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High Frequency beacon

Hi guys

I'm working on a lawn mower. I'd like it to precisely know its position in order  to optimise its travel.  As it is working outside and on a more than 500 square meters, the IR beacon (needs to remain in sight) , the GPS(not sufficient precision) won't fi my needs. Any idea like HF beacon ? 

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In fact a navigation system prefers first the GPS and next come multiple DME and next only  mutiple VOR. With the DME you get a circle from each DME station, the position is then at the intersection. When using the vor you get only a vector to the station, it seems easier but it's not.

I don't have any DME on my mower : the DME is an UHF device that  enables the aircraft to its distance to the beacon. most DME are collacated with a VOR which is a VHF device.

The ground base DME station is able to handle 100 aircrafts up to a range of around 200 Nm(Nautical Miles)

US stands for Ultra Sonic and IR for Infra Red 

 

I see. I remember reading about the DME when studying the principles of VOR. I did not pay attention because I always figured I would use multiple VORs and triangulate.

 

As a pilot I should have thought about it before ! In fact the distance measuring equipment is a DME but the precision won't be enough as well. I'm thinking back to a I2C compass, US sensors and an "under ground" wire. So far I'm using only the wire and bumpers.

Please update me on these acronyms: DME, US sensor.

I Get DME = distance measuring equipmen, but is that something that's already on your mower, or already on your airplane?

(I am not a pilot.)

I am thinking VOR. Ever played with (a) flightsimulator? Won't be easy though.

Building a VOR station requires fancy electronics and/or a rotating directional aerial. For locational info you need two or three of them around the area. The geometry involved on your vehicle is probably too complex for a micro controller type brain.

I think I'm wrong as the time for the HF pulse would be too short to permit it's simple computation : for 30m it would be only 0.1 micro second ! toos short formy PIC. Got to revert back to IR or US

500 sq m I think it's too large for a positionning system based on IR, that 's why I'm thinkink of a radio  system.

I was thinking of the mower sending a message " Clear to send beacon 1" then waiting for it's response in order to calculate the distance between the mower and beacon1 and so on with beacon 2 and 3. At the end with these 3 circles, the mower could be able to compute it's position. Not easy at first but has anyone ever compute a distance with such a system ?

I think the GPS precision won't be enough as the mower requested precision has to be around 5 sq cm. The many best solution would be a kind of differential GPS with a beacon sending the error to the mower. not easier I think. But once more is there any one who has ever test this kind of solution ?

 

 

500sq meters with IR? That will need to be intensely bright. When I first read this post I thought it said "High Frequency Bacon"

That is a lot of ground to cover! Especialy if you say you need better precision than the GPS can offer.

You could try to use a radio transmitter like the ones used for RC cars and planes. But then you'd still need to determine direction pretty accurately. If you could get a couple of those hooked up with a directional antenna and have the antenna on the beacon spin around broadcasting pulse signals; each signal telling the direction the beacon is pointed at at the current pulse.

The mower (hopefully) receives only the signals that are directed straight at it. Use two or three of those beacons and you can dertermine your position quite well. Each beacon telling the mower its bearing relative to the beacon.

Maybe this can be done the other way around by having a directional receiver on the bot spinning around and the beacons broadcasting their ID over the field. That way the bot gets a bearing on a couple of beacons and calculate its position.

I can't think of any inexpensive easy solution.

Some vacuum cleaning robots and lawnmower robots  use IR or laser fences. You just put them on the ground where you dont what the bot to go. Cross the IR or laser beam and either the fence signals to the mower it has crossed the line or the robot itself detects the fence.