Abstract: The invention combines the benefits of sectored servo data with the benefits of time-based servo data. Recording media such as magnetic tape, magnetic disks, optical tape and optical disks can store servo data in a time-based sectored servo format.

Abstract: A method and apparatus is disclosed for writing product servo sectors to a disk of a disk drive to define a plurality of data tracks. The disk drive comprises the disk and a head actuated over the disk. The disk comprises a plurality of spiral tracks which are read using the head to synchronize a write clock and to generate a position error signal (PES) according to a PES algorithm used to maintain the head along a first servo track while writing product servo sectors along the first servo track. The PES algorithm is adjusted to seek the head to a second servo track, and the head is used to write product servo sectors along the second servo track.

Abstract: A piezo actuator is provided between a suspension spring and a head carriage. When a predetermined track of a magnetic disk is accessed by positioning a magnetic head in the predetermined track, the piezo actuator maintains the magnetic head in an ON track state by dynamically moving a light weight head cartridge according to a servo information or dynamically moving a head assembly in the head cartridge according the servo information.

Abstract: The present invention is directed to method and apparatus for determining a transducer's reference position in a disk drive having a disk surface with spiral servo information written thereon. The transducer comprises a read head for reading spiral servo information and a read signal envelope is generated when the read head reads the spiral servo information. An integration is performed over a first integration window, wherein the first integration window includes a read signal envelope. A reference position is determined for the read head using a second integration window (virtual integration window) that is included within, and smaller than, the first integration window. In one embodiment, the integration may be performed on a frame-by-frame basis. A determination may be made of the frame in the first integration window that includes a maximum sync amplitude. The second integration window may be centered using the frame that includes the maximum sync amplitude.

Abstract: A magnetic recording system includes a patterned medium comprised of land areas and trough areas, a write element which writes the data to the patterned medium, and a read element which reads the data from the patterned medium and servo information from the troughs. The land areas store data and the trough areas inhibit storage of data. The read element is wider than the write element.

Abstract: A method of manufacturing a disk drive by demodulating product servo sectors and spiral tracks written on a disk of the disk drive is disclosed. An external spiral servo writer writes a plurality of spiral tracks that spiral from an outer diameter to an inner diameter of the disk. Each spiral track comprises a high frequency signal interrupted at a predetermined interval by a sync mark. The spiral tracks are used to write product servo sectors to the disk during a fill operation. Common circuitry, such as burst demodulation circuitry, is used to demodulate the high frequency signal in the spiral tracks during the fill operation as well as demodulate the product servo sectors.

Abstract: A method and apparatus is disclosed for adjusting the track density over the disk radius by changing the slope of spiral tracks used to servo write a disk drive. A plurality of spiral tracks are written to the disk wherein each spiral track comprises a high frequency signal interrupted at a predetermined interval by a sync mark. A slope of the spiral tracks over a first radial segment of the disk is substantially steeper than the slope of the spiral tracks over a second radial segment of the disk. The head internal to the disk drive is used to read the spiral tracks in order to write product servo sectors to the disk to define a plurality of data tracks. The steeper slope of the spiral tracks over the first radial segment causes a track density of the data tracks to be lower over the first radial segment compared to the track density of the data tracks over the second radial segment.

Abstract: A magnetic recording medium has a substrate, and a servo signal recording magnetic layer whose magnetization is oriented in a direction perpendicular to a surface thereof, a non-magnetic layer and a data recording magnetic layer, which are stacked on the substrate in the order mentioned. The servo signal recording magnetic layer has a coercivity higher than that of the data recording magnetic layer. The servo signal recording magnetic layer has servo tracks formed with a track pitch Tps, the servo tracks adjacent to each other in a track width direction being magnetized to opposite directions perpendicular to the film surface.

Abstract: In a disk drive, since high-frequency repeatable runout (RRO) components own low correlative relationships between adjoining tracks, a servo control system of a magnetic head is followed to the high-frequency RRO components, and thus, in the worst case, there is a possibility that data which have been previously recorded on these tracks are destroyed. To avoid this problem, both a tracking type repetitive control unit which is followed to low-frequency RRO components, and a rejection type repetitive control unit which cancels the high-frequency RRO components are provided in a following control loop in order that the following control system is not unnecessarily followed to the high-frequency RRO.

Abstract: A method and apparatus for automatically determining an embedded runout correction threshold for a disk drive are disclosed. In prior systems, embedded runout correction thresholds were set for all disk drives in a production run. The present invention provides a technique for automatically determining an embedded runout correction threshold on a drive-by-drive basis, instead of a production run of drives basis.

Abstract: A servo system is disclosed which is applied to a disk drive for detecting characteristic frequency components of a position error between a position of the head and the target position, and calculating a control correction value for correcting a control value. The servo system estimates the frequency components of target value variation from the characteristic frequency components of the position error, thereby modifying the characteristic frequency components to follow the target value variation. Thus, the servo system calculates the control correction value for suppressing the target value variation, and executes head positioning control, using a value obtained by adding the control value to the control correction value.

Abstract: A method of reducing rotational vibration effects in a disk drive by sensing vibration in a sensor and generating corresponding sensor data; deriving a statistical sensor (SS) value based on the sensor data; deriving a statistical position error signal (SPES) value from servo sectors read by the head; comparing the SS value to a SS-threshold value; comparing SPES value to a SPES-threshold value; and generating a feed-forward command effort signal for reducing rotational vibration effects if the SS value exceeds the SS-threshold value and if SPES value exceeds the SPES-threshold value.

Abstract: Method and apparatus for operating a motor. During a commutation state current is applied to a motor while field effect transistors (FETs) are held in an enable or disable state to effect current in phases of the motor. The phases have a high FET and a low FET. Control circuitry is employed to detect back electromotive force and zero crossing (Zc) signals that indicate transition timing for the commutation states. At a transition state the current is decreased in accordance with a noninstaneous decay function and applying a pulse width modulated signal to a switching element. Alternatively, the current is decreased by enabling either all low side FETs or all high side FETs to allow the current to decay. The next commutation state is applied after the current has been reduced, avoiding negative current to be source from ground and reducing current spikes in the motor.

Abstract: A scanning device for scanning data-carrying disks. The disks include a magnetisable layer to and from which data is written and read using a magnetic transducer, such as a Giant Magneto-Resistive (GMR) transducer. Positioning of the transducer over a data track is achieved by optical tracking using a land/groove structure, and positioning of the transducer with respect to the optical tracking system by means of a reference beam transmitted through the disk.

Abstract: A method of handling resonance effects on disc drives includes the steps of monitoring a position error signal (PES) for an actuator arm of a disc drive, generating a feedforward compensation signal from the PES using a bandpass filter, and applying the compensation signal to a servo control signal. The bandpass filter has a center frequency set to a known resonance frequency. A disc drive includes an actuator assembly including an arm for carrying a head in a transducing relation with respect to a disc in response to a control signal, and a controller that monitors a PES for the arm and generates the control signal. The controller includes a servo controller that generates a servo control signal from the PES, and a feedforward compensation element which bandpass filters the PES to generate a compensation signal which is combined with the servo control signal to generate the control signal.

Abstract: This invention discloses a method for controlling the position of flexible portions of a mechanical structure by attaching one or more Momentum Transfer Actuators on the flexible portions of the mechanical structure near the points whose position is to be controlled, sensing the position of the flexible portions of the mechanical structure, and, employing one or more feedback loops, to control the Momentum Transfer Actuators to cause the flexible ends of the mechanical structure to follow a desired position as a function of time. The invention also addresses the use of combined actuating and sensing devices that incorporate both a Momentum Transfer Actuator and an inertial sensor to provide acceleration, velocity, and position information to the feedback control system.

Abstract: A disc drive with an information portion previously written on a rotatable disc surface, a servo write clock generator phase lock loop circuit controlling timing for writing a reference mark to the rotatable disc surface in substantial time alignment and phase and frequency coherent with the information portion previously written to the rotatable disc surface, a servo write clock generator phase lock loop circuit controlling timing for writing the reference mark, a pulse detector circuit for creating logic level signals from the reference mark, a pattern generator for generating reference mark write signals from the logic level signals, a memory buffer for storing radial position correction tables and values for writing the reference mark, and a self-servo control and sequencing circuit synchronizing timing signals for writing the reference mark to rotatable disc surface of disc drive.

Abstract: A method of recovering data from a data sector through adaptive fly height to improve reliability of a disc drive is disclosed. Encountering a data error in a data sector initializes an error recovery routine that increases a fly height of the read/write head for asperity encounters, or decreases the fly height of the read/write head for low amplitude read signal encounters. In the case of asperity encounters, when the increased fly height fails data recovery, the read/write head is positioned off track, then lowered to burnish the asperity and the data sector is re-read.

Abstract: A method and apparatus for simultaneously measuring and calculating servo-related data is disclosed. The method involves measuring the servo related data for a first track of a disc drive and then measuring servo related data for a second track. The method further involves calculating servo related values for the first track, based on the measured servo related data for the first track, while servo related data is being measured for the second track. This method is applicable for processes such as zero acceleration path determination in disc drives, whereby position errors are measured for the first track and then position errors are measured for a second track while simultaneously calculating the zero acceleration path for the first track based on the position errors previously measured.

Abstract: A reader-to-writer offset for a head positioned over a track on a disc in a disc drive having a plurality of tracks is generated by using two iterations. A first iteration is used to determine a fine-tuning range that is used for a second iteration. The first iteration uses coarse steps of the reader across the track pitch to roughly determine OTC boundaries (which are used as the fine-tuning range). The fine-tuning range is determined by locating the point before the first valid reading (e.g., a VGA reading or BER reading with a rate that is less than the BER threshold) and by locating the point after the last valid reading. The second iteration uses fine steps of the reader across the track pitch to determine the actual OTC boundaries. The OTC boundaries are the first valid reading and the last valid reading that are made using the fine steps.

Abstract: A method and apparatus for controlling the position of a computer hard disk drive transducer head are provided. According to the invention, an initial value compensation scheme is applied to a signal derived from available states of the transducer head when the control mode of the disk drive switches from a track seek mode to a settling mode. In particular, at least portions of a the compensation signal are provided to both a coarse actuator and a microactuator associated with the transducer head. According to one embodiment of the present invention, high frequency components of the compensation signal are generally provided to the microactuator, while low frequency components of the compensation signal are generally provided to the coarse actuator. The method and apparatus of the present invention provide a computer hard disk drive having improved performance due to reduced settling times and improved audible characteristics.

Abstract: A magnetic recording medium has a substrate, and a servo signal recording magnetic layer whose magnetization is oriented in a direction perpendicular to a surface thereof, a non-magnetic layer and a data recording magnetic layer, which are stacked on the substrate in the order mentioned. The servo signal recording magnetic layer has a coercivity higher than that of the data recording magnetic layer. The servo signal recording magnetic layer has servo tracks formed with a track pitch Tps, the servo tracks adjacent to each other in a track width direction being magnetized to opposite directions perpendicular to the film surface.

Abstract: The present invention proposes a new servo track writing technique called Extended Copying with Head Offset (“ECHO”). The read and write elements of the read/write head are offset from each other. A servo writer writes a guide pattern on the magnetic media disc. ZAP correction factors are added to the guide pattern. The head disc assembly is then connected to an electrical control system for self-propagating servo writing. The actuator arm is displaced until the read head is aligned over the guide pattern. A new servo track is written by the write element. ZAP correction factors are added to the newly written servo track. The actuator arm is displaced until the read element is aligned with the newly written servo track. A new servo track is written. ZAP correction factors are added to the newly written servo track. The process is repeated until a desired number of servo tracks are written.

Abstract: In the magnetic disk unit comprising suspensions in each of which an IC is mounted on a load beam, a magnetic head displacement caused by the warp of the load beam occurring due to heat generated from the IC is compensated, whereby the shortening of an access speed and high reliability of reading/writing are realized. The thermal displacement of the magnetic head is compensated by operating micro actuators on the load beam in accordance with the temperature rise of the IC which is measured by a temperature sensor. Namely, by driving the micro actuators so that the magnetic head may move in a direction reverse to the direction of the magnetic head movement caused by the thermal displacement, the thermal displacement of the magnetic head is made to be substantially zero.

Abstract: A piezo actuator is provided between a suspension spring and a head carriage. When a predetermined track of a magnetic disk is accessed by positioning a magnetic head in the predetermined track, the piezo actuator maintains the magnetic head in an ON track state by dynamically moving a light weight head cartridge according to a servo information or dynamically moving a head assembly in the head cartridge according the servo information.

Abstract: A disk drive is disclosed comprising a head, and an actuator, responsive to an adjusted control effort signal, for actuating the head radially over a disk. An adaptive feed-forward signal is generated in response to a vibration affecting the disk drive and combined with a nominal control effort signal to generate the adjusted control effort signal. During a normal read operation the feed-forward signal is substantially removed from the adjusted control effort signal, and during a retry read operation the feed-forward signal is included in the adjusted control effort signal.

Abstract: A servo controller for correcting a read position of a head when reading data recorded on a recording medium. In accordance with the amplitude ratio of data signals read from each segment of a servo section defined on a recording medium, the servo controller generates an AGC signal corresponding to the next segment before reading the next segment. The data signal read from a phase detection segment of the servo section is amplified to an amplitude greater than the predetermined determination range. The amplified data signal is converted to a two-value digital signal in accordance with the determination range. The phase used during servo control is calculated in accordance with the digital signal.

Abstract: A system and method for controlling the position of a digital data storage device slider through the use of an electro-thermal micromechanical actuator is disclosed. A movable member is etched into a face of a slider opposite the air-bearing surface of the slider. The movable member is substantially freestanding in relation to the slider, having only a single end connected to the slider. An electrically actuated heater element with two parallel current paths is disposed on the movable member. One of the current paths is substantially narrower than the other current path. When a current is passed through the heater element, the narrower current path heats up more quickly than the wider current path. By varying the current passed through the heater element in a selected manner, a distortion of the movable member is harnessed and used to create a relative motion in the slider body, allowing the slider to be quickly and exactly located over the centerline of a track of a storage device.

Abstract: A magnetic disk unit writes, on a magnetic disk, a burst position error data which is used for correcting a positional error of a burst pattern which is used for correcting an error within one track, next to the burst pattern. A write head is controlled a position so as to satisfy a relationship M=N when (N−1)K <WHD<NK, where WHD denotes a core width of a write head, K denotes a pitch of burst boundaries of the burst pattern, and M denotes a number of regions of the burst position error data which need to be provided after the burst pattern. The burst position error data is written on the magnetic disk by the write head the position of which is controlled in this manner.

Abstract: A head gimbal assembly (10) for a disk drive (1), having a load beam (28), a flexure (30), a portion of the flexure (30) being attached to the load beam (28), a slider (20) which includes a read/write head (22), and a collocated microactuator (24) which connects between the flexure (30) and the slider (20). The collocated microactuator (24) is a shear mode piezoelectric motor (25) for providing pure or nearly pure lateral movement to the slider (20), thus providing secondary actuation for the head gimbal assembly (10).

Abstract: The present invention provides a system, method and data format wherein a redundant sync byte or group of sync bytes is provided in a data sector at a distance sufficient to isolate the redundant sync byte from the primary sync byte in the event of multiple byte defects. In a first embodiment, a redundant sync byte, or group of sync bytes, is provided in the AGC field preceding the primary sync region. Upon failure to detect the primary sync byte, an attempt is made on a subsequent revolution to read the secondary sync byte, either by holding the AGC gain prior to reaching the data block, or initiating an “early read” just prior to reaching the data block. In a second embodiment of the invention, the redundant sync byte is provided within the data field subsequent to the primary sync region. On failing to detect the primary sync byte, the secondary sync byte can be read immediately or can be postponed until a subsequent revolution.

Abstract: Servo circuitry is disclosed that is configured to operate with a magnetic disk drive system. The servo circuitry is comprised of a first servo detector system, a second servo detector system, and a comparator. The first servo detector system and the second servo detector system each receive samples, taken from a read signal, that include servo data. The first servo detector system compares the samples to a plurality of servo codes to generate a first selected code. The second servo detector system compares a first shifted version of the samples to the plurality of servo codes to generate a second selected code. The comparator receives the selected codes and selects one of the selected codes. The selected code represents the servo data. The servo circuitry could also include a third servo detector system that operates on a second shifted version of the samples.

Abstract: A hard disk drive system (10) includes a rotating magnetic disk (16), and a support arm (22) which is supported for movement relative to the disk under control of a voice coil motor (21). a microactuator (26) supports a read/write head (27) on the support arm for movement relative thereto a control arrangement (13) controls the voice coil motor and the microactuator in response to position information (31), which is read by the read/write head from the disk and which indicates the position of the read/write head relative to the disk. The system is free of a sensor for detecting the actual position of the support arm relative to the read/write head or the disk.

Abstract: This invention discloses a method for controlling the position of flexible portions of a mechanical structure by attaching one or more Momentum Transfer Actuators on the flexible portions of the mechanical structure near the points whose position is to be controlled, sensing the position of the flexible portions of the mechanical structure, and, employing one or more feedback loops, to control the Momentum Transfer Actuators to cause the flexible ends of the mechanical structure to follow a desired position as a function of time. The invention also addresses the use of combined actuating and sensing devices that incorporate both a Momentum Transfer Actuator and an inertial sensor to provide acceleration, velocity, and position information to the feedback control system.

Abstract: A method of correcting track misregistration in a servo system for a disc drive including one or more discs includes positioning a head over a track located on a disc and maintaining the head centered over the track. The process for maintaining the head centered may include measuring the radial position of the head relative to the disc and determining correction factors for a zero acceleration path. Correction factors are determined by modeling an actuator transfer function to produce an estimated position signal. Subsequently, an estimated disturbance signal is determined by subtracting the measured position and the estimated position signal and filtering it with an adaptation filter. Thereafter, the estimated disturbance signal is subtracted from the measured radial position to produce a modified position measurement signal. The head is repositioned in accordance with the modified position measurement signal.

Abstract: A disc drive includes a base and a disc rotatably attached to the base. The disc drive also includes an actuator assembly rotatably attached to said base and a device for moving the actuator assembly. The disc drive includes servo circuitry and a controller for controlling movement of the actuator and head switches during track seek operations. The disc drive determines the average seek time for each head and also measures the amount of time for a head switch from the transducer head having the shortest average seek time to all the other transducing heads in the disc drive. When a seek is performed, the controller in the disc drive determines if the shortest average seek time plus the seek time from the transducing head to the transducing head on the surface containing the target track and sector is less than the average seek time of the head on the surface having the target track and sector.

Abstract: A servo system is disclosed which is applied to a disk drive for detecting characteristic frequency components of a position error between a position of the head and the target position, and calculating a control correction value for correcting a control value. The servo system estimates the frequency components of target value variation from the characteristic frequency components of the position error, thereby modifying the characteristic frequency components to follow the target value variation. Thus, the servo system calculates the control correction value for suppressing the target value variation, and executes head positioning control, using a value obtained by adding the control value to the control correction value.

Abstract: Apparatus using information about the extent of errors in sensed data for performing as a control function at least one of adjusting the position of a magnetic head to improve alignment relative to a track and selecting from two or more data signals a data signal having the least amount of errors is shown. The apparatus uses information about the extent of errors to perform a control function for reproducing the data stored in predetermined storage locations in a storage media. The apparatus positions a transducer for sensing from predetermined storage locations stored data containing at least one constraint. The transducer generates a first signal representative of the data containing at least one constraint stored in the sensed data and any errors introduced into the sensed data during the sensing.

Abstract: A disc drive with an information portion previously written on a rotatable disc surface, a servo write clock generator phase lock loop circuit controlling timing for writing a reference mark to the rotatable disc surface in substantial time alignment and phase and frequency coherent with the information portion previously written to the rotatable disc surface, a servo write clock generator phase lock loop circuit controlling timing for writing the reference mark, a pulse detector circuit for creating logic level signals from the reference mark, a pattern generator for generating reference mark write signals from the logic level signals, a memory buffer for storing radial position correction tables and values for writing the reference mark, and a self-servo control and sequencing circuit synchronizing timing signals for writing the reference mark to rotatable disc surface of disc drive.

Abstract: A method and apparatus for using control apparatuses and read/write apparatuses within a disc drive to create a microtrack that is used to probe the magnetic sensitivity of each portion of a magnetic stripe of a magneto-resistive read/write head in the disc drive. The method can be executed by first selecting a target track and then recording a test signal along the target track. Next, the target track is trimmed to create a microtrack, the microtrack having a microtrack width less than the stripe width, the microtrack having a first circumferential edge and a second circumferential edge. Subsequently, the magneto-resistive stripe is positioned at various radial locales traversing the microtrack, and at each locale the magneto-resistive stripe is used to read the test signal recorded on the microtrack, thereby producing a detected signal at each of the various locales. Finally, a signal-strength profile is determined.

Abstract: A method of handling resonance effects on disc drives includes the steps of monitoring a position error signal (PES) for an actuator arm of a disc drive, generating a feedforward compensation signal from the PES using a bandpass filter, and applying the compensation signal to a servo control signal. The bandpass filter has a center frequency set to a known resonance frequency. A disc drive includes an actuator assembly including an arm for carrying a head in a transducing relation with respect to a disc in response to a control signal, and a controller that monitors a PES for the arm and generates the control signal. The controller includes a servo controller that generates a servo control signal from the PES, and a feedforward compensation element which bandpass filters the PES to generate a compensation signal which is combined with the servo control signal to generate the control signal.

Abstract: A method and apparatus for simultaneously measuring and calculating servo-related data is disclosed. The method involves measuring the servo related data for a first track of a disc drive and then measuring servo related data for a second track. The method further involves calculating servo related values for the first track, based on the measured servo related data for the first track, while servo related data is being measured for the second track. This method is applicable for processes such as zero acceleration path determination in disc drives, whereby position errors are measured for the first track and then position errors are measured for a second track while simultaneously calculating the zero acceleration path for the first track based on the position errors previously measured.

Abstract: A method and apparatus for controlling the position of a computer hard disk drive transducer head are provided. According to the invention, an initial value compensation scheme is applied to a signal derived from available states of the transducer head when the control mode of the disk drive switches from a track seek mode to a settling mode. In particular, at least portions of a the compensation signal are provided to both a coarse actuator and a microactuator associated with the transducer head. According to one embodiment of the present invention, high frequency components of the compensation signal are generally provided to the microactuator, while low frequency components of the compensation signal are generally provided to the coarse actuator. The method and apparatus of the present invention provide a computer hard disk drive having improved performance due to reduced settling times and improved audible characteristics.

Abstract: A disc drive device includes a base and a disc rotatably attached to the base. The disc drive also includes an actuator assembly rotatably attached to said base and a device for moving the actuator assembly. The actuator assembly includes an actuator arm and a transducer head in a transducing relationship with respect to the disc. The transducer is attached to the actuator arm. A method of screening disc drives for harmonic resonant frequencies includes sampling the position error signal at a track location in the disc drive, and determining the velocity of the position error signal from the sample of the position error signal. The velocity of the position error signal sample is divided by the position error signal to produce a quotient. The quotient is compared to a selected quotient threshold value to determine the type of a harmonic in the disc drive.

Abstract: A data recording and/or reproducing apparatus which scans a head over a disc on which a servo pattern for moving the head to a predetermined position is recorded in an arc forming a part of a concentric circle. The apparatus comprises a track No. detector and fine signal detector, for detection of the servo pattern, a circumferential position detector to detect a circumferential position on the disc, an offset calculator to calculate an offset of a current position on the disc from the detected circumferential position, and a positional difference calculator. The calculated offset of the current position is added to the positioning signal to control the head scanning orbit on the disc to be spiral.

Abstract: The present invention provides methods and apparatus for locating target positions within an encoded data stream, where the encoded data stream incorporates special, reserved codewords to represent host data structure information, such as file marks and record boundaries. The encoded data stream can also only be read or decoded in the forwards direction. Incorporation of the special codewords obviates an index associated with the encoded data to support navigation within the encoded data stream. The methods and apparatus locate target positions by decoding the data until the target position is encountered, and provide mechanisms to enable location of target positions that are specified as being backwards, relative to a current position in the encoded data stream.

Abstract: In the sector number counting method of the HDD using a disk as the recording medium having a plurality of servo sectors which are divided into several servo sectors groups, so that the first sector number information of each of the divided sectors groups is recorded on an index region, the inventive method for counting the sector number according to the present invention comprises the steps of checking whether the index bit recorded on the index region is detected every time when a servo interrupt occurs, and counting and saving the sector number according to a count value of an index timer on the basis of the first sector number of the servo sectors group corresponding to the index bit after the index timer is started when the index bit is detected.

Abstract: The present invention provides an apparatus and method of partitioning a recording medium data track into two longitudinal regions and erasing any preexisting signal on each region with a DC bias signal of polarity opposite to that of the other region. Magnetic transitions subsequently recorded over the two track regions will be shifted differently depending on the relationship of the polarity of the signal being encoded to that of the DC bias erase signal applied to each region. The complementary lead/lag errors from the two track regions produce a combined read head waveform in which the timing errors are substantially eliminated, thereby reducing system bit error rates and allowing increased data density on the medium. An apparatus and method of controlling the lateral position of the various heads are also disclosed.