Hi Sai Tez. Arduino can not drive a motor directly, same as Raspberry Pi. Saying that, you do not need an Arduino if you do not want it. You can control the Raspberry Pi GPIOs output, to logically control an interface, like the relay same as Arduino. For example, with the WiringPi library you can control the GPIOs for motor direction and delivery PWM for motor speed. The diagram that I sent before shows that. Of course, in that case the interface was obtained by a H-Bridge that can drive small motors. For big motors, relays, contactors, are needed.