Starting an autonomous plane project

skatj

http://www.parallax.com/detail.asp?product_id=27207

Me and my friends are looking to build an autonomous plane for the state science and engineering fair, and I was wondering if this kit would work for us. We only have experience in mindstorms robotics so this is a huge leap forward for us and we're desperately trying to learn.

I have a couple questions

1) it says we need to power it with a 9V power supply, but can we use a battery instead?

2) will we be able to attach gps/altitude/gyro sensors to this?

3) will the board of education work with this http://www.parallax.com/detail.asp?product_id=29144?

4) assuming we have that motor control product, would we be able to run 4 servos(possibly 5), plus 1 DC motor for the propeller, as well as various sensors?
any suggestions for motors?

5) any suggestions on what else we would need to buy?

Post Edited (skatj) : 10/13/2007 7:11:07 PM GMT

D Faust

1) You can use a 9V battery or the battery pack that is sold with the boe-bot (you can buy it separate). The stamp only needs 5V so you might want to consider lithium Ion cells (3.somethingV) to reduce weight. If you want to run servos off the board then you will want a 6V supply because if the servos try to draw their power through the 5V regulator it will have to dissipate too much power.

2)Yes, you should be able to attach a GPS (parallax sells one), as for the altitude and gyroes, it depends on the product. Do you have one in mind? Does anyone else have soem that they have used with success?

3) the url must not be right. What is the product called?

Yes, you should be able to control the 4 or 5 servos (you would probably want to get a Parallax Servo controller to offload this from the stamp {you have to send a signal every so often, and this can be a pain.) The dc motor should work fine considering you have a motor controller. (Pololu motor controller, or motor mind B might work well for this.) What size plane are you talking about (RC care size 1ft - 1 1/2ft?)

I have used mindstorms myself and PBASIC is completely different. With mindstorms you don't get into the electronics of everything. I have not heard anything about this kit, but it looks suitable for beginners. Just a heads up.

EDIT: you might want to change the name of the thread to involve a plane (there are a few people who have built planes and you might get their attention if you put that in the title.· Do this by clicking the pencil in your first post and changing the subject line.

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skatj

D Faust said...
1) You can use a 9V battery or the battery pack that is sold with the boe-bot (you can buy it separate). The stamp only needs 5V so you might want to consider lithium Ion cells (3.somethingV) to reduce weight. If you want to run servos off the board then you will want a 6V supply because if the servos try to draw their power through the 5V regulator it will have to dissipate too much power.

So do I have to solder wires to the battery or something? And that one battery can power everything, the servos, the motors, and the board?

I think the question mark broke the link, here it is http://www.parallax.com/detail.asp?product_id=29144 HB-25 Motor Controller

Not sure on the exact size of the plane, but it will be fairly small. Would this be compatible, if not any suggestions for motors?
http://www.redrockethobbies.com/product_p/watt157155.htm

D Faust said...
Yes, you should be able to control the 4 or 5 servos (you would probably want to get a Parallax Servo controller to offload this from the stamp {you have to send a signal every so often, and this can be a pain.)

Alright, where can I buy a servo controller, I can't seem to find any on the parallax website. And what do you mean by "you have to send a signal every so often, and this can be a pain"?


Thanks for the help, like you said this stuff is a huge leap from mindstorms, and I am really nervous about screwing something up or buying the wrong products

Mike Green

Look under products / accessories / motor control.
The PWMPAL can control 4 servos and the Parallax Servo Controller can control 16.

DiablodeMorte

I'd love to help w/ this project. I'm starting one of my own and I'll need all the help i can get(I just ran my schools gas plane into the ground so hard it shattered some of the insides and broke the wings in half)

D Faust

If you use a 9V battery you should not use it for the servos.· There is a connector on the board for such a battery.· If you use the boe-bot battery back, that outputs 6V, then you should be able to run the servos and motor off of it.

I have no experience with planes so I could not tell what is neccessary.· The HB-25 is typically for larger motor, so unless you are making a large plane the pololu or motor mind B will probably work best.· It all depends on the motor, so choose that first.

Look under the motor controller section for servo controllers.· What I mean·by you have to send a signal every so often is that you do not set the position of the servo and it will keep that position.· You have to tell the servo every so many (40?) instructions the postion that you want it at.· With the servo controller, the servoes become "set·and forget", because it pulses for you.· There is a new project coming out called a servoPal, that goes inbetween the servo and the controller (basic stamp) to keep sending the position signal after the stamp stops.· I hope this clarifies it.

I would order the kit, because then you will understand this a lot better.· You can order the other parts later.

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allanlane5

The problem with a model airplane is -- it's only a matter of time until you crash and destroy it. And making it "autonomous" is also not trivial. It can also be quite an expensive hobby.

But if you've got $1,000 hanging around for building prototypes and trying things, go for it. Probably you want a 9.2 or 9.6 volt battery pack -- but as has been said, those can be heavy. A 7.2 volt battery pack is more practical for servos. However, I feel SURE there are off the shelf airplane systems with servos, a controller, battery, charger, and RC remote. Hopefully you can 'hack' a large one of those to install a small PC board with BS2, GPS, and accelerometers.

To keep costs down, I recommend Off The Shelf whenever possible. People have been flying hobby planes for a really long time, and you want to take advantage of any mass-production items you can.

skatj

Alright i'll order the kit before I try anything else.

Also, it wont be truly autonomous in that it can autopilot to a certain location, our goal is just to get it off the ground and fly around with a preprogrammed flight path. A more accurate description would be "non R/C model airplane". We have a budget of around 350$, possibly more

skatj

Fast question, are the parallax chips/motor controllers compatible with brushless motors? I'm a little afraid we're gonna end up building the whole plane and find out a regular DC motor wont have enough thrust to take off

allanlane5

I didn't think you controlled the plane ENGINE with the Stamp, but you DO control the elevator and ailerons and rudder with servo controls.

D Faust

I think that a brushless motor needs AC waveform, but I am not sure. aka no the parallax controllers won't work.· If you do· use a dc motor and do not need speed/direction control then you can just use a transistor to trigger a relay to turn on the motor.

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AP

It is common to control the motor like it is a servo: by a standard speed control made for electric motors of R/C airplanes. You can purchase a speed control to suit the motor (brushed, brushless), because both take a standard servo pulse (PWM 1-2ms at 50 Hz)

skatj

So if I don't buy a parallax motor controller, and buy a brushless motor I can just hook the motor to something like this, http://www.redrockethobbies.com/ElectriFly_BL_8_Brushless_ESC_p/gpmm2070.htm then hook that to the Basic Stamp?

Does it need a separate battery or what?


Would this brushed motor work with the motor controller? http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXWK49&P=V

Post Edited (skatj) : 10/15/2007 3:03:49 AM GMT

RichardF

skatj,
I am an experienced electric RC modeler. Trust me on this! Build an electric RC airplane first (an electric high wing trainer from Tower Hobbies would work fine). Learn to fly it well and learn how the components work together. Going autonomous from there will be easy, it is just going to crash a lot and cost a lot of money! Seriously, sticking a basic stamp into the plane and controlling servos in a predetermined sequence loaded into memory is easy. The problem is dynamics. If a gust of wind comes along (and it always will) and lifts a wing the stamp program has no way of knowing that the airplane is already rolled into a turn and it will blindly give a signal to the aileron servo to turn, and now the airplane is upside down! You get the drift, I am sure. To make this work with any reasonable chance of success you need a full set of accelerometers and gyros·for all axis which can tell the stamp what the aircrafts attitude is in the pitch, roll and yaw axis very accurately. Then the stamp program has to figure out how much input based on that information to give the servo to accomplish what it was programmed to do. It is going to have to be a closed-loop system with lots of math going on. The basic stamp is way too slow to have any chancie of handling this. The propeller chip would work great because of its high speed and multiprocessing capability. Worrying about what motor/battery combination to use is down in the minutia compared to other problems you will encounter. Many experienced RC pilots can't handle a gust of wind. Compare their brain's capability to the basic stamp!
A few years back, an autonomous RC plane was flown by amateurs across the Atlantic Ocean succesfully. You could start by reading their story in the AMA archives available at modelaircraft.org. Good luck.

Post Edited (RichardF) : 10/15/2007 12:13:54 PM GMT

Professorwiz

Adding on to what RichardF had said, I have flown RC Helicopters, and planes for more than 14 years. You also might what to add in to the mix the GPS modual that Parallax sells. You might also look at the SX chip, more involved programming but it might work fast enough. I think that perhaps having different channels having their own sensors with their own chips might work out, then have a centralized command unit that reads in the GPS modual.. hmm.
Russ

RichardF

Also, please note that there is a world of difference between sending an autonomous aircraft to a distant point in space, such as crossing the Atlantic Ocean, and that of flying a set, predetermined pattern. In the first case, by just using a couple of RC gyros and a magnetic compass module (sold by Parallax) I can easily get a plane to fly a reaonably set path and stay upright. That is a whole lot different than saying I want the plane to fly a certain distance, then turn left 90 degrees, then fly another set distance, then turn left 180 degrees, etc. What about the wind blowing it off course? What about a thermal updraft increasing the altitude? The plane crossing the Atlantic didn't really care much about the altitude as long as it didn't hit the ocean surface. By adding a GPS unit if the plane gets blown off course a new magnetic heading can be determined. This is all pretty heady stuff and not for the weak of pocketbook. Have fun.