Controlling a Jaguar with a Raspberry Pi

[ToddF]

I got my order of Raspberry Pis this week. This weekend I sat down and figured out how to use the Pi to control a Jaguar. Here I'm just typing text commands at the command prompt which set the PWM pulse width going to the Jaguar. I found the right numbers using a cheap RC servo, so the Jag may use slightly different values for full forward and reverse. 600 microseconds is full reverse. 1500 microseconds is stop. 2400 microseconds is full forward.

Video here.

[droswell]

Very cool! I wonder if the Kinect can plug into the Pi to offload the video processing?

[RyanN]

Very cool indeed. We're using a Raspberry Pi for our Senior Design project at Mississippi State University. We're attaching one to a robotic blimp.

We decided that driving 3 motors, along with taking in I2C and SPI sensor data, was too much for the Pi (mainly not enough pins on the header to do everything we needed), so we decided to talk to a PIC24 over UART to command motors and sensors. Plus, many of the Pi's lower level controls and communication aren't very mature. We were able to talk to an I2C device using the Pi, and toggle some LEDs on, but PWM output wasn't working so well.

Offloading this also allows us to do more with video streaming. Mainly, the Pi is being used for communication rather than processing data, but as we progress, the use of the Pi's power will be greater.

The Raspberry Pi has great potential for robotics applications. If you're interested in something like this, also have a look at the BeagleBoard and BeagleBone. They're more expensive, but the software they run is more mature.

[ToddF]

If pins are your problem, the I2C interface is the solution. The best priced servo driver board I've found is sold by Adafruit. It costs $14.95, is only 1"x2.5" in size, and drives 16 servos. You could add up to 62 of them for a total of 992 PWM outputs. I'll probably end up using one of these, but right now I'm experimenting to see what I can do without adding any supporting electronics.

I haven't yet researched I2C boards for input signals, but I'm sure they are out there.

[ToddF]

All,
I wrote a simple script user interface so the speeds of all eight servos are displayed and are easily modified with the arrow keys.

Video here. I demonstrate using one Jaguar and two servos.

Todd F.

[markgryzwa]

Servo controls should be 1500usec for neutral. 1000usec for full reverse, 2000us for full forward. I use an Arduino microocontroller with a joystick shield added for full control of the drive.

[markgryzwa]

http://www.youtube.com/watch?v=gcuFZ...1&feature=plcp

Video of arduino demo

[ToddF]

These go to eleven...

http://www.brookshiresoftware.com/rd...ervos_work.htm