Linear Tape-Open (“LTO”) is a computer storage magnetic tape format developed as an alternative to the proprietary Digital Linear Tape (“DLT”) format. The LTO roadmap calls for successive increases in capacity and speed. Due to these targets and the need to maintain, and perhaps shrink, a small drive housing form-factor, printed circuit board real estate is becoming very valuable as the need to include additional components increases. Due to this, it is becoming challenging to fit various drive mechanisms, included in previous generation LTO drives, into newer designs.
Designing high bandwidth tracking servo systems, for use in LTO drives, presents the following technological challenges: high bandwidth amplifiers, faster sample rates for digital control algorithms, control of loop shaping to achieve robust and higher performance suppression capabilities, improved feedback sensors and high bandwidth actuators. Although each one of these is an important design or engineering task, the performance of the actuator basically limits the final tracking servo bandwidth. As a result, the actuator is often considered to be the most important requirement.
As discussed in more detail below, the claimed embodiments are directed to high bandwidth actuators. Some of the issues with high performance actuators are: minimizing moving mass, optimization of the working lateral range of motion and controlling the high order unwanted resonance frequencies above a minimum frequency that is determined based on the tracking servo bandwidth requirements.
In addition, drive form factors (for example LTO form factor requirements) and installation/mounting requirements are also a concern. Some computer industry requirements include the drive mounting configurations. For example, some computer manufactures specify a drive-mounting configuration requirement that the drive can be mounted on its lateral side or on its bottom side. The side-mounting configuration requires two sets of hole-patterns with a minimum screw length that will support the drive in a computer chassis. A typical screw length requirement is about 4 to 5 millimeters. In a LTO half-high drive (½ of the standard height of 3¼ inches) the pin threading mechanisms must be spaced away from the mounting screw. Thus, the actuator must fit between the pin threading mechanisms and the drive reel located in the back. The actuator must also fit in the limited space in the width dimension. Prior art actuator assemblies are typically not suitable for tape drives with smaller form factors where drive components are more tightly packed. In addition, some of the actuator configurations of the prior art force a lower 1st mode resonance frequency response at around 100 Hz. Generally, a lower 1st mode of the spring-mass system also results in a lower 2nd mode of resonance.
In view of the foregoing, a need exists in the art for a high bandwidth actuator that meets the above-described technological requirements.
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.
The following embodiments and aspects thereof are described and illustrated in conjunction with systems, apparatuses and methods which are meant to be exemplary and illustrative, not limiting in scope. In various embodiments, one or more of the above-described problems have been reduced or eliminated.
One embodiment by way of non-limiting example provides for a servo-controlled, head actuator design that has low profile characteristics in both the height and width dimensions. The low height allows the actuator to fit into a half-high tape drive form factor. The construction of the actuator, in one embodiment, reduces the width of the tape drive system, and allows the industry standard mounting with the necessary screw length. Additionally, in some implementations, the actuator comprises a smaller, concentrated moving mass coupled with a flexure construction having a narrowed width with added ribs for torsional stiffness. These aspects of the actuator provide a higher second mode of vibration compared to the flexure designs of the prior art. The actuator design includes a coarse actuator assembly for larger movements of the head, and a fine grain actuator, including a voice coil motor, responsive to analysis of servo signals. In some embodiments, the voice coil motor of the fine actuator and the coarse actuator shafts are in line. Since the centerlines of the shafts are in-line with the voice coil motor, the resonance response of the shaft spring-mass system is reduced.
In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the drawings and by study of the following descriptions.
Exemplary embodiments are illustrated in referenced figures of the drawings. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than limiting.
The following embodiments and aspects thereof are described and illustrated in conjunction with systems, apparatuses and methods which are meant to be exemplary and illustrative, not limiting in scope.
It should be noted that the phrases “fine actuator” and “moving mass” can be used interchangeably and generally refer to the following collection of parts: coarse actuator base 106, head carriage 104, magnetic head 102, voice coil motor 160 and top and bottom flexure springs (140,142/refer to
The fine actuator controls the head carriage assembly 102/104, relative to coarse actuator base 106, using a voice coil motor (VCM) assembly (see
The trigger point of the reference hall sensor magnet assembly 122 provides a known location for the head with respect to tape. The linear hall sensor magnet 124 (see
Regarding the reference hall sensor 800 (refer to
In reference to the linear hall sensor 124 and an associated dual pole magnet 125, the fine actuator of the head actuator assembly 100 is utilized to keep the head on a track under a servo control. It should be noted that the dual pole magnet 125 is only partly visible in
With reference to
Top flexure spring 140 further includes holes 180 that are utilized to secure top flexure spring 140 to the coarse actuator base 106 via additional screws (not shown). In one implementation, clamps may also be included with the screws. It should be noted that
As the head carriage 104 is secured to top flexure spring 140 via screws 176 and the top flexure is further secured to the coarse actuator base 106 via screws (not shown), it can be seen that head carriage 104 is mounted between opposing arms (106a, 106b) in area 103 of the coarse actuator base 106. Head carriage 104 is also coupled to the actuator base 106 via a bottom flexure spring 142. Similar to top flexure spring 140, bottom flexure spring 142 is coupled with the head carriage 104 at an inner set of holes 184 via a clamp 186 and screws 188 (note only one screw 188 is intentionally included in
Actuator assembly 100 has two separate resonance frequency vibration modes referred to as the first mode and the second mode. The first mode refers to up and down frequency vibrations of the actuator assembly and is generally low frequency. The second mode refers to torsional frequency vibration of the moving mass and is generally preferred to be kept as high as possible and preferably five to eight times higher than the closed-loop bandwidth frequency.
Top and bottom flexures springs 140 and 142 each further include various ribs 194 that are oriented perpendicular to each flexure. In one implementation, the top and bottom flexure springs 140 and 142 are metal springs that apply opposing forces to bias the head carriage 104 towards a center position relative to the fine actuator thus providing a resonance frequency dampening effect. In one implementation, flexure springs are 140 and 142 are made from 300 series stainless steel. The ribs 194 allow for reductions in the width of top and bottom flexure springs 140 and 142 while maintaining desired spring forces. This is accomplished because ribs 194 add torsional stiffness to the top and bottom flexure springs 140 and 142. Since the width of the flexures is reduced, the overall size of the actuator assembly 100 can be reduced accordingly to fit into a smaller drive enclosure. As previously indicated, it is also desirable to maintain a high second resonance mode. The placement of the top and bottom flexure springs 140 and 142 help to contribute the high second mode of vibration. The top and bottom flexure springs 140 and 142, in one implementation, are mounted to be substantially aligned with the center of gravity of the moving mass corresponding to the fine actuator. This can be seen, for example, via
Furthermore, under servo control, the voice coil motor 160 is electrically coupled with a corresponding magnetic circuit that generates a force required to move the magnetic head 102 such that it stays aligned with a particular track on a tape. A magnetic moment caused by the force can also excite the shafts 107 and their associated spring-mass system. Since the voice coil 160 is in-line with the shafts 107, the residual force of the moment arm is substantially zero and the resonance of the shaft's spring-mass system is also reduced substantially.
Another advantage of the claimed embodiments is that the flex cables 134 and 136 are mounted parallel to the tape travel path and this allows for further separation of the two flex cables. Laterally extending arms (104a, 104b/refer to
In one implementation, laterally extending arms (104a, 104b) form approximately 10 degree angles at either side of fork-shaped portion 103 as indicated by areas 906 and 908. Since the flex cables (134, 136) are attached to the laterally extending arms (104a, 104b), flex cable portions 134a and 136a (refer to
Advantageously, the claimed embodiments provide for a reduced fingerprint actuator assembly capable of fitting into next generation LTO tape drives. Additionally, a higher second mode vibration is achieved by placing flexures with ribs inline with the moving mass/fine actuator. Furthermore, the reduced footprint actuator assembly provides the required extra room in a tape drive housing for tape grabber mechanics as well as providing the option to install the housing in various orientations due to multiple sets of mounting holes for screws. More specifically, area 500 of drive 200 (refer to
Another advantage of the claimed embodiments is that a flat voice coil motor design is employed by the claimed embodiments. Prior art voice coils are typically circular. Using a circular voice coil results in an increased fine actuator moving mass. That increase in mass necessitates the use of wider flexures. In turn, wider flexures results in an enhanced width for the actuator as a whole. By using a flat voice coil, those prior art issues are avoided. Additionally, the flat voice coil contributes to the moving mass being concentrated in a small area which in turn helps to achieve the in-line/center of gravity aspects of the claimed embodiments.
While a number of exemplary aspects and embodiments have been discussed above, those of skill in the art will recognize certain modifications, permutations additions and sub-combinations thereof. It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions and sub-combinations as are within their true spirit and scope.
This application claims the benefit of U.S. Provisional Patent Application No. 60/804,223 filed on Jun. 8, 2006, which is incorporated herein by reference.
Number | Name | Date | Kind |
---|---|---|---|
5371636 | Nayak et al. | Dec 1994 | A |
5377052 | Guzman et al. | Dec 1994 | A |
5566039 | Spicer | Oct 1996 | A |
5793573 | Eckberg et al. | Aug 1998 | A |
5936804 | Riener et al. | Aug 1999 | A |
5949619 | Eckberg et al. | Sep 1999 | A |
6075678 | Saliba | Jun 2000 | A |
6404598 | Nayak et al. | Jun 2002 | B1 |
6411474 | Anderson | Jun 2002 | B1 |
6594118 | Nayak et al. | Jul 2003 | B1 |
6697229 | Tamura et al. | Feb 2004 | B2 |
6704169 | Nawa | Mar 2004 | B2 |
6765759 | Bhattacharya et al. | Jul 2004 | B2 |
7123450 | Villiard et al. | Oct 2006 | B1 |
7227724 | Nayak et al. | Jun 2007 | B2 |
7359259 | Poechmueller | Apr 2008 | B2 |
7420781 | Nayak et al. | Sep 2008 | B2 |
7474495 | Weng et al. | Jan 2009 | B2 |
20020041470 | Nayak et al. | Apr 2002 | A1 |
20020060884 | Nawa | May 2002 | A1 |
20040184195 | Nayak et al. | Sep 2004 | A1 |
Number | Date | Country | |
---|---|---|---|
20070285845 A1 | Dec 2007 | US |
Number | Date | Country | |
---|---|---|---|
60804223 | Jun 2006 | US |