Friends on R-Pi Official Forum told me that it would be good to get a servo controller in order to control multiple servos. Raspberry Pi only has one PWM output but with I2C, Raspberry Pi is able to communicate with PWM driver such as PCA9685.
The recommended one is the Pololu Micro Maestro 6-channel USB Servo Controller.
I have also found another Servo Controller from AdaFruit – Adafruit 16-Channel 12-bit PWM/Servo Driver – I2C interface – PCA9685.
AdaFruit Servo Driver would need a breadboard, DC adapter and other wire connections while Pololu seems to need just a USB to micro USB connection.
Here is a get-started video:
The controller can be used with/without USB as mentioned in the starter guide. There is driver and software sets for Windows and Linux if using USB. The software is useful to test the servo motors and to configure the movements. The configured movements can be saved into a BASH script. There are examples written using Python script (without using USB?).
Relevant tutorials for Pololu:
Relevant tutorials for Adafruit:
With one of this, I think I no longer need the Gertboard or Arduino. But I couldn’t really decide which one to get. Both seem to have their pros and cons.