help me in flying robot....

[ashok7067]

hi.. m doin a project on flying robot... can anyone suggest me how 2 balance the robot.... i want info on digital compass also....

 

[mostafa_et]

Hi Ashok,
Well you are asking a question that can be answered in books, I will not try to give a full answer to your question, as frankly I don't have the full knowledge to cover it, but I will try to give you a few pointers.

When you say how to control the balance of a flying robot, I assume you are talking about keeping it flying steady, to do this you will need to control your robot's orientation in the air, i.e. you need a control system.
A control system can be described (this is not in anyway a formal definition) as a system that measures a certain quantity (temperature, speed, etc...) and then use a control element (a motor, movable surfaces on an aircraft wing, etc...) to change that quantity and bring it as close as possible to a desired value, in other words a control systems "senses" something, "thinks" if this something is ok or not, and then "decides" how to change it if it is not ok. This means you need three things
1- Sensors (you cannot control something if you don't know what is its current state)
2- Logic (to compare the measured value with the desired value and decide how to bring it to the deisred value if it is not there)
3- Control Element (this is the final element that has the power to change the value that you are trying to control)
* To be a little more specific, you need sensors to measure the position of your robot in three dimensions, I believe these are called attitude sensors, check out this link https://www.freepatentsonline.com/6181989.html titled Aircraft attitude sensor and feedback control system, it talks about an infra red system to sense an aircraft attitude, I don't know how effective it is but it's a start, use google, it's your friend search for aircraft attitude sensors to start with.
* Next you need the brains to make a decision on what to do if your robot is starting to point downwards or starting to list to the right for example, for this you need a background on feedback control systems, this article should give you a start https://newton.ex.ac.uk/teaching/CDHW/Feedback/ titled Feedback and Temperature control
* Finally you need some knowledge about Aerodynamics and Aircraft design, I don't have resources for that but you can try googling it.

I fully know that I haven't answered your questions, but I certainly hope I have given you some pointers regarding what to look for or what do you need to learn, I believe that sometimes this is half of the road to travel.

Good luck, inform us about your progress and don't hesitate to ask me for any clarifications regarding this message.
Mostafa

 

[ashok7067]

thanx mostafa... let me tell my idea briefly... my robot uses four rotors on four sides like a plus "+" pattern... wen all de motors run at de same speed,de robot will raise up...
wen it wanna go straight meanz the front motor slows down...
wen it wanna take a left meanz the left motor slows down...

so i wanna keep my robot in a stable position always... wat kinda sensors can i use to maintain its position and prevent it from falling down...

waitin 4 a reply....

 

[mostafa_et]

Ok, here is what I have done in response to your question:
I went to digikey.com, a large supplier of electric/electronic components, it has ICs of every kind, relays, sensors, connectors, soldering tools, LCD displays and the list goes on.
I searched for tilt sensors, the results returned came in three categories, I tried the tilt category, but it returned switches only, i.e. on/off switches that toggle at a certain tilt angle (typically > 30 deg.) which I though unsuitable to your application, thus I turned to the next category, which is magnetic switches /sensors which returned one sensor, I looked at its datasheet (provided at the site) and I found that it could work, it has UART and SPI interfaces, among others, it has an operational range of +- 60 deg. and accuracy of about 0.5 deg in two axis, the problem is that it is 1- expensive ($385) and 2- Sensitive to magnetic interference, so the motors for your propellers could interfere with them, as it measures the tilt angles based on earth's magnetic field as I understood.
Now I know that the above is not an answer to your question, the reason is I regretfully don't have enough time to thoroughly research for a suitable sensor, so instead I have tried to show you how you can find it yourself.
Try searching google for "tilt sensors" and then to save time, don't open all the links that are returned, open only the links from known semiconductor manufacturers, ex. ST Micro, Texas instruments, national semiconductor, philips, freescale, etc.
I wish I had more time to help, but I hope the above can get you started.
best regards,
Mostafa

Added after 4 minutes:

Hey, here is another thing I found, it's an article in sensormag.com about electrolytic tilt sensor, it claims it is very accurate, price range is $5 to $50, and being electrolytic it is not susciptible to electromagnetic interference.
regards,
Mostafa

Added after 59 seconds:

oops, forgot to paste the link.
here it is **broken link removed**

 

[mondunno]

flying robot?

u mean flying on its own?

just get the hardware and mechanical parts first(which is the worst part)
next get familiar to program it.

 

[melc]

thanx mostafa... let me tell my idea briefly... my robot uses four rotors on four sides like a plus "+" pattern... wen all de motors run at de same speed,de robot will raise up...
wen it wanna go straight meanz the front motor slows down...
wen it wanna take a left meanz the left motor slows down...

so i wanna keep my robot in a stable position always... wat kinda sensors can i use to maintain its position and prevent it from falling down...

waitin 4 a reply....

You need only 3 motors, 1 for rising up and two for direction commands. Imagine an UFO. There are plenty chinese toys on this principle. The body is made from polistyrene.
If I'll be less lazy I could take a photo for you...

 

[ashok7067]

using 3 motors??? can u send me any link 4 tat.....

Added after 49 seconds:

thanks a lot mustafa.... it was really usefull....

 

[tonybg]

Whw don't you build the classical tandem twin motor helicopter.two indentical
motors,at the back and the front,one slightly above the other.they are used for lifting heavy cargo.that will solve a lot of the weight problems of the helicopter.

 

[ashok7067]

**broken link removed**

this is the robot with 4 rotors.... but i cant understand how it'll be stable with 2 and 3 rotors.... can anyone upload the picture and the url of that site plz....

 

[coblaze]

Hi Ashok.

The project which you are looking at is one on which I have done quite a lot of research. Unfortunately I havent had the time to make a prototype . Anyways, I;m here to help you.

See using 3 motors will be much tougher than using 4. You'll realise that once you start thinking about the physics of it. Now, any object in the air has 6 degrees of freedom viz. rotations about 3 axis and motion along 3 axis. To controll all of them is going to be quite a task.

So basically you have 4 means of controlling these degrees of freedom viz.
1) Throttle (which in this case is upwards)
2) Yaw
3) Roll
4) Pitch

Now, to measure the accelerations related to the 6 degrees of freedom you'll need.
1) 3 axis MEMs gyroscope (pretty expensive )
2) 3 axis Accelerometers
3) Electronic Compass (to sense the direction)

If read up about all this, it should get you started on the project.

Cheers
coblaze

Added after 3 minutes:

this is the robot with 4 rotors.... but i cant understand how it'll be stable with 2 and 3 rotors.... can anyone upload the picture and the url of that site plz....

Have you made that??

Added after 2 minutes:

BTW what you are looking for is also commercially available as "drangonflyer"

 

[melc]

using 3 motors??? can u send me any link 4 tat.....



This is the basic structure:
**broken link removed**

As you may see in the movie, it can't be controlled only up and down because it's spinning. Adding two left and right horizontal engines will keep the the spinning out.
I have one but I've didn't found yet the left-right engines, both must be powerfull.

 

[kender]

Now, to measure the accelerations related to the 6 degrees of freedom you'll need.
1) 3 axis MEMs gyroscope (pretty expensive )
2) 3 axis Accelerometers
3) Electronic Compass (to sense the direction)

Magnetic field sensors (aka compass) and gyros are redundant, so you don't need all of these three items. You might be able to get away with either:
- 1) and 2)
- or 2) and 3) In this case you will need a 3 axis magnetic sensor. Did you have this design in mind originally?

 

[kbrahma]

I still wonder if 4 rotors are really required?