Angle Controllable Seesaw

This project is an angle controllable seesaw that is intended to demonstrate feedback controls. There is a seesaw structure with a DC motor with a propeller on one end of the arm. This motor spins to generate a force on the seesaw arm to keep it horizonal. The angle of the arm is detected indirectly by using an ultrasonic sensor. This sensor measures the distance from the ground to the motor. If this distance is smaller than nominal for a horizonal arm, then the motor spins faster to lift the arm up more. If the distance is larger than nominal, then the motor decreases its speed. The motor’s speed is computed by the Arduino using a PID controller. There are two status LEDs. The green LED turn on when the motor is spinning, and the red LED turn on when the motor is not spinning. There is also a switch to turn the red LED off. I found that the motor does not spin fast enough to generate large amounts of thrust, so for the motor to have the desired control authority, the seesaw should be reasonably close to balanced, which is why the 9V and AA batteries are on the other side of the arm. The 9V battery powers the motor, but the AA battery is just there for balance.