JPS63281059A - Speed detector - Google Patents

Abstract

PURPOSE:To obtain a safe device which does not deteriorate in suppression effect owing to a change in circumferential magnetic environment by providing a fixed coil which has the same characteristics with a speed detection coil separately from it, calculating the difference between signals of both coils, and easily removing disturbance. CONSTITUTION:A moving oil 3 and a fixed magnetic circuit 4 constitute a rectilinear motor which generates driving force for moving a mobile body 1 along a guide 2. The speed detection coil 6 and a compensating coil 1 for canceling disturbance are provided on a magnetic field produced by a magnetic circuit 5 for speed detection. The coil 11 is fixed to the circuit 5 and its winding direction and its number of turns are set equal to those of the coil 6 which moves together with the mobile body 1. Further, the in-phase outputs of the coils 11 and 6 are connected in opposite-phase relation at the input stage of an amplifying circuit 8 so as to cancel each other. Then a disturbance signal resulting from peripheral magnetic variation is detected by both coils 6 and 11 with nearly equal sensitivity, but the speed of the mobile body 1 is detected by only the coil 6, so the circuit 8 outputs only a real moving speed signal after the disturbing signal is removed.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a speed detection device that detects the speed of a moving object using an electromotive force induced in a wire-wound coil.

<Prior art> A conventional speed detection device includes a magnetic circuit consisting of a permanent magnet and a yoke that generate a magnetic field, and a wire-wound coil arranged so that the winding direction coincides with the direction perpendicular to the direction of the generated magnetic field. , either the magnetic field or the coil is configured to move in a direction perpendicular to both the magnetic field direction and the winding direction, and the speed of the moving body is detected by the electromotive force induced in the winding coil.

Various types of speed detection devices as described above have already been used, such as the one shown in FIG. 4 for controlling the positioning of a recording/reproducing head of an information storage device.

In FIG. 4, 1 is a moving body equipped with a recording/reproducing head, 2 is a guide that guides the moving body 1 to a predetermined position, and the moving body l has a plurality of bearings for running on the guide. are installed. 3.4 is the mobile object l
A moving coil and a fixed magnetic circuit are used to generate the driving force to move the linear motor. 5 is a speed detection magnetic circuit fixed on the same base as the guide 2; 6 is a speed detection coil installed on the moving body 1;
1/6 is arranged so as to run in the magnetic field generated by the speed detection magnetic circuit 5.

FIG. 5 shows the configuration of a control circuit for position control, where 7 is an input control number obtained by detecting the difference between a target position (not shown) and the current position of the moving body, and 8 is an input control number obtained by detecting the difference between the target position and the current position of the moving object. An amplifier circuit for detecting an electromotive force generated by a speed detection coil on the moving body 1; 9 a variable gain differential amplifier for providing negative feedback of the moving speed of the moving body 1; 10 a moving coil of the linear motor; Shows the driver that drives the.

The minor loop of the speed detection coil/amplifier circuit/differential increaser 1/driver/linear motor in this control system is a closed servo control system for a moving body with a running mechanism as shown in Figure 4, which has low running resistance and is suitable for high-speed movement. This is effective in improving seismic motion characteristics when positioning with high precision.

FIG. 6 is a diagram showing frequency transfer characteristics between input to the moving coil 3 and displacement. As shown in the figure, the purely mechanical frequency transfer characteristic of the moving body in response to the input control signal drops at -40 dB/dec when it reaches the O-order resonance point, whereas the negative feedback of the speed signal due to the minor looseness mentioned above. In a system in which speed feedback is performed, the frequency is converted to -20 dB/dec up to the corner frequency determined by the speed feedback gain. The latter transmission characteristics are equivalent to those of a mechanical system with good damping, and the gain peak at the resonance point is eliminated, and the transmission rate of disturbance vibration in the vicinity of this point is significantly reduced, improving vibration resistance characteristics. Furthermore, when this method is used, the rotation of the phase becomes gentler and servo design becomes easier.

<Problem to be solved by the invention> In principle, in the minor loop mentioned above, the corner frequency of the transfer function can be arbitrarily changed by changing the speed feedback gain, and the mechanical characteristics can be improved as required. It is possible, but the prerequisite for this is that the speed signal can be obtained within the required frequency band. However, in reality, O disturbances other than the speed information may be mixed into the speed signal, making it impossible to obtain sufficient results. The frequency transfer characteristics between the input to the moving coil and the detected speed at this time are shown in Figure @7.

The main cause of the disturbance is the magnetic field fluctuation around the speed detection coil, and in the above example, there is a leakage magnetic flux fluctuation due to magnetic saturation of the linear motor drive magnetic circuit, or a magnetic field fluctuation due to the linear motor moving coil drive current. Furthermore, when such a control system is applied to information equipment, it is also subject to disturbances from a motor for driving a storage medium and the like. In order to prevent such disturbances and obtain a stable control system, it is necessary to make the speed detection magnetic circuit a completely closed magnetic circuit, and to take some measures against the sources of disturbances. However, the above-mentioned countermeasures mainly involve strengthening the magnetic shielding, and new problems arise such as an increase in the size of the magnetic circuit, resulting in an increase in weight and cost.

Further, if the magnetic environment changes due to a change in the design of peripheral components, the amount of disturbance will also change, so there are problems such as having to deal with it each time.

The present invention has been made to overcome the drawbacks of the conventional methods, and provides a stable speed that easily removes disturbances in the speed detection method and that does not reduce the suppression effect even if the magnetic environment around the device changes. The purpose is to provide a detection device.

Means for Solving the Problems> The present invention consists of a magnetic circuit and a wire-wound coil, and detects the electromotive force induced at both ends of the coil due to the relative displacement between the two, thereby determining the relative speed between the two. In a speed detection device for detecting a speed detection coil, a fixed coil having characteristics equivalent to that of the speed detection coil is provided separately from the speed detection coil, and the signals of the two coils are differentiated to detect the speed detected by the speed detection coil. The feature is that disturbance signals other than speed information are removed from the signal.

<Operation> The speed detection device of the present invention provides a fixed coil separately from the speed detection coil, and differentially outputs the signals of both coils, thereby detecting the disturbance signal due to magnetic field fluctuations around the speed detection device. from the signal detected by the coil.

Therefore, magnetic disturbances applied to the speed detection device can be easily removed, and high-quality speed information can be obtained even if the magnetic shielding is not complete.

<Example> Hereinafter, the speed detection device of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing the configuration of an information storage device using the speed detection device of the present invention.

In the figure, 1 is a moving body equipped with a recording/reproducing head, 2 is a guide that guides the moving body 1 to a predetermined position, and the moving body 1 is equipped with a plurality of bearings for running on the guide. has been done. 3.4 is a moving coil and a fixed magnetic circuit for generating a driving force for moving the movable body 17, and constitutes a linear linear motor.

5 is a speed detection magnetic circuit fixed on the same pace as the guide 2; 6 is a speed detection coil installed on the moving body 1; It is arranged to run in the generated magnetic field.

1 differs from FIG. 4 in that a compensation coil 11 for canceling disturbances is provided in the magnetic field created by the speed detection magnetic circuit 5, separate from the speed detection coil.

The compensation coil is fixed to the magnetic circuit 5, and its winding direction and number of windings are set to be the same as those of the speed detection coil that moves together with the moving body 1. Moreover, FIG. 2 shows the configuration of a control circuit related to the present invention. At the input stage of the amplifier circuit 8, the in-phase outputs of the compensation coil and the speed detection coil are connected in series with opposite phases so that the in-phase outputs are canceled. wired. The rest is the same as FIG. 5.

The disturbance suppression effect in the above system will be briefly explained. In a water system, it is clear from the detection principle that disturbance signals due to magnetic field fluctuations around the speed detection device are detected with approximately the same sensitivity by both the speed detection coil and the compensation coil. On the other hand, it is also clear that the moving speed of the moving body 1 is detected only by the speed detection coil.

Therefore, only the true moving speed signal from which the disturbance signal has been removed is output from the amplifier circuit 8 to which the differential signal of both coils is input.

Fig. 3 shows the frequency transfer characteristics between the input to the moving coil 3 and the detected speed, and shows the case of the embodiment according to the present invention, in which an ideal characteristic of 20 dB/dec is obtained, and The characteristic distortion in the high frequency range that can be seen with the conventional method shown in Figure 7 has been improved.

It goes without saying that the shape, sensitivity, and installation position of the compensation coil and the differential method are not limited to those of this embodiment, as long as they are set so that magnetic disturbances can be canceled. is clear. For example, the same effect can be obtained by winding the compensation coil /1/ around a yoke passing through the center of the speed detection coil. Further, although the embodiments have been described using a movable coil type, similar results can be obtained with a moving magnetic pole type.

Effect> As explained above, the present invention consists of a magnetic circuit and a wire-wound coil, and detects the electromotive force induced at both ends of the coil due to the relative displacement between the two, thereby determining the relative speed between the two. In the speed detecting device, a fixed coil having the same characteristics as the speed detecting coil is provided separately from the speed detecting coil, and the signals of the side coils are differentiated. This method removes disturbance signals other than speed information from the signal detected by the speed detection coil, making it possible to obtain high-quality speed information even if magnetic shielding is not complete, and furthermore, it is possible to obtain high-quality speed information even if magnetic shielding is not complete, and furthermore, it is possible to obtain high-quality speed information even if magnetic shielding is not complete. It is possible to provide a speed detection device that maintains the suppressing effect even when a speed detection occurs.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a schematic configuration of a speed detecting device that indicates a speed according to an embodiment of the present invention, FIG. 2 is a diagram showing a control circuit of the present invention, and FIG. 3 is a diagram showing a transfer characteristic according to the present invention. , FIG. 4 is a diagram showing the configuration of a speed detection device in a conventional method, and FIG.
Figure 6 shows a control circuit in a conventional system, Figure 6 is a diagram for explaining the effects of speed feedback on mechanical transmission characteristics, and Figure 7 is a diagram showing conventional transmission characteristics. 1. Mobile object 2. Guide 3. moving coil
4. Fixed magnetic circuit 5. Magnetic circuit for speed detection 6
．． Speed detection coil 7. Input control signal 8. Amplification circuit 9. Differential amplifier 10. Driver 11.
Compensation Coil Agent Patent Attorney Takeshi Sugiyama (and 1 other person) Figure 2 Hequenc Figure 3 Figure 4 Figure 5 Atsushi Figure 6

Claims (1)

[Claims] 1. In a speed detection device comprising a magnetic circuit and a wire-wound coil, the speed detection device detects the relative speed between the two by detecting an electromotive voltage induced at both ends of the coil due to relative displacement between the two. A fixed coil having the same characteristics as the speed detection coil is provided separately from the coil, and disturbance signals other than speed information are removed from the signal detected by the speed detection coil by differentially transmitting signals between the two coils. A speed detection device characterized by: