Yeah.just change the set point by a little bit. eg. if you change yaw,it will move left and right to correct it.For the balance point slightly in that direction.If its too low the bot will not move.If too big,the bot will slide too fast and may lost it balance.
It seems like you haven't installed the PID library.Please install the library from the links provided above or from my GITHUB.
UPDATE:digitalIOPerformance library doesn't work on Arduino 1.6. Use Arduino 1.5 for compiling the program.
It's good to hear you have interest in robotics at such an early age.For learning Arduino,you can refer any book or tutorials on internet.One example is:-http://electronics2work.com/tutorials/arduino.htmlThe link to download app is given in the tutorial above and yes you can move it in all the four directions.
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