Touchdown detection for multiple actuators on magnetic recording device

According to an embodiment, a controller of a magnetic disk device executes control such that detection of touchdowns of one or more first magnetic heads and detection of touchdowns of one or more second magnetic heads are executed at different timings. In addition, the controller executes control such that touchdowns of the one or more first magnetic heads are detected at different timings and touchdowns of the one or more second magnetic heads are detected at different timings.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2020-157430, filed on Sep. 18, 2020; the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a magnetic disk device and a method.

BACKGROUND

It is necessary to reduce a flying height of a magnetic head from a magnetic disk surface in order to increase a recording density of a magnetic disk driven by a magnetic disk device. A dynamic flying height (DFH) technique is sometimes used in order to reduce such a flying height of the magnetic head. In order to accurately control the flying height with this DFH technique, it is necessary to detect a state where the magnetic head is in contact with the magnetic disk. The state where the magnetic head is in contact with the magnetic disk may be referred to as a touchdown.

In addition, there is known a magnetic disk device capable of independently moving two or more magnetic heads respectively by two or more actuator systems.

DETAILED DESCRIPTION

According to the present embodiment, a magnetic disk device includes a magnetic disk, one or more first magnetic heads and one or more second magnetic heads, a first actuator system, a second actuator system, and a controller. The one or more first magnetic heads and one or more second magnetic heads record data on and read data from the magnetic disk. The first actuator system moves the one or more first magnetic heads. The second actuator system moves the one or more second magnetic heads. The controller executes control such that detection of touchdowns of the one or more first magnetic heads and detection of touchdowns of the one or more second magnetic heads are executed at different timings. In addition, the controller executes control such that touchdowns of the one or more first magnetic heads are detected at different timings and touchdowns of the one or more second magnetic heads are detected at different timings.

Hereinafter, the magnetic disk device and a method according to embodiments will be described in detail with reference to the attached drawings. Note that the present invention is not limited to the embodiments.

Embodiment

FIG. 1is a diagram illustrating an example of a configuration of a magnetic disk device1according to an embodiment. The magnetic disk device1can be connected to a host2. A standard of a communication path between the magnetic disk device1and the host2is not limited to a specific standard. In one example, serial attached SCSI (SAS) can be adopted.

The host2corresponds to, for example, a processor, a personal computer, or a server. The magnetic disk device1can receive access commands (read command and write command) from the host2.

The magnetic disk device1includes a plurality of magnetic disks300that rotate about a rotary shaft330of a spindle motor (SPM)310. Here, as an example, the magnetic disk device1includes six magnetic disks300-1,300-2,300-3,300-4,300-5, and300-6. The six magnetic disks300-1,300-2,300-3,300-4,300-5, and300-6are integrally rotated by the SPM310.

Recording surfaces on which data can be recorded are formed on front surfaces and back surfaces of the six magnetic disks300. The magnetic disk device1includes 12 magnetic heads HD11to HD16and HD21to HD26in order to access each of a total of 12 recording surfaces configured by the six magnetic disks300.

The magnetic head HD11is provided so as to face the front surface of the magnetic disk300-4. The magnetic head HD12is provided so as to face the back surface of the magnetic disk300-4. The magnetic head HD13is provided so as to face the front surface of the magnetic disk300-5. The magnetic head HD14is provided so as to face the back surface of the magnetic disk300-5. The magnetic head HD15is provided so as to face the front surface of the magnetic disk300-6. The magnetic head HD16is provided so as to face the back surface of the magnetic disk300-6. The magnetic head HD21is provided so as to face the front surface of the magnetic disk300-1. The magnetic head HD22is provided so as to face the back surface of the magnetic disk300-1. The magnetic head HD23is provided so as to face the front surface of the magnetic disk300-2. The magnetic head HD24is provided so as to face the back surface of the magnetic disk300-2. The magnetic head HD25is provided so as to face the front surface of the magnetic disk300-3. The magnetic head HD26is provided so as to face the back surface of the magnetic disk300-3.

Hereinafter, the 12 magnetic heads HD11to HD16and HD21to HD26may be collectively referred to as the magnetic head HD. Each of the magnetic heads HD can access the recording surface provided on the surface of the magnetic disk300facing itself, that is, record data and read data.

The magnetic disk device1includes two actuator systems110and210that can be driven independently of each other.

The first actuator system110includes a voice coil motor (VCM)111, four actuator arms120, and six suspensions130. Each of the six suspensions130provided in the first actuator system110supports any one of the magnetic heads HD11to HD16. Each of the six suspensions130provided in the first actuator system110is attached to a distal end of any one of the four actuator arms120.

The second actuator system210includes a voice coil motor (VCM)211, four actuator arms120, and six suspensions130. Each of the six suspensions130provided in the second actuator system210supports any one of the magnetic heads HD21to HD26. Each of the six suspensions130provided in the second actuator system210is attached to a distal end of any one of the four actuator arms120.

The two actuator systems110and210can rotate about a rotary shaft320. The rotary shaft320is provided at a position parallel to the rotary shaft330and separated from the rotary shaft330. The VCM111can rotate the first actuator system110within a predetermined range about the rotary shaft320. The VCM211can rotate the second actuator system210within a predetermined range about the rotary shaft320. Accordingly, the first actuator system110can move the magnetic heads HD11to HD16relative to the recording surfaces of the magnetic disks300-4to300-6in the radial direction. The second actuator system210can move the magnetic heads HD21to HD26relative to the recording surfaces of the magnetic disks300-1to300-3in the radial direction.

FIG. 2is a view for describing a positional relationship between the actuator systems110and210and the magnetic disk300according to the embodiment. As illustrated in this drawing, the actuator systems110and210moves the magnetic head HD relative to the recording surface of the magnetic disk300along a locus T. Note that the magnetic disk device1is provided with a ramp load mechanism340for parking each magnetic head HD on the locus T near an outer end of the magnetic disk300.

The description will be given with reference toFIG. 1again.

The magnetic disk device1further includes a first system-on-a-chip (SoC)100, a second SoC200, head amplifiers140and240, and servo controllers (SVC)150and250.

The head amplifier140amplifies a signal, read from the magnetic disk300by the magnetic heads HD11to HD16(more specifically, read elements402provided in the magnetic heads HD11to HD16), and output and supply the amplified signal to the first SoC100. In the first SoC100, the signal supplied from the head amplifier140is demodulated into digital data by a read channel circuit (not illustrated).

In addition, a signal corresponding to the digital data is supplied from the first SoC100to the head amplifier140. The head amplifier140amplifies the signal supplied from the first SoC100and supply the amplified signal to the magnetic heads HD11to HD16(more specifically, write elements401provided in the magnetic heads HD11to HD16). The write element401having received the signal records the signal on the recording surface of the magnetic disk300.

In addition, the head amplifier140detects touchdowns of the magnetic heads HD11to HD16in response to an instruction from the first SoC100.

The head amplifier240amplifies a signal, read from the magnetic disk300by the magnetic heads HD21to HD26(more specifically, read elements402provided in the magnetic heads HD21to HD26), and output and supply the amplified signal to the second SoC200. In the second SoC200, the signal supplied from the head amplifier240is demodulated into digital data by a read channel circuit (not illustrated).

In addition, a signal corresponding to the digital data is supplied from the second SoC200to the head amplifier240. The head amplifier240amplifies the signal supplied from the second SoC200and supply the amplified signal to the magnetic heads HD21to HD26(more specifically, write elements401provided in the magnetic heads HD21to HD26). The write element401having received the signal records the signal on the recording surface of the magnetic disk300.

In addition, the head amplifier240detects touchdowns of the magnetic heads HD21to HD26in response to an instruction from the second SoC200.

The SVC150drives the first actuator system110based on an instruction from the first SoC100. Specifically, the SVC150drives the first actuator system110to position the magnetic head HD to be used among the magnetic heads HD11to HD16at a position instructed by the first SoC100.

In addition, the SVC150also drives the SPM310based on an instruction from the first SoC100. The SVC150drives the SPM310such that a rotational speed of the SPM310is constant at a predetermined target speed.

The SVC250drives the second actuator system210based on an instruction from the second SoC200. Specifically, the SVC250drives the second actuator system210to position the magnetic head HD to be used among the magnetic heads HD21to HD26at a position instructed by the second SoC200.

The first SoC100is connected to the host2. The first SoC100interprets an access command from the host2and executes control to perform an operation based on the interpretation result, such as accessing the magnetic disk300.

The first SoC100includes a first central processing unit (CPU)101and a second CPU102. The first CPU101and the second CPU102operate according to a firmware program. The firmware program is stored in a predetermined non-volatile storage area. The predetermined non-volatile storage area may be the magnetic disk300or a read only memory (ROM) (not illustrated).

The first CPU101controls the overall operation of the magnetic disk device1together with the first CPU201provided in the second SoC200. The first CPU101sends various instructions to the second CPU102as a part of control of the overall operation of the magnetic disk device1. The various instructions from the first CPU101to the second CPU102include a rotation control instruction of the SPM310, a load/unload instruction of the first actuator system110, a touchdown measurement instruction for the first actuator system110, and the like. In addition, the various instructions from the first CPU101to the second CPU102include an instruction for accessing the magnetic disk300via the magnetic heads HD11to HD16.

The second CPU102executes an operation instructed by the first CPU101. The second CPU102controls the head amplifier140, the SVC150, or the both in order to implement the instructed operation.

The second SoC200includes a first CPU201and a second CPU202. The first CPU201and the second CPU202operate according to a firmware program. The firmware program is stored in a predetermined non-volatile storage area. The predetermined non-volatile storage area may be a magnetic disk300or a ROM (not illustrated).

The first CPU201controls the overall operation of the magnetic disk device1together with the first CPU101provided in the first SoC100. The first CPU201sends various instructions to the second CPU202as a part of control of the overall operation of the magnetic disk device1. The various instructions from the first CPU201to the second CPU202include a load/unload instruction of the second actuator system210, a touchdown measurement instruction using the second actuator system210, and the like. In addition, the various instructions from the first CPU201to the second CPU202include an instruction for accessing the magnetic disk300via the magnetic heads HD21to HD26.

The second CPU202executes an operation instructed by the first CPU201. The second CPU202controls the head amplifier240, the SVC250, or the both in order to implement the instructed operation.

Note that the first SoC100and the second SoC200are examples of a controller in the claims. One of the first SoC100and the second SoC200is an example of a first controller chip in the claims. The other one of the first SoC100and the second SoC200is an example of a second controller chip in the claims. An actuator system controlled by the first controller chip among the actuator systems110and210is an example of a first actuator system in the claims. An actuator system controlled by the second controller chip among the actuator systems110and210is an example of a second actuator system in the claims.

Hereinafter, a description will be given assuming that the first SoC100is the first controller chip, the second SoC200is the second controller chip, the first actuator system110is the first actuator system, and the second actuator system210is the second actuator system.

Subsequently, a configuration of the magnetic head HD according to the embodiment will be described.FIG. 3is a view illustrating the configuration of the magnetic head HD according to the embodiment as viewed from the recording surface side of the magnetic disk300.FIG. 4is a cross-sectional view of the magnetic head HD according to the embodiment cut along an extending direction of the suspension130.

As illustrated inFIGS. 3 and 4, the magnetic head HD includes the write element401, the read element402, a head-disk interface (HDI) sensor403, and a heater404.

The write element401records data on the recording surface of the magnetic disk300by a magnetic field generated from a magnetic pole thereof. The read element402reads a change in the magnetic field on the magnetic disk300as data to read the data recorded on the magnetic disk300.

The HDI sensor403includes a resistive element (not illustrated). With this resistive element, it is possible to detect the contact between the magnetic head HD and the magnetic disk300. More specifically, when the magnetic head HD comes into contact with the magnetic disk300, the HDI sensor403undergoes a thermal change due to the influence of frictional heat at the time of the contact therebetween. As a result, a resistance value of the resistive element changes. As the change in the resistance value of the resistive element is detected by the head amplifiers140or240, the contact between the magnetic head HD and the magnetic disk300is detected.

The heater404is supplied with power from the head amplifiers140or240to heat the magnetic head HD. Since the magnetic head HD is thermally deformed by this heating, a flying height F of the magnetic head HD from the magnetic disk300changes. More specifically, the thermal expansion of the magnetic head HD increases as the power supplied to the heater404increases, which reduces the flying height F.

During touchdown measurement, the power supplied to the heater404is gradually increased under the control of the head amplifiers140or240by the second CPUs102or202. The magnetic head HD expands as the power supplied to the heater404increases, which reduces the flying height F. Further, when the flying height F becomes zero, the contact between the magnetic head HD and the magnetic disk300is detected by the head amplifiers140or240based on the change in the resistance value of the resistive element of the HDI sensor403. That is, the touchdown is detected. The second CPUs102or202record the power supplied to the heater404when the touchdown is detected. As a result, the touchdown measurement for one magnetic head HD ends.

In other words, the touchdown measurement is to measure the power supplied to the heater404, which is required to cause a touchdown (a state where the magnetic head HD and the magnetic disk300are in contact with each other). After the touchdown measurement, the power supplied to the heater404is controlled with a power value acquired by the touchdown measurement as a reference (reference power) when the magnetic head HD is used to access the recording surface of the magnetic disk300. If the touchdown can be detected with high accuracy, the accuracy of the reference power is improved, and thus, the accuracy of control of the flying height F is improved.

The touchdown measurement is executed for each of the 12 magnetic heads HD.

As described above, the touchdown measurement involves the contact between the magnetic head HD and the magnetic disk300. Due to the contact between the magnetic head HD and the magnetic disk300, a disturbance is applied to the rotation of the magnetic disk300.

The magnetic head HD is levitated by a lift force generated by the relative speed between the magnetic disk300and the magnetic head HD. That is, the flying height F of the magnetic head HD is affected by a rotational speed of the magnetic disk300. Accordingly, if the touchdown measurement is performed for another magnetic head HD in a state where the disturbance is applied to the rotation of the magnetic disk300, the flying height F of the other magnetic head HD fluctuates due to the disturbance applied to the rotation of the magnetic disk300, and thus, the touchdown detection accuracy of the other magnetic head HD deteriorates. As a result, it is difficult to accurately measure a reference power applied to the other magnetic head HD.

Therefore, touchdown measurement for the six magnetic heads HD are individually and sequentially performed in one actuator system between the two actuator systems110and210in the embodiment. When the touchdown measurement for all the magnetic heads HD in the one actuator system is completed, the touchdown measurement of the six magnetic heads HD are individually and sequentially performed in the other actuator system between the two actuator systems110and210.

Accordingly, touchdowns of two magnetic heads HD are prevented from occurring at the same time, and thus, the touchdown detection accuracy of each magnetic head HD is improved.

The first CPU101and the first CPU201are electrically connected such that communication between the first CPU101and the first CPU201is possible in order to control a touchdown measurement timing for each of the actuator systems110and210.

FIG. 5is a schematic view for describing a connection example according to the embodiment between the first CPU101and the first CPU201. Each of the first CPU101and the first CPU201has two ports P1and P2. Each of the ports P1and P2is a terminal configured to transmit and receive a 1-bit signal as an example here.

The port P1(referred to as a port P1o) provided in the first CPU101is connected to the port P1(referred to as a port P1i) provided in the first CPU201. The first CPU101transmits a 1-bit signal to the first CPU201via the port P1o. The port P1iprovided in the first CPU201includes a latch circuit (not illustrated), and takes (in other words, latch) the 1-bit signal output from the port P1oof the first CPU101.

The port P2(referred to as a port P2i) provided in the first CPU101is connected to the port P2(port P2o) provided in the first CPU201. The first CPU201transmits a 1-bit signal to the first CPU101via the port P2o. The port P2iprovided in the first CPU101includes a latch circuit (not illustrated), and takes the 1-bit signal output from the port P2oof the first CPU201.

In this manner, the signal from the first CPU101to the first CPU201is transferred via the port P1provided in each of the first CPUs101and201, and the signal from the first CPU201to the first CPU101is transferred via the port P2provided in each of the first CPUs101and201.

The first CPUs101and201transmit and receive the signals using the two ports P1and P2to control the touchdown measurement timing.

FIG. 6is a flowchart for describing an example of an operation related to the touchdown measurement in the magnetic disk device1according to the embodiment.

First, in the first SoC100, the first CPU101instructs the second CPU102to control the rotation of the SPM310(S101). Specifically, the first CPU101instructs the second CPU102to control the rotation of the SPM310. The second CPU102uses the SVC150to execute speed control for accelerating the rotational speed of the SPM310to a target speed in response to the instruction from the first CPU101.

When the rotational speed of the SPM310reaches the target speed, the rotation control of the SPM310is completed (S102). Thereafter, the second CPU102uses the SVC150to execute control such that the rotational speed of the SPM310is constant at the target speed.

When the rotational speed of the SPM310reaches the target speed, it is possible to load the actuator systems110and210(more accurately, load the 12 magnetic heads HD connected to the actuator systems110and210). The first CPU101notifies the first CPU201that loading of the second actuator system210becomes possible by communication via the port P1.

Specifically, in the second SoC200, the first CPU201starts monitoring the content of the latch circuit of the port P1iafter the start. The first CPU201repeats the determination on whether the latch circuit of the port P1ihas taken an H-level signal (S201) until the latch circuit of the port P1itakes the H-level signal (S201: No).

The first SoC100sets a signal level of the port P1ofrom an L level to the H level (S103), and then, clears the signal level of the port P1oto the L level (S104).

In the second SoC200, the H-level signal is taken into the latch circuit of the port P1iaccording to the processing of S103, and the first CPU201determines that the latch circuit of the port P1ihas taken the H-level signal (S201: Yes). As a result, the first CPU201can recognize that loading of the second actuator system210becomes possible. When determining that the latch circuit of the port P1ihas taken the H-level signal (S201: Yes), the first CPU201clears the content of the latch circuit of the port P1ito the L level (S202).

In this manner, after the rotation control of the SPM310is completed, the first CPU101notifies the first CPU201that loading of the second actuator system210becomes possible by the first communication using the port P1.

In the first SoC100, the first CPU101instructs the second CPU102to load the first actuator system110(S105). The second CPU102uses the SVC150to control the VCM111in response to the instruction from the first CPU101, thereby loading the first actuator system110. As a result, the magnetic heads HD11to HD16are moved from the ramp load mechanism340onto the recording surfaces of the magnetic disks300-4,300-5, and300-6.

When the loading of the first actuator system110is completed (S106), the first CPU101waits for the completion of loading of the second actuator system210.

In the second SoC200, the first CPU201instructs the second CPU202to load the second actuator system210(S203). The second CPU202uses the SVC250to control the VCM211in response to the instruction from the first CPU201, thereby loading the second actuator system210. As a result, the magnetic heads HD21to HD26are moved from the ramp load mechanism340onto the recording surfaces of the magnetic disks300-1,300-2, and300-3.

When the loading of the second actuator system210is completed (S204), the first CPU201notifies the first CPU101that the loading of the second actuator system210has been completed by communication via the port P2.

Specifically, in the first SoC100, the monitoring of the content of the latch circuit of the port P2iis started after the processing of S106. That is, the first CPU101repeats the determination on whether the latch circuit of the port P2ihas taken the H-level signal (S107) until the latch circuit of the port P2itakes the H-level signal (S107: No).

In the second SoC200, after the processing of S204, the first CPU201sets a signal level of the port P2ofrom the L level to the H level (S205), and then, clears the signal level of the port P2oto the L level (S206).

In the first SoC100, the H-level signal is taken into the latch circuit of the port P2iaccording to the processing of S205, and the first CPU101determines that the latch circuit of the port P2ihas taken the H-level signal (S107: Yes). As a result, the first CPU101can recognize that the loading of the second actuator system210has been completed. When determining that the latch circuit of the port P2ihas taken the H-level signal (S107: Yes), the first CPU101clears the content of the latch circuit of the port P2ito the L level (S108).

In this manner, the first CPU201notifies the first CPU101that the loading of the second actuator system210has been completed by the first communication using the port P2.

Subsequently, the touchdown measurement is executed. In this example, first, the touchdown measurement for the first actuator system110is executed. Note that a configuration may be adopted in which the touchdown measurement for the second actuator system210is executed prior to the touchdown measurement for the first actuator system110.

The first CPU101instructs the second CPU102to execute the touchdown measurement for the first actuator system110(S109). The second CPU102sequentially controls the six magnetic heads HD11to HD16using the head amplifier140in response to the instructions from the first CPU101, thereby serially executes the touchdown measurement on the six magnetic heads HD11to HD16.

When the touchdown measurement for the first actuator system110is completed (S110), the first CPU101notifies the first CPU201that the touchdown measurement can be started by communication via the port P1.

Specifically, in the second SoC200, the first CPU201starts monitoring the content of the latch circuit of the port P1iafter the processing of S206. That is, the first CPU201repeats the determination on whether the latch circuit of the port P1ihas taken the H-level signal (S207) until the latch circuit of the port P1itakes the H-level signal (S207: No).

In the first SoC100, the first CPU101sets a signal level of the port P1ofrom the L level to the H level (S111), and then, clears the signal level of the port P1oto the L level (S112).

In the second SoC200, the H-level signal is taken into the latch circuit of the port P1iaccording to the processing of S111, and the first CPU201determines that the latch circuit of the port P1ihas taken the H-level signal (S207: Yes). As a result, the first CPU201can recognize that loading of the touchdown measurement becomes possible. When determining that the latch circuit of the port P1ihas taken the H-level signal (S207: Yes), the first CPU201clears the content of the latch circuit of the port P1ito the L level (S208).

In this manner, the first CPU101notifies the first CPU201that the touchdown measurement for the second actuator system210becomes possible by the second communication using the port P1.

After notifying that the touchdown measurement for the second actuator system210becomes possible, the first CPU101waits for the completion of the touchdown measurement for the second actuator system210.

In the second SoC200, the first CPU201instructs the second CPU202to execute the touchdown measurement for the second actuator system210(S209). The second CPU202sequentially controls the six magnetic heads HD21to HD26using the head amplifier240in response to the instructions from the first CPU201, thereby serially executes the touchdown measurement on the six magnetic heads HD21to HD26.

When the touchdown measurement for all the magnetic heads HD connected to the second actuator system210is completed (S210), the first CPU201notifies the first CPU101that the touchdown measurement has been completed by communication via the port P2.

Specifically, in the first SoC100, the first CPU101starts monitoring the content of the latch circuit of the port P2iafter the processing of S112. That is, the first CPU101repeats the determination on whether the latch circuit of the port P2ihas taken the H-level signal (S113) until the latch circuit of the port P2itakes the H-level signal (S113: No).

In the second SoC200, after the processing of S210, the first CPU201sets a signal level of the port P2ofrom the L level to the H level (S211), and then, clears the signal level of the port P2oto the L level (S212).

In the first SoC100, the H-level signal is taken into the latch circuit of the port P2iaccording to the processing of S211, and the first CPU101determines that the latch circuit of the port P2ihas taken the H-level signal (S113: Yes). As a result, the first CPU101can recognize that the touchdown measurement for the second actuator system210has been completed. When determining that the latch circuit of the port P2ihas taken the H-level signal (S113: Yes), the first CPU101clears the content of the latch circuit of the port P2ito the L level (S114).

In this manner, the first CPU201notifies the first CPU101that the touchdown measurement for the second actuator system210has been completed by the second communication using the port P2.

When the touchdown measurement for the actuator systems110and210is completed, the actuator systems110and210are unloaded.

In the first SoC100, the first CPU101instructs the second CPU102to unload the first actuator system110(S115). The second CPU102uses the SVC150to control the VCM111in response to the instruction from the first CPU101, thereby unloading the first actuator system110. As a result, the magnetic heads HD11to HD16are retracted to the ramp load mechanism340. When the unloading of the first actuator system110is completed (S116), the operation of the first CPU101related to the touchdown measurement ends.

In the second SoC200, the first CPU201instructs the second CPU202to unload the second actuator system210(S213). The second CPU202uses the SVC250to control the VCM211in response to the instruction from the first CPU201, thereby unloading the second actuator system210. As a result, the magnetic heads HD21to HD26are retracted to the ramp load mechanism340. When the unloading of the second actuator system210is completed (S214), the operation of the second CPU202related to the touchdown measurement ends.

FIG. 7is a flowchart for describing details of a touchdown measurement operation in each of the actuator systems110and210according to the embodiment.

In each of the actuator systems110and210, the same operation is performed except that the CPUs that execute control, the head amplifiers used for the control, and the magnetic heads HD to be controlled are different from each other. Here, as a representative, the touchdown measurement operation in the first actuator system110will be described.

First, the second CPU102uses the head amplifier140to execute touchdown measurement of the first magnetic head HD among the six magnetic heads HD11to HD16(S301). The first magnetic head HD can be arbitrarily determined by a designer.

In the S301, the second CPU102uses the head amplifier140to start supplying power to the heater404of the first magnetic head HD, and gradually increases the supplied power. When a touchdown of the first magnetic head HD occurs, the head amplifier140detects the touchdown based on a signal from the HDI sensor403. The head amplifier140notifies the second CPU102that the touchdown has been detected. The second CPU102records the power supplied to the heater404at the timing when the touchdown has been detected as reference power applied to the first magnetic head HD. Further, the second CPU102stops the supply of power to the heater404.

When the touchdown measurement of the first magnetic head HD, that is, the acquisition of the reference power applied to the first magnetic head HD, is completed (S302), the second CPU102executes touchdown measurement of the second magnetic head HD among the six magnetic heads HD11to HD16(S303). The touchdown measurement of the second magnetic head HD is performed in the same procedure as the touchdown measurement of the first magnetic head HD.

When the touchdown measurement of the second magnetic head HD, that is, the acquisition of the reference power applied to the second magnetic head HD, is completed (S304), the second CPU102executes touchdown measurement of the third magnetic head HD among the six magnetic heads HD11to HD16(S305). The touchdown measurement of the third magnetic head HD is performed in the same procedure as the touchdown measurement of the first magnetic head HD.

When the touchdown measurement of the third magnetic head HD is completed (S306), touchdown measurement for the fourth, fifth, and sixth magnetic heads HD are executed sequentially and serially in the same procedure as the touchdown measurement of the first magnetic head HD in the subsequent S307to S312.

When the touchdown measurement of the sixth magnetic head HD is completed (S312), the touchdown measurement in the first actuator system110is completed.

The touchdown measurement of each magnetic head HD is executed using the signal from the HDI sensor403as above. A method of the touchdown measurement is not limited thereto. For example, as disclosed in Japanese Patent Application Laid-Open No. 2008-186564, a method of detecting a touchdown based on an error rate of data read from the magnetic disk300is applicable to the embodiment.

In addition, a communication method between the first CPU101and the first CPU201is not limited only to the method using the ports P1and P2. A memory may be arranged between the first CPU101and the first CPU201to transmit and receive information between the first CPU101and the first CPU201via the memory. In addition, the first CPU101and the first CPU201may be connected by a communication line capable of transmitting and receiving a signal in both directions to perform communication via the communication line.

In addition, the case where both the actuator systems110and210are configured to be rotatable about the same rotary shaft320has been described above. The embodiment is also applicable to a magnetic disk device in which the actuator systems110and210are configured to be rotatable about different rotary shafts320-1and320-2, for example, as illustrated inFIG. 8. In the example illustrated inFIG. 8, a magnetic head HD of the first actuator system110is unloaded to a ramp load mechanism340-1, and a magnetic head HD of the second actuator system210is unloaded to a ramp load mechanism340-2.

In addition, the number of the magnetic disks300provided in the magnetic disk device1is not limited to six.

In addition, the number of the magnetic heads HD provided in the magnetic disk device1is not limited to twelve. For example, the magnetic disk device1can include one or more magnetic heads HD which are moved by the first actuator system110, and one or more magnetic heads HD which are moved by the second actuator system210.

In addition, the number of the actuator systems provided in the magnetic disk device1is not limited to two. When the magnetic disk device1has three or more actuator systems, at least two of the three or more actuator systems can function as a pair of the first actuator system and the second actuator system according to the embodiment.

As described above, according to the embodiment, the first SoC100and the second SoC200, which serve as the controller, execute control together such that the touchdown measurement, more specifically, the touchdown detection, of the first actuator system110and the touchdown measurement, more specifically, the touchdown detection, of the second actuator system210are executed at different timings. Further, the first SoC100and the second SoC200, which serve as the controller, execute control such that touchdowns of the respective magnetic heads HD moved by the first actuator system110are measured at different timings in the touchdown measurement for the first actuator system110. In addition, the first SoC100and the second SoC200, which serve as the controller, execute control such that touchdowns of the respective magnetic heads HD moved by the second actuator system210are measured at different timings in the touchdown measurement for the second actuator system210.

As a result, touchdowns of two magnetic heads HD are prevented from occurring at the same time, and thus, the touchdown detection accuracy of each magnetic head HD is improved.

In addition, according to the embodiment, the first SoC100executes the touchdown measurement for all the magnetic heads HD moved by the first actuator system110. Further, the second SoC200executes the touchdown measurement for all the magnetic head HD moved by the second actuator system210after the touchdown measurement for all the magnetic heads HD moved by the first actuator system110is completed.

As a result, touchdowns of two magnetic heads HD are prevented from occurring at the same time, and thus, the touchdown detection accuracy of each magnetic head HD is improved.

Note that the touchdown measurement of the magnetic head HD moved by the first actuator system110and the touchdown measurement of the magnetic head HD moved by the second actuator system210may be executed alternately in units of magnetic head HD. In such a case, it becomes necessary for each of the first CPU101and the second CPU201to transmit and receive a notification to control the touchdown measurement timing each time the touchdown measurement of one magnetic head HD is completed between the first CPU101and the second CPU201.

In the embodiment, the touchdown measurement for all the magnetic heads HD moved by the second actuator system210is executed after the touchdown measurement for all the magnetic heads HD moved by the first actuator system110is completed. Accordingly, the number of times of transmitting and receiving the notification to control the touchdown measurement timing is only twice. In the example illustrated inFIG. 6, the notification is transmitted and received by the processing of S111and the processing of S211.

In addition, according to the embodiment, the first SoC100and the second SoC200, which serve as the controller, execute control such that the touchdown measurement is executed in the state where the actuator systems110and210are loaded together.

When the actuator systems are loaded, the windage loss of the SPM310increases as the magnetic head HD faces the recording surface of the magnetic disk300. As a result, the power consumption of the SPM310increases. Therefore, for example, by unloading one of the actuator systems110and210when the touchdown measurement is being executed in the other of the actuator systems110and210, the power consumption of the SPM310can be reduced.

On the other hand, the windage loss of the SPM310caused by the loading of the actuator system gives a static disturbance to the rotation of the magnetic disk300.

In the actual magnetic disk device1, a use case is assumed in which the two actuator systems110and210are used in parallel to access the magnetic disk300. Since the two actuator systems110and210are used in parallel, the number of accesses to the magnetic disk300per unit time can be improved as compared to a case where the actuator systems110and210are used exclusively.

In the above use case, the actuator systems110and210are used in the loaded state, and thus, a larger disturbance is applied to the rotation of the magnetic disk300as compared to a case where only one of the actuator systems110and210is loaded. That is, the flying height F of each magnetic head HD is controlled in a state where the large disturbance due to the actuator systems110and210being loaded together is applied to the rotation of the magnetic disk300.

In the embodiment, the touchdown measurement is executed in the state where the actuator systems110and210are loaded together. That is, the touchdown measurement is executed under the most unfavorable condition within the range of assumed disturbance conditions. As a result, the magnetic disk device1uses the two actuator systems110and210in parallel to access the magnetic disk300so that it is possible to accurately control the flying height F even when the disturbance conditions deteriorate.

Note that the first SoC100and the second SoC200, which serve as the controller, may execute control such that the touchdown measurement for one of the actuator systems110and210is executed while executing seek control using the other of the actuator systems110and210in order to execute the touchdown measurement under an even more unfavorable condition within the range of assumed disturbance conditions.

In addition, in the above description, the first SoC100and the second SoC200, which serve as the controller, execute unloading of the actuator systems110and210after the touchdown measurement for all the magnetic heads HD moved by the first actuator system110and the touchdown measurement for all the magnetic heads HD moved by the second actuator system210are completed. The controller may be configured to unload the actuator system110, and then, unload the actuator system210. In such a case, the first SoC100unloads the actuator system110, and sends a notification to the second SoC200in the same procedure as S103, S104, S201, S202, and the like after the unloading of the actuator system110is completed. When receiving the notification, the second SoC200starts unloading the actuator system210. Note that the unloading order is not limited thereto.

The controller may be configured to load the actuator system110, and then, load the actuator system210similarly to unloading. In such a case, the first SoC100loads the actuator system110, and sends a notification to the second SoC200in the same procedure as S103, S104, S201, S202, and the like after the loading of the actuator system110is completed. When receiving the notification, the second SoC200starts loading the actuator system210. Note that the loading order is not limited thereto.

Since the loading/unloading of the actuator systems110and210are executed at different timings between the actuator systems as described above, it is possible to suppress the disturbance caused by loading/unloading. In addition, it is possible to reduce a vibration or an impact generated in the magnetic disk device1by loading/unloading. For example, in a manufacturing plant of the magnetic disk device1or a data center using the magnetic disk device1, a plurality of the magnetic disk devices1are operated in a state where the plurality of magnetic disk devices1are housed in a pallet. In such a case, the vibration or impact generated in each of the magnetic disk devices1affects the operation of other magnetic disk device1. Since the vibration or impact generated in each of the magnetic disk devices1can be reduced by executing the loading/unloading of the actuator systems110and210at different timings, it is possible to reduce the influence of each of the magnetic disk devices1on the operation of the other magnetic disk device1.