초록 ▼

A method for mixing at least two materials is provided. The method comprises introducing the at least two materials into a physical system and combining the at least two materials to form a mixture thereof. The method also comprises independently controlling a desired characteristic of the mixture a

A method for mixing at least two materials is provided. The method comprises introducing the at least two materials into a physical system and combining the at least two materials to form a mixture thereof. The method also comprises independently controlling a desired characteristic of the mixture and a desired parameter of the physical system, wherein the controlling is based in part on estimating a disturbance, wherein the estimating the disturbance is based on processing an error term determined by subtracting a modeled parameter of the physical system from a corresponding sensed parameter of the physical system.

대표청구항 ▼

What is claimed is: 1. 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 den

What is claimed is: 1. 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. 2. The control system of claim 1, wherein the density observer produces the estimate of the density of the first mixture based on subtracting the estimate of the density of the first mixture from the sensed density output to determine a density error term, based on processing the density error term with a first proportional-integral (PI) controller, based on summing the output of the first proportional-integral controller with the commanded combined mass flow rate of the materials into the first tank to determine a first sum, and based on processing the first sum through a model of the first tank and wherein the first estimation of the disturbance is output from the first proportional-integral controller. 3. The control system of claim 1, wherein the flow modulator component comprises a first flow modulator to output control commands to a first actuator and a second flow modulator to output control commands to a second actuator. 4. The control system of claim 1 further comprising: a second tank, wherein the first tank is positioned to overflow the first mixture into the second tank to form a second mixture; and a first height sensor to provide a sensed height output of the second mixture in the second tank, wherein the controller further comprises: a height controller component to determine the commanded rate of flow of the materials into the first tank, a height observer to determine a second estimation of the disturbance and to determine an estimation of the height of the second mixture in the second tank based on the estimation of the height of the second mixture, based on the sensed height of the second mixture, based on the commanded combined volume flow rate of the materials into the first tank, and based on a model of the second tank, wherein the height controller determines the commanded combined volume flow rate of the materials into the first tank based on a commanded height input, based on the estimation of the height of the second mixture in the second tank, and based on the second estimation of the disturbance. 5. The control system of claim 4, wherein the height observer produces the estimate of the height of the second mixture in the second tank based on subtracting the estimate of the height of the second mixture from the sensed height output to determine a height error term, based on processing the height error term with a second proportional-integral (PI) controller, based on summing the output of the second proportional-integral controller with the commanded combined volume flow rate of the materials into the first tank to determine a second sum, and based on processing the second sum through a model of the second tank and wherein the second estimation of the disturbance is output from the second proportional-integral controller. 6. The control system of claim 4, wherein the second estimation of the disturbance is based on processing a second error term determined by subtracting a second modeled parameter of the physical system from a corresponding second sensed parameter of the physical system. 7. The control system of claim 6, wherein processing the second error term comprises multiplying the second error term with a second proportional constant to determine a second proportional term, integrating the second error term to determine a second integral term, and summing the second proportional term and the second integral term. 8. The control system of claim 4, wherein the second estimation of the disturbance takes account of at least one of an inaccuracy in a design estimate of the second modeled parameter of the physical system and an unmeasured parameter of the physical system. 9. The control system of claim 4, further comprising a second density sensor operable to provide a sensed density of the second mixture, wherein the controller further controls the at least two actuators based at least in part on the sensed density of the second mixture. 10. The control system of claim 9, further comprising a second density observer to determine an estimate of the density of the second mixture based on the sensed density of the second mixture, wherein the controller controls the at least two actuators based at least in part on the estimate of the density of the second mixture. 11. The control system of claim 4, further comprising a second height sensor operable to provide a sensed height output of the first mixture in the first tank, wherein the controller further controls the at least two actuators based at least in part on the sensed height output of the second height sensor. 12. The control system of claim 11, further comprising a second height observer to determine an estimate of the height of the first mixture in the first tank based on the sensed height output of the second height sensor, wherein the controller controls the at least two actuators based at least in part on the estimate of the height of the first mixture in the first tank. 13. The control system of claim 1, wherein the two actuators introduce a dry cement material and water into the first tank, wherein the first mixture is a cement slurry, and further comprising an outflow pump in fluid communication with a well bore to provide the cement slurry to promote a well bore cementing operation. 14. The control system of claim 1, wherein the actuators are selected from the group consisting of valves, screw feeders, augurs, and elevators. 15. The control system of claim 1, wherein the first estimation of the disturbance is based on processing a first error term determined by subtracting a first modeled parameter of the physical system from a corresponding first sensed parameter of the physical system. 16. The control system of claim 15, wherein processing the first error term comprises multiplying the first error term with a first proportional constant to determine a first proportional term, integrating the first error term to determine a first integral term, and summing the first proportional term and the first integral term. 17. The control system of claim 15, wherein the first estimation of the disturbance takes account of at least one of an inaccuracy in a design estimate of the first modeled parameter of the physical system and an unmeasured parameter of the physical system. 18. The control system of claim 1, wherein the controller decouples a volumetric flow rate parameter. 19. The control system of claim 1, wherein the controller decouples a mass flow rate parameter. 20. The control system of claim 1, further comprising a stirrer to promote blending of the first mixture in the first tank.