Hello, I have the same problem. I've made a model of the self-balancing motorcycle and then I've exported it to Simulink to design the PID controller. In the model, the controller that I've designed works well, but when I put it in the self-balancing motorcycle, it fell down. Also, I've tried with a LQR controller and I've achieved 10 or 15 seconds of balance, only. I've modeled the inertial wheel motor to put it in the model, but I think the motor's parameters isn't correct. Could someone help me?