Methods for volumetrically controlling a mixing apparatus

Abstract

Methods of controlling a volumetric ratio of a material to total materials in a mixing vessel are provided. In various embodiments, the methods may comprise: estimating the volumetric ratio of the material to the total materials in the mixing vessel and an output flowrate of the material from the mixing vessel using a volumetric ratio observer; dynamically recomputing the commanded input flowrate of the material based on outputs of the volumetric ratio observer using a flow regulator; and adjusting an input valve of the material based on the commanded input flowrate of the material using a flow modulator. The mixing vessel may include a first mixing vessel partially separated from a second mixing vessel. In this case, a height of the total materials in the second mixing vessel may be estimated using a height observer.

Description

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 depicts a mixing apparatus comprising two mixing vessels separated by a weir.

FIG. 2 is a state block diagram of an embodiment of a physical system and a flow modulator being used to volumetrically mix components in the mixing vessels shown in FIG. 1.

FIG. 3A is a state block diagram of an embodiment of a portion of a volumetric ratio observer for use with a single mixing vessel.

FIG. 3B is a state block diagram of another embodiment of a portion of a volumetric ratio observer for use with two mixing vessels.

FIG. 4 is a state block diagram of an embodiment of a control system for controlling the mixing apparatus depicted in FIG. 1.

FIG. 5 is a state block diagram of another embodiment of a control system for controlling the mixing apparatus depicted in FIG. 1.

FIG. 6 is a state block diagram of yet another embodiment of a control system for controlling the mixing apparatus depicted in FIG. 1.

FIG. 7 is a state block diagram of yet another embodiment of a portion of a volumetric ratio observer for use with mixing three components utilizing a two-vessel mixing apparatus.

FIG. 8 is a state block diagram of still another embodiment of a volumetric ratio observer for use with mixing three components utilizing a two-vessel mixing apparatus.

FIG. 9 shows how a process for mixing multiple components in a mixing apparatus comprising a single vessel or tank can be controlled using a volumetric ratio mixing control scheme.

FIG. 10 shows results obtained from systems according to FIGS. 2-9.

FIG. 11 shows yet another embodiment, with a different implementation of the disclosed volumetric control ideas.

Claims

1. A method of controlling a volumetric ratio of a material to total materials in a mixing vessel, comprising: estimating the volumetric ratio of the material to the total materials in the mixing vessel and an output flowrate of the material from the mixing vessel using a volumetric ratio observer;dynamically recomputing the commanded input flowrate of the material based on outputs of the volumetric ratio observer using a flow regulator; andadjusting an input valve of the material based on the commanded input flowrate of the material using a flow modulator.

2. The method of claim 1, wherein the mixing vessel comprises a first mixing vessel partially separated from a second mixing vessel.

3. The method of claim 2, further comprising estimating a height of the total materials in the second mixing vessel using a height observer.

4. The method of claim 2, wherein the volumetric ratio observer is used to estimate the volumetric ratio of the material to the total materials in the first mixing vessel and an output flowrate of the material from the first mixing vessel.

5. The method of claim 3, further comprising: estimating a total volumetric disturbance flowrate using the height observer which has the following inputs: a measured height of the total materials in the second mixing vessel; a commanded input flowrate of the total materials; and a measured output flowrate of the total materials from the second mixing vessel; andestimating a volumetric disturbance flowrate of the material using the volumetric ratio observer, which has the following inputs: a measured input flowrate of the material and a commanded input flowrate of the material,wherein the flow regulator has the following inputs: the estimated volumetric ratio of the material to the total materials in the first mixing vessel; the estimated volumetric disturbance flowrate of the material; and the estimated output flowrate of the material from the first mixing vessel.

6. The method of claim 2, wherein the volumetric ratio observer has the total volumetric disturbance flowrate as another input, and wherein it is also used to estimate the volume of the total materials in the first mixing vessel.

7. The method of claim 1, wherein the total materials comprise water and cement.

8. The method of claim 2, wherein the height observer comprises a PI controller.

9. The method of claim 8, wherein the height observer further comprises an Integral controller coupled to the PI controller.

10. The method of claim 2, wherein the volumetric ratio observer comprises first and second Integral controllers.

11. The method of claim 3, further comprising estimating an output flowrate of the total materials from the first mixing vessel using a weir flow observer having the following inputs: the estimated height of the total materials in the second mixing vessel; the measured height of the total materials in the second mixing vessel; and the measured output flowrate of the total materials from the second mixing vessel.

12. The method of claim 11, wherein the weir flow observer comprises a PI controller.

13. The method of claim 12, wherein the weir flow observer further comprises an Integral controller coupled to the PI controller.

14. The method of claim 3, further comprising computing a commanded output flowrate of the total materials from the first mixing vessel using a state feedback controller having the following inputs: a commanded height of the total materials in the second mixing vessel; the estimated height of the total materials in the second mixing vessel; and the commanded output flowrate of the total materials from the second mixing vessel.

15. The method of claim 14, further comprising dynamically recomputing the commanded input flowrate of the total materials using a second portion of a flow regulator having the following inputs: the commanded output flowrate of the total materials from the first mixing vessel; the estimated output flowrate of the total materials from the first mixing vessel; and the estimated volumetric disturbance flowrate.

16. The method of claim 15, further comprising adjusting an input valve for a second material based on the commanded input flowrate of the total materials and the commanded input flowrate of the material using the flow modulator.

17. The method of claim 1, being implemented by a computerized system or by hardware.

18. The method of claim 1, wherein the total materials comprise a fluid and a gas-transported dry material.

19. A method of controlling a volumetric ratio of a material to total materials in a first mixing vessel that is partially separated from a second mixing vessel, comprising: estimating the volumetric ratio of the material to the total materials in the second mixing vessel, an output flowrate of the material from the first mixing vessel, and a volumetric disturbance flowrate of the material using a volumetric ratio observer having the following inputs: a commanded input flowrate of the material and a measured input flowrate of the material;computing a commanded output flowrate of the material from the first mixing vessel using a state feedback controller having the following inputs: a commanded volumetric ratio of the material to the total materials in the second mixing vessel and the estimated volumetric ratio of the material to the total materials in the second mixing vessel;dynamically recomputing the commanded input flowrate of the material using a flow regulator having the following inputs: the estimated input flowrate error of the material and the estimated output flowrate of the material from the first mixing vessel; andadjusting an input valve of the material based on the commanded input flowrate of the material using a flow modulator.

20-32. (canceled)

33. A method of controlling a volumetric ratio of a material to total materials in a first mixing vessel that is partially separated from a second mixing vessel, comprising: estimating a total volumetric disturbance flowrate, the volumetric ratio of the material to the total materials in the first mixing vessel, and an output flowrate of the material from the first mixing vessel using a volumetric ratio observer having the following inputs: a measured height of the total materials in the second mixing vessel; a measured input flowrate of the material; and a commanded input flowrate of a second material that is also being fed to the first mixing vessel;dynamically recomputing the commanded input flowrate of the material using a flow regulator having the following inputs: a commanded volumetric ratio of the material to the total materials in the first mixing vessel; an estimated volumetric ratio of the material to the total materials in the first mixing vessel; and the estimated output flowrate of the material from the first mixing vessel; andadjusting an input valve of the material based on the commanded input flowrate of the material using a flow modulator.

34-55. (canceled)