Why didn't you say that in the first place?
The first sentence in Reply # 1 says?
We have separate power for servos, microcontroller get power from Arduino.
The Arduino IS the microcontroller. Please explain the second sentence.
Also, take a picture (or more than one) of your hardware, showing all the connections between the Arduino, the SD21, the batteries/power supply that is powering the SD21, and the servo connections to the SD21. Host them on a picture sharing site, and post links to those pictures.