To adjust the voltage supplied to the actuator I assume I could use some sort of digital PWM, but I'm confused about the differences between analog and digital PWM. Is digital PWM just a matter of switching between 0 and 5V more quickly than you would if you wanted an analog signal? Also, given that the max DC voltage of the actuator is 12V, I was considering implanting a simple non-inverting amplifier between the Arduino and the actuator. I'm worried about overdrawing current from the Arduino as well, so I thought that implanting the non-inverting amplifier might help with that respect, drawing current from Vcc+ (please correct me if I am mistaken).
I thought that a servo utilized position predictions in determining where the shaft of the device should be, and for my purposes I need to have speed control over the motor. I thought that it would be simplest to make a DC PWM signal which is amplified with a gain of 2.4 so that I could control the speed of the motor by simply varying the amount of time that the 5V signal was on during PWM. Is this not a possibility? If I were to use a servo, I don't really understand how I would vary the signals to it to control its speed, rather than position. I'm trying to make a syringe pump attached to a closed system which reduces the pressure in the system at a constant rate.