Method and apparatus for measuring and controlling solids composition of a magnetorheological fluid
View Patent ↗A system for dispensing magnetorheological fluid to an MR finishing machine includes a pump for pressurizing the system; a first magnetic valve for regulating MR fluid flow by magnetically varying the structure and apparent viscosity of the fluid through a first flow passage; a similar second magnetic valve magnetically controlling a second flow passage in line with the first valve and flow passage; a pressure sensor disposed between the first and second valves; and an electronic control means. MR fluid flow through the system is controlled to a predetermined flow rate solely by the first valve. When the second valve is deactivated, a reference pressure is determined and saved. When the second valve is activated, a second pressure is determined and saved. From the pressure difference, the solids concentration of the fluid is determined, and a computer algorithm adds a calculated amount of water to the fluid reservoir as needed. The second valve is deactivated, and the measurement cycle is repeated, as may be desired.
1. A system for measuring solids concentration in a magnetorheological fluid, comprising:
a) means for passing said magnetorheological fluid through said system at a fixed flow rate;
b) an inline pressure sensor disposed downstream of said means for passing;
c) a magnetic valve disposed downstream of said inline pressure sensor;
d) control means for controlling the action of said magnetic valve between first and second predetermined states of actuation;
e) computer means connected to said inline pressure sensor for obtaining first and second inline pressure measurements corresponding to said first and second states of valve actuation, and for using the difference between said first and second pressure measurements to calculate solids concentration in said magnetorheological fluid.
2. A system in accordance with claim 1 wherein said first predetermined state is a de-energized state and said second predetermined state is an energized state.
3. A system in accordance with claim 1 wherein said means for passing includes a centrifugal pump, a flowmeter, and a flow controller.
4. A system in accordance with claim 1 for controlling said calculated solids concentration to a predetermined aim, comprising:
a) a reservoir for holding a supply of said magnetorheological fluid and for supplying said fluid to said pump means;
b) means for using said calculated solids concentration to determine an amount of diluent to be added to said reservoir to adjust said calculated solids concentration to said predetermined aim concentration; and
c) means for adding said amount of diluent to said fluid in said reservoir.
5. A system for magnetorheological finishing of a substrate surface by impinging a magnetically stiffened magnetorheological fluid thereupon, comprising:
a) a carrier wheel disposed adjacent said substrate surface for creating a work zone therebetween;
b) nozzle means for dispensing said magnetorheological fluid onto said carrier wheel for transport into said work zone;
c) magnet means adjacent said carrier wheel for creating a magnetic field to stiffen said fluid within said work zone;
d) a fluid delivery system for receiving spent magnetorheological fluid from said carrier wheel, reconstituting said fluid, and supplying said reconstituted fluid to said nozzle means,
wherein said fluid delivery system includes means for measuring and controlling solids concentration in said magnetorheological fluid.
6. A system in accordance with claim 5 wherein said means for measuring and controlling solids concentration in said magnetorheological fluid comprises:
a) means for passing said magnetorheological fluid through said system at a fixed flow rate;
b) an inline pressure sensor disposed downstream of said means for passing;
c) a magnetic valve disposed downstream of said inline pressure sensor;
d) control means for controlling the action of said magnetic valve between first and second predetermined states of actuation;
e) computer means connected to said inline pressure sensor for obtaining first and second inline pressure measurements corresponding to said first and second states of valve actuation, and for using the difference between said first and second pressure measurements to calculate solids concentration in said magnetorheological fluid;
f) a reservoir for receiving spent magnetorheological fluid from said carrier wheel and for supplying said fluid to said means for passing;
g) means for using said calculated solids concentration to determine an amount of diluent to be added to said reservoir to adjust said calculated solids concentration to a predetermined aim concentration; and
h) means for adding said amount of diluent to said fluid in said reservoir.
7. A method for measuring solids concentration in a magnetorheological fluid, comprising the steps of:
a) providing a measurement system including means for passing said magnetorheological fluid through said system at a fixed flow rate, an inline pressure sensor disposed downstream of said means for passing, a magnetic valve disposed downstream of said inline pressure sensor, control means for controlling the action of said magnetic valve between first and second predetermined states of actuation, and computer means connected to said inline pressure sensor for obtaining first and second inline pressure measurements corresponding to said first and second states of valve actuation, and for using the difference between said first and second pressure measurements to calculate solids concentration in said magnetorheological fluid;
b) delivering said magnetorheological fluid through said system;
c) determining a reference pressure value when said magnetic valve is in said first predetermined state;
d) determining a test pressure value when said magnetic valve is in said second predetermined state;
e) calculating a difference between said test and reference pressure values;
h) providing a system calibration curve of solids concentration as a function of difference between said test and reference pressure values; and
i) applying said difference to said system calibration curve to determine said solids concentration in said magnetorheological fluid.
8. A method in accordance with claim 7 for controlling said solids concentration to a predetermined aim value, comprising the steps of:
a) providing a reservoir for supplying said magnetorheological fluid to said means for passing, and means for adding diluent to said magnetorheological fluid in said reservoir;
b) using said calculated solids concentration to determine an amount of diluent to be added to said reservoir to adjust said calculated solids concentration to said predetermined aim value; and
c) adding said amount of diluent to said fluid in said reservoir.