JPH01500383A - Preventing destruction of disk drive positioning systems - Google Patents

Abstract

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

Description

[Detailed description of the invention] □ Prevention of destruction of disk drive positioning system The present invention is directed to a positioning servo mechanism. and, in particular, operate to control a carriage moving over a high-density recording disk. related to things.

Brushwork Kasahiki For example, transducers such as those used in high-density magnetic disk drives. ・Those skilled in the art of manufacturing and using carriage positioning servomechanisms , positioning problems, especially carriage actuator “runaway” (excessively fast). We are aware of the problem of damage that can occur when moving at high speeds.

At this "runaway speed" the carriage hits the end stop and the servo There is a tendency to damage the mechanism or carriage, etc. Those skilled in the art should understand this “ We are well-versed in the means to prevent and reduce runaway behavior, such as controlling controllers or This is done by anticipating related failure conditions in servomechanisms. . The present invention is directed to this critical actuator speed problem.

As those skilled in the art are well aware, such a recording transducer on a carriage are generally extremely fragile and, moreover, are mounted on flexible structures that are also fragile. ing. The modern trend toward achieving higher recording densities on disks is Eliminate low-speed stepping motor positioning devices and replace them with higher-speed linear systems Alternatively, they prefer to use a low-pressure type actuator. these For example, the actuator of the The head positioning current operates at a speed proportional to the head positioning current under the control of commands and control signals. There are inductive types such as In particular, it is important to understand that relatively simple prevention techniques can be used. Taking this into consideration, the “runaway acceleration” and destruction of current expensive heads is expensive. The present invention is directed to these problems.

In general, the problem with one approach to solving this problem is that The approach caused the actuator to decelerate too rapidly due to a large force of 100G. It is to force This causes severe vibrations and the floating head It instantly digs into the disk surface and destroys it, causing the head and disk to fall, and the disk to break. This leads to a catastrophic situation where disk data is lost.

One approach to solving the above problem is the Bertsch patent application (= European patent application). No. 0131469, U.S. Patent Application Section 512, filed December 7, 1983, No. 873 = USP 4,553,181). In this patent application, inter alia The selected RC circuit is placed between the head positioning control servo and the head actuator. This allows maximum head speed to be maintained even when failures occur within the system. In other words, it is automatically limited to a value that prevents damage to the head. Belch The application uses passive circuitry with few reliable components. But long Additionally, element limitations degrade actuator performance and increase access time. Ma Additionally, the system in this application cannot report system failures, which could lead to Unfortunately, the Belch application also reduces the access time between tracks. A fairly expensive and reliable RC circuit is required to keep However, a higher servo output voltage is also required. In addition, Belch comes out The proposed approach does not absolutely prevent head destruction; of course, it simply limits the head speed upon collision (with a stop). Destruction at any rate is not desirable; as is well known, Han's slight head crash eventually causes serious damage.

Another approach to solving this problem is described in U.S. Pat. No. 4,375,711. disclosed herein that a similar actuator power attenuation circuit is It is designed to operate when

There are also other approaches. This approach uses an external transducer and This provides a means of preventing destruction. This app (using closed-loop speed sensing) In Roach, its detection sensitivity increases along the stroke of the linear actuator. It is set to change based on the expected speed. Failures can only be reported in a limited sense. This system will prevent collisions (unless a “stopping circuit” is added). is not possible, and the required external transducer increases the number of elements. This system essentially contains only a speed detection circuit, and therefore, to solve the destruction problem, It must be coupled to the deactivation circuit of the actuator and the carriage stop means.

Yet another approach is described in the British patent patent @GB2078030 (1981). (Published on December 23, 2016), which monitors the output level of power amplifiers that can be stopped. It includes a saturation detection circuit to detect the saturation time of the amplifier and a circuit to indicate the saturation time of the amplifier. If saturated continues for longer than a predetermined time, thereby inhibiting the amplifier input. ing. This system is capable of reporting fault conditions. Also, “Coil O It is possible to detect a “busy” condition and prevent collisions (if a “stop circuit” is added). ).

However, the Greig patent states that “the use of an oven loop servo has not been achieved. i.e., if the fault condition has not reached 100% saturation, the timer will be reset and restarted. Therefore, the actuator speed remains dangerous. It can be a state. In this system, the actuator amplifier itself is damaged. It is ineffective if the amplifier However, the carriage does not stop.

Crying bean Ω mamehi As we will discuss, this system completely prevents actuator collisions. It is "dynamic braking", and on the other hand, when the speed decreases sufficiently, , the brake is removed (and the external bias circuit makes the carriage non-data Providing something that will push you into the zone. Also, this system is a closed loop It includes a detection circuit to detect the “coil oven” condition. In a preferred embodiment , speed detector, failure detector and its latches, and actuator coil and a means for disabling the power amplifier to completely stop the actuator. It consists of a means to ...The combination of these features gives it more than ordinary advantages.

In one aspect of the invention, the system determines the “actual” actuator speed (e.g. (for example, as a back emf in the actuator voice coil) and monitor it. When this exceeds a predetermined maximum value (VAC>V-), monitor the actuator. Before the actuator hits the end stop, the actuator current is shorted and the current In combination with this, including completely shutting down the source, e.g. Shut off the buff supply to the actuator to avoid shutdown The actuator may be slowed down or attenuated. Preferably, Use rays to ignore “transients” and reduce power to simulate It may be possible to reduce the speed to a safe level without shutting down. stomach.

K plate two! single plate FIG. 1 is a block diagram of a preferred embodiment of the speed protection circuit, and FIG. 2 is a block diagram of a preferred embodiment of the speed protection circuit. Case in point diagram, Figure 3 shows a complete disk drive servo system that may be used in the subject embodiment. This is a body diagram.

Tohyuunoshashi Gojisen Plate Figure 1 shows a speed safety device (the circuit shown in Figure 2) constructed based on the principle of this system. ) is illustrated. This and other circuit means discussed in this disclosure The columns shall be understood as those well known to those skilled in the art, unless otherwise specified. Unless otherwise specified, all materials, methods, etc. It is understood that the method, device, or apparatus is implemented in a manner consistent with a preferred embodiment. It will be understood.

In principle, the apparatus shown in FIG. (for disk drive servos) the speed at which it receives input from the actuator coil a detection unit 1; a speed threshold comparison stage 2 receiving the signal from the unit 1; A latch hand that receives input from this stage 2 (along with the control microprocessor) stage 3, power amplifier disabling stage 4, delay means 6, and delay circuit 6. The system consists of a control system that includes a “crowbar activation” stage 5 that is controlled . The power amplifier disabling stage 4 and the delay means 6 receive the signal (aa) from the latch 3. receive. The speed detection unit (disk drive linear actuator) Receives the back electromotive force signal of the voice coil (from the voice coil motor VC to be driven). and in response sends a "velocity" signal vv to the velocity threshold comparison stage 2. comparison The device 2 sets the signal vv to a preset value ■. , 8, vv>■1Ill, and I's It is designed to output a signal V at the same time. The signal V arrives at the latch circuit 3. This means that the current actuator speed V@ct has exceeded Vx. Ru. Latch 3 connects this input with a predetermined microprocessor activation signal ma. is energized in response, and in response issues a “failure indication” signal aa. These signals are sent to the power amplifier disabling stage 4 and the failure notification means 8 (this (preferably part of the control microprocessor) and through a delay circuit 6. and send it to Clover Stage 5 (power cutoff).

The disabling stage 4 responsively controls a predetermined power amplifier that drives the actuator. It is understood as being adapted to render it inoperable. clover stage 5 responsively cuts off all power to the actuator and immediately stops the carriage. adapted to stop. The crowbar stage 5 preferably includes a coil V A triac or equivalent that effectively shorts the current flowing through C ( Those skilled in the art will understand that triacs are similar to low-impedance diodes connected back-to-back. A working active solid state array with a void Something that gives a very low impedance in both directions to a device like a coil. As is known to the person skilled in the art, the fault notification means 8 includes, for example For example, flags can be set to signal critical failures that require operator intervention. , used as a means of activating an alarm signal.

The operation of this embodiment can be summarized as follows.

If the actual speed of the actuator detected by the detection stage is a predetermined maximum value V, If □ is exceeded, this activates the output of comparator 2 and sets latch 3. , latch 3 is also assumed to be energized by the microprocessor input. ), and the latch 3 outputs the fault signal aa. Power amplifier disabling stage The signal aa sent to the actuator power amplifier 7 (this is the voice coil The failure signal aa, which disables (or reduces) sent to. This delay circuit 6 delays the operation of the crowbar unit 5 for a predetermined period of time.

This predetermined time is sufficient time to determine whether the "overspeeding condition" continues. In particular, the problem was solved by reducing the "disable" stage 4 to less than the actual speed V□8. That's enough time to decide what you can do.

This means that the amplifier 7 (or its peripheral circuits) is not the cause of the failure, and that the This can happen even if you are not responsible for your running speed. Even in this case, the unit crowbar unit 5 is activated after a predetermined time delay by step 6. A signal such as It is designed to stop the controller. “Detector 1 is the opposite from the coil VC By detecting the electromotive force, unsafe speeds can be detected, thus ensuring that the VC is It should be noted that it is also possible to detect whether the VC is If it is hot, its voltage will rise immediately and its current will be "O". stop If this condition is considered to be a “failure”, i.e. a “circuit oven”, etc. can be handled as such. The back electromotive force multiplied by a constant gives the actual speed. Conveniently, As shown in Figure 1, the back electromotive force is calculated from the total coil voltage to only the voltage drop IR between them. can be determined as low.

After disabling the amplifier 7 and/or activating the crowbar unit 5, The microprocessor outputs a signal to reset latch 3 as shown in Figure 1. Ru.

Those skilled in the art will understand that the power amplifier disabling stage prevents actuator collisions. and automatically when (if) the speed decreases enough. The company offers "dynamic brakes," which have brakes that are released when It is interesting to note that with this speed down, e.g. Ridges can be moved to zones with no data. This is called “closed loop loop”. This will include feedback.

This system will prevent amplifier failure and coil oven failure even if everything else fails. It also includes a crowbar unit that monitors the carriage and stops it in its tracks. It is. Those skilled in the art will appreciate that this system can be used without degrading performance or access A few simple, passive, inexpensive, high-reliability components (e.g. (See the circuit in Figure 2).

The preferred embodiments disclosed herein are merely illustrative, and the present invention Without departing from the subject matter, we are open to many variations and modifications in construction, arrangement, and use. It will be understood that it is possible to

Further variations of the invention are possible; for example, the means and techniques disclosed herein are , for other dense disk files as well as for related systems. Applicable. The present invention is also applicable to equipping other servo systems. It is.

international search report SA　21930

Claims (12)

[Claims] 1. The actuator means including the drive coil means CL is used to drive the disk. a disk drive for controllably moving a servo arm means that moves over the rack; servo system, the system comprising: safety adapted to reduce actuator speed below a predetermined target speed Vt; The actual speed of the actuator at any moment during operation means A for detecting the degree Vact; Compare Vact with target speed Vt, and when Vact > Vt, output an alarm in response. A voltage drop between the means B for outputting the signal SA and the coil means CL in response to the output SA. and means C for substantially eliminating the lower part. 2. The safety device reduces the power input to the coil means CL in response to the occurrence of the output SA. Claim 1, characterized in that the actuator means is decelerated by a small amount. servo system. 3. A latch means L is provided at the output position of the comparison means B, and the means L receives the signal SA. in response to the received power input to the coil means CL; , adapted to substantially short-circuit the current to the coil means CL after a predetermined delay. The servo system according to claim 2, characterized in that: 4. The system includes: for providing controlled drive power to the coil means CL; power amplifier means PA, the reduction of said power input being responsive to latching means L; The operations performed by the amplifier disabling unit AD of the safety device that operates in response to the The servo system according to claim 3, characterized in that: 5. The latch means L, in response to receiving the alarm signal SA from the comparison means B, Trigger signal tt to start power reduction and coil short circuit by AD section 5. The servo system according to claim 4, wherein the servo system emits a signal. 6. The means C includes means CR for substantially short-circuiting the current flowing through the coil means CL. The servo system according to claim 1, characterized in that the servo system includes: 7. The means CR includes bidirectional low impedance means Z, the means Z transmitting an alarm signal. responds after a preset delay when receiving a signal SA and selectively connects to the coil means The servo system according to claim 6, characterized in that the servo system is arranged so that . 8. Claim 7, characterized in that the means Z consists of a "triac". servo system. 9. Means CR determines the input position to means Z for producing said preset delay. The servo according to claim 7, characterized in that it includes a delay means DL connected to the servo system. 10. The safety device is configured to control the output SA to decelerate the actuator means. reducing the power input to the coil means CL in response to the occurrence of A latching means is provided at the output position of the comparing means B, and this latching means In response to the reception, the power input to said coil means CL is reduced; to substantially short-circuit the current to the coil means CL after a predetermined delay, and the system includes , power amplifier means for providing controlled drive power to the coil means CL. PA is included, and the reduction in said power input is responsive to latching means L of said safety device. The latch means L is executed by the amplifier disabling unit AD which operates as In response to receiving the alarm signal SA from the The ninth aspect of claim 9 is characterized in that the trigger signal tt is emitted to initiate short-circuiting of the cable. The servo system described in section. 11. of the disk using actuator means including drive coil means CL. A device adapted to controllably move servo arm means moving over a track. Provides improved servo control for disk drive servo systems A method of: Detects the actual speed Vact of the actuator and compares Vact with the target speed Vt. , responsively outputs an alarm output signal SA when Vact>Vt, characterized in that the signal SA is used to substantially short-circuit the current between the coil means CL. Method. 12. In response to the occurrence of the alarm signal SA, after this occurrence, said current is short-circuited. A method for reducing the power input to the coil means CL only for a predetermined alarm period before the 12. A method according to claim 11, characterized in that the method comprises the steps of: