How do I give a radio control car autonomous control

[Kenjones1935]

I don't know how I did not post this URL yesterday

http://ttjcrew.com/

[John_Mac]

Hi Ken

Just looked at the video. Remarkably, this is very similar to what I did and described in my earlier post. Some similarities/differences...I used a larger RC truck platform with 4WD (a junker from Radio Shack), I also ripped all the electronics out and replace the old steering motor with a real servo, I ripped out the RX and motor controller, but kept the H Bridge to be used under PIC control. They put in a new H Bridge, but looks like it was on or off, mine had variable speed control determined by the TX input. They were purely autonomous GPS (only works outdoors). I used a Spektrum DX-7 TX/RX RC system so I could have both RC and Auto control. They used an Arduino board from Sparkfun, I used the MicroChip PIC and my own proto board.

So you see there are many ways to go.

I looked up the VEX system. This is pretty much a lot of plug and play modules that you can buy to do robotics. I think you may still need to buy a TX/RX to have RC control...can get pricey. But you will have to choose.

I am not that acquainted with the various kits that Microchip sells...perhaps others can comment.

I went entirely from the ground up. ICD2 programmer (there are others you can use), I started in assembly but then bought PICBasic Pro (also easy to convert a lot of my old Basic Stamp programs), some 16F88 and 16F627A PIC chips, some proto boards, and supporting electronics (voltage regulator, caps, resistors, jumper wires, header pins,,,,) and built up the hardware and software to make it all work. Most of the sensors from Sparkfun or Parallax will work off a PIC, but you have to read the spec sheets. You will need the usual lab stuff, soldering station, with general electronic parts, batteries, power supplies, and I found the Parallax USB oscilloscope to be absolutely essential in debugging the code. Plus I already had the DX-7 TX/RX. Starting from scratch, this is also pretty pricey way to go. But I had a lot of the stuff and I wanted to be able to modify the control systems at the PIC level for all my projects.

I don't know what you have nor your skill level in this area. You can get some help here on the Forum, but if you go with a plug and play system, it is more turn key and probably forums for those as well. Looks like the Tech Junkie website will have all the code and schematics for what they did, but you would have to go with the Arduino boards which use Atmega chips, not PICs.

Take a look at the DIYDrone website and the ArduPilot system there. this is a great site for autonomous systems, and it is all freeware with most of the parts from Sparkfun. They have lots of stuff you might be able to use and a forum to get a lot of answers....and it is all as cheap as you can get. check this out:

http://diydrones.com/profiles/blogs/ardupilot-main-page

I have a blog there on using a dsPIC IMU system for model helicopters, still PIC based but use C code and microcode C compiler.

You will have to decide the route you take, but it can be a lot of fun.

Good luck

John

Oh...your question on switching from manual to auto...the switch is on the TX. It sends either a short PWM or long PWM to the RX and the PIC reads this to decide if it passes TX signals directly to the servos (manual) or is in control of the truck (auto)....not DTDT switches. And I also use Windows.

[Kenjones1935]

Here's my idea.

The underlying purpose is to interest middle school kids in STEM.

Hobby level RC cars are technically really neat but the engineering is mostly cut and try. Missing is an element of formal language combined with intent. You know formal language as a "blue print" a "recipe" a "musical score" a "program".

I suggest a competition, a race, to be held in the Longsjo Middle School (Fitchburg, Mass) gymnasium plus its lobby. The racing vehicles are 1/10 scale RC hobby level cars or trucks. The race course is delineated on the basketball court by four inch plastic flexible conduit and maybe some traffic cones. The course extends out into the lobby to which there are two doors the width of the basketball court apart.

Inside the lobby is out of sight for the kids handling the RC transmitters. The regular lights are dim in the lobby. A bright light is placed in the doorway that leads back into the gym. The cars must find their own way back into the gym.

Let's guess three or four cars racing each other. The first car to complete three laps wins.

Can I build a car system robust enough to withstand the violence and simple enough to program? I am thinking of a simple language like ROBOlab or Terrapin LOGO. Both of these can easily follow a black line with a light background. I have done that. I think they could also easily find and go to a beam of light.

What do you think? Will it work? Is it practical? Should I start with a PICaxe kit?

Ken

[John_Mac]

Good plan Ken...and glad you are getting students involved.

I cannot comment on the language you quote since I have no experience with them. What you describe, however, sounds very well suited to the Basic Stamp. Look at the Parallax site and look for the Board of Education. This is a Basic Stamp processor with an integrated proto board and voltage supply/regulator. It comes with a Basic Stamp program editor and integrated USB programmer. There are lots of example programs and Parallax sells lots of sensors to interface to it. I actually started my RC truck project on a Basic Stamp. The major limitation was that it has limited program storage for lots of variables. But for simple programs, it is very adequate. they also have more advanced Propeller systems as well. The nice thing about the Basic Stamp is that if you want to go more sofisticated on a PIC, you can get the PICBasic compiler (this site) and the programs port with little changes.

The competition you describe sounds very challenging. Depending on what the obstacles are in the lobby, you may run into some serious navigation issues. An arbitrary course with chairs, tables, cabinets etc would require a great deal of sophistication to navigate. You could put some "clues" in there, such as bright LEDs or something a simple detector can locate and navigate to. If you think of tight turns with an RC car, it requires backing up, turning, etc. hard to do completely autonomously, but not impossible.

I strongly recommend you take a good look at the Basic Stamp. Easy start up, few extra components, relatively cheap (you might get an education discount), simple sensors, and lots of programs out there to build on. It is also an easy step to upgrade to a more complex PIC system from there.

John

[Kenjones1935]

Thank you , again, John,

The Parallax products look just about right. They also seem to offer plenty of support.

Initially I would have no obstacles out in the lobby of the gym. The car would still have to make a 360 turn to find the light at the exit door, then go to it. If I place the light correctly the car would reappear to the RC transmitter person once it reaches the light.

The RC car suspension could be challenged by putting wooden ramps in the gym floor course. The type of tire affects their skidding. Which in turn affects their turning ability at speed.

Thank you again and again for your help.

What do you do professionally? How did you get so involved in RC/auto
flight?

Ken

[John_Mac]

Hi Ken

My pleasure and good luck. Retired physicist here, always played with RC and processors/sensors....just not together. Now that I have time I, get to play with my toys

Happy to share ideas and code/schematics, or just another set of eyes.

John

[Kenjones1935]

I am new to Parallax. It comes highly recommended.

I wish to build a 1/10 scale hobby level radio control car that can also run autonomously. I think they have a PIC that can do the job. The question is how do deal with the Pulse Width Modulated signals that come from the radio receiver. Presently they go directly into the electronic speed control module and the steering servo. I thought that for my design I could use them as inputs to the PIC.

I hope that I do not have to use PIC code space and compute power to continuously sample the three RC receive channels. Is there some kind of transition detector which can digitize the PWM signals? I assume the PIC input can figure when they change.

If Parallax does not make an appropriate micro to be the central brains of this operation I can use a DPDT switch under PIC control to steer the PWM signals. There has to be a signal from the radio transmitter telling the car which mode is appropriate. That signal has to be interpreted by the micro somehow.

Ken