Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronic Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

Relative positioning system ?

Status
Not open for further replies.

amith.srivatsa

Junior Member level 1
Joined
Aug 7, 2009
Messages
17
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Location
Germany
Activity points
1,496
Hello everyone,

I am working on building a relative position system for a robot using 433 MHz transcivers.

To measure the position of the robot,(................principle similar to GPS............) I intend to use an active device(433 Mhz transceiver) on the robot and 3 repeaters(433 Mhz transceivers) placed on for example trees, now, to measure the distance, I plan to use "data delay time" principle.

So, I should know "at what point of time" I transmitted my signal from the active device" & then "at what point of time" I received back my transmitted signal after modification by the repeaters. Using this data, I can find the relative position.

Do you know how to do this ? Also which transceiver modules have this feature ?

Many thanks in advance
Amit
 

kender

Advanced Member level 4
Joined
Jun 19, 2005
Messages
1,422
Helped
138
Reputation
276
Reaction score
38
Trophy points
1,328
Location
Stanford, SF Bay Peninsula, California, Earth, Sol
Activity points
9,970
Get a good text on GPS and follow it. BTW, you'll need at least 4 transmitters (just like you need 4 GPS satellites), because you will need to solve for time on the roving unit too. In some sense your setup is simpler than GPS: no Doppler and you know the PRN codes of your transmitters in advance.
 

FvM

Super Moderator
Staff member
Joined
Jan 22, 2008
Messages
47,956
Helped
14,145
Reputation
28,549
Reaction score
12,830
Trophy points
1,393
Location
Bochum, Germany
Activity points
278,208
GPS is using a sophisticated receiver design to achieve high time resolution with relative small signal bandwidth. I don't think, that any usual UHF transceiver is particularly suited for a similar application. Depends of course on the intended distance accuracy, that wasn't mentioned yet.

The most simple method is possibly a private DGPS setup: A pair of a fixed and a mobile GPS receiver and a radio link for the correction signal. Unfortunately, it only works in the open country.
 

amith.srivatsa

Junior Member level 1
Joined
Aug 7, 2009
Messages
17
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Location
Germany
Activity points
1,496
Yes, I forgot to mention an important parameter, the accuracy required is 1cm when the rover is not moving and about 300cms when the rover is moving.

Also, the LOS of the transceivers is for 500m.

I am a beginner, have no previous RF experience...For now, I am selecting a good 433MHz transceiver IC & a good CPLD/FPGA.

The plan is to implement the algorithm to calculate the distances between the "active device"(on the rover) and the repeaters(on trees) using CPLD/FPGA. Then, to make a PCB design with the Trancseiver & CPLD/FPGA. The calulated distances are then to be given to a microcontroller which calculates the relative position of the rover based on which it can navigate autonomously.

Will this work ? Suggestions wuold hell me a lot.
 

kender

Advanced Member level 4
Joined
Jun 19, 2005
Messages
1,422
Helped
138
Reputation
276
Reaction score
38
Trophy points
1,328
Location
Stanford, SF Bay Peninsula, California, Earth, Sol
Activity points
9,970
FvM said:
1 cm sounds illusional.
1cm was done at 50m with a well-controlled setup and in "vanilla" environment. The application was to determine positions of horse raiders on the race track (hippodrome). It can be done at 500m provided good environment.
 

FvM

Super Moderator
Staff member
Joined
Jan 22, 2008
Messages
47,956
Helped
14,145
Reputation
28,549
Reaction score
12,830
Trophy points
1,393
Location
Bochum, Germany
Activity points
278,208
I don't doubt, that it's possible with respective techniques. But not with a usual 433 MHz transceiver.

P.S.: Do you know, what kind of RF technology (carrier frequency, modulation, receiver design, antenna) was used to achieve the said 1 cm accuracy?
 

kender

Advanced Member level 4
Joined
Jun 19, 2005
Messages
1,422
Helped
138
Reputation
276
Reaction score
38
Trophy points
1,328
Location
Stanford, SF Bay Peninsula, California, Earth, Sol
Activity points
9,970
FvM said:
Do you know, what kind of RF technology (carrier frequency, modulation, receiver design, antenna) was used to achieve the said 1 cm accuracy?
It was a reverse GPS system: the rovers were transmitting and "satellites" were receiving. Frequency: 1.5GHz. Same frequency as GPS, however, the transmitter was orders and orders of magnitude closer to the receiver, so the interference from celestial GPS signal was negligible. Antenna on the rover was a patch, antenna on the receiver was either patch or helix. Modulation was BPSK.
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top