CA2171716C - Flow-metered pumping with load compensation system and method - Google Patents
Flow-metered pumping with load compensation system and methodInfo
- Publication number
- CA2171716C CA2171716C CA002171716A CA2171716A CA2171716C CA 2171716 C CA2171716 C CA 2171716C CA 002171716 A CA002171716 A CA 002171716A CA 2171716 A CA2171716 A CA 2171716A CA 2171716 C CA2171716 C CA 2171716C
- Authority
- CA
- Canada
- Prior art keywords
- speed
- pump
- motor
- pump motor
- load
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 238000005086 pumping Methods 0.000 title claims abstract description 41
- 238000000034 method Methods 0.000 title claims description 14
- 239000007788 liquid Substances 0.000 claims description 14
- 239000000126 substance Substances 0.000 claims description 7
- 238000005406 washing Methods 0.000 claims description 5
- 230000004913 activation Effects 0.000 claims 7
- 238000004140 cleaning Methods 0.000 claims 3
- 230000001105 regulatory effect Effects 0.000 claims 1
- 230000009467 reduction Effects 0.000 abstract description 4
- 230000000694 effects Effects 0.000 abstract description 2
- 239000003570 air Substances 0.000 description 8
- 238000005259 measurement Methods 0.000 description 6
- 230000009977 dual effect Effects 0.000 description 5
- 239000012530 fluid Substances 0.000 description 5
- 238000010586 diagram Methods 0.000 description 4
- 230000001133 acceleration Effects 0.000 description 2
- 238000004891 communication Methods 0.000 description 2
- 238000005070 sampling Methods 0.000 description 2
- 101100242924 Bacillus subtilis (strain 168) pbpF gene Proteins 0.000 description 1
- 235000001537 Ribes X gardonianum Nutrition 0.000 description 1
- 235000001535 Ribes X utile Nutrition 0.000 description 1
- 235000016919 Ribes petraeum Nutrition 0.000 description 1
- 244000281247 Ribes rubrum Species 0.000 description 1
- 235000002355 Ribes spicatum Nutrition 0.000 description 1
- 101100242909 Streptococcus pneumoniae (strain ATCC BAA-255 / R6) pbpA gene Proteins 0.000 description 1
- 239000012080 ambient air Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 101150058012 mrcA gene Proteins 0.000 description 1
- 229920000136 polysorbate Polymers 0.000 description 1
- 101150105325 ponA gene Proteins 0.000 description 1
- 230000001360 synchronised effect Effects 0.000 description 1
Classifications
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D7/00—Control of flow
- G05D7/06—Control of flow characterised by the use of electric means
- G05D7/0617—Control of flow characterised by the use of electric means specially adapted for fluid materials
- G05D7/0629—Control of flow characterised by the use of electric means specially adapted for fluid materials characterised by the type of regulator means
- G05D7/0676—Control of flow characterised by the use of electric means specially adapted for fluid materials characterised by the type of regulator means by action on flow sources
- G05D7/0682—Control of flow characterised by the use of electric means specially adapted for fluid materials characterised by the type of regulator means by action on flow sources using a plurality of flow sources
-
- D—TEXTILES; PAPER
- D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
- D06F—LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
- D06F39/00—Details of washing machines not specific to a single type of machines covered by groups D06F9/00 - D06F27/00
- D06F39/02—Devices for adding soap or other washing agents
- D06F39/022—Devices for adding soap or other washing agents in a liquid state
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B43/00—Machines, pumps, or pumping installations having flexible working members
- F04B43/0009—Special features
- F04B43/0081—Special features systems, control, safety measures
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
- F04B49/06—Control using electricity
- F04B49/065—Control using electricity and making use of computers
-
- D—TEXTILES; PAPER
- D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
- D06F—LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
- D06F33/00—Control of operations performed in washing machines or washer-dryers
- D06F33/30—Control of washing machines characterised by the purpose or target of the control
- D06F33/32—Control of operational steps, e.g. optimisation or improvement of operational steps depending on the condition of the laundry
- D06F33/37—Control of operational steps, e.g. optimisation or improvement of operational steps depending on the condition of the laundry of metering of detergents or additives
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B2203/00—Motor parameters
- F04B2203/02—Motor parameters of rotating electric motors
- F04B2203/0201—Current
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B2203/00—Motor parameters
- F04B2203/02—Motor parameters of rotating electric motors
- F04B2203/0203—Magnetic flux
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B2203/00—Motor parameters
- F04B2203/02—Motor parameters of rotating electric motors
- F04B2203/0208—Power
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B2205/00—Fluid parameters
- F04B2205/05—Pressure after the pump outlet
Abstract
The present invention is an improved flow-metered pumping system using an air-backed diaphragm pump with load compensation.
A variable motor speed controller is used to compensate for flow rate reduction caused by pressure effects. When the output pressure on the pump increases to a point where the load on the pump motor exceeds a specified threshold, the motor speed controller increases the speed of the motor to compensate for pressure induced diaphragm distortion losses and to achieve a substantially constant flow rate across a range of pump output pressures.
A variable motor speed controller is used to compensate for flow rate reduction caused by pressure effects. When the output pressure on the pump increases to a point where the load on the pump motor exceeds a specified threshold, the motor speed controller increases the speed of the motor to compensate for pressure induced diaphragm distortion losses and to achieve a substantially constant flow rate across a range of pump output pressures.
Description
WO 95/093~5 , ~ ~ 1 7 1 7 1 6 PCT/CAg4/00517 FLOW I~ 5KED Plll~PING WITEI LOAD COM~ 'rION
SYSTE:~I AND ~nr~
FI~r~n OF T}~! T~v~!~TIoN
The present invention relate6 generally to metered pumping systems, and particularly to a constant flow pumping system using air-backed A 1 Aphragm pumps.
R~CKGROtJND OF T}~ I Nv~ oN
Air-backed diaphragm pumps provide an economical and reliable solution for many fluid handling applications.
However, they are not suitable for use in a sy~tem where a precise or highly stable flow rate is required. The flow rate of such pumps drops with increasing pressure on the pump outlet for several reasons. First, the increased load slows the motor down resulting in a re~ A flow rate.
Second, the unsupported regions of the pump A i Aph~agm balloon slightly in proportion to the prQ~sure on the outlet, reducing the effectiv~ displacemQnt ~nd flow rate of the pump. ThQse A ~ Aph~ agm distortion-based flow rate losses are i~A~ponA~nt of motor typo.
While load ~AllceA motor speed reductions can be comr~n~ted by using control tec~n~ques well known in the art, such ~o~L-~ion tech~ques only counter~ct ~bout 70~
of pressure induced flow rate los~es. These te~hniques do not compensate for diaphragm distortion-based flow rate losses which can account for up to 30% of the pressure induced flow reduction.
One method of eliminating the distortion based diaphragm flow rate loss is to support the diaphragm with some incompressible liquid in a sealed chamber h~h i n~ the diaphragm. However, such liquid-h~oke~ pumps are inefficient and relatively e~r~n~ive compared to air-backed pumps. Alternatively, a rotor vane pump can be used instead of a diaphragm pump. A rotor vane pump can accurately maintain a specified flow rate through varied outlet pressures. However, rotor vane pumps ~re very expensive. Moreover, rotor vane pumps cannot pump fluid3 cont~;n~ng large particulates (> 50 micron) and as a result reguire the use ofimicr~f~ilters to screen any fluid that .
is pumped. Air-backed diaphragm pumps, on the other hand, are inexpensive and can pump fluids with relatively large particulates without impairing the pump.
S Pumps which have a form of speed control are described in United States patents 4,384,825 and 5,163,818. The '825 patent is directed to a portable battery powered pump which provides constant mass flow of air sample through a particulate filter or vapor trap. The system is used for sampling ambient air where the speed of the motor is monitored by a photo-optical device. The speed of the motor is varied depending upon feedback received from the photo-optical speed measuring device. The motor current is also measured to provide a signal to indicate restricted flow.
The measured current may also be fed back which, in combination with the motor speed signal, causes an increased speed as air flow resistance increases. Similarly with the '818 patent, an automatic constant air flow rate pump unit is provided for sampling air. The instantaneous air flow is circulated and compared with the programmed desired air flow rate. The motor speed is modulated in response to the controlling computer comparing the instantaneous air flow rate with the programmed rate causing the pump to approach the desired air flow rate.
An object of the invention is to provide a low cost metered flow pumping system that provides substantially constant flow rate across a range of pump output pressures.
Another object of the present invention is to provide a metered flow pumping system that is not sensitive to the presence fluid particulates.
Another object of the invention is to provide a metered flow pumping system using an air-backed diaphragm pump.
SUMMARY OF THE INVENTION
In summary, the present invention is an improved flow-metered pumping system using an air-backed diaphragm pump with load compensation. A variable motor speed controller is used to compensate for flow rate reduction caused by pressure effects.
The load on the motor driving r ~ ~ Z 1 7 1 7i ~6 a diaphragm pump increases in proportion to the pressure on the output of the pump. This load is measured and used in a feedback loop to incr~ase the speed of the motor. ~he gain of this feedback loop is set at such a level as to compensate for pressure induced diaphragm distortion losses and to achieve substantially constant flow rate across a range of pump output pressures.
In accordance with an aspect o~ the invention, a flow-metered pumping system, comprises:
a pump for pumping a liquid;
a pump motor for driving the pump, the pump motor including a motor driver for supplying power to the pump motor;
a speed sensor, coupled to the pump motor, for generating a speed signal corresponding to the pump motor's speed;
a load sensor, coupled to the pump motor, for generating a load signal corresponding to the pump motor's load;
- 20 ' -- ' ~ ! ;
; ;' ~ i '-W095/09305 . ~ ~ i r ~ PCT/CA94/00517 2~ 7~ 7~6 speed control means, coupled to the motor driver and to the speed ~en~r, for maint~in;ng the speed of the pump motor at a specified speed; the sp~ed control means including a negative feedback means for modulating the amount of power supplied by the motor driver to the pump ~ motor according to the speed signal and the specified speed;
speed compensation means, coupled to the speed control mean and to the load sen~or, for maint~in;~g a substantially constant flow rate through the pump; the speed compensation means including a positive feedback means for adjusting the specified speed according to the load signal and a specified base speed.
According to a further aspect of the invention, a flow-metered pumping system comprises;
a motor driven pump for pumping a liquid;
a load r~n~or coupled to the pump for generating a load signal corresponA; ng to 10A~; ng on the pump;
a speed ~n~r coupled to the pump for generating a speed ~ignal corresp~ to the pump's speed;
speed control means, coupled to the pump, the load ~ or, and the speed ~eP-o~ for maintA j n; ~g a substantially constant flow of the liquid through the pump corresponding to a specified base pump speed; the speed control means including feedback means for modulating said pump's speed according to the load signal, the speed signal, and the specified base speed such that the pump's speed is increased by the speed control means as the load signal increases in value.
In accordance with a further aspect of the invention, a method of flow-metered pumping comprises:
providing a pump for pumping a liquid;
operating a pump motor for driving the pump; the pump - motor including a motor driver for supplying power to the pump motor;
measuring the pump motor's load;
measuring the pump motor's speed;
WO 95/0!~305 2 1 7 ~ 7 ~ 6 PCT/CA94/00517 ~. ~. r - - _ 4 --maint~ining ~ substantially constant flow rate through the pump, including modulating the pump motor's speed according to measured load, the measured speed and a specified base flow rate such that the pump motor' 8 speed is increased as the measured load increases.
RRIF~F Dli:8CRIPTION OF T~ DRAWINGS
Additional objects and features of the invention will be more readily apparent from the following detailed description and appended claims when taken in conjunction with the drawings, in which:
Figure 1 is a block diagram of a WA~h; ~ machine system that uses the flow-metered pumping system of the instant invention to provide a constant flow rate of chemical solution to the w~h~ng mach;n~-.
Figure 2 i~ a block diagram of thQ flow-metQrQd pumping sy~tem of the instant invQntion.
Figure 3 depict~ a pump motor drivs circuit and tha drive and measurement 8i ~nA 1 ~ a~sociated therewith.
Figure 4 depict~ a graph showing the motor speed for an air-backed diaphragm pump n~eA~ to maintain a constant flow rate for a range of motor loads.
Figure 5 is a flow chart for a dual control loop to maintain a constant flow through an air-backed diaphragm pump.
Figure 6 is a timing diagram showing the sequence of flow control steps used in the dual control loop emho~;ment of the present invention.
Figure 7 is a flow chart for an alternate control method to maintain a constant flow through a pump.
D~CRIPTTON OF T~ p~ n ~BODI~TS
Figure 1 shows a w~-h;ng mach;~ system 100 utilizing meterQd flow pump controller~ 102-1, 102-2, 102-3 of the present invention. Tha w~h; nq machine sy~tQm includes w~hin~ ma~hine~ 104-1 to 104-6 which receive chemical solution pumped at a measured flow rate by pumps 111-116.
These metered-flow pumps are controlled by metered flow pump controllers 102-1 to 102-3. Each pump controller 102 .
can control up to two pumps. Each of the two pumps attached to one controller can feed a separate washer or they both can be attached to a single washer to provide double the maximum flow of solution to that washer. Washer 104-1 is shown connected to a single pump 111, which is one of two pumps controlled by metered flow controller 102-1. Pump 111 draws chemical solution from main conduit 30 and delivers the solution to washer 104-1 via feed conduit 31. Other washers in the system are connected to the pumps and main conduit in a similar manner.
Master controller 120 coordinates the various subsystems of the washing machine system. It communicates to the pump controllers and washing machines over serial connection line 121. In the instant embodiment, this serial connection is implemented using a RS 485 communication protocol. The master controller 120 specifies desired flow rates to the metered-flow pump controllers 102 over serial connection line 121.
Figure 2 shows the metered flow pumping system of the instant invention including the controller 102, and two pumps 111, and 112. The instant invention has the capability to independently regulate two pumps but can be operated to control a single pump or multiple pumps without departing from the scope of the invention. Each pump 111, 112 consists of a pulse controlled permanent magnet DC motor 130, motor driver 132, and an air-backed diaphragm pump 134. The motor drivers 132 deliver power to motors 130 according to the signals on pulse length modulation (PLM) signal lines 234, 235 which are output from the controller 120.
The controller 102 consists of a CPU 210 which executes software stored in a ROM 211 in conjunction with a RAM 212 for manipulating controller hardware to perform control functions.
The ROM 211 stores control programs 214-216 and data tables 218-221. The data tables hold parameters used by the controller software in controlling the pump motors. The controller also has a timer 213 for scheduling the execution of control WO 95/09305 ~ ~ ~ t r 1 ~2 2 1 7 1 7 ~ 6 PCT/CA94/OOS17 functions. A-D converters 230, 231 translate analog signals from the pump motors into digital values that are used by the CPU 210. The controller has output port registers 232 and 233 connected to PLM signal lines 234, 235. The CPU 210 writes to these registers to control the PLM signal lines 234, 235. Finally, the controller has I/O
interface 240 sending and receiving messages to and from an outside source using the RS 485 communication protocol. In the preferred embodiment, all Of the ~,.LLoller elements are cont~ n~~ within a 68HC705B5 single chip micro-controller, but they can be built using discreet components without departing from the scope of the invention. Other micro-controllers, preferably with built-in analog to digital converters, could be used in alternate embodiments.
The controller software 214-216 instructs the CPU 210 to calculate the amount of time that the PLM signals output on lines 234, 235 should be ON in a given cycle according to the control algorithms ~i~cllcced below. The CPU 210 programs the timer 213 to generate a signal at the specified time interval. The CPU 210 writes a high value to the output port correspon~in~ to a PLM signal to turn on that PLM signal and writes a low value to the same o~uL
port to turn off the PLM signal when the timer 213 indicates that the ~pecified time ha~ 61 ap~
ThQ PLN signals are pQriodic (8.192 ms cycle tim~ in th~ instant embodim~nt) and control power to the pump motor. When a PLM signal i~ high the motor i8 supplied with power that causes acceleration. When th~ PLM signal is low the powQr is cut off and the motor coasts. The speed of a motor can be controlled by adjusting the duty cycle of the PLM signal. The more that the signal i5 ~on~
duxing a cycle, the faster the motor will rotate.
Referring to Figures 2 and 3, each motor provides the controller with two sense signals. The motor back-emf signals received on lines 241, 242 are used by the controller as a measure of motor speed. Motor speed can be measured by other means such as an encoder or tachometer WO 95/093~5 ~ 2 PCT/CA94/00517 without departing from the scope of thQ invention. The motor current signals received on lines 243 and 244 are used by the controller as an indication of the load on each motor. Motor lo~i ng can also be measured by other means such as a torque or pressure sensor without departing from the scope of the invention.
The measurement of the back-emf signal is synchronized with the PLM drive signal. The controller software reads the back-emf signal at the end of the PLM drive cycle just before the PLM signal i8 turned on for the next drive cycle. This timing allows the measurement of a motor's back-emf without interference from the PLM drive signal.
The timing of the motor current signal i8 not critical. In the instant emho~ ~ ment, the motor current i8 re~d in the middle of the PLM cycle but can be read ~t other points in the PLM drive cycla without effecting the operation of the invention.
Figure 4 depicts a motor speed ~nd motor load graph that shows relAtionship b~tween motor speed and motor load for an air-backed ~Aphragm pump for two different flow rates. As shown, in order to maintain a constant flow rate through the pump, as the load (i.e., ohL~uL pressure) on the pump increases past a threshold load, the motor speed must be increased in order to maintain a constant flow rate. Also shown in Figure 4 is that the threshold load is different for different flow rates and that different positive feedback gains are needed to maintain different flow rates.
Figure 5 shows the feedback ~o-.Lrol system implemented by the controller 210. The controller uses a dual feedback loop system to control the flow rate through the motor.
The controller 210 executes a first motor speed feedback routine 215 to control motor speed. The controller uses a specified Speed Command value as the target motor speed.
It gets a back-EMF signal from the motor that is proportional to motor speed. The timer is used to signal the controller when to read the back-EMF signal. The A-D
converters are used to convert the analog back-emf signal W0 95109305 ~ ~ r~ ~ 2 1 7 1 7 1 6 PCT/CA94/005l7 ~ 8 ~
into a digital ~ignal for manipulation by the CPU. The controller uses the digital ~o,.ve ~ion of the back-EMF
signal and speed command value to select the duty cycle for the PLM signal. An error value ~Lv~GLLional to the difference between the actual speed (a~ reflected by the digitized back-EMF sign~l) and ths speed command value ic generated by the controller. The change in the PLM signal duty cycle i5 determined by multiplying the error by a proportional gain signal and A~ 1 n~ the integral of the error with respect to time multiplied by an integral gain value. This change value is added to a n steady state" PLM
duty cycle value that is determined by multiplying the speed command value by an initial gain. The following p~ ocode shows the operation of the controller software implementing the first fee~hA~k loop:
Speed Control Receive Back emf error ~ Spes~ommand - Back Qmf accum ~ accum + (~rror * Int~gralGain) clip accum to predefined range temp ~ (Sp~eA~ommand * InitialGain) +
(QrrOr * ~ ~pG~ ~ionalGain) + accum clip temp to predefined range PLM duty cycl~ ~ temp -- c~l,L~ller will continue to drive motor with this computed -- PLM duty cycle until this value i~ updated This routine is executed once during each PLM drive cycle after the back-emf has been read.
The control software includes a second feedback loop routine 216 to adjust the speed command value used by the first f~e~h~k loop to compensate for ~iAphragm distortion-~nAI~c~ flow ratQ 1088e8 at high output pressure~. ThQ ~o..LLollQr r~c~ive~ an externally ~ourced flow command valuQ ovQr th~ RS 485 link that ~pecifie~ the target flow ratQ through the pump. The flow command value in thQ prefQrrQd QmbodimQnt i8 actually a ba8e pump speed value which will achievQ a de~ired flow rate if the load on the pump motor is very low.
WO 95/09305 '.. '' ' ~ ~ C 2 1 7 ~ 7 1 6 PCT/CAg4/00517 g The controller gets a motor current signal from the motor that is proportional to the load on the motor. The controller uses the motor current and flow command value to ~ select an appropriate speed command value. The motor current i8 compared to a threshold value. If the motor current i8 greater than the thrQshold, the difference between the motor current and the threshold i8 multiplied by a flow gain and addQd to the flow command value to generate a new speed command value for the motor speed feedback routine 215. A~ the load incrQasQs, the speed command value i8 increa~ad to compQ~-te for throughput 1058Q8 caused by pressure Qffects. The following r~r~9co~ shows the operation of the controller software implementing the second control loop:
Load Compensation Receive MotorCurrent if MotorCurrent ~ Threshold then {
SpeedCommand ~ FlowCommand +
( (MotorCurrent - Threshold) * FlowGain ) e1Be Cp~ ommand ~ FlowCommand Return }
The positivQ fe~h-~k gain coefficient, FlowGain, in thi~ routin~ i- computed from flow and speed mea~urQments of actual air-backQd A; ~phragm pump~ 80 that th~ flow rate of fluid through the pump remain~ substanti~lly constant for a ~p~c~fied range of o~yu~ pressure~ or motor loads.
This routine i8 executed once during each PLM cycle just after the motor current signal has been read.
Each time a new flow command value i~ received over the RS 485 port the CPU 210 executes an init;Al;~ation routine 213. The initialization routine select~ values for the flow gain, proportional gain and integral gain, ~nd motor current threshold using the data tables 218-221.
There i~ a ~eparate table for each of these par~meters.
Each table consists of a sequence of flow rate / value W095/09305 ~ ' 2 1 7 1 7 1 6 PCTICA94/00517 pairs. The value paired with A ~low rate i~ the optimized parameter value correspo~; ng to that flow rate. These pairs are stored in the table in sequence of increasing flow rates. The initialization routine scans the table starting at the highest flow rate and locates the largest flow rate that is less than or equal to the new flow command. The parameter is initialized to the value correspo~ g this located flow rate. Using a parameter lookup table indexed according to flow rate allows the controller software to be optimized for broad range of flow rates. In th~ preferred embodiment, the parameters can also be down-loaded over the serial link, allowing the master ~on~Loller to optimize the control software for certain ~ituations.
ThQ initialization routin~ then ramps the motor ~peed up or down to th~ desired flow rate by increa~ing or decreasing ~peed command valu~ by a constant amount each cycle until the target motor speed is r~A~h~A. Once up to speed, the init~ A 1i7ation routine then enable~ the dual loop control algorithm to control speed and compensate for load. The following p~ Ao~oA~ shows the flow of the init;A1i7Ation routine:
Tnit;A1i 7 {
Receive FlowCommmand if FlowCommand is NQW
ThrQshold - ThresholdTabl~(FlowCommand) FlowGain ~ GainTablQ(FlowCommand) Initi_lGain ~ InitGA~nTable(FlowCommand) ProportionalGain - Prop~A~Table(FlowCommand) Ramp Sp~Command up or down until SpeedCommand - FlowCommand }
Return }
ThresholdTabl2(FlowCommand) -- Note structure of Threshold table is -- Table(Flow(l:N),Threshold(l:N)) Index ~ l Do For Index = l to N
If Flow(Index) ~ FlowCo~mand {
WO 95/09305 , t ~ 2 1 7 1 7 1 6 PCT/CAg4/00517 1 ~ -R~turn (Threshold(Index)) }
Return (Threshold(N)) -- The FlowG~in, InitialGain ~nd ProportionalGain function3 all -- work in the same way as the ThresholdTable function, except -- that the flow value brQakpoints may be different in each table.
Figure 6 i5 a timing diagram showing the timing relationship between the measurement of motor signals, the motor drive signals, and the software implementing the dual loop control algorithm. When the PLM motor drive signal is high in Figure 6, the motor is receiving power that causes acceleration. When the motor drive signal is low the motor receives no power and coasts. The back-EMF waveform represents thQ back-emf of the motor driven by the PLM
motor driv~ ~ign~l. Th~ currant ~ens~ wav~form ~how~ the current through th~ motor driv~n by the PLM motor drive signal.
Motor current and back-emf measurement timing i~
~ eA to the motor drive timing because the back-emf must be s~n~ at the end of the drive interval ~ust before the "on" portion of the drive waveform begins. The current measurements are made near the middle of the PLN drive cycle. The PLM motor drive signal is turned on and off according to the output of the controller timer. That ~ame timer is used to signal the controller software to measure current and back-emf, thereby insuring that there is a prQciee rQlationship between thQ PLM drive signal and the motor signal measuremQnt points.
The motor current is read shortly after the motor driv~ ~ignal i~ turnQd of f. The load compen~ation routine 216 thQn ~x~cutes and calc~ t~ a spQed command value for U8- by the fir~t cG,.L~ol loop routine. The ti~er i~
ammed to cau3e a back-emf read a Qpec;fiQd time before the start of th~ next PLM driv~ cycl~. The sp~d control routinQ 215 is executed after the back-~mf has bQen measured to calculate a new duty cycle value for the PLM
W095/09305 2 1 7 1 7 1 6 PCT/CAg4/00~l7 drive signal that will be used by a counter to control the n on" portion of the subsequent PLM duty cycle.
Figure 7 shows the flow of an alternative method of controlling the motor using only a single control loop.
The controller implements a signal feed back loop to control motor speed. The controller uses a specified speed command value that i~ the target motor speed. It get~ a signal from the ~otor, motor current that i~ ~o~Lional to the load on the motor. The c~,-LLoller u~es the motor current and speed command value to select the duty cycle for the PLM motor drive ~ignal, increasing the duty cycle of the PLM motor drive signal as the load increasQ~.
Controller software implementing a single control loop method has only a single feedback loop that performs both the speed control and load compensation function~. The sequence of instructions in the software routine is similar to the first fe~h~rk loop control routine Ai~r~l~r~~ above.
In this embodiment, however, the specified flow command value i~ used in~tead of a cpeed command value as the target motor speed. In addition load compQnsation i5 implementQd by directly adjusting the PL~ duty cycle rather than adjusting the target motor spQQd. The following r~ AocoA~ show~ the operation of the cG..L~oller software implementing this fseAh~k loop:
Speed C~ ol with Load Compensation Receive MotorCurrent Receive Back_emf error ~ FlowCommand - Back_emf accum ~ accum + (error * IntegralGain) clip accum to predefined range temp - (FlowCommand * InitialGain) +
(error * ProportionalGain) + accum if MotorCurrent ~ Threshold then temp = temp + ((MotorCurrent - Threshold) *
FlowGain) clip temp to predefined range P~M duty cycle - temp }
Thi~ routine is executed once during each PLM cycle after motor current and back-emf have been measured.
W095/09305 , ' . ~ S 2 1 7 1 7 1 6 PCT/CA94/OOS17 .
Although preferred embodiments of the invention are described herein in detail, it will be understood by those skilled in the art that variations may be made thereto without departing from the spirit of the invention or the ~cope of the appended claims.
SYSTE:~I AND ~nr~
FI~r~n OF T}~! T~v~!~TIoN
The present invention relate6 generally to metered pumping systems, and particularly to a constant flow pumping system using air-backed A 1 Aphragm pumps.
R~CKGROtJND OF T}~ I Nv~ oN
Air-backed diaphragm pumps provide an economical and reliable solution for many fluid handling applications.
However, they are not suitable for use in a sy~tem where a precise or highly stable flow rate is required. The flow rate of such pumps drops with increasing pressure on the pump outlet for several reasons. First, the increased load slows the motor down resulting in a re~ A flow rate.
Second, the unsupported regions of the pump A i Aph~agm balloon slightly in proportion to the prQ~sure on the outlet, reducing the effectiv~ displacemQnt ~nd flow rate of the pump. ThQse A ~ Aph~ agm distortion-based flow rate losses are i~A~ponA~nt of motor typo.
While load ~AllceA motor speed reductions can be comr~n~ted by using control tec~n~ques well known in the art, such ~o~L-~ion tech~ques only counter~ct ~bout 70~
of pressure induced flow rate los~es. These te~hniques do not compensate for diaphragm distortion-based flow rate losses which can account for up to 30% of the pressure induced flow reduction.
One method of eliminating the distortion based diaphragm flow rate loss is to support the diaphragm with some incompressible liquid in a sealed chamber h~h i n~ the diaphragm. However, such liquid-h~oke~ pumps are inefficient and relatively e~r~n~ive compared to air-backed pumps. Alternatively, a rotor vane pump can be used instead of a diaphragm pump. A rotor vane pump can accurately maintain a specified flow rate through varied outlet pressures. However, rotor vane pumps ~re very expensive. Moreover, rotor vane pumps cannot pump fluid3 cont~;n~ng large particulates (> 50 micron) and as a result reguire the use ofimicr~f~ilters to screen any fluid that .
is pumped. Air-backed diaphragm pumps, on the other hand, are inexpensive and can pump fluids with relatively large particulates without impairing the pump.
S Pumps which have a form of speed control are described in United States patents 4,384,825 and 5,163,818. The '825 patent is directed to a portable battery powered pump which provides constant mass flow of air sample through a particulate filter or vapor trap. The system is used for sampling ambient air where the speed of the motor is monitored by a photo-optical device. The speed of the motor is varied depending upon feedback received from the photo-optical speed measuring device. The motor current is also measured to provide a signal to indicate restricted flow.
The measured current may also be fed back which, in combination with the motor speed signal, causes an increased speed as air flow resistance increases. Similarly with the '818 patent, an automatic constant air flow rate pump unit is provided for sampling air. The instantaneous air flow is circulated and compared with the programmed desired air flow rate. The motor speed is modulated in response to the controlling computer comparing the instantaneous air flow rate with the programmed rate causing the pump to approach the desired air flow rate.
An object of the invention is to provide a low cost metered flow pumping system that provides substantially constant flow rate across a range of pump output pressures.
Another object of the present invention is to provide a metered flow pumping system that is not sensitive to the presence fluid particulates.
Another object of the invention is to provide a metered flow pumping system using an air-backed diaphragm pump.
SUMMARY OF THE INVENTION
In summary, the present invention is an improved flow-metered pumping system using an air-backed diaphragm pump with load compensation. A variable motor speed controller is used to compensate for flow rate reduction caused by pressure effects.
The load on the motor driving r ~ ~ Z 1 7 1 7i ~6 a diaphragm pump increases in proportion to the pressure on the output of the pump. This load is measured and used in a feedback loop to incr~ase the speed of the motor. ~he gain of this feedback loop is set at such a level as to compensate for pressure induced diaphragm distortion losses and to achieve substantially constant flow rate across a range of pump output pressures.
In accordance with an aspect o~ the invention, a flow-metered pumping system, comprises:
a pump for pumping a liquid;
a pump motor for driving the pump, the pump motor including a motor driver for supplying power to the pump motor;
a speed sensor, coupled to the pump motor, for generating a speed signal corresponding to the pump motor's speed;
a load sensor, coupled to the pump motor, for generating a load signal corresponding to the pump motor's load;
- 20 ' -- ' ~ ! ;
; ;' ~ i '-W095/09305 . ~ ~ i r ~ PCT/CA94/00517 2~ 7~ 7~6 speed control means, coupled to the motor driver and to the speed ~en~r, for maint~in;ng the speed of the pump motor at a specified speed; the sp~ed control means including a negative feedback means for modulating the amount of power supplied by the motor driver to the pump ~ motor according to the speed signal and the specified speed;
speed compensation means, coupled to the speed control mean and to the load sen~or, for maint~in;~g a substantially constant flow rate through the pump; the speed compensation means including a positive feedback means for adjusting the specified speed according to the load signal and a specified base speed.
According to a further aspect of the invention, a flow-metered pumping system comprises;
a motor driven pump for pumping a liquid;
a load r~n~or coupled to the pump for generating a load signal corresponA; ng to 10A~; ng on the pump;
a speed ~n~r coupled to the pump for generating a speed ~ignal corresp~ to the pump's speed;
speed control means, coupled to the pump, the load ~ or, and the speed ~eP-o~ for maintA j n; ~g a substantially constant flow of the liquid through the pump corresponding to a specified base pump speed; the speed control means including feedback means for modulating said pump's speed according to the load signal, the speed signal, and the specified base speed such that the pump's speed is increased by the speed control means as the load signal increases in value.
In accordance with a further aspect of the invention, a method of flow-metered pumping comprises:
providing a pump for pumping a liquid;
operating a pump motor for driving the pump; the pump - motor including a motor driver for supplying power to the pump motor;
measuring the pump motor's load;
measuring the pump motor's speed;
WO 95/0!~305 2 1 7 ~ 7 ~ 6 PCT/CA94/00517 ~. ~. r - - _ 4 --maint~ining ~ substantially constant flow rate through the pump, including modulating the pump motor's speed according to measured load, the measured speed and a specified base flow rate such that the pump motor' 8 speed is increased as the measured load increases.
RRIF~F Dli:8CRIPTION OF T~ DRAWINGS
Additional objects and features of the invention will be more readily apparent from the following detailed description and appended claims when taken in conjunction with the drawings, in which:
Figure 1 is a block diagram of a WA~h; ~ machine system that uses the flow-metered pumping system of the instant invention to provide a constant flow rate of chemical solution to the w~h~ng mach;n~-.
Figure 2 i~ a block diagram of thQ flow-metQrQd pumping sy~tem of the instant invQntion.
Figure 3 depict~ a pump motor drivs circuit and tha drive and measurement 8i ~nA 1 ~ a~sociated therewith.
Figure 4 depict~ a graph showing the motor speed for an air-backed diaphragm pump n~eA~ to maintain a constant flow rate for a range of motor loads.
Figure 5 is a flow chart for a dual control loop to maintain a constant flow through an air-backed diaphragm pump.
Figure 6 is a timing diagram showing the sequence of flow control steps used in the dual control loop emho~;ment of the present invention.
Figure 7 is a flow chart for an alternate control method to maintain a constant flow through a pump.
D~CRIPTTON OF T~ p~ n ~BODI~TS
Figure 1 shows a w~-h;ng mach;~ system 100 utilizing meterQd flow pump controller~ 102-1, 102-2, 102-3 of the present invention. Tha w~h; nq machine sy~tQm includes w~hin~ ma~hine~ 104-1 to 104-6 which receive chemical solution pumped at a measured flow rate by pumps 111-116.
These metered-flow pumps are controlled by metered flow pump controllers 102-1 to 102-3. Each pump controller 102 .
can control up to two pumps. Each of the two pumps attached to one controller can feed a separate washer or they both can be attached to a single washer to provide double the maximum flow of solution to that washer. Washer 104-1 is shown connected to a single pump 111, which is one of two pumps controlled by metered flow controller 102-1. Pump 111 draws chemical solution from main conduit 30 and delivers the solution to washer 104-1 via feed conduit 31. Other washers in the system are connected to the pumps and main conduit in a similar manner.
Master controller 120 coordinates the various subsystems of the washing machine system. It communicates to the pump controllers and washing machines over serial connection line 121. In the instant embodiment, this serial connection is implemented using a RS 485 communication protocol. The master controller 120 specifies desired flow rates to the metered-flow pump controllers 102 over serial connection line 121.
Figure 2 shows the metered flow pumping system of the instant invention including the controller 102, and two pumps 111, and 112. The instant invention has the capability to independently regulate two pumps but can be operated to control a single pump or multiple pumps without departing from the scope of the invention. Each pump 111, 112 consists of a pulse controlled permanent magnet DC motor 130, motor driver 132, and an air-backed diaphragm pump 134. The motor drivers 132 deliver power to motors 130 according to the signals on pulse length modulation (PLM) signal lines 234, 235 which are output from the controller 120.
The controller 102 consists of a CPU 210 which executes software stored in a ROM 211 in conjunction with a RAM 212 for manipulating controller hardware to perform control functions.
The ROM 211 stores control programs 214-216 and data tables 218-221. The data tables hold parameters used by the controller software in controlling the pump motors. The controller also has a timer 213 for scheduling the execution of control WO 95/09305 ~ ~ ~ t r 1 ~2 2 1 7 1 7 ~ 6 PCT/CA94/OOS17 functions. A-D converters 230, 231 translate analog signals from the pump motors into digital values that are used by the CPU 210. The controller has output port registers 232 and 233 connected to PLM signal lines 234, 235. The CPU 210 writes to these registers to control the PLM signal lines 234, 235. Finally, the controller has I/O
interface 240 sending and receiving messages to and from an outside source using the RS 485 communication protocol. In the preferred embodiment, all Of the ~,.LLoller elements are cont~ n~~ within a 68HC705B5 single chip micro-controller, but they can be built using discreet components without departing from the scope of the invention. Other micro-controllers, preferably with built-in analog to digital converters, could be used in alternate embodiments.
The controller software 214-216 instructs the CPU 210 to calculate the amount of time that the PLM signals output on lines 234, 235 should be ON in a given cycle according to the control algorithms ~i~cllcced below. The CPU 210 programs the timer 213 to generate a signal at the specified time interval. The CPU 210 writes a high value to the output port correspon~in~ to a PLM signal to turn on that PLM signal and writes a low value to the same o~uL
port to turn off the PLM signal when the timer 213 indicates that the ~pecified time ha~ 61 ap~
ThQ PLN signals are pQriodic (8.192 ms cycle tim~ in th~ instant embodim~nt) and control power to the pump motor. When a PLM signal i~ high the motor i8 supplied with power that causes acceleration. When th~ PLM signal is low the powQr is cut off and the motor coasts. The speed of a motor can be controlled by adjusting the duty cycle of the PLM signal. The more that the signal i5 ~on~
duxing a cycle, the faster the motor will rotate.
Referring to Figures 2 and 3, each motor provides the controller with two sense signals. The motor back-emf signals received on lines 241, 242 are used by the controller as a measure of motor speed. Motor speed can be measured by other means such as an encoder or tachometer WO 95/093~5 ~ 2 PCT/CA94/00517 without departing from the scope of thQ invention. The motor current signals received on lines 243 and 244 are used by the controller as an indication of the load on each motor. Motor lo~i ng can also be measured by other means such as a torque or pressure sensor without departing from the scope of the invention.
The measurement of the back-emf signal is synchronized with the PLM drive signal. The controller software reads the back-emf signal at the end of the PLM drive cycle just before the PLM signal i8 turned on for the next drive cycle. This timing allows the measurement of a motor's back-emf without interference from the PLM drive signal.
The timing of the motor current signal i8 not critical. In the instant emho~ ~ ment, the motor current i8 re~d in the middle of the PLM cycle but can be read ~t other points in the PLM drive cycla without effecting the operation of the invention.
Figure 4 depicts a motor speed ~nd motor load graph that shows relAtionship b~tween motor speed and motor load for an air-backed ~Aphragm pump for two different flow rates. As shown, in order to maintain a constant flow rate through the pump, as the load (i.e., ohL~uL pressure) on the pump increases past a threshold load, the motor speed must be increased in order to maintain a constant flow rate. Also shown in Figure 4 is that the threshold load is different for different flow rates and that different positive feedback gains are needed to maintain different flow rates.
Figure 5 shows the feedback ~o-.Lrol system implemented by the controller 210. The controller uses a dual feedback loop system to control the flow rate through the motor.
The controller 210 executes a first motor speed feedback routine 215 to control motor speed. The controller uses a specified Speed Command value as the target motor speed.
It gets a back-EMF signal from the motor that is proportional to motor speed. The timer is used to signal the controller when to read the back-EMF signal. The A-D
converters are used to convert the analog back-emf signal W0 95109305 ~ ~ r~ ~ 2 1 7 1 7 1 6 PCT/CA94/005l7 ~ 8 ~
into a digital ~ignal for manipulation by the CPU. The controller uses the digital ~o,.ve ~ion of the back-EMF
signal and speed command value to select the duty cycle for the PLM signal. An error value ~Lv~GLLional to the difference between the actual speed (a~ reflected by the digitized back-EMF sign~l) and ths speed command value ic generated by the controller. The change in the PLM signal duty cycle i5 determined by multiplying the error by a proportional gain signal and A~ 1 n~ the integral of the error with respect to time multiplied by an integral gain value. This change value is added to a n steady state" PLM
duty cycle value that is determined by multiplying the speed command value by an initial gain. The following p~ ocode shows the operation of the controller software implementing the first fee~hA~k loop:
Speed Control Receive Back emf error ~ Spes~ommand - Back Qmf accum ~ accum + (~rror * Int~gralGain) clip accum to predefined range temp ~ (Sp~eA~ommand * InitialGain) +
(QrrOr * ~ ~pG~ ~ionalGain) + accum clip temp to predefined range PLM duty cycl~ ~ temp -- c~l,L~ller will continue to drive motor with this computed -- PLM duty cycle until this value i~ updated This routine is executed once during each PLM drive cycle after the back-emf has been read.
The control software includes a second feedback loop routine 216 to adjust the speed command value used by the first f~e~h~k loop to compensate for ~iAphragm distortion-~nAI~c~ flow ratQ 1088e8 at high output pressure~. ThQ ~o..LLollQr r~c~ive~ an externally ~ourced flow command valuQ ovQr th~ RS 485 link that ~pecifie~ the target flow ratQ through the pump. The flow command value in thQ prefQrrQd QmbodimQnt i8 actually a ba8e pump speed value which will achievQ a de~ired flow rate if the load on the pump motor is very low.
WO 95/09305 '.. '' ' ~ ~ C 2 1 7 ~ 7 1 6 PCT/CAg4/00517 g The controller gets a motor current signal from the motor that is proportional to the load on the motor. The controller uses the motor current and flow command value to ~ select an appropriate speed command value. The motor current i8 compared to a threshold value. If the motor current i8 greater than the thrQshold, the difference between the motor current and the threshold i8 multiplied by a flow gain and addQd to the flow command value to generate a new speed command value for the motor speed feedback routine 215. A~ the load incrQasQs, the speed command value i8 increa~ad to compQ~-te for throughput 1058Q8 caused by pressure Qffects. The following r~r~9co~ shows the operation of the controller software implementing the second control loop:
Load Compensation Receive MotorCurrent if MotorCurrent ~ Threshold then {
SpeedCommand ~ FlowCommand +
( (MotorCurrent - Threshold) * FlowGain ) e1Be Cp~ ommand ~ FlowCommand Return }
The positivQ fe~h-~k gain coefficient, FlowGain, in thi~ routin~ i- computed from flow and speed mea~urQments of actual air-backQd A; ~phragm pump~ 80 that th~ flow rate of fluid through the pump remain~ substanti~lly constant for a ~p~c~fied range of o~yu~ pressure~ or motor loads.
This routine i8 executed once during each PLM cycle just after the motor current signal has been read.
Each time a new flow command value i~ received over the RS 485 port the CPU 210 executes an init;Al;~ation routine 213. The initialization routine select~ values for the flow gain, proportional gain and integral gain, ~nd motor current threshold using the data tables 218-221.
There i~ a ~eparate table for each of these par~meters.
Each table consists of a sequence of flow rate / value W095/09305 ~ ' 2 1 7 1 7 1 6 PCTICA94/00517 pairs. The value paired with A ~low rate i~ the optimized parameter value correspo~; ng to that flow rate. These pairs are stored in the table in sequence of increasing flow rates. The initialization routine scans the table starting at the highest flow rate and locates the largest flow rate that is less than or equal to the new flow command. The parameter is initialized to the value correspo~ g this located flow rate. Using a parameter lookup table indexed according to flow rate allows the controller software to be optimized for broad range of flow rates. In th~ preferred embodiment, the parameters can also be down-loaded over the serial link, allowing the master ~on~Loller to optimize the control software for certain ~ituations.
ThQ initialization routin~ then ramps the motor ~peed up or down to th~ desired flow rate by increa~ing or decreasing ~peed command valu~ by a constant amount each cycle until the target motor speed is r~A~h~A. Once up to speed, the init~ A 1i7ation routine then enable~ the dual loop control algorithm to control speed and compensate for load. The following p~ Ao~oA~ shows the flow of the init;A1i7Ation routine:
Tnit;A1i 7 {
Receive FlowCommmand if FlowCommand is NQW
ThrQshold - ThresholdTabl~(FlowCommand) FlowGain ~ GainTablQ(FlowCommand) Initi_lGain ~ InitGA~nTable(FlowCommand) ProportionalGain - Prop~A~Table(FlowCommand) Ramp Sp~Command up or down until SpeedCommand - FlowCommand }
Return }
ThresholdTabl2(FlowCommand) -- Note structure of Threshold table is -- Table(Flow(l:N),Threshold(l:N)) Index ~ l Do For Index = l to N
If Flow(Index) ~ FlowCo~mand {
WO 95/09305 , t ~ 2 1 7 1 7 1 6 PCT/CAg4/00517 1 ~ -R~turn (Threshold(Index)) }
Return (Threshold(N)) -- The FlowG~in, InitialGain ~nd ProportionalGain function3 all -- work in the same way as the ThresholdTable function, except -- that the flow value brQakpoints may be different in each table.
Figure 6 i5 a timing diagram showing the timing relationship between the measurement of motor signals, the motor drive signals, and the software implementing the dual loop control algorithm. When the PLM motor drive signal is high in Figure 6, the motor is receiving power that causes acceleration. When the motor drive signal is low the motor receives no power and coasts. The back-EMF waveform represents thQ back-emf of the motor driven by the PLM
motor driv~ ~ign~l. Th~ currant ~ens~ wav~form ~how~ the current through th~ motor driv~n by the PLM motor drive signal.
Motor current and back-emf measurement timing i~
~ eA to the motor drive timing because the back-emf must be s~n~ at the end of the drive interval ~ust before the "on" portion of the drive waveform begins. The current measurements are made near the middle of the PLN drive cycle. The PLM motor drive signal is turned on and off according to the output of the controller timer. That ~ame timer is used to signal the controller software to measure current and back-emf, thereby insuring that there is a prQciee rQlationship between thQ PLM drive signal and the motor signal measuremQnt points.
The motor current is read shortly after the motor driv~ ~ignal i~ turnQd of f. The load compen~ation routine 216 thQn ~x~cutes and calc~ t~ a spQed command value for U8- by the fir~t cG,.L~ol loop routine. The ti~er i~
ammed to cau3e a back-emf read a Qpec;fiQd time before the start of th~ next PLM driv~ cycl~. The sp~d control routinQ 215 is executed after the back-~mf has bQen measured to calculate a new duty cycle value for the PLM
W095/09305 2 1 7 1 7 1 6 PCT/CAg4/00~l7 drive signal that will be used by a counter to control the n on" portion of the subsequent PLM duty cycle.
Figure 7 shows the flow of an alternative method of controlling the motor using only a single control loop.
The controller implements a signal feed back loop to control motor speed. The controller uses a specified speed command value that i~ the target motor speed. It get~ a signal from the ~otor, motor current that i~ ~o~Lional to the load on the motor. The c~,-LLoller u~es the motor current and speed command value to select the duty cycle for the PLM motor drive ~ignal, increasing the duty cycle of the PLM motor drive signal as the load increasQ~.
Controller software implementing a single control loop method has only a single feedback loop that performs both the speed control and load compensation function~. The sequence of instructions in the software routine is similar to the first fe~h~rk loop control routine Ai~r~l~r~~ above.
In this embodiment, however, the specified flow command value i~ used in~tead of a cpeed command value as the target motor speed. In addition load compQnsation i5 implementQd by directly adjusting the PL~ duty cycle rather than adjusting the target motor spQQd. The following r~ AocoA~ show~ the operation of the cG..L~oller software implementing this fseAh~k loop:
Speed C~ ol with Load Compensation Receive MotorCurrent Receive Back_emf error ~ FlowCommand - Back_emf accum ~ accum + (error * IntegralGain) clip accum to predefined range temp - (FlowCommand * InitialGain) +
(error * ProportionalGain) + accum if MotorCurrent ~ Threshold then temp = temp + ((MotorCurrent - Threshold) *
FlowGain) clip temp to predefined range P~M duty cycle - temp }
Thi~ routine is executed once during each PLM cycle after motor current and back-emf have been measured.
W095/09305 , ' . ~ S 2 1 7 1 7 1 6 PCT/CA94/OOS17 .
Although preferred embodiments of the invention are described herein in detail, it will be understood by those skilled in the art that variations may be made thereto without departing from the spirit of the invention or the ~cope of the appended claims.
Claims (22)
1. A flow-metered pumping system, comprising:
an air-backed diaphragm pump for pumping a liquid;
a pump motor for driving said pump, said pump motor including a motor driver for supplying power to said pump motor;
a speed sensor, coupled to said pump motor, for generating a speed signal corresponding to pump motor speed;
a load sensor, coupled to said pump motor, for generating a load signal corresponding to pump motor load;
speed control means, coupled to said motor driver and to said speed sensor, for maintaining said pump motor speed at a specified speed command value; said speed control means including a negative feedback means for modulating the amount of power supplied by said motor driver to said pump motor according to said speed signal and said specified speed command value;
speed compensation means, coupled to said speed control means and to said load sensor, for maintaining a substantially constant flow rate through said pump; said speed compensation means including a positive feedback means for adjusting said specified speed command value according to said load signal and a specified base speed.
an air-backed diaphragm pump for pumping a liquid;
a pump motor for driving said pump, said pump motor including a motor driver for supplying power to said pump motor;
a speed sensor, coupled to said pump motor, for generating a speed signal corresponding to pump motor speed;
a load sensor, coupled to said pump motor, for generating a load signal corresponding to pump motor load;
speed control means, coupled to said motor driver and to said speed sensor, for maintaining said pump motor speed at a specified speed command value; said speed control means including a negative feedback means for modulating the amount of power supplied by said motor driver to said pump motor according to said speed signal and said specified speed command value;
speed compensation means, coupled to said speed control means and to said load sensor, for maintaining a substantially constant flow rate through said pump; said speed compensation means including a positive feedback means for adjusting said specified speed command value according to said load signal and a specified base speed.
2. The flow-metered pumping system of claim 1, wherein said speed compensation means adjusts said specified speed command value in accordance with the following equation:
Specified Speed Command Value = Base Speed + (PumpLoad Threshold) * FlowGain when said pump motor load on said pump exceeds said Threshold, where PumpLoad is a pump motor load value corresponding to said load signal, Threshold is a predefined pump motor load threshold value and FlowGain is a predefined positive feedback gain value.
Specified Speed Command Value = Base Speed + (PumpLoad Threshold) * FlowGain when said pump motor load on said pump exceeds said Threshold, where PumpLoad is a pump motor load value corresponding to said load signal, Threshold is a predefined pump motor load threshold value and FlowGain is a predefined positive feedback gain value.
3. The flow-metered pumping system of claim 1, wherein:
said pump motor consists of a permanent magnet DC motor; said load signal corresponding to pump motor current.
said pump motor consists of a permanent magnet DC motor; said load signal corresponding to pump motor current.
4. The flow-metered pumping system of claim 1, wherein:
said pump motor consists of a pulsed activation, permanent magnet DC motor;
said speed signal corresponds to pump motor back-emf.
said pump motor consists of a pulsed activation, permanent magnet DC motor;
said speed signal corresponds to pump motor back-emf.
5. The flow-metered pumping system of claim 2, wherein:
said pump motor consists of a pulsed activation, permanent magnet DC motor;
said load signal corresponds to pump motor current;
said speed signal corresponds to pump motor back-emf.
said pump motor consists of a pulsed activation, permanent magnet DC motor;
said load signal corresponds to pump motor current;
said speed signal corresponds to pump motor back-emf.
6. A flow-metered pumping system comprising:
motor driven air-backed diaphragm pump for pumping a liquid;
a load sensor coupled to said pump for generating a load signal corresponding to loading on said pump;
a speed sensor coupled to said pump for generating a speed signal corresponding to pump speed;
a speed control means, coupled to said pump, said load sensor and said speed sensor for maintaining a substantially constant flow of said liquid through said pump corresponding to a specified base pump speed; said speed control means including feedback means for modulating said pump speed according to said load signal, said speed signal and said specified base speed such that said pump speed is increased by said speed control means as said load signal increases in value.
motor driven air-backed diaphragm pump for pumping a liquid;
a load sensor coupled to said pump for generating a load signal corresponding to loading on said pump;
a speed sensor coupled to said pump for generating a speed signal corresponding to pump speed;
a speed control means, coupled to said pump, said load sensor and said speed sensor for maintaining a substantially constant flow of said liquid through said pump corresponding to a specified base pump speed; said speed control means including feedback means for modulating said pump speed according to said load signal, said speed signal and said specified base speed such that said pump speed is increased by said speed control means as said load signal increases in value.
7. The flow-metered pumping system of claim 6, wherein said feedback means modulates said pump speed in accordance with the following equation:
Pump Speed = Base Speed + (PumpLoad - Threshold) *
FlowGain when said loading on said pump exceeds said Threshold, where PumpLoad is a pump load value corresponding to said load signal, Threshold is a predefined pump load threshold value and FlowGain is a predefined positive feedback gain value.
Pump Speed = Base Speed + (PumpLoad - Threshold) *
FlowGain when said loading on said pump exceeds said Threshold, where PumpLoad is a pump load value corresponding to said load signal, Threshold is a predefined pump load threshold value and FlowGain is a predefined positive feedback gain value.
8. The flow-metered pumping system of claim 6, wherein:
said pump motor consists of a pulsed activation, permanent magnet DC motor;
said speed signal corresponds to pump motor back-emf.
said pump motor consists of a pulsed activation, permanent magnet DC motor;
said speed signal corresponds to pump motor back-emf.
9. The flow-metered pumping system of claim 6, wherein:
said pump motor consists of a pulsed activation, permanent magnet DC motor;
said load signal corresponds to pump motor current.
said pump motor consists of a pulsed activation, permanent magnet DC motor;
said load signal corresponds to pump motor current.
10. The flow-metered pumping system of claim 7, wherein:
said pump motor consists of a pulsed activation, permanent magnet DC motor;
said load signal corresponds to pump motor current;
said speed signal corresponds to pump motor back-emf.
said pump motor consists of a pulsed activation, permanent magnet DC motor;
said load signal corresponds to pump motor current;
said speed signal corresponds to pump motor back-emf.
11. A method of flow-metered pumping consisting of:
providing an air-backed diaphragm pump for pumping a liquid;
operating a pump motor for driving said pump, said pump motor including a motor driver for supplying power to said pump motor;
measuring pump motor speed;
generating a speed signal corresponding to said pump motor speed:
maintaining said pump motor speed at a specified speed command value, including modulating the amount of power supplied by said motor driver to said pump motor according to said speed signal and said specified speed command value;
measuring pump motor load; and maintaining a substantially constant flow rate through said pump, including adjusting said specified speed command value according to said measured load and a specified base speed.
providing an air-backed diaphragm pump for pumping a liquid;
operating a pump motor for driving said pump, said pump motor including a motor driver for supplying power to said pump motor;
measuring pump motor speed;
generating a speed signal corresponding to said pump motor speed:
maintaining said pump motor speed at a specified speed command value, including modulating the amount of power supplied by said motor driver to said pump motor according to said speed signal and said specified speed command value;
measuring pump motor load; and maintaining a substantially constant flow rate through said pump, including adjusting said specified speed command value according to said measured load and a specified base speed.
12. The method of claim 11, wherein said step of maintaining a substantially constant flow rate includes adjusting said specified speed command value in accordance with the following equation:
Specified Speed Command Value = Base Speed + (PumpLoad Threshold) * FlowGain when said load on said pump motor exceeds said Threshold, where PumpLoad is said measured pump motor's load, Threshold is a predefined load threshold value and FlowGain is a predefined positive feedback gain value.
Specified Speed Command Value = Base Speed + (PumpLoad Threshold) * FlowGain when said load on said pump motor exceeds said Threshold, where PumpLoad is said measured pump motor's load, Threshold is a predefined load threshold value and FlowGain is a predefined positive feedback gain value.
13. The method of claim 11, wherein:
said pump motor consisting of a pulsed activation, permanent magnet DC motor;
said load measuring step including measuring pump motor current;
said speed measuring step including measuring pump motor back-emf.
said pump motor consisting of a pulsed activation, permanent magnet DC motor;
said load measuring step including measuring pump motor current;
said speed measuring step including measuring pump motor back-emf.
14. A method of flow-metered pumping consisting of:
providing an air-backed diaphragm pump for pumping a liquid;
operating a pump motor for driving said pump; said pump motor including a motor driver for supplying power to said pump motor;
measuring pump motor load;
measuring pump motor speed;
maintaining a substantially constant flow rate through said pump, including modulating said pump motor speed according to measured load, said measured speed and a specified base flow rate such that said pump motor speed is increased as said measured load increases.
providing an air-backed diaphragm pump for pumping a liquid;
operating a pump motor for driving said pump; said pump motor including a motor driver for supplying power to said pump motor;
measuring pump motor load;
measuring pump motor speed;
maintaining a substantially constant flow rate through said pump, including modulating said pump motor speed according to measured load, said measured speed and a specified base flow rate such that said pump motor speed is increased as said measured load increases.
15. The method of claim 14, wherein said step of maintaining a substantially constant flow rate includes adjusting said specified speed command value in accordance with the following equation:
Specified Speed Command Value = Base Speed + (PumpLoad Threshold) * FlowGain when said load on said pump motor exceeds said Threshold, where PumpLoad is said measured pump motor load, Threshold is a predefined load threshold value and FlowGain is a predefined positive feedback gain value.
Specified Speed Command Value = Base Speed + (PumpLoad Threshold) * FlowGain when said load on said pump motor exceeds said Threshold, where PumpLoad is said measured pump motor load, Threshold is a predefined load threshold value and FlowGain is a predefined positive feedback gain value.
16. The method of claim 14, wherein:
said pump motor consisting of a pulsed activation, permanent magnet DC motor, said load measuring step including measuring pump motor current;
said speed measuring step including measuring pump motor back-emf.
said pump motor consisting of a pulsed activation, permanent magnet DC motor, said load measuring step including measuring pump motor current;
said speed measuring step including measuring pump motor back-emf.
17. The flow-metered pumping system of claim 1, wherein said speed control means and said speed compensation means modulate said amount of power supplied by said motor driver and adjust said specified speed command value, respectively, multiple times within any 0.3 second period.
18. The flow-metered pumping system of claim 6. wherein said speed control means and said speed compensation means modulate said amount of power, supplied by said motor driver and adjust said specified speed command value, respectively, multiple times within any 0.3 second period.
19. The flow-metered pumping method of claim 11, wherein said maintaining steps are performed multiple times within any 0.3 second period.
20. The flow-metered pumping method of claim 14, wherein said maintaining step is performed multiple times within any 0.3 second period.
21. A flow-metered pumping system for regulating the flow of liquid cleaning chemicals to at least one washing machine, each said washing machine having an inlet for receiving said liquid cleaning chemicals, said flow-metered pumping system comprising:
at least one flow-metering unit, each of which includes:
at least one air-backed diaphragm pump for pumping liquid cleaning chemicals into said inlet of each of a group of said washing machines associated with said flow metering unit, each said pump including:
a pump motor for driving said pump, said pump motor including a motor driver for supplying power to said pump motor;
a speed sensor, coupled to said pump motor, for generating a speed signal corresponding to pump motor speed;
and a load sensor, coupled to said pump motor, for generating a load signal corresponding to pump motor load;
speed control means, coupled to said motor driver and to said speed sensor of said at least one air-backed diaphragm pump, for maintaining said pump motor speed at a specified speed command value; said speed control means including a negative feedback means for modulating the amount of power supplied by said motor driver to said pump motor according to said speed signal and said specified speed command value; and speed compensation means coupled to said speed control means and to said load sensor of said at least one pump, for maintaining a substantially constant flow rate of said liquid cleaner chemical through said at least one pump; said speed compensation means including a positive feedback means for adjusting said specified speed command value according to said load signal and a specified base speed.
at least one flow-metering unit, each of which includes:
at least one air-backed diaphragm pump for pumping liquid cleaning chemicals into said inlet of each of a group of said washing machines associated with said flow metering unit, each said pump including:
a pump motor for driving said pump, said pump motor including a motor driver for supplying power to said pump motor;
a speed sensor, coupled to said pump motor, for generating a speed signal corresponding to pump motor speed;
and a load sensor, coupled to said pump motor, for generating a load signal corresponding to pump motor load;
speed control means, coupled to said motor driver and to said speed sensor of said at least one air-backed diaphragm pump, for maintaining said pump motor speed at a specified speed command value; said speed control means including a negative feedback means for modulating the amount of power supplied by said motor driver to said pump motor according to said speed signal and said specified speed command value; and speed compensation means coupled to said speed control means and to said load sensor of said at least one pump, for maintaining a substantially constant flow rate of said liquid cleaner chemical through said at least one pump; said speed compensation means including a positive feedback means for adjusting said specified speed command value according to said load signal and a specified base speed.
22. The flow-metered pumping system of claim 21, wherein said speed control means and said speed compensation means modulate said amount of power supplied by said motor driver and adjust said specified speed command value, respectively, multiple times within any 0.3 second period.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US12716293A | 1993-09-27 | 1993-09-27 | |
| US127,162 | 1993-09-27 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2171716A1 CA2171716A1 (en) | 1995-04-06 |
| CA2171716C true CA2171716C (en) | 1999-03-23 |
Family
ID=22428628
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002171716A Expired - Lifetime CA2171716C (en) | 1993-09-27 | 1994-09-20 | Flow-metered pumping with load compensation system and method |
Country Status (12)
| Country | Link |
|---|---|
| US (1) | US5509788A (en) |
| EP (1) | EP0720693B1 (en) |
| JP (1) | JPH09505863A (en) |
| AT (1) | ATE166702T1 (en) |
| AU (1) | AU698430B2 (en) |
| BR (1) | BR9407705A (en) |
| CA (1) | CA2171716C (en) |
| DE (1) | DE69410623T2 (en) |
| ES (1) | ES2117801T3 (en) |
| PL (1) | PL174818B1 (en) |
| WO (1) | WO1995009305A1 (en) |
| ZA (1) | ZA947491B (en) |
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- 1994-09-20 JP JP7510025A patent/JPH09505863A/en active Pending
- 1994-09-20 BR BR9407705A patent/BR9407705A/en not_active IP Right Cessation
- 1994-09-20 PL PL94313700A patent/PL174818B1/en unknown
- 1994-09-20 DE DE69410623T patent/DE69410623T2/en not_active Expired - Lifetime
- 1994-09-20 WO PCT/CA1994/000517 patent/WO1995009305A1/en active IP Right Grant
- 1994-09-20 CA CA002171716A patent/CA2171716C/en not_active Expired - Lifetime
- 1994-09-20 ES ES94928220T patent/ES2117801T3/en not_active Expired - Lifetime
- 1994-09-20 AT AT94928220T patent/ATE166702T1/en not_active IP Right Cessation
- 1994-09-20 EP EP94928220A patent/EP0720693B1/en not_active Expired - Lifetime
- 1994-09-20 AU AU77356/94A patent/AU698430B2/en not_active Expired
- 1994-09-26 ZA ZA947491A patent/ZA947491B/en unknown
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1995
- 1995-08-16 US US08/515,750 patent/US5509788A/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| CA2171716A1 (en) | 1995-04-06 |
| PL174818B1 (en) | 1998-09-30 |
| DE69410623T2 (en) | 1998-10-15 |
| AU7735694A (en) | 1995-04-18 |
| JPH09505863A (en) | 1997-06-10 |
| DE69410623D1 (en) | 1998-07-02 |
| ATE166702T1 (en) | 1998-06-15 |
| PL313700A1 (en) | 1996-07-22 |
| EP0720693B1 (en) | 1998-05-27 |
| US5509788A (en) | 1996-04-23 |
| AU698430B2 (en) | 1998-10-29 |
| BR9407705A (en) | 1997-02-04 |
| WO1995009305A1 (en) | 1995-04-06 |
| ZA947491B (en) | 1995-05-15 |
| ES2117801T3 (en) | 1998-08-16 |
| EP0720693A1 (en) | 1996-07-10 |
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