WO2002059893A2 - Spin motor control in an optical drive - Google Patents
Spin motor control in an optical drive Download PDFInfo
- Publication number
- WO2002059893A2 WO2002059893A2 PCT/US2002/001841 US0201841W WO02059893A2 WO 2002059893 A2 WO2002059893 A2 WO 2002059893A2 US 0201841 W US0201841 W US 0201841W WO 02059893 A2 WO02059893 A2 WO 02059893A2
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- Prior art keywords
- spin
- motor
- period
- rpm
- module
- Prior art date
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Classifications
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B19/00—Driving, starting, stopping record carriers not specifically of filamentary or web form, or of supports therefor; Control thereof; Control of operating function ; Driving both disc and head
- G11B19/20—Driving; Starting; Stopping; Control thereof
- G11B19/24—Arrangements for providing constant relative speed between record carrier and head
- G11B19/247—Arrangements for providing constant relative speed between record carrier and head using electrical means
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B19/00—Driving, starting, stopping record carriers not specifically of filamentary or web form, or of supports therefor; Control thereof; Control of operating function ; Driving both disc and head
- G11B19/20—Driving; Starting; Stopping; Control thereof
- G11B19/28—Speed controlling, regulating, or indicating
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
- G11B7/085—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam into, or out of, its operative position or across tracks, otherwise than during the transducing operation, e.g. for adjustment or preliminary positioning or track change or selection
- G11B7/08505—Methods for track change, selection or preliminary positioning by moving the head
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
- G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
- G11B7/0938—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following servo format, e.g. guide tracks, pilot signals
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
- G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
- G11B7/0948—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following specially adapted for detection and avoidance or compensation of imperfections on the carrier, e.g. dust, scratches, dropouts
Definitions
- the present invention relates to an optical disk system and, in particular, to a servo system for controlling and monitoring the operation of an optical disk spin motor control system.
- optical system typically includes a laser or other optical source, focusing lenses, reflectors, optical detectors, and other components.
- a laser or other optical source typically includes focusing lenses, reflectors, optical detectors, and other components.
- typical previous systems have used optical components that were sufficiently large and/or massive that functions such as focus and/or tracking were performed by moving components of the optical system. For example, some systems move the objective lens (e.g. for focus) relative to the laser or other light source.
- optical path then, passed through a disk substrate, or some other portion of the disk, typically passing through a substantial distance of the disk thickness, such as about 0.6 mm or more, before reaching a data layer.
- optical disks and other optical storage systems provided relatively large format read/write devices including, for example, devices for use in connection with 12 inch (or larger) diameter disks.
- read/write devices including, for example, devices for use in connection with 12 inch (or larger) diameter disks.
- optical storage technologies have developed, however, there has been increasing attention toward providing feasible and practical systems which are of relatively smaller size.
- a practical read/write device must accommodate numerous items within its form factor, including the media, media cartridge (if any), media spin motor, power supply and/or conditioning, signal
- an optical head occupying small volume is desirable.
- the optical head have a small dimension in the direction perpendicular to the surface of the spinning media.
- a smaller, more compact, optical head provides numerous specific problems for electronics designed to control the position and focus of the optical head.
- a system and method includes a control system design for controlling operation of a motor system that addresses the design challenges for the small form factor optical disk system.
- the optical disk system includes a spin motor on which an optical medium is positioned, an optical pick-up unit positioned relative to the optical medium, an actuator arm that controls the position of the optical pick-up unit, and a control system for controlling the spin motor, the actuator arm, and the laser.
- Embodiments of the control system and device in accordance with the present invention use several unique methods including sharing a general purpose processor between the servo system and other drive systems in the device, using a dedicated high speed processor for time critical servo functions, communicating between the dedicated servo processor and the shared general purpose processor, distributing the servo processing between the general purpose processor and the dedicated servo processor, and distributing the servo processing within the general purpose processor between a main loop process and a background periodic interrupt process.
- a control system in one aspect of the invention includes a lookup table module providing a first output in response to receiving an index value.
- the system further includes a controller module for processing the first output to provide a control command; and a drive module for processing the control command to commute a spin motor.
- a control system for an optical disk drive.
- the system includes a lookup table module providing a reference period corresponding to each of a physical sector address on an optical medium.
- the system further includes a drive module configured to sense a BEMF zero crossing occurring in a spin motor. A measurement of two of the BEMF zero crossings can be used to calculate a spin period measurement.
- the reference period can be compared to the spin period measurement to provide a period error value.
- the system also includes a controller module for providing a control command to drive the spin motor in response to the period error value.
- a method is provided for controlling the operation of an optical disk drive.
- the method includes providing a lookup table module configured to provide a reference period corresponding to each of a physical sector address on an optical medium; sensing a BEMF zero crossing using a BEMF detector to calculate a spin period measurement; comparing the reference period to the spin period measurement to provide a period error value; and providing a control command in response to the period error value.
- a method for controlling the spin speed of a motor.
- the method includes receiving a period value; receiving an integrator gain value (Ki) and a proportional gain value (Kp); updating an integration value in response to the integrator gain value; and outputting a motor control command in response to a proportional gain value.
- a system for controlling a spin motor.
- the system can include a first module for providing a period error, a proportional gain (Kp) and an integration gain (Ki).
- the system can also include a second module for operating on the Ki and Kp to provide an output and a third module for commutating the motor in response to the output.
- a method for controlling the spin speed of a motor.
- the method includes receiving a physical sector address (PSA) value and recording a current time of receipt; entering a database using a table index based on the PSA value; and providing reference data from the database corresponding to the table index to provide an output for providing a control effort.
- PSA physical sector address
- a method for controlling the spin velocity of an optical medium.
- the method includes reading a physical sector address (PSA) from an optical medium; calculating a table index based on the PSA; entering a lookup table module to acquire reference data; and maintaining a constant data rate transfer from the optical medium for a range of PSAs.
- PSA physical sector address
- a system for controlling spin velocity of an optical medium.
- the system includes a means for reading a physical sector address (PSA) from an optical medium; means for calculating a table index based on the PSA; means for entering a lookup table module to acquire reference data; and means for maintaining a constant data rate transfer from the optical medium for a range of PSAs.
- a method is provided for controlling a spin motor. The method includes comparing a first period corresponding to a first RPM at a first physical sector address (PSA) on an optical medium to a second period corresponding to a second RPM at a second PSA on the optical medium to provide a delta RPM. The method further includes driving a winding in the spin motor with a current to cause the spin motor to change velocity from the first RPM to the second RPM in response to the delta RPM being greater than a predetermined value.
- PSA physical sector address
- a method of controlling spin speed includes receiving an indication to make a velocity change from a
- a system for controlling spin speed includes a module for receiving an indication to make a velocity change from a first RPM to a second RPM. The difference between the first RPM and the second RPM is a predetermined value.
- the module is operable to rotate an optical medium at a maximum control effort from the first RPM to the second RPM, and rotate the optical medium with a proportional plus integral (P+I) control at the second RPM.
- P+I proportional plus integral
- the method includes detecting a first BEMF crossing and setting a first time stamp, detecting a second BEMF crossing and setting a second time stamp; calculating a measured spin period as the difference between the first time stamp and the second time stamp; comparing the measured spin period to a reference spin period to determine a period error; operating on the period error with a proportional gain and an integrator gain to provide a command output; and driving a winding in the spin motor with a current to cause the spin motor to change velocity in response to the command output.
- a system for controlling spin speed.
- the system includes a first module operable to detect a first BEMF crossing and setting a first time stamp and to detect a second BEMF crossing and setting a second time stamp.
- a second module is also included which is operable to calculate a measured spin period as the difference between the first time stamp and the second time stamp, and is also operable to compare the measured spin period to a reference spin period so as to determine a period error.
- a third module is operable to operate on the period error with a proportional gain and an integrator gain to provide a command output.
- a fourth module is included which is operable to drive a winding in the spin motor with a current to cause the spin motor to change velocity in response to the command output.
- a method for obtaining digital feedback from a spin motor.
- the method includes detecting data representing a position on an optical medium and determining a detection rate; comparing the detection rate to a reference rate to provide an error rate; generating an output command in response to the error rate to provide a drive output which commands a voltage applied to a spin motor to adjust the spin speed of said spin motor.
- a system for obtaining digital feedback from a spin motor.
- the system includes a control module operable to detect data representing a position on an optical medium and determine a detection rate. The detection rate can be compared to a reference rate to provide an error rate.
- the control module can also generate an output command in response to the error rate to provide a drive output which commands a voltage applied to a spin motor to adjust the spin speed of the spin motor.
- a method is provided for starting the operation of a motor including windings and a rotor. The method includes placing the motor in a first operational state; driving the motor from the first operational state to a second operational state; and sensing a variation in an electrical waveform induced by driving of the motor to determine a cycle period from which the speed of the motor can be determined.
- a startup control system for a motor including windings and a rotor.
- the system includes a start module configured to operate to place the motor in a first operational state; drive the motor from the first operational state to a second operational state; and sense a variation in an electrical waveform induced by driving the motor to determine a cycle period from which the speed of the motor can be determined.
- an optical disk drive system including a read/write optical unit, a motor for moving said optical unit, and a circuit for controlling the speed of the motor.
- the system includes a start module operably configured to execute the following method: placing the motor in a first operational state; driving the motor from the first operational state to a second operational state; and sensing a variation in an electrical waveform induced by the driving of the motor to determine a cycle period from which the speed of the motor can be determined.
- FIG. 1A shows an optical drive according to the present invention.
- FIG. IB is a simplified schematic illustration of a motor in accordance with the present invention.
- FIG. IC shows an example of an optical media that can be used with an optical drive according to the present invention.
- FIG. 2A shows an embodiment of an optical pickup unit mounted on an actuator arm according to the present invention.
- FIG. 2B shows an embodiment of an optical pick-up unit according to the present invention.
- FIG. 2C illustrates the optical path through the optical head of FIG. 2B.
- FIG. 2D shows an embodiment of optical detector positioning of the optical pick- up of FIG. 2B.
- FIG. 3 shows a block diagram of the components of a control system of an optical drive according to the present invention.
- FIG. 4 shows a block diagram of the controller chip shown in the block diagram of FIG. 3 according to the present invention.
- FIG. 5 shows a functional block diagram of a spin control servo block diagram for controlling the spin motor as shown in FIG. 3 according to the present invention.
- FIG. 6 shows a start spin algorithm for spinning up the spin motor of FIG. IB according to the present invention.
- FIG. 7 shows a block diagram of the spin control interrupt algorithm executed on the system shown in FIG. 5 according to the present invention.
- FIG. 8 shows a spin control algorithm which is called from the spin control interrupt algorithm of FIG. 7 according to the present invention.
- FIG. 9 shows an embodiment of a spin speed control algorithm called from the spin control algorithm of FIG. 8 according to the present invention.
- FIG. 10 is a block diagram of a PS A/PMAD feedback system.
- the servo systems may advantageously contain program logic or other substrate configuration representing data and instructions, which cause the servo system to operate in a specific and predefined manner, as described herein.
- the program logic may advantageously be implemented as one or more modules.
- the modules may advantageously be configured to reside on memory in processors and execute on the one or more processors.
- the modules include, but are not limited to, software, firmware, hardware or a combination thereof that perform certain tasks.
- a module may include, by way of example, software components, processes, functions, subroutines, procedures, attributes, class components, task components, object- oriented software components, segments of program code, drivers, firmware algorithms, micro-code, circuitry, data, and the like.
- the program logic is generally considered to be a sequence of processor-executed steps. These steps generally require manipulations of physical quantities. Usually, although not necessarily, these quantities take the form of electrical, magnetic, or optical signals capable of being stored, transferred, combined, compared, or otherwise manipulated. It is conventional for those of ordinary skill in the art to refer to these signals as bits, values, elements, symbols, characters, text, terms, numbers, records, files, and the like.
- an optical disk system includes a spin motor on which an optical media is positioned, an optical pick-up unit positioned relative to the optical media, an actuator arm that controls the position of the optical pick-up unit, and a control system for controlling the spin motor, the actuator arm, and the laser.
- the control system can include a read/write channel coupled to provide control signals to a servo system.
- the optical media can be a relatively small-sized disk with readable data present on the surface of the disk.
- the optical disk may have a pre-mastered portion and a writeable portion.
- the pre-mastered portion is formed when the disk is manufactured and contains readable data such as, for example, audio, video, text or any other data that a content provider may wish to include on the disk.
- the writeable portion is left blank and can be written by the disk drive to contain user information (e.g., user notes, interactive status (for example in video games), or other information that the drive or user may write to the disk).
- the optical pick-up unit includes a light source, reflectors, lenses, and detectors for directing light onto the optical media.
- the detectors include laser power feed-back detectors as well as data detectors for reading data from the optical media.
- the optical pick-up unit is mechanically mounted on the actuator arm.
- the actuator arm includes a tracking actuator for controlling lateral movement across the optical media and a focus actuator for controlling the position of the optical pick-up unit above the optical medium. The tracking and focus actuators of the optical pick-up unit are controlled by the controller.
- the focus actuator is a voice coil positioned to flex the actuator arm at a flexure line so that the optical pick-up unit moves in a direction perpendicular to the surface of the optical media.
- the tracking actuator can include a voice coil positioned so that the actuator arm can be rotated around a point on the actuator arm so that the optical pick-up unit can be positioned on tracks across the optical medium.
- the controller can further include control electronics for controlling the power to the laser.
- the laser power may be adjusted to a high level in order to write data to the optical data and adjusted to a low level in order to read data from the optical media.
- the servo system includes various feedback loops for controlling the operation of the spin motor, the optical pick-up unit, and the controller.
- the feedback loops for example, can include a tracking loop, a focus loop, a spindle speed control loop, and a laser power control loop.
- servo system according to the present invention operate even in the event of significant cross-talk between the individual feedback loops.
- a servo system can include track seeking (both multi-track seeking and one-track seeking), error recovery, and other functions related to the control of the optical pick-up unit, focus positioning and tracking positioning, during transfer of data to and from the optical media during read and write operations, respectively.
- a servo system can include calibration routines, which set and define operating parameters of the servo system.
- calibrations can be adaptively accomplished during operation of the disk drive. In some embodiments, calibrations are accomplished whenever a new optical disk is inserted into the optical drive.
- Control system 114 includes R/W processing 116, servo system 118, and output interface 120.
- Read/Write processing 116 controls the reading of data from optical medium 106 and the writing of data to optical medium 106.
- Read/Write processing 116 outputs data to a host (not shown) through output interface 120.
- Servo system 118 controls the speed of spin motor 102, the position of OPU 108, and the laser power in response to signals from R/W processing 116. Further, servo system 118 insures that the operating parameters (e.g., focus, tracking, and spin motor speed) are controlled in order that data can be read from or written to optical medium 106.
- FIG. IC shows an example of optical medium 106.
- Optical medium 106 can include any combinations of pre-mastered portions 150 and writeable portions 151.
- Pre- mastered portions 150 for example, can be written at the time of manufacture to include content provided by a content provider.
- the content for example, can include audio data, video data, text data, or any other data that can be provided with optical medium 106.
- Writeable portion 151 of optical medium 106 can be written onto by optical drive 100 to provide data for future utilization of optical medium 106.
- the user for example, may write notes, keep interactive status (e.g., for games or interactive books) or other information on the disk.
- Optical drive 100 for example, may write calibration data or other operating data to the disk for future operations of optical drive 100 with optical medium 106.
- optical media suitable for use in drive 100 is available from Dataplay, Inc., Boulder, Colorado, USA.
- the R/W Data Processing 116 can operate with many different disk formats.
- an optical medium uses a single structure or format (such as identical materials, layers and the like) for both a region for holding mastered data, e.g., data which is written substantially all at once or in parallel, and for defining a writeable area, such as a user- writeable area.
- Optical drive 100 can be included in any host, for example personal electronic devices.
- optical drive 100 can have a relatively small form factor such as about 10.5 mm height, 50 mm width and 40 mm depth.
- FIGS. 2B and 2C show an embodiment of OPU 108.
- OPU 108 of FIG. 2B includes a periscope 210 having reflecting surfaces 211, 212, and 213.
- Periscope 210 is mounted on a transparent optical block 214.
- Object lens 223 is positioned on spacers 221 and mounted onto quarter wave plate (QWP) 222 which is mounted on periscope 210.
- Transparent optical block 214 is, in turn, mounted onto turning mirror 216 and spacer 224, which are mounted on a silicon submount 215.
- a laser 218 is mounted on a laser mount 217 and positioned on silicon submount 215.
- detectors 225 and 226 are positioned and mounted on silicon substrate 215.
- a high frequency oscillator (HFO) 219 can be mounted next to laser 218 on silicon submount 215 to provide modulation for the laser beam output of laser 218.
- HFO high frequency oscillator
- Laser 218 produces an optical beam 224 which is reflected into transparent block 214 by turning mirror 216. Beam 224 is then reflected by reflection surfaces 212 and 213 into lens 223 and onto optical medium 106 (FIG. 1A). In some embodiments, reflection surfaces 212 and 213 can be polarization dependent and can be tuned to reflect substantially all of the light from laser 218. QWP 222 rotates the polarization of laser beam 224. The reflected beam 230 from optical medium 106 is collected by lens 223 and focused into periscope 210. A portion (in some embodiments about 50%) of reflected beam 230 passes through reflecting surface 213 and is directed onto optical detector 226.
- reflected beam 230 passes through reflecting surface 212 and is reflected onto detector 225 by reflecting surface 211. Because of the difference in path distances between the positions of detectors 225 and 226, detector 226 is positioned before the focal point of lens 223 and detector 225 is positioned after the focal point of lens 223, as is shown in the optical ray diagram of FIG. 2C.
- FIG. 2D shows an embodiment of detectors 225 and 226 according to the present invention.
- Detector 225 includes an array of optical detectors 231, 232, and 233 positioned on submount 215. Each individual detector, detectors 231, 232, and 233, is electrically coupled to provide signals A, E and C to control system 114 (FIG. 1 A).
- Detector 226 also includes an array of detectors, detectors 234, 235 and 236, which provide signals B, F, and D, respectively, to control system 114.
- center detectors 232 and 235, providing signals E and F, respectively, are arranged to approximately optically align with the tracks of optical medium 106 (FIG. 1 A) as actuator arm 110 (FIG. 1A) is rotated across optical medium 106.
- the degree of focus can be determined by measuring the difference between the sum of signals A and C and the center signal E of detector 225 and the difference between the sum of signals B and D and the center signal F of detector 226.
- a tracking monitor can be provided by monitoring the difference between signals A and C of detector 225 and the difference between signals B and D of detector 226.
- spin motor 102 can be a three- phase, brushless spin motor connected to the associated control and drive circuitry as described herein.
- spin motor 102 is a twelve- pole motor having nine windings, which indicates that the motor magnet has six pairs of N/S magnet poles (i.e. twelve pole motor) and includes 9 stator slots on which the coils are wound. The nine windings are grouped into three coils A c , B c , and C c , where each winding set is selectively driven at a predetermined phase.
- Spin motor 102 includes rotor shaft 104, which rotates responsive to the magnetic fields generated by the current flowing through coils A c , B c , and C c being energized in a standard sequence, such as in bipolar operation.
- the rotor of spin motor 102 has a segmented magnet which in conjunction with the stator coils generates a rotational force proportional to the current in coils A c , B c , and C c .
- motor sequencer 326 applies a current to the coils in a specific sequence, which is synchronized with the rotor position. In bipolar operation, sequencer 326 controls spin motor 102, such that current is driven through two coils while a third coil is left floating.
- optical drive 100 presents a multitude of challenges in control over conventional optical disk drive systems.
- a conventional optical disk drive system may perform a two-stage tracking operation by moving the optics and focusing lens radially across the disk on a track and may perform a focusing operation by moving a focusing lens relative to a disk.
- conventional optical disk drive systems are much larger than some embodiments of optical drive 100.
- Some major differences include the actuator positioning of actuator arm 110, which operates in a rotary fashion around spindle 200 (FIG. 2A) for tracking and with a flexure action around axis 206 for focus. Further, the speed of rotation of spin motor 102 is dependent on the track position of actuator arm 110.
- servo system 118 pushes the bandwidth of the servo system as hard as possible, but not so hard that mechanical resonance in actuator arm 110 are excited, to avoid erroneously responding to mechanical and optical cross couplings.
- control system 114 can include operating at lower bandwidth with large amounts of cross coupling and nonlinear system responses from operating closer to the bandwidth. Additionally, the performance of optical drive 100 should match or exceed that of conventional CD or DND drives in terms of track densities and data densities.
- FIG. 3 shows a block diagram of an embodiment of control system 114 according to the present invention.
- Optical signals are received from OPU 108.
- some embodiments of OPU 108 include two arrays of detectors with array 225 including detectors 231, 232, and 233 for providing signals A, E, and C, respectively, and array 226 having detectors 234, 235 and 236 providing signals B, F, and D, respectively.
- Signals received from OPU 108 are typically current signals. Therefore, the signals from OPU 108 are converted to voltage signals in a preamp 254.
- Preamp 254 can include a transimpedance amplifier, which converts current signals to voltage signals.
- preamp 254 generates a high frequency (HF) signal based on the input signals from OPU 108.
- the HF signal can be formed by the analog sum of the signals from OPU 108 (signals A, B, C, D, E and F).
- Control chip 250 is a digital and analog signal processor chip which digitally performs operations on the input signals A, B, C, D, E, F, HF, and laser power to control the actuators of actuator arm 110 (FIG. 1A), the laser power of laser 218 (FIG. 2B), and the motor speed of spin motor 102.
- Control chip 250 also operates on the HF signal to read the data and communicates data and instructions with a host (not shown).
- a type of control chip, Part No. 34-00003-03 is available from ST Microelectronics.
- the laser power signal is further input to laser servo 112 along with the W R command.
- Power driver 252 also provides current to drive spin motor 102.
- Spin motor 102 can provide sensors to track the position of OPU 108 so that the speed of spin motor 102 can be related to the track. In some embodiments, the data rate is held constant by controlling the speed of spin motor 102.
- power driver 252 can also control a cartridge eject motor 260 and latch solenoid 262 in response to commands from control chip 250.
- cartridge eject motor 260 mounts and dismounts optical medium 106 onto spin motor 102.
- Latch solenoid 262 provides a means to latch the actuators so that they cannot move in the focus or tracking directions when the drive is not active. This is to prevent actuator or disk damage during a non-operating shock.
- control system 114 can include power monitor 264 and voltage regulator 266.
- Power monitor 264 provides information about the power source to control chip 250.
- Power monitor 264 for example, can reset control chip 250, in the event of a power interruption.
- voltage regulator 266, in response to an on/off indication from control chip 250, provides power to drive laser 218, spin motor 102, actuators 208 and 204, cartridge eject motor 260, and latch solenoid 262.
- Some factors which may further lead to offset and gain settings include light scattering onto detectors, detector variations, detector drift, or any other factor which would cause the output signal from the detectors of OPU 108 to vary from ideal outputs.
- Various calibration and feedback routines can be operated in microprocessor 270 and DSP 272 to maintain efficient values of each of the offset and gain values of offset block 274 and amplifiers 276, respectively, over various regions of optical medium 106.
- the offset and gain values of offset block 274 and amplifiers 276 can be varied by microprocessor 270 and DSP 272 as OPU 108 is positionally moved over optical medium 106.
- microprocessor 270 and DSP 272 monitor the offset and gain values of offset block 274 and amplifiers 276 in order to maintain optimum values for the offset and gain values as a function of OPU 108 position over optical medium 106.
- the offset values of offset block 274 and amplifiers 276 are determined such that the dynamic range of the respective input signals are centered at zero. Further, the gains of amplifiers 276 are set to fill the dynamic range of analog-to-digital converters 278-1 and 278-2 in order to reduce quantization error.
- FOK 290 determines if the total intensity of light on detectors 225 and 226 is above a threshold value indicating a near in-focus condition. In some embodiments, this function can also be executed in software in the servo system.
- Digitized detector signals A d , E d , C d , B d , Fd, and D are input to decimation filters 292-1 through 292-6, respectively.
- Decimation filters 292-1 through 292-6 are variable filters which down-sample the digitized detector signals A d , E d , C d , B d , F d , and D d to output signals Af, Ef, C f , B f , F f , and D f , which are input to DSP 272.
- each of signals A , E , C , B , F , and Dd can be effectively sampled at 6.6 MHz by ADC 278-1 and 278-2.
- Decimation filters 292-1 through 292-6 can then down- sample to output signals A f , E f , C f , B , F f , and D f at, for example, about 90 kHz.
- Embodiments of decimation filters 292-1 through 292-6 can down-sample to any sampling rate, for example from about 26 kHz to about 6.6 MHz.
- the servo information can be at lower frequencies.
- the mechanical actuators 208 and 204 of actuator arm 110 can respond in the hundreds of Hertz range yielding servo data in the 10s of kHz range, rather than in the mHz ranges of optical data. Further, mechanical resonance of actuator arm 110 can occur in the 10s of kHz range. Therefore, down-sampling effectively filters out the high frequency portion of the spectrum which is not of interest to servo feedback systems. Further, a much cleaner and more accurate set of digital servo signals A f , E f , C f , B f , F f , and D f are obtained by the averaging performed in decimation filters 292- 1 through 292-6, respectively. In some embodiments, decimation filters 292-1 through 292-6 can be programmed by microprocessor 270 or DSP 272 to set the output frequency and further filtering characteristics.
- Embodiments of optical drive 100 operate in extremes of physical abuse and environmental conditions that may alter the resonant frequency characteristics and response characteristics of spin motor 102, optical medium 106, and actuator arm 110.
- the digital output signals A d , E d , C , B d , F , and D d are further input to summer 294.
- Summer 294 can be a programmable summer so that a sum of particular combinations of inputs A , E d , C , B , F , and D can be utilized.
- Summer 294 sums a selected set of signals Ad, E d , Cd, B , F d , and D to form a low-bandwidth digitized version of the HF signal.
- the output signal from summer 294 is multiplexed in multiplexer 296-1 and multiplexer 296-2 with the digitized HF signal HF output from ADC 278-1.
- a HF select signal input to each of multiplexer 296-1 and 296-2 selects which of HF d or the output signal from summer 294 are chosen as the output signal from multiplexer 296-1 and 296-2.
- the output signal from multiplexer 296-1 is input to disturbance detector 298.
- Disturbance detector 298 detects a media defect to optical medium 106 by monitoring the data signal represented by HF d or the output from summer 294 and alerts DSP 272 of a defect.
- a defect can include, for example, a scratch or speck of dust on optical medium 106.
- the signal from gain 286 can be input to sheer 315, DPLL 317, and sync mark detector 319 to provide another indication of the speed of spin motor 102.
- Sheer 315 determines a digital output in response to the output signal from equalizer 284 and amplifier 286. Sheer 315 indicates a high state for an input signal above a threshold value and a low state for an input signal below the threshold.
- DPLL 317 is a digital phase-locked loop, which servos a clock to the read back signal so that sync marks on the tracks can be detected.
- Sync mark detector 319 outputs a signal related to the period between detected sync marks, which indicates the rotational speed of spin motor 102.
- an angular spindle speed feedback indication for example, the bemf_in signal, can be used as an indication of the speed of spin motor 102.
- Each of these speed indications can be input to multiplexer 321, whose output is input to microprocessor 270 as the signal which indicates the rotational speed of spin motor 102.
- Microprocessor 270 can choose through a select signal to multiplexer 321 which of the rotational speed measurements to use in a digital servo loop for controlling the rotational speed of spin motor 102.
- the wobble frequency of PushPuUBP is in the 100 kHz range (in some embodiments around 125 kHz) and therefore, with decimation filters 292- 1 through 292-6 operating at around 70 kHz, is filtered out of signals Af, E f , C f , B f , F f , and D f .
- Microprocessor 270 and DSP 272 output control signals to drivers which affect the operation of optical drive 100 in response to the previously discussed signals from actuator arm 110 and spin motor 102. For example, a control signal from microprocessor 270 is output to spin control servo module 302 to provide a spin control signal for controlling spin motor 102.
- a digital servo system executed on microprocessor 270 or DSP 272 is further discussed below.
- Microprocessor 270 and DSP 272 can communicate through direct connection or through mailboxes.
- DSP 272 operates under instructions from microprocessor 270.
- DSP 272 may be set to perform tracking and focus servo functions while microprocessor 270 provides oversight and data transfer to a host computer or to buffer memory. Further, microprocessor 270 may provide error recovery and other functions.
- DSP 272 controls tracking and focus servo systems while microprocessor 270 controls all higher order functions, including error recovery, user interface, track and focus servo-loop closings, data transport between optical medium 106 and buffer memory, and data transfer between the buffer memory and a host, read and write operations, and operational calibration functions (e.g. , setting offset and gain values for offset 274 and amplifiers 276 and operational parameters for decimation filters 292-1 through 292-6).
- operational calibration functions e.g. , setting offset and gain values for offset 274 and amplifiers 276 and operational parameters for decimation filters 292-1 through 292-6).
- optical medium 106 may require that OPU 108 travel across optical medium 106 from the OD to the ID with optical medium 106 spinning such that the data directly under OPU 108 travels at a constant linear velocity during read and/or write operations to provide and maintain a constant data rate to R/W data processing 116.
- seek mode is used when the target spin speed is different from the current spin speed, for example, by more than 100 RPM. This is usually as a result of a seek command directing OPU 108 to a different radial position.
- control system 118 commands maximum acceleration if the motor speed is too slow and commands maximum deceleration if the motor speed is too fast.
- Seek mode can be disabled as soon as the speed is faster than the target speed when speeding up and as soon as the speed is slower than the target speed when slowing down.
- P+I proportional plus integral
- control module 302 receives a physical sector address (PSA), which is generally indicative of the location of data on optical medium 106 (e.g., the unique address of each track and sector, FIG. IC).
- PSA physical sector address
- the PSAs can be encoded at the beginning of each sector in the Mastered Media portion of optical medium 106.
- PMAD Pre-mastered Address
- the PSA and PMAD can be used interchangeably to refer to an address of a track or sector on optical medium 106.
- Control chip 250 reads the PSAs anytime the tracking servo is actively following a track.
- lookup table module 306 includes a list of reference periods that correspond to a spin speed when reading or writing at the corresponding PSA. A substantial match between the Reference Period from lookup table module 306 and a measured Spin Period indicates that spin motor 102 is substantially spinning at the desired RPM.
- lookup table module 306 can be used to slowly adjust the Target Spin Period as the PSA numbers continue to increment.
- target PSA 304a shown in FIG. 5, can be used to determine the Target Spin Period for the read or write operation that occurs at the end of a seek operation. In general, the system wants to read or write to the address represented by target PSA 304a.
- control module 302 receives a media type indication 304c from the DSA (FIG. IC) that provides information about optical medium 106, such as the type of media being used and the PSA/PMAD boundaries for the pre-mastered and mastered portions. As described below, media type indication 304c ensures that data is acquired from the proper data table corresponding to either the mastered or pre-mastered portions of optical medium 106 as appropriate.
- Lookup table module 306 includes logic capable of receiving input target PSA 304a or current PSA 304b and media type indication 304c.
- the PSAs are represented by an integer number, which can be used as an Index to enter lookup table 306 and locate reference data, such as a reference period, a proportional gain (Kp) and integrator gain (Ki) corresponding to the PSA number.
- a correction factor can be applied in the event that controller module 308 misses a reading of one or several PSAs. For example, a PSA can be delivered every 2 msec. Thus, if 4 msec have passed since controller module 308 reads a PSA, the algorithm adds 2 (4 msec/2) to the last PSA number read. The corrected PSA can then be used as the Index for lookup table module 306 to provide the reference data for controller module 308.
- lookup table 306 can be divided into a first and a second lookup table.
- the first lookup table can include reference data corresponding to the PSAs found in the pre-mastered portion of optical medium 106.
- the second lookup table can include reference data corresponding to the PSAs found in the writeable portion of optical medium 106.
- Media type indication 304c can be used to direct the system to the proper table.
- the first and second lookup tables allow optical disk system 100 to operate in a dual media mode.
- Physical sector address 304a and PSA 304b can be received at any rate based upon such parameters as the design of spin motor 102 and servo system 118.
- PSA 304a and PSA 304b can be received in control module 302 at an average rate of about two milliseconds.
- the PSA number indicates a row in lookup table 306.
- the PSA Index is a number corresponding to an element in a row, 1-N, in lookup table 306.
- Lookup table module 306 can include logic to provide an integrator gain (Ki) and a proportional gain (Kp).
- Ki and Kp are functions of the reference period corresponding to each PSA.
- Gains Ki and Kp can be formulated using an equation that accounts for measuring Spin Period (proportional to 1/RPM) and controlling Spin Speed (RPM).
- Ki and Kp can be determined using the equations as follows:
- Ki K 2 /(K,/RPM)
- any number of methods could be used to generate the Ki and Kp signals, such as, for example, simulating the speed control loop at each target Spin Period.
- lookup table module 306 provides for faster operations to be performed by microprocessor 270, since a 1 /period calculation is not necessary to determine spin RPM.
- Summing module 325 including summing circuitry, is provided to compare the Reference Period from lookup table module 306 for a given PSA to a spin period measurement generated from a speed interrupt pulse provided from drive module 253, as described below. The time is recorded at each occurrence of the speed interrupt pulse received by summing module 325. The time is compared to a previously recorded time corresponding to a previously received speed interrupt pulse, the difference in time representing the spin period measurement. Summing module 325 generates a feedback element representing the Period Error between the Reference Period and the Measured Period of spin motor 102.
- Controller module 308 performs an integration function, which provides an output command, used by drive module 253 to, in turn, provide a drive output, used to start, stop, and quickly change the spin speed of spin motor 102, as desired.
- Controller module 308 is provided with Ki and Kp from lookup table module 306 that correspond to a PSA.
- controllers used in motor control servos, such as in hard drives have a fixed sample period, since the target RPM is constant. Accordingly, in typical controllers a fixed gain for a proportional and a fixed gain for the integral controller can be used that provides the dynamics or bandwidth required to provide controls solutions.
- the period of optical drive 100 can vary as spin motor 102 changes velocity, for example, from about a 1500 RPM to a 4500 RPM.
- Controller module 308 keeps the servo control bandwidth constant as RPMs vary by using different and variable proportional and integral gaining for all sample rates.
- the Period Error is input to controller module 308 from summing circuitry 325.
- Controller module 308 updates the Integrator value, as necessary, by incrementing the Integrator value by the product of Ki and the Period Error.
- controller module 308 increments the proportional value by calculating the product of Kp and the Period Error to generate the output command.
- Integrator Value Integrator Value + (Period Error * Ki)
- Output Command (Period Error * Kp) + Integrator Value
- the Integrator value is the sum of the product of Ki times the Period Errors for all time since the Integrator Value is initialized.
- Controller module 308 provides the output command to drive module 253, which allows drive module 253 to determine the amount of voltage to apply to change the speed of spin motor 102.
- the output command can be a 9 bit number, which can be sent over a serial interface to drive module 253.
- Drive module 253 is provided to interface directly to spin motor 102 and control the electrical commutation of spin motor 102 once the spin motor begins to run (i.e., after start module 400 (FIG. 6) is performed). As previously mentioned, drive module 253 provides the spin interrupt pulses used to measure the Spin Period and control Spin Speed.
- Drive module 253 provides a pulse or an interrupt, which corresponds to each occurrence of a BEMF zero-crossing in spin motor 102, as described below.
- Drive module 253 detects the BEMF zero crossing on the coil leads that drive spin motor 102 to determine rotor position.
- the BEMF zero crossing interrupts occur at a rate depending on the type of spin motor. For example, in a twelve-pole motor the BEMF zero crossing interrupts occur at a rate of 6 times per revolution.
- the spacing between interrupts can vary because the magnetic poles on the rotor are typically not perfectly spaced during motor manufacture.
- spin motor 102 must achieve a nominal spin velocity to generate detectable BEMF zero crossings.
- spin motor 102 can be stationary.
- a start-up logic 400 is provided to begin the movement of spin motor 102.
- the initial start-up sequence of spin motor 102 can be an open-loop sequence (i. e. , no feedback) until the motor reaches the nominal speed.
- FIG. 6 is a flow diagram illustrating an embodiment of start module 400 for causing the initial movement of spin motor 102 of FIG. IB in accordance with the present invention.
- start module 400 includes logic that initiates movement of spin motor 102 from a non-moving, non-spinning or stationary condition to a moving, spinning or non-stationary condition.
- the non-moving condition may include any time the rotation of spin motor 102 is inadequate to provide efficient operation of optical drive
- Start module 400 can be implemented any time that spin motor 102 needs to spin up optical medium 106. In most embodiments, start module 400 has substantially no information at startup about the position or state of spin motor 102 or the alignment of rotor shaft 104.
- Start module 400 initializes the system hardware to set up the operational parameters.
- a plurality of registers such as a current limiter, torque optimizer, fine torque optimizer, Kval, lockspeed, drive mode, and closed loop, coast, and brake, are initialized with operational parameters.
- the parameters provide information regarding the amount of current to use.
- rotor shaft 104 In powering up the first coil, rotor shaft 104 can be made to move, such that rotor shaft 104 is jogged to an initial position.
- a pair of drivers can be connected to each of the three motor coils.
- the state of sequencer 326 (FIG. IB) determines which drivers are turned on and whether the drivers pull the coil line to ground or to a Power Supply. If a specific coil has current flowing through it, the specific coil will attract the rotor to a given position. The rotor stops in this position until the next coil is energized, which causes the rotor to move to the next position. If this next coil stays energized with a fixed current then the rotor will stop in this next position.
- a second state is achieved by powering a second coil positioned adjacent to the first coil in the preferred direction of rotation.
- the powering of the second coil causes rotor shaft 104 to move slightly in the preferred direction.
- the powering up of the second coil substantially ensures, for example, that if spin motor 102 is in a very low torque position (i. e. , high friction) during the first state, enough torque is generated to align rotor shaft 104.
- the routine in module 400 pauses again for a time period long enough to allow spin motor 102 to settle down, for example, between about 100 and about 300 milliseconds.
- alignment phase 406 of start module 400 substantially ensures that spin motor 102 is locked into a known fixed position and is ready to be rotated in a known direction.
- spin motor 102 since there is no physical contact between optical medium 106 and OPU 108, spin motor 102 does not require reverse rotation protection to prevent reverse movement that could damage, for example, OPU 108 and optical medium 106.
- First acceleration phase 408 is open loop and occurs before spin motor 102 is moving fast enough to be monitored by drive module 253.
- acceleration phase 408 provides an open loop step sequence to accelerate spin motor 102 to the nominal RPM, such as from about 900 RPM to about 1000 RPM.
- the acceleration of spin motor 102 can be made to follow a pre-designed acceleration profile.
- the open loop startup runs spin motor 102 by timing the commutation steps. Since the load (i. e. , the inertia of the optical medium 106) can be approximated, the open loop startup can be simulated. The simulation can yield the sequence of timing events. At the end of the timing sequence, the RPM of spin motor 102 can be made to match that of the simulation.
- the acceleration profile can be designed such that spin motor 102 is capable of accelerating at the rate of the profile under worst case conditions.
- a sequence loop is initialized and made to accelerate spin motor 102 by stepping the motor through electrical states.
- spin motor 102 is stepped to the next electrical state with a time delay between each successive state being made shorter using a variable delay.
- the number of iterations required to achieve the final RPM can be determined from the given acceleration profile.
- the sequence loop continues for 1 to N iterations and/or until spin motor 102 has reached the nominal RPM.
- the sequencing loop is made to perform from between 10 to 50 iterations, for example 25 iterations before reaching the nominal RPM.
- drivers are floated with no load (i.e., turned off) and set to open loop, which means that spin motor 102 is coasting at approximately the nominal RPM. While coasting spin motor 102 may slow down due to friction and the like.
- An initial Run Voltage is set during action 412 at a voltage sufficient to keep spin motor 102 operating at or near the nominal RPM to keep the motor spinning until the speed control firmware is enabled.
- Action 413a of start module 400 enables the BEMF interrupt detection in drive module 253 after entering the coast phase.
- the BEMF detection capability in drive module 253 is enabled, such that drive module 253 begins to detect the BEMF zero crossings and provides BEMF interrupt pulses to summing module 325.
- drive module 253 can begin closed loop motor control.
- spin motor 102 can be allowed to coast for a fixed time duration, for example, 20 milliseconds, to provide enough time for at least two BEMF interrupts to be detected.
- drive module 253 is set to a sine drive mode. While spin motor 102 is coasting, the chip commutation, the voltage between a pair of windings, the magnets and the rotor create a sine wave variation on each of the windings. In this state, the voltage on the windings of spin motor 102 can be an AC waveform induced by the rotor magnets moving by the stator coils (i.e., BEMF).
- drive module 253 detects the BEMF zero crossing and initiates a pulse or BEMF interrupt. The BEMF interrupt causes a clock to record the time. At the next BEMF zero crossing, drive module 253 initiates a second pulse, which again causes the recording of the time.
- drive module 253 detects the BEMF zero crossings on one of the coils using, for example, an analog comparator circuit. The period indicates how fast spin motor 102 is rotating. Once the period is known, drive module 253 starts an internal state machine, which can commute spin motor 102.
- the state machine is hardware that generates the proper sequence of voltages applied to the windings of spin motor 102 to keep spin motor 102 spinning.
- drive module 253 provides a delay for a fixed time duration, for example, about 200 milliseconds.
- the delay is provided to allow the internal state machine to settle to the spin period before applying a rapid acceleration command. The delay ensures that the state machine does not lose synchronization.
- drive module 253 can be further synchronized to predetermine approximately where the next window for a BEMF zero crossing will occur.
- the window is not a fixed time, but rather the window is a percentage of the last measured BEMF zero crossing period. If the window is loose (i.e., too large), the spin control becomes inefficient since spin motor 102 continues to coast (and slow down) while looking for the BEMF zero crossing. Better spin control and commutation is achieved having the search window as tight or small as possible.
- Drive module 253 searches a very narrow window for zero crossings using a modulating pulse.
- drive module 253 causes a chopped voltage to be input into a coil of spin motor 102, such that the voltage chopping can be measured to know about where the zero crossing is going to occur.
- Drive module 253 shuts off that one coil while it is looking for the crossing
- drive module 253 provides another delay for a fixed time duration, for example, 200 milliseconds.
- the second delay allows drive module 253 to settle, such that the velocity of spin motor 102 and the BEMF circuitry are synchronized.
- spin motor 102 is performing under BEMF commutation, which means drive module 253 is detecting BEMF zero crossings and spin motor 102 remains synchronized with the interrupts continuously.
- start module 400 enters into a second acceleration phase, where spin motor 102 is made to accelerate to a predetermined operational RPM.
- the operational RPM is selected to be fast enough to prevent inadvertently writing to optical medium 106.
- a state machine is set in speed lock detector 310 to indicate that the operational RPM has been achieved.
- the system waits to receive a spin event or time out signal.
- the time out signal signifies that no interrupts have occurred in a predetermined period indicating that spin motor 102 is not spinning properly.
- a spin event signifies that the spin up module has completed it's function.
- Start module 400 can require as much time as necessary to adequately start the movement of spin motor 102. In one embodiment, every time spin motor 102 is started and start module 400 is performed, it may take from approximately 200 milliseconds to about 1 second; for example 500 milliseconds total time to spin up and place spin motor 102 under BEMF commutation.
- spin control servo system 300 in accordance with the present invention can maintain the speed control of spin motor 102 (CLV mode) or can accelerate or decelerate (seek mode) to the speed required for new locations on optical medium 106.
- CLV mode speed control of spin motor 102
- seek mode decelerate
- FIG. 7 shows a block diagram of a spin interrupt module 420 executed on spin control system 300 shown in FIG. 5 in accordance with the present invention.
- Spin interrupt module 420 provides the ability to measure the speed of spin motor 102.
- Spin interrupt module 420 can be called from start module 400 to provide speed control allowing spin motor to accelerate to the operational RPM. Spin interrupt module 420 can also be called when a large speed adjustment is needed, such as in a seeking operation or when a small speed adjustment is needed, such as during normal operation.
- logic in action 502, can be provided that provides a "Watchdog" function, which records if and when interrupt 500 has occurred.
- the Watchdog function monitors the BEMF interrupts and determines if the BEMF interrupts stop occurring or if the BEMF interrupts start occurring too frequently. In either of these situations, the Watchdog indicates that an error has occurred and an error recovery action must be taken. For example, in the event that spin motor 102 is inadvertently stopped, spin control system 300 (FIG. 5) can be made to cease operation (i.e., freeze), since the watchdog logic (and subsequently, the error handling routines) does not sense that the next interrupt has occurred.
- the watchdog logic also monitors the rate of the occurrences, to ensure that the interrupts occur at some minimum rate.
- action 504 if the checker senses a period that would represent a velocity of 6000 RPMs or more, the checker implements a counter that registers that a "bad period" was sensed (action 506). Any number of bad periods can be allowed before initiating major error recovery algorithms, for example five bad periods in a row may be allowed before initiating major error recovery (action 508).
- the major error recovery disables the spin interrupt which then would cause an error recovery state machine to restart spin motor 102 (action 510). Once the period is believable the spin control interrupt module 420 continues its operation.
- a record of spindle position is maintained, for example, to know the angular position of optical medium 106.
- an Index Counter is used, which keeps track of the BEMF interrupts per revolution.
- the Index Counter can be used for several purposes.
- the Index Counter is used to count revolutions during seeks to correct for spiral. For example, during a seek in the OD direction, a track can be added to the seek length for every index counted during the seek operation.
- Another use of the Index Counter is to synchronize the output waveform for repeatable runout feedforward control. The repeatable runout feedforward control requires an index and a sub-period.
- OPU 108 follows a spiral and moves inward one track per revolution.
- a "jump-back" algorithm can be set which causes a jump-back of one track every revolution to revisit a track.
- the jump-back algorithm can be used to maintain radial position at a location on optical medium 106 or to re-read a small portion of the data on optical medium 106.
- the jump-back can be set to two tracks every two revolutions or, for example, N tracks every N revolutions.
- a timer or index is set, winch is incrementally maintained for every one revolution of the motor to keep a count of the number of revolutions to determine whether it is time to do another jump-back.
- the Jump-Back is synchronized with the rotation rate by the BEMF interrupt.
- FIG. 8 shows a spin speed control module, which can be called from spin control interrupt module 420 in action 516 (referred to hereinafter as "spin speed module 516") of FIG. 7 according to the present invention.
- spin speed module 516 can be called six times per revolution to perform the actual speed control.
- spin speed module 516 is called once per BEMF interrupt.
- the measured period is compared to a reference period to determine the difference between the two periods and generate a period error.
- an index checker determines whether or not the period is an index period as calculated in action 512 of FIG. 7.
- the Index Period is the period measured when the index counter gets to the index count (for example, every 6 interrupts-one per revolution).
- spin speed module 516 limits the size of the period error calculated in action 602.
- the error is limited to ensure that the system processor, whether a 16 bit, 32 bit or higher bit processor, does not overflow the arithmetic operations.
- the error is limited by comparing the period error to a
- Spin speed module 516 initiates slew mode, which can be used to quickly change the velocity of spindle motor 102 during, for example, during start-up operation, seeking operations or when optical drive 100 experiences a shock, which causes optical drive 100 to be knocked off track.
- the slew mode is set to accelerate or decelerate spin motor 102 to a relatively high or low speed.
- Slew mode does not require intermediate speed control, since the target speed is based on where the speed is going to end up after spin motor 102 is spun-up for a given PSA number. Instead, slew mode uses a full on or full off control. Slew mode can be optimized to accomplish the speed change quickly with mimmum over/undershoot.
- action 610 a decision is made as whether slew mode is active. Slew mode is made active when it is determined that a new speed is required that is more than 100 RPM higher or lower than the present speed. Action 610 checks the slew mode flag to determine if slew mode is active.
- the integrator function is initialized with the starting value that has been determined to minimize the transient and a non-slew mode is set. Accordingly, when the next interrupt occurs, the routine will not enter slew mode at 610.
- control output is set with the value received from the Integrator rather than a zero as when in slew mode.
- the routine exits slew mode and continues at 624.
- action 626 if the period is less then the target period, the integrator function is initialized with the starting value that has been determined to minimize the transient and the mode is set to not slew (action 620). Accordingly, when the next interrupt occurs, the routine will not enter slew mode at 610.
- control output is set with the value received from the integrator function rather than a zero as before during slew mode.
- the routine exits slew mode and continues at 624.
- the proportional term is calculated.
- the proportional term is the proportional gain Kp (FIG. 5) multiplied by the period error.
- the sum of the Ki and Kp terms may be divided by a factor, if necessary, to correct for units.
- drive module 253 can command the voltage.
- the output of drive module 253 is limited to a 9 bit control register to ensure that no more than full scale is output.
- a check is provided to indicate if the system is in an index state.
- the Index is set after a number of interrupts are received. For example, the Index can be incremented after every revolution (i.e, after receiving six BEMF interrupts). If the system is not in an index state, the routine can continue without entering into CLV mode.
- the system is in an index state, and the I/O that had been set high in action 606 is turned off or set to low. This creates a short pulse going out through an I/O line every time index occurs (e.g., every six BEMF interrupts).
- a checker determines if PSAs are being read to determine if the CLV routine is necessary. During spin up and during seek, the system cannot read PSAs. Thus, in action 646, if PSAs are not being read, the routine returns to 648 and continues. In action 646, if PSAs are being read, the routine enters action 650 to update the CLV target as described with reference to FIG. 9. Once the CLV target is updated the routine returns to point 652 and continues.
- FIG. 9 shows an embodiment of a spin speed control module 650 called from spin speed module 516 of FIG. 8 according to the present invention. Spin speed control module 650, called once per revolution (i.e.
- speed control module 650 can update the PSA number if necessary (i.e., the PSA number is old) and the time of the reading is known.
- a check is made to determine the age of the PSA number.
- the checker compares the current time stamp to the old time stamp, if more than a specific check time has elapsed, for example, more than 48 milliseconds, it is assumed that the PSA is no longer valid.
- the remainder of speed control module 650 is bypassed and the routine continues at 726.
- the PSA maximum is limited to prevent overrun of lookup tables module 306 (FIG. 5).
- PSA number velocity versus PSA number is not necessarily a linear function, since it is equal to 1 over radius function, in one embodiment, the PSA is compared to a constant known to be the largest valid PSA. If the PSA is larger than this maximum valid PSA then it is set to this maximum before the table lookup occurs. As OPU 108 spirals in from the OD to the ID, which takes it to higher PSA numbers, the incremental speed difference per revolution becomes greater.
- lookup table module 306 (FIG. 5) is divided into two sections. The first section provides PSA numbers that correspond to positions on the outer radius.
- the second section provides PSA numbers that correspond to positions on the inner radius. The positions on the inner radius change much quicker than positions on the outer radius and therefore the resolution is higher.
- the two section lookup table module 306 conserves table space and keeps the maximum linear velocity error small.
- the PSA is compared to a reference number.
- the reference number is determined to correspond to the largest PSA in the low resolution table.
- the reference number can be any constant, for example, 10240. If the PSA is greater than the reference number, the routine continues to action 714 where the second section or high resolution look up table is used. In action 712, if the PSA is lower than the reference number, then the first section or lower resolution look up table is used.
- the lookup table thus provides the target period for spin motor 102 at a given PSA and the controller gain coefficients that are desired for stable speed control at the given radius, for example, Ki and Kp.
- the Table Index is a number corresponding to a row in lookup table 306.
- the PSA is divided by the number of PSAs per row, which may range up to about 1024.
- the low resolution spin period table is indexed by 256 PSAs per row and the high resolution spin period table is indexed by 128 PSAs per row.
- the Ki and Kp tables can be indexed by 1024 and 512 PSAs per row, respectively.
- the calculated Index is limited to the range of the table to ensure that the table limit is not exceeded for any reason.
- a check is provided to determine if the index is different than the previous index received during a previous revolution. If the table index has not changed, the routine continues 726. If the table index has changed and the lower resolution table has been used, the PSA number has to change by one count before the table index is updated. If the table index has changed and the higher resolution table has been used, the PSA number has to change by one count before the table index is updated. The index is checked for a change to reduce the firmware computation time, since in most instances the index will not have changed. No table lookup is required if the index has not changed.
- the index will remain the same between revolutions and the routine can continue to 726. However, in action 722, if the index has changed, the routine looks up a new period integrator Ki for a proportional gain Kp and puts it in global variables available to all of the modules to be used in spin control interrupt 420 (FIG. 7) and spin speed module 516 (FIG. 8).
- FIG. 10 is a block diagram of a PSA/PMAD feedback system 800 in accordance with the present invention.
- OPU 108 can travel across optical medium 106 from the OD to the ID or from the ID to the OD with optical medium 106 spinning such that the data directly under OPU 108 travels at a constant linear velocity during read and/or write operations to provide and maintain a constant data rate to R/W data processing 116.
- the PSA/PMAD values on optical medium 106 are equally spaced apart along a spiral path.
- PSA/PMAD feedback system 800 ensures that the constant linear velocity of the data under OPU 108 is maintained by ensuring that the reading of the PSA/PMAD values occur at a substantially constant rate.
- PSA/PMAD values are read from optical medium 106 and the rate at which the PSA/PMADs are read is measured.
- the measured rate is compared to a reference rate to provide a rate error.
- the reference rate can be any desired rate and once selected can be made constant. In one embodiment, the reference rate is about 2 milliseconds.
- the PSA/PMAD value is used to access a lookup table, similar in form and function to lookup table 306 described above.
- Reference data is acquired from the lookup table, which may include a proportional gain, and an integrator gain.
- an integration function is performed using the reference data and the rate error, in a manner similar to that described above, to provide an output command.
- the output command can be used to provide a drive output, which commands the voltage applied to spin motor 102 to change the spin speed of spin motor 102, as desired.
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Abstract
Description
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Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AU2002236835A AU2002236835A1 (en) | 2001-01-25 | 2002-01-18 | Spin motor control in an optical drive |
Applications Claiming Priority (16)
Application Number | Priority Date | Filing Date | Title |
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US26435101P | 2001-01-25 | 2001-01-25 | |
US60/264,351 | 2001-01-25 | ||
US09/951,108 | 2001-09-10 | ||
US09/951,325 US6898170B2 (en) | 2001-01-25 | 2001-09-10 | PMAD/PSA digital feedback system |
US09/951,108 US7065018B2 (en) | 2001-01-25 | 2001-09-10 | CLV system and method using PSA lookup |
US09/951,475 | 2001-09-10 | ||
US09/951,930 | 2001-09-10 | ||
US09/951,869 US6876609B2 (en) | 2001-01-25 | 2001-09-10 | System and method for controlling a spin motor |
US09/951,328 US6754151B2 (en) | 2001-01-25 | 2001-09-10 | BEMF timing system |
US09/951,475 US7079459B2 (en) | 2001-01-25 | 2001-09-10 | System and method for performing a spin motor startup operation |
US09/951,328 | 2001-09-10 | ||
US09/951,330 US6901040B2 (en) | 2001-01-25 | 2001-09-10 | Kp and Ki lookup system and method |
US09/951,330 | 2001-09-10 | ||
US09/951,869 | 2001-09-10 | ||
US09/951,325 | 2001-09-10 | ||
US09/951,930 US6704261B2 (en) | 2001-01-25 | 2001-09-10 | Spin motor control in an optical drive |
Publications (2)
Publication Number | Publication Date |
---|---|
WO2002059893A2 true WO2002059893A2 (en) | 2002-08-01 |
WO2002059893A3 WO2002059893A3 (en) | 2002-10-03 |
Family
ID=27575304
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/US2002/001841 WO2002059893A2 (en) | 2001-01-25 | 2002-01-18 | Spin motor control in an optical drive |
Country Status (2)
Country | Link |
---|---|
AU (1) | AU2002236835A1 (en) |
WO (1) | WO2002059893A2 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1729294A1 (en) * | 2005-05-30 | 2006-12-06 | Deutsche Thomson-Brandt Gmbh | Compact pickup for micro optical drive |
US7852714B2 (en) | 2005-05-30 | 2010-12-14 | Thomson Licensing | Compact pickup for micro optical drive |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4789975A (en) * | 1984-10-17 | 1988-12-06 | Sony Corporation | Apparatus for recording and/or reproducing data signal on or from disk shaped recording medium at a variably selected constant linear velocity |
-
2002
- 2002-01-18 WO PCT/US2002/001841 patent/WO2002059893A2/en not_active Application Discontinuation
- 2002-01-18 AU AU2002236835A patent/AU2002236835A1/en not_active Abandoned
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4789975A (en) * | 1984-10-17 | 1988-12-06 | Sony Corporation | Apparatus for recording and/or reproducing data signal on or from disk shaped recording medium at a variably selected constant linear velocity |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1729294A1 (en) * | 2005-05-30 | 2006-12-06 | Deutsche Thomson-Brandt Gmbh | Compact pickup for micro optical drive |
WO2006128767A1 (en) * | 2005-05-30 | 2006-12-07 | Thomson Licensing | Compact pickup for micro optical drive |
US7852714B2 (en) | 2005-05-30 | 2010-12-14 | Thomson Licensing | Compact pickup for micro optical drive |
Also Published As
Publication number | Publication date |
---|---|
WO2002059893A3 (en) | 2002-10-03 |
AU2002236835A1 (en) | 2002-08-06 |
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