U.S. patent application number 11/036782 was filed with the patent office on 2005-08-18 for drive technology for peristaltic and rotary pumps.
Invention is credited to Bach, David T..
Application Number | 20050180856 11/036782 |
Document ID | / |
Family ID | 36678127 |
Filed Date | 2005-08-18 |
United States Patent
Application |
20050180856 |
Kind Code |
A1 |
Bach, David T. |
August 18, 2005 |
Drive technology for peristaltic and rotary pumps
Abstract
A method and system for controlling a rotary pump where a rotary
pump can be coupled to a stepper motor, and the stepper motor can
be controlled with micro- or nano-stepping accuracy using a
processor controlled drive system. The processor controlled drive
system moves the stepper motor according to a predetermined move
profile; this causes the rotary pump to dispense a precision amount
of fluid. The rotary pump can be a peristaltic pump or any other
type of pump. The rotary pump can be coupled to the stepper motor
through a reduction gear with a reduction ratio of 2:1 or similar.
The stepper motor can be mechanically coupled to a rotational
position encoder so that a measure of the rotation position can be
fed back to the processor. The processor can cause the stepper
motor to interpolate between pulse positions of the encoder.
Inventors: |
Bach, David T.; (Ellicott
City, MD) |
Correspondence
Address: |
Clifford Kraft
320 Robin Hill Dr.
Naperville
IL
60540
US
|
Family ID: |
36678127 |
Appl. No.: |
11/036782 |
Filed: |
January 14, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60536291 |
Jan 14, 2004 |
|
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60537777 |
Jan 20, 2004 |
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Current U.S.
Class: |
417/42 ;
417/410.3; 417/474 |
Current CPC
Class: |
F04B 43/12 20130101;
F04B 17/03 20130101; F04B 9/02 20130101; F04B 2203/0213 20130101;
F04B 43/1253 20130101; F04B 13/00 20130101; F04B 49/065 20130101;
F04B 2201/1208 20130101; F04B 43/0081 20130101 |
Class at
Publication: |
417/042 ;
417/410.3; 417/474 |
International
Class: |
F04B 049/00; F04B
017/00 |
Claims
I claim:
1. A method of controlling a rotary pump comprising the steps of:
coupling a rotary pump to a stepper motor, wherein said stepper
motor is controlled with micro- or nano-stepping accuracy using a
processor controlled drive system; causing said processor
controlled drive system to move said stepper motor according to a
predetermined move profile, wherein said rotary pump dispenses a
precision amount of fluid.
2. The method of claim 1 wherein said rotary pump is a peristaltic
pump.
3. The method of claim 1 further comprising the step of causing
said rotary pump to be coupled to said stepper motor through a
reduction gear.
4. The method of claim 3 wherein said reduction gear is 2:1 or
greater.
5. The method of claim 1 further comprising sensing a rotational
position of said stepper motor using a rotary encoder.
6. The method of claim 5 wherein said processor interpolates
between positions of said rotary encoder.
7. The method of claim 1 wherein said stepper motor has a
resolution of at greater than 70,000 steps per revolution.
8. The method of claim 1 further comprising causing said stepper
motor to operate at a plurality of different resolutions during a
dispense cycle.
9. The method of claim 8 wherein said stepper motor operates at
both 1000 steps per revolution and at least 10,000 steps per
revolution during a dispense cycle.
10. An apparatus for dispensing fluid comprising: a rotary pump; a
stepper motor coupled to said rotary pump; a nano-stepping drive
system under control of a processor driving said stepper motor; a
move profile stored in said processor for causing said stepper
motor to move said rotary pump a predetermined amount to dispense a
predetermined amount of fluid.
11. The apparatus of claim 10 wherein said rotary pump is a
peristaltic pump.
12. The apparatus of claim 10 further comprising a rotary encoder
coupled to said stepper motor.
13. The apparatus of claim 12 wherein said processor causes said
stepper motor to interpolate between positions of said rotary
encoder.
14. The apparatus of claim 10 further comprising a reduction gear
between said rotary pump and said stepper motor.
15. The apparatus of claim 14 wherein said reduction gear is 2:1 or
greater.
16. A method for precision fluid dispensing comprising the steps
of: causing a processor to control a stepping position of at least
one stepper motor; coupling a stepper motor driver for driving a
stepper motor to said processor and to said stepper motor; coupling
a peristaltic pump mechanically to said stepper motor, said
processor causing said peristaltic pump to rotate with a stepping
precision of at least 10,000 steps per revolution.
17. The method of claim 16 wherein said stepping precision is
greater than 125,000 steps per revolution.
18. The method of claim 16 further comprising placing a reduction
gear between said stepper motor and said peristaltic pump.
19. The method of claim 16 further comprising coupling an optical
encoder mechanically to said stepper motor, said optical encoder
electrically also coupled to said processor.
20. The method of claim 19 wherein said processor causes said
stepper motor to interpolate between positions of said optical
encoder.
Description
[0001] This application is related to and claims priority from U.S.
provisional patent applications 60/536,291 file Jan. 14, 2004 and
60/537,777 file Jan. 20, 2004. Applications 60/536,291 and
60/537,777 are hereby incorporated by reference.
BACKGROUND
[0002] 1. Field of the Invention
[0003] The present invention relates generally to the field of
fluid pumps and more specifically to the use of a multiple
resolution stepping drive for a peristaltic or rotary pump.
[0004] 2. Description of the Prior Art
[0005] Peristaltic pumps have a unique advantage over other pumps
in that they can be cleaned by merely removing the tubing and
discarding it. New tubing is rapidly loaded making product
changeover quite easy and contamination free. Also, the fluid
shearing effect on tubing, known with other pumps, does not exist
with peristaltic pumps. This protects products being pumped such as
fluids containing fragile blood cells.
[0006] A major problem with peristaltic pumps is precision and
accuracy. This is true even when stated accuracy is said to be some
fixed value, for example +/-0.5%. Over a period of a product run,
the tubing and other accessories can change resulting in a loss of
precision, because the precision is directly related to the tube
diameter as well as the rotor speed.
SUMMARY OF THE INVENTION
[0007] The present invention relates to a method and system for
controlling a rotary pump where a rotary pump can be coupled to a
stepper motor, and the stepper motor can be controlled with micro-
or nano-stepping accuracy using a processor controlled drive
system. The processor controlled drive system moves the stepper
motor according to a predetermined move profile; this causes the
rotary pump to dispense a precision amount of fluid. The rotary
pump can be a peristaltic pump or any other type of pump. The
rotary pump can be coupled to the stepper motor through a reduction
gear with a reduction ratio of 2:1, 7:1 or similar. The stepper
motor can have an internal rotational encoder, or it be
mechanically coupled to a rotational position encoder so that a
measure of the rotation position can be fed back to the processor.
The processor can cause the stepper motor to interpolate between
pulse positions of the encoder.
[0008] Using the present invention, it is possible to achieve a
stepping resolution of at least 125,000 steps per revolution. With
a 2:1 reduction gear, it is possible to achieve as high as 250,000
steps per revolution. The present invention allows the stepper
motor to operate at different resolutions during a dispense cycle.
An example might be 1000 steps per revolution which is then
switched to 10,000 steps per revolution (or much greater) depending
upon the needs of the application.
DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 shows a block diagram of a stepper motor pump drive
system.
[0010] FIG. 2 shows a flowchart for a dispense algorithm.
[0011] FIG. 3 shows a block diagram of a stepper motor pump driver
attached to a peristaltic pump.
[0012] FIG. 4 is a table of stepping resolutions.
[0013] Several figures and illustrations have been presented to aid
in understanding the present invention. The scope of the present
invention is not limited to the figures.
DESCRIPTION OF THE INVENTION
[0014] The present invention relates to the use of a multiple
resolution stepping motor to drive a peristaltic or rotary pump to
dispense fluids.
[0015] A conventional peristaltic fluid pump (or alternatively any
rotary pump) benefits by using a multi-resolution stepping drive to
increase precision and hence overall system dispensing accuracy. A
stepper motor such as an "Oriental" motor or equivalent can achieve
micro- or nano-stepping resolution if properly driven. This type of
motor can then be directly attached to a peristaltic pump. The
improved control and resolution of the stepper motor allows the
peristaltic pump to dispense fluids with an accuracy approaching
that of a linear pump and allows possible tubing wear
compensation.
[0016] A pump drive system is shown in FIG. 1. This is the system
described in U.S. Pat. No. 6,739,478 by Bach et al. This system
uses a microprocessor coupled with a position feedback system to
determine the position of the pump. The position feedback is
optional since the accuracy of the micro- or nano-stepping motor
can be such that direct rotational position feedback may not be
necessary. U.S. Pat. No. 6,739,478 is hereby incorporated by
reference.
[0017] A peristaltic pump system can select and use any of the 16
resolutions in this embodiment of on-the-fly to assist in enhancing
precision. FIG. 4 shows a table of stepping resolutions that can be
used. The motor stepping rate can start at 1000 steps per
revolution, and then for example, switch to 10,000 steps per
revolution to improve precision as a dispensing goal (final
dispensed quantity) is approached. A gear head can be optionally
used to further improve precision. For example, a VICI M6 multiple
piston pump head could be run with a 2:1 gear head on a 16 step
setting to achieve 250,000 steps per revolution. The same system
could also run at 1000 steps per revolution. This type of stepper
drive, with or without a gear head, allows greater drive range and
capability that can be currently found on peristaltic pumps.
[0018] When an Oriental "Alpha" series pump is used (for example
with a 110 V. driver), the pump can be rotated at 500, 1000, 5000
and 10,000 steps per revolution. With a reduction gear of 7:1, a
maximum precision of around 70,000 steps per revolution can be
achieved.
[0019] FIG. 1 shows a block diagram of possible electronics that
could be used to drive a peristaltic pump. A micro- or nano-step
motor can be driven with suitable drive electronics known in the
art under the control of a microprocessor. The microprocessor can
be any processor of any bit width and can also be a
microcontroller. An example processor is a 16 bit processor made by
Intel called the 80196. The processor can optionally couple into a
CAN bus, an RS-232 interface, and can contain RAM, ROM and disk
storage. Optional rotational position feedback can be used through
an A/D converter if desired.
[0020] FIG. 2 shows a flowchart that can be used for a sample
dispense. In this algorithm, a peristaltic (or any other) pump can
be moved by creating a move profile. Here a Gaussian move profile
is used. A step table is created that relates to accelerations, and
the motor is moved according to the table.
[0021] FIG. 3 shows a block diagram of a stepper motor with
processor controlled driver coupled through an optional reduction
gear to a peristaltic pump. Typical drive electronics are sold
under the trade name of ONE PUMP by Scientific Products and Systems
of Baltimore Md. This electronics, as shown in FIG. 3, can be used
to drive both linear and rotary pumps. This electronics also
includes features such as the ability to separately control a
nozzle, linking of multiple pumps on a CAN bus, and control of
pumps by programmable logic controllers (PLCs).
[0022] A Renishaw rotary 4096 pulse per revolution encoder can be
optionally interfaced to the controller to provide around 0.08
degree resolution (also some motors have internal revolution
encoders). Stepping motor steps can be used to interpolate between
encoder signals allowing for finer resolution (settings above 6 in
FIG. 4). A home signal can be optionally incorporated so that
counters can be calibrated and peristaltic pump rollers
synchronized.
[0023] Several illustrations and descriptions have been used to aid
in the understanding of the present invention. One of skill in the
art will recognize that many variations and changes are possible.
All such variations and changes are within the scope of the present
invention.
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