How do I give a radio control car autonomous control

[mackrackit]

Maybe just leave the RC part intact. Add another RC channel and another board.
The second board would be for auto.
The added RC channel would be to switch power from one board to the other.

[Kenjones1935]

Yes, this idea might work.

My problem is that I do not know the details of the I/O signals of the various parts of these 'bots. With LEGO RCX the outputs to the motors come directly from the encapsulated microcontroller system. The motors are not as powerful as those in a RC car. The commands available to the RCX from the ROBOlab program have seven levels of power.

The RC cars, on the other hand, are driven by a 7.2 volt battery pack through a box called a "speed control". Speed control gets its signal directly from the RC receiver. I think it is treated as a servo. Is this pulse width modulation?

I am hoping to borrow an oscilloscope soon.

Ken

[mackrackit]

This might help some.
http://ww1.microchip.com/downloads/e...hapter%205.pdf
and the suggestion up in post #2 also.

But yes, PWM is how speed is controlled. How your car is setup I do not know. Maybe if you gave a brand/type someone here might know off hand?

[Kenjones1935]

Still finding it difficult to find the I/O details of my radio control receiver and my electronic motor speed controller. What is on those three wires (white, red and black) between the receiver and the ESC?? Also what is the information format on the three wires (blue, red and black) between the receiver and the servo?

RC receiver: FUTABA FP-R122JE am 2 channel BEC

ESC: NOSRAM Tomahawk Reverse 93050

motor: MABUCHI RS-540RH/SH

[John_Mac]

I have done a lot of work on Autonomous control of RC cars, helis and airplanes. My applications have mostly been on stabilization and waypoints for aircraft using in inertial measurement unit (IMU) board. On the RC car, I ripped out the simple RC controls and replaced them with a Specktrum RX.TX system. I used a PIC processor to convert the throttle PWM signal into something the existing H Bridge motor controller understood and replaced the steering servo with a standard RC servo. I have a camera on a servo controlled pan and tilt servo system, and added things like the Parallax PING sonic distance sensor, and compass module and a GPS (but this only works outside). There are a lot of things you can think of adding.

Looks like you already have a real RX/TX system with a BEC/ESC to a motor. The signal going from the RX to the ESC; Red/Black/Blue(sometimes different color) are +V/GND/Signal. Signal is a Pulse Width Modulated signal whose width tells you how much throttle to apply. Typically this signal will be 3.5v (or so) and a width of 1.2 to 1.8 usec, depending on throttle setting.

Autonomous control will depend on what you want to do and what sensors you need to accomplish it. Waypoints won't work indoors with a GPS, but you can memorize a track, detect obstruction, follow a wire or tape track, lots of things.

A very sophisticated version of indoor automony is a laser scanner that basically maps its environment, but very pricey. You could try a sonar version of this using the PING sensor, lots of math and geometry involved.

Good luck and have a lot of fun with your students.

John

[Kenjones1935]

Thank you, John for answering my questions. I am out here in the middle of Massachusetts. Is there a robotics club around?

My RC car is not the correct one for this job. It has 4 wheel drive and hence a drive belt down the middle where I would mount the PIC. I refer to it because that is all I have. If this idea takes wings a new car can be purchased.

My first thoughts for autonomous control sensors is simple sonic proximity detectors. If they looked to the right and to toward the front, I'll bet I could program the car to follow a wall (close on its right side) until it found an opening (in a corner). Or something....

I need to pick a PIC. I've been told that VEX uses Microchip's 18F8520. Our local technical high school has some VEX kits, but I do not have access to play with them. Any suggestions would be greatly appreciated.

I am a retired digital hardware and software designer. I still have my Texas Instruments 7400 Series TTL catalog. I have not done hardware design since the early 1980's. I am way out of touch.

Ken

[John_Mac]

Thank you, John for answering my questions. I am out here in the middle of Massachusetts. Is there a robotics club around?

My RC car is not the correct one for this job. It has 4 wheel drive and hence a drive belt down the middle where I would mount the PIC. I refer to it because that is all I have. If this idea takes wings a new car can be purchased.

My first thoughts for autonomous control sensors is simple sonic proximity detectors. If they looked to the right and to toward the front, I'll bet I could program the car to follow a wall (close on its right side) until it found an opening (in a corner). Or something....

I need to pick a PIC. I've been told that VEX uses Microchip's 18F8520. Our local technical high school has some VEX kits, but I do not have access to play with them. Any suggestions would be greatly appreciated.

I am a retired digital hardware and software designer. I still have my Texas Instruments 7400 Series TTL catalog. I have not done hardware design since the early 1980's. I am way out of touch.

Ken

Hi Ken

I'm out in Colorado, so don't know much about clubs in Mass, but you do have MIT there and they are well known for their work in robotics. You might see if you could connect with them. The laser scan I mentioned was at MIT. Here is a link you might enjoy:

http://diydrones.com/profiles/blogs/...ter-with-laser

I don't really know about VEX, but I have chosen my PICs based on numbers of hardware PWM channels, ADC channels etc...so depends on application. I never found I taxed the speed of the processor.

One thing I started, but never really finished was to put a PING on a servo so I could rotate it left and right. I took a left/right scan and stored the distances to detected obstacles, basically making a map. I could then make decisions on where to go next. You can't really scan very fast though due to a couple of things. The first is that you need to make redundant measurements to filter noise out at each setting, and then the servo is constantly moving and can limit it's lifetime. So this isn't useful for a fast moving car, but maybe a crawler. I like the idea since it requires some math and algorithm development as a learning project.