasonic receivers and a triangulation algorithm determines the location (distance and direction) of the emitter relative to the robot.

You can see it a bit in this video:

I imagine in this situation that the emitter is directional and the robot cannot find it if it is pointing away from its sensors…

The tricky part however is completing the project within the $50 budget: not much room for experimentation with different parts.

To do the ultrasonic triangulation, we would recommend trying the following sets of sensors:

For each of the sets, you should be able to use one as your emitter by regularly sending the sensor a trigger pulse (and ignoring the response) and use the other two as the receivers by regularly measuring the received pulses (without having to send trigger pulses). These sensors aren’t exactly made to function this way, so it would require experimentation to determine how well they behave like this.

We hope this helps and thanks for choosing RobotShop,