JPH04212017A - Absolute rotation position detector - Google Patents

Abstract

PURPOSE:To enlarge an absolute rotation position detecting range with a compact structure. CONSTITUTION:Two or three variable magnetic resistance type rotation detecting units which generate cyclic rotation position detecting signals including different cycles according to a rotation displacement of an object to be detected are provided. Difference between the position detection signals of the first and the second detecting units is obtained, and a first periodicity signal for indicating periodicity of the first position detection signal is calculated based on the difference. Further, difference in the position detection signals of the first and third detecting units is obtained, and a second periodicity signal for indicating the periodicity of the first periodicity signal is calculated based out the difference. By combining the three, that is the first position detection signal, the first and second periodicity signals, an absolute position can be accurately specified over a wide range. An apparatus comprises stator and rotor parts of the respective detecting units and a rotation transmitting mechanism integrally housed with appearance of a single rotation detector equipped with one rotation input axis provided on the apparatus, to realize an entirely compact structure.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an absolute rotational position detection device capable of detecting absolute rotational positions over a wide range.

0002

[Prior Art] Conventional absolute encoders can only detect the absolute position within one rotation, and in order to detect the absolute position over multiple rotations, a separate rotation speed detection means is provided, and the rotation speed detected by this and the absolute position within one rotation. Conventional rotational speed detection means require a gear with a fairly large reduction ratio in order to detect the rotational speed in an absolute manner. For example, the main axis 3
When configuring a gear down mechanism so that up to 2 rotations can be detected absolutely, a 32-tooth gear is installed on the main shaft,
It is conceivable to provide a gear with 1024 teeth on the deceleration output shaft, but in that case, the response accuracy at the rotation speed switching point would be 1.
We can only expect an accuracy of approximately 11 degrees when the rotation is divided into 32, or in terms of angle. As described above, although a fairly high-precision gear mechanism is required, there is a drawback that detection accuracy cannot be expected to be very high. In order to avoid such difficulties, the number of revolutions is sometimes obtained by counting incremental pulses, but in this case there are problems such as the number of revolutions becoming unclear due to power outages or the like.

Furthermore, Japanese Patent Publication No. 50-23618 discloses a linear position detection device using a magnetic scale consisting of a magnetic track having a large number of magnetic gratings (permanent magnet gratings) that are magnetized in opposite directions alternately. It is shown that by providing two magnetic tracks with different magnetic grating wavelengths and comparing the phases of the phase modulated output signals of each magnetic track, an output signal with an expanded absolute position detection range can be obtained. ing.

Furthermore, in Japanese Patent Application Laid-Open No. 52-76952, two rotational position transducers are arranged at a ratio of 255:2.
It is disclosed that the rotation speed information of one transducer is obtained by coupling the two transducers with a gear ratio of 56 and obtaining the output difference between the two transducers. Here, the determined output difference is used as it is as shaft rotation speed data. In other words, the gear ratio of 255:256 means that the first shaft
When the shaft rotates, the output difference is exactly 1, which makes it possible to detect up to 256 rotations of the first shaft. In the case of such a configuration, there is a problem in that in order to expand the absolute detectable range, the gear must be made larger accordingly. For example, in order to be able to detect up to 1024 rotations, the gear ratio must be set to 1023:1024, which increases the size of the gears and requires strict processing accuracy.

Moreover, in this prior art, a problem arises in that as the number of gear teeth increases, the detection accuracy decreases in inverse proportion to the expansion of the absolute detection range. In other words, as the number of gear teeth increases, the difference in the output values between the two detectors per rotation becomes smaller, and the ratio of errors in the detector output data causing errors in rotation speed detection increases, resulting in a decrease in detection accuracy. That's what I do. for example,
When an encoder with a resolution of 1024 per revolution is used as a detector, and the gear ratio is 1023:1024, the output difference between the two encoders of "1" corresponds to one revolution, so the encoder output error is ±1. Even if there is, it will result in a detection error of one rotation.

[0006]

[Problem to be solved by the invention] The above-mentioned Special Publication Publication No. 50-2
What is shown in Japanese Patent No. 3618 is a linear position detector, and there is no indication at all how to apply this to a rotational position detecting device. Furthermore, even if one were to consider applying this as is to a rotational position detection device, it would be necessary to provide a magnetic track with a permanent magnet lattice that is alternately magnetized in opposite directions, which would require manufacturing and processing. However, there are problems in that it is troublesome and increases the cost. Furthermore, the usage environment is naturally limited. Furthermore, when two or more, for example three, magnetic tracks are provided, it is unclear what kind of configuration will be used to obtain an output signal with an expanded detection range, so it is difficult to efficiently expand the detection range. It was not easy to come up with a possible rotational position detection device.

Although the device disclosed in the above-mentioned Japanese Patent Application Laid-open No. 52-76952 is of the rotational position detection type, it is important to consider how to compactly combine a plurality of rotational position detectors to provide one absolute rotational position detector. The FIG. 1, it becomes bulky and large-scale when assembled as a device. Furthermore, although it has been shown that two rotary position transducers can be combined, there is no perspective as to what measures should be taken when installing three or more to further expand the detectable range. In other words, there was a limit to the detectable range.

The present invention has been made in view of the above-mentioned points, and uses a plurality of rotation detecting sections each of which generates periodic rotational position detection signals each having a different period depending on the rotational displacement of the object to be detected. In an absolute rotational position detection device that can obtain a rotational position detection signal with an expanded absolute position detection range by calculating the output signal, the configuration of the rotation detection section is simplified and costs are reduced. , it is assembled into a compact device as a whole, realizing miniaturization and ease of use, and does not require an excessive reduction ratio, and has a mechanically simple configuration compared to conventional ones, making it extremely An object of the present invention is to provide an absolute rotational position detection device that can accurately detect absolute rotational positions over a wide range. Another object of the present invention is to provide an absolute rotational position detection device that can effectively perform detection in an expanded range by combining three rotational position detection sections.

[0009]

[Means for Solving the Problems] An absolute rotational position detection device according to a first aspect of the present invention includes a rotation transmission means for imparting rotational motion applied to a rotation input shaft to a detection section, and a rotation transmission means that transmits rotational motion applied to a rotation input shaft. A motion corresponding to the rotational displacement of the input shaft is given to each, and a periodic rotational position detection signal is generated according to the rotational displacement of the input shaft, and the rotational displacement of the input shaft corresponding to one cycle of each is given. first and second rotation detectors having different amounts; and
The difference between the first rotational position detection signal generated by the rotation detection unit and the second rotational position detection signal generated by the second rotation detection unit is determined, and based on this difference, the first rotation detection unit arithmetic means for performing a calculation to determine the number of periods from the origin with respect to the origin and outputting a period number signal indicating the determined number of periods, and each of the rotation detecting sections includes a plurality of primary coils and a plurality of secondary coils. A stator, a rotor that rotationally displaces according to a given rotational displacement and gives a magnetic resistance change according to the rotational position to the magnetic circuit of the stator, and each of the primary coils are excited with phase-shifted alternating current signals. , has a circuit that causes a secondary coil to generate an output signal having a phase shift according to the rotational position of the rotor, and a circuit that measures the phase shift of this output signal and outputs it as the rotational position detection signal, The present invention is characterized in that the stator and rotor portions of the first and second rotation detecting sections and the rotation transmitting means are integrally housed.

According to the second aspect of the present application, a third rotation detecting section is provided, and the mutual difference in the amount of rotational displacement of the input shaft corresponding to one cycle of each rotation detecting section is determined by the third rotation detecting section. The difference between the first rotation detection section and the second rotation detection section (first difference) is greater than the difference between the first rotation detection section and the third rotation detection section (second difference). It's supposed to be big. Then, a first difference, which is the difference between the first rotational position detection signal generated by the first rotation detection unit and the second rotational position detection signal generated by the second rotation detection unit, is determined. a first calculation means that performs a calculation to determine the number of periods from the origin regarding the first rotation detection section based on the difference between the two, and outputs a first period number signal indicating the determined number of periods; Determining the difference between the first rotational position detection signal generated in the section and the third rotational position detection signal generated in the third rotation detection section as a second difference,
a second calculation means that performs a calculation to determine the number of periods of the first period number signal based on the second difference and outputs a second number of periods signal indicating the determined number of periods; 1st
, the stator and rotor portions of the second and third rotation detecting portions and the rotation transmitting means are integrally housed.

[0011]

[Operation] Since there is a difference in the amount of rotational displacement of the rotational input shaft corresponding to one period of each rotation detection section, for example, the first rotational position detection signal generated from the first rotation detection section corresponds to exactly one period. When the rotational position detection signal of the second rotation detection section changes, the rotational position detection signal of the second rotation detection section does not show a change of exactly one period, and a difference occurs between the respective position detection signals. This difference gradually widens as the rotational displacement from the origin increases, and depending on how large this difference is, it becomes clear how many cycles from the origin the first rotation detection section is. Therefore, the calculation means calculates the difference between the first rotational position detection signal and the second rotational position detection signal, and performs calculation to determine the number of cycles from the origin for the first rotation detection section based on this difference. The absolute rotational position from the origin can be specified by the combination of the periodic number signal indicating the determined periodicity and the first rotational position detection signal.

The structure of the rotation detection section is such that the rotor gives a change in magnetic resistance to the magnetic circuit of the stator according to the rotational position, and there is no need for significant magnetization (permanent magnetization). Therefore, manufacturing and processing are simple and cost is low. Furthermore, it is not subject to any restrictions on the usage environment. Furthermore, since the stator and rotor portions of the first and second rotation detection sections and the rotation transmission means are integrally housed, one rotation detector equipped with one rotation input shaft can be used. The appearance of the device can be improved, the device can be assembled into a compact device as a whole, and the device can be made smaller and easier to use.

According to the second invention, the difference (first difference) between the position detection signals between the first rotation detection section and the second rotation detection section is greater than the difference between the position detection signals between the first rotation detection section and the second rotation detection section. This is larger than the difference (second difference) in the position detection signal between the position detection signal and the rotation detection unit No. 3. Also,
These differences gradually widen as the displacement from the origin increases, and depending on how large these differences are, it becomes clear how many cycles from the origin the first rotation point detection section is. Furthermore, these differences all exhibit periodicity. In other words, the difference gradually widens as the displacement from the origin increases, but since the position detection signal itself has periodicity, these differences also have periodicity. Since the rate of change of the first difference is larger than that of the second difference, the accuracy of the data is good, and the first rotation detection section detects how many cycles from the origin it is. suitable for However, since the first difference period arrives earlier than the second difference period,
To extend the detectable range, a second
It is desirable to utilize the difference between

[0014] Therefore, a second difference is determined by the second calculation means. Here, if the number of cycles from the origin regarding the first rotation detection section is directly determined based on the second difference, the rate of change is small, so compared to the case where it is determined based on the first difference. The accuracy will be much worse. Therefore, in order to improve the accuracy and expand the detectable range, this second calculation means
Based on the difference, an operation is performed to determine the number of cycles of the first number of cycles signal. Naturally, there is a correlation between the periods of the output signals of each rotation detection section, and there is also a correlation between the first difference and the second difference, so the first period number signal is determined based on the second difference. In other words, the number of periods of the first difference can be determined. A signal indicating the period number of the first period number signal thus determined is output as a second period number signal. In other words, since the period itself of the first period number signal is much longer than the period of the first position detection signal, the period number of the first period number signal is determined based on the second difference having a small rate of change. The determination can be made with much higher precision than when the number of cycles from the origin of the detection target for the first detection unit is directly determined based on this second difference.

The first period number signal thus obtained indicates the period number of the first rotational position detection signal, and the second period number signal indicates the period number of the first period number signal. Therefore, these first rotational position detection signals, the first
The combination of the period number signal and the second period number signal is
This method precisely specifies the absolute position of the detection target from the origin over a wide range.

As described above, in the second invention, what is determined by the second calculation means is not the number of periods from the origin regarding the first rotation detection section, but the number of periods of the first period number signal. Therefore, when using a gear train as a transmission means, for example, without increasing the number of gear teeth,
The absolute rotational position detection range can be expanded, the mechanical structure can be simplified and smaller, and the accuracy can be improved.

In other words, in the relationship between the first and second rotation detection sections, the absolute position detection range may be relatively narrow, and accordingly, for the reasons mentioned above, it is possible to simplify the mechanical structure and improve accuracy. Further expansion of the absolute position detection range is achieved by providing the third rotation detection section and the second calculation means. Here, since the second period number signal indicates the period number of the first period number signal, its accuracy is sufficient if it is coarse, and this means that some error of the detector is This means that the calculation accuracy of the period number of the first period number signal is not affected at all, and therefore the detection accuracy is improved.

Therefore, according to the second invention, even when a reduction mechanism such as a gear train is used as a transmission means, an excessive reduction ratio is not required as in the conventional case, and the reduction ratio is reduced compared to the conventional case. With a mechanically simple configuration, absolute positions over an extremely wide range can be detected with high precision.

To show the correspondence between the first invention and the embodiments described below, the first and second rotation detecting sections correspond to the first and second rotary encoders RE1 and RE.
2. Gears 1 and 2 correspond to the rotation transmission means, and subtractor 5 and divider 7 correspond to the calculation means. Also, to show the correspondence between the second invention and the embodiments described below, those corresponding to the first to third rotation detection sections are the first to third rotary encoders RE1 to RE3, and the rotation transmission means. Gears 1 to 4 correspond to gears 1 to 4, subtracter 5 and divider 7 correspond to the first calculation means, subtracter 6 and divider 8 correspond to the second calculation means, It is.

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. First, the principle of this invention will be explained with reference to FIG. The absolute rotational position detection device shown in FIG. 1 is composed of three absolute rotary encoders RE1, RE2, and RE3. Each encoder RE1 to RE3 divides one rotation into N parts (N is any integer), and each outputs a rotational position detection signal that indicates the rotational position of each rotor (not shown) using an absolute address within one rotation. do. The first rotary encoder RE1 is connected to the main shaft and detects rotation of the main shaft. The rotation to be detected is applied to this main axis. The number of teeth is n-1 on the rotating shaft of the first rotary encoder RE1.
(where n is an arbitrary integer) gear 1 is provided,
This gear 1 meshes with a gear 2 having n teeth and provided on the rotating shaft of a second rotary encoder RE2. Furthermore, the second
The encoder RE2 is provided with a gear 3 having n+1 teeth, and this gear 3 meshes with a gear 4 having n teeth provided on the rotating shaft of the third encoder RE3.

Therefore, when the main shaft rotates once, RE1 becomes 1.
rotation, RE2 is (n-1)/n rotation, RE3 is {(n-
1)(n+1)}/n2 rotations. Here, the rotational position (
If the absolute addresses within one rotation are respectively D1, D2, and D3, then the value of D1 when the spindle makes one rotation is N (however, the value N indicating the maximum rotational position is equivalent to 0), D2
, D3 are as follows. D1=N D2={N(n-1)}/n D3={N(n-1)(n+1)}/n2
...(1)

In other words, each encoder RE1 to RE3
The outputs D1 to D3 vary at a predetermined period according to the mechanical displacement of the spindle (rotational displacement over multiple rotations from the origin), and the amount of mechanical displacement of the spindle corresponding to each period (less than one rotation or less) (rotation angle above) is for each encoder R
Each of E1 to RE3 is different. In other words, the mechanical displacement P1 of the main shaft corresponding to one period of the first encoder RE1, that is, the rotation angle is 2π radians (that is, one rotation)
However, the mechanical displacement amount P2 of the main shaft corresponding to one cycle of the second encoder RE2, that is, the rotation angle is {n/(n
-1)}・2π radians (that is, (n-1)/n rotations)
, the mechanical displacement P3 of the main shaft corresponding to one cycle of the third encoder RE3, that is, the rotation angle is n2/{(n-1)
(n+1)}・2π radians (that is, {(n-1)(n
+1)}/n2 rotations).

The mechanical position of the spindle, that is, the absolute rotation angle over multiple rotations from the origin, is plotted on the horizontal axis, and each output signal D1
, D2, D3 on the vertical axis, each encoder RE1
FIGS. 7A, 7B, and 7C show periodic changes in the output signals D1 to D3 of RE3. When the main shaft stands still at a certain mechanical absolute position (that is, absolute rotation angle), the output signals D1 to D3 corresponding to that position are sent to each encoder RE.
1 to RE3. As is clear from FIG. 7, each of the output signals D1 to D3 always shows a value less than one cycle. but,
Since the mechanical displacement amount (rotation angle) of the main shaft corresponding to one cycle of each output signal D1 to D3 is different, each output signal corresponds to the individual absolute position of the main shaft shown on the horizontal axis in FIG. The values of D1 to D3 each represent a unique combination. Specifically, the number of cycles of the output signal D1 of the first encoder RE1, which corresponds 1:1 to the rotation of the main shaft (that is, the absolute number of rotations of the main shaft counted from the origin), is the same as that of each output signal D1 to D3. is uniquely determined by a unique combination of values. In making this determination, of course, not only the current values of the signals D1 to D3 but also the main axes corresponding to one cycle of each signal D1 to D3 that are the cause of the difference in each of these signals D1 to D3 must be determined. Information related to the amount of mechanical displacement (or their difference) is also involved. The absolute position of the main shaft can be specified by the combination of the thus determined number of cycles of the output signal D1 of the first encoder RE1 and the current value of the signal D1.

The number of cycles of the output signal D1 of the first encoder RE1 is based on the current value of each signal D1 to D3 and the number of cycles of each signal D1 to D3.
Information related to the amount of mechanical displacement of the spindle corresponding to one cycle of D3 (i.e., each encoder R of the mechanical movement of the spindle)
information related to the degree of transmission to E1 to RE3),
It can be determined by algebraic or mathematical methods. There are various calculation methods that can be used for this purpose, but among them,
The most efficient method in terms of calculation time and calculation circuit configuration is shown below. It includes a constant related to the difference between one cycle of the first encoder RE1 and one cycle of the other encoders RE2 and RE3, and a constant between the current value of the output signal D1 of the first encoder RE1 and the other output signals D2 and D3. This method uses the difference from the current value. As an example, the above-mentioned constants are considered based on one cycle of the first encoder RE1, and the constants of the encoder R
Another encoder R corresponding to the amount of displacement of the main shaft (that is, one rotation) that causes a one-cycle change in the output signal D1 of E1
It is established by considering the changes in the output signals D2 and D3 of E2 and RE3. That is, the first encoder RE
Output signals D2 of the other encoders RE2 and RE3 corresponding to one period of displacement (one rotation of the main shaft) of the output signal D1 of the encoder 1
, D3 are known in advance, and other encoder outputs D2, D3 with respect to the first encoder output D1 at that time
The differences "D1-D2" and "D1-D3" can be established as the above constants.

[0025] Thus, the difference "D12=D1-D2" between the outputs D1 and D2 of the encoder RE1 and the second rotary encoder RE2 per cycle of the first rotary encoder RE1 when the main shaft rotates once is expressed as above. From equation (1), it can be expressed as follows. Change in D12 per spindle rotation (one period of RE1) = N/n...(
2)

Therefore, both encoders RE1 and RE2
The difference D12 between the current outputs D1 and D2 of
By dividing by the above-mentioned constant N/n representing 2 as shown below, it is possible to obtain the rotational speed (this will be referred to as the absolute rotational speed) Rx of the main shaft counted from the origin. This Rx
corresponds to the number of cycles of the output D1 of the first encoder RE1. Note that the origin is all encoders RE1, RE2, and R.
This is the point where the outputs D1, D2, and D3 of E3 are all zero.

Rx=D12÷(N/n)
...(3) In the above formula (3), D12=D1-D2
...(4), but both D1 and D2 are values that change modulo N with rotation, and the rate of change is slower for D2 than D1 at the ratio of (n-1)/n. , the simple difference "D1-D2" can be a negative number. When this simple difference "D1-D2" becomes a negative number, the sum of N added to that simple difference is set as D12, and D
12 always represents the effective difference between D1 and D2. In actual calculations, there is no need for a special N addition, and "-D2
'' as a complement, execute ``D1-D2'' by complement operation with N as the carry value, and ignore the sign bit to find the effective difference D12, which is equivalent to performing N addition. I can do it. The state of the effective difference D12 with respect to the absolute position of the main axis is shown in FIG. 7(d).

[0028] Absolute rotational speed R obtained from the above equation (3)
By combining the integer part of x and the rotational position detection output D1 of the first rotary encoder RE1 (that is, truncating the decimal part of Rx obtained by equation (3) and using D1 as the decimal part), a multi-rotation type The absolute rotational position detection value is obtained.

By the way, when the absolute rotational speed Rx of the main shaft reaches n, the difference D12 becomes N (that is, 0), and it becomes impossible to detect any further absolute rotational speed. Therefore, only by using the first and second rotary encoders RE1 and RE2, only the absolute rotational position up to n rotations can be detected. The third rotary encoder RE3 is provided to expand the absolute rotational position detection range. In other words, the first and second encoders RE1, RE2
The rotational speed (that is, R
Rx (number of cycles of E1) is a periodic signal with one period equal to a predetermined value n, and a third encoder RE3 is used to further obtain the number of periods of this periodic signal and thereby further expand the absolute position detection range. is provided.

Difference between the outputs D1 and D3 of the first and third encoders RE1 and RE3 per rotation of the main shaft ``D13=D
1-D3'' can be expressed as follows from equation (1) above. Change in D13 per rotation of the spindle = N/n2... (5) From equations (2) and (5) above, the relationship between the change in D12 and the change in D13 per rotation of the spindle is as follows: Express.

D13=D12/n
...(6) In other words, the difference D13 is 1 of the difference D12
/n as the spindle rotates. Also,
From the above equation (5), the first and third encoders RE1, R
It can be seen that the absolute rotational speed R'x can be determined by dividing the difference D13 between the current outputs D1 and D3 of E3 by the above-mentioned constant N/n2 indicating the difference D13 per revolution as shown below. R'x=D13÷(N/n2)
…(7)

However, in the calculation of the above equation (7), the divisor is 1/n compared to the above equation (3), so
The resolution becomes coarser, and the error in D13 has a relatively large effect on R'x. Therefore, from the above equation (6), the value of D13 when D12 reaches the maximum value N (i.e. 0) is N/n.
and divide the difference D13 by this, D13÷(N/n)=Ry
...(8), and the calculation accuracy of Ry is Rx in equation (3)
The calculation accuracy is the same as that of . Here, the following relationship is derived from equations (7) and (8).

R'x=Ry・n
...(9) That is, the value Ry obtained by equation (8) is the value of 1/n of the absolute rotation speed R'x, and is a value that increases by 1 every time the main shaft rotates n times from the origin. . On the other hand, the value Rx obtained based on the difference D12 by the above equation (3) indicates only the absolute rotation speed up to n rotations as described above, and for the absolute rotation speed of n rotations or more, it ranges from 0 to n(
However, since n is equal to 0, strictly speaking it is "n-1"
) is repeated. Therefore, the integer part of Ry obtained by equation (8) is the upper absolute rotation number with n rotations as one unit of the absolute rotation number, and the integer part of Rx obtained by equation (3) is defined as the absolute rotation number 1 rotation. If the lower absolute rotational speed is set as one unit and the two are combined, the absolute rotational speed can be detected over a wide range. The absolute rotation speed R'x obtained from this combination can be expressed as follows.

R'x=Ry・n+Rx
...(10) Furthermore, in the above formula (8), D13=D1-D3
...(11), but D of the above equation (4)
Similar to 12, the simple difference "D1-D3" can be a negative number. In that case, similar to D12 above, the simple difference "
When "D1-D3" is a negative number, the value obtained by adding N is used as the effective difference D13, and as described above, a special N addition operation is not required in actual calculations. By the way, from the above equation (5), when the absolute rotational speed R'x of the main shaft reaches n2, the difference D13 becomes N (that is, 0), and it becomes impossible to detect any further absolute rotational speed. Therefore, when adding the third rotary encoder RE3,
The absolute rotation speed detection range is expanded to n2 rotations. Figure 7 (
In e), the state of the effective difference D13 with respect to the absolute position of the main axis is shown. As is clear from the figure, one cycle of D12 corresponds to n (for example, 32) cycles of D1, and D13
One period corresponds to n2 (for example, 1024) periods of D1.

As mentioned above, the above ((
If we execute the calculations of equations 3) and (8), we can get n2 from the origin.
Multi-rotation type absolute rotational position up to rotation can be determined. In that case, the format of the multi-rotation type absolute rotational position signal consists of D1, Rx, and Ry, and the output D1 of the first encoder RE1 is set as the lowest weight, and the Rx obtained by the above equation (3) is set as the uppermost of D1. , and Ry obtained by the above equation (8) is set as the upper weight of Rx. Therefore,
The absolute rotational position detection signal based on the combination of these three types of data D1, Rx, and Ry has an accuracy of one rotation divided into N.
It is possible to express absolute rotational position up to two rotations. FIG. 2 shows a basic circuit configuration block diagram for executing the calculations of equations (3) and (8), in which 5 and 6 are subtracters, and 7 and 8 are dividers.

[0036]Although the constants N and n can be determined as appropriate, it is common for N to be a relatively large value in order to improve accuracy, and n also to be a relatively large value in order to widen the detection range. This is desirable. However, if n is too close to N, the divisor N/n in equations (3) and (8) will become small, and the precision of Rx and Ry will deteriorate. Further, for convenience of calculation, it is preferable that n be a divisor of N. Considering the above points, as a preferable example, each constant N and n may be determined so that N=n2. For example, when N=1024, n
= 32, with an accuracy of 1024 divisions per rotation, 1
It becomes possible to detect the absolute rotational position within the range of 0.024 rotations.

In the above description, the speed is decelerated at a ratio of "n-1 to n" between the first and second rotary encoders RE1 and RE2, and the speed is increased at a ratio of "n+1 to n" between RE2 and RE3. However, on the contrary, between RE1 and RE2
The speed may be increased at a ratio of "-1", and decelerated at a ratio of "n to n+1" between RE2 and RE3. Although the calculation formulas in that case are not exactly the same as the formulas (1) to (11) above, they can be easily derived by analogy with these formulas, but they are not particularly shown here. Also, each encoder RE
Instead of setting the increase/decrease ratio between RE1, RE2, and RE3 as "n-1 vs. n" or "n+1 vs. n," it may be set as "na vs. n" or "n+a vs. n." However, if a is sufficiently smaller than n and is a divisor of n, it is preferable for convenience of calculation. In that case, the divisor of equations (3) and (8) is aN/n.

By the way, if the absolute rotational speeds Rx and Ry are simply calculated using the above equations (3) and (8), the following error may occur when they are combined with the encoder output D1. For example, when N=1024 and n=32, the states of the encoder outputs D1 and D2 at the portion where the rotation of the main shaft switches from the first rotation to the second rotation are shown in Figs. 3(a), (b), and (c).
) are shown respectively. In the same figure (a), each encoder output D1, D
2, shows the case where there is no error in D3, the same figure (b)
2 shows a case where an error occurs in the encoder output D2 in the forward direction, and (c) in the figure shows a case where an error occurs in the encoder output D2 in the backward direction. As shown in (a),
Even under normal conditions, in a certain range just before the rotation speed changes,
There is a part where "D1-D2" becomes "32, that is, n", and in this part, the rotation speed Rx determined by the above equation (3) becomes "1". This is theoretically “D1-
D2" is a number that changes continuously as D1 and D2 change, but the change step of "D1-D2" is n of D1.
There is one step per step, and the change steps of D1 and D2 are not the same but gradually deviate, so between the theoretical one change step of "D1-D2" (that is, n steps of D1) , the actual "D1-D2" does not maintain a constant value, but there is a difference of 1 between the theoretical value and that value.
The plus value is repeated alternately, and the ratio of the plus value gradually becomes higher, and eventually when the theoretical change step switches, the actual "D1-D2" also changes to the theoretical value (
This is due to the fact that the value is changed to a value obtained by adding 1 to the theoretical value of the previous step. Therefore, the range in which the theoretical value of D12 switches from 31 to 32, that is, "992≦D1≦1023
(Generally, N-n≦D1≦N-1), D12=n=32 as shown in FIG. 3(a). Therefore, for example, the position D1 = 1023, D2 = 991 is actually the 1023rd address of the first rotation (Rx = 0), but if you simply apply the above formula (3), D12 = 32
Therefore, Rx=1, resulting in the 1023rd address of the second rotation. In addition, if an error as shown in Figure (b) occurs, even if the above equation (3) is simply applied at the position of D1 = 0, D2 = 992, Rx = 1, and the result is as follows in the second rotation. The correct absolute rotational position of address 0 can be found, but D
At the position where 1=0 and D2=993, simply applying equation (3) results in Rx=0, and an incorrect position of the 0th address of the first rotation, that is, the origin, is obtained. Also, the same figure (c
), D1=102
3. Even though it is the 1023rd position of the first rotation at the position D2=990, if you simply apply equation (3), R
x=1, resulting in the second rotation at address 1023.

In order to improve the above-mentioned malfunction, D12 is not used as is in the equation (3), but is modified as follows according to the rotational position of the main shaft, that is, the range of the output D1 of the encoder RE1. shall be taken as a thing. 0≦D1≦511 (generally 0≦D1≦(N/2
)-1) Rx=(D12+k)÷(N/n)
...(3-1)
512≦D1≦1023 (generally N/2≦D1≦
N-1) Rx=(D12-k)÷(N/n)
...(3-2) However, k is an integer arbitrarily set according to the allowable error range. For example, if you want to allow an error of up to 8 divisions, k
=8.

The above formula (3) can be replaced with the above formula (3-1) or (
By changing equation 3-2), the above-mentioned malfunction can be improved as follows. First, in the case of FIG. 3(a), the rotation angle range immediately before the rotation speed is changed is "512≦D1≦
1023'', and by applying the above equation (3-2), the value obtained by subtracting the constant k (for example, 8) from ``D1-D2=D12'' is divided by the constant N/n. Then, for example, at the position D1=1023, D2=991, "D12
-k=1023-991-8=24'', so Rx
= 0, and the correct position of address 1023 of the first rotation is found. In addition, in the case of FIG. 3(a), “0≦D1≦
511'', the above formula (3-1) is applied, and for example, in the position D1=0, D2=992, the range ``D12+k=10
24-992+8=40", so Rx=1,
The correct rotational position can be determined without any problems. In the case of FIG. 3(b),
The above formula (3-1) is applied in the range immediately after the rotation speed change which is affected by the error, for example, D1=0, D2=99.
At position 3, “D12+k=1024-993+8=3
9'', so Rx=1 and the correct position can be found. Further, even if the above equation (3-1) or (3-2) is applied in a region that is not affected by errors, the correct position can be found without any problem. In the case of FIG. 3(c), the above formula (3-2) is applied in the range immediately before the rotation speed change which is affected by the error. For example, at the position D1=1023, D2=990, "D12
-k=1023-990-8=25'', so Rx=
0, and the correct position can be found. Further, even if the above equation (3-1) or (3-2) is applied in a region that is not affected by errors, the correct position can be found without any problem.

[0041] A malfunction similar to the above-mentioned malfunction associated with D12, which may occur immediately before or after each rotation, may also occur with respect to D13. However, D
In the case of 13, D12 has a carry (that is, D12 is N-
There is a possibility that such a malfunction may occur immediately before or after the switching from N=1 to N=0. Therefore, in order to improve this malfunction, D1 is
3 is not used as is, but is used with the following changes depending on the range of D12.

0≦D12≦511 (generally 0≦D12≦(N
/2)-1) Ry=(D13+k)÷(N/
n)...(8-1
) 512≦D12≦1023 (generally N/2≦
When D12≦N-1) Ry=(D13-k)÷(
N/n) …(8
-2) Above (3-1), (3-2), (8-1), (8
-2) In order to execute the formula, FIG. 2 may be changed as shown in FIG. 4. Adders 9 and 10 are provided between subtracters 5 and 6 and dividers 7 and 8, respectively, and comparators 11 and 34 determine which range D1 and D12 belong to, and the determination result is Accordingly, gates 12 or 13, 35 or 36 are opened to apply "+k" or "-k" to adders 9 and 10, and k is added to or subtracted from D12 and D13. In addition, the above (3-1), (3-2), (8-1), (8-2
It goes without saying that the range of D1 to which the equation ) is applied is limited to a relatively narrow range immediately before and after the rotation speed change, and equations (3) and (8) may be used in other ranges.

Note that if there are no errors in the encoder outputs D1, D2, and D3, errors such as those shown in FIGS. 3(b) and (c) will not occur; in that case, only errors such as those shown in FIG. 3(a) will occur. Needless to say, this should be taken into consideration. For that purpose, D1
determines whether it belongs to "0≦D1<N-n" or "N-n≦D1≦N-1", and in the former case, use the above equation (3) as is, and in the latter case, use the above (3) as is. In formula 3), "D12-1" may be used instead of D12. In that case, D
Similarly, regarding 13, “0≦D12<N-n” or “N
-n≦D12≦N-1”, and perform the above (8).
Use the formula as it is, or use "D13-" instead of D13 in the same formula.
1" may be used.

[0044] Rotary encoders RE1, RE2, RE
3, any absolute encoder can be used, such as a variable magnetic resistance type phase shift type rotation angle detection device as disclosed in Japanese Patent Laid-Open No. 57-70406. FIGS. 5 and 6 show an example in which the present invention is implemented using a variable magnetoresistive phase shift rotation angle detection device as disclosed in the above publication.

In FIG. 5, VRE1, VRE2, VR
E3 indicates a sensor portion (hereinafter simply referred to as an encoder) of the variable magnetoresistive phase shift rotation angle detection device, and corresponds to RE1, RE2, and RE3 in FIG. 1. Figure 6(a) shows these three encoders VREl.
, VRE2, and VRE3, and FIG. 3(b) is a radial cross-sectional view of one encoder VRE1. In FIG. 6(a), the first encoder VRE1 is shown in cross section, but the second and third encoders VRE2
, VRE3 are shown in side view. The diameters of VRE2 and VRE3 are approximately half of VRE1. VRE1 on main shaft 14
A rotor 15 is attached to the main shaft 14, and a gear 16 is provided at one end of the main shaft 14. This gear 16 is VRE2
A gear 17 provided on the rotating shaft 20 of the VRE 3 meshes with the gear 17, and a gear 18 further provided on the shaft 20 meshes with a gear 19 provided on the rotating shaft 21 of the VRE3. Gear 16, 17, 18, 19
The number of teeth is n, n-, the same as gears 1, 2, 3, and 4 in Fig. 1.
1, n+1, n.

22 is the casing of VRE1, 23, 24
is a bearing. 25 is a stator core of VRE1. As shown in FIG. 6(b), the encoder VRE1 includes a plurality of poles A, B, C, and D on the stator 25, and each pole A to D has primary coils 2A to 2D and secondary coils 3A to 3D. 3D
It is wrapped around. The rotor 15 is, for example, an eccentric rotor, and has a shape that changes the reluctance of each pole depending on the rotation angle. Poles A and C that form a pair in the radial direction
When one of the primary coils 2A and 2C of B and D is excited with a sine wave signal, and the other primary coil 2B and 2D is excited with a cosine wave signal, the following is the combined output Y1 of the secondary coils 3A to 3D. I get a signal. Other encoders VRE2,V
RE3 has a similar structure, and the following signals are obtained as secondary outputs Y2 and Y3.

Y1=sin(ωt-θ1)Y2=sin
(ωt-θ2) Y3=sin(ωt-θ3)
...(12) θ1, θ2, θ3 are each encoder VRE
The outputs Y1, Y2, and Y3 are obtained by phase-shifting the reference AC signal sinωt by a phase angle corresponding to each rotation angle. Therefore, these output signals Y1, Y2, Y
Absolute value data D1, which indicates the rotational position within one rotation by measuring the phase shifts θ1, θ2, θ3 in 3, respectively.
D2 and D3 are found respectively.

In FIG. 5, counter 27 counts the output clock pulses of clock oscillator 26. In FIG. A part of the count output is transmitted to the sine wave generator 28 and the cosine wave generator 2.
9, a sine wave signal sinωt and a cosine wave signal cos synchronized with the count output based on the count output.
ωt is generated. As described above, these signals are supplied to the primary side of each encoder VRE1 to VRE3. The secondary side output signals Y1, Y2, Y3 are applied to the gate circuit 30. The gate circuit 30 receives timing signals T1 and T2.
, T3, the signals Y1, Y2, and Y3 are selected in a time division manner, multiplexed, and applied to the load control input of the latch circuit 31. The latch circuit 31 latches the count value of the counter 27 in synchronization with the rising timing of the signal Y1, Y2, or Y3 applied from the gate circuit 30. The execution circuit 32 is controlled by a central processing unit (CPU) 33 to execute various functions. Each encoder VRE1
, VRE2, VRE3, and includes registers R1, R2, and R3 for storing outputs D1, D2, and D3 of VRE2 and VRE3. (which is known by the timing signals T1, T2, T3) in the corresponding register R1 or R2, R3. In the execution circuit 32, each register R1, R2
, R3, each encoder output D1, D2, D
3 and based on the predetermined calculation constants N, n, N/n, k, etc., the above formula (4) and (11) and (3-1) or (3-2) and (8-1) or The calculation of equation (8-2) and the accompanying comparative judgment of the range of D1 are performed, and data D1, R indicating the absolute rotational position in the range of n2 rotations is calculated.
Output x and Ry.

In the above embodiment, each encoder RE1 to RE
Although one period of the output signals D1 to D3 of No. 3 corresponds to one rotation of each rotor, the present invention is not limited to this.
It will be clear from the principles of the invention that encoders RE1-RE3 that generate output signals D1-D3 at multiple periods per rotation may be used. For example, when using encoders RE1 to RE3 that generate output signals D1 to D3 at nine cycles per rotation of each rotor (that is, those capable of absolute position detection within a rotation range of 40 degrees), One period in a) corresponds to 2π/9 radians, that is, 40 degrees instead of 2π radians, and the absolute detectable range for n2 periods is “(1024/9)·2π”. As an encoder that generates outputs of a plurality of periods per rotation, the encoder disclosed by the present applicant in Japanese Patent Laid-Open No. 57-88317 can be used.

[0050]

[Effects of the Invention] As described above, according to the present invention, a plurality of rotation detection sections each generating periodic rotational position detection signals each having a different period depending on the rotational displacement of the object to be detected are used, and the output signals of the rotation detection sections are In an absolute rotational position detection device that can obtain a rotational position detection signal with an expanded absolute position detection range by calculation, the structure of the rotation detection section is designed to be Since the magnetic resistance change is imparted by the rotor, there is no need for significant magnetization (permanent magnetization), and therefore manufacturing and processing are simple and cost-effective, and it is easy to use in the environment. This has the effect of not being subject to any restrictions. Also, the first and second
Since the stator and rotor portions of the rotation detecting section (furthermore, the third rotation detecting section) and the rotation transmitting means are integrally housed, one rotary unit equipped with one rotation input shaft This has the effect that the appearance of a detector can be given to the device, and the device can be assembled into a compact device as a whole, thereby realizing miniaturization and ease of use of the device. In addition, by providing three rotation detection units, the number of cycles of the first cycle number signal is further determined, so when a gear train is used as the transmission means, for example, the number of gear teeth can be increased. The absolute rotational position detection range can be expanded, and the mechanical structure can be simplified and smaller.
Absolute positions over an extremely wide range can be detected with high precision.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing the principle of an embodiment of the present invention.

FIG. 2 is a block diagram showing the principle of arithmetic processing in the same embodiment.

FIG. 3 is a diagram showing an example of the outputs of the first and second rotary encoders over time in order to explain the possibility of an error near a rotation speed switching point.

FIG. 4 is a block diagram showing the principle of an improved example of the arithmetic processing in FIG. 2;

FIG. 5 is a block diagram schematically showing an electrical processing system of an embodiment of the present invention when a variable magnetic resistance type rotation angle detector is used as a rotary encoder.

6(a) is an axial sectional view showing a structural example of three encoders in FIG. 5, and FIG. 6(b) is a radial sectional view of one encoder.

7A, 7B, and 7C are diagrams showing the state of the output signal of encoder 3 in FIG. 1 with the absolute position of the main axis on the horizontal axis and the value of the output signal on the vertical axis; (d) is a diagram showing the state of the difference between the output signals of the first encoder and the second encoder, with the absolute position of the main axis as the horizontal axis and the difference value as the vertical axis. 3 is a diagram illustrating the state of the difference between the output signals of the encoder No. 3, with the absolute position of the main axis on the horizontal axis and the difference value on the vertical axis. FIG.

[Explanation of symbols]

RE1, RE2, RE3...Rotary encoder, VRE
1, VRE2, VRE3... variable magnetic resistance type rotation angle detector, 1, 2, 3, 4, 16, 17, 18, 21... gear,
5, 6...Subtractor, 7, 8...Divider, D1, D2, D3...
Output of each encoder.

Claims (3)

[Claims] 1. A rotation transmitting means for imparting a rotational motion given to a rotational input shaft to a detection unit; a motion corresponding to the rotational displacement of the rotational input shaft is respectively imparted by the rotational transmission means; first and second rotation detection units each generating periodic rotational position detection signals in response to rotational displacement, and having a difference in rotational displacement amount of the input shaft corresponding to one cycle; Determining a difference between a first rotational position detection signal generated by the first rotation detection unit and a second rotational position detection signal generated by the second rotation detection unit,
Furthermore, a calculation means for performing a calculation to determine the number of periods from the origin regarding the first rotation detection section based on this difference and outputting a period number signal indicating the determined number of periods, each of the rotation detection sections: a stator including a plurality of primary coils and a plurality of secondary coils, and a stator that is rotationally displaced according to a given rotational displacement;
A rotor that gives a change in magnetic resistance to the magnetic circuit of the stator according to the rotational position, and each of the primary coils are excited with an alternating current signal with a phase shift, and an output signal having a phase shift according to the rotational position of the rotor is generated. It has a circuit that generates a signal in the secondary coil, and a circuit that measures the phase shift of this output signal and outputs it as the rotational position detection signal, and
An absolute rotational position detection device characterized in that the stator and rotor portions of the rotation detection section and the rotation transmission means are integrally housed. 2. Rotation transmitting means for applying a rotational motion applied to a rotational input shaft to a detection unit, the rotation transmission means respectively applying a motion corresponding to the rotational displacement of the rotational input shaft, Each generates a periodic rotational position detection signal according to the rotational displacement, and there is a difference in the amount of rotational displacement of the input shaft corresponding to one cycle, and the first rotation detection section and the second rotation detection section each generate a periodic rotational position detection signal. first, second and third rotation detecting sections, the difference between which is larger than the difference between the first rotation detecting section and the third rotation detecting section; The difference between the first rotational position detection signal generated by the rotation detection unit and the second rotational position detection signal generated by the second rotation detection unit is determined as a first difference, and based on this first difference, a first calculation means for performing a calculation to determine the number of periods from the origin regarding the first rotation detection section and outputting a first period number signal indicating the determined number of periods; The difference between the generated first rotational position detection signal and the third rotational position detection signal generated by the third rotation detection section is determined as a second difference, and the first period is determined based on this second difference. a second calculation means that performs a calculation to determine the number of periods of the number signal and outputs a second number of periods signal indicating the determined number of periods, and each of the rotation detectors has a plurality of primary coils and a second a stator having a primary coil; a rotor that is rotationally displaced according to a given rotational displacement and gives a change in magnetic resistance to the magnetic circuit of the stator according to the rotational position; A circuit that is excited by an alternating current signal and causes a secondary coil to generate an output signal having a phase shift according to the rotational position of the rotor, and a circuit that measures the phase shift of this output signal and outputs it as the rotational position detection signal. An absolute rotational position detection device comprising: a stator and a rotor portion of the first, second, and third rotation detection portions and the rotation transmission means; 3. The rotor rotation shaft of the first rotation detecting section is directly connected to the rotation input shaft and has a transmission ratio of 1, and the rotation transmission means has a gear train, and the 3. The absolute rotation position according to claim 2, wherein the rotation of the rotor rotation shaft of the first rotation detection section is transmitted to the rotor rotation shafts of the second and third rotation detection sections at different transmission ratios of less than 1, respectively. Detection device.