System and method for position control of a mechanical piston in a pump

• US 20070128048A1
• Filed: 11/20/2006
• Published: 06/07/2007
• Est. Priority Date: 12/02/2005
• Status: Active Grant

• Current Assignee: Entegris Incorporated
• Original Assignee: Entegris Incorporated
• Inventors: Cedrone, James, Gonnella, George, Gashgaee, Iraj
• Granted Patent: US 8,083,498 B2
• Time in Patent Office: Days
• US Class Current: 417/44.100
• CPC Class Codes: F04B 17/03 driven by electric motors
• CPC Class Codes: F04B 25/00 Multi-stage pumps
• CPC Class Codes: F04B 49/065 and making use of computers
• CPC Class Codes: Y10S 417/90 Slurry pumps, e.g. concrete

Abstract

Embodiments of the systems and methods disclosed herein utilize a brushless DC motor (BLDCM) to drive a single-stage or a multi-stage pump in a pumping system for real time, smooth motion, and extremely precise and repeatable position control over fluid movements and dispense amounts, useful in semiconductor manufacturing. The BLDCM may employ a position sensor for real time position feedback to a processor executing a custom field-oriented control scheme. Embodiments of the invention can reduce heat generation without undesirably compromising the precise position control of the dispense pump by increasing and decreasing, via a custom control scheme, the operating frequency of the BLDCM according to the criticality of the underlying function(s). The control scheme can run the BLDCM at very low speeds while maintaining a constant velocity, which enables the pumping system to operate in a wide range of speeds with minimal variation, substantially increasing dispense performance and operation capabilities.

Claims

1. A pumping system comprising:

a pump;

a brushless DC motor driving a dispense pump residing in said pump;

a computer-readable medium carrying software instructions for controlling said pump; and

a processor communicatively coupled to said computer-readable medium and said pump, wherein said software instructions are executable by said processor to control said brushless DC motor in accordance with a control scheme.

2. The pumping system of claim 1, wherein said dispense pump is a piston displacement pump comprising:

a dispense chamber;

a piston;

a dispense stage diaphragm positioned between said dispense chamber and said piston; and

a lead screw connecting said piston and said and brushless DC motor.

3. The pumping system of claim 2, further comprising a position sensor coupled to said brushless DC motor and in communication with said processor for providing real time position feedback of said piston.

4. The pumping system of claim 3, wherein said position sensor is internally or externally coupled to said brushless DC motor.

5. The pumping system of claim 3, wherein said position sensor is operable to provide measurements that facilitate control of said piston at 0.045 degrees of rotation.

6. The pumping system of claim 3, wherein said position sensor is a 1000, 2000 or 8000 line encoder.

7. The pumping system of claim 1, wherein said control scheme is configured to minimize heat generation by said brushless DC motor during operation of said dispense pump.

8. The pumping system of claim 1, wherein said control scheme is configured to run said brushless DC motor at least two controller frequencies during a single cycle.

9. The pumping system of claim 8, wherein said at least two controller frequencies comprises a first frequency for a dispense portion of said single cycle.

10. The pumping system of claim 9, wherein said first frequency is at 30 kHz.

11. The pumping system of claim 1, wherein said control scheme is configured to provide a desirable dispense profile characterized by smoothness of a pressure signal.

12. The pumping system of claim 1, wherein said control scheme is configured to run said brushless DC motor at a first frequency during dispensing and drop down to a second frequency during non-dispensing operations.

13. The pumping system of claim 1, wherein said pump is a single-stage pump or a multi-stage pump.

14. A pump comprising:

a dispense pump, wherein said dispense pump is a piston displacement pump comprising;

a dispense chamber;

a piston;

a dispense stage diaphragm positioned between said dispense chamber and said piston;

a brushless DC motor; and

a lead screw connecting said piston and said and brushless DC motor;

wherein said brushless DC motor is controlled by software instructions embodied on a computer-readable medium and executable by a processor implementing a control scheme and wherein said processor is communicatively coupled to said computer-readable medium and said pump.

15. The pump of claim 14, further comprising a position sensor coupled to said brushless DC motor and in communication with said processor for providing real time position feedback of said piston.

16. The pump of claim 15, wherein said position sensor is internally or externally coupled to said brushless DC motor.

17. The pump of claim 15, wherein said position sensor is operable to provide measurements that facilitate control of said piston at 0.045 degrees of rotation.

18. The pump of claim 14, wherein said control scheme is configured to minimize heat generation by running said brushless DC motor at least two controller frequencies during a single cycle, wherein said at least two controller frequencies comprises a first frequency for a dispense portion of said single cycle.

19. A method of controlling position of a mechanical piston in a pump, comprising:

connecting said mechanical piston to a brushless DC motor;

employing a position sensor for real time position feedback of said mechanical piston; and

controlling an operating frequency of the control loop of said brushless DC motor according to software instructions implementing a control scheme,

wherein said software instructions are embodied on a computer-readable medium and executable by a processor,

wherein said processor is communicatively coupled to said computer-readable medium and said pump,

wherein said control scheme increases said operating frequency of said brushless DC motor to enhance position control of said mechanical piston during dispensing and decreases said operating frequency of said brushless DC motor during non-dispensing operations to minimize heat generation.

20. The method of claim 19, further comprises increasing said operating frequency of said brushless DC motor to about 30 kHz during a dispense portion of a cycle.

21. The method of claim 19, further comprises decreasing said operating frequency of said brushless DC motor to about 10 kHz during a non-dispense portion of a cycle.

22. The method of claim 19, wherein said pump is a single-stage or a multi-stage pump.