I felt this is a question needs to be further clarified to the local host. In the past, I understand our local host misunderstood the total 15 V all together; does not matter how they were connected. Based on this email, it sounds like agangavaram's setup is allowed, ie..
-> Robot carries two separate pack of batteries pack, one 12 V and one 9V
--- the 12V is only for motor
--- the 9V is only for the microcontroller
Is that correct?