Servo2

This is called a proportional regulator and its the most simple but stable regulator you can make. But its not the quickest and its not the most precised one. Cuz a P regulator needs always a little failure to keep the position more or less precise. The P factor you have choosen will cause many problems. One will be overshots. Cause the motor will not instantly stop if the driver switches from 15V to 0. One way to reduce this is decrease the P. If you want a faster and more pricise regulator, there might be a PI or even PID regulator the better choice. But start always with a P regulator and find P. Its defintitive not 100000. Its much lower.