JPH03103716A - Position detector - Google Patents

Abstract

PURPOSE:To obtain high accuracy by detecting the instantaneous values of two-phase AC signal different in amplitude corresponding to the position of a moving body by an instantaneous signal detection part, calculating the sum of squares of the instantaneous signals, and detecting the position of the moving body from the relation between this value and the position of the moving body. CONSTITUTION:Magnetic sensors 4a and 4b output the two-phase AC signals Vsintheta and Vcostheta which are 90 deg. out of phase with each other. The gear shape of a gear disk 102 fitted to a rotary body 1 for varying the amplitudes of the two-phase AC signals according to the position of the moving body is so determined that all respective gears differ in tooth height; and differences from the surfaces of the magnetic sensors 4a and 4b to the end surfaces of the teeth of the gear disk 102 are made different with the position. The instantaneous signal detection part 11 consisting of hold circuits 6a and 6b and A/D converters 7a and 7b outputs the instantaneous signals Ss and Sc obtained by digitizing the two-phase AC signals and a low-order digit signal detection part 12 perform reverse trigonometric function conversion by dividing the signals Ss and Sc; and an arithmetic circuit 141 in a high-order digit signal detection part 14 calculates the sum of squares of the instantaneous signals and an adder 10 adds the high-order and low-order digit signals and outputs a position signal Snab.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a position detection device, and particularly to an absolute type position detection device.

(Prior Art) For example, an example of a magnetic rotational position detection device will be described with reference to FIG. Z of the gear disk 2 made of a gear-shaped magnetically permeable material and the disk made of a magnetically permeable material having only one notch 3A on the outer periphery.
A phase disk 3 is attached to the rotating body 1 of the object to be detected, and magnetic sensors 4a and 4b having magnets are arranged near the gear disk 2, and magnets are also arranged near the Z-phase disk 3. A magnetic sensor 5 with a magnetic sensor 5 is arranged. The magnetic sensors 4a and 4b are arranged so that the distance between the sensor elements is 174 of the gear l tooth of the gear disk 2, so the output thereof is as shown in FIG.
As shown in A), two-phase alternating current signals Vsinθ and Vcosθ having a phase difference of 90° are obtained. Further, as shown in FIG. 7(B), the output signal from the magnetic sensor 5 becomes a Z-phase signal P2 for identifying the position of a specific tooth of the gear disk 2 as the origin within one rotation, and It has a changing part P2° corresponding to 3A. Then, two-phase alternating current {g Vs
inθ and Vcosθ are the instantaneous signal S which is digitally converted in the instantaneous signal detection section l1 consisting of sample and hold circuits 6a and 6b and A/D converters 7a and 7b, respectively.
8 and Se, and after these instantaneous signals S8 and Se are divided in the lower digit signal detection unit l2, an inverse trigonometric function transformation ? As a result, the lower digit signal S0, which is the position θ within the gear lm, is obtained.

On the other hand, in the upper digit signal detection section 13, the two-phase AC signal Vsi
nθ and Vcosθ are converted into pulse signals P. by comparators 8a and 8b. and P, and the number of pulses of the pulse signals Pa and P from the Z-phase signal P representing the home position is counted by the pulse counter 9, and the upper digit signal Sn corresponding to the number of teeth of the gear from the home position is obtained. Output. The adder 10 is
The upper digit signal Sn and the lower digit signal S. and add the addition result to the position signal S,
The position of the moving body (rotating body 1) is detected.

(Problem to be Solved by the Invention) In the conventional device, as described above, the notch 38 of the Z-phase disk 3 is used as the origin, and the pulse signals P2 and Pb, which are the number of teeth of the gear, from this origin are counted. Since the absolute position within one rotation is determined by However, there was a problem in that the absolute position of the moving body was not determined.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a position detection device that can always detect an absolute position within one rotation.

(Means for Solving the Problems) The present invention has been made to solve the above-mentioned problems. The amplitude of the two-phase AC signals having a predetermined phase difference from each other is made to vary depending on the position of the moving body,
A position detection device is provided that can detect the absolute position of a moving object based on the relationship between the sum of squares of the instantaneous values of the two-phase AC signal, which is the square value of the amplitude, and the position of the moving object.

That is, the present invention relates to a position detection device that detects the position of a moving body based on two-phase AC signals having a periodic waveform corresponding to the distance traveled by the moving body and having a predetermined phase difference from each other. The above objects of the present invention include: a sensor section that outputs two-phase AC signals with different amplitudes depending on the position of the moving object; an instantaneous signal detection section that detects the instantaneous value of the two-phase AC signal; This is achieved by providing a calculating means for calculating the sum of squares of the signals, and a detecting means for detecting the position of the moving object based on the relationship between the sum of squares and the position of the moving object.

(Function) In the present invention, two-phase AC signals Vtprsinθ and V(pl
Output cosθ. Then, the sum of squares of the instantaneous values of this two-phase AC signal fV cp)sjnθ) ” (V .p)COSθ
) 2-V tp+ ・=' (2) is the position P
Therefore, the position @P of the moving object is detected in absolute terms using the relationship between the sum of squares v tp+ and the position P.

(Example) Embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows a position detection device of the present invention in correspondence with FIG. The gear disk 102 of the present invention attached to the rotating body 1 has a special gear shape, and the magnetic sensors 4a and 4b output two-phase AC signals Vsjno and Vcosθ having a phase difference of 90° as in the conventional case. do. However, in the present invention, in order to change the amplitudes of the two-phase AC signals Vsinθ and Vcosθ depending on the position of the moving body, the gear shape of the gear disc 102 is changed so that the tooth heights of the teeth of each gear are all different as shown in FIG. The distance from the surfaces of the magnetic sensors 4a and 4b to the end surface of the teeth of the gear disc 102, the so-called gap length, is made different depending on the position. Therefore, the output signals from the magnetic sensors 4a and 4b gradually decrease with respect to the position P as shown in FIG. P, Sinθ and V tp+
It becomes COSθ. In this embodiment, the tooth height of each gear tooth is within a range in which the amplitude VIP+ can be considered to change approximately linearly with respect to the gap length,
, ) to the n (≧2)th tooth height Ill as Ho−
11+ − n−J ・・”” (
3) (A is a constant).

Further, the instantaneous signal detection section 1l is composed of sample and hold circuits 6a, 6b and ^/D converters 7a, 7b as in the conventional case, and detects the two-phase AC signals V fpl SjQθ and v tp.
Digital instantaneous signals S and Sc obtained by digitally converting + cos θ are output. Similarly to the prior art, the lower digit signal detection section 12 also divides the instantaneous signals S and Sc, performs inverse trigonometric transformation, and outputs the lower digit signal S0, which is the position θ within the gear 1 tooth. On the other hand, the arithmetic circuit 1 in the upper digit signal detection section 14
41 is S%+S%- from the instantaneous signals Ss and Sc.
(V lplSjnθ)""(VIPICOS
θ)2=V IPI ・・・・・・
By performing the calculation in (5), the positions P and V IP as shown in FIG. 3 are stored in advance as the data table 142.
Based on the relationship of I', the V IPI 2 outputs the upper digit signal Snab, which is the absolute position within one revolution at that time. The adder IO receives the upper digit signal Snah and the lower digit signal S. Add and add the position number Spa
By outputting b, the absolute position of the moving body (rotating body 1) can always be detected.

FIG. 4 is a partial C view of another embodiment of the present invention.

As shown in FIG. 4, the gear disk 2 attached to the moving body 1 is the same as the conventional gear disk explained in FIG. 6, but in this embodiment, the center of the gear disk 2 and the moving body 1 are It is mounted eccentrically, with its center of rotation shifted. As a result, the gap length from the surfaces of the magnetic sensors 4a and 4b to the teeth of the gear disk 2 differs at each position within 180° with the eccentric direction as the symmetrical axis, so the two-phase AC output from the magnetic sensors 4a and 4b Signal V tpl sin θ and V
(P) The relationship between the square value V + Pl' of the amplitude of COS θ and the position P is also as shown in FIG. Therefore, by determining this relationship as a data table, it is possible to detect the absolute position within 180 degrees by performing the same processing as in the above example.

In addition, considering that the relationship shown in Fig. 5 is almost a sine wave except for the offset, the same magnetic sensors 4a and 4b are placed at a position 90° shifted from the center of the rotating body with respect to the magnetic sensor. or by shifting the eccentric directions of two identical gear disks by 90 degrees, a two-phase signal v < p+ 2 with a 90' phase difference can be detected, and the lower order of the first embodiment can be detected. The absolute position within one rotation may be detected in the same manner as the processing performed by the digit signal detection section 12.

In addition to the above-mentioned gear type, the present invention also uses, for example, a drum magnetization type, in which the magnetic material on the drum surface on the rotating body side is magnetized.
It can also be applied to detecting the magnetic flux using a magnetic sensor.

In this case, in addition to changing the gap length mentioned above, the amplitude of the two-phase AC signal can be changed by changing the magnetization strength of the magnetic material on the drum surface depending on the position.
The absolute position of the rotating body can be detected by a method similar to that of the previous embodiment. In addition, even in the case of a method other than the rotation type, such as a linear movement type, two-phase AC can be used by changing the gap length with respect to the position by arranging the detected object at a slight angle with respect to the sensor surface. You can change the width of the signal, or in the case of a magnetized type, as described above,
By changing the amplitude of the two-phase AC signal by changing the magnetization strength with respect to the position, the absolute position of the moving object can be detected. Furthermore, the present invention is not limited to magnetic type position detection devices, but can also be applied to optical type or other types that perform position detection using two-phase AC signals.

(Effect of the invention) As described above, according to the invention, absolute position detection can be always performed based on the relationship between the position P and the sum of squares of the two-phase AC signal, so the reliability of position detection is improved. improves.

Halt circuit, 7a, 7b-・A/o converter, 8a, 8
b --- Comparator, 9... Pulse counter, 10...
Adder, 11... Instantaneous signal detection section, 12... Lower digit signal detection section, 13j4... Upper digit signal detection section.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a rotational position detection device that is an embodiment of the present invention, Fig. 2 is a waveform diagram showing an example of the sensor output signal, and Fig. 3 is the square value of the amplitude of the sensor output signal VfPl' 4 is a partial diagram showing another embodiment of the wooden invention, FIG. 5 is a waveform diagram of the sensor output, and FIG. 6 is an example of a conventional position detection device. The configuration diagram shown in FIG. 7 is a waveform diagram of the sensor signal.

Claims (1)

[Claims] 1. In a position detection device that detects the position of the moving object based on two-phase AC signals having a periodic waveform corresponding to the moving distance of the moving object and having a predetermined phase difference from each other, a sensor unit that outputs two-phase AC signals with different amplitudes depending on the position; an instantaneous signal detection unit that detects the instantaneous value of the two-phase AC signal; a calculation unit that calculates the sum of squares of the instantaneous signals; A position detection device comprising: a detection means for detecting the position of the moving body based on the relationship between the sum of squares and the position of the moving body.