What are common control strategies for dosing pumps?
There are thousands of ways and products to mix fluids and gases , titration pumps, pulse pumps digitally controlled, radial pumps, bubble control pumps for gases &amp;  medical, consumer, industrial, military, aerospace for many industries.

Basic designs include;


Rotary pumps => Consumer: Aquarium version shown here
Reciprocating Style Metering Pumps => 


displacing a fixed volume through the reciprocating motion using;
a piston, a diaphragm, or a bellows

Liquid Diaphragm Pumps ( like those used in fuel pumps )
Diaphragm Liquid Metering Pumps ( discontinuous pulsed operation, including those with magnetic drive)
Electronically Controlled Diaphragm Metering Pump ( more precise with flow sensing )
Pulsed syringe mixer with rate and cc. pulse control


Can you articulate your requirements in more detail? 
Got Specs?