CN101379558A

CN101379558A - Method of generating a position error signal, method of writing a data track, and method and apparatus for testing a head

Info

Publication number: CN101379558A
Application number: CNA200780004887XA
Authority: CN
Inventors: 迈克尔·阿兰·迈尔斯
Original assignee: Xyratex Technology Ltd
Current assignee: Seagate Systems UK Ltd
Priority date: 2006-02-10
Filing date: 2007-02-06
Publication date: 2009-03-04

Abstract

A method of generating a position error signal for a desired radial position of a read/write head relative to a data track of a disk (1) is disclosed. In the method the track has a plurality of servo bursts defining a plurality of servo nulls (108) for the track (101), the servo nulls being positioned such that there are servo nulls at more than four different radial positions relative to the track, the servo nulls defining a predetermined locus (24) e.g. aspiral, having a known position relationship with the track (101), the locus extending across the radial extent of the track (101) and a method for testing a read/write head.

Description

Produce the method and apparatus of the method for position error signal, the method that writes data-track and test magnetic head

The present invention relates to produce the method for position error signal, the method and apparatus that writes the method for data-track and be used to test magnetic head.

In various embodiments, the present invention relates generally to magnetic head dielectric tests equipment, for example general known conduct in this area " spin stand (spin-stands) ".

Spin stand (spin stands) is at first developed as the instrument that uses in the research and development process in the art, estimated and optimize with the performance of the various parts that allow disk drive, various mentioned components for example is magnetic head, disk and passage (channel).Also before fitteding to be the disk drive parts, tests disk drive manufacturing field use spin stand (spin stand) W head or the disk of each production now usually.

The typical testing apparatus that is known in the art comprises motor drive shaft and supporting assembly, the disk that can be write and be read by the magnetic head of being tested is installed on this motor drive shaft, and this supporting assembly is used to support the magnetic head of tested person and the magnetic head that " flies (flying) " on disk when rotation.This testing apparatus comprises that also the permission magnetic head is set at the layout on the disk.This layout generally includes and is used for the rough positioning device of head position in the lip-deep optional position of disk, for example X-Y positioning stage (stage).

Rough positioning device is used for usually the zone of the test tracks on disk to head position.Thin locating device (for example piezo-element actuator or similarly micro actuator) also is set usually to carry out the thin location of magnetic head.Thin locating device is used for seeking and positioning head in the central authorities of track, then with little increment from track centre " slight promote (microjog) " magnetic head.

When testing,, use thin locating device in orbit or cross over track positioning head in various radial positions then at first with the central authorities of head position at track.Test data is write track, subsequently with the various radial deflection amounts of magnetic head by magnetic head read test data.Usually, must carry out this through the repeatedly rotation of disk on each side-play amount reads to resist noise.Like this, a series of tests be can carry out, for example so-called bit error rate (BER) (BER) test (bathbub), track extruding, track centre, read/write offset etc. comprised.

Usually, the internal sensor of thin locating device with high precision is to determine the error between the desirable position that is input to thin locating device (so-called " position of indication ") and the physical location that reached by thin locating device.This error term can be fed back to be used for thin locating device control loop to reduce or eliminate any error and to obtain more accurate localization.Yet,, also exist system can't directly determine above-mentioned some errors of between desirable or the head skew amount of indicating and actual magnetic head side-play amount, introducing although thin locating device has this FEEDBACK CONTROL.This is illustrated in the location of the magnetic head on the various side-play amounts relevant with track centre actual is open loop.In practice, this is undesirable, because particularly can influence system from the noise of thermal drift from each provenance, the internal sensor that makes fine positioning put sensor can't " see " this error and therefore this system can't compensate this error, thereby cause error all being arranged in the side-play amount of obtaining hope with in the side-play amount that keeps wishing.

In order to address this problem, proposed to use servo track on the disk in the prior art with the location fully of the magnetic head on the disk that allows to determine.In this scheme, test tracks comprises two types data.First sets of data is the form of servo pulse (servo burst), and it is arranged with the form of the servo track that is divided into the sector usually.As known in the prior art, these effective servo pulses define the position of test tracks on disk, and these effective servo pulses are used to set up its position with respect to the magnetic head of track according to position error signal (PES) by magnetic head.Before being installed to disk in the testing apparatus, servo pulse can be write disk in advance.More at large, when disk is installed in the testing apparatus first, as the part that disk initialization is handled, can be by the pulse of magnetic head writing servo.Writing servo track in any case, identical probably servo track will be used to test a plurality of magnetic heads (common good hundreds of or several thousand magnetic heads) subsequently.

Second sets of data is a test data, and its servo pulse with the servo track that is divided into the sector is write by intersection.Again write and to read these data measured with the read that allows each magnetic head by each tested in equipment magnetic head.

To feed back to servo controller from the PES that servo pulse obtains at last, and use this PES to reduce any error in the indicating positions of the magnetic head error of thermal drift (for example owing to).

For example, the two all general configuration that discloses the servo scheme of this form of use in magnetic head dielectric tests equipment of US-B-6023145 and US-B-6538838.

In these schemes, the layout of servo track and be similar in final use the common working method of magnetic head positioning system in the head disk assembling in essence from the generation of the position error signal of servo track.Yet as will be described, owing to a plurality of reasons, this system is not suitable for being used in the head test equipment.

Figure 1A illustrates the servo pulse structure 2 with common prior art quadrature amplitude modulation.(for simply, linear track 1 is shown here, track 1 is same radially also concentricity with disk usually.) servo pulse structure 2 has the periodic magnetic transition of four series that are known as servo pulse: A-pulse, B-pulse, C-pulse and D-pulse (3a, b, c, d).In servo structure 2, write each servo pulse 3a, b, c, d repeating, and this each servo pulse has different radial deflection amount mutually at half track spaced radial.Usually, there are about 250 servo structure 2 around the track 1.Usually, each servo structure 2 around the track 1 also comprises unique track address (not shown), can be with the decoding of track address digit ground to provide the coarse position of servo structure 2.

When W head 4 (crossing the centre-line of track 5 shown in Figure 1A) passes track 1 and crosses servo pulse structure 2 when circumference flows, detect each servo pulse 3a, b, c, d according to this by magnetic head, and the generation signal, this signal have with magnetic head 4 radially with each pulse 3a, b, c, the overlapping proportional intensity of degree of d.Figure 1B illustrates how to obtain quadrature amplitude modulation (QAM) position error signal (PES) from these four signals.Two kinds of traces (trace) are acquired: first signal 6 that obtains from A and B pulse 3a, b equals (A-B)/(A+B); The secondary signal of obtaining from C and D pulse 3c, d 7 equals (C-D)/(C+D).

Shown in Figure 1B,

signal

6,7 provides Voltage Reference, and this Voltage Reference provides the measurement with respect to the radial position of track 1, magnetic head 4, and its each quadrant Q1, Q2, Q3, Q4 at track 1 is almost linear.As the part of demodulation process, selecteed pulse is to 3a, b; 3c, d provide linear signal 6 for the residing quadrant of magnetic head; 7 pulse is to (that is, being C and D for Q1, is A and B for Q2, or the like).Thereby no matter magnetic head 4 is in which quadrant among Q1, Q2, Q3, the Q4, all magnetic head 4 is produced suitable almost PES.Yet, even in each quadrant Q1, Q2, Q3, Q4, also will there be linear error to a certain degree, can be if do not proofread and correct these errors of these errors with in some error drawing-in systems.

In addition, this servo scheme is subjected to the influence of gain error probably.This is that variation by the width of the read element of tested magnetic head causes.Because manufacturing tolerance, the width of read element can have 20% variation.When using different magnetic heads to detect given servo pulse, thereby these variations of width can cause producing slight different signals and cause gain error.Two

trace

6a, 6b of first signal shown in Figure 1B are corresponding to the magnetic head read element of different in width 4a, the 4b shown in Figure 1A, and the influence (drawing respectively with solid line and broken string) of gain error is shown.

Should be appreciated that to exist some head positions relevant with track to make A=B of this place or C=D, promptly in this position, is identical from the signal of A pulse and B pulse or C pulse and D pulse detection.In this position, the gain of magnetic head and the linear accuracy that does not influence the signal that obtains from servo pulse.The position of A=B or C=D is called as " servo null (servo null) " 8.As can be seen from Fig 1B, for each quadrant Q1, Q2, Q3, Q4, in servo null 8 with in the position near servo null 8, usually signal is the most linear, and from servo null 8 position farthest, signal is least linear.

Should be noted that other servo burst arrangements also is possible, comprise for example servo pulse of width modulated and the servo pulse of phase modulation (PM).All these all run into the identical basic problem that is caused by nonlinearity erron and gain error.

Owing to only need magnetic head to follow track centerline (make usually track centerline consistent) usually, so be minor issue at terminal user's disk system neutral line and gain error with null position.Yet, as mentioned above, wish to keep these side-play amounts crossing to obtain on many positions of track in head skew amount and the repeatedly rotation at disk for head test.Thereby, in the head test process, passing and wishing high linearity, accuracy and repeatability in whole radial positions of track.And, feed back to performance and stability that linearity among the PES of closed loop servo controller and gain error influence controller unfriendly.And, because therefore magnetic head crooked in the final disk system of using can't follow optimum null.Thereby before using even take a long time of the linear and gain of characterization magnetic head for servo track.At the Magnetic Head test macro of the element of needs tests high-throughput, this does not make us accepting.

For the servo track arrangement by prior art alleviates above-mentioned intrinsic problem to a certain extent, prior art proposes should be to each magnetic head of servo track characterization before test.Usually this is by seeking orbit centre, slightly promote the zone that magnetic head passes track then, and the linearity of calibration magnetic head and gain carry out, to eliminate the error in the drawing-in system.Yet because the matter of time that will spend with respect to each tested magnetic head of servo track characterization on tested media, such characterization is unpractiaca in the product test environment.

The US-B-6023145 teaching a kind of slightly different servo scheme.In the method, the internal sensor that at first uses micro positioner magnetic head is moved to indication the position as a reference.In the position of this indication, read servo pulse by magnetic head, and according to through disk repeatedly rotation read to determine position error term and be stored in the storer.Then, even all the position in hope is locked when having thermal drift in order to allow magnetic head, use location error term is as the reference value of controller.Yet this method has a shortcoming: need the rotation many times of disk to come enough accurately calculating location error term so that appropriate reference value to be provided.This makes that this method only is adapted at most researching and developing in the laboratory using, and more can be received in there in a large amount of rotations of disk magnetic head is remained on identical radial position, thereby providing the enough time accurately determines position error term.On the contrary, in production environment, a complete cover test more likely is performed on magnetic head.This requirement will repeatedly slightly be promoted magnetic head leap track and be set up minisize track profile (profile), bit error rate (BER) test failure (BER bathtub) etc.Therefore, be very slow in each locational tediously long calibration process that is slightly promoted.Because test speed directly influences the handling capacity of tested element and therefore influences production cost, so test speed is a particular importance in production environment.Owing to these reasons, the method among the US-B-6023145 is unsuitable for carrying out these tests in the production test.

Except the problems referred to above of the prior art, the general trend in the disk drive technology is the width that reduces magnetic head and track.If this trend continues, then can aggravate the problems referred to above.

Owing to these reasons, when the test magnetic head, the radial zone that prior art can not be passed needed track provides point-device position control, and/or need elapsed time that the servo pulse characterization that is written into disk is tested each magnetic head, so the known servo techniques of magnetic disk servo design field helps limited in spin stand (spin stand).

According to a first aspect of the invention, a kind of method is provided, this method produces position error signal to W head with respect to the desirable radial position of data in magnetic disk track, wherein, this track has a plurality of servo pulses, a plurality of servo pulses are used to limit a plurality of servo null of this track, this servo null is located so that in the different radial position above four with respect to track and all has servo null, servo null limits desired trajectory, this desired trajectory and this track have known position relation, the radial zone that this track passes this track extends, this method comprises: (a) according to described known position relation, determine that correspondence and described magnetic head are with respect to the desirable radial position of track, target null position on the null loci; (b) use magnetic head to detect the position of at least one servo null; (c) determine the site error of magnetic head from described at least one servo null positions that is detected with respect to target null position; (d) produce position error signal according to described site error.

Top configuration provides position error signal, no matter which position magnetic head is in, do not consider whether magnetic head is carrying out track to the moving or pass and be used for track that BER measures or the miniscanning that passes track side surfaces (profile) of track, and this signal all can be used in the continuous feedback system of absolute position yet.This is to calculate in advance and obtain by be moved to target null will occur before its intended destination place at magnetic head.This target null is with respect to the absolute position on the disk of track, and this target null is used as the reference point that produces position error signal.Owing to use the absolute position, it is identical that the target in the feedback loop keeps, thus the advantage of bringing: even in the process of obtaining sample for calculating mean value when magnetic head passes track and slightly promotes, the mean value of a plurality of revolutions calculating PES that also can be by disk.On the contrary, in the system of US-B-6023145, must reset the interior target of this ring for each new position that disk is moved to, this acquisition time that need prolong is to produce satisfied reference value.

The motion that this configuration also allows magnetic head is changed into from a kind of stepping (step), the method (this is the current approach of carrying out the magnetic head dielectric tests) adjusting (settle) and read (read) and is a kind ofly passed through the method that writes the track moving head with constant speed, thereby has eliminated searching and adjustment time and further reduced the test duration.

Top configuration also has advantage: because the also misalignment mutually of track and track, the radial position meeting of therefore crossing over the interior servo null of radial zone of track changes.As previously mentioned, servo pulse be provided between head skew amount that measures in the zone (" range of linearity " that be called servo pulse here) of servo null and the actual head skew amount the most accurate, can repeat and linear relation.Therefore, has servo null by different radial position with respect to track, can make around the range of linearity of a plurality of servo null and cross over the track radial zone extension bigger than the servo configuration of prior art, in the servo configuration of prior art, the servo null and the range of linearity are radially aimed at.

Usually, this configuration has advantage: can obtain high-quality PES numerical value, and must be to each single magnetic head of the servo track characterization tested person of disk unlike prior art.When test, this has saved a large amount of time, therefore, in production environment, has reduced the cost of production disk drive parts.

In a preferred embodiment, step (b) comprises that detection is at least diametrically near the position of the servo null of magnetic head.This configuration has advantage: upwards near magnetic head and the servo null of the most accurate PES is provided, in any radial position of magnetic head with respect to track, magnetic head can obtain high-quality, PES repeatably based on the footpath.

In another preferred embodiment, step (b) comprises the position of detecting a plurality of servo null, and step (c) is included in carries out interpolation to seek described site error between described a plurality of null position.This allows to obtain higher accuracy by the interpolation of needing carrying out between discrete servo area structure, and to determine target null position, this position must be not consistent with servo null.Can also obtain bigger accuracy by between a large amount of servo samples, carrying out interpolation, come to seek the site error of magnetic head for the existence of resisting noise in the sample.

The mean value that calculates site error by the continuous rotation of disk is to produce position error signal.Calculate target null position between the new position in advance owing to moving at magnetic head, and produce the PES relevant with this target null, therefore in fact all the position PES for magnetic head have identical reference value.Therefore, before being transfused to servo controller, can calculating the mean value of PES by the continuous rotation of disk, and between moving, must not calibrate.This provides the higher accuracy in the PES signal and further resists noise.

In one embodiment, select the desirable radial position of magnetic head to be consistent with servo null.

In a most preferred embodiment, track and disk are concentricity, and a plurality of servo null have different radial positions along the circle spacing and on each circumferential position.

In a preferred embodiment, the position of servo null extends through most of radial zones of track at least.This has advantage: no matter what the radial position of magnetic head is, thereby all might and can obtain linear PES from this servo null at least near servo null.In a preferred embodiment, servo null has the radial position that evenly arranges.The circumferential position of servo null can evenly be arranged.This permission produces high-quality linear PES from servo pulse.In a preferred embodiment, is extending in the radial direction continuously along centering on the single of track the position of servo null.

In a preferred embodiment, the radial position of servo null linear change along with circumferential position.This has advantage: make the easier execution of interpolation between the room.

Preferably, servo pulse is formed in each servo sector of servo track of sectorization.This for example allows by servo sector recognizer (this recognizer can be read by magnetic head) is provided, or obtains the position of the circumference of servo pulse by the quantity Calculation that keeps the servo sector that magnetic head passes.

The position of servo null limits at least one spiral at least a portion of the servo null on the disk.This permission writes disk with single spiral servo track, and this servo track can be used to provide PES in any radial position of disk.This also provides advantage: writing spiral that can be continuous, thus can pass through the error writing servo track of the minimum that disk brings with the influence because of thermal drift.Preferably, spiral pitch (pitch) is the width of track.This provides the servo null of each track maximum quantity and bigger accuracy.

In another embodiment, servo null loci and disk are concentricity.Track can limit sine wave.Sine wave has the wavelength of the orbit circumference of equaling.A plurality of servo null loci can be written into disk.Track can be written into and make it comprise more than a servo null loci.

In one embodiment, disk initially is empty servo pulse, and described method comprises, in step (a) before, carries out the step that disk is write described servo pulse.

Servo pulse is the servo pulse of quadrature amplitude modulation preferably.Selectively, servo pulse can be the servo pulse of amplitude modulation(PAM) or the servo pulse of phase modulation (PM), or has any other servo pulse in room.

In one embodiment, provide a kind of method of testing W head, this method comprises: magnetic head is indicated to desirable position with respect to the track of disk; According to as mentioned above, the difference between the position of the physical location of magnetic head and hope is produced position error signal; Using the closed loop controller that is provided with to come the position of control head is 0 position error signal is reduced to essence; And test magnetic head.

According to a second aspect of the invention, a kind of method from data-track to disk that use W head to write is provided, part as the method for test magnetic head in magnetic head dielectric tests equipment, this disk has a plurality of servo pulses, this servo pulse defines the servo null more than four, this method comprises: write described data-track and make it consistent with described servo null more than four, thereby servo null limits the desired trajectory with known location relation relevant with track, and the radial zone that this track is crossed over track extends.

In a preferred embodiment, track and disk are concentricity, and a plurality of servo null have different radial positions along the circle spacing and on each circumferential position.The position of servo null can extended in the radial direction continuously along centering on the single of track.The radial position of servo null is linear the change along with circumferential position.The position of servo null limits at least one spiral at least a portion of the servo null on the disk.

In other embodiments, servo null loci and disk are concentricity.Track can limit sine wave.

In one embodiment, disk initially is empty servo pulse, and described method comprises, before writing the step of data-track, carries out the step that disk is write described servo pulse.

According to a third aspect of the invention we, a kind of equipment that is used to test W head is provided, this equipment comprises: disk, it has data-track, wherein, this track has a plurality of servo pulses, these a plurality of servo pulses limit a plurality of servo null of this track, this servo null be located so that with respect to this track more than four different radial positions on have servo null, servo null limits predetermined null loci, should be scheduled to null loci and this track and have known position relation, the radial zone that this track passes through this track extends; Steady arm is used for the described magnetic head in location in the radial position on the disk; Processor is provided for: (a) receive the desirable radially head position with respect to track; (b), determine corresponding to described magnetic head with respect to the target null position desirable radial position of track, on the null loci according to described known position relation; (c) use magnetic head to detect the position of at least one servo null; (d) determine site error from least one detected servo null positions with respect to the magnetic head of target null position; And (e) according to site error generation position error signal; And feedback controller, be provided for receiving described position error signal as the feedback input, and make described steady arm locate described magnetic head, be 0 thereby described position error signal is reduced to essence.

According to a forth aspect of the invention, a kind of disk is provided, it has at least one circular shape concentric track, this track has a plurality of servo pulses, these a plurality of servo pulses limit a plurality of servo null of track, thereby this servo null is positioned and has servo null relevant with this track on more than four different radial positions, servo null limits the spiral at least a portion on the disk, this spiral at least a portion and this track have known position relation, and the radial zone that this track passes this track extends

According to a fifth aspect of the invention, provide a kind of method of the test W head that is suitable for using in disk drive, this method comprises: corresponding to the track on the disk, and positioning head in the radial position of spinning disk medium; The position of periodic movable signal indication magnetic head, thus the radial position of magnetic head along periodic path movement, if disk rotation m changes then this magnetic head passes the periodic path of n wavelength, wherein, n and m are integers; Along periodic path, on a plurality of points, use magnetic head to read from disk; And use institute's number to read the characterization magnetic head.

Periodic movable signal has advantage: magnetic head can be in various radial positions with single channel (this channel definition for by the continuous operation of obtaining test data of W head, and do not stop to reorientate magnetic head) with different side-play amounts from the track reading of data.Compare, in prior art arrangement, need a plurality of passages, each and every one needs a passage by radially offset position each of magnetic head.The configuration of this embodiment has advantage: with the time of the side-play amount positioning head cost less of the disk of hope, and in fact spend more time and obtain test data.

If disk rotation m changes then this magnetic head passes the periodic path of n wavelength.This has advantage: after the m of disk changes, turn back to respect to the same position of magnetic disk surface and defer to identical path with respect to magnetic disk surface, periodic path this moment " sealing (close) " at magnetic head.This is illustrated in respect to the test that can obtain more covers by W head on the identical in fact point of magnetic disk surface and reads.In addition, must not stop to test reading to reorientate magnetic head.This causes temporal saving again in test processes.

In one embodiment, n=1 and m=1.This allows the wavelength of periodic path to meet the single complete rotation of disk expediently.

In the preferred embodiment of this method, carry out described reading on the same position in each periodic path relevant, and this method comprises described the read calculating mean value of the different revolution of process disk to each point on the disk with disk.Allow the more accurate test of generation to read to the calculating mean value that reads, wherein alleviated noise and/or caused the false other factors that reads from W head.This allows the W head of more accurate characterization (characterise) tested person.

In a preferred embodiment, the periodic path of indication comes down to sinuous path.

In a further preferred embodiment, the indicating positions of magnetic head is moving head on whole radial zones of track.For example, this allows to carry out (bathtub) BER test of losing efficacy completely in single passage.

In a preferred embodiment, this method comprises: use optical pickup to read the optical readable mark that rotates with disk, thereby and determine the position of rotation of disk; The position of rotation of determining with reference to described disk calculates the periodic path of indication.This allows accurately to coordinate between the rotation of the cycle of the periodic path of indication and disk.This allows the periodic path of indication accurate " finishing (close) ".

In a preferred further embodiment, this method comprises provides at least one error signal in the position of magnetic head to servo controller, and servo controller is configured to come according to the cycle movable signal of described at least one error signal and described indication the position of control head.Track has relative servo pulse, and this method comprises: use magnetic head to detect servo pulse; The detected servo pulse of demodulation is to determine the position error signal of magnetic head; Putting the position up-sampling position error signal of corresponding described periodicity movable signal with the orbit centre of hope; And determine that by a plurality of samples trend in the sample is to provide described at least one error signal.This position that allows control head is with comfort noise or drift, and it has influenced steady arm and has caused that the side-play amount of reality of magnetic head is different with the indication side-play amount of magnetic head.This has advantage: the bandwidth of sample is low relatively, allows more easily implementation controller function.In addition,, promptly locate the center of the track of servo null, sample from identical position with respect to the track radial position.Any nonlinear adverse effect with respect to the PES of magnetic head radial position on the track has been eliminated in this expression in large quantities.This provides advantage: before test, and must be for each magnetic head of each track characteristicization.Thereby this method can not comprise tests magnetic head to servo track characterization magnetic head.In addition, this embodiment provides advantage: in the test process, and before the indication magnetic head arrives each position, the essential continuous track centerline of searching again.Can eliminate drift in real time, the test duration of vast scale be spent in obtain on the test data rather than on track centerline, seek continually and positioning head again.Therefore reduce the time of test magnetic head cost, brought more efficient, test cheaply.

According to a sixth aspect of the invention, provide a kind of equipment that is used to test W head, this equipment comprises: the axle that is used to install magnetic disk media and spinning disk medium; Steady arm is used for locating W head in the radial position of described magnetic disk media; Controller, construct and be configured to the movable signal indication steady arm positioning head of periodic, make the radial position of magnetic head move along periodic path in theory, wherein, if disk rotation m changes then magnetic head passes the periodic path of n wavelength, wherein n and m are integers; And data obtainer, be used on a plurality of points, using magnetic head to read from disk along periodic path.

By example embodiments of the invention are described referring now to accompanying drawing, wherein:

Figure 1A illustrates the example of prior art QAM (quadrature amplitude modulation) servo pulse, and Figure 1B illustrates the example of the PES (position error signal) that the servo pulse from Figure 1A obtains;

Fig. 2 schematically shows the example of W head testing apparatus according to an embodiment of the invention;

Fig. 3 illustrates the example of the design of the servo null of servo track according to an embodiment of the invention;

Fig. 4 illustrates the example of spiral servo track according to an embodiment of the invention;

Fig. 5 is illustrated in the RRO in the servo track that reads Fig. 3 and the example of NRRO error;

Fig. 6 A illustrates the desirable sinusoidal curve that is suitable for by the testing apparatus of Fig. 2 is used and indicates head trajectory, and Fig. 6 B illustrates the example of the track among Fig. 6 A that has noise, and Fig. 6 C shows the example of the track among Fig. 6 A that has thermal drift.

With reference to figure 2, the example of testing apparatus 10 according to an embodiment of the invention is shown.Disk 11 is installed to axle 12.Disk 11 has the test tracks 101 of at least one circular concentric arrangement, and test tracks 101 has with the servo pulse of the arranged in form of the servo track 109 of sectorization (servo burst) 102 (the most clearly being illustrated in Fig. 3).

Will be installed to head suspension assembly 15 by the W head 14 of equipment 10 tests.Head suspension assembly 15 is installed to micro actuator 16.Micro actuator 16 is single shaft micro actuator 16 preferably.Yet in other embodiments, micro actuator 16 can be linearity or micro positioner turning axle, any appropriate format with any amount.Micro actuator 16 can operate to carry out careful position adjustment with respect to 11 pairs of magnetic heads of disk 14.

Location by 16 pairs of magnetic heads 14 of feedback control loop control micro actuator.The preferred low frequency servo controller that uses, this controller has at 1Hz to the bandwidth between the 10Hz.Preferably operate to reduce the test duration for example about 12000rpm (about 200 revolution per seconds) with high relatively rmp for testing apparatus 10.As will be described, testing apparatus 10 revolutions obtain a position error signal sample.This provides enough sample rate to support needed bandwidth.

Prime amplifier 17 amplifies magnetic head 14 detected data.Via passage 18, the data corresponding to the pulse 102 of private clothes that are detected are sent to detuner 19.As below describing in detail, detuner 19 can be operated usually to produce the PES 20 from servo pulse 102.PES 20 is fed back to servo controller 21.Detuner 19 receives the desirable radial deflection amount corresponding instruction input 19a with magnetic head.For example, this side-play amount can be the center line with respect to track 101.Servo controller 21 can be operated to micro actuator 16 is produced signal output 21a, so that detent 16 positioning heads 14.Usually arrange that servo controller 21 comes positioning head 14 so that PES 20 is reduced to 0.Can finish this kind operation of servo controller 21 by any suitable technology, for example techniques well known in the art no longer specify here.

Fig. 3 illustrates the test track/data track 101 of preferred servo pulse 102 (schematically showing) design of form that (not to scale (NTS)) has the servo track 109 of sectorization.On the part of whole test tracks 101, to sector n+3 servo pulse 102 is shown from sector n-3.Track 101 is circle and concentricity with disk 11.(should notice that circuit orbit has been expressed as linear axes to be illustrated more clearly in the characteristic of servo track in Fig. 3.)

In use, write and sense data from track 101 on disk 11, the servo track 109 of track 101 and sectorization is interleave (interleave) mutually.The servo pulse 102 of each servo sector provides servo null 108.For example shown in Figure 1, preferred servo pulse 102 is QAM (quadrature amplitude modulation) servo pulses, thereby provides each servo null 108 by a pair of relevant servo pulse 102.Yet, also can use the servo pulse 102 of other suitable type known in the art that servo null is provided.For clear, Fig. 3 does not illustrate the form of servo pulse 102 itself.Instead, the position of the servo null 108 that is provided by the various servo pulses 102 relevant with track 101 is provided Fig. 3.

In a preferred embodiment, the radial position 23 of servo null 108 changes linearly with the circumferential position of servo pulse 102.Fig. 3 illustrates the linear relationship or the track 24 of servo null 108.As will be readily understood, in the place of using the sector servo scheme, the radial position 23 of servo null 108 exists and limits track 24, but will have discrete location thus.Therefore Fig. 3 illustrates the track 24 of discrete servo null positions 23.Preferably servo null 108 is radially arranged equably.Also preferably with servo null 108 circumference separation equably.In example, if the typical amounts of hypothesis servo sector be 250 and servo sector take half track 101, then each sector be equivalent to track 101 circumference 0.2%

Can expect other radial positions of the servo null 108 except linearity and the relation between the circumferential position.In any case, preferred, the radial position of continuous servo null 108 and the change of circumferential position dullness.Preferably pre-determine the form of track 24, and system knows this form in advance.

Fig. 3 illustrates the current location for magnetic head 14, and for concentric read position 25, room 26 appears on the N of sector.When magnetic head 14 was crossed track 101 circular flights, magnetic head 14 detected each servo pulse 102 according to this.To measure relatively and the radial position of servo null 108 magnetic head 14, servo pulse 102 from the detected signal demodulation of servo pulse 102 so that the servo sample of each servo pulse 102 to be provided.

Use produces error signal so that any thermal drift is proofreaied and correct from the signal of servo pulse 102.In order to reduce the noise in this signal, the pulse that can read the either side of target, and if necessary then uses the known relationship of track 24 to carry out interpolation or on average to determine more accurate null position.As previously mentioned, nonlinearity erron and gain error reduce near null position.

Refer again to Fig. 3, if wish now with magnetic head 14 slight 0.5% to new radial position 27a of the track widths that promote, the step below then adopting.At first, the known relationship by using track 24 is calculated new target null position 28 to the desirable radial position 27a of magnetic head 14.In this example, target null position 28 is between sector N+2 and N+3.The sensor order magnetic head 14 that uses micro actuator 16 and inside thereof then is near target location 27a.Read servo null 108 by magnetic head 14.Can read in all servo null 108, or only read near these servo null 108 of target radial position 27a.Known relationship according to track 24 is used method of interpolation in detected null signals, to seek the null position 28 that magnetic head passes the reality of track 24.The difference of target null position 28 and detected null position is used to produce position error signal 20.

As will be understood, before moving head 14, calculate for the target null position 28 of the radial deflection amount of the hope of magnetic head 14 and produce this method formation position error signal 20 of the position error signal 20 relevant then with this target null position 28, and when magnetic head was in target location 27a, this position error signal 20 will be always 0.No matter select which target location 27a with respect to track 101, this is always correct.This technology can be used to pass the little slight promotion of track 101 or moving of a plurality of track 101.As long as track 24 radially extends to the identical degree with track 101, just can use this technology to come to radial position generation PES with respect to any hope of the magnetic head 14 of track 101.As long as track 24 extends so far, just can use radial position similarly above track 101.

In other embodiments, can select target position 27a make its with radial position on servo null 108 immediate any one be consistent.In this situation, the quantity by the servo null on the track 24 108 limits the resolving power in the location of magnetic head 14.

The whole radial zone of test tracks 101 is passed in preferred servo null 108 extensions at least.Servo null 108 can extend beyond the radial zone of track 101.In fact, extend its track 24 by servo null 108, servo track 109 can extend beyond the track 101 of test tracks shown in Figure 3 101 up to other radially adjoining.Like this, schematically show, single continuous servo track 109 can be write disk 11 with the form of spiral as Fig. 4.The part of this spiral servo track 109 effectively provides each

servo track

109a, 109b, 109c, 109d to concentric

circular data track

101a, 101b, 101c, the 101d (as shown in Figure 4 by

rail flanges

22a, 22b, 22c, 22d) of a plurality of vicinities on the disk 11.

Preferred use identical micro actuator 16 writing servo pulses 102, when in the test process of magnetic head 14, coming positioning head 14, use this micro actuator 16 by slight promotion.What this allowed servo pulse 102 writes and reads equity, thereby compensates for any out of true in the micro actuator 16 effectively.This is normally according to the standard method of reading servo track 109 in production test environment, wherein write a series of tracks 109 and as the part of initialize routine and its hundreds of or several thousand magnetic heads 14 are remained unchanged before re-treatment.

To obtain higher accuracy in the magnetic head 14 in order also testing thus, preferably dynamically to compensate repeatably error (writing the NRRO (not reproducible operation) that RRO (can rerun) or machinery are introduced) at positioning head 14.According to technology known in the art, can characterization RRO when the initialization of testing apparatus 10.Preferably dynamically compensate machine error.Preferably, based on reading the PES 20 that is independent of radial position, algorithm inserts each measurement in the sector on sector basis.Preferably, servo controller 21 is used for before PES 20 comes compensation for thermal drift, thereby arranging that at least 20 of this system's disk changes is used to accumulate enough RRO data to be ready to this system.Estimate that this is no more than 100 milliseconds (ms) with cost.This can parallelly with test operation carry out, if perhaps can accept this application expense selectively as independently the operation move.

With reference to figure 5, the track 24 of ideal null 31 and the actual path of detected servo null 30 are shown.For detected servo null 30, these points illustrate the RRO composition (for example being caused by the eccentricity in the axle) of error, and error bars illustrates the NRRO composition (for example being caused by mechanical shock) of error.In order to determine the RRO composition, detected sample 30 need average by a plurality of rotations of disk to resist the NRRO composition.Error between each sample 30 of characterization and the ideal null 31 also is kept at error in the dynamic RRO form, and dynamically the RRO form is used for determining the position of servo null 108.For each servo pulse 3 repeatably composition be constant, therefore when passing track 101 slight promotions, can use repeatably composition and not need to upgrade form.

Other that is envisioned that servo pulse 102 and track 101 arranged substituting as the above-mentioned specific embodiment of the spiral trajectory 24 with circular concentric data track 101 and linearity/servo null 108.For example, write circular, concentric data track 101 not necessarily.Can write data-track 101 with spiral or sinusoidal wave form, the track of servo null 108 can be concentric.Other form is possible.Under each situation, the track of servo null 108 extends through the radial extension of track 101.Here, the radial extension of track 101 represent with respect to track 101 rather than with respect to disk 11.This permission is sought a little on track 24, and at that point, when following track 101 on this position in the whole radial positions on track 101, magnetic head will pass track 24 and detect servo null 108.

And according to the zone of target disk 11, according to the fc-specific test FC of carrying out, anticipation track 24 can extend across a plurality of adjacent data-tracks 101, or a part of only crossing track 101.

In one example, the position of indication magnetic head 14 is with the path in surface description cycle of crossing disk 11.Though can use arbitrarily rational periodic path in theory, for simple preferred sinusoidal trajectory 27b.Fig. 6 A illustrates desirable sinusoidal head trajectory.Fig. 6 B illustrates the sinusoidal head trajectory with some current noise.Disk 11 has at least one track 101, and track 101 is circle and concentricity with disk 11.The center line of sinuous path 27b is preferably consistent with the center line of track 101.Thereby the whole radical length that preferred sinusoidal amplitude makes magnetic head 14 pass track 101 moves around.

Thereby integral body (integral) quantity of the whole wavelength of the wavelength of preferred sinuous path 27b is consistent accurately with whole revolutions of disk 11.Selectively, can use the Integer n wavelength consistent of wavelength with the integer m of whole revolutions of disk 11.To understand, after the revolution of crucial here some quantity at disk 11 (preferably only one change), magnetic head 14 returns follows relatively and identical path, disk 11 surfaces, thereby can repeat the following data of reading magnetic head 14.

Can anticipate, other periodic path except sinuous path, as long as these paths periodically be applied to magnetic head 14 and continuously moving heads 14 cross the part of the radical length of track 101 at least, and before the beginning next cycle, magnetic head 14 navigated to and gets back to the position that radially begins.

The specific consistance that reaches between whole revolutions of indicating head position 27b and disk 11 by high class precision is necessary.Accurate consistent for the rotation of obtaining sinusoidal wavelength and disk 11 can use optics timing technology.The example of this technology is disclosed among commonly assigned (commonly assigned) the U.S. Patent application Nos.60/695845 and 11/480582 that submits to respectively on July 5th, 2005 and on July 5th, 2006, its title is " method and apparatus that is used for clocking, is used for the writing servo track and is used to describe the time of servo track writer ", and its full content is incorporated this paper into as a reference.Briefly, by moving so that output signal to be provided of fluorescence detector detection and disk 11 synchronization-moving at least one mark, this output signal can be processed so that clock signal to be provided.By being fixed to the grating of disk 11, perhaps some part (for example other parts of motor drive shaft 12 or motor itself) with disk 11 synchronous rotations can provide a mark or a plurality of mark.

Use preferred sinusoidal head trajectory, the Zone Full that makes magnetic head 14 pass track 101 is measured test data.In the prior art, this is by the radial deflection amount to the relevant hope of magnetic head 14 indication and track 101, and on this side-play amount, measure and carry out through the repeatedly rotation of disk 11, to change this side-play amount then and repeat and handle, set up the profile of wishing up to the radial zone that passes track 101.In principle, by using the sinusoidal indicative curve head position of this example, only need once rotating of disk 11 to obtain essential data with the width that passes track 101.Yet, in practice, preferably use the repeatedly rotation of disk 101, thereby can carry out the reading of larger amt to resist noise.

In preferred version, the indicating positions of magnetic head 14 is sinusoidal curves, and when the position of magnetic head 14 is consistent with track centerline (, when sinusoidal curve or other cyclical signal are in the pulse of multiple of π radian), PES 20 is sampled.These samples are collected in repeatedly rotation through disk 11, and these samples are carried out calculating mean value or low-pass filter.The numerical value that is obtained provides the low-down bandwidth measurement of the error that is caused by thermal drift (or mainly by thermal drift).Fig. 6 C illustrates because thermal drift influences, the indication sinusoidal position of magnetic head 14 example how deorbit is drifted about (form with exaggeration illustrates).Under no drift situation, these numerical value should be 0.

This technology has the advantage of easy enforcement.And, with the position consistency of the servo null 108 of servo track 109, on track centerline, obtain PES sample 20, thereby avoided the change of the gain of possible effect of nonlinear and PES signal 20 to a great extent.Therefore must be to of the accurate measurement of track 101 characterization magnetic heads 14 with the thermal drift of obtaining magnetic head 14.Can detect and eliminate drift in real time, make to spend more the test duration of vast scale and obtain test data rather than come track 101 calibration magnetic heads 14.Thereby reduce the time of test magnetic head 14 costs, and bring more effective, more save the test of cost.

By the example that concrete reference is illustrated embodiments of the invention have been described.Yet, should be appreciated that, within the scope of the invention, can change and revise described example.

For example, with reference on the W head of disk, carrying out BER inefficacy (bathtub) test the example of the preferred embodiments of the present invention has been described.Yet, the person skilled in the art will easily understand, can carry out the head test of other type according to principle of the present invention.Similarly, according to principle of the present invention, can test the magnetic head of other type of the medium that is used to read other type.

Claims

1. method, the radial position that this method is wished with respect to the data in magnetic disk track W head produces position error signal, wherein, this track has a plurality of servo pulses, a plurality of servo pulses are used to limit a plurality of servo null of this track, these a plurality of servo null are located so that in the different radial position above four with respect to track and all have servo null, servo null limits desired trajectory, this desired trajectory and this track have known position relation, the radial zone that this track passes this track extends, and this method comprises:

(a), determine that correspondence and described magnetic head are with respect to the target null position desirable radial position of track, on the null loci according to described known position relation;

(b) use magnetic head to detect the position of at least one servo null;

(c) determine the site error of magnetic head from described at least one servo null positions that is detected with respect to target null position;

(d) produce position error signal according to described site error.

2. method according to claim 1, wherein, step (b) comprises that detection is at least diametrically near the position of the servo null of magnetic head.

3. method according to claim 1 and 2, wherein, step (b) comprises the position of detecting a plurality of servo null, and step (c) is included in carries out interpolation to seek described site error between described a plurality of null position, calculate described interpolation according to described known position relation.

4. according to each described method of claim 1 to 3, wherein, the mean value that calculates site error by the continuous rotation of disk is to produce position error signal.

5. according to each described method of claim 1 to 4, wherein, the radial position of the hope of selection magnetic head is to be consistent with servo null.

6. according to each described method of claim 1 to 5, wherein, track and disk are concentricity, and a plurality of servo null have different radial positions along the circle spacing and on each circumferential position.

7. according to each described method of claim 1 to 6, wherein, servo null is at interval even on disk.

8. according to each described method of claim 1 to 7, wherein, is extending in the radial direction continuously along centering on the single of track the position of servo null.

9. according to each described method of claim 1 to 8, wherein, the radial position of servo null is linear the change along with circumferential position.

10. according to each described method of claim 1 to 9, wherein, the position of servo null limits at least one spiral at least a portion of the servo null on the disk.

11. method according to claim 10, wherein, spiral pitch is the width of track.

12. according to each described method of claim 1 to 5, wherein, servo null loci and disk are concentricity.

13. method according to claim 12, wherein, track defines sine wave.

14. method according to claim 13, wherein, sine wave has the wavelength of the orbit circumference of equaling.

15. according to each described method of claim 1 to 14, wherein, disk initially is empty servo pulse, described method comprises, in step (a) before, carries out the step that disk is write described servo pulse.

16. a method of testing W head, this method comprises:

Magnetic head is indicated to respect to the desirable position of the track of disk;

According to each described method of claim 1 to 15, to the physical location and the generation of the difference between the desirable position position error signal of magnetic head;

Use the closed loop controller that is provided with to come the position of control head so that actual the reducing to of position error signal is essentially 0; And

The test magnetic head.

17. one kind is used W head that disk is write the method for data-track in magnetic head dielectric tests equipment, this disk has a plurality of servo pulses, and this servo pulse defines more than four servo null, and this method comprises:

Write described data-track and make it consistent with described servo null more than four, thereby servo null limits the desired trajectory with known location relation relevant with track, the radial zone that this track is crossed track extends.

18. method according to claim 17, wherein, track and disk are concentricity, and a plurality of servo null have different radial positions along the circle spacing and on each circumferential position.

19. according to claim 17 or 18 described methods, wherein, is extending in the radial direction continuously along centering on the single of track the position of servo null.

20. according to each described method of claim 17 to 19, wherein, the radial position of servo null is linear the change along with circumferential position.

21. according to each described method of claim 17 to 20, wherein, the position of servo null limits at least one spiral at least a portion of the servo null on the disk.

22. method according to claim 17, wherein, servo null loci and disk are concentricity.

23. method according to claim 22, wherein, track defines sine wave.

24. according to each described method of claim 17 to 23, wherein, disk initially is empty servo pulse, described method comprises, before writing the step of data-track, carries out the step that disk is write described servo pulse.

25. an equipment that is used to test W head, this equipment comprises:

Disk, it has track, wherein, this track has a plurality of servo pulses, these a plurality of servo pulses limit a plurality of servo null of this track, this servo null be located so that with respect to this track more than four different radial positions on have servo null, servo null limits desired trajectory, this desired trajectory and this track have known position relation, and the radial zone that this track is crossed this track extends;

Steady arm is used for the described magnetic head in location in the radial position on the disk;

Processor is provided for:

(a) receive the desirable radially head position relative with track;

(b) according to described known position relation,, determine the target null position on the null loci corresponding to of the desirable radial position of described magnetic head with respect to track;

(c) use magnetic head to detect the position of at least one servo null;

(d) determine site error from least one detected servo null positions with respect to the magnetic head of target null position; And

(e) produce position error signal according to site error; And

Feedback controller is provided for receiving described position error signal as the feedback input, and makes described steady arm locate described magnetic head, thereby described position error signal is reduced to 0.

26. the method for a test W head that is suitable for using in disk drive, this method comprises:

Corresponding to the track on the disk, positioning head in the radial position on the spinning disk medium;

The position of periodic movable signal indication magnetic head makes the radial position of magnetic head along periodic path movement, if disk rotation m changes then this magnetic head passes the periodic path of n wavelength, wherein, n and m are integers;

Along periodic path, on a plurality of points, use magnetic head to read from disk; And

Use institute's number to read the characterization magnetic head.

27. method according to claim 26, wherein, n=1 and m=1.

28. according to claim 26 or 27 described methods, wherein, carry out described reading on the same position in each periodic path relevant, and this method comprises described read average of the different rotation of process disk to each point on the disk with disk.

29. according to each described method of claim 26 to 28, wherein, the periodic path of indication comes down to sinuous path.

30. according to each described method of claim 26 to 29, wherein, the indicating positions of magnetic head is moving head on whole radial zones of track.

31. according to each described method of claim 26 to 30, wherein, this method comprises:

Use optical pickup to read the optical readable mark that rotates with disk, thereby and determine the position of rotation of disk;

The position of rotation of determining with reference to described disk calculates the periodic path of indication.

32. according to each described method of claim 26 to 31, wherein, this method comprises provides at least one error signal in the position of magnetic head to servo controller, and servo controller is configured to come according to the cycle movable signal of described at least one error signal and described indication the position of control head.

33. method according to claim 32, wherein, track has relative servo pulse, and this method comprises:

Use magnetic head to detect servo pulse;

The detected servo pulse of demodulation is to determine the position error signal of magnetic head;

Putting the position up-sampling position error signal of corresponding described periodicity movable signal with the orbit centre of hope; And

Determine that by a plurality of samples trend in the sample is to provide described at least one error signal.

34. an equipment that is used to test W head, this equipment comprises:

Axle is used to install magnetic disk media and spinning disk medium;

Steady arm is used for locating W head in the radial position on the described magnetic disk media;

The movable signal indication steady arm positioning head of periodic is constructed and be configured to controller, makes the radial position of magnetic head move along periodic path, and wherein, if disk rotation m changes then magnetic head passes the periodic path of n wavelength, wherein n and m are integers; And

Data obtainer is used for using magnetic head to read from disk on a plurality of points along periodic path.

35. equipment according to claim 34, wherein, n=1 and m=1.

36. according to claim 34 or 35 described equipment, wherein, structure and configuration data getter are to read on the identical position in each periodic path relevant with disk.

37. according to each described equipment of claim 34 to 36, wherein, the periodic path of indication comes down to sinuous path.

38. according to each described equipment of claim 34 to 37, wherein, this equipment comprises optical pickup, optical pickup is used to read the optical readable mark that rotates with disk, this mark is set to allow to determine the position of rotation of magnetic disk media.

39. according to each described equipment of claim 34 to 38, wherein, described controller is a servo controller, servo controller is set for the position of coming control head according to the periodicity movable signal of at least one error signal and described indication, wherein, provide at least one error signal in the position of magnetic head to described servo controller.

40. according to the described equipment of claim 39, wherein, track has relative servo pulse, this equipment comprises:

Detuner is used for demodulation by the position error signal of the detected servo pulse of magnetic head with definite magnetic head; And

Sampler is used for putting collection position error signal on the position of corresponding described periodicity movable signal with the orbit centre of hope, and determines that by a plurality of samples trend in the sample is to provide described at least one error signal.