JP2004347612A - Abnormality detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect a position and to simultaneously also detect abnormality without newly providing an abnormality detection circuit, and to configure a device at low cost. <P>SOLUTION: This abnormality detection device has: a position sensor 10 supplied with an excitation signal having a prescribed periodic waveform, outputting first and second amplitude-modulated signals induced according to a detection position from first and second output windings; a phase shift means 23 or 24 electrically shifting a phase of one of the first amplitude-modulated signal and the second amplitude-modulated signal by a prescribed angle; conversion means 17-20 adding or subtracting the other of the first amplitude-modulated signal and the second amplitude-modulated signal to/from a signal outputted from the phase shift means to convert it into a phase-modulated signal; an arithmetic means 22 finding the detection position by detecting a phase of the phase-modulated signal outputted from the conversion means; and an abnormality decision means 21 deciding whether position detection operation is abnormal or not, by detecting the phase. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

    The present invention relates to an abnormality detection device, and more particularly to a resolver for detecting a position or a device for detecting a rotational position such as a synchro, and more particularly, to an abnormality for detecting a motor position for driving a brushless motor. It relates to a detection device.

  FIG. 7 shows a conventional position detecting device of this type (for example, see Patent Document 1). In FIG. 7, an excitation signal (sin ωt), which is a sine wave voltage for excitation, is input from an oscillation circuit 22 that generates an excitation signal based on a clock of a counter 12 to a position sensor 10 constituted by a resolver, for example. The excitation signal is output from the position sensor 10 in accordance with the rotational position θ, cos θ, an induced signal sin θ sin (ωt ± α) amplitude-modulated by sinθ, and cosθsin (ωt ± α). Here, α represents the phase fluctuation error of the output signal with respect to the excitation signal due to a change in the temperature from the path from the position sensor 10 to the position detection circuit or the position sensor winding.

  When one of the output signals sin θ sin (ωt ± α) is shifted by a predetermined value of 90 ° by the phase shift circuit 14, the phase shift output becomes sin θcos (ωt ± α). When the phase shift signal and the other output signal cos θ sin (ωt ± α) from the position sensor 10 are added by an addition circuit, an addition signal sin (ωt + θ ± α) is output. Similarly, when the phase shift signal and the other output signal cos θ sin (ωt ± α) output from the position sensor 10 are subtracted by a subtraction circuit, a subtraction signal sin (ωt−θ ± α) is output.

  Here, the excitation signal (sinωt) which is a reference signal is counted based on the counter 12. That is, since the count is counted as one cycle from 0 to 360 deg, the zero-cross point of the addition signal sin (ωt + θ ± α) is detected by the zero-cross detection circuit 17, and the data D1 latched by the latch circuit 19 is + θ ± α. Similarly, the zero-cross point of the subtraction signal sin (ωt−θ ± α) is detected by the zero-cross detection circuit 18, and the data D2 latched by the latch circuit 20 becomes −θ ± α. Further, in the error calculation circuit 21, (D1 + D2) / 2 becomes ± α as described above. Therefore, the phase variation error ± α can be calculated. The subtraction circuit 22 subtracts the data D1 from the phase variation error ± α to obtain θ, and the position θ excluding the phase variation error ± α can be extracted.

JP-A-9-126809

  In Japanese Patent Application Laid-Open No. Hei 9-126809, since the above configuration is adopted, when the position detection circuit fails for some reason, particularly when the phase shift circuit 14 fails and the phase shift is stopped, the addition signal is output. Is sin θ sin (ωt ± α) + cos θ sin (ωt ± α) = (sin θ + cos θ) sin (ωt ± α), and the subtraction signal is sin θ sin (ωt ± α) −cos θ sin (ωt ± α) = (sin θ−cos θ) sin (Ωt ± α). Therefore, the data D1 becomes ± α or 180deg ± α except when θ is 135 deg and 315deg, and the counter D2 becomes 180deg ± α or ± α except for 45deg and 225deg. . Therefore, θ detects one of ± α, 90 ° ± α, 180 ° ± α, and 270 ° ± α. Here, for simplicity, if α = 0, the relationship between the original position (for example, the motor rotation position) and the detected position is as shown in FIG. The error is a maximum of 135 deg. When the brushless synchronous machine is used as a motor rotational position detecting device for driving, there is a possibility that a malfunction such as driving in the opposite direction to the original driving direction may occur. In order to avoid this, two position detecting devices are provided, and it is proposed to determine whether a failure has occurred by comparing them. However, since two position detecting devices themselves are required, the cost is high.

  Further, to calculate the position θ, it is necessary to once calculate the phase variation error ± α, and to perform an arithmetic process for excluding the position variation error, so that the configuration circuit becomes complicated and expensive.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide an abnormality detection device that can minimize the influence of a failure even if a phase shift circuit fails.

  According to the present invention, an excitation signal having a predetermined periodic waveform is supplied, a first amplitude modulation signal induced from a first output winding according to a detection position is output, and a detection signal is detected from a second output winding. A position sensor that outputs a second amplitude modulation signal induced according to a position, and a phase shifter that electrically shifts one of the first amplitude modulation signal and the second amplitude modulation signal by a predetermined angle. Means for converting the other of the first amplitude modulation signal and the second amplitude modulation signal into a phase modulation signal by adding or subtracting the signal output from the phase shifting means to the phase modulation signal; An abnormality comprising: arithmetic means for obtaining a detection position by detecting the phase of the output phase modulation signal; and abnormality determination means for detecting whether or not the position detection operation is abnormal by detecting the phase. Detector A.

  According to the present invention, an excitation signal having a predetermined periodic waveform is supplied, a first amplitude modulation signal induced from a first output winding according to a detection position is output, and a detection signal is detected from a second output winding. A position sensor that outputs a second amplitude modulation signal induced according to a position, and a phase shifter that electrically shifts one of the first amplitude modulation signal and the second amplitude modulation signal by a predetermined angle. Means for converting the other of the first amplitude modulation signal and the second amplitude modulation signal into a phase modulation signal by adding or subtracting the signal output from the phase shifting means to the phase modulation signal; An abnormality comprising: arithmetic means for obtaining a detection position by detecting the phase of the output phase modulation signal; and abnormality determination means for detecting whether or not the position detection operation is abnormal by detecting the phase. Detector Because, without providing a new abnormality detection circuit can be detected combined simultaneously anomaly upon detection position, it is possible to construct a low cost device.

Embodiment 1 FIG.
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram showing the configuration of the position detection device (abnormality detection device) of the present invention. In the figure, reference numeral 10 denotes a one-phase excitation input / two-phase output type position sensor, which may be constituted by, for example, a resolver or the like, and is not limited thereto, and may be any type of position sensor. . When supplying an excitation signal having a predetermined frequency shape, the position sensor 10 outputs, from the first and second output windings, amplitude modulation signals amplitude-modulated by cos θ and sin θ according to the detected position. . Reference numeral 12 denotes a counter that generates a clock signal. Reference numeral 22 denotes an oscillation circuit that inputs an excitation signal having the above-described predetermined frequency to the position sensor 10 based on the clock signal from the counter 12. Reference numerals 23 and 24 denote phase shift circuits that electrically shift the phase of the amplitude modulation signal output from the position sensor 10 by a predetermined angle. Reference numeral 15 denotes an addition circuit for adding the signal output from the phase shift circuit 23 and the signal output from the phase shift circuit 24, and 16 denotes subtraction for subtracting the signal output from the phase shift circuit 23 and the signal output from the phase shift circuit 24. Circuit. Reference numerals 17 and 18 are zero-cross detection circuits to which output signals of the addition circuit 15 and the subtraction circuit 16 are input, respectively, and which detect a zero cross of the input signals. Reference numerals 19 and 20 denote zero-cross detection pulses detected by the respective zero-cross detection circuits 17 and 18, that is, zero-phase detection pulses in which the amplitude value of each signal changes from negative to positive as latch pulses. This is a latch circuit that latches the count value of the counter 12 at a timing. The data D1 and D2 latched by the latch circuits 19 and 20, respectively, correspond to the phase shifts of the output signals of the adder 15 and the subtractor 16 with respect to the reference sine signal sinωt. Reference numeral 21 denotes an error calculation circuit which receives the data D1 and D2 latched by the respective latch circuits 19 and 20, and obtains a phase variation error β by calculating “(D1 + D2) / 2 (= β)”. 22, the data D1 latched in one latch circuit 19 and the value β obtained by the error calculation circuit 21 are input and subtraction of “D1−β (= θ)” is performed to remove the phase fluctuation error β. The subtraction circuit outputs the correct detected position θ.

  Next, the operation will be described. First, similarly to the conventional example of FIG. 7, by inputting an excitation signal sinωt to the position sensor 10 by the oscillation circuit 22, an induced signal, that is, an amplitude modulation signal sinθsin (ωt ± α) and cosθsin (ωt ± α) is output. Therefore, in the conventional example, as shown in FIG. 7, a phase shift circuit 14 is provided on one of the two sides, and input is performed. Is input to the adding circuit 15 and the subtracting circuit 16 through the first phase shift circuit 23, and the other output signal from the position sensor 10 is input to the adding circuit 15 and the subtracting circuit 16 through the second phase shifting circuit 24. input. However, the electrical phase relationship between the first phase shift circuit 23 and the second phase shift circuit 24 is set so as to shift the phase shift by 90 degrees relatively. For example, in the phase shift circuit 23, the phase is shifted by +45 deg and the output is sin θ sin (ωt ± α + 45 deg), and in the other phase shift circuit 24, the phase is shifted by −45 deg and cos θ sin (ωt ± α−45 deg). Here, if ± α−45 deg is β, the output of the first phase shift circuit 23 is sin θ sin (ωt ± β + 90 deg) = sin θcos (ωt ± β), and the output of the second phase shift circuit 24 is cos θ sin (Ωt ± β). The output signal of the addition circuit 15 is sin (ωt ± β + θ), and the output signal of the subtraction circuit 16 is sin (ωt ± β−θ). As described above, the signals output from the phase shift circuits 23 and 24 are added or subtracted by the adder circuit 15 and the subtractor circuit 16 so that the phase modulation signals sin (ωt ± β + θ) and sin (ωt ± β−θ) are obtained. Is converted to Thereafter, data D1 and data D2 are calculated through the zero-cross detection circuits 17 and 18 and the latch circuits 19 and 20, as in the conventional example. In the zero-cross detection, either one of the rising edge and the falling edge is detected. This makes it possible to calculate θ by the arithmetic circuits 21 and 22. Further, by providing a process of calculating (D1 + D2) / 2, it is possible to detect (D1-D2) / 2 = θ and the position θ.

  β may be considered to be a phase variation error obtained by adding +45 deg set to α by the phase shift circuit. If the phase variation variation error of the conventional example is considered as β−45 deg, ± α is the same as the conventional example. Since the error fluctuation has characteristics, it can be handled as temperature detection data. Therefore, if the relationship between the phase variation error and the temperature is set in advance, the temperature is measured by detecting the position variation error. For example, a position sensor provided with the motor can measure the temperature of the motor or the ambient temperature of the motor. Therefore, when the motor is exposed to a high temperature, or is generating heat at a high temperature, and if the temperature rises further, there is a possibility that the motor will break down, the motor for driving the motor based on the position variation error is used. Control is performed so as to limit or stop the current, thereby preventing a motor failure.

  In general, when a circuit breaks down, it is extremely unlikely that two places will break down at the same time. Usually, in Failure Mode and Effects Analysis of a device, analysis is performed by focusing on only one place. Therefore, in the present invention, it is only necessary to assume that one of the phase shift circuits has failed. Assuming that the second phase shift circuit 24 has failed and the phase has not been shifted, cos θ sin (ωt ± α) is obtained. Therefore, the addition circuit 15 outputs sin θ sin (ωt ± α + 45 deg) + cos θ sin (ωt ± α), and the subtraction circuit 16 outputs sin θsin (ωt ± α + 45 deg) −cos θ sin (ωt ± α). At this time, for simplicity, if α = 0, the relationship between the original position (for example, the motor rotation position) and the detected position is as shown in FIG. As shown in FIG. 2, the error in the detected position is smaller than that in FIG. 8 showing the position detection when a failure occurs in the conventional example of FIG. As described above, the error is small if the relative phase shift angle is close to the desired angle, and the error is large if the relative phase shift angle is large. Therefore, as in the present invention, by providing a phase shift circuit for both phases of the winding output signal, even if one fails, the other phase is shifted, so that the position detection error is reduced by the other phase shift. The error can be reduced by the phase angle. Since there are two phase shift circuits and the probability of failure is the same, the same phase shift angle should be set, and when the position sensor attempts to transfer the orthogonal amplitude modulation signal to convert it to a phase modulation signal, Since the relative phase shift angle is 90 deg, which is divided into two, when the two phase shift angles are set to ± 45 deg, it is possible to minimize the influence at the time of failure. For example, even if a motor rotation position is used as a detection device in a device that drives a brushless synchronous machine, the motor drive does not drive in the reverse direction, and the effect of malfunction is negligible.

  When an error occurs in the position detection device and an error occurs in the position detection as shown in FIG. 2, similarly, the phase fluctuation error fluctuates depending on the position as shown in FIG. As can be seen from this, the phase fluctuation error in the normal state depends on the temperature, and thus the temperature rise does not suddenly occur but changes gradually. However, when an abnormality occurs, the phase changes suddenly from the normal state to the abnormal state, so that the phase fluctuation error also changes rapidly. By capturing this, it is possible to determine that the position detection device has become abnormal. In addition, in systems where the position changes constantly because the phase fluctuation error changes depending on the position, those that gradually change with temperature during normal operation are detected because the phase fluctuation error changes according to the position during abnormal operation. By doing so, it can be determined that there is an abnormality. Thus, the position detection device of the present invention can be used as an abnormality detection device.

  Further, when the amount of change in the phase variation error within the temperature range in which the position sensor or the position detection device is used, that is, when the variation range of the phase variation error is small, as shown in FIG. If a phase fluctuation error occurs, it is possible to determine that there is an abnormality. Even if the position falls within the range of phase fluctuation, as can be seen by comparing FIGS. 2 and 6, when the error of position detection is small at the time of abnormality, the phase fluctuation error is also small. That is, when the phase fluctuation error is within the fluctuation range, the error of the position detection is small even if the abnormality cannot be detected, so that the influence of the error is further reduced.

  The method of detecting an abnormality of the position detecting device can be applied not only to the present invention but also to a conventional example having only one phase shift circuit. That is, the present invention aims at minimizing the influence of position detection due to a failure by providing two phase shift circuits, but the same applies to phase fluctuation errors. Therefore, in a conventional device in which the phase shift means is provided for only one phase, the phase fluctuation error appears as a larger fluctuation at the time of failure, and the abnormality detection becomes easier.

  In the case where the apparatus is used as a position detecting device for driving a motor, when the abnormality is determined as described above, the malfunction of the motor can be prevented by stopping the driving of the motor.

  In addition, zero cross detection is assumed to detect either rising or falling, but it is also possible to detect both. In this case, since it is a half cycle, the detected count is doubled to calculate. There is a need to. In addition, it is also possible to perform the operation by latching the addition circuits 15 and the subtraction circuit 16 in the rising directions of the addition circuits and the latching of the addition circuits 15 and the subtraction circuits 16 in the falling directions thereof. By utilizing both the rising and falling edges, the position can be detected only in the oscillation cycle in the past, but the position can be detected every half cycle, so that the position can be detected at a higher speed. Furthermore, although detection has been proposed to be detected at a zero-crossing point, detection may be performed by providing hysteresis at the zero-crossing point in order to prevent erroneous detection due to noise received on the circuit or failure of the device.

  As described above, the position detection circuit (abnormality detection device) according to the present embodiment can minimize the influence of the failure even if the phase shift circuit fails, and the motor described above. When used for driving, malfunction can be prevented. Further, it is possible to use the apparatus as an abnormality detection device for detecting an abnormality in position detection without adding a new means for detecting a circuit abnormality. Since the position θ can be obtained without providing a calculation process for calculating the position variation error, the position detection and the abnormality detection can be performed at low cost.

Embodiment 2 FIG.
FIG. 3 is a block diagram showing a configuration of the position detection device according to the present embodiment. In the drawing, reference numeral 30 denotes a brushless motor having the number of pairs of N poles, which is directly connected to the position sensor 10, and the position sensor 10 detects a motor rotation position. Reference numeral 25 denotes a counter that counts a time difference d between the zero cross point of the signal output from the addition circuit 15 and the zero cross point of the signal output from the subtraction circuit 16. Reference numeral 26 denotes a latch circuit which receives a zero-cross detection pulse detected by each zero-cross detection circuit 18, that is, a zero-phase detection pulse as a latch pulse, and latches the count value of the counter 25 at the timing of the latch pulse. Note that other configurations are the same as those in the above-described first embodiment, and thus are denoted by the same reference numerals, and description thereof is omitted here.

  When driving a brushless motor having N pole pairs, it is customary to use a position sensor having an N-axis double angle with one rotation of the motor as N cycles. This is because, for the motor drive itself, when focusing on only one pole, the rotational position detected by the position sensor corresponds to the electric angle of the motor, and the detected position can be directly applied to motor control. However, according to the detection method of the present invention, as can be seen from the above embodiment, the phase difference between the output sin (ωt ± β + θ) from the adding circuit 15 and the output sin (ωt ± β−θ) of the subtracting circuit 16 is 2θ. It becomes. Here, if the electric angle of the motor is set to 2θ, if the phase difference between the output signal of the adding circuit 15 and the output signal of the subtracting circuit 16, that is, the zero-crossing time difference is measured, the motor control can be directly applied. It can be replaced by an electrical angle. Therefore, it is not necessary to calculate the phase fluctuation error once and then calculate the detection position as in the conventional example. As shown in FIG. 3, the zero cross point of the signal output from the addition circuit 15 and the subtraction circuit 16 are calculated. The time difference d at which the zero-crossing point of the signal output from is generated is counted. Since the output signals of the addition circuit 15 and the subtraction circuit 16 are repeated at a predetermined period of 2π / ω, d × ω is the electrical angle. For example, the detection position when the motor is a 4-pole pair and the position sensor is a 2-axis double angle is as shown in FIG. At this time, as in the above-described embodiment, the detection angle when one of the phase shift circuits has failed is also shown. As can be seen from the graph, even if the phase shift circuit fails, the error is small and the influence on the motor control is small.

  Here, although the predetermined period is 2π / ω, there is a possibility that ω may fluctuate due to the variation of the components of the oscillation circuit. Therefore, the period T at which the zero-cross point of the addition circuit 15 or the subtraction circuit 16 occurs is set to T. It may measure and adapt it to the time difference d, 2πd / T.

  It should be noted that the present invention can be applied to a motor having a pole-pair number of (multiple of 2) × M for a position sensor of M-axis double angle. For example, for a motor having 6 pole pairs, a three-axis double angle sensor may be used as described above, but a one-axis double angle sensor may be used. In this case, if the present embodiment is applied to the sensor position θ, 2θ can be detected, and this is calculated by ３. By setting 2θ / 3, the electrical angle can be calculated.

  As described above, in the position detection device according to the present embodiment, if the electric angle of the motor is set to 2θ, the phase difference between the output signal of the addition circuit 15 and the output signal of the subtraction circuit 16, that is, Since the time difference at zero crossing can be measured and replaced with the electrical angle used for motor control as it is, even if the phase shift circuit fails, the effect of the failure can be minimized. In the case where the motor is used for driving the motor as shown, malfunction can be prevented.

Embodiment 3 FIG.
FIG. 5 is a block diagram showing a configuration of the position detection device according to the present embodiment. In the figure, reference numeral 31 denotes a position calculation circuit which receives the data D1 latched in the latch circuit 19 and calculates a position θp by calculating “−D1−δ (= θp)”. Reference numeral 32 denotes a position calculation circuit which receives the data D2 latched in the latch circuit 20 and obtains the position θm by calculating “D2 + δ (= θm)”. Reference numeral 33 denotes a comparison processing circuit which calculates an average value of θp and θm and outputs the calculated value as θ in consideration of a shift in position detection θp and θm due to noise received on the detection circuit. When θp and θm greatly differ from each other, that is, when the difference between θp and θm is equal to or greater than a predetermined threshold, the comparison processing circuit 33 determines that there is an abnormality. Note that other configurations are the same as those in the above-described first embodiment, and thus are denoted by the same reference numerals, and description thereof is omitted here.

  If the output winding of the position sensor and the path from the position sensor to the position detecting device are long, they appear as phase fluctuation errors in the output due to the influence of temperature and the like. The factor becomes small, and the amount of phase fluctuation becomes sufficiently small. In this case, there is no problem even if the phase fixing error δ is considered. In such a case, as shown in FIG. 5, the excitation signal sinωt output from the oscillation circuit and the composite signal sin (ωt + θ + δ) output from the addition circuit 15 shown in the present invention pass through the zero-cross detection circuit 17, When the data is latched by the latch circuit 19, a phase difference of -θ-δ is detected from the latched data D1. When the combined signal sin (ωt−θ + δ) output from the subtraction circuit 16 passes through the zero-cross detection circuit 18 and is latched by the latch circuit 20, a phase difference of θ−δ is detected from the data D2. Here, when it is assumed that the phase error δ is a fixed value, the values are determined in advance when the apparatus is constructed. Therefore, processes 31 and 32 for subtracting the fixed phase error δ from the detected data D1 and D2 are performed. Thus, the positions θp and θm can be detected. One of θp and θm may be used as the position θ. By doing so, the other detection circuit can be omitted and the configuration can be made inexpensively. Further, since the detections θp and θm may be slightly shifted due to noise received on the detection circuit, the accuracy can be improved by calculating the average value of the detections θp and θm by the comparison processing circuit 33 to obtain the position θ. . If θp and θm are significantly different, it is considered that an abnormality has occurred in the detection device, and an abnormality determination can be made. Further, when the motor is used for motor control or the like, it is possible to instruct to stop the control.

  In the present embodiment, when the amount of variation is small enough that the phase variation error is considered to be a fixed value, the sensitivity can be further increased outside the variation range of the phase variation error described in the first embodiment, and abnormality detection can be performed. It becomes even easier.

1 is a configuration diagram illustrating a position detection device according to a first embodiment of the present invention. FIG. 7 is an explanatory diagram showing a result of position detection according to Embodiment 1 of the present invention. FIG. 9 is a configuration diagram illustrating a position detection device according to a second embodiment of the present invention. FIG. 9 is an explanatory diagram illustrating a result of position detection according to the embodiment of the present invention. FIG. 9 is a configuration diagram illustrating a position detection device according to a third embodiment of the present invention. FIG. 14 is an explanatory diagram illustrating a phase fluctuation error according to the third embodiment of the present invention. FIG. 9 is a configuration diagram illustrating a conventional position detection method. FIG. 10 is an explanatory diagram showing a position detection result at the time of an abnormality by the conventional position detection method.

Explanation of reference numerals

  10 position sensor, 12 counter, 15 addition circuit, 16 subtraction circuit, 17 zero cross detection circuit, 18 zero cross detection circuit, 19 latch circuit, 20 latch circuit, 22 oscillation circuit, 23 phase shift circuit, 24 phase shift circuit, 25 counter, 26 latch circuit, 30 motor, 33 comparison processing circuit.

Claims (5)

An excitation signal having a predetermined periodic waveform is supplied, a first output winding outputs a first amplitude modulation signal induced according to a detection position, and a second output winding outputs a first amplitude modulation signal according to the detection position. A position sensor for outputting an induced second amplitude modulation signal;
Phase shifting means for electrically shifting the phase of one of the first amplitude modulation signal and the second amplitude modulation signal by a predetermined angle;
Conversion means for converting the other of the first amplitude modulation signal and the second amplitude modulation signal into a phase modulation signal by adding or subtracting the signal output from the phase shifting means;
Calculating means for determining the detection position by detecting the phase of the phase modulation signal output by the conversion means,
An abnormality determination unit that determines whether the position detection operation is abnormal by detecting the phase.   2. The abnormality detection device according to claim 1, wherein when the position detection error is out of a predetermined range, the position detection operation is determined to be abnormal.   2. The abnormality detection device according to claim 1, wherein when the position detection error changes suddenly, the position detection operation is determined to be abnormal.   The abnormality detection device according to claim 1, wherein the abnormality determination unit determines an abnormality in the position detection operation when the position detection has a predetermined value. The position sensor is directly connected to the motor to detect the motor rotation position,
Further comprising a drive circuit for driving the motor,
5. The abnormality detection device according to claim 1, wherein when the abnormality determination means determines that the position detection operation is abnormal, the control for driving the motor is interrupted and the motor driving is prohibited. apparatus.

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