Society of Robots - Robot Forum
Mechanics and Construction => Mechanics and Construction => Topic started by: necxz on August 31, 2010, 07:37:55 PM
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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.
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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/ (http://www.instructables.com/id/How-to-make-a-Robo-Bellhop/)
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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.
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THIS IR beacon (http://www.pololu.com/catalog/product/701) 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.
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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?
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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.
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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.
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@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 :D
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.
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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.
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@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.
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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".
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@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.
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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.
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@madsci
thank you :D
@all
what range finder do you suggest? what about Sharp GP2Y0A02YK0F Analog Distance Sensor 20-150cm.
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You run the risk of interference by using an ir rangefinder with the ir beacon. The ultrasonic rangefinder was a better idea.
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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.
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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
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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.
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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!
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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.
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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?
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What do you mean either sides?
(http://www.billporter.info/wp-content/uploads//2010/09/example.png)
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.
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(http://i263.photobucket.com/albums/ii148/mac0i0i0iiii/proposedIR.jpg)
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
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@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$ :(
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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 (http://www.lynxmotion.com/c-11-spur-gear-motors.aspx) more then the other motors I have tried. They seem to be better quality. They also sell wheels and chassis.
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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.. :)
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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.
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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.
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Did anyone think of PIR sensors :P
http://www.sparkfun.com/commerce/product_info.php?products_id=8645 (http://www.sparkfun.com/commerce/product_info.php?products_id=8645)
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Hi,
Did anyone think of PIR sensors :P
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.
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thanks a lot guys.. another alternative we're testing right now is using the same IR transceivers for direction to know the distance of the user. Is it possible that we take out the received IR signal and assume distance through its RSSI?? i mean we won't need really precise distance from the user, all we need is at least to have a 0.7-1meter allowance for the user to freely move. Is it possible to use the RSSI even on the moment when the robot is properly oriented at the user's back as distance detection ?? super thanks.. im also one of the pursuers of this project.. i guess we'll be bugging you guys for the whole year .. :))
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RSSI?
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Its seems it will be really hard to implement too many sensors. I have read many studies and most of you are suggesting that it is really hard. What if we remove the range finder instead. From what I've read if we only embed an anti-collision sensor(ultrasonic) and an IR beacon they will work without interfering with each other and thus solving our problem. Am i correct?
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Received signal strength indication - we can determine distance of an object through the strength of the return signal.. like for our case, IR.. the attenuation of signal by the distance it traveled assuming no other interference.. this was the suggestion of our adviser. wherein the returned modulated frequency will be used to assume distance.. that the robot will stop if the calculated distance(considering noise here) is like for example less than 1m.
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Hi,
Received signal strength indication -
Aha, it helps writing it out in full the firsst time when usin self invented acronyms.
we can determine distance of an object through the strength of the return signal.. like for our case, IR.. the attenuation of signal by the distance it traveled assuming no other interference.. this was the suggestion of our adviser. wherein the returned modulated frequency will be used to assume distance.. that the robot will stop if the calculated distance(considering noise here) is like for example less than 1m.
That will be very variable depending on the target. If you get some useable results wearing blue jeans, don't wear white or black when you have to demonstrate it, or you'll be disappointed with your grades.
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Aha, it helps writing it out in full the firsst time when usin self invented acronyms.
http://en.wikipedia.org/wiki/Received_signal_strength_indication (http://en.wikipedia.org/wiki/Received_signal_strength_indication)
And, since you will no doubt mock wikipedia
http://www.google.com/search?q=RSSI (http://www.google.com/search?q=RSSI)
http://acronyms.thefreedictionary.com/RSSI (http://acronyms.thefreedictionary.com/RSSI)
(http://www.x-lin.com.tw/img/xpro-5000a_03.jpg)
So... not so self invented. Either that or 'fate' help write the indicator panels on all the radios with RSSI indicators I have ever seen. :P :P
I think you guys are way over complicating this problem. You had a good plan with using the IR beacon for bearing, a ultrasonic for following distance and two side ultrasonics for avoidance, and some good programming to determine if it's an obstacle or target in front of you.
Heck, you can even just have bumpers that would feel for obstacles and try to go around.
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So... not so self invented. Either that or 'fate' help write the indicator panels on all the radios with RSSI indicators I have ever seen. :P :P
Apparently not, just obscure enough that it ought to have been spelled out, so as not to waste peoples time Gogling stuff.
Glad you enjoyed your time spend searching and your "field day" ;)
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Apparently not, just obscure enough that it ought to have been spelled out, so as not to waste peoples time Gogling stuff.
Glad you enjoyed your time spend searching and your "field day" ;)
Miss my chance to poke fun on our resident dinosaur?
It's not obscure, in fact it's written on the two radios that happen to be on my bench right now. It would have been nice not to have to spend 30 seconds searching, but since you didn't bother someone had too. I'll be sure to spell out all basic engineering acronyms in my posts for you from now on. ;)
(This is in jest, fyi)
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hey madsci and soeren.. pls dont make this such a big fuss.. i'm really glad your both helping us.. it really means a lot if you must know.. :)we're just discovering other options to make our project worth defending during our paper presentation and you both did really helped a lot. thanks.. neczx and i are going crazy right now, i do get both of your points though.. that is not to make our project complex when it could have been easy.. (tap on my head)
we've decided to include in our limitations that the robot wouldnt be able to detect if its the user or an obstacle is up in front. it will avoid whatever it is as long as it gets near the robot when it is moving forward. meaning it is not the user. then we could include a park mode in the user's transceiver so that he/she can get near the vehicle. did we decide right?? thanks guys, we are planning to include you both and this site to our acknowledgements.. :)
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Don't worry fate, Soeren is a wise old man and I had to get my jab in when I could, as the opportunities come few and far between.
the robot wouldnt be able to detect if its the user or an obstacle is up in front
I wouldn't say that is such definite terms, because like i said before, you could get fancy with your code such that if there's an object in front and the IR beacon is being received, object = user. If there's an object in front and beacon isn't being received, object = obstacle.
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Don't worry fate, Soeren is a wise old man and I had to get my jab in when I could, as the opportunities come few and far between.
:D
the robot wouldnt be able to detect if its the user or an obstacle is up in front
I wouldn't say that is such definite terms, because like i said before, you could get fancy with your code such that if there's an object in front and the IR beacon is being received, object = user. If there's an object in front and beacon isn't being received, object = obstacle.
thanks.. got that..
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What do you mean either sides?
(http://www.billporter.info/wp-content/uploads//2010/09/example.png)
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.
Instead of using IR Rangefinders, you could use an IR emitter on the master (the person who the robot should follow) and a IR camera on the slave. The Nintendo Wii Remote is a bluetooth enabled IR camera. Only drawback is you would need to interface through a computer, but its an option that you could try readily. See this example of someone using the Wiimote to make a multitouch whiteboard:
Low-Cost Multi-touch Whiteboard using the Wiimote (http://www.youtube.com/watch?v=5s5EvhHy7eQ#)
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Instead of using IR Rangefinders, you could use an IR emitter on the master (the person who the robot should follow) and a IR camera on the slave.
You are comparing apple to oranges here. First, they are using an IR beacon for bearing, not an IR rangefinder. Second, the Wii camera will be ok for telling you the bearing to the IR, but will be tricky to get distance. It would require two IR sources on the person, and a computer algorithm to measure the distance between the two. Even then, it may not be as accurate as an IR rangefinder.
The Wii remote is good for many things, but way too impractical for this.
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Instead of using IR Rangefinders, you could use an IR emitter on the master (the person who the robot should follow) and a IR camera on the slave.
actually, we have thought about wiimote, but had given up the idea. its way too complex for our bearing where we could could use a simpler device, quite impractical.
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are IR really used in line-of-sight communications only? that blocking the signal could mean a signal loss? it's quite a puzzle to me where in this video, obstacles are present (such as the sofa) and still the beacons were able to detect each other. I mean did i miss something here?
Beacon Robot (http://www.youtube.com/watch?v=TqskQru6pa8#ws)
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are IR really used in line-of-sight communications only? that blocking the signal could mean a signal loss? it's quite a puzzle to me where in this video, obstacles are present (such as the sofa) and still the beacons were able to detect each other. I mean did i miss something here?
Beacon Robot (http://www.youtube.com/watch?v=TqskQru6pa8#ws)
It is mostly line of sight, and won't go through a couch. I'd have to know more about that robot to answer your question. I have a feeling it just avoid obstacles until it gets a signal from the beacon.
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You are comparing apple to oranges here. First, they are using an IR beacon for bearing, not an IR rangefinder.
Sorry it was late when I made the post, and I completely misread that.
And yes the wii remote would be impractical, I meant it more as an informational/proof of concept idea.