Author Topic: question about the material for my robot  (Read 1763 times)

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Offline Sarah21Topic starter

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question about the material for my robot
« on: February 07, 2011, 05:15:14 AM »
Hi,


I've been working on my robot, that can be used for outdoor and indoor applications.

I chose Aluminum as a material for the robot body, since it is light, easy to be formed and strong at the same time. But in my place, most of the time it is hot outside, so now am afraid that the robot my heat up and got damaged... any ideas how to overcome this problem?
i was thinking that maybe i can add a layer of material or paint that may help cooling down. I searched and I didn't find something similar, any ideas people???

Another thing, I am using a camera for the robot, and in order to get a vision which as stable as possible in the outdoor terrain, I decided to use sorbothane as a layer under my camera to absorb shocks. This material has some great characteristics. What do think of this? Do u have any other thoughts maybe??

thank you all.
 

Offline Soeren

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Re: question about the material for my robot
« Reply #1 on: February 07, 2011, 01:01:59 PM »
Hi,

I chose Aluminum as a material for the robot body, since it is light, easy to be formed and strong at the same time. But in my place, most of the time it is hot outside, so now am afraid that the robot my heat up and got damaged... any ideas how to overcome this problem?
Unless you live in #666, I seriously doubt that it should be too hot for aluminum  ;D

How hot exactly does it get (in C or F)?
If anything, it would be the electronics that might get too hot, but there's always a way.


i was thinking that maybe i can add a layer of material or paint that may help cooling down. I searched and I didn't find something similar, any ideas people???
Short of a layer of ice, if you add something it should be an isolating material, like something foamy (i.e. with trapped air) and some mirror finish on the outside to deflect sun rays (like a survival blanket).
However, this would trap the heat generated by the 'bot and that would be a bad thing.
I do think you exaggerate the heat problem though.


Another thing, I am using a camera for the robot, and in order to get a vision which as stable as possible in the outdoor terrain, I decided to use sorbothane as a layer under my camera to absorb shocks. This material has some great characteristics. What do think of this? Do u have any other thoughts maybe??
I have no personal experience with Sorbothane, but whatever you use, you can not get a perfectly stable picture from a moving 'bot.
Best solution I can think of, is a balanced counterweight, like one of the "poor mans steadycams", perhaps dampened in some way.

Whenever you add any kind of elastic mounting, you need some dampener as well, like a car where the movements of the springs is kept in check by the shock absorbers.

How pronounced is the unsteadiness as it is?
Regards,
Sren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline nickc

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Re: question about the material for my robot
« Reply #2 on: February 07, 2011, 03:06:59 PM »
I've used sorbothane on some projects at work. It's used in things like the palm of bike gloves to absorb vibration. It works well for small shocks but probably not enough to make much difference in the image quality and wouldn't do much if added between the camera and the bot.  When designing suspension, you have to consider the inertia of each of the items you are connecting.  If you think of the camera sitting in space and the robot hitting a bump and moving up.  The tiny mass of the camera would not be enough to keep it from moving up with the robot not matter what the suspension. If you are adding suspension, you need to do between the axles and body of the robot.
here's a link to a simple steadicam type mount for an iphone.  It might work for your bot-cam.  It looks like there are a couple of other links other camera mounts in the article.

http://lifehacker.com/#!5595556/build-a-diy-iphone-steadicam-for-smooth-iphone-video

If you insulate your robot don't forget you are trapping all the heat from the motors and electronics in.  You might have to add vents or a fan if you are using big motors.  If you have any extra I/O you could add a temperature sensor to your controller and test your insulation ideas.

Offline Sarah21Topic starter

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Re: question about the material for my robot
« Reply #3 on: February 09, 2011, 02:01:33 AM »
Thank you Soren for your reply..


Quote
Unless you live in #666, I seriously doubt that it should be too hot for aluminum  ;D

How hot exactly does it get (in C or F)?
If anything, it would be the electronics that might get too hot, but there's always a way.

Well, my outdoor temperature may reach to 55C in summer time, it is a desert.
so, with that temperature, and the vertical sun rays, i think it is possible for the aluminum to get heated right?.

Quote
Short of a layer of ice, if you add something it should be an isolating material, like something foamy (i.e. with trapped air) and some mirror finish on the outside to deflect sun rays (like a survival blanket).
However, this would trap the heat generated by the 'bot and that would be a bad thing.
I do think you exaggerate the heat problem though.

Will the heat generated by the robot be that much?
I did some digging after reading this reply and I read about the aluminum foam and about its different application in aerospace, medicine etc. Is it a good solutions though? 

and for the fact that it will trap the heat generated from the robot, will drilling some tiny holes in The 'bot body help in ventelating?

Quote
Whenever you add any kind of elastic mounting, you need some dampener as well, like a car where the movements of the springs is kept in check by the shock absorbers.

How pronounced is the unsteadiness as it is?

I don't know the amount of unsteadiness yet, my robot still didn't see the light, but since the outdoor terrain is full small stones and stuff, I thought about this problem and tried to solve it. I am sorry, but I didn't understand your last point. You said that if I have to use an elastic mounting, I need to add a dampener, and that goes with the sorbothane as well?? so i need to add another system to the robot or there is any thing simple for robots?

Offline Sarah21Topic starter

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Re: question about the material for my robot
« Reply #4 on: February 09, 2011, 02:20:24 AM »
Thank you for the reply nickc..

Quote
If you are adding suspension, you need to do between the axles and body of the robot.


OK, what about, adding a layer of sorbothane to the wheels? will it help more? or is more efficient to add it like you mentioned?


Quote
If you insulate your robot don't forget you are trapping all the heat from the motors and electronics in.  You might have to add vents or a fan if you are using big motors.  If you have any extra I/O you could add a temperature sensor to your controller and test your insulation ideas.

I am using 4 micro-metal gear pololu motors.. they are not big at all. Will they generate much heat?
So you are saying that I should add a temperature sensor and check whether my insulation solutions are working or not?

Offline rbtying

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Re: question about the material for my robot
« Reply #5 on: February 09, 2011, 08:37:33 AM »
The Pololu micro metal gearmotors heat up relatively quickly at high voltages - how much power are you feeding to it?  You can calculate approximate wattage lost to heat by doing the equation

Code: [Select]
V_in = voltage to motor
A_in = amperage to motor
T_out = torque at motor shaft
W_out = angular speed at motor shaft

Wattage_loss = V_in * A_in - T_out * W_out

That value will have to be dissipated into the environment somehow, so make sure to account for it.

Offline Soeren

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Re: question about the material for my robot
« Reply #6 on: February 09, 2011, 10:26:28 PM »
Hi,

Well, my outdoor temperature may reach to 55C in summer time, it is a desert.
so, with that temperature, and the vertical sun rays, i think it is possible for the aluminum to get heated right?.
Dang, I sure would melt at that temperature but aluminum... Heated yes, too hot to touch perhaps, but that wouldn't be a problem for the aluminum. Everything else, on the other hand...

Which desert is that, if I may ask?


Will the heat generated by the robot be that much?
In high temperatures, people have a tendency to move as little as possible, as even a short walk will only increase body temperatures (but I'm sure you're naturally aware of that).
If your ambient temperature is 55C, adding even a few Watt worth of heat may be a disaster for the electronics, if you encapsulate it.


I did some digging after reading this reply and I read about the aluminum foam and about its different application in aerospace, medicine etc. Is it a good solutions though? 
It's good for deflecting the heat from the sun, like any mirror finish, so if you can add it in places to keep the sun from heating the electronics and motors, but without encapsulating them - it is important to keep air flow as high as possible in temperatures like yours.
A fine mist of water directed to a heat sink or wet felt strategically placed would help - air in itself doesn't cool, it just moves the air and if the difference between the hot air and the cool air is just a few degrees it won't do much difference - evaporation is needed for cooling, as it "uses" heat.


and for the fact that it will trap the heat generated from the robot, will drilling some tiny holes in The 'bot body help in ventelating?
Help yes, help adequately, I don't think so. It will take quite an airflow, perhaps even forced cooling (with a fan).

Make sure all semiconductors you use are spec'd for industrial, military or automotive temperature range.


I don't know the amount of unsteadiness yet, my robot still didn't see the light, but since the outdoor terrain is full small stones and stuff, I thought about this problem and tried to solve it. I am sorry, but I didn't understand your last point. You said that if I have to use an elastic mounting, I need to add a dampener, and that goes with the sorbothane as well?? so i need to add another system to the robot or there is any thing simple for robots?
I have no personal experience with Sorbothane, so I cannot say if they've invented a material that have the right properties for both being elastic and dampening.
Perhaps you have seen a car with the dampeners shot. It rocks like a ship going through waves, as the springs just keep going up and down for a while after a bump.

I think you have to accept a bit of shaking as the only real solutions will be expensive gyro stabilizing of a platform that can move in 3 dimensions and very fast so.
Using a Poor Mans Steadycam with a modest amount of dampening should provide you with usable results - after all, it will convey more "nerve" to the viewer, if it isn't rock steady.

Personally, I wouldn't spend too much time trying to fix a problem before having an idea about its magnitude, so I'd just make sure that the chassis had options for mounting whatever I later found needed.

Building the 'bot and making it go would be my first priority and I guess you should concentrate on getting high temperature tolerant components first - have you planned on a chassis design and on which microcontroller, sensors and motor drivers to use?
Regards,
Sren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline Sarah21Topic starter

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Re: question about the material for my robot
« Reply #7 on: February 13, 2011, 11:40:12 AM »
Hi Soren,

Quote
Which desert is that, if I may ask?

 ;D I live in the gulf region, In UAE in particular, and in summer time.. the temperature do reach up to 55oC
Quote
If your ambient temperature is 55C, adding even a few Watt worth of heat may be a disaster for the electronics, if you encapsulate it.

When I designed my robot body, I thought of preventing any sand or tiny particles to reach inside and damage or contaminate my circuit and components.. so i designed it to be similar to army tanks some how.. will that be considered as encapsulating electronics?

Quote
A fine mist of water directed to a heat sink or wet felt strategically placed would help -

I'll look more for info about the heat sink idea.. thanks for the hint..

Quote
Make sure all semiconductors you use are spec'd for industrial, military or automotive temperature range.

Will that be written in the specifications for the component itself?? coz i don't remember meeting this specification anywhere....

Building the 'bot and making it go would be my first priority and I guess you should concentrate on getting high temperature tolerant components first - have you planned on a chassis design and on which microcontroller, sensors and motor drivers to use?

 
Quote
yes I did, I have my chassis designed, Ill be using an AVR microcontroller, particularly the baby orangutan Atmega 328P, 2 ultrasonic rangers for the obstacle avoidance problem, the motor drivers will be the ones in the MCU.. the TB6612FNG dual H-bridge, mounted on the baby orangutan, one blackfin camera and a matchport b/g, what do you think?

Offline Sarah21Topic starter

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Re: question about the material for my robot
« Reply #8 on: February 13, 2011, 11:41:15 AM »
The Pololu micro metal gearmotors heat up relatively quickly at high voltages - how much power are you feeding to it?  You can calculate approximate wattage lost to heat by doing the equation

Code: [Select]
V_in = voltage to motor
A_in = amperage to motor
T_out = torque at motor shaft
W_out = angular speed at motor shaft

Wattage_loss = V_in * A_in - T_out * W_out

That value will have to be dissipated into the environment somehow, so make sure to account for it.

thank u,  :)

Offline Soeren

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Re: question about the material for my robot
« Reply #9 on: February 20, 2011, 12:37:00 AM »
Hi,

;D I live in the gulf region, In UAE in particular, and in summer time.. the temperature do reach up to 55oC

Dang, forget about the robot, how do you cope yourself? Just 30C and I'm not moving much ;D


When I designed my robot body, I thought of preventing any sand or tiny particles to reach inside and damage or contaminate my circuit and components.. so i designed it to be similar to army tanks some how.. will that be considered as encapsulating electronics?

I'm not quite sure what this means, as I have never been that close to tanks (my pro military career was in radio/telegraphy communication and is just a faint memory).
Not knowing the granularity of your sand (it varies a lot around the world) I don't know if fine mesh stainless steel weave would do(?) at least in some places to get ventilation.

Any reduction in air flow will mean less cooling by air.


Quote from: Sarah21 link=topic=13181.msg98291#msg98291 dat=1297618812
Quote
Make sure all semiconductors you use are spec'd for industrial, military or automotive temperature range.


Will that be written in the specifications for the component itself?? coz i don't remember meeting this specification anywhere....

Yes.
Both in the data sheet and usually on a microcontroller itself, by a letter (and/or number) code.
Around halfway down on this Microchip page you'll find the temperature specs for the various models of PIC16F1828 (just an example).
This is always the temperature directly on the semiconductor junction(s). The data sheet should contain the specs for temperature resistance from junction to ambient (sometimes as junction to housing plus housing to ambient).
At an air temperature of 55C you should calculate with at least 70C ambient (as it's the directly surrounding air, which is heated by the component).
You can get heat sinks to mount (glue) directly on top of a microcontroller for added radiance.

I'm not sure if Atmel has got this info on their pages, but it will always be in the data sheet.
Usually, you'll find it under "ordering info" or similar, since it's the only parameter that's different.

Same thing applies to motor drivers etc.

Using chips and transistors that can handle much more current than what you need will help as well.
Keeping direct sun from all that gets hot is imperative.


Assuming a very low relative humidity in a desert, some kind of evaporation system should have great effect.


Quote from: Sarah21 link=topic=13181.msg98291#msg98291 dat=1297618812
yes I did, I have my chassis designed, Ill be using an AVR microcontroller, particularly the baby orangutan Atmega 328P, 2 ultrasonic rangers for the obstacle avoidance problem, the motor drivers will be the ones in the MCU.. the TB6612FNG dual H-bridge, mounted on the baby orangutan, one blackfin camera and a matchport b/g, what do you think?

The 328p only goes to 85C according to my knowledge :(
If you haven't got this "minor monkey" yet, perhaps you should reconsider.

If you're programming in a high level language, the controller family doesn't matter in particular and having on-board drivers may be quite OK in lesser temperatures, having them at separate PCB(s) may be a better solution in your case.
I have no personal experience with either the Blackfin or the Matchport, but from what I read about the camera, it should be quite good.

Any ideas of the final (total) weight?

If possible, posting pics and/or drawings of the chassis and what else you have (more or less) ready will make it easier to give particular advice.
Regards,
Sren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline Alia

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Re: question about the material for my robot
« Reply #10 on: February 24, 2011, 04:41:55 PM »
Hi
Eventhough I am not that related to the subject. I want to ask from where can I get sorbothane ?

Offline Soeren

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Re: question about the material for my robot
« Reply #11 on: February 24, 2011, 07:12:07 PM »
Regards,
Sren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline Aberg098

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Re: question about the material for my robot
« Reply #12 on: February 25, 2011, 09:28:06 AM »
If solar heat is a concern, try something simple like painting it white...

Offline Juicaj1

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Re: question about the material for my robot
« Reply #13 on: March 13, 2011, 03:24:37 PM »
I don't know just how tough or big your robot is but if you were concerned about heat and strength I might have gone with some hdpe for your chasis. It's pretty cheap and strong you can get it white to reflect some light waves and because it's a polymer its not very thermally conductive ie won't get as hot as fast or as easily as metal. I would assume you probably don't want to redo your chasis so I would consider using it or maybe even Ldpe to make a small casing for your electronics and if you really want to keep things cool maybe add a small computer cooling fan.

 


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