Track seeking using a track following loop

Abstract: An optical disk recorder includes a position servo control loop for causing a beam of radiation to faithfully follow a track on the disk, jump from a current track to an adjacent track or to a small number of tracks away from the current track. Operation of the position servo loop is altered by selectively reversing the phase of a differentiated position error signal and integrating the differentiated position error signal for comparison with a sawtooth signal for moving the beam of radiation from the current track to an immediately adjacent track under continuous position servo control. Upon reaching the adjacent track, the sawtooth signal returns to a reference potential for initiating track following. The servo error between the integrated differen­ tiated position error signal and the sawtooth signal is sufficiently small such that relaxation of the sawtooth signal does not cause any significant perturbations in the positioning servo loop operation. A velocity long seek servo can be substituted for the position servo loop for more rapid long seeks.

Description: The present invention relates to position control systems, particularly those position control systems being advantageously used with optical disk recorders. Both magnetic and optical disk recorders employ either a large plurality of concentric record tracks or a single spiraling record track. The tracks on optical disks are identified by any one of a plurality of surface configurations on the optical medium (disk). A common configuration is for the medium to have circularly concentric grooves or a single spiral groove for indicating the location of the record tracks. In both magnetic and optical disk recorders, means are provided for faithfully following an addressed one of the record tracks. When it is desired to scan a track other than the currently scanned track, a track seek operation is provided; that is, the track following is aborted and a track seek algorithm is employed. Such seeking generally uses an algorithm which causes the effective disconnection of the track following operation. In the past, when optical disk transducers were moved from a current track to an immediately adjacent track, that one track seek was colloquially referred to as track jumping. Such track jumping was often used for creating stop motion of video signals recorded on an optical disk. One of the recurrent problems of track jumping , as well as multiple track seeks, is to quickly and faithfully move from the currently scanned track to the addressed or target track, whether it be the next adjacent track or several tracks from the current track. Other track seek operations use a so called velocity loop for the track seek, then switch to a position loop for track following. Other systems provide for disconnecting the track following position loop and supply a bang bang servo set of pulses for jumping to an adjacent track in a so called open loop mode, i.e., the position error feed back is disconnected. Yet other algorithms employ a single servo loop for both track scanning (following) and track seeking. The King et al., U. S. Patent 2,843,841, shows an optical disk recorder employing phase encoded recording of binary data. King et al. used an open loop pulse for moving the electron beam from scanning a current track to scan an adjacent track. The open loop pulse deflects the beam toward the second adjacent track more than one-half way, whereupon the pulse is terminated. Then the track following position control system takes over and finishes the movement of the beam to the adjacent target track. King et al. in the position controlling loop do track following using a so-called grey scale. The data tracks are radially spaced apart on the disk with alternate opaque and transparent track position indicators lying between the data tracks. The data track bits on one side of either an opaque or transparent strip are called upsticking bit, while the bits in a track on the other side of the opaque or transparent strips are called downsticking bits. When the position loop is scanning the upsticking bits, then a reduction of light indicates that the beam is too close to an opaque strip in a first or down direction. However, when the beam is scanning the second track on the opposite side of the opaque strip, then a reduction in light indicates a track deviance in an up or opposite direction. Accordingly, when the beam is moved from one side of an opaque strip to the other side, the sense of the position error track following loop is reversed. The same procedure is followed in switching from a track over a transparent strip. The operation of track jumping in King et al. finds the open loop pulse moving the beam more than half way between the two adjacent tracks. Before termination of the open loop pulse, the sense of the track following loop is reversed. The track following position error signal has a one-half cycle of vibration when the beam is switched from a current track to an immediately adjacent track. The King et al. system appears to be satisfactory for relatively low track densities, but is not satisfactory for the higher track densities contemplated for the present day optical disk recorders. An improvement over the King, et al. system is shown in U. S. Patents 3,473,164 and 3,480,919 to Jensen et al. Rather than having concentric circular tracks as in King et al., Jensen shows a linear raster of tracks, but using the same data track configuration. With particular reference to Fig. 5 of U. S. Patent 3,480,919, it is seen that the King, et al. open loop pulse is replaced by a clamping operation in a differential position error signal loop which forces the electron beam to move in one direction or another toward a second adjacent track. At the same time the clamping action is provided, the sense of the track following position sensing loop is reversed. when the electron beam is about halfway in its movement from the current track to an adjacent track, the clamping is removed. The track following loop completes the movement of the beam to the target adjacent track. This new arrangement provided for a more faithful jump from a current track to an adjacent track. However, the data format is the same and tends to limit the track density of the optical tracks; hence, it is not necessarily suitable for present day contemplated optical disks. Patent Reissue, 32,051 shows track jumping in a video recorder wherein the position error signal produced while traversing between two adjacent tracks is a sinusoidal. The zero crossing of the sinusoid at the midpoint between the track causes termination of a jumping pulse. The jumping pulse disconnects the track following loop from an actuator, whole in turn is reconnected after the beam has moved more than one-half way from the current track to the target adjacent track. Compensation pulses are provided at the terminous of the jump for reducing overshoot and beam settling time. In acquiring the tracking mode on the adjacent target track it is desired to provide a simpler, but more effective track jumping than provided by the reissue patent. Patent Reissue 32,051 discloses a servo positioning system, a data recorder and a method of operating according to the preambles of claims 1,7 and 10 respectively. Hirano, U.S. Patent 4,613,963 shows another open loop jumping circuit which requires a plurality of beams for achieving the open loop jump. It is desired that the use of a plurality of radiation beams be avoided when controlling track following and track seeking. Matla in U.S. Patent 4,217,612 shows a servo system which uses the same servo loop for both track following or scanning and track seeking. The command signal input into a scanner is changed to switch from track seeking to following. This arrangement will not work in systems not employing a simulator. It is an object of the present invention to provide track traversing from one track to a second track while maintaining the operation of a track following loop by selectively altering the operation of loop. Viewed from a first aspect the present invention provides a servo positioning system having a carriage for carrying an object to selectively position the object over one of any one of a plurality of spaced apart reference lines, a position detector for sensing and indicating the relative position of the object with respect to a closest one of the reference lines, the position detector supplying a position error signal indicative of the positional relationship of the object with respect to a closest one of said reference lines and supplying a sinusoidal signal alternation each time the object traverses a space between adjacent ones of the reference lines, the system being characterized by: jump control means for supplying a reference line following signal for indicating keeping the object over a current one of the reference lines and a jump command signal for indicating a desired movement of the object from the current reference line to a second reference line spaced from the current reference line, differentiating means connected to the position detector for receiving the position error signal and differentiating the position error signal to create a differentiated error signal, a servo driver means electrically interposed between said carriage, jump control means and the differentiating means for electrically coupling said differentiating means to said carriage for actuating the carriage to position the object with respect to the current reference line or a second reference line in response to the differentiated error signal, the reference line following signal and the jump command signal, and phase change means connected to the differentiating means and the jump control means for reversing the phase of the differentiated error signal when the object is traversing between the current and the second reference line by reversing the polarity of the differentiated error signal between zero crossings thereof occurring intermediate the current and second reference lines, the phase change means being coupled to the servo drive means for supplying the reversed phase signal thereto. Viewed from a second aspect the present invention provides a data recorder having a rotatable disk for storing signals to be sensed and recorded, a carriage radially movable with respect to a recording surface on the disk, and having signal transducer means in transducing relationship to the recording surface, actuator means coupled to the transducer and carriage for positioning same radially of the disk and for causing the transducer means to faithfully follow a track on the disk and for faithfully changing tracks on the disk in response to commands, position detector coupled to said transducer means for sensing the relationship of the transducer to a track being followed and to adjacent tracks during a track traversal mode of operation and supplying a position error signal indicative of the relative radial position of the transducer means to the tracks on said record disk, the position error signal being a sinusoid when traversing a track with a zero crossing of the sinusoid indicating such track crossing, characterized by signal differentiating means coupled to said position detector for receiving the position error signal and supplying a differentiated position error signal which is first differential of the position error signal, a signal integrator electrically coupled to the output of the differentiating circuit for receiving the differentiated position error signal and for supplying an output integrated error signal, a voltage reference source supplying a reference signal, a jump signal generator connected to the integrator for supplying a square wave to the integrator for integration with said differentiated position, an analog summer circuit having first and second inputs, the first input coupled to the signal integrator and receiving the output integrated error signal and the second input coupled to gating means for receiving the reference signal the summer circuit being subtractively responsive to the two signals for supplying a servo output error signal, servo driver means coupled to the output of the summer circuit and to said actuator means for positioning the transducer means in accordance with the combination of the reference signal, and the output integrated error signal, phase change means electrically interposed between the output of the differentiating circuit and the input of the signal integrator and operative to supply a differentiated position error signal or an inverted differentiated position error signal to the signal integrator, jump control means coupled to said jump signal generator for causing the jump signal generator to supply the square wave to the integrator and coupled to the phase change means for actuating the phase change means to supply the inverse of the differentiated position error signal between predetermined zero crossings of the differentiated signal during the time the transducer means is traversing from one track on the disk to an immediately adjacent track on the disk wherein the signal reversal is in the middle one-half portion of the spacing between the adjacent tracks, and means in the jump control means for terminating the jump signal when the adjacent track is reached. A track following loop supplies a position error signal for facilitating track following within a position control loop. The position error signal goes through one cycle of vibration or alternation when a light beam controlled by the position error loop causes the beam to traverse from one track to an adjacent track. The position error signal is differentiated then integrated for supplying a control signal for both track seeking and following. A servo circuit during track following causes the loop to servo to a given reference potential, such as ground reference potential. For a traversal of the light beam from one to an adjacent track, a ramp (or sawtooth) command signal replaces the reference potential and has a polarity indicative of the direction of jump. The sawtooth signal causes the position servo control loop to move the radiation beam away from a current track toward an immediately adjacent track. The signal polarity of the differentiated position error signal is similar to the polarity of the sawtooth command signal during the first and last fourth of the position error signal vibration. The intermediate or central portion of the differentiated position error signal has its polarity reversed such that signal fed to the summer is derived from the position error signal that always has the polarity like that of the sawtooth command signal. Upon reaching the adjacent track, the sawtooth returns to ground reference potential. Upon reaching a track center line, the integrated signal in integrator 64 is quickly discharged for quickly removing the integrated signal from the servo loop. The operation of the loop is such that the error signal produced by the summer circuit during traversal between the tracks is kept relatively small such that insignificant, if any, transients are produced in the position servo loop by the sawtooth signal returning to ground reference potential. Using the position servo loop for both following and track jumping, can be for moving from one track to an adjacent track or for stepping between plurality of tracks, such with multiple sawtooth command signals (no limitation thereto intended), one command signal for traversing from one track to an adjacent track. The position servo loop can be advantageously employed for track seeking a relatively small number of tracks and be combined with a velocity loop for enabling seeking over a relatively large number of tracks. The foregoing and other objects features, and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings. Fig. 1 is a simplified diagrammatic showing of an optical disk recorder incorporating the teachings of the invention with that portion of the recorder illustrating the operation of the invention being accented and more complete than the showing of the remainder of the recorder. Fig. 2 is a set of graphs representing signals used to describe the operation of the Fig. 1-illustrated recorder. Fig. 3 illustrates a combined integrator and ramp generator usable in Fig. 1-illustrated apparatus. Referring now to the appended drawing like numerals indicate like features and structural elements in the drawing. Optical disk recorder 10 records and reads signals on and from optical record disk 11. Disk 11 is mounted for rotation on spindle 12 of disk rotating motor 13. Motor 13 is operated at a constant angular speed; when video signals are recorded, motor 13 is operated at a constant track lineal speed on disk 11 irrespective of the radial position of the track. Recorder 10 has a frame diagramatically represented by numeral 14 for suitably mounting all of the components of the recorder. Carriage 15 is mounted on frame 14 for reciprocating radial motions with respect to a record surface of disk 11. Objective focusing lens 16 is mounted on the distal of carriage 15 for supplying a beam of radiation to disk 11 and for receiving a reflected beam of radiation from disk 11. Lens 16 is supported by a focus and tracking fine actuator 17 of usual design. Fine actuator 17 moves objective lens 16 perpendicular to the surface of disk 11 and along the axis of a light path for focusing operations, and moves the objective lens linearly radially for performing tracking operations and for causing the beam of radiation to move from a currently scanned track of disk 11 to a second track of disk 11. The second track may be the immediately radially adjacent track or may be separated by several intermediate record tracks. Carriage servo 18 mounted on frame 14 is mechanically coupled to carriage 15 as indicated by dash line 19. Carriage servo 18 controls the radial position of carriage 15, a later described position error servo loop which controls fine actuator 17, has its operation coordinated with that of carriage servo 18 so that carriage 15 tends to position itself for enabling the objective lens 16 to be centered in its range of radial movement with respect to disk 11. The optics carried by carriage 15, which are in optical communication with lens 16, can be of the usual design. For purposes of brevity, beam splitter 22 is intended to represent all of the optics carried by carriage 15. Such optics may be those optics known for use with various forms of optical recording on disk 11. Such recording includes embossed recording, phase change recording, magneto-optic recording, polymer dye recording and the like. Laser light source 23 mounted on frame 14 supplies a collimated light beam of radiation over light path 24 to optics 22. Optics 22 directs a portion of the light through objective lens 16 to disk 11 for recording and reading signals. The light reflected from disk 11 passes into optics 22, thence over light path 25 for data detection, focus detection and the like. A portion of the reflected light is transmitted over light path 26 to be reflected by mirror 27 to a pair of photo-cells (PC) 28. The light travelling over path 26 contains track position indicating distortions of the reflected light beam as is known in the optical recording art. The photo-cells 28 detect a difference in light intensity on one photo-cell from another for indicating track following offsets, as is well known. Detector (DET) 29 receives electrical signals from PCs 28 for generating a position error signal (PES) which it supplies over line 30. Position error signal (PES) 35 is representative of the output of detector 29 during traversal of the beam of radiation from the center of a current track being scanned 36 and an immediately adjacent track having centerline 37. PES 35 is shown as being sinusoidal and which is spatially related to the track centerlines 36 and 37. Please note that the signal 35 is not represented in the time domain. The servo pulse 38 results in a radiation beam radial velocity represented by velocity curve 39. The operation of the track following position servo loop is next described together with the change in operation for achieving track jumping/seeking. Differentiator (DIFF) 44 receives PES 35 to supply a differentiated position error signal PES′ 43 over signal line 45. PES′ 43 has relatively negative polarity signal portions in the quarter portions of the intertrack systems between lines 36 and 37, which is a polarity suitable for comparing with a command signal for traversing the radiation beam to target adjacent track centerline 37. A center part 46 of PES′ disposed between the quarter track points 56 has a signal polarity which when combined in the summer 65, as later described, tends to move that radiation beam back towards the current track. To avoid this problem, at the zero crossings 56 the polarity of the center portion 46 of PES′ is reversed to appear as dash line 47. In this manner, all of PES′ signal 43 positions between lines 36 and 37 have the same polarity. To achieve the track traversing, servo command signal 48 in the shape of a sawtooth wave, is combined with PES′ signal 43 (as integrated) in later described summer circuit 65. The resultant servo error signal resulting from combining signal 48 with modified signal 43 is represented by sawtooth signal 49. The switching of polarity at the quarter track points 56 results in minor perturbations 50 in the servo error signal. Suitable compensation in the position servo loop removes any negative effect of such perturbations. Circuit 53 receives PES′ and converts PES′ 43 to a unipolar signal having the line 47 indicated phase reversal of the center portion of PES′. Electronic switch 54 switches the output signal of circuit 53 between PES′ line 45 and an inverted PES′ signal supplied by analog signal inverter 61 in synchronism with zero crossings 56. Synchronism is achieved by zero crossing circuit (0X) 55 generating output pulses in response to the zero crossings 56 which are supplied over line 59 to AND circuit 57. AND circuit 57 is enabled to pass the zero crossing pulses by an enabling (jump) signal, later described, received over line 58. AND circuit 57 controls electronic switch 54, as indicated by dash line 60, to move between the two illustrated terminals for selectively connecting analog inverter circuit 61 into the position control loop. Zero crossing detector 55 identifies all of the zero crossings of PES′. The AND circuit 57 under control of the jump signal on line 58 permits only two zero crossings 56 to pass to electronic switch 54 for switching to inverter 61. The second zero crossing actuates switch 54 to reconnect line 45 directly into the servo loop. Switch 54 supplies PES′ signal as selectively reversed to signal integrator 64. Integrator 64 supplies an error signal into analog summer 65. Summer 65 takes the later described reference signal and combines it with the error signal to supply servo position feedback signal 49 through the electronic switch 80; thence, power amplifier 81 over line 82 to fine actuator 17. The reference voltage VR, which may be ground reference potential, is continuously supplied over line 66 to summer 65. During track following the objective lens 16 is centered on a current track being scanned. When line 58 is carrying a jump signal, AND circuit 67 is enabled to pass the ramp generator 68 signal 48 to summer 65. Line 58 may be coupled to generator 68 for enabling the generation of repetitive servo ramp signals 48. At this point in time it should be noted that the polarity of the servo command signal 48 determines the direction of jump. A direction signal supplied over line 70 from a control unit (not shown) determines the direction of jump. Generation of such jump direction signals is so well known it will not be further discussed. The output of analog summer circuit 65 is supplied to compensation circuit COMP 69, which is a design using known position servo design techniques. The generation of jump signal appearing on line 58 is next described. The first step is for the program control (not shown or described) to supply a count set signal over line 72 to counter COUNT 73. For a one track jump the counter is set to two. Once the counter 73 is set, then the program control supplies a jump initiate signal over line 75 to jump flip flop or bistable circuit 76. On being set, jump circuit 76 supplies the jump command signal over line 58, which initiates generator 68 supplying the servo command signal 48 to the summer 65 reference input, closes AND circuit 66 and opens AND circuit 67, and enables AND circuit 57 to pass zero crossing signal 56 to electronic switch 54. Zero crossing (0X) detector 74 responds to the zero crossings of PES signal 35 at the midpoint between center lines 36 and 37 and upon reaching line 37. Subtracting two from the numerical contents of counter 73 when counter 73 equals 0, and it supplies an AND circuit enabling signal to AND circuit 77 permitting the next occurring zero crossing signal (at center line 37) to pass to reset jump circuit 76 for removing the jump enabling signal from line 58. The above description shows how a position servo loop used for track following is effectively and simply used for track jumping and for a plurality of track jumps for enabling short seeks to be successfully completed. Track seek mode switch 80 is selectively actuated to switch in the just described position servo loop or to use a velocity long seek servo, as next described. Velocity seek servo 83 is initiated by receiving a seek command over line 84 from the program control using known techniques. Velocity seek servo 83 responds to the received command, which includes a number of tracks to be crossed for reaching a target track, to electronically control the switch 80 to switch from the just described position servo loop to the alternate terminal which couples the velocity seek servo 83 output signal to power amplifier 81. This signal also travels over line 82 to fine actuator 17. The velocity control signal on line 82 also travels to carriage servo 18 for moving carriage 15 on the long seek. Line 85 couples fine actuator 17 to carriage servo 18 for indicating the relative position of fine actuator 17 with respect to carriage 15 such that carriage servo 18 can respond for trying to center objective lens 16 at its midpoint of radial travel with respect to carriage 15. Operation of velocity servos are well known and not further described for that reason. An example of a two unit servo wherein one actuator is carried by the other and the carrying actuator follows the carried actuator (the fine actuator also called a topper actuator) is shown in expired U. S. Patent 2,717,979. The supplying of address signals and switching between position track following and seeking modes is shown in the McIntosh, et al., U. S. Patent 3,924,268. Fig. 3 illustrates a simplified circuit for generating a jumping control ramp signal. The control ramp is generated within integrator 64 rather than by a separate ramp circuit 68. Summer 65 continuously receives the reference voltage VR. Square wave generator 100 is actuated by the line 58 circuit to generate a square wave with a polarity indicated by the line 70 jump direction signal. The duration of the square wave is comparable to the duration of the ramp signal 48. This square wave is analog OR′d with the switch 54 tracking error signal at the input of integrator 64. Integrator 64 integrates the OR′d signal to output a pseudo error signal identical to signal 48 (Fig. 2) resulting in a drive signal output from summer 65 causing a jump. Subtracting the pseudo error signal from VR results in an identical drive signal as described for the ramp generator 68. Note that, because of the subtraction, for a given direction of track jumping the polarity of the square wave is opposite to the ramp signal 48. Fig. 3 is the preferred embodiment for the jump signal generation.

Claims: A servo positioning system having a carriage (15) for carrying an object to selectively position the object over one of any one of a plurality of spaced apart reference lines, a position detector (28, 29) for sensing and indicating the relative position of the object with respect to a closest one of the reference lines, the position detector supplying a position error signal (35) indicative of the positional relationship of the object with respect to a closest one of said reference lines and supplying a sinusoidal signal alternation each time the object traverses a space between adjacent ones of the reference lines, the system being characterized by: jump control means (58, 76) for supplying a reference line following signal for indicating keeping the object over a current one of the reference lines and a jump command signal for indicating a desired movement of the object from the current reference line to a second reference line spaced from the current reference line, differentiating means (44) connected to the position detector (28, 29) for receiving the position error signal (35) and differentiating the position error signal to create a differentiated error signal (43), a servo driver means (81) electrically interposed between said carriage (15), jump control means (58, 76) and the differentiating means (44) for electrically coupling said differentiating means to said carriage for actuating the carriage to position the object with respect to the current reference line or a second reference line in response to the differentiated error signal (43), the reference line following signal and the jump command signal, and phase change means (53) connected to the differentiating means (44) and the jump control means (58, 76) for reversing the phase of the differentiated error signal (43) when the object is traversing between the current and the second reference line by reversing the polarity of the differentiated error signal between zero crossings thereof occurring intermediate the current and second reference lines, the phase change means (53) being coupled to the servo drive means (81) for supplying the reversed phase signal thereto. A servo positioning system as claimed in claim 1, wherein said jump control means (58, 76) includes a jump signal generator (76) for supplying the jump command signal, a reference line counting means (74) coupled to said position detector (28, 29) for receiving said position error signal (35) and counting the number of reference lines traversed so as to determine arrival at a target reference line, the reference line counting means being coupled to said jump signal generator for turning off the jump signal generator, and the system further comprising: a bi-polar ramp generator (68) responsive to the jump command signal and a direction signal over line (70) for supplying a positive or negative ramp signal, said jump signal generator (76) being coupled to said phase change means (53) for enabling same to reverse the phase of the differentiated error signal (43), a voltage reference source for supplying a reference signal (V R ), and signal combining means (64, 65) connected between said servo driver means (81) and said differentiating means (44), and responsive to said jump control means (58, 76), for combining said differentiated error signal (43) or said reversed phase signal with said ramp signal to generate a ramp-shaped servo drive signal (49) for effecting the jumping of the object to said second reference line. A servo positioning system as claimed in claim 1, comprising: a square wave generator (100) connected to the jump control means (58, 76) for generating said jump command signal as a square wave signal, an integrator (64) coupled to the differentiating means (44) for receiving said differentiated error signal (43) or said reversed phase signal and coupled to the square wave generator (100) for receiving the jump command signal for generating an integrated signal from the received signals, a summer circuit (65) coupled to the integrator for receiving said integrated signal and the voltage reference source for receiving said reference signal (V R ), the summer circuit (65) combining the reference signal (V R ) with said integrated signal for supplying a drive control signal for controlling said carriage (15), the jump command signal being coupled to said square wave generator and to said phase change means for simultaneously actuating same for effecting a jump motion by the carriage. A servo positioning system as claimed in claim 2, further comprising: an integrator (64) in the signal combining means coupled to the differentiating means (44) for receiving and integrating said differentiated error signal (43) or said reversed phase signal to supply an integrated error signal, a summer circuit (65) in the signal combining means coupled to the integrator for receiving the integrated error signal and coupled to the jump control means (58, 76) and the ramp generator (68) for receiving said reference line following and jump command signals for subtractively combining the integrated error signal with either the reference signal (V R ) or the ramp signal for generating a drive control signal for the carriage (15) for controlling same, and the jump command signal being coupled to the ramp generator (68) and to said phase change means (53) for simultaneously actuating same for effecting a jump motion by the carriage (15). A servo positioning system as claimed in any of claims 2 to 4, wherein said phase change means (53) comprises: input means connected to said differentiating means (44) for receiving the differentiated error signal (43), an analog signal inverter (61) having an input connected to said input means for receiving the differentiated error signal (43) and having an output terminal, an electronic switch (54) having an output coupled to said signal combining means (64, 65) and having first and second inputs respectively connected to said input means and to the output of said analog inverter (61) and having a control input, a zero crossing detector (55) coupled to said input means for supplying an output signal each time the differentiated error signal (43) has a zero access crossing, and actuating means (57) coupled to the control input of said electronic switch (54) for selectively actuating same between the output of said inverter (61) and said input means and keeping the input of the switch connected to the input means as a default setting, the actuating means being coupled to said zero crossing detector (55) for responding to the first zero access crossing signal to actuate the electronic switch (54) to receive the output signal from the inverter (61) and being responsive to the second received zero access crossing signal to return the switch to said input means. A servo positioning as claimed in claim 5, further comprising: gating means (66, 67) electrically interposed between said voltage reference source, said ramp generator (68) and said summer circuit (65) for selectively coupling either the reference signal (V R ) or the ramp signal to said summer circuit (65), and the jump signal generator (76) being coupled to said gating means and to said phase change means (53) for supplying the jump command signal whereby the phase change means (53) selectively switches the electronic switch (54) between the input means and the output of the inverter (61) at the differentiated error signal (43) zero crossings and the gating means (66, 67) supplies the ramp signal to the analog summer circuit (65) in place of the reference signal (V R ), said jump signal generator further being operable to terminate the jump command signal, whereby said gating means blocks the ramp signal from said analog summer circuit (65) and replaces same with the reference signal (V R ). A data recorder having a rotatable disk (11) for storing signals to be sensed and recorded, a carriage (15) radially movable with respect to a recording surface on the disk (11), and having signal transducer means in transducing relationship to the recording surface, actuator means (17, 18) coupled to the transducer (16) and carriage (15) for positioning same radially of the disk and for causing the transducer means to faithfully follow a track on the disk (11) and for faithfully changing tracks on the disk in response to commands, position detector (28, 29) coupled to said transducer means for sensing the relationship of the transducer to a track being followed and to adjacent tracks during a track traversal mode of operation and supplying a position error signal (35) indicative of the relative radial position of the transducer means to the tracks on said record disk (11), the position error signal being a sinusoid when traversing a track with a zero crossing of the sinusoid indicating such track crossing, characterized by signal differentiating means (44) coupled to said position detector (28, 29) for receiving the position error signal and supplying a differentiated position error signal which is a first differential of the position error signal, a signal integrator (64) electrically coupled to the output of the differentiating circuit (44) for receiving the differentiated position error signal and for supplying an output integrated error signal, a voltage reference source supplying a reference signal (V R ), a jump signal generator (100) connected to the integrator for supplying a square wave to the integrator for integration with said differentiated position error signal, an analog summer circuit (65) having first and second inputs, the first input coupled to the signal integrator (64) for receiving the output integrated error signal and the second input coupled to gating means (66) for receiving the reference signal (V R ), the summer circuit (65) being subtractively responsive to the two signals for supplying a servo output error signal, servo driver means (81) coupled to the output of the summer circuit (65) and to said actuator means (17, 18) for positioning the transducer means in accordance with the combination of the reference signal (V R ), and the output integrated error signal, phase change means (53) electrically interposed between the output of the differentiating circuit (44) and the input of the signal integrator (64) and operative to supply a differentiated position error signal or an inverted differentiated position error signal to the signal integrator (64), jump control means (58, 76) coupled to said jump signal generator (100) for causing the jump signal generator to supply the square wave to the integrator (64) and coupled to the phase change means (53) for actuating the phase change means to supply the inverse of the differentiated position error signal between predetermined zero crossings of the differentiated signal during the time the transducer means is traversing from one track on the disk (11) to an immediately adjacent track on the disk (11) wherein the signal reversal is in the middle one-half portion of the spacing between the adjacent tracks, and means (74) in the jump control means for terminating the jump signal when the adjacent track is reached. A data recorder as claimed in claim 7 wherein said transducer means is an optical system (16, 22, 23) on the carriage, the transducer means including an objective leans (16) with a fine actuator (17) controlled by the data recorder for controlling a beam of radiation to impinge upon the record surface track in a predetermined manner with said position detector (28, 29) including optical means optically coupled to said optical system (16, 22, 23) for receiving a beam of radiation reflected from the disk for detecting the relative position of the beam of radiation with respect to closely radially adjacent tracks on the disk (11), said position detector (28, 29) supplying a single cycle of alternation in the position error signal whenever the transducer means traverses from a current track to an immediately adjacent track, said differentiating circuit (44) supplying a differentiated position error signal having zero crossings at quarter points of the intertrack spacing between two adjacent track centerlines on the disk, and said phase change means (53) changing the phase of the differentiated position error signals intermediate to quarter track points each time the transducer means is traversing from one track to an adjacent track. A data recorder as claimed in claim 8, further including means in said jump control means (58, 76) for actuating the data recorder to successively jump a plurality of tracks. A method of operating an optical disk recorder having a rotatable disk (11) for storing signals to be sensed and recorded, a carriage (15) radially movable with respect to a recording surface on the disk (11), and signal transducer means in transducing relationship to the recording surface, the method comprising the steps of: positioning the carriage radially of the disk so as to cause the transducer means to faithfully follow a track on the disk (11) and for faithfully changing tracks on the disk in response to a jump command; sensing the relationship of the transducer to a track being followed and to adjacent tracks during a track traversal mode of operation; supplying a position error signal (35) indicative of the relative radial position of the transducer means to the tracks on said record disk (11), the position error signal being a sinusoid when traversing a track with a zero crossing of the sinusoid indicating such track crossing; the method being characterisd by the steps of: calculating, in response to the position error signal, a differentiated position error signal which is a first differential of the position error signal, providing a square wave for integration with said differentiated position error signal, supplying the input of an integrator with either the differentiated position error signal or an inverted differentiated position error signal, the inverted differentiated position error signal being provided between predetermined zero crossings of the differentiated signal during the time the transducer means is traversing from one track on the disk (11) to an immediately adjacent track on the disk (11) wherein the signal reversal is in the middle one-half portion of the spacing between the adjacent tracks, determining in the integrator, in response to either the differentiated position error signal or the inverted differentiated position error signal, an output integrated error signal, providing a reference signal (V R ), determining a servo output error signal by combining the output integrated error signal and the the reference signal (V R ), positioning the transducer means in accordance with the combination of the reference signal (V R ) and the output integrated error signal, and terminating the jump command when the adjacent track is reached.

Inventors: FENNEMA ALAN AUGUST, FENNEMA, ALAN AUGUST
Applicants: IBM, INTERNATIONAL BUSINESS MACHINES CORPORATION
Application year: 1988
Main classification: G11B21
IPC codes: G11B7, G11B21