Patent ID: 7686499

Claim:
A control system for mixing at least two materials in a physical system, comprising: a first tank; at least two actuators, each actuator being operable to introduce a material into the first tank to form a first mixture; a first density sensor operable to provide a sensed density output of the first mixture; and a controller to control the at least two actuators to obtain a density of the first mixture and a volume flow rate of the first mixture, wherein the density is controlled independently from the volume flow rate, the controller comprising: a flow modulator component to output control commands to the two actuators based on a commanded combined mass flow rate of the materials into the first tank and based on a commanded combined volume flow rate of the materials into the first tank, a density controller component to determine the commanded combined volume flow rate of the materials into the first tank, and a density observer to determine a first estimation of a disturbance and to determine an estimation of the density of the first mixture based on the estimation of the density of the first mixture, based on the sensed density output, based on the commanded combined mass flow rate of the materials into the first tank, and based on a model of the first tank, wherein the density controller component determines the commanded combined volume flow rate of the materials into the first tank based on a commanded density input, based on the estimation of the density of the first mixture, and based on the first estimation of the disturbance.