JPS60162918A - Multiple rotation absolute detector - Google Patents

Abstract

PURPOSE:To detect the absolute extent of rotation of a rotating body at low cost by providing the 1st rotation detector, a speed reduction gear which is connected thereto and has a constant ratio, and the 2nd rotation detector, and performing processing by a processor on the basis of their output signals and the speed reduction ratio. CONSTITUTION:A resolver 14 as the 1st rotation detector is coupled directly with the left end of a ball screw 10, a rotor coil is installed in a stator to generate a resolver signal, and the 2nd resolver 22 of the same structure is connected through the speed reduction gear 20. Both resolvers 14 and 22 are connected to a resolver signal digital converter 18 through a resolver signal switch 16 to send their output signals to a microcomputer 24. Then, the converter 18 connects with a carry-borrow detector 28 having an up/down counter 30 and necessary contents are read in the microcomputer 24. Consequently, the absolute extent of rotation of the 1st rotation detector is obtained by the inexpensive detectors.

Description

Detailed Description of the Invention Technical Field The present invention provides a multi-rotation absolute 1 capable of detecting the absolute amount of rotation of a rotating body rotating one or more revolutions from its original position without actually rotating the rotating body from its original position.・Regarding the detector.

Conventional technology multi-rotation absolute: 1. -1- The detector is used, for example, to absolutely detect the distance from the origin of a linearly moving member sent by a pole. By detecting the absolute amount of rotation of the pole screw from its original position, the position of the linearly moving member can be determined from the detection result and the holes of the hole screw.

Currently, an optical absolute encoder is used as a means to detect the absolute amount of rotation from the original position of a rotating body that is rotated multiple times, such as the above-mentioned pole screw, but this is generally expensive. However, those with a large number of rotations that can be detected are particularly expensive.

Purpose of the Invention The present invention is based on the background of 1N, and provides an inexpensive multi-rotation absolute detector that can absolutely detect the absolute amount of rotation from the original position of a rotating body that rotates many times. This was done for the purpose of

Structure of the Invention To achieve this object, the multi-rotation absolute detector according to the present invention is (a) a single-rotation absolute detector that generates an electrical output signal corresponding to an absolute rotation amount within one rotation; , a first rotation detector connected to the rotating body and rotated by the rotating body, and (b) a speed reducer connected to the first rotation detector and reducing the rotation of the first rotation detector at a constant reduction ratio. (C) a single-rotation abflush 1~detector similar to the first rotation detector, the second rotation detector connected to the reduction gear; (d+first and second rotation detectors); Based on the output signal from the device and the reduction ratio, determine the number of rotations of the first rotation detector from the original position, which is uniquely determined in response to the output signal of the second rotation detector,
From the number of rotations and the output signal of the first rotation detector, rjF
and a processing device that calculates the amount of one rotation of the Ilij body.

Effects of the Invention As described above, if the first rotation detector is connected to the rotating body whose amount of rotation is to be detected, and the second rotation detector is connected to the first rotation detector via the deceleration device, the rotation amount can be detected. The two-rotation detector rotates by an amount obtained by dividing the amount of rotation of the first rotation detector by the reduction ratio of the reduction gear. Conversely, if you multiply the rotation amount of the second rotation detector by the reduction ratio of the reduction gear, you can find the rotation amount of the first rotation detector, and from that rotation amount, you can calculate the rotation amount from the original position of the first rotation detector. You can measure the amount of rotation. Then, the sum of the rotation (2) and the indicated value of the current rotation (2) of the first rotation detector is the absolute rotation (2) of the first rotation detector from its original position.

That is, the multi-rotation absolute 1 and detector 2 of the present invention
It is possible to detect the absolute amount of rotation from the original position of a rotating body that rotates more than one revolution using a single-turn absolute detector.For example, an inexpensive single-turn absolute detector such as a resolver or an optical type Also, it becomes possible to use a relatively inexpensive one-turn absolute encoder, etc., and an inexpensive multi-turn absolute detector can be obtained.

In addition, the second rotation detector is provided to determine how many rotations the first rotation detector has made before reaching the current rotation position, and the detection accuracy of the absolute rotation amount of the rotating body is determined by the first rotation detection. The second rotation detector does not affect the detection accuracy. Therefore, alignment of the second rotation detector with respect to the first rotation detector does not need to be carried out very strictly, and high precision is not required for the holding device and deceleration device of the first rotation detector and the second rotation detector. Furthermore, the processing device that calculates the absolute rotation (1) of the rotating body from its original position based on the output signals from the first and second rotation detectors and the reduction ratio is an inexpensive processing device that uses, for example, a general-purpose microcomputer. It can be manufactured in a number of ways, and from this point of view as well, the effect of cost reduction is fully realized.

Although the multi-rotation Absolute 1 detector according to the present invention can be manufactured at low cost as in -J2, it can enjoy all the inherent advantages of the Abfluue 1 detector.

In other words, there is no need to perform the troublesome return-to-origin operation every time the device is started, unlike the case with incremental rotation detectors, and there is also no need for switches, control equipment, etc. for this operation, which reduces trouble. It is. In addition, there is no need to hack up the various memories of the processing device, and even in the event of a power outage, it is possible to start up the machine directly from the stopped position without having to return to the origin, such as sliding machine tools, etc. It can be widely used for controlling the position of, I rotor unloader device, robot I, etc.

EXAMPLE The following is an example in which the multi-rotation absolute detector of the present invention is used in a linearly moving member position detection device for absolutely detecting the absolute position of a linearly moving member moved by a ball screw, that is, the distance from the origin. This will be explained in detail based on the figures.

FIG. 1 is a perspective view schematically showing a mechanical part of a linearly moving member position detection device, and in the figure, reference numeral 10 does not indicate a ball screw. The ball screw 10 is rotatably but immovably attached to the main body of the machine tool by a bearing member (not shown), and is connected to a drive source at the right end as shown in the figure, and is moved by being rotationally driven. The member 12 is moved back and forth in a linear direction.

A resolver 14 as a first rotation detector is directly connected to the left end of the ball screw 10 so that it rotates at the same speed as the ball screw 10. In the first resolver 14, a rotor having a rotor coil is rotatably disposed in a stator having a stator coil, and when the rotor is rotated in the excitation state of the rotor coil, the terminal of the stator coil is It generates a resolver signal, which is an electrical signal corresponding to the rotational position of the rotor. As shown in FIG. 2, this first resolver 14 is connected to a resolver signal digital converter (hereinafter abbreviated as an R/D converter) 18 via a resolver signal switch 16. R
The /D converter 18 emits a digital signal corresponding to one rotational position of the first resolver 14 based on the resolver signal from the first resolver 14, and in this embodiment, the digital signal corresponds to one rotation of the rotor. 212 digital signals are emitted, and together with the first resolver 14, constitutes a one-rotation absolute detector which is a first rotation detector.

A second resolver 22 is further connected to the ball screw 10 via a reduction gear device 20. In FIG. 1, the speed reduction device 20 is illustrated as a simple gear train for easy understanding, but in reality, this speed reduction device 20 requires a large reduction ratio, so for example, a harmonic gear train is used.
A 'ii star gear reduction device commercially available under the trade name of Live is suitable.The second resolver 22 is the first resolver 1.
4, but as is clear from FIG.
Both are connected to the R/D converter 18 of 1JTI. The resolver signal switch I6 selectively switches between the resolver signal from the first resolver I4 and the resolver signal from the second resolver 22 based on a command from the microcomputer 24.
/D converter 18, and the microcomputer 24 outputs digital signals corresponding to the resolver signals from the first resolver 14 and the second resolver 22 (hereinafter, the digital signals are supplied to the first resolver 14 and the second resolver 22, respectively) when necessary. R/D
It is adapted to be readable from the converter 18. In addition,
26 is an excitation circuit for exciting the rotor coils of both the resolvers 14 and 22.

0 The R/D converter 18 further includes a carry-borrow detector 2.
8 are connected. This carry-borrow detector 28 emits an associative same signal when the content of the digital signal of the R/D converter 18 transitions from a full number 1~ to zero, and conversely, when it transitions from zero to a full number i. 1
It emits down clock signals. An up-down counter 30 is connected to this carry-borrow detector 28, and this further includes a microcomputer 2.
Connected to 4. The up/down counter 30 records the numerical value supplied from the microcomputer 24. a, and each time one up clock signal is issued from the carry poll r:1-detector 28, the value is increased by 1, and each time a down clock signal is issued, the value is decreased by 1, and this up down counter 30
The contents can be read into the microcomputer 24 when necessary.

The microcomputer 24 is further connected to a human power device 32 equipped with various keys and operation buttons, and a display 34 for displaying instructions to the operator from the microphone 1, 0τ1, 24 and position detection results. has been done.

Further, the first resolver 14 and the second resolver 22 are provided with a mounting flange 38 at the tip, as shown in FIG.
It is fixed to the machine tool main body by 42 to 0 and 1, and can be easily mounted to the machine tool main body by loosening the bolt 42 and releasing the tightening of the mounting flange 38 by the fixing part plate 40. The position can be adjusted by one angle.

Before explaining the operation of the position detection device constructed as described above, the principle of operation of this device will be explained based on FIG. 4.

In FIG. 4, the straight line T, 1 indicates the mechanical movement limit position at which the movable member 12 comes into contact with a stopper and is prevented from moving further, and the straight line L2 indicates the origin position of the position detection device. . Further, the first digital value, that is, the digital output value of the first resolver 14 is represented on the horizontal straight lines 1 and 3, and the second digital value, that is, the digital output value of the second resolver 22 is represented on the straight line - 44''-.

It is assumed that the origin of the first resolver 14 is aligned with the origin 0 of the moving part + and J12, the origin of the second resolver 22 is aligned with the mechanical movement limit position, and the current position of the moving member 12 is at point A. If the position is as shown, the digital output value of the first resolver 14 will indicate the distance Mlt a , and the digital output value of the second resolver 22 will indicate the distance a2. The digital output value of the second resolver 22 represents the current position of the moving member 12 (however, it is not a position based on the origin 0, but a position based on the straight line L1), but its accuracy is low. On the other hand, although the output value of the first resolver 14 has high accuracy, it only represents the position from point B, not the position from the origin 0. The position of this point B with respect to the origin O is the first resolver 14
Although it is known that this is an integer 0 times the output value Y corresponding to one rotation of the integer n, it is not possible to know the value 3 from only the output value of the ε-th rezurper 14.

However, this integer n is the output value a1 of the first resolver 14.
can be intertwined with the output value a2 of the second resolver 22 and the reduction ratio N of the reduction gear device 20.

That is, the amount of rotation of the second resolver 22 is equal to the amount of rotation of the first resolver I.
Since the rotation amount is 1/N of the rotation amount of 4, the following equation holds true as is clear from FIG.

a2=Z→-n Y/N +a 1/N ---
-(1, but here Z is a ball 10.
This is a value that should be appropriately selected according to the circumstances of the mechanical parts such as the moving member 12 and the stopper, and here, assuming that z = 3 Y / 2 N −−−−−−−−+21 is selected. , the above formula (1) is a2
=3Y/2N+nY/N+a, /N-(3).

In this equation (3), since the reduction ratio N of the reduction gear 20 and the output value Y corresponding to one revolution of the first resolver 14 are known in advance, the output value a1 of the first resolver 14 is
By substituting the output value a42 of the second resolver 22, the integer n is uniquely determined. Therefore, the output value a of the first resolver 14 and the second resolver 22
From the output value a2 of
1-a, will be determined accurately.

Based on the above principle, the operation of the embodiment apparatus will be explained with reference to flowcharts 1 to 7 shown in FIGS. 5 to 7.

FIG. 5 is a flowchart of a main program that controls the overall operation of the apparatus of this embodiment. When the power is turned on, normal initial reset, self-diagnosis, etc. are automatically executed in step S1.

Subsequently, in step S2, the home position alignment-U flag is cleared, which is provided for the purpose of aligning the origin positions of the first resolver 14 and the second resolver 22. Subsequently, the position detection unit reset I subroutine in step S3 is executed, which will be described in detail later. Thereafter, various steps are executed, and in step S4, it is determined whether or not the original position adjustment button of the input device 32 is operated.
If it has been operated, the program execution will be at step S.
After the process moves to step S5 and the original position alignment flag is set, the original position alignment subroutine of step S6 is executed.

This subroutine of step S6 is executed with the movable member 12 positioned at the origin, as shown in FIG.

That is, in step S7, the resolver signal switch 1
6 is instructed to select the first resolver 14,
In step S8, a display indicating that the first resolver 14 is selected is displayed on the display 34, and the digital output value of the first resolver 14 is displayed on the microcomputer 2.
4, and the value is displayed on the display 34. Thereafter, in step S9, it is determined whether or not the cent completion button of the input device 32 has been operated. If it has not been operated, the program execution returns to step s8, and steps 886 and S9 are executed until the cent completion button is operated. is repeated.

While this execution is repeated, if the operator loosens the bolt 42 of the fixing member 40 fixing the first resolver 14 and changes the mounting angle position of the first resolver 14 with respect to the machine tool body, the Since the displayed value on the display 34 changes, when this displayed value becomes O, tighten the port 42 to fix the first resolver 14, and operate the cent complete button to adjust the original position of the first resolver 14. finish.

Thereafter, steps SIO, Sll, and S12 are similarly executed to adjust the original position of the second resolver 22. However, in this case, the mounting angle position of the second resolver 22 relative to the machine body is adjusted so that the displayed value on the display 34 is not 0 but 3Y/2N as described above.

In this way, the original position alignment of the first resolver 14 and the second resolver 22 can be performed extremely easily, and once this original position alignment is completed, the program execution returns to step S3 in the main routine of FIG. , by executing the position detection unit reset subroutine in step S3, the display 3
4, the current position (here, the origin position) of the movable member 12 is displayed, and thereafter, the absolute position that changes every moment as the movable member 12 moves will be displayed on the display 34.

This position detecting section reset subroutine is as shown in FIG. 7, and this subroutine will be explained in detail below. However, this subroutine is executed independently of the original position alignment subroutine described above even when the power is turned on after the position detection device is put into use.
Rather, since it is provided for that purpose, we will first explain the case where the moving member 12 is in the general position represented by point A in FIG. A case in which this position detection unit reset subroutine is executed will be explained.

In step 313, the second resolver 22 is selected,
In step 314, the output value a2 of the second resolver 282 is stored in the a2 memory. however,
This step S]4 is executed after a sufficient period of time, for example about several m5ec, has elapsed after the resolver signal switch 16 was activated.

Subsequently, steps S15 and S16 are similarly executed, and the output value of the first resolver 14 is stored in the a1 memory.

After that, steps S17 to S22 are executed, and n that satisfies the above equation (3) is determined. Note that step S1
9 should theoretically be O, but in reality, the first resolver 14 and the second resolver 22
0 because an error of several counts occurs when the original position cent.
It won't be. Therefore, in step S20, it is not determined whether the calculation result in step S19 is O or not, but rather
A determination is made as to whether or not it is within 10, and if it is within ±10, it is determined that n that satisfies equation (3) has been obtained. Also, when calculating n, set n to 0.
By increasing 1 by 1 from (Although this will result in more than one rotation, in reality, the specifications are set to prevent it from rotating more than one rotation, so this is not a problem), Step S
If it is discovered in step S21 that such a situation has occurred, the program execution moves to step S23, where the original position alignment error flag is set, a message to that effect is displayed on the display 34, and the program execution ends at step S23. Return to the main program shown in Figure 5. Therefore, the operator operates the original position adjustment button and performs the original position adjustment work in steps S5 and S6.

After the integer n (the number of rotations of the first resolver 14) that satisfies equation (3) is determined as follows, step S2
4 and S25 are executed, and an integer m greater than n by 2
is set in the up/down counter 30. This means that when the value of the integer n itself is entered in the up-down counter 30, when the moving member 12 moves in the negative direction from the origin O, the content of the up-down counter 30 becomes negative and data processing is performed. This is to avoid any trouble.

Therefore, when the moving member 12 is at the origin position, a
The content of 1 memory becomes O, or the content of m memory becomes 2. The contents of the up-down counter 30 indicate how many rotations of the pole screw 10 the current position of the moving member 12 corresponds to (actually, it is a value that is n plus 2, so it is 2 times less than the actual number of rotations of the ball screw 10). 1 of the first resolver 14, which is read moment by moment during position detection by the device of this embodiment after the execution of the position detection section reset subroutine currently being explained.
This functions as upper-level data of the 2-hit data.

Therefore, the current position of the movable member 12 is now in a state where it can be absolutely detected by the above two steps.
Actually, after the output value of the first resolver 14 is stored in the a□ memory in step S16, the output value of the first resolver 14 is stored in the up/down counter 30 in step S25 within a very short time. may vary between 0 and a full count of 1. In such a case, an extremely large reading error will occur, so in this embodiment, a check is made between steps S16 and S25 to see if such an occurrence has occurred.
If such a reading error occurs, correction of such a reading error is automatically performed. Steps S26 to S29 are the steps for this check, and step S
30 to S32 are the correction steps. The check is performed using extended data (D, D2) in step S, in which the output value D1 of the up-down counter 30 read in step S326 is used as upper data, and the output value D2 of the first resolver 14 read in step S27 is used as lower data.
24, the value m stored in the m memory is used as the upper data, and in step S]6, the output value a1 of the first resolver 14 stored in the memory is used as the lower data. This is done by determining whether or not it is out of line. That is, step S28
In step S29, the difference between the extended data (D, .D22) and the extended data (m-a,) is calculated, and in step S29 it is determined whether the calculated result is within ±100. If the calculation result is within ±100, it is determined that the above-mentioned inconvenience did not occur, but if it exceeds ±100, it is determined that the above-mentioned inconvenience has occurred. , step S
The correction is made at 30-32. That is, in step S30, it is determined whether or not the calculation result in step S28 is greater than 100. If it is greater than 100, it is determined that the current position of the movable member 12 has been excessively read due to a reading error, and step S31 is performed. At this point, the contents of the amplifier down counter 30 are decremented by one. Also, the calculation result of step 328 is minus 100.
If it is smaller, it is determined that the current position of the moving member 12 has been read too small due to a reading error, and the process proceeds to step S3.
2, the contents of the amplifier down counter 30 are incremented by one. After that, the program execution is at step S
26, the same thing is executed, but in this case, the determination result in step S29 should be YF, S, and the program execution moves to step S33.

In step 333, it is determined whether or not the original position alignment flag is set, but since this flag is not set in normal use, the original position alignment error flag is cleared in step S34. (If this flag is not set, no change will occur), and the execution of the position detection unit reset subroutine ends.

The case where the position detection section reset subroutine is executed in a state where the moving member 12 is placed at a general position other than the origin position has been described above.
A case will be described in which the original position adjustment button is operated and the position detection section resetting subroutine is executed after the original position adjustment subroutine is executed.

In this case, the moving member 12 is positioned at the origin, and the first resolver 14 and the second resolver 22 have been temporarily aligned in their original positions by line 4 of the original position adjustment subroutine. After 0 is stored in the n memory in step S18, the result of the first determination in step 320 is usually YES. Therefore, from now on, steps S24 to 332 are executed with the integer n being O.
In this case, since the original position alignment flag has been set in step S5, the determination result in step S33 is YES, and steps S35 and 336 are executed to determine whether or not the original position alignment has been performed with sufficient accuracy. A judgment is made. That is, the determination result in step 320 is YES with the moving member 12 positioned at the origin.
If so, it means that the original position alignment has been performed with a certain degree of accuracy, but this step 320 is originally a step for determining whether or not the original position alignment has been performed with sufficient accuracy.
Since this is a step executed to know the general current position of the moving member 12, rather than a step, a wide margin of ±10 is set. On the other hand, since it is desirable that the original position 5 alignment be performed with even higher accuracy, the accuracy of the original position alignment is checked with a narrow margin of ±5 in step S36. Then, if the determination result in step 336 is NO,
The execution of the program moves to step S23, where the original position alignment-U abnormality flag is set, and a message to that effect is displayed on the display 34.If the determination result at step S36 is YES, the original position alignment is performed. This means that the original position alignment has been performed with sufficient accuracy, and the original position alignment abnormality flag is cleared in step S34, and the execution of the position detection unit reset subroutine (step S3) associated with the original position alignment work ends.

- In the detailed embodiment, the one-rotation absolute detector constituting the first rotation detector is connected to the first resolver 14.
and an R/D converter 18, and a one-rotation absolute detector constituting the second rotation detector consists of a second resolver 22 and an R/D converter 18. That is, two digital rotary absolute detectors are constructed by the inexpensive resolver 21 [1i1 and one R6/D converter commonly used for them, and this embodiment uses an optical absolute detector. This has the unique advantage that a multi-U rotation absolute detector can be constructed at a lower cost than when two encoders are used.

7 However, even when an optical absolute encoder is used as a digital crew rotational absolute detector, the equipment cost is still quite low compared to when an optical multi-rotation absolute encoder is used. The effects of the present invention can also be achieved by using two encoders.

Furthermore, the present invention can of course be used not only to detect the absolute position of a moving member that moves linearly, but also to detect the rotational position itself of a rotating body that rotates many times.

Further, in the embodiment, the number of rotations of the first rotation detector from the original position is calculated from the output value of the first rotation detector, the output value of the second rotation detector, and the reduction ratio of the reduction gear; By using this as higher-order data of the 12 Hiso 1-data which is the output value of the first rotation detector, the absolute amount of rotation of the rotating body from its original position can be calculated. However, the absolute rotation of a rotating body is not limited to this.
For example, a table in which numerical values that are integral multiples of the number 8 corresponding to one rotation of the first rotation detector are arranged in order of size is stored in advance in the storage device of the microcomputer, and the output value of the second rotation detector is stored in advance. Calculate the product with the reduction ratio of the reduction gear, select a value smaller than the calculation result and closest to the calculation result from the table above, and add this and the output value of the first rotation detector. The absolute amount of rotation of the rotating body can also be determined by the following, and the present invention also includes this aspect.

Other mechanical parts such as reduction gears, electronic control circuits.

It goes without saying that the present invention can be implemented with various modifications and improvements made to the control program and the like based on the knowledge of those skilled in the art.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the principle of a mechanical part of a linear moving member position detection device using a multi-rotation abflush 1 to a detector, which is an embodiment of the present invention, and FIG. 2 is a perspective view showing the electronic control of the device. It is a block diagram of a circuit. FIG. 3 is a perspective view showing the resolver fixing means in the apparatus shown in FIG. 1. FIG. 4 is a diagram for explaining the operating principle of the apparatus shown in FIGS. 1, 9, and 3. FIG. 5 to 7 are flowcharts showing selected portions of the control program pre-stored in the microcomputer of the above-described embodiment apparatus, which are necessary for understanding the present invention. 10: Hall screw 12: Moving member 14: First resolver 16; Resolver signal switch 18; Resolver signal digital converter (R/D converter) 20: Reduction device 22: Second resolver 24: Microcomputer 28: Carry borrow detector 30 Near tube down counter 34: Display 38: Mounting flange 40: Fixing member Applicant: Fuji Machine Manufacturing Co., Ltd. 0 Figure 1 Figure 2 Figure 4

Claims (3)

[Claims] (1) One rotation amount" A device that detects the absolute rotation amount of a rotating body that rotates one rotation from its original position, and is a one-rotation absolute detector that generates an electrical output signal corresponding to the absolute rotation amount within one rotation. a first rotation detector connected to the rotating body and rotated by the rotating body; and a speed reduction device connected to the first rotation detector and configured to reduce the rotation of the first rotation detector at a constant reduction ratio. a one-rotation absolute-1 detector similar to the first rotation detector and connected to the reduction gear; and outputs from the first and second rotation detectors. Based on the signal and the reduction ratio, determine the number of rotations of the first rotation detector from the original position that is uniquely determined in response to the output signal of the second rotation detector, and calculate the number of rotations and the first rotation detector. A multi-rotation absolute 1 detector including a processing device that calculates the absolute rotation amount of the rotating body from the output signal of the rotating body. (2) The first and second rotation detectors are first and second resolvers, respectively, and the processing device is an R/D converter that converts a resolver signal into a digital signal; a resolver signal switch that selectively inputs output signals of the first resolver and the second resolver to a converter; and output signals of the first resolver and the second resolver supplied via the R/D converter. The number of rotations of the first resolver is calculated from a first digital signal and a second digital signal corresponding to 2. The multi-rotation absolute detector according to claim 1, further comprising an arithmetic device for calculating the absolute rotation amount of the multi-rotation absolute detector. (3) the first and second rotation detectors are first and second optical absolute encoders that generate first and second digital output signals, respectively, and the processing device is a The second digital faith,
A patent claim that is a calculation device that calculates the number of rotations of a first optical absolute encoder from the reduction ratio stored in advance, and calculates the absolute rotation amount of the rotating body from the calculation result and a first digital signal. The range of the multi-rotation ab flue 1 to the detector according to item 1.