JPS61292502A - Absolute position detector - Google Patents

Abstract

PURPOSE:To enable detection of the absolute position in an extensive range, by differentiating magnetic pitches magnetized on a scale by the specified width and also, by installing a plurality of detecting heads. CONSTITUTION:Pitch distances of magnetic poles N, S of the primary coil 17 are changed in due order with an increment DELTAl, that is to say, they are arranged with the between-pitch distances l, l+DELTAl, l+2.DELTAl.... The secondary dielectric body 13 is provided with a linear motor runner 16, detecting heads 14 and 15 as an integral body, and they are positioned parallel to the coil 17 with an infinitesimal gap. And, to the heads 14, 15, exciting currents ISinomegat and ICosomegat are supplied and respective output signals are phase-detected as voltages provided with the phases proportional to their displacement distances and become output signals DS1 and DS2. These signals represent the maximum values in the displaced distances deviated by the increment DELTAl respectively, and they show the absolute values only in the range of a single pitch of the magnetic pole. Consequently, by the arithmetic operations of these 2 output signals, the displacement of the dielectric body 13 is detected as the absolute value.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to an absolute position detection device for detecting the absolute position of a linear motor used in a positioning device or the like.

(Technical background of the invention and its problems) A beam near motor is generally used in the positioning system used in machine tools, etc., but the position detection unit, which is the most important element of this system, has various types. Means are being considered.

Among these, the conventionally used magnetic scale has the advantage of being relatively inexpensive and capable of easily detecting the position.

Figure 6 shows the principle structure of this magnetic scale.
A scale 1, which is magnetized at a pitch P on a magnetic film coated or plated on a scale base 2, and a detection radar 3 for reading the scale are opposed in parallel with a small gap in between. And, the detection head 3 has a saturable iron core 4.
and 5 are arranged at a pitch of 2/1, respectively, and excitation MA wires 6 and 7 are wound around these saturable iron cores 4 and 5, and output windings 8 and 9 are wound around them, respectively.

With this configuration, l5rnωt is applied to the excitation winding MA6.

When an excitation current rcasωt is supplied to the excitation winding 7,
The phase of the signal magnetic field received by the two saturated iron cores 4 and 5 is 2.
/! Since the pitch is shifted by 90°, the output af
Output signals eO1 and eo? obtained from f18 and 9? teeth.

However, the moving distance of X-niscale Eo: Maximum value of output voltage The output voltage e of this magnetic scale is as follows.

is obtained by combining eel and 802, and from equations (1) and (2) above, eQ! Since eoI+802, the moving distance X of the scale l can be obtained from equation (3) by detecting the phase using the excitation voltage Sinωt as a reference. Here, if the output signal obtained by detecting one phase is assumed to be OS, an output characteristic as shown in FIG. 7 will be obtained, and the moving distance of the scale l can be taken out as the output signal.

However, 1: the above-mentioned detection device can only measure the absolute position within the l pitch range, and the scale l
It has the disadvantage that it cannot be detected absolutely over a large movement range, but only as incremental positions. There is also a method of arranging a large number of detection heads over the entire movement range, but this not only increases the size of the device but also increases the cost.

(9. Aim of Ming) This invention was made under the above circumstances,
An object of the present invention is to vary the magnetic pitch magnetized on the scale by a predetermined width and to provide a plurality of detection heads.

An object of the present invention is to provide an absolute position detection device capable of detecting an absolute position over a wide range.

(Summary of the Invention) The present invention relates to a position detection device for a linear motor consisting of a primary winding and a secondary conductor that face each other at a predetermined interval and are movable in parallel to each other. The absolute position l can be detected by making the widths different and by providing a secondary conductor portion which is integrated by adding a plurality of detection heads to the secondary conductor.

(Embodiment of the invention) Fig. 3 (A) To explain the concept of the beam near motor,
This diagram shows the principle of the primary winding (stator) 11 and secondary conductor (rotor) 12 in an induction motor, and Figure (B) shows this induction motor developed into a linear motor. Due to the magnetism generated by the primary winding 11, the primary winding 11A is formed by opening S into a flat plate, and the secondary conductor 12A is formed by opening the secondary conductor 12 into a flat plate. This invention adds the above-mentioned detection head to this secondary conductor 12A, and
By utilizing the magnetism of the next winding 11A, this linear motor and a magnetic scale are integrated to detect the position of the linear motor.

FIGS. 1(A) to 1(C) show an embodiment of the present invention and its operation. FIG. 1(A) shows the primary winding (stator)! 7
The magnetic properties N and S of are changed by Il'i order with the pitch interval incremented by 2 sentences, that is, pitch interval intersection, 1◆Δdan, intersection ÷ 2
・ΔSee,..., intersection+n・2 sentences are arranged. A secondary conductor (parallel) 13 is integrally constructed with a near motor running element 1G and two detection leads 14 and 15, which are parallel to the primary winding 17 and facing each other across a small gap. It has become so. Then, for detection, 14 and 15, l5inωt and lC are applied, respectively.
An excitation current a5ωt is supplied, and the respective output signals e1 and e2 are obtained as voltages having a phase shift proportional to the moving distance X, as described above. These output signals e1
and e2 are phase-detected as described later and output signal DS
I and mouth S2, and the detection characteristics are as shown in (B) and (G) in the same figure. Here, the detection helad 14 is one after the other jl
The detection head 15 is arranged so as to match one side end of the magnetic pole, which is the minimum pitch of the magnetic field of the i17, and the detection head 15 is arranged so that the pinch interval of the magnetic field of the primary winding 17 is (alternative ◆2. ) are distributed in a relationship that matches the starting point.

FIG. 2 shows the block configuration of the phase detection device, in which an AC excitation power source 21 is supplied to two detection radiators 14 and 15, excitation windings M22 and 23 with excitation currents l5inω and Icosωt, respectively.

Output signals e1 and e are output from the output S lines 24 and 25, respectively.
2 is induced. By detecting the phases of these output signals 81 and e2 by phase detection circuits 26A and 28B, the output signals 81 and e2 are converted into signals corresponding to the moving distance of the secondary conductor 13.
The output signals DSI and DBP are converted into digital signals and output as output signals DSI and DBP. These output signals DSI and DBP are input to the arithmetic processing section 28, and predetermined arithmetic operations are performed.

Note that the output signals DSI and DBP obtained here are as follows:
As shown in Fig. 1 (B) and (C), the maximum value is shown at the movement distance where the increment Δ is misaligned, and it is only m8
Since the absolute value is only shown within the range of 1 pitch of i, the procedure for determining the absolute position using these two output signals OS+ and DBP is as follows with reference to Figures 1 (A) to (C). to be analyzed.

Now, set the maximum value of the output signals DSI and DBP to "999".
', and if the value of the output signal DSL at this time is Sl, then the moving distance PSI is as follows:
Sentence◆∆l)◆(sentence/2・ΔX>=3×(cross◆Δsentence) Therefore, as a general formula, where the number of pitches is n, lf and the moving distance *pn+ are as follows.

. . . (5) Similarly, if the value of the output signal 092 is 52, then the moving distance gI P n + is given by the following general formula.

(6) Here, Pnl in equations (5) and (6) are originally equal to 1.

. . . (7) By the way, equation (7) was obtained from the general equation in a state such as the moving distance fiPs1.

In reality, there may be a state with a position l relationship such as PS2. The values of the output signals DSI and DBP at this time are respectively S3
and S4, equation (5) becomes equation (8), and (8
) corresponds to equation (9) and equation (7) corresponds to equation (10), respectively, to obtain the following equation.

・・・・・・・・・(8) ・・・・・・・・・(9) Here, in equation (7) or equation (10), 5
Since l-34, l and 2 sentences are known quantities, the pitch number n
is found. In other words, by determining the pitch number n, the movement of the secondary conductor 13 can be detected as an absolute value. In other words, the number of pitches n is determined by equation (7) or equation (10), and by substituting this number of pitches n into equation (5) or (6) or equation (8) or (9), the moving distance # is calculated. X is required. These calculations are performed in the calculation processing section 2.

In Fig. 1, the starting positions of the detection heads 14 and 15 are arranged so as to coincide with each magnetic pole tip for ease of understanding, but the above analysis results apply in the same way regardless of the position. It is possible. Also, the output signal ports S1 and DS2 were analyzed here with the maximum value set to "993".

The number of divisions of 1 cycle (1 pitch) is 1000, which can be selected arbitrarily, and it is also possible to further improve the accuracy by using three or more detection heads. Also, the primary @t&17 is magnetic pole NS from the beginning.
It is also possible to create a predetermined pattern and eliminate the need for winding.

FIG. 4 shows an example in which the present invention is applied to a linear step motor, in which a stator 35 made of a magnetic material with rack-shaped teeth and a movable part 3! are parallel to each other with a small gap in between. The movable part 31 is provided with two detection radars 32 and 33 along with an 0f mover 34 serving as a driving source, and a stator 35.
An output voltage corresponding to the moving pressure Fax is obtained from the south magnetic pole of the rack-like shape. The rack-shaped teeth of this fixed f-35 are made by sequentially changing the pitch interval in increments of 2 sentences, that is, the pitch interval is ◆2・Δl,・
..., l◆n·2 sentences, the movement distance X can be obtained as an absolute amount as described above.

FIG. 5 shows an example in which the present invention is applied to a cylindrical linear motor, in which the stator 45 has magnetic poles S and the pitch interval is sequentially changed by increasing the increment Δ, that is, the pitch interval is .12・ΔLove,...See◆n・2 sentences are arranged. The movable part 41, which is disposed parallel to the stator 45 and facing the stator 45 with a small gap in between, is provided with a movable element 44 serving as a driving source and two detection rads 42 and 43. Therefore, as described above, the moving distance X can be obtained as an absolute quantity.

In this cylindrical linear motor, the same effect can be obtained by cutting a groove as shown in FIG. 4 or a spiral groove as the fixed f. In addition, the movable parts and fixed parts in the above explanation are reversed and IJr! ! It is also possible to set the portion 21 on the fixed side and the fixed part on the movable side.

(Effects of the Invention) As described above, according to 9.1fi, the linear motor and the magnetic scroll can be integrated into a compact structure, and the moving distance of this linear motor is absolutely within the length measurement range. Since the quantity can be detected, it is possible to realize a small, inexpensive, and extremely high-performance absolute position detection device, and also to provide a conveyance line system using a linear motor with good performance.

[Brief explanation of drawings]

Figures 1 (A) to (C) are diagrams illustrating an embodiment of a device that implements the present invention and its operation, Figure 2 is a diagram showing the phase detection operation, and Figure 3 (A). , (B) A diagram explaining the concept of a beam near motor, FIGS. 4 and 5 are diagrams showing other embodiments of the present invention, FIG. 6 is a diagram explaining the principle of a conventional magnetic scale, and FIG. is a diagram showing its output characteristics. ■...Scale, 2...Scale base, 3,1
4, 15.32, 33, 42.43... 12 degrees to detection, 4.5... Tsubo saturation core, 8.7, 22.23...
・Excitation winding, 8, 9, 24.25... Output a line, +
1. IIA, +7-primary winding, 12.12A, +3
・Secondary conductor, 21... AC excitation power supply, 28A,
28B...phase detection circuit, 27A, 27B...^
/Roconverter, 25...@ Arithmetic processing unit, 31.41.
...Movable part, 34.44...Mover, 35.45
···stator.

Claims (1)

[Claims] In a linear motor consisting of a primary winding and a secondary conductor that face each other at a predetermined interval and are movable parallel to each other, the magnetic pitch of the primary winding is made different by a predetermined width, and the two
The feature is that absolute position can be detected by providing a secondary conductor part that is integrated by adding multiple detection heads to the secondary conductor, which is integrated by adding multiple detection heads to the secondary conductor. Absolute position detection device.