Help with Slave Robot

[necxz]

We are planning on constructing a slave robot for our final year project. A Slave robot in a way that it will carry your baggage and follow you around.
We are having a dilemma in what transmitter to use. We are planning on putting two RFID receivers on the robot and the user will carry a RF transmitter.
So that when the user is turning to a different direction the robot will know where to turn and when. Is it feasible using RFID??

Also Our robot slave project will also have an anti-collision feature any advice on what sensor to use? we are planning to use sonar-sensor.

I would like to ask for your input regarding our project, it would really help us a lot.
Thank you in advance.

[madsci1016]

Is it feasible using RFID??

Not really. RFID won't read reliably in any direction, so it's not practical for localization.

Try infrared. Here's an Irobot Create project that uses the infrared beacons and wall receiver.

http://www.instructables.com/id/How-to-make-a-Robo-Bellhop/

[necxz]

ahh so RFID isn't feasible too bad.

What is the maximum range an IR can maintain?? its just that one of my seniors made a project using IR and its range is only .5 meters.
Our professor wants us to have a longer range lets say 1m or 2m is it possible?

Thank you for the link i will look at it.

Can blutooth be used?? so that we can use our cellphone as a transmitter its more convenient that way.

 

[madsci1016]

THIS IR beacon says it has an effective range of 15 feet, 5 meters.

Anything RF is not going to give you good directionality as easily as IR will.

[necxz]

Wow thank you very much. That beacon is amazing and it has a range of 5 meters.
We are now decided to use IR in our project.

and for our anti-collision we are going to use ultra sonic sensors.
any comment on that matter?

[Soeren]

Hi,

What is the maximum range an IR can maintain?? its just that one of my seniors made a project using IR and its range is only .5 meters.

That depends on the designer and the methods used - with lenses and/or parabolic mirrors 1 mile shouldn't be hard.

Most integrated IR receivers is spec'd at from 10m to 30m if used correctly.
Once again, it all depends on the designer/developer.

[madsci1016]

and for our anti-collision we are going to use ultra sonic sensors.
any comment on that matter?

Nope, sounds good. Won't interfere with the IR beacons.

[necxz]

@soeren
thank you for the reply. I guess we still have a lot of reading to do. Also we will be using the beacon indoors so sunlight wont be an interference. I have read somewhere that IR is greatly affected by sunlight that is why we need to experiment what frequency we will use am I correct??

@madsci1016
Ok thank you very much. Now its all about the availability of the materials
Which is better to use regarding our project a dc motor or a servo motor? which will be used as our main source of mobility.

It's just we are debating what to use I'm leaning towards the use of a dc motor but my group mates are in favor of servo motors.

@all
I'm really sorry if I ask many questions. Thank you very much. 

[Metal Slug 2]

It really depends on how large your slave robot is going to be.  You mentioned it needs to carry around baggage.  Assuming your baggage may be groceries, clothes or maybe even tools the weight might be anywhere from 0.5kg-15kg perhaps.  In this case, using common hobby servos for movement may not be feasible.  I would go for DC motors in this case, with a good gearbox.

[necxz]

@Metalslug2
Yes you are right. The slave robot should be able to carry around 10-15kg so it is decided then we will be using a dc motor.
thank you very much.

@all
I have a question regarding the pololu Beacon. Is it possible to program the Beacon to maintain a 1m distance from the transmitter?? so that the robot wont be able to bump the user.

[Soeren]

Hi,

@soeren
thank you for the reply. I guess we still have a lot of reading to do. Also we will be using the beacon indoors so sunlight wont be an interference. I have read somewhere that IR is greatly affected by sunlight that is why we need to experiment what frequency we will use am I correct??

Yes, sunlight is rich in IR and so is a lot of other light sources (energy saving lamps and fluorescent tubes are really bad in that respect) so you need to use a modulated signal (eg. a carrier wave) to get a weak signal out of a lot of noise and sunlight can still swamp the receiver out, so that it gets insensitive to the signals you want through.

Integrated receivers are great. They have built in Automatic Gain Control (AGC) and noise reduction (different types for different problems, so you need to select which type).
The frequency usually won't matter that much, as long as transmitter and receiver is matched.

Vishay have a broad range of receivers with different types of AGC circuits for different noise problems. If you take a look at eg. TSOP381nn or TSOP383nn (Where nn is the carrier frequency; 30, 33, 36, 38, 40 or 56 kHz), you'll see it's spec'd at 45m range typical. This is with zero ambient light, i.e. in a totally dark room.

You'll need to select the carrier frequency for the transmitter (beacon) and you need to select the AGC after both the kind of noise it will see and the type of "telegram" it will see from the beacon - a continuous wave (CW) will need one of the IRRX's made for security curtains, which has a constant gain in their "AGC" circuits (shouldn't really be called an AGC then) and that may be a problem if you have other interference and different angles and distance - as ever so often, the selection will be a compromise between opposite "interests".

[necxz]

@soeren
ahh ok I get it now. pololu Ir beacon now uses vishay's IR detector so it has a built in noise reduction. Our project robot will be used indoors so it somewhat lessens our problem about IR radiated from the sun.
Our target range is approximately 2-3m so I think it is sufficient.
Based from what I have read is it true that we will also need a range finder in order to maintain a distance of 1-1.5 meter between our receiver and transmitter? because our IR beacon can only provide us with directional information and in order to have a fix distance we will need a rangefinder.

[madsci1016]

Bases from what I have read is it true that we will also need a range finder in order to maintain a distance of 1-1.5 meter between our receiver and transmitter? because our IR beacon can only provide us with directional information and in order to have a fix distance we will need a rangefinder.

Correct.

[necxz]

@madsci
thank you

@all
what range finder do you suggest? what about Sharp GP2Y0A02YK0F Analog Distance Sensor 20-150cm.

[madsci1016]

You run the risk of interference by using an ir rangefinder with the ir beacon. The ultrasonic rangefinder was a better idea.

[necxz]

ahh yeah it will conflict with the beacons. is it alright to use the ultrasonic as a rangefinder and also as a sensor for anti-collision? I mean wont it conflict with each other if we used two ultrasonic one for avoiding obstacles and one as a range finder?

Sorry I ask so many question it's just that our topic has been recently approved and our papers is due a few weeks from now. I need to study the background of each sensor, indicated what materials are we going to use, how they work and how we will cascade each parts.  I'm also doing my research I'm really sorry for taking a lot of your time. Thank you very much.

[necxz]

ahh yeah it will conflict with the beacons. is it alright to use the ultrasonic as a rangefinder and also as a sensor for anti-collision? I mean wont it conflict with each other if we used two ultrasonic one for avoiding obstacles and one as a range finder?

Sorry I ask so many question it's just that our topic has been recently approved and our papers is due a few weeks from now. I need to study the background of each sensor, indicated what materials are we going to use, how they work and how we will cascade each parts.  I'm also doing my research I'm really sorry for taking a lot of your time. Thank you very much.

bump for my question

[madsci1016]

ahh yeah it will conflict with the beacons. is it alright to use the ultrasonic as a rangefinder and also as a sensor for anti-collision? I mean wont it conflict with each other if we used two ultrasonic one for avoiding obstacles and one as a range finder?

This is a tougher question and I can't answer a simple yes or no.

All the ultrasonic rangefinder does is tell you how far away an object is from it. What you do with the information is up to you.

So if you have two rangefinders pointing forward on your robot, how will they know whether the object in front of them is the person to follow or an obstacle in it's way?

You are going to tell us more about the project, so we can help you come up with a scheme to both follow someone and avoid obstacles. There's no quick answer here just based on sensor type. 

[necxz]

Ok thank you for the reply.

We are planning to make a Slave robot wherein a user will carry a transmitter and the robot with an embedded receiver will follow him around carrying his baggage(15-20kg).

An IR transmitter in the user side will broadcast and a receiver embedded in the robot will receive the broadcast in order to determine the location of the user.

A fixed distance of 1-1.5m should be maintained between the user and the machine. In order to prevent the machine from bumping the user.

The robot will also have Collision Avoidance in order to prevent it from bumping obstacles.

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We will be using 2 IR beacons (one as a transmitter and the other as a receiver)*

It will be powered by two DC motors (left-right) w/ motor control.* (not sure what motor)

Ultra-sonic sensors will be used for Collision avoidance.*

A sensor will also be used in order to maintain a fixed distance b/w the user and robot. * ( not sure what sensor)

The movement of the motors will be influenced by the output of the IR beacons and sensors.

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That is our Abstract. I'm not really sure if it's feasible. I want to ask for opinions about our project.
Please correct me if there is something wrong with our abstract.
Thank you again!

[madsci1016]

If the robot is always going to be following someone, wouldn't it be safe to assume the person would be leading it around obstacles?

Beyond that, I think your best bet would to be program your robot so it's always facing the beacon, and have a rangefinder pointing forward to maintain the distance. Then you could have two on either sides point out at an angle looking for obstacles.

[necxz]

Yes it would always be following a user but since there will be a fixed distance b/w them there is a slight chance that it might bump to something or someone.

That is what we have in mind that the robot should always face the beacon together with a range finder. What do you mean either sides? at left and right side of the robot? what if b/w the robot and the user suddenly a person blocks his path?

[madsci1016]

What do you mean either sides?

The red is the IR beacons and path, the blue is a forward looking ultrasonic that is used to maintain distance, and the yellow are side looking ultrasonics to avoid hitting someone.

what if b/w the robot and the user suddenly a person blocks his path?

There is no simple answer to this problem. Any range sensor won't be able to make out a obstacle versus the person it is suppose to be following.

The only thing I can think of, is if that IR beacon tells you it lost the other beacon completely. If the IR beacon lost signal, and there's something close in front of the robot, you can assume it's an obstacle and not the person to follow.

[fate]

What if the setup is like this..

Violet- IR beacon transmitter broadcasting signal specific frequency
Red - IR receivers, when the IR is detected at one of the receivers, the robot will orient its position as to make the center receiver receive the signal. serve as direction
Yellow - Ultrasonic Sensors, collision avoidance distance collision id defined as to not interfere with person in front, probably less than 0.5m  
Blue- Range finder way below or under the robot as to not interfere with line of sight transmission with the IR receivers.
Green - person holding the transmitter device

this is our idea of the project, pls comment on its drawbacks.. tnx

[necxz]

@madsci

thank you for the diagram and it might work. thank you very much. In your diagram the sonar on the sides won't interfere with our sonar acting as a rangefinder. can you suggest a dc motor that we could use? we saw a dc motor from parallax and it is equipped with a position sensor but it's too expensive it almost cost 300$ 

[madsci1016]

Sonar's may interfere with each other, but there's an easy way to fix that. Just only use 1 sonar at a time. THE EZ series of sonar have a pin you wire to the next sonar that allow them to time when they fire with each other. Or if you are controlling the timing with your microcontroller, just fire one after the previous one got a read.

I like the Lynxmotion motors more then the other motors I have tried. They seem to be better quality. They also sell wheels and chassis.

[fate]

what if we are going to use an IR range finder, with a different modulated frequency setting from the IR transceivers?? is it possible? thanks..

[Soeren]

Hi,

what if we are going to use an IR range finder, with a different modulated frequency setting from the IR transceivers?? is it possible? thanks..

Yes but... Unfortunately, so is the chance that the sum and/or difference frequencies will screw up the result and since you cannot change the frequency of the distance sensors, you are down to what frequencies that you can get the integrated IR-receivers in.

You may be in for a lot of experimenting, but if you get the frequency of the distance sensors first, you can at least calculate which frequencies are guaranteed to not work.

[madsci1016]

what if we are going to use an IR range finder, with a different modulated frequency setting from the IR transceivers?? is it possible? thanks..

Also, it doesn't buy you some magical way of know if the object in front of the robot is an obstacle or the person to follow. Obstacles and the person to follow will look the same to any type of distance sensor, IR or ultrasonic.

[voyager2]

Did anyone think of PIR sensors
http://www.sparkfun.com/commerce/product_info.php?products_id=8645

[Soeren]

Hi,

Did anyone think of PIR sensors

Yes, but you have to make a stable rotating base (with proper indexing) to be able to use it, as it sees changes and is blind to static ob- and subjects, whatever their body temperature.

A really keen programmer should be able to "see" the difference between a static object and a person moving with IR, US, RADAR, LASER or whatever, I just doubt that the OP is in that class though.