JPS59175070A - Data recording apparatus and method - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

BACKGROUND OF THE INVENTION This patent application is filed on September 27, 1982 and is filed under now abandoned United States Patent No. 06/42.
This is a partial continuation of 4,914. This invention relates to rotationally rigid disk data storage devices of the floating head or windieser type. More particularly, the present invention relates to a greatly improved non-removable media, high storage capacity rotationally rigid disk data storage device and method. Inventor Assignee has pioneered the development of low cost, high performance rotationally rigid disk data storage devices in the non-removable 8-inch media field. Part J: The eel device is 2
There are two currently co-pending United States patent applications entitled ``Improved Data 1-Lance Duel Position Control System for Rotating Disk Data Recording Devices,'' now United States Patent No. 4,396,959, 1980. Serial number 190 filed on September 24th
．． 198 et al., subject matter Serial No. 304,209, filed September 21, 1981, entitled ``Improvements to a Data Transducer Position Control System for Rotating Disk Data Storage Devices.'' Both of these Vf applications include a common 8-inch, non-removable media disk drive that provides four storage disks for online data storage (unformatted) spanning 40 megabytes. The Q2000i?Isk drive products have been very successful in the market.
With an average track access time of 5 milliseconds, a maximum storage capacity of 40 megabytes was achieved. This was accomplished through the use of an optical servo loop associated with a single servo sector on the disk surface. A programmed digital microprocessor receives cross information from the optical servo and track center Ij! from the servo sector. Error information is received, and it determines the truck's destination and trunk center.
A correction value was computed and the rotary actuator was commanded to move the theta transducer assembly onto the desired track and maintain it on the track during the data loading/swapping operation. Despite the fact that the original Q2000 data storage product achieved very high data storage capacity and a corresponding average track access time, it effectively doubled the data storage capacity and effectively reduced the average track access time. A need has arisen for higher capacity, higher performance disk drives that cut access times in half. High track densities are known in the prior art. For example, it is currently possible to achieve track densities of approximately 96o tracks per radial inch of disk data storage surface. Traditionally, the disadvantage of such densities has been the narrowness of the data storage tracks, resulting in data transduy track-following errors from mechanical resonances, vibrations, non-vibrating mechanical motion, thermal expansion, etc. It was said to be easy. 1
The preferred drive to achieve a track density of 960 tracks per inch had to be designed with great attention to mechanical stiffness and very high natural resonant frequencies. A highly complex closed loop servo system was required to maintain the transducer positioned within the selected data track so that there was no data loss during operation. Data transducer movement means. These stringent requirements for mechanical stiffness in the servo loops controlling such means have led to high production costs for manufacturers. OBJECTS AND SUMMARY OF THE INVENTION The general object of this invention is to A very high data density data storage device with significantly improved performance achieved with high reliability and low manufacturing costs by applying low cost, high performance technology to a rotating media rigid disk data storage device. It is another object of the present invention to combine an optical T encoder with a dedicated servo surface to provide optical trunk position and on-disk track centerline correction information to a microprocessor and then to provide a microprocessor with optical trunk position and on-disk track centerline correction information. Calculate the digital value using
A data storage device having a track width as narrow as 0.7 mm, a guard band as small as 0.6 mm, and a high track density of about 789 tracks per inch is used to seek the desired track. , on that track and provide a digital value to control the rotary actuator to keep the data transducer aligned on the centerline of the desired track. Furthermore, another object of the present invention is to have a higher performance τ′,
It is an object of the present invention to provide a closed-loop servo system for rigid rotary DC data storage that is simpler than the prior art. It is a further object of the present invention to provide a rigid rotating system that includes a new reinforced base casting that achieves significantly improved mechanical stiffness and heat dissipation properties while also achieving compactness. Another object of the present invention is to provide an improved control method d.
3 and [1] provide a data storage assembly for a rigid rotating disk data storage device for data transduction! The assembly is rotatably moved from the starting data track to the requested destination track at twice the average speed of the prior art, and the assembly is placed on the destination track more rapidly than before and the data read/occupation process is performed. During operation, the objective is to keep the 7 hinges clearly aligned to the required track J-. Yet another object of the invention is to provide a data transducer support arm assembly with characteristics that facilitate reduced length and size and improved manufacturability. These and other obvious objects and advantages include a substrate, a plurality of rotating rigid magnetic data storage disks rotationally journalled to the substrate, and close proximity to the surfaces of most of the disks by air-hairing effects. a plurality of read/write data transducers held in the disk; an actuator for positioning a transducer over one of a plurality of concentric data tracks during a write operation and for moving the transducer from track to track during a track seek operation. Achieved by improved equipment. Improvements to this device include the following collaborative and interactive structural elements: The optical encoder has a scale attached to an actuator and a light source/optical bin array assembly secured to the base. The scale is provided with a series of regularly spaced, extremely fine radial lines arranged to pass between the light source and the array;
A plurality of phase-related signals are provided indicating the position of the transducer relative to the substrate. One dedicated surface of the f-isk is divided into a plurality of radial sectors, each sector having a first offset from the track centerline in the first radial direction for the odd-numbered 1-racks and a second offset for the even-numbered tracks. The first bursts are pre-recorded in a plurality of first bursts offset from the track centerline in two opposite radial directions. The first burst is sandwiched adjacently between the second bursts to create a checkerboard pattern of two types of bursts. The servo bursts do not necessarily have to be coherent since they are not used by the phase +1 device to berth 1. Does the peak detector read out the servo surface? J-1-transducer, and it detects and outputs the averaged peak amplitude value for each seftana hover burst read by the transducer. An analog switch is connected to the optical encoder and peak detector. The analog switch simultaneously outputs a phase-related position signal and a peak amplitude value. An analog-to-digital converter is connected to the analog switch and converts each analog signal received therefrom into a digital word. A user interface circuit couples the device to the user equipment such that data is received and transmitted and the user's equipment commands disk surface and track selection via control data. A tachometer is mechanically coupled to the disk and generates a clock signal representing sector boundaries. The programmed digital microprocessor is
Connected to user interface, tachometer, analog-to-digital converter, analog switch and peak detector. The processor extracts digital control data words from the digital information received from these sources.
and command the rotary actuator to move from the starting trunk to the user-determined destination track, to set on the destination track during track seek mode, and to set on the track centerline during track following mode. The actuator is commanded to maintain the transducer υ in a straight line. The digital-to-analog converter is MicroProcera t1
is connected to receive the digital control data word and convert it to an analog signal value. A rotary \7 actuator drive H-position amplifier is connected to a digital-to-analog converter. It receives digital control values from there and sends current steps through rotary actuators that perform trunk seeking, setting and tracking. Additional structural aspects of the invention include reinforcement members for high structural stiffness for natural resonance and for improved thermal Wi,yA in the vicinity of the rotary actuator during maintenance of the required stiffness.

An improved substrate comprising a single textile material comprising an improved heat dissipating reinforcing member. Another structural aspect of the invention is an improved rotary system that achieves significantly higher torque and thereby moves data transducer assemblies from departure trucks to destination trunks at significantly higher average speeds. The purpose of the present invention is to provide an actuator assembly. Furthermore, the structural aspects of the invention +d, involve reduced length and size while maintaining the required stiffness;
Another object of the present invention is to provide a data transducer support arm suitable for easier WA construction than before. The improved data storage method of this method includes the steps of rotating a plurality of rigid magnetic media data storage disks associated with a substrate and the read/write data being held in close proximity to the auxiliary surface by air bearing effects. A transducer reads data from and moves data from and to a large portion of the surface of the disk, and a current-operated transducer moving means mounted on the substrate moves a large number of concentric data tracks on the surface. positioning a data transducer on the selected one; and providing a plurality of phase-related signals indicative of transducer position with respect to the substrate;
Offset from the track center line in the first direction for odd-numbered 1-racks, and in the second direction for even-numbered tracks.
pre-recorded with a plurality of first bursts offset from the position of the track centerline in the direction of
A plurality of pre-recorded, spread-shaped applying a vector to one servo surface of the disk; detecting and outputting an average peak amplitude value for each sector servo burst read by a transducer to the servo surface; switching in a controlled manner between the associated signal and a peak amplitude value of the servo burst; converting each switched analog signal to a digital word; and receiving digital disk surface and track selection control data from a user interface. a tachometer mechanically coupled to the disk, generating clock signals representative of sector boundaries; and processing the converted digital words and control data from the user interface to perform trunk seek operations. During a track following data read/write operation, the transducer is calculating a digital control word to digitally command the transducer 1 large displacement means to adjust in a straight line to the centerline 1 of the data track; converting the digital commands into analog drive currents for application to the means. This method 1 also includes one or more additional steps, such as providing a reference track identification to a look-up table; providing digital velocity profile data to a look-up table; referencing the look-up table; determining the seek magnitude and transducer of the seek 4J operating period given by the plurality of phase-related signals; commanding a velocity profile during the track seek operation by calculating and outputting a digital current value dependent on the actual position of the first phase-related signal; When the first signal reaches the zero axis, the amplitude of the other signal is measured periodically, and then the amplitude of the other signal is measured periodically until the first signal reaches the zero axis, and the signal is switched to the first signal. the step of repeating the measurement and providing quadrature phase signals;
Provides a lookup table for the digital arctangent value, calculates the arctangent angle from the lookup table, calculates the angle conversion value from the arctangent value, and outputs the conversion value as a track centerline correction digital current value. step and according to a defined algorithm [calculate the ticular track-following current as adjacent integers within a range between defined integer values, the middle value being determined as zero current, and in one direction. outputting the highest valid integer to command the vehicle to accelerate and outputting the lowest valid integer to command the vehicle to accelerate in the opposite direction. Other objects, advantages and features of the invention will become apparent to those skilled in the art from consideration of the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings. Dew. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS General System 10 Description An improved high capacity disk drive 10 incorporating principles of the present invention is shown in FIG. The electrical system is best understood by referring to the electrical system diagram in Figure 1. Disk drive 10 is formed in a cast aluminum base 11-L. The base body 11 includes reinforcing ribs and heat dissipation recesses depicted in FIGS. 3 and 4 and described below. Most of the surface is coated with magnetic storage medium 4
Two non-removable discs 12.14.16 Onibi 1
8 is rotatably supported by the base casting 11. These substantially parallel disks 12, 14, 16 and 18 are securely mounted on a rotating hub 19 which is journalled in the base casting 11. The hub 19 is driven either directly by an electric motor 13, an electronically commutated brushless DC motor, or by an AC motor 13 coupled by a flexible belt 15 as depicted in FIG. . One of the disk surfaces 2-o, such as the bottom surface of disk 14 (schematically shown as the non-top surface in FIG. 2), is dedicated to providing track centerline nervo information. The ray jlζ surface 20 is divided equally into, for example, 54 radial nervohictors. Each sector is
For example, it is depicted topographically in Figure 2, and
J3 is shown in less detail (as depicted, two centerline offset A'' servo bursts, and two centerline offset servo bursts sandwiched between and radially opposite from the A bursts). Two "B" servo bursts are recorded. Each sector also includes track zero TRg information, as explained below. Each servo burst does not need to be phase coherent with any other burst. The servo sectors and intersections A, B and track zero burst will be explained in more detail below.
9 will be installed. The code disk 22 defines sector boundaries, and a set of dual spokes 23 on the code disk 22 provide index signals for complete rotations of the disk. Perforated code disk 22 operates in conjunction with a magnetic transducer 26, such as a Hall effect transducer. The electrical) J signal from the transducer 26 is
A comparator 28 compares it with a reference signal. A digital comparison signal (pulse) is output by the comparator via sector boundary signal line 30 for each detected sector boundary. Line 30 is Microphone Prosetuna 3
2 interrupt line. Microphone 1:1 microprocessor 32 is preferably a type 8051 or equivalent manufactured by Intel Corporation of Zanta Clara, California.
It operates at a clock speed of 2MHz. Line 30 is the INT β bin (bin 1
2). Sector boundary signal line 30 also includes code 1 isk 22
It is connected to a one-round index detection circuit 34 that detects the index burst given by the double spoke 23 of. The output from the one-round detector 34 connects the drive 10 via a data and control bus 39 to an upper level comparator'.
A user interface circuit 38 is provided via line 36 to connect to the & The user interface 38 is connected to the microprocessor 32 via a continuous data line 40, and a seek completion sub-control line 41 extends from the processor 32 to the interface 38. Since there are eight primary data storage surfaces on the disks 12.14.16 and 18, there are eight data transducers 42.44.4 (3, 48, 50, 52, 54 and 56). 1- The transducer is of the well-known floating head or winch single star type mounted in close proximity to the disk surface based on air bearings or cushion effects. A pair of vertically arranged adjacent heads 44- to reduce crosstalk.
46.48-50. and inserted between 52 and 54. Head 48 is dedicated to reading prerecorded number-voice sector data on the lower surface 20'' of disk 14. Other heads 42. =1.4,46°50.52
', 54 and 56 are read/write transducers, which are connected to the selection circuit 58 for double sunlight. Selection circuit 58 is controlled by a signal from user interface 38 on multi-bit control line 59. The data to be written on the selected disk surface is sent from the host system via user interface 38 to head selection circuit 58 via line 60. The data read from the selected disk surface is
The signal is amplified by a power converter 62, recovered by a data recovery circuit 63, and then provided to the user interface 38. The servo sector data transducer 48 is connected to an amplifier 64 which increases the amplitude of the servo sector data hust read from the dedicated surface 20. The recovered data is then connected to an amplifier and filter circuit 66 and a peak detection circuit 68. The peak detection circuit 68 detects the continuously read offsets A and BJ5 from the center line.
and a squared output indicating the relative amplitude of each of the 1 to 0 bursts. The squared output of peak detector 68 is applied to a single switching pole of analog switch 70 . Analog switch 70 is controlled by digital data sent from microprocessor 32 via three bit control lines 72. The selected analog output from analog switch 70 then
Type 08 manufactured by National Semicontactor Corporation of Zanta Clara, California
It is converted into a digital word by the operation of a very fast analog-to-digital converter such as 20 or equivalent. Converter 74 samples each A and B servo burst over a period of 2 milliseconds under the control of microprocessor 32 via 3-bit line 75 and extracts the stripped peak value. Assign a digital value between 0 and 255. The 8-bit digital word is then transferred from 8 bits 1 to bus 76.
The microphone above is given to 1 prolet 1 and 32. Lotus 7
6 encodes the external data bus of the mark (cobroserie-32) with its associated address decoder and buffer logic (not shown). Equation where △ is the digital value of the last sampled △ burst, and B is equal to the value of the last sampled B burst.
-β rice equation, OV (even track) -l ψ-+-powder +128A-?
E? According to the above, calculate the offset value. The offset value is then used to address a lookup table previously stored in the read-only portion of microprocessor 32 with a digital offset correction value. As shown at J5 in FIG. 2, a beam 82 (or glass scale 84) is fixed to a rotary actuator 86. Light source 94
provides parallel light that is directed through scale 84 to masked optical transducer array 96 . Array 96 amplifies two quadrature sinusoidal signals which are further amplified by the operation of a pair of differential amplifiers 98 and 100. Amplifier 98 outputs a 1, P11 signal; Output P2 double. Pl and P
22, the track crossing information is sent to the microprocessor 32.
and is used as a physical reference point during servo writing onto servo surface 20 during manufacturing operations. The fifth cell and amplifier 97 have automatic gain control
Provides drive current to J3 and light source 94. Signal light source 94
J3 and masked array 06 are adjustably mounted on base casting 11 as a single backage as shown in FIG. An optical engineer assembly including a light source 94 and a masked array 96 is disclosed in common assignee U.S. Pat. No. 7rI 4,396,95.
9 in more detail. The positive values are output to the microprocessor 32 via bus 110 to a digital-to-analog converter 112 where they are converted to analog values. These values are corrected for phase delay in loop compensation network 114 (bypassed by electrical switch 115 during track-seek mode) during track-following mode and then in power amplifiers 116 and 118. and is amplified by the rotary actuator 86. Inverter 120 provides amplifier 118 with a value that is phase inverted and amplified from the value sent to amplifier 116 . These output elements of the servo lube system will be explained in detail in detail. Base Casting 11 Detail of the bottom of base casting 11 (as depicted in the bottom plan view of FIG. 3).
2 and a concave substrate surface 124. The thickened and reinforced portion 126 surrounds the pivot location for the rotary actuator assembly 8o. Drive motor fulcrums 130 and 132 are used to mount motor 13 to base 11 by threading bolts through apertures 134. The disk axle assembly is journaled through the base molding 11 to the hub axle 136. Base #
The raised portion 138 of the bracket 11 is partially shown in FIG. It is set up to hold. A series of reinforcing ribs erected on the base casting 11 are 3'
l lJ will be done. Counting counterclockwise from the pivot support 136,
These ribs are radial rib 142, transverse rib 144, early radial rib 146, and radial rib 1.
48, a radial rib 150, and a radial rib 152. A second lateral rib 154 and a separate vertical rib 156 are provided to roughly enhance the substrate surface 124 . The basic casting 11 is considerably thickened in the region 160 provided for the rotary actuator 8°. This thickened region 160 is provided with a series of generally parallel, laterally formed quadruple sections 162 defined by raised, generally parallel ribs 164 . Part 4 1
62 is formed as shown in FIG. 3 and provides continuous reinforcing ribs both in the lateral direction J3 and in the radial direction with respect to the pivot position 126 for the rotary actuator assembly 80. First. , the rib 164 determined by the recess 162 is
Provides for the dissipation of heat generated within the rotary actuator 80. Second, such a ramp 164 provides a base casting 11 that is substantially reinforced in the area that supports the rotary actuator assembly 80. The inventors have discovered that the use of a base casting as described and depicted in FIG. 3 provides substantial stiffness and increases the natural resonant frequency of the base casting 11, which device 10
This is a very important consideration in disk drives with increased track densities that provide greater booter storage capacity, such as . Rotary Actuator Assembly 80 The rotary actuator assembly 80 is mechanically depicted in an exploded view of its components in FIG. This rotor assembly 80 was manufactured on September 2, 1980.
Filed on the 4th, currently US Patent No. 4,39
It operates according to the same general principles as the rotary actuator depicted and described in common assignee co-pending United States patent application Ser. No. 190.198, No. 6,959. However, this rotary actuator 80 includes several significant improvements over earlier types, which will now be described. The base casting 11 has a reference fj in FIG. 3 on its upper side.
A rotary actuator shaft 172 is provided which is securely bonded to the four parts of the pivot in the base casting generally identified by reference number 126. Base tlj'/M object 11
The upper side includes the following components: a steel base ring 176, a lower permanent magnet 178, and a hub assembly 182.
A recess 174 is provided for mounting a rotary actuator 86, an upper permanent magnet 184, an upper steel shielding ring 185, and an aluminum top plate 186, to which a rotary actuator 86 is fixed. The plate 186 is provided with a recess 187 in which the upper steel ring 185 is held by adhesive. The steel ring 185 allows the magnetic field from the upper magnet 184 to
It acts as a shield to prevent erasure of data stored on the bottom surface of the lowermost disk 18. The plate 186 has an opening 189 in the top plate 1ε36.
It is securely attached to the top wall of the base casting by screws 188 passing through and engaging aligned, threaded holes 191 in the base casting 11. Hub 182 includes a spaced ball bearing assembly and another I-shape for rotatably engaging shaft 172 . Elements 176, 178, 184
, 186 and 188 remain fixed, whereas the rotary actuator 86 and its hub assembly 182 are connected to the alternately stacked rotor assembly 80.
rotates according to the central member of. The rotary actuator 86 has six windings 190, 192, 194, connected in series with two interleaved circuits wI202J> and 204 as depicted in FIG.
196, 198 and 200. circuit network 20
2 are connected via jacks 206 and 208. Circuitry 204 is connected by jacks 210 and 212. Each of the six coils 190-200 is formed from 113 turns of 26 gauge drawn copper wire coated with a suitable insulating varnish and has a measured resistance of approximately 4.7 ohms. Each coil is formed into a trapezoid-like shape. The six coils are arranged in a row at actuator 86 in a spaced configuration in a plane with respect to the apex pointing toward the solid shaft hub assembly 182, as shown in FIG. . The inventors have discovered that the use of a continuous top play 1-186 provides substantial mechanical stiffness to the rotary accuji:Lator assembly 80. Additionally, it has been discovered that the use of two magnets 178 and 184 increases the torque produced by rotor 86. The increased Iζ torque substantially reduces access time between separated data tracks. Referring again to servo loop output circuit FIG. 1, the microprocessor 32
When calculating the digital current value to be applied to the rotary actuator 86, this value is first
It is converted into an analog value by an analog converter (hereinafter referred to as DAC) 112. The DACI 12 is preferably of the type 1408 manufactured by Molla or an equivalent type. The analog output from DACl 12 is provided to lead-lag loop compensation network 114 during track following mode. During the track seek mode, the lead-lag loop compensation circuitry is connected to the micropro L? The analog output from the DACl 12 is bypassed by an electronic switch 115 operating under the control of the amplifier 1
16 and 118 directly. Analog switches, not shown, switch the inputs of amplifiers 116 and 118 between loop compensation circuit 1148 and DACl 12 under control of microprocessor 32. Loop compensation circuit 114 is preferably implemented with an operational amplifier coupled to provide the necessary phase lead to prevent negative feedback (oscillation) in the servo loop. The phase margin of the servo loop of disk drive 10 is approximately 35° to 400° (the phase margin is equal to the oven loop unity gain phase shift with a 180° phase shift, and the loop has positive feedback and negative feedback). Becomes stable ('R, swing))
. The phase shift applied to the loop of the drive device 10 is 14
5° to 150° (1800-phase margin). The loop gain of the closed loop is increased by J3C in the drive 10 and the transducer array 9 is increased in short time intervals.
Set to 0. Usually a phase margin of 35° to 400° (
It becomes ring-shaped and attenuates very slowly. By increasing the loop gain and including the output of the phase ring cancellation circuit in the Reed-La loop compensation circuit 114, the overage 1-1-,t is effectively canceled and the loop is rotationally limited. In this manner, system 10 ignores overshoot and rotation without it, and rapidly sets up transducer assembly 90 with minimal phase margin. Rotor Amplifiers 116, 118 FIG. 6 shows the circuit details of rotary amplifiers 116 and 118. The circuit includes an input connection point 220 that receives an input control voltage vin. Amplifiers 116 and 11
8 is preferably 5GS-
The inverting amplifier 120 is preferably implemented with two identical monolithic integrated circuit operational power amplifiers, such as the DΔ2030 integrated circuit audio power amplifier array manufactured by ATES Semiconductor Corporation, or its equivalent. Amplifiers 116 and 118 are type LM324 interference amplifiers manufactured by National Mini 1 Contactor of Santa Clara, State of California, or equivalent.
2 and 204. The resistive elements of network 202 are depicted as series resistors 222 and are connected to network 204.
The resistive element of is depicted as a series resistor 224. A 1 ohm current forcing reference resistor 226 is connected in series between networks 202 and 204. Its significance will be briefly discussed below. Two 68Ω shunt resistors 228 and 230 connect networks 202 and 20, respectively.
connected in parallel across 4. Resistor 228, along with network 202, reaches a final value of approximately 500
Up to 0H7, the impedance is 6 CI per Δ tave.
B is increased and an L-R network is formed by increasing the impedance characteristic 11 of 50 to 500 Hz. The same is true for the L-R network formed by resistor 230 and network 204. At a load impedance of 68Ω, each amplifier 11!3.
11ε reaches the final gain of Pobo 137. Each amplifier 116 and 118 is 10.0001-
It characteristically rolls off at 1z (with a gain of 137). Nevertheless, each amplifier 116 and 118
High frequency stabilization of each monolithic amplifier 116 and 118 is required due to the length of the leads between the actuator 86 and the actuator 86 . This stabilization is provided by an R-C network including a 1 Ω resistor 232° 236 and a 0.22 microfarad capacitor (234, 238). This network rolls off each amplifier 116 and 118 at approximately 720K) (z) and provides unity gain stability. Four diodes 240.2 = 12, 244 and 24
6 is a typical protection for monolithic amplifiers 116 and 118 against voltage changes appearing at their outputs, as shown in FIG. 6. A voltage reference circuit is not shown, but A Zener diode connected in series with a resistor between ground and the power supply V+ acts as a suitable reference circuit. In this example, the reference voltage vR is 6 volts and the power supply V+ 24 volts. 6 equal high value resistors (100 KO) 250 volts,
252, 25' 4, 256, 258iJ3
and 260 are connected as shown in FIG. Resistors 250 and 252 are connected to the output connection point V. pH at
- Setting the gain and high input impedance to the amplifier 116. Resistors 254 and 256 are the output node to amplifier 118. Set the unit system iE7 J3 and σ high input impedance. resistor 258 and 2
C30 sets the 111-gain 1q and high impedance for the inverting amplifier 120. Amplifiers 116 and 118 are driven differentially. They operate linearly over a range of ±1 volt of the input. At an input of approximately 1 volt, the amplifier begins to saturate, which means that the output current driven through circuits wi4202 and 204 (J1 remains the same as the input voltage outside the range of 1 volt). The linearity of this circuit is determined by the resistance of the two series networks 202 and 204 and the voltage effects due to amplifiers 116 and 118. The maximum amount of current achieved is approximately 2 Amps. According to classical theory for a differential amplifier arranged as an inverting amplifier such as a Since the output circuit (amplifiers 116, 11
8, including ■in to V. l\), the gain is unity. Since the current flowing through the feedback resistors (252, 256) is the same as the current flowing through the input resistors (250, 254), each feedback resistor 252, 256 has an output voltage (v0' or -V). be the same as the input voltage viri'. The current required to maintain the output at the same voltage as the input is determined by the forcing resistor 226 and networks 202 and 204.
flows through. For example, if the input voltage in is +1/2v
Assume that. A current of 1 ampere flows from ■+ through the second amplifier 118, the coil 204, the forced resistor 226, the coil 202° and the first amplifier 116 to ground. At 0°25V, the current flowing is 0.55 Amps. At an O volt input, no current flows. FIG. 7 shows the current flowing in proportion to the desired translational position change. Referring again to FIG. 1 and considering FIG. 7, converter 112 converts digital values to analog current steps. These current steps are converted into analog voltage steps by a current-to-voltage converter. If the measured value is outside the range u11 of ±1 volt, the output J amplifier circuit
A linearly proportional current is passed through I. If the 51n value exceeds 1 volt, then maximum current will flow through the network. For example, when a current of 3 amperes is commanded to pass through the coil, their resistance (approximately 50) will cause a maximum current of 41 t.
f limited to 2 amps (on a 24 volt power supply). The minimum current output to amplifiers 116 and 118 is determined by reference to a digitally stored acceleration lookup table to cause an acceleration of the position actuator 1 to be greater than or equal to the minimum acceleration value tracked by processor 32. When the input voltage ■in is equal to OV, no current flows through networks 202 and 204, which means that input voltage [1
Unless the controller 32 commands the actuator 80 to move by generating a digital value that finally appears as a differential voltage 1n at the input 220, until then the heat l15! It means not to miss it. Track Follow Modes of Operation The microprocessor-based control system of disk drive 10 has two basic modes of operation: track centerline jβ follow mode and track seek mode. During the track following operation period, the Microprocessor I32
subtracts the positive amount required to keep the transducer in line with the track centerline and increases the DA
Cl 12 into 256 possible analog correction voltage values, timed by compensation network 114 to provide proper servo loop phase compensation, and amplifier 11
6 and 118 to output a digital correction signal which is then applied to rotor 86 as a drive signal. A new correction signal is calculated for each servo burst. The microprocessor 32 is capable of outputting 216 centerline 3] positive values for each rotation of the disk. Thus, due to disk hub bearing runout and thermal expansion occurring in real time, drive system 10 automatically compensates for such centerline offlet errors. The 1-to-easy follow mode is best understood by referring to FIG. There are 54 identical sectors throughout the servo surface 20. Figure 8 shows tracks 0, 1,
The internal shape of one such sector falling in the area of 2J'3 and 3 (the outermost data cylinder) is shown. Very short duration sector pulses are generated by the secondary disk 22 and the Hall effect sensor 26. The sector pulses cause the microprocessor 32 to rerun 1 in track following mode. Each sector is
The time width is approximately 360 microseconds. Each sector includes five bursts, two staggered A-berths 1 to 8 interleaved with A-nosets from the two centerlines, followed by a track O burst. Each burst occupies 72 microseconds during the disk rotation period. The track O burst is one-numbered only at the end of the seek mode operation to determine whether the outermost track, 1, track O, has been reached. Truck○
The burst is actually an A burst that exists not only on the outermost track, but on all sectors of all other inner tracks. The use of trailing trunk O bursts numbers the processor 32 microcode. When the sector pulse "resets" the processor 32, the processor begins counting sector intervals.
commands analog-to-digital converter 74 to sample and convert the peak value of the A burst available at peak detector 68 by operation of analog switch 70. The sampling period lasts approximately 12 ficroseconds. The microprocessor 32 processes the three last obtained A/
Memorize the B peak zamble. Each new ripple replaces the oldest accumulated sample. In this way, the data library of A/B peak values is constantly continuous by the replacement of the three stored values as new numbers are received and stored in the registers of processor 32. Micro 10 Hina 32 detects the difference in magnitude between the last two sampled A/B peak values. The computed difference between A and B beaks is used to address a look-up table in pre-stored processor 32 single-only memory. The correction value is located on the address and is applied by the processor 32 to the rotary actuator 8 as already explained.
6 is output to ii1 correct. The correction value moves the actuator 86 and therefore the transdeconner 90 towards the track centerline. The microprocessor 32 requires approximately 58 microseconds to perform each correction 31 calculation, including processing the data required, before starting the next burst. Approximately 2 microseconds are required before the data is sampled and the next data correction value is determined.As shown in Figure 8, there are four samples and calculations made for each sector. , disk 12
The process is repeated continuously for each of the 54 sectors during -18 complete rotation periods. Since track O bursts are ignored during the track following mode of operation, processor 32 enters a wait state at the end of the fourth decision made in each sector. The wait state ends with the arrival of the next sector pulse, and the 4-no-pull decision process is repeated before the next sector. The trunk seek operation seventh microprocessor 32 constantly monitors the actual track position of the data transfer driver 90. During the initial power-up period, processor °32 commands the actuator to seek the outermost track (track O). Once track O is reached and confirmed by the absence of the third A burst on the L lid, processor 32 detects that it is on track O and immediately initializes the internal track counter. Ru. As the track is traversed during the seek period, P which arises from the synchronous movement of the scale 84 between the light beam from the fixed light source 94 and the fixed masked photodiode array 96 in phase %I. The track counter is incremented and decremented according to the cycles of the 1 a3 and 1) 2 quadrature signals. Track selection information is transmitted from the serial data line 40 via the user interface 38 to the microbrlt? Tsuv
321 people were arrested. Line 40 provides successive stepping pulses to microprocessor 32 on pin 14 (I/+). Processor 32 includes an internal direct connection to a 91J resistor;
16B/S1 track selection information is received via serial line 40. A 16-bit data word is sufficient to identify any one of the 1172 valid concentric data tracks (cylinders). Microprocessor 32 calculates the required truck position by adding the number responding to the destination trunk to the current trunk number. An advantage derived from the use of a very fast analog-to-digital converter 74 (2 microsecond conversion time) is that the microprocessor 32 can detect Pl and It follows directly from the P2 quadrature sine wave. The analog values of Pl and 12 are switched to an analog-to-digital converter 74 by an analog switch 70 under the control of a microprocessor υ32. During seek mode, the micropro Sec-32 commands the speed protweet by reference to an internal lookup table stored in its internal read-only memory. The actual position of transducer Ln 90 is determined by J: Pl and P
Monitored from the 2nd position signal. During the high velocity center position period of a seek, the Pl and P2 signals change rapidly, so it is practical to consider only one of these sinusoids. For example, at maximum speed, each sine wave P1 or P2 cycles for approximately 50 microseconds. The minimum processing loop required for monitoring track position is a 12 MHz microbroselli clock frequency, with each instruction cycle requiring only 1 microsecond. During the slow end portion of the seek operation, Pl continues until it reaches the zero axis (midpoint); The processor 32 switches to follow P2. Their tracking continues through the slow portion of the seek operation until the tracked P 113 and P2 reach the zero axis and switch to the other. During the seek operation, the micro The processor 32
and detect when the midpoint of the P2 sine wave reaches. At each waypoint J3, processor 32 determines that a track boundary has been reached and it increments or increments its internal track position counter depending on whether assembly 90 is moving away from or towards track O. reduce At the end of a seek, the processor 32 enters a setup navigation mode that uses the values of the quadrature sine wave generated from the optical encoder assembly (88, 94, 96). is preliminarily determined by reference to values in a velocity profile look-up table that indicates the expected time of arrival of the assembly fly 90 at the destination truck relative to the distance. Calculate the angle of the position of assembly 90 by calculating the arctandiene I angle from the Pl and P2 sinusoids.
is determined by reference to a lookup square containing 64 values of the arctangent between A simple table can be operated over the other seven half quadrants of the circle. Thus, a true circumferential servo system using quadrature signals P1A'3 and ]]2 can be recognized by the fidgets. The processor 32 commands the actuator 86 to move over the "optical trunk centerline" of the destination track based on the angular shift (in) resulting from the arctangent reduction. Rack centerline'' is not the actual track centerline, but the approximation rapidly places the assembly 90 in the vicinity of the destination truck centerline. See processor 32, the assembly 90 is associated with the destination truck for a predetermined time interval. The counter remains within the set servo loop until set within a predetermined travel range.The counter of the pro-tuna 32 is reset each time a range boundary is crossed during the set period, e.g. without resetting. After 20 inputs, assembly 901.t is determined to be fully configured and the processor 32 enters the track following mode. Upon initial input from the track following mode or seek operation, the processor 32 , commands the actuator 86 to move to the actual trunk centerline according to a single step function. Once the assembly 90 is set on the actual destination truck centerline, the user interface 38
Passeek Complete" line 41. Interface 38 then passes this state over three buses onto the host device and normal read/store operations are performed on the destination track. For example, in a 40 millisecond seek (average seek), the seek value from the look amplifier table tells the processor that assembly 90 is expected to arrive at the destination track in about 30 milliseconds. 32 will be notified. After 30 milliseconds, processor 32 enters the set servo loop mode and re-controls the PIJ3J, 1)2 signal from the optical encoder assembly. This mode runs for about 5 milliseconds. Finally, the program tree 32 selects A/
Enter track following mode using the 1B servo sector. This final centerline adjustment requires approximately 2 milliseconds before the seek complete signal is output. At the end of each seek, the microprocessor 32 (well, takes a value midway between the three servo-controlled A/(3 burst peaks (1α, which is the A burst) after R and adjusts that value to O burst). Compare with the rimple of This calculation G provides a determination of the relative peak value for track O that accommodates the differences between the various drives 10. If a particular drive 10 has a lower output power than the servo transducer 48 The relative determination of track O (performs better if
Device 10J5 produces a track O determination system that is independent of the particular gain characteristics of the electronic circuitry associated with it. It will be appreciated that the servo control system for drive 1o is a closed loop system during both track following and track seeking modes of operation. By maintaining a closed loop during the setup period, and by servoing the P 1 d5 through P2 signals, the drive circuit 10 ensures that the setup time is the same as that actually required for each seek. In some uses of the seek, assembly 90 actually apertures the destination track slightly and requires slightly more setup time. In case J3, the closer and parallel the lookup seek profile is to the actual position of movement of assembly 90, the less time is required. In each course, as much time as is necessary for the particular state of the seek is spent configuring. This method is described in U.S. Patent No. 4,395.95.
9, the common assignee's preceding Q200
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[Brief explanation of drawings]

FIG. 1 is an electrical block diagram of the overall system of an improved disk drive incorporating the principles of the present invention. FIG. 2 shows the mechanical elements of a disk drive employing the principles of the invention electrically depicted in FIG. It is a schematic diagram of the surface structure of the a-shibe. 3 is a bottom plan view of the base casting of the disk drive depicted in FIGS. 1 and 2; FIG. FIG. 4 is an exploded view showing the details of the lance du-length arm rotor assembly of the disk drive device shown in FIG. 1 J5 and FIG. 2. FIG. 5 is an electrical circuit diagram of the connection of the coils including the rotor of the lance duplexer arm rotor assembly depicted in FIG. 4; FIG. 6 is an electrical circuit diagram illustrating a further portion of the servo loop of the disk drive depicted in FIGS. 1 and 2. FIG. FIG. 7 is a graph of data transducer position plotted against current flowing through the rotor coil of the actuator of the disk drive depicted in FIGS. 1 and 2; FIG. 8 is a greatly enlarged timing diagram of the outer track portion of one of the pre-recorded servo sectors of the disk drive not depicted in FIGS. 1 and 2. FIG. In the figure, 1o is a disk drive device, 11 is a base casting, 12, 14, 16, 18 are non-removable disks, 20 is a servo surface, 22 is a rotating code disk, 2
6 is a magnetic transducer, 28 is a comparator, 32
is a microprocessor; 34 is an index detection circuit;
38 is a user interface circuit, 42, 44, 46
, 48, 50, 52, 54, 56 are data transducers, 57 I; t shield, 58 are selection circuits, 63 are data circuit 1u circuits, 66 are filter circuits, 68 are peak detector circuits, 70 are analog switches , 74 is Anna 1:
1 a digital transducer, 80 a rotary actuator assembly, 84 a glass scale, 86 an actuator, 90 a data transducer assembly, 11
2 represents a digital-to-analog converter, and 114 represents a loop compensation network. Patent Applicant: Kraontum Corporation Continued from Page 1 0 Inventor: Donald Shi Westwood 878 441 Pertino Rose Protusum Drive, California, United States of America

Claims (1)

Claims: (1) a base body, a plurality of rotating rigid magnetic media data storage disks commonly pivoted to said base body for rotation, and in close proximity to a majority surface of said disks by air bearing effects; a plurality of read/write data transducers held in the disk; a rotary actuator transfer II pivoted on the base body and having an axis of rotation parallel to the axis of rotation of the disk and operated by electrical current; transporting the transducers and positioning them over one of a number of concentric data tracks during a data read/write operation, and transporting the transducer during a track seek operation of the device. a data storage device for moving a deuser from track to track, the data storage device being mounted between the transfer mechanism and the base body;
an optical encoder means for providing a plurality of phase-related signals indicative of the transducer position relative to the transducer; and a surface of the marking disk divided into a plurality of radial sectors, each sector in a first direction relative to an odd numbered track. and offset from the track centerline in a second direction for even numbered tracks, and spatially interleaved between said first bursts. , offset from the trunk centerline in the second direction for odd numbered tracks, and offset from the track centerline in the first direction for even numbered tracks. and the bursts, not necessarily phase coherent, are connected to a transducer that reads out the servo surface;
peak detection means for detecting and detecting an average peak amplitude value for each sector servo burst read by the transducer; analog switch means for switching between a phase-related position signal and said peak amplitude value of said sector burst; and analog switch means connected to said analog switch means for converting each analog signal received therefrom into a digital word. digital transducer means; a user interface for receiving digital disk surface and track selection control data; face circuit means; tachometer means mechanically coupled to said disk for generating clock signals representative of sector boundaries; said analog-to-digital converter means and said analog switch means for receiving digital data from said analog-to-digital converter means and said user interface circuit means, and for receiving digital control data therefrom; and commanding said rotary actuator to move from a starting track to a user-determined destination track and set thereon based on information from said optical encoder means during a track seek period; programmed digital microprocessor means for commanding a rotary actuator to maintain the data transducer in line with a track centerline based on information from the peak detection means during a track following period; digital-to-analog converter means connected to said microprocessor means for receiving said digital control data words and converting them to analog signal values; and digital-to-analog converter means connected to said digital-to-analog converter means for receiving said analog signal values; and rotary actuator driver amplifier means for amplifying and outputting the transport mechanism during track following periods and during trunk seek and setup periods, respectively. (2) further comprising an improved rotary actuator in the transfer mechanism, the actuator having a magnetic flux that returns a fixed base plate, the magnetic flux returning a top plate and a first generally annular A permanent magnet is securely mounted on said fixed base plate and is characterized by an even number of adjacently opposed magnetic field sections with alternating north poles and S8i on the majority surface thereof, and a second A generally annular permanent magnet of the generally annular permanent magnet is securely attached to the magnetic flux returning the top plate and has an arrangement of opposed magnetic field segments identical to the first magnet. can be,
A rotatable coil assembly is placed between the first and second magnets and is spaced close to the first and second magnetic fluxes; a plurality of coils, the coils being aligned adjacent to the linearly aligned magnetic sections in at least one rotational position of the assembly; 2. A data storage device as claimed in claim 1, wherein the transfer mechanism is connected to two series windings disposed adjacent to the assembly and sandwiched oppositely, the transfer mechanism being attached to the assembly. Apparatus. (3) The base body includes an enclosed section containing the rotary actuator, and the base body includes an externally reinforced or curved surface adjacent the section to dissipate heat generated by the actuator. 2. The data storage device according to claim 2, wherein the base body extends generally radially outward from a shaft support for the rotary disk and a shaft support position of the rotary actuator. a casting including an elongated integrally reinforcing rib member, said casting further including a heat dissipating surface formed on a majority surface of said exterior adjacent said pivot location, said casting including a heat dissipating surface formed on said exterior majority surface adjacent said pivot location; 5. The data storage device of claim 1, wherein the transfer mechanism includes a plurality of radial arms, each of which has an expander attached to the acticoator assembly. each arm has a widest opening adjacent its wide end and a narrowed end mounted on at least one said transducer; generally aligned in the longitudinal direction of said arm with a minimum frontage adjacent the end;
A data storage device according to claim 1, characterized in that it determines a succession of adjacently spaced circular openings of decreasing diameter. (6) The programmed microprocessor means commands track following by dividing one of 64 adjacent lζ integers between 96 and 160, and the 1-rack centerline is determined by the equation, ♂ 128, where A is a digital word corresponding to the average peak amplitude of the burst of Arrival, and B is:
2. A data storage device as claimed in claim 1, characterized in that it is a digital word corresponding to the average peak amplitude of other types of parses 1 to 1, both of which are read by said servo transducer. (7) The programmed digital microbe [
1 setter commands a track seek by outputting the highest valid integer that commands acceleration of the rotor in one direction and the lowest valid integer that commands acceleration of the rotor in the other direction; A data storage device according to claim 6. (8) Said rotary actuator driver amplifier means is configured to substantially energize the coils of said rotary actuator when said servo transducer is aligned with the centerline of a selected track during a track following period. A data storage device according to claim 2, comprising a bush pull amplifier configured as a non-current complementary constant voltage differential amplifier. (9) A disk drive in a data storage device, comprising: a base molding; and a plurality of non-removable rotationally rigid magnetic media data storage having a series of four concentric data tracks for storage data, the base molding being pivotally mounted to said base molding for common rotation therewith. a disk; means for rotating said disk; and a plurality of commonly mounted successive/write data transducers held in close proximity to a majority surface of said disk by air bearing effects; 5J@ transport means mounted on the substrate #h structure for commonly moving the data transducer with respect to the data tracks of the disk; actuator means; an optical encoder means operable between the transfer means and the substrate casting or the like to generate a plurality of periodic, phase-related signals indicative of the position of the transfer means relative to the substrate casting; one of the data surfaces of the disk is offset from a track centerline in a first radial direction for odd numbered tracks and offset from a track centerline in an opposite second radial direction for even numbered tracks; a plurality of first bursts and a plurality of second bursts sandwiched adjacently between said first parses 1- as a pre-recorded servo surface; The bursts are offset from the track centerline in the second direction for odd-numbered tracks and in the first direction for even-numbered tracks, and each burst is distinct from any other burst. Rather than being phase coherent, one of the data transducers is dedicated as a sequence-only transducer reading out the servo surface and operates between the disk and the substrate casting so that the burst is sector boundary generation means for generating electrical pulses denoting the boundaries of a plurality of sectors on said servo surface present; and an average for each burst connected to said dedicated servo transducer and read by said servo transducer. peak detection means for calibrating and outputting a peak amplitude value, the peak detection means being connected to the optical encoder means and the peak value detection means for switching between the plurality of phase-related position signals J3 and the peak amplitude value of the burst; Analog switch means, a transformer 1 connected to the other data transducer and the host system, including a transducer selection circuit, digital disk surface and data track selection control data J3, and the other transducer's' Knee 1r interface circuit means for receiving data to be written to a selected data track via one of the >ILJR interface circuits; said analog-to-digital converter means; said analog switch means; and said Cd sector boundary. the generating means and the user interface means;
controlling said actuator means to control said transfer means to receive digital words from said analog-to-digital converter means and said kneading interface means and calculate therefrom a digital control word; Move from the position to the destination track position and set it on it during the track seek operation period,
A programmed digital Ifi! that maintains the transducer in line with the track centerline during track following operation! digital-to-analog converter means connected to said digital control means for receiving said digital data control leads and converting them into proportional analog signal values; and said digital-to-analog converter. lead-lag voltage loop compensation means connected to the means for providing phase compensation to the analog signal value during a track following operation; and amplifier means connected to an analog converter means for amplifying said analog signal value and driving said actuator in accordance with said value to improve performance. (10) the periodic phase-related signal output by the optical encoder means includes a pair of sinusoids in quadrature, and the control means adjusts the position of the transport means with digital values responsive to the sinusoids; The disk drive device according to claim 9, comprising means for determining. (11) The disk drive device according to claim 9, further comprising reference track detection means for detecting when the servo transducer is located on a predetermined reference track. 12) The servo surface includes a burst arrangement in the reference track that coexists with the burst arrangement of all other data tracks, and the control means includes means for testing the presence of the particular burst arrangement. A disk drive device according to claim 11. (13) rotating a plurality of rigid magnetic media data storage disks relative to a substrate; and a read/write data transducer held in close proximity to the surface by a V-air bearing effect, with a majority of the disks a step of transmitting and writing data from a surface of the substrate, and moving the data transducer to a plurality of concentric circles on the surface, with an electric current operated lance transducer moving means mounted on the substrate. positioning on a selected one of the data tracks of the disk; providing a plurality of phase-related signals indicative of transverse position with respect to the substrate; and providing sectors, each sector being offset from a track centerline position in a first direction for odd numbered tracks and offset from a track centerline position in a second direction for even numbered tracks. pre-recorded in a plurality of first bursts; an average peak amplitude value for each sector servo burst previously recorded with a plurality of second bursts offset from track centerline in the first direction for even numbered tracks and read by a transducer for the servo surface; switching in a controlled manner between the plurality of phase-related signals and the peak amplitude value of the servo burst; converting each switched analog signal into a digital word; a slap for receiving digital disk surface J3 and track selection control data from a 1-9 finger interface; a schedule for generating a signal, processing the converted Iζ digital word from the user interface and the control data, and operating with current from a starting data track position to a destination track position during a single link operation. 1 - digitally commanding the transducer moving means to move and aligning the transducer with the data track centerline during track following data read/write operations; A digital control is used to digitally command the transducer moving means.
011 words/words; and converting the digital commands into analogue drive currents for use with the transducer moving means. (14) The method further comprises the step of providing overlapping reference track identification data relative to the reference track on the surface of the small sector as an additional burst in each of the sectors except on the reference track and rack. 14. The data storage method according to item 13. (15) directing the transducer to the reference track during an initial operation period; - setting a digital track counter to the reference value while the transducer is located on the reference track; according to the initial count corresponding to the starting track and during the track seek operation according to the track position digital value 4 obtained from the phase-related signal as the transducer moves away from or approaches the reference track. , further comprising the step of incrementing or decrementing the track counter. (16) providing look-up table speed profile data; determines the velocity profile during the track seek operation by commanding and depends on the speed of the seek and the actual measured position of the transducer provided by the plurality of phase-related signals during the seek operation. 14. The data storage method of claim 13, further comprising the step of: determining and outputting a digital current value at which the first phase-related signal has a minimum f's+ at that value. the step of periodically measuring the amplitude of the first signal as it changes to a maximum, and measuring the other phase-related signals when the first signal reaches C (amplitude midpoint); switching, then periodically measuring the amplitude of the other signal; switching back to measuring the first signal when the other signal reaches the zero axis; and track seeking. continuing to switch between the phase signals of the first and second fractions during a period of operation;
14. The method of claim 13, further comprising: a schedule for monitoring the actual radial position of the transgear relative to the disk surface. (18) Given the phase signal in quadrature, providing a lookup table of digital arctangent values in a predetermined range including the range from zero to one, and calculating from the quadrature signal by referring to the lookup table Calculate the arctangent angle by 11, calculate the angle conversion value from the arctangent angle,
applying said value as a track centerline correction current value to said transducer moving means to move said transducer in the vicinity of a track centerline; 14. The data storage method as claimed in claim 13, further comprising the step of setting the track center line near the track center line upon completion of a track seek operation by correcting the line to be aligned with the actual track center line. (19) further comprising the step of dividing the digital track following value as 64 adjacent integers in the range from 96 to 160, the track centerline being determined by 128 according to the equation: is a digital word responsive to one average peak amplitude value of the second burst, and B is
'+! is a digital word responsive to the average peak amplitude value of the other first and second bursts read by the servo transducer. ff [Claim 1
3. Data storage method according to item 3. (20> Track seek comprises: outputting the highest valid integer commanding the transducer movement means to accelerate in one direction; and accelerating the transducer movement means in the opposite direction. 20. A data storage method as claimed in claim 19, including the step of outputting the lowest valid integer that commands.