1. A magnetic disk drive that adopts a data-surface servo system, said magnetic disk drive comprising:
a magnetic disk including a main preamble that is written at a frequency of a data clock;
a write channel for writing a plurality of data sectors each including a sub preamble and user data, with a write clock that is synchronized with a signal obtained by reading the main preamble; and
a read channel for, when any of the plurality of written data sectors is read, generating a read clock by use of the signal obtained by reading the main preamble and a signal obtained by reading the sub preamble included in a data sector to be read,
wherein:
a bit length of the sub preamble becomes longer with the increase in distance between the data sector and the main preamble.
2. The magnetic disk drive according to claim 1, wherein:
only one said main preamble is located in each data area.
3. The magnetic disk drive according to claim 2, wherein:
said main preamble is located at a position adjacent to a preceding servo sector thereof.
4. The magnetic disk drive according to claim 1, wherein:
said magnetic disk drive adopts a zone-bit recording method, and the main preamble is written at a frequency of a data clock set in each zone of a plurality of zones arranged radially on the magnetic disk.
5. The magnetic disk drive according to claim 1, wherein:
said servo sector is written from the innermost radius side towards the outermost radius side of the magnetic disk at the same frequency, and a write frequency of the servo sector differs from a write frequency of the data clock.
6. A magnetic disk drive that adopts a data-surface servo system, said magnetic disk drive comprising:
a magnetic disk including a main preamble that is written at a frequency of a data clock;
a write channel for writing a plurality of data sectors each including a sub preamble and user data, with a write clock that is synchronized with a signal obtained by reading the main preamble; and
a read channel for, when any of the plurality of written data sectors is read, generating a read clock by use of the signal obtained by reading the main preamble and a signal obtained by reading the sub preamble included in a data sector to be read,
wherein:
at the time of writing the data sector, said write channel generates the write clock by use of the signal obtained by reading the main preamble and a signal obtaining by reading the preceding data sector of a data sector to be written.
7. The magnetic disk drive according to claim 6, wherein:
a bit length of said each sub preamble included in each of the plurality of written data sectors is the same as the bit length of the sub preambles included in the other written data sectors.
8. The magnetic disk drive according to claim 7, wherein:
the bit length of the main preamble is sufficient for independently reading the user data, and is longer than the bit length of the sub preamble.
9. The magnetic disk drive according to claim 7, wherein:
a ratio of the bit length of the sub preamble to the bit length of the main preamble ranges from about 10% to 40%.
10. A magnetic disk drive that adopts a data-surface servo system, said magnetic disk drive comprising:
a magnetic disk including a main preamble that is written at a frequency of a data clock;
a write channel for writing a plurality of data sectors each including a sub preamble and user data, with a write clock that is synchronized with a signal obtained by reading the main preamble; and
a read channel for, when any of the plurality of written data sectors is read, generating a read clock by use of the signal obtained by reading the main preamble and a signal obtained by reading the sub preamble included in a data sector to be read,
wherein:
at the time of reading the written data sector, said read channel generates the read clock by use of the signal obtained by reading the main preamble, a signal obtained by reading the preceding data sector of a data sector to be read, and a signal obtained by reading the sub preamble included in the data sector to be read.
11. A method for writing and reading user data in a magnetic disk drive that adopts a data-surface servo system, said method comprising:
providing a magnetic disk in which at a frequency of a data clock, a main preamble is written to each data area formed between servo sectors, after servo data are written and before shipment of the magnetic disk drive;
writing a plurality of data sectors each including the sub preamble and user data, to said each data area with a write clock that is synchronized with a read signal of the main preamble;
performing synchronous operation of a read channel while reading the main preamble; and
performing, subsequent to performing the synchronous operation, synchronous operation of the read channel while reading the sub preamble of a data sector selected from among the plurality of written data sectors.
12. A writing and reading method according to claim 11, wherein:
providing the magnetic disk includes writing the main preamble to the magnetic disk before the magnetic disk drive is shipped.
13. A writing and reading method according to claim 11, wherein:
providing the magnetic disk includes writing the main preamble at a position adjacent to each preceding servo sector in all data areas formed between the servo sectors.
14. A method for writing and reading user data in a magnetic disk drive that adopts a data-surface servo system, said method comprising:
providing a magnetic disk in which at a frequency of a data clock, a main preamble is written to each data area formed between servo sectors;
writing a plurality of data sectors each including the sub preamble and user data, to said each data area with a write clock that is synchronized with a read signal of the main preamble;
performing synchronous operation of a read channel while reading the main preamble; and
performing, subsequent to performing the synchronous operation, synchronous operation of the read channel while reading the sub preamble of a data sector selected from among the plurality of written data sectors,
wherein:
writing the data sectors includes generating the write clock by use of a signal obtained by reading the main preamble and a signal obtained by reading the preceding data sector of the data sector to be written.
15. A method for writing and reading user data in a magnetic disk drive that adopts a data-surface servo system, said method comprising:
providing a magnetic disk in which at a frequency of a data clock, a main preamble is written to each data area formed between servo sectors;
writing a plurality of data sectors each including the sub preamble and user data, to said each data area with a write clock that is synchronized with a read signal of the main preamble;
performing synchronous operation of a read channel while reading the main preamble; and
performing, subsequent to performing the synchronous operation, synchronous operation of the read channel while reading the sub preamble of a data sector selected from among the plurality of written data sectors,
wherein:
reading the data sector includes generating the read clock by use of the signal obtained by reading the main preamble, a signal obtained by reading the preceding data sector of the data sector to be read, and a signal obtained by reading the sub preamble included in the data sector to be read.
16. A magnetic disk drive that adopts a data-surface servo system, said magnetic disk drive comprising:
a magnetic disk including a common preamble that is written at a frequency of a data clock;
a write channel for writing a plurality of data sectors with a write clock that is synchronized with a signal obtained by reading the common preamble; and
a read channel for, when any of the plurality of written data sectors is read, synchronizing a read clock with a signal obtained by reading the common preamble,
wherein:
said common preamble is written at a position adjacent to the preceding servo sector thereof; and
at the time of writing the data sector, said write channel generates the write clock by use of a read signal of the common preamble, and a read signal of the preceding data sector of the data sector to be written.
17. A magnetic disk drive that adopts a data-surface servo system, said magnetic disk drive comprising:
a magnetic disk including a common preamble that is written at a frequency of a data clock;
a write channel for writing a plurality of data sectors with a write clock that is synchronized with a signal obtained by reading the common preamble; and
a read channel for, when any of the plurality of written data sectors is read, synchronizing a read clock with a signal obtained by reading the common preamble,
wherein:
said common preamble is written at a position adjacent to the preceding servo sector thereof; and
at the time of reading the written data sector, said read channel generates the read clock by use of the common preamble, and a read signal of the preceding data sector of the data sector to be read.
18. The magnetic disk drive according to claim 16, wherein:
the top of data in each one of said data sectors is a SYNC pattern.
19. The magnetic disk drive according to claim 17, wherein:
the top of data in each one of said data sectors is a SYNC pattern.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method of controlling an operation mode of a fuel cell in a fuel cell vehicle, comprising:
determining by a controller a first torque and a first state of charge (SOC) corresponding to a stop mode torque value and a stop mode SOC value, and determining by a controller a second torque and a second SOC corresponding to a start mode torque value and a start more SOC value, wherein the second torque is higher than the first torque and the second SOC is lower than the first SOC;
when a driver-demanded torque is lower than the first torque, and a current SOC in a battery is higher than the first SOC, converting by the controller the operation mode of the fuel cell to a stop mode; and
when the driver-demanded torque is higher than the second torque, or the current SOC in the battery is lower than the second SOC, converting by the controller the operation mode of the fuel cell to a start mode,
wherein the first torque is increased to more quickly convert the operation mode to the stop mode or the second torque is reduced to more quickly convert the operation mode to the start mode according to driving state of the fuel cell vehicle.
2. The method according to claim 1, wherein during the stop mode and when the stop mode is not yet terminated, the stop mode is interrupted when the driver-demanded torque becomes higher than a third torque or the current SOC becomes lower than a third SOC, wherein the third torque is a predetermined torque ranging between the first and second torques, and the third SOC is a predetermined SOC ranging between the first and second SOCs.
3. The method of claim 1 wherein the first torque is increased to more quickly convert the operation mode to the stop mode.
4. The method of claim 1 wherein the second torque is reduced to more quickly convert the operation mode to the start mode according to driving state of the fuel cell vehicle.
5. The method according to claim 1, wherein as speed of the fuel cell vehicle is increased, the second torque is reduced to more quickly convert the operation mode to the start mode.
6. The method according to claim 1, wherein as available output voltage of the fuel cell is decreased, the second torque is reduced to more quickly convert the operation mode to the start mode.
7. The method according to claim 1, wherein the operation mode is converted to the start mode when the driver-demanded torque is higher than the second torque, when the current SOC is lower than the second SOC, or when a vehicle speed is equal to or higher than a predetermined speed and a voltage across both poles of the fuel cell is equal to or lower than a predetermined voltage.
8. The method according to claim 1, wherein during the start mode, the operation mode is not converted to the stop mode until the start mode has been maintained for at least a predetermined period of time.
9. A non-transitory computer readable medium containing program instructions executed by a controller, the computer readable medium comprising:
program instructions that determining a first torque, a first state of charge (SOC), a second torque and a second SOC of a fuel cell in a fuel cell vehicle;
program instructions that compare a driver-demanded torque to the first torque and that compare a current SOC to the first SOC;
program instructions that convert an operation mode of the fuel cell to a stop mode when the driver-demanded torque is lower than the first torque, and when the current SOC is higher than the first SOC;
program instructions that compare a driver-demanded torque to the second torque and a current SOC to the second SOC;
program instructions that convert the operation mode of the fuel cell to a start mode when the driver-demanded torque is higher than the second torque, and when the current SOC is lower than the second SOC; and
program instructions that determine when the fuel cell vehicle is in a regenerative braking state, a downhill driving state, an idle state, a rapid acceleration state, or a state of decrease in available output voltage;
program instructions that reduce the first SOC when the fuel cell is in the regenerative braking state;
program instructions that increase the first torque when the fuel cell is in the downhill driving state;
program instructions that increase the first torque when the fuel cell is in at least a portion of the idle state;
program instructions that reduce the second torque as speed of the fuel cell is increased; and
program instructions that reduce the second torque as available output voltage of the fuel cell is decreased.