Update: added RemoteXY software and HC-05 Bluetooth module to update PID parameters with my phone. Software is easy to use but I need to buy the full version (only 8 bucks) to add more controls. Only problem is that it stopped communicating with the bluetooth module when it encountered a timer1 interrupt so had to change program to use a millisecond count loop and all was well.
After I buy the full version, will add a joystick control to make robot directional. Fun project as I learned how to use Bluetooth module and RemoteXY software for the phone which is really easy to implement.
Original Post: Here is my first real self balancing robot though I have done some simple bang-bang ones in the past. I used this instructable (not mine): https://www.instructables.com/id/Arduino-Self-Balancing-Robot-1/ which is about the simplest treatment of self-balancing I have ever seen. Downloaded the libraries, input my robot's calibration parameters, compiled the sketch and it worked. Needs work of course but am only using P of PID right now.
Mine is using mini L293D motor shield, Arduino Uno, MPU6090 acc/gyro and surprisingly everything is run with a 2S 800mah lipo, without any external voltage regulator - using only the one on the L293D shield to power MPU6090 and the Arduino Uno. Simple.
See his instructable for details as it is a great writeup about how to make one.
Need to tune mine but might try RemoteXY software and an ESP8266 to update PID parms and try a little steering.
This is a companion discussion topic for the original entry at https://community.robotshop.com/robots/show/self-balancing-robot-using-remotexy-and-bluetooth-to-pass-in-pid-and-cg-parameters