Unfortunately I'm a newbie of simulink and I had problems. PIN 9, PIN 10 and PIN 11 represents the pin of ARDUINO UNO so if they are setted to HIGH produce 5 V otherwise they produce 0V. I created this
You can try using acontrolled voltage source and adding a ground to one end of the source and connecting the other end to your system. Furthermore, you should be able to add a ground after the diodes the same way you added the solver (by splitting the signal).