Robot that follows you - Page 1
Forum section: electronics / projects

author: ryuguy88
author_rank: Newbie
timestamp: March 25, 2017, 01:07:02 am
content: Hello everyone, I'm new to the forum (this is my first post, actually)Intro:I'm trying to build a small robot that will fit inside a hamster ball (or some similar-sized plastic sphere). The idea is that the robot will cause the sphere to roll around like the Morph Ball from the Metroid games. I'm still deciding on a mechanical design and wheel configuration, but once I get that working I'd like to add a mode that will let the ball follow me around the house in addition to remote control. This could be implemented as a phone app or some small handheld device that I build myself: I don't really care.My question is:How can I make the robot know which direction to go when it follows me? Do I need to include GPS, or is there some other way to do it?Thanks in advance for the help.

author: tpowell1830
author_rank: Frequent Contributor
timestamp: March 25, 2017, 01:12:26 am
content: Quote from: ryuguy88 on March 25, 2017, 01:07:02 amHi ryuguy88, welcome to the forum.I have no idea, but this might be a breadcrumb that you could follow.https://www.dronezon.com/drone-reviews/best-follow-me-gps-mode-drone-technology-reviewed/As you can see, the technology is not trivial.

author: xrunner
author_rank: Super Contributor
timestamp: March 25, 2017, 01:14:06 am
content: How is the Bot going to sense your presence in front of it sans you controlling it via a remote?IR - or what are you thinking?

author: ryuguy88
author_rank: Newbie
timestamp: March 25, 2017, 01:22:06 am
content: IR was my first thought as a control protocol, but Bluetooth is probably better, since I kind of want to paint the plastic sphere and the paint will probably block the IR. I wanted to leave some transparent/translucent plastic exposed for the aesthetic, but at best it would only be a ring around the "equator" about an inch wide.I had thought of IR as a way to sense my presence, though.

author: DaJMasta
author_rank: Super Contributor
timestamp: March 25, 2017, 04:03:00 am
content: I think I've seen an RC toy that is just a ball, may be a good reference for how to make the mechanics of it work well, or maybe just a platform for modding your own brain into.GPS following is simple enough, especially with the multitude of UAV controllers that can do that or something similar, but GPS is only good down to a dozen meters or so with a lock in ideal conditions, so it's probably not going to be accurate enough to follow you (unless it's following at a long distance).IR would be a simpler choice, but it will have issues outside and occasionally inside where there's a lot of light coming in (or with other IR devices). Radio would be an option, but you'd have a tough time getting enough distance between elements to really tell direction accurately without extremely precise timing equipment (not suitable for a little bot, really).I think a combination of sensors and some software to best-guess which ones are agreeing is the right approach, but I think you're going to want some sort of wearable beacon on you to be followed. It's going to be much easier to hone in on something that's emitting, and if you have maybe directionally-coded IR pulses and maybe an ultrasonic beam or two... you could probably get reasonable repeatability with the bot being able to follow you.Unless you're going extremely compute-heavy and doing something with a camera and recognition software, I think it's going to be very tough to try and do passively (without a beacon to home in on), and even with a beacon, relying on just one kind of sensor will leave you some circumstances where there is just no chance that it can follow you. Bluetooth or similar would probably be ideal to control - but maybe consider the UAV route and do it with wifi. Not that you'll need the data rate, but it gets you a bit of extra range and telemetry possibilities.

author: ryuguy88
author_rank: Newbie
timestamp: March 29, 2017, 02:03:36 am
content: I thought of something else.What if I had a few Bluetooth receivers shielded so each one could only receive signals from one direction (different for each receiver), then I broadcast some kind of "ping" and make the robot move in the same direction as the receiver that heard the ping?

author: DaJMasta
author_rank: Super Contributor
timestamp: March 29, 2017, 05:34:08 am
content: It's not a bad concept, but the execution may be tricky.For one, the bluetooth protocol may make it a little odd to do that - since something similar happens when broadcasting before pairing, but you only really have a data link when paired and can't generally have several links open on the same radio module.The other is the chance for reflections, if you get a surface that will reflect signals (bluetooth or otherwise) you may get a pretty strong signal on the wrong receiver just because it was at the right (wrong?) angle. Some of his can be alleviated if you're monitoring channel power on all radios and rejecting anything more than XX% below (since many reflections will be more attenuated than direct paths), but that could again be pretty tricky to execute.I don't have the experience to say for sure, but the equipment required to get accurate enough measurements or have enough radio connections open to pick probably does exist and can be used this way, but it may be too expensive, large, or power hungry to be a realistic solution.