Best way to make the receiver follow the transmitter. Should UWB be used or rf?

I want a trolley to follow the transmitter which is placed with the person. What should i use a rf or UWB 'DW1000' or some other module?
The wheels should be able to follow in the direction where the transmitter is and brakes need to applied when the trolley is at a specific distance.
The speed should increase if the distance is large and slow if the distance is less.
Any Help regarding as how to do it will be also appreciated :slight_smile:

Narrow beam, Ultra sonic, or better, I.R. for direction and ultrasonic for distance., Sensor/detector(s). RF is a waste of time, unless you already know a lot about what you are doing (and you don't, or, you would not be asking here).

Single sensor on a Servo Sweep mounting. sync steering to servo position.

Multiple sensors positioned in a ten to twenty degree spread. measure intensity received on all sensors, pick sensor with strongest signal, scan sensors immediately next to strongest signal for next strongest signal level, sync steering to position indicated, rescan.

What did your instructor suggest/Prefer?

Adding a GPS to both platforms can help. They could exchange locations, which could augment other sensors. Also, it may be a good way to confirm that they are out of range of the other sensors.

While the absolute GPS error can be 3 to 30m (or more, depending on satellite reception), the relative error is much less. That is, two GPS locations may both be off by 11m from the actual map location, but the calculated distance between them may have an error of only 1m, for example. This is a common way to increase GPS accuracy. (See also this.)

I have written a GPS library that is very accurate in its distance and bearing calculations: NeoGPS. Other GPS libraries have trouble with small separations, because of floating-point errors. NeoGPS is smaller and faster than other libraries, and it can be configured to parse only the messages and fields that you really need, saving even more space. NMEAaverage.ino shows how to use the distance and bearing functions.

Cheers,
/dev

123Splat:
Narrow beam, Ultra sonic, or better, I.R. for direction and ultrasonic for distance., Sensor/detector(s). RF is a waste of time, unless you already know a lot about what you are doing (and you don't, or, you would not be asking here).

Single sensor on a Servo Sweep mounting. sync steering to servo position.

Multiple sensors positioned in a ten to twenty degree spread. measure intensity received on all sensors, pick sensor with strongest signal, scan sensors immediately next to strongest signal for next strongest signal level, sync steering to position indicated, rescan.

What did your instructor suggest/Prefer?

How much will it cost approximately?
rf or gps will be preferred he said, but narrow beam will work too.
And sensors that are to be placed on the trolley, how much will that cost?
Thank You for Quick response :slight_smile:

/dev:
Adding a GPS to both platforms can help. They could exchange locations, which could augment other sensors. Also, it may be a good way to confirm that they are out of range of the other sensors.

While the absolute GPS error can be 3 to 30m (or more, depending on satellite reception), the relative error is much less. That is, two GPS locations may both be off by 11m from the actual map location, but the calculated distance between them may have an error of only 1m, for example. This is a common way to increase GPS accuracy. (See also this.)

I have written a GPS library that is very accurate in its distance and bearing calculations: NeoGPS. Other GPS libraries have trouble with small separations, because of floating-point errors. NeoGPS is smaller and faster than other libraries, and it can be configured to parse only the messages and fields that you really need, saving even more space. NMEAaverage.ino shows how to use the distance and bearing functions.

Cheers,
/dev

My Range will vary from 30 cm to 5 m, so will GPS be able to track down the distance accurately as to not hit the person who is carrying the transmitter?
I actually started this idea as gps based but due to accuracy reasons i switched to other sensors..
Also, by using GPS how will the receiver know in which direction to move?
Thank You for quick Response :slight_smile:

chinmaya_03:
will GPS be able to track down the distance accurately as to not hit the person who is carrying the transmitter?

As I said:

Adding a GPS to both platforms... could augment other sensors. the calculated distance between them may have an error of only 1m

You can't use GPS alone when the distance is less than 1m, or you could run into the person. You'll have to use other sensors if you want to get closer than 1m. Personally, I would not want the trolley within 30cm, because my stride length is longer than that. Does this person have to shuffle?

shuffle.gif
:slight_smile:

by using GPS how will the receiver know in which direction to move?

It's easy to calculate the bearing from one location to another with the NeoGPS library:

      float bearing = trolleyLoc.BearingTo( personLoc );

If you are going fast enough to have a good GPS speed value (> 3kph ?), you would know the trolley's direction of travel. Then you could determine how to travel toward the person as an offset from the current direction.

When travelling less than 3kph, you would also need a magnetic compass module that tells you the current orientation of your trolley. Using the trolley's orientation and the bearing to the person, you can determine which direction the trolley should move.

Or, you could let it start moving to determine its direction of travel. That could look a little funny, though. :smiley: Magnetic compass modules are the best solution, and they're very inexpensive.

Regardless, you will need other sensors. GPS is very good if the trolley gets out of range of the other sensors (> 5m). GPS is not very good when the trolley is closer than 2m.

Cheers,
/dev

/dev:
As I said:
You can't use GPS alone when the distance is less than 1m, or you could run into the person. You'll have to use other sensors if you want to get closer than 1m. Personally, I would not want the trolley within 30cm, because my stride length is longer than that. Does this person have to shuffle?

No Shuffling :smiley: ,the person is walking in the supermarket so I guess if I place the module in the middle of the trolley than 1m will be pretty good.

/dev:
If you are going fast enough to have a good GPS speed value (> 3kph ?), you would know the trolley's direction of travel. Then you could determine how to travel toward the person as an offset from the current direction.

The person is walking straight sometimes, stopping to place some products in the trolley .. and then continue for a little distance then again stop..
So the speed will vary a lot.

/dev:
When travelling less than 3kph, you would also need a magnetic compass module that tells you the current orientation of your trolley. Using the trolley's orientation and the bearing to the person, you can determine which direction the trolley should move.

Should I use an accelerometer for distance less than 3m? And is there any way to use rf? Because I want the project to be under 50$, thats the maximum budget.
Also magnetic compass is around 20$, and a rf transmitter is around 3$.

/dev:
Or, you could let it start moving to determine its direction of travel. That could look a little funny, though. :smiley: Magnetic compass modules are the best solution, and they're very inexpensive.
Regardless, you will need other sensors. GPS is very good if the trolley gets out of range of the other sensors (> 5m). GPS is not very good when the trolley is closer than 2m.

Or as 123splat suggested should i use ultrasonic to find distance and servo sweep to find direction?
Your suggestions?
One more thing..
http://www.dx.com/p/ultrasonic-distance-measuring-transducer-module-kit-w-9g-servo-black-392018?tc=INR&gclid=COyN7cSstc8CFQomvQod01QGdA#.V-1wbCT8bhQ
This device can take 15 degrees max so 4 sensors can be used...? What do you suggest.
Regards
Chinmaya

A magnetic compass over a concrete floor full of rebar! I don't think so.

Paul

Inside a grocery story? GPS reception would be very dependent on the building. Metal roof? Other floors above? No GPS.

I say put a leash on the shopper, attached to a string length encoder (distance), mounted on a rotary encoder (bearing). :smiley:

BTW, ultrasonic may decide to follow some other shopper walking by...

There are so many amusing ways this can go wrong. Sounds like fun, though.

Good luck!
/dev

Something to consider:

How do you make it follow your path exactly (or very closely) so it doesn't cut a corner and take a out a center-of-aisle display table that you nimbly step around without thinking about?

No GPS then.
BTW i am doing this for a project, and have to show it in university exhibition for 20 Marks.
Wireless preferably rf or ultrasonic...
which one would be more economical and easy to implement?
Aaand there will be no other shoppers :wink:

CrossRoads:
Something to consider:

How do you make it follow your path exactly (or very closely) so it doesn't cut a corner and take a out a center-of-aisle display table that you nimbly step around without thinking about?

:o :o
Then other sensors to detect a object can be placed and the trolley can make a way around...
But in this i simply want the receiver(trolley) to follow the transmiter, figuring out the distance and direction and use some Digital Logic :smiley:
Regards
Chinmaya

Remember Hansel and Gretel? They dropped cookie crumbs to mark their trail. You could do something similar with bits of aluminum foil and have the trolley look for the reflections!

Paul

Predetermined path through the store for the cart/trolley/bot to follow, marked with I.R. paint. bot uses I.R. illumination and sensors to follow path ( or substitute magnetic rubber strip and Hall Effect sensors, but there goes your budget)(see line following robot projects). use ultra-sonic distance sensors for obstacle avoidance, and distance from shopper detection ( stop when obstacle within set range, like 2-3 meters). and near field RFID to identify shopper within range.

Gonna cost ya a little more than $50, even before you consider motor drive and power supply to support shopping cart sized max load......

I am now using a rf(transmitter and receiver) to transmit the data from the accelerometer placed in transmitter.
Arduino will be used at receiver(trolley) to decode the displacement in x and y axis that will be sent by the rf, then a single servo motor is used for change in direction and behind that two dc motors(small size) are placed which will work when there is a displacement in y axis.
Any suggestions?
Thanks in advance!

The rf will be reflected from all the complex surfaces in a supermarket and so will not give you a reliable direction - and even so, how would you detect the direction? by scanning with a very directional receive antenna ? Or by using phased arrays? And what if there are absorbtive obstacles?

Motor manufacturers have spent many millions trying to get collision avoidance radar to work at 77GHz - it isn't easy or cheap.

Not for 50$, I'm afraid

regards

Allan.

Actually , it may not be quite impossible at least if there's not too metal about.

If you used a very low frequency - eg 500kHz, and a 'huff-duff' type antenna - 2 orthogonal loops and an omni - you might get somewhere.

It'd be quite illegal in most countries, of course..

regards
Allan

It might not be possible in a supermarket but for showcasing of project i have to move the trolley in an empty hall way!
The transmitter will have a accelerometer, and as soon as there is a movement in accelerometer, the same will be transmitted through rf to the trolley where the arduino will figure out the displacement in both the axis and the wheels will be configured according to the output we will get from arduino.
the components i am using :-
Transmitter and Receiver
Accelerometer
Arduino
Car chasis
Back Wheels and motors
Servo Motor
Thanks for Help.
Regards
Chinmaya

"Published on Mar 18, 2012
Tired of lugging around a bunch of stuff at airports, Ben builds Robot Luggage to help lighten the load with the help of Jesse Robinson!"

This is awesome!! Thanks for showing this!!!
Can you help in figuring out the code and the components required?
Thank You again!
Regards
Chinmaya