WO2009094498A1

WO2009094498A1 - Methods and apparatus for homing and synchronization

Info

Publication number: WO2009094498A1
Application number: PCT/US2009/031764
Authority: WO
Inventors: Adnanul Haq; Richard Schoeneck
Original assignee: Douglas Machine, Inc.
Priority date: 2008-01-26
Filing date: 2009-01-23
Publication date: 2009-07-30

Abstract

An apparatus and method for homing and synchronizing various drive modules (12, 14) for a carrier tape (10) of an instrument (100) initially establishes a phase offset (Pm) and path length (Xm) for each module (12, 14) incorporated into the instrument (100), either before or after homing of the modules (12, 14). In particular, with knowledge of the overall tape path length (Xu) associated with the instrument (100) based on the various individual module path lengths (Xm), a phase offset (Pm) for each drive module (12, 14) relative to the total path length (Xu) for the tape (10) is determined through the use of position sensors (102) provided on the modules (12, 14). From this information, a consensus position is calculated and used to shift the drive pins (18) of the various modules (12, 14) during synchronization. In this fashion, the individual modules (12, 14) are assured to be synchronized to properly interact with and drive the tape (10) during operation of the instrument (100).

Description

Methods and Apparatus for Homing and Synchronization

BACKGROUND

The present invention generally relates to homing and synchronization, particularly relates to methods and apparatus for homing and synchronization of carrier tape, and specifically relates to methods and apparatus for carrier tape homing and synchronization which initialize the carrier tape position within each module of a high-throughput screening instrument (HTSI), synchronize the tape between modules and prevents tape over-stretching or buckling while homing. The function of a tape drive is to move a carrier tape horizontally (X-direction) through an instrument including multiple modules and which are functionally interconnected. Each module controls its own section of the tape drive, known as the Tape-X axis. A carrier tape, which is perforated on both sides, propagates from one module to the next module on belts. As the leading edge of the tape reaches the end of a module, the challenge is to enable a smooth transfer to the next module in series. The individual Tape-X axes of all the modules would preferably be seamlessly synchronized with each other so the tape drive becomes a single monolithic system for transporting the tape. Ideally, the overall operation should be flexible enough to handle addition or removal of modules from the overall tape drive, even where the tape is already loaded across the drives at startup. Furthermore, the performance-heads (multi-tip dispenser, scanning head, etc.) on each module require wells of the tape to be in a specific physical location for correct operation. The problem is the following:

1) Initializing tape-home position within each individual Tape-X axis to determine correct well position.

2) Synchronizing the tape 10 across a given number of Tape-X axes.

3) Ability to perform initializing and synchronizing while tape 10 is already loaded across the drives.

SUMMARY The present invention solves this problem and other needs in the field of homing and synchronization of individual modules in an instrument performing operations on a continuous carrier tape, in preferred aspects, by initially establishing a phase offset and path length for each module incorporated into the instrument. If data on each phase offset and path length is not known, a homing of the drive pins associated with the modules is performed and then the phase offset and path length information is reestablished. In particular, with knowledge of the overall tape path length associated with the instrument based on the various individual module path lengths, a phase offset for each drive module relative to the total path length is determined through the use of position sensors provided on the modules. From this information, a consensus position is calculated and used to shift the drive pins of the various modules during synchronization. In this fashion, the individual modules are assured to be synchronized to properly interact with and drive the tape during operation of the instrument.

The present invention will become clearer in light of the following detailed description of illustrative embodiments of this invention described in connection with the drawings.

DESCRIPTION QF THE DRAWINGS The illustrative embodiments may best be described by reference in the accompanying drawings where:

Figure 1 shows a perspective view of a tape drive utilizing the tape homing and synchronization method according to the preferred teachings of the present invention.

Figure 2 shows a front view of the tape drive of Figure 1. Figure 3 shows a diagram illustrating the method of the present invention.

Figure 4 shows a diagram illustrating a total unit path through an instrument formed of multiple modules.

Figures 5, 6, and 6 A diagrammatically illustrate homing and synchronizing methods of operation of the present invention. All figures are drawn for ease of explanation of the basic teachings of the present invention only; the extensions of the figures with respect to number, position, relationship, and dimensions of the parts to form the preferred embodiments will be explained or will be within the skill of the art after the following description has been read and understood. Further, the exact dimensions and dimensional proportions to conform to specific force, weight, strength, and similar requirements will likewise be within the skill of the art after the following description has been read and understood. Where used in the various figures of the drawings, the same numerals designate the same or similar parts. Furthermore, when the terms "top", "bottom", "first", "second", "forward", "rearward", "reverse", "front", "back", "height", "width", "length", "end", "side", "horizontal" "vertical", and similar terms are used herein, it should be understood that these terms have reference only to the structure shown in the drawings as it would appear to a person viewing the drawings and are utilized only to facilitate describing the illustrative embodiments. DESCRIPTION OF THE PREFERRED EMBODIMENTS

An apparatus for tape homing and synchronization, according to the preferred teachings of the present invention, is shown in the drawings for an instrument generally designated 100. In general, instrument 100 includes a tape drive employed to move a carrier tape 10 horizontally (X-direction) through instrument 100 including multiple modules 12 and 14 which are functionally interconnected. In this regard, only two modules 12 and 14 are shown for purposes of explanation, with it being understood that the instrument 100 would include several such modules 12 and 14, and in particular, in most forms, more than two modules 12 and 14. Each module 12 and 14 controls its own section of the tape drive, known as the Tape-X axis. The Tape-X axis includes a drive mechanism having a pair of parallel motor-driven metal belts 16 with pins 18 fastened on them. The carrier tape 10, which is perforated on both sides, propagates from one module 14 to the next module 12 on these belts.

As the leading edge of the tape 10 reaches the end of a module 14, the challenge is to enable a smooth transfer to the next module 12 in series. In accordance with the invention, the individual Tape-X axes of all the modules 12 and 14 are seamlessly synchronized with each other so the tape drive becomes a single monolithic system for transporting the tape 10 from one end of the instrument 100 to the other. As will become more fully apparent below, the invention provides for enough flexibility to handle the addition or removal of modules 12 and 14 from the instrument 100, even in the case where the tape 10 is already loaded across the drives at startup of the instrument 100. With this arrangement, wells of the tape will advantageously be in a specific physical location for correct operation of the performance-heads (multi-tip dispenser, scanning head, etc.) on each module 12 and 14. The spacing (Xp) of the pins 18 on the belt 16 is a precise multiple of the perforation spacing (Xt) on the tape (particularly note Figure 4). The distance between corresponding wells and successive well arrays (Xa) is also a precise multiple of spacing Xt. Spacing Xt is, therefore, a defining parameter of the instrument 100 as a whole. The web path through each module 12 and 14 has a path length Xm. The Xm path length does not need to be an integer multiple of spacing Xt, the tape drive pitch. It is only required that the path length Xm is known. The path length Xm within a module 12 or 14 could also be variable using another mechanism such as a festoon. Again, the path length Xm must only be known for each module 12 and 14. Different modules 12 or 14 can have different path lengths Xm .

When the instrument 100 is assembled from a plurality of modules 12 and 14, the total unit path Xu is formed by the serial connection of paths XmI + XmI + Xm3, etc. The path Xu can be divided into equal increments of spacing Xt, with each sub path Xm making up a portion. If spacing Xt is referenced from the beginning of unit path Xu, all of the subsequent positions of spacing Xt along the path Xu will be defined. If the start reference of spacing Xt is adjusted, it defines a phase offset from the zero reference of the unit path Xu. The phase offset can range from zero, up to a maximum of spacing Xt where the pattern will repeat.

Each module 12 and 14 is capable of having an independent drive with pins 18 that interface with the tape drive holes having spacing Xt. Within each module 12 and 14, the phase relationship between the drive pins 18 of the drive and the path Xm must be known. For example, if the drive pulley is at zero degrees, then the drive pins 18 are defined to be at 90 degrees phase Pm with respect to the zero reference for path Xm. Many methods for determining the phase Pm of the drive pins 18 within the module 12 and 14 are possible. For example, absolute encoder providing drive shaft angle, then adding an equipment specific phase offset, then converting to Xt cycles using modulo function, the remainder is the phase Pm.

Once the phase of every independent drive of modules 12 and 14 is known, the lengths of paths Xm of individual modules 12 and 14 can be used to calculate the phase offset Em for each drive relative to the path Xu. It is the phase of each drive relative to the path Xu that is plotted on the consensus graph in Figure 3. The phase offset Em of the individual drives are therefore compared relative to a common reference as if having a continuous web through the entire path Xu.

Weighting the phases of the independent drives (based on a common phase reference) allows for coordinating an unlimited number of drives on the path Xu. The 'center-of-mass' weighting strategy is therefore a very simple, fast, and expandable method, allowing for independent programming with coordinated behavior. It is possible to assign different weights to drive mechanisms that would act as higher priority, or drives that should act as the 'primary' reference. In one preferred form, the drives are equally weighted. Only one center of mass can be determined on a single circle. Correspondingly, the longest phase offset required for any drive to move to the 'center of mass' phase is half a cycle (Xt/2).

Some drive mechanisms may have a restriction of only being able to move in the forward direction (i.e., a uni-directional drive as opposed to a bi-directional drive) because of the function performed. To synchronize multiple drives that cannot move backwards, a minimal forward correction move can be initiated simultaneously on all drives. The most minimal coordinated correction move without knowledge of the phase error of every drive is represented as Xt/2. Each drive will then move a distance ranging from zero to spacing Xt. Drives aligned with the consensus position will move a distance of Xt 12. Drives with a negative phase error would move a distance between zero and Xt/2. Drives with a positive phase error would move a distance between Xt/2 and Xt. The correction moves may be defined to take place more gradually over a longer distance. For example, minimal moves plus distance Xc. If the phase error of every drive is known, then, the smallest coordinated forward correction move will be equal to half of the distance between the most positive and most negative phase error. Specifically, according to a preferred form of the present invention, initializing within individual Tape-X axes is done via position sensors 102. Each module 12 and 14 rotates its Tape-X axis and a point on the moving drive is sensed on the stationary sensor 102. The location of this sensor 102 is precisely set in all modules 12 and 14. This operation results in a value for the offset of the phase Pm for the modules 12 and 14. This phase operation results in an error (Em) value for the modules 12 and 14. This error value is the distance needed to get the wells to the required point. Since each module 12 and 14 has its own unique error {Em) value, a simple synchronization would call each module 12 and 14 to move its Tape-X drive Em units. After synchronization, the distance between corresponding pins 18 on successive modules 12 and 14 will be a multiple of Xt. This ensures that a belt pin 18 will always slide into a perforation of the tape 10 correctly on all modules 12 and 14 as the tape transfers between them.

It should be realized that the above operation may not be suitable for the situation where the tape 10 is already present on the drive before initialization. Since 0 < Em <Xt, unwanted stretching or bulging of the tape 10 between modules 14 and 12 can be created. One example is two modules 12 and 14 with Em values 0 and Xt. In this case, one of the modules 12 and 14 will travel Xt extra units while synchronizing. Further recognized in accordance with the present invention is that the Em values can be visualized as lying on a circle of radius Xt/2π and a position of consensus can be determined to which each of the modules 12 and 14 can move their respective Tape-X axes. This position is trigonometrically calculated, and each module 12 and 14 is then moved to this position. The maximum stretch or bulge of the tape 10 that can now occur is 0.5 *Xt. However, it is important to note that even in this worst case, bulge is extremely unlikely if the tape 10 was already loaded on the instrument 100. The presence of the tape 10 would indicate that the tape 10 must be really close to synchronicity and therefore would only need a small correction. In Figure 3, the bigger dot PC shows the consensus position for the indicated Em values.

In a method of operation as shown in Figure 5, each module 12 and 14 of the instrument 100, after starting step 300, checks whether the phase offset Pm and the path length Xm are known at step 302. If not known, homing of the pins 18 is checked at step 304. If the pins 18 are not homed, it is determined whether motion is required for homing at step 306. If homing motion is required, a report is given to the controller of the instrument 100 at step 350. At step 352, modules 12 and 14 wait for a synchronized homing command from the controller of the instrument 100. When the synchronized homing command is received, synchronized homing motion is performed at step 354. If homing motion is not required at step 306, absolute encoder homing is performed at step 308. After steps 308 or 354, the phase offset Pm and path length Xm are calculated at step 310. The programming formulas for phase offset Pm and path length Xm in the preferred form can be expressed as:

Pm = (DrivePos) MOD Xt

Xm = PathLength With phase offset Pm and path length Xm known from step 302 or 310, they are reported to the controller for the instrument 100 at step 360, with this operation ending at step 362.

In a method of operation as shown in Figure 6, the controller of the instrument 100 begins operation at starting step 200 and checks whether reports of step 360 have been received from all modules 12 and 14 at step 260. If not all reporting, it is checked whether reports from step 350 have been received from any module 12 or 14 at step 250. If no reports have been received, operation returns to step 260. If reports of step 350 have been received, a synchronized homing command is sent to all modules 12 and 14 at step 252, with modules 12 and 14 receiving such command at step 352. At step 254, it is checked whether homing has been completed at all modules 12 and 14. After homing has been completed at all modules 12 and 14, operation returns to step 260.

After reports of step 260 have been received from all modules 12 and 14, the phase error Em is calculated for all modules 12 and 14 at step 262. The programming formulas calculating the error Em for modules 12 and 14 in the preferred form are: EmX = (Xt- Pm 1) MODX/; Em I = (Xm X -Pm I) MOD Xt; Em 3 = ((Xm X +Xm I) - Pm 3) MOD Xt; Em 4 = ((Xm 1 + Xm 2 + Xm 3) - Pm 4) MOD Xt; etc. for modules 12 and 14 in the instrument 100. Next, the consensus position PC is calculated at step 264. The programming formulas for calculating the consensus position in the preferred form is: x =Xt 12π

SumX =COS(Em X / r) * WmX + COS(Em 2 1 r) * Wm 2 + COS(Em 3 / r) * Wm 3 + ...

SumY =SIN(Em W r) * Wm X + SIN (Em 2 / r) * Wm 2 + SIN(Em 3 / r) * Wm 3 + ...

(Where Wm is the weighting factor for each module.)

IF SumX > 0 AND SumY >= 0 THEN Cθ =ATAN(SumY / SumX)

ELSEIF SumX < 0 AND SumY >= 0 THEN Cθ =ATAN(SumY / SumX) + π ELSEIF SumX < 0 AND SumY <= 0 THEN

Cθ =ATAN(SumY / SumX) + π ELSEIF SumX > 0 AND SumY <= 0 THEN Cθ =ATAN(SumY / Sum X) + 2π

ELSEIF SumX = 0 AND SumY >= 0 THEN

Cθ = πl 2 ELSE

Cθ = -πl 2 ENDIF

PC =r * Cθ.

Synchronized correction movement commands are sent to all modules 12 and 14 at step 280, and this operation ends at step 298.

In preferred forms of the present invention as shown in Figure 6A, step 280 is accomplished by calculating the minimum bi-directional correction moves at step 282. The programming formulas calculating the minimum bi-directional correction moves at step 282 in the preferred form are as follows: MmI = (Em 1 - PC + Xt) MOD Xt IF MmI > (Xt 12) THEN MmI = MmI - Xt Mm2 = (Em2 - PC + Xf) MOD Xt

IF Mm2 > (Xt 12) THEN Mm2 = Mm2 - Xt Mm3 = (EmI - PC + Xt) MOD Xt IF Mm3 > (Xt 12) THEN Mm3 = Mm3 - Xt Etc. for all modules. Next, it is determined whether any of the modules 12 and 14 are constrained to move forward only at step 284. If some modules 12 and 14 are constrained to move forward only, the minimum forward correction move is calculated at step 286. The programming formulas calculating the minimum forward correction moves at step 286 in the preferred form are as follows: Min = 0

IfMmI < Min THEN Min = MmI If Mm2 < Min THEN Min = Mm2

If Mm3 < Min THEN Min = Mm3

Etc. for all modules.

MmI = MmI - Min Mm2 = Mm2 - Min

Mm3 = Mm3 - Min

Etc. for all modules.

The correction move offset is added to the correction moves of step 284 or 286 at step 288, with the programming formulas calculating adding an offset to the correction moves at step 288 in the preferred form are as follows:

MmI = MmI + Xc

Mm2 = Mm2 + Xc

Mm3 = Mm3 + Xc

Etc. for all modules. Next, the synchronous correction moves are sent to all modules 12 and 14 at step 290.

Based on the above, it should be readily apparent that the present invention provides for the effective and efficient initializing of tape positioning, as well as homing and synchronization of a tape across a plurality of modules of an overall instrument when either the tape is being initially loaded or while the tape is already loaded across drives of the modules.

Thus since the invention disclosed herein may be embodied in other specific forms without departing from the spirit or general characteristics thereof, some of which forms have been indicated, the embodiments described herein are to be considered in all respects illustrative and not restrictive. The scope of the invention is to be indicated by the appended claims, rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.

Claims

1. Method for homing and synchronizing a plurality of modules used to drive a common tape of an instrument comprising: establishing an overall path length based on a sum of path lengths of the plurality of modules; determining a phase offset for each module of the plurality of modules incorporated into the instrument relative to the overall path length; and synchronizing the plurality of modules by making a coordinated correction to the plurality of modules based on respective phase offsets.

2. The method of claim 1 further comprising homing of drive pins of at least select ones of the plurality of modules prior to determining the phase offset for the select ones of the plurality of modules.

3. The method of claim 2 with the establishing of the overall path length being performed after the homing of the select ones of the plurality of modules.

4. The method of claim 1 with the determining of the phase offsets for the plurality of modules incorporated into the instrument constitutes sensing the phase offsets through the use of position sensors mounted on the plurality of modules.

5. The method of claim 1 further comprising calculating a consensus position based on the phase offsets from each of the plurality of modules and utilizing the consensus position in making the coordinated correction.

6. The method of claim 1 with making the coordinated correction including repositioning drives of the plurality of modules which have both positive and negative phase errors.

7. The method of claim 6 further comprising making the coordinated correction equal to one-half a distance between a most positive phase error and a most negative phase error.

8. The method of claim 1 further comprising establishing a minimum coordinated correction equal to one-half of a drive pitch.

9. The method of 1 further comprising determining if any module is constrained to move uni-directionally prior to synchronizing the plurality of modules.

10. The method of claim 9 wherein, if any of the plurality of modules is constrained to move uni-directionally, a minimum uni-directional correction move is calculated and, if none of the plurality of modules is constrained to move only uni- directionally, a minimum bi-directional correction move is calculated.

11. The method of claim 1 further comprising adding an offset to the correction offset of each of the plurality of modules.

12. An instrument for driving a tape comprising, in combination: a first module including a first drive mechanism having a first plurality of rotatable drive pins and establishing a first path length, a second module including a second drive mechanism having a second plurality of rotatable drive pins and establishing a second path length, a common tape extending about and being adapted to be simultaneously driven by both of the first and second drive mechanisms through an overall path length, a first position sensor provided on the first module for determining a first phase offset relative to the overall path length, a second position sensor provided on the second module for determining a second phase offset relative to the overall path length, and a controller for commanding a synchronization of the plurality of modules by making a coordinated correction to the plurality of modules based on the first and second phase offsets.

13. The instrument of claim 12 with each of the first and second position sensors being mounted in a stationary manner relative to a respective one of the first and second drive mechanisms.

14. The instrument of claim 12 with the controller also providing for homing of at least one of the first and second drive mechanisms prior to determining a respective one of the first and second phase offsets.

15. The instrument of claim 12 with the controller commanding synchronization based on a consensus position established in relation to the phase offsets from each of the plurality of modules.

16. The instrument of claim 12 with at least one of the first and second drive mechanism can move bi-directionally.

17. The instrument of claim 16 with at least one of the first and second drive mechanism only operated uni-directionally.