System and method for position control of a mechanical piston in a pump
View Patent ↗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.
1. A pumping system comprising:
a pump;
a brushless DC motor driving a dispense pump residing in said pump, wherein said dispense pump comprises an inlet and an outlet;
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 for operation of said dispense pump routing fluid from said inlet to said outlet;
wherein said control scheme is configured to run said brushless DC motor at a first frequency during dispensing and run said brushless DC motor at a second frequency lower than the first frequency during non-dispensing operations.
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 real time feedback of said brushless DC motor's position to said processor such that said processor is able to control 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 provide a desirable dispense profile characterized by smoothness of a pressure signal.
9. The pumping system of claim 1 , wherein said pump is a single-stage pump or a multi-stage pump.
10. A pump comprising:
a dispense pump, wherein said dispense pump is a piston displacement pump comprising:
an inlet;
an outlet;
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 for operation of said dispense pump routing fluid from said inlet to said outlet and wherein said processor is communicatively coupled to said computer-readable medium and said pump;
wherein said control scheme is configured to run said brushless DC motor at a first frequency during dispensing and run said brushless DC motor at a second frequency lower than the first frequency during non-dispensing operations.
11. The pump of claim 10 , 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.
12. The pump of claim 11 , wherein said position sensor is internally or externally coupled to said brushless DC motor.
13. The pump of claim 11 , wherein said position sensor is operable to provide real time feedback of said brushless DC motor's position to said processor such that said processor is able to control said piston at 0.045 degrees of rotation.