JP2017037046A - Torque calibration device using electromagnetic force and torque calibration method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a calibration device which enables highly precise calibration to be executed even for minute torque in a manner that uses torque generated by electromagnetic force in place of a conventional actual load type torque calibration device.SOLUTION: A calibration device comprises: magnetic circuits with different electric poles arranged opposite to each other 8 and 9 which generate a magnetic field of magnetic flux density B; a coil 7 which is inserted into the magnetic circuits with different electric poles arranged opposite to each other; a motor 2 which rotates the coil 7 with a specific rotational angular velocity ω and immobilizes the same at a specific angular position; a rotary encoder which detects the angular position p and the rotational angular velocity ω of the coil 7; a voltage measurement section which measures induced electromotive force V generated in the coil 7 when the motor 2 is rotated at the rotational angular velocity ω; and a memory which stores the maximum value Vof the induced electromotive force V and the angular position pwhen the induced electromotive force V is maximized. A CPU 10 immobilizes the coil 7 at the angular position pagainst torque by applying electric current I to the coil 7 and inputs output torque of the motor 2 generated when the coil 7 is immobilized into a torque converter to be calibrated.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a calibration apparatus and a calibration method for calibrating a torque measuring instrument, and is used in fields where the torque must be controlled to a minute value and strictly, such as the precision instrument field, the measuring instrument field, and the medical instrument field. The present invention relates to a torque calibration device and a calibration method for calibrating a torque measuring device.

Conventionally, calibration (or testing) of a torque measuring device is generally performed by a gravity method by comparing with torque generated by applying gravity to the tip of a lever.
Gravity method is an effective method that can realize the most advanced torque at present, including National Institute of Advanced Industrial Science and Technology (NMIJ), National Metrology Institute (NMI) such as Germany, France, China and Korea. It is adopted as a method to realize the national standard of torque.

Japanese Patent Application Laid-Open No. 2004-228561 describes that torque calibration is interrupted when a long-period fluctuation occurs when torque calibration is performed using the torque generated by adding a weight to the tip of the lever. Yes.
Non-Patent Document 1 describes an actual load type torque standard developed by German NMI that enables calibration of minute torque of 1 mN · m to 10 mN · m, which is currently the most accurate. It is regarded as a high torque standard.

JP 2001-133351 A

IPO science "Metrological characterization of a 1 N m torque standard machine at PTB, Germany" (Posted on May 20, 2014 by D. Roske)

For example, when manufacturing precision equipment and micro equipment, and also when implanting an implant, the prescribed tightening torque value is extremely small, and it is required to strictly maintain and manage it.
However, with this gravity method, there is a limit in manufacturing accuracy in reducing the weight of the loaded weight or shortening the length of the lever, and further, the influence of the frictional force acting on the fulcrum of each lever. And the influence of gravitational acceleration based on differences in air flow and latitude. Non-Patent Document 1 describes that calibration of torque values of 1 mN · m to 10 mN · m can be realized with an uncertainty of 0.1% using the actual load formula, but the uncertainty is sufficient as a torque standard. However, it is very difficult to accurately calibrate a small torque of less than 1 mN · m with the actual load type.

On the other hand, in the torque SI traceability system currently proposed in Japan, the torque standard machine of gravity method (actual load type torque standard machine) possessed by NMIJ and the torque adopted by the calibration operators at the first level Although it is necessary to make a comparison between calibration devices, because of the principle of each device's structure, weight, and torque generation, slight vibrations affect accuracy, so the torque calibration device can be easily transported and relocated. I can't.
For this reason, an intermediary device (torque measurement device) must be used, and the result is inevitably influenced greatly by the performance of the used intermediary device. There is a need for a calibration method.

  Therefore, in order to overcome these problems, the object of the present invention is to perform highly accurate calibration (or test) even for minute torque by using torque generated by electromagnetic force instead of the conventional actual load type. It is also possible to make the torque calibration device main body compact and facilitate transportation and installation so that calibration (or testing) at the national standard level of torque can be performed at the manufacturing site.

In order to solve the above problems, a torque calibrating device according to the present invention includes a different pole facing magnetic circuit that forms a magnetic field having a magnetic flux density B, a coil installed in the opposite pole facing magnetic circuit, and a rotational angular velocity of the coil. A motor that rotates at ω and stops at a specific angular position, a rotary encoder that detects the rotational angle position p and the rotational angular velocity ω of the coil, and induction that occurs in the coil when the coil is rotated at the rotational angular velocity ω. A voltmeter for measuring the electric power V, a memory for recording the maximum value V _max of the induced electromotive force V and the angular position p ₀ at that time, and a torque transducer to be calibrated are connected to the coil to pass the current I. And a control device that stops the motor at the angular position p ₀ against the torque generated at the time, and the output torque of the motor at that time is input to the torque converter to be calibrated.

According to the present invention, the following effects can be achieved as compared with a conventional actual load type calibration apparatus.
(1) A minute torque can be reproduced with high accuracy.
(2) Weight reduction, compactness, and cost reduction are possible.
(3) Evaluation of gravitational acceleration according to latitude is unnecessary.
(4) It is difficult to receive mechanical damage due to conveyance, and even if it is received, re-evaluation (magnetic flux density of the magnetic circuit and coil shape) after conveyance is easy.
(5) For this reason, the primary standard of torque can be easily realized even at the manufacturing site.
(6) By building a new torque SI traceability system, development of new torque measuring devices can be promoted.

FIG. 1 is a perspective view showing the force that the coil C receives from the magnetic field when the current I is passed through the coil C in the magnetic field having the magnetic flux density B. FIG. FIG. 2 is a diagram in which the force that the coil C receives from the magnetic field when the current I is passed through the coil C in the magnetic field having the magnetic flux density B is viewed from the direction of the rotation axis. FIG. 3 is a perspective view showing an induced electromotive force generated when the coil C is rotated at a rotational angular velocity ω in a magnetic field having a magnetic flux density B. FIG. 4 is a view of the induced electromotive force generated after t seconds when the coil C is rotated at the rotational angular velocity ω in the magnetic field having the magnetic flux density B as viewed from the direction of the rotation axis. 5A and 5B show the overall configuration of an embodiment of the present invention, where FIG. 5A is a side view and FIG. 5B is a front view. FIG. 6 is an enlarged view around the current / voltage measuring device main body 6, the rectangular coil 7, and the yoke 8. FIG. 7 is a block diagram of the present embodiment. FIG. 8 is an overall configuration diagram when performing torque calibration according to the present embodiment.

First, the basic principle of the present invention will be described.
As shown in FIG. 1, a rectangular coil C (length L, height h, O-O) that can rotate around a horizontal axis (O-O ') in a vertically upward uniform magnetic field with a magnetic flux density B When a current I is applied with a shape symmetrical to '), the force F received from the magnetic field by two sides perpendicular to the magnetic flux density is
F = I · B · L or F = -I · B · L · · · · · · · · · · · (1)
It becomes. In other words, the forces acting on the two sides perpendicular to the magnetic flux density are equal in magnitude and opposite in direction, so that a couple is generated.

FIG. 2 shows a state where the rectangular coil C is inclined by θ (hereinafter referred to as “angular position”) with respect to the direction of the lines of magnetic force. At this time, the torque T acting on the coil C is expressed as follows:
T = I · B · L · h · cosθ = I · B · A · cosθ · · · · · · · · · · · (2)
It can be expressed as.
Here, when A = L · h, that is, A is the area of the coil and the coil C has N turns,
T = N ・ I ・ B ・ A ・ cosθ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Equation (3)
It becomes.
From Equation (3), the maximum value T _max of the torque T is cos θ = 1, that is, the surface of the coil C is parallel to the magnetic field lines. Occurs when θ = nπ (n = 0, 1, 2, 3, ...)
T _max = N ・ A ・ B ・ I ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Equation (4)
It becomes.

In order to realize torque with high accuracy, it is required to set or measure each parameter on the right side of Equation (4) with high accuracy.
Although the angular position θ and the current I can be measured with relatively high accuracy, it is extremely difficult to measure the shape (number of turns N and area A) of the coil C and the magnetic flux density B with high accuracy.
Therefore, in order to cancel out the magnetic flux density B, the area A of the coil C, and the number of turns N, the same coil C is rotated by the motor M at the rotational angular velocity ω in the magnetic field of the same magnetic flux density B as shown in FIG. The induced electromotive force V generated in step 1 is measured in advance.
That is, when the coil C is rotated at a constant rotational angular velocity ω (π / s) by the motor M in a magnetic field having the same magnetic flux density B as when torque is generated, an induced electromotive force V is generated in the coil C. .
When the origin (t = 0) is when the normal vector of the coil C coincides with the direction of the magnetic field line, as shown in FIG. 4, when the normal line of the coil C becomes an angle ωt with respect to the magnetic field line after t seconds, as shown in FIG. The induced electromotive force V is
V = N ・ A ・ B ・ ω ・ sinωt ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Equation (5)
It is represented by

Here, the maximum value (absolute value) V _max of the induced electromotive force V is sinωt = 1, and the surface of the coil C is parallel to the magnetic field lines, ωt = −n · π / 2 (n = 0, 1, 2, 3 ...)
V _max = N ・ A ・ B ・ ω ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Equation (6)
It becomes.
As described above, this is the same angular position as when the current I is passed through the coil C in the magnetic field of the magnetic flux density B and the generated torque becomes the maximum value T _max .
Therefore, in advance, to rotate at different rotational speeds omega _i by the motor M to the coil C in the magnetic flux density B, and each rotation speed, and the maximum induced electromotive force V _{Max_i,} the angular position p _{0 - i} of the coil C at that time Record.
Then, ω _i is taken on the horizontal axis and V _{max — i} is taken on the vertical axis, and N · A · B which is the inclination is obtained by an approximate expression.
Note that the average value of p _{0 — i} is p _{0 /} .

Next, a current I is passed through the coil C while the coil is held at the angular position p _{0 /} by the motor M.
At this time, according to Equation (4),
T _max / I ＝ N ・ A ・ B ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Equation (7)
And according to equation (6)
V _max / ω = N ・ A ・ B ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Equation (8)
Furthermore, according to equations (7) and (8),
T _max · ω = V _max · I ···································· Equation (9)
It becomes.

Equation (9) shows that the mechanical power and the electrical power are equal, and N, A, and B are all erased, and V _max (voltage value), I (current value), ω (rotational angular velocity) ), And the accuracy of T _max can be determined by the positioning accuracy of the coil C.
For example, for voltage and current values, a voltmeter with an accuracy of ± 0.01 V or less is adopted, and an ammeter with an accuracy of ± 0.001 A or less is adopted, and the rotational angular velocity and angular position have a resolution of 2 ²⁴ counts per revolution. If an optical non-contact rotary encoder with a resolution of 262144 counts / revolution is used, the relative expansion uncertainty can be reduced to less than 0.1% even for minute torques of less than 1 mN · m. It is. This accuracy indicates that the uncertainty of the current high-performance actual load type torque standard machine described in Non-Patent Document 1 can be realized.
In addition, about the coil C, since the bobbin reinforced with acrylic is used, the influence by a deformation | transformation etc. can be disregarded.
When the torque is determined by the actual load type, even the actual load type torque standard machine developed by the German NMI with the smallest uncertainty is on the order of 10 ^-5 relative value, but according to the present invention, Compared with the conventional actual load formula, the uncertainty can be reduced to 1/10.

Specifically, in the present invention, in advance, in a magnetic field having a magnetic flux density B, the motor M rotates the coil C in the rotational angular velocity omega _i, the maximum value V _{Max_i} the induced electromotive force generated with the angular position p at that time _Measure and record _{0_i} repeatedly.
By changing the rotation angular velocity ω _i in various _ways and repeating the above measurement and recording, the relationship between ω _{i and} V _{max — i} is obtained, and the inclination is calculated by the least square method or the like, as shown in the equation (6). The magnetic flux density B and the shape of the coil C (the number N of turns and the area A) can be evaluated. Further, at any rotational angular velocity, the angular position where V _max should not be strictly changed, and the measurement result of p _{0_i} is considered to be a normal distribution. Therefore, from the viewpoint of improving accuracy, the average value p _{0_i Let 0} / be the angular position where the induced electromotive force is maximum.

Next, in the magnetic field having the same magnetic flux density B, the motor M holds the angular position of the coil C at the average value p ₀ /, and the current I is caused to flow through the coil C.
T _max = I · V _max / ω
It becomes.
That is, T _max can be specified by measuring V _max / ω (apparatus specific constant) evaluated in advance and the current I, and by inputting this torque to the calibration target, Can be calibrated.

An embodiment of the present invention based on the above basic principle will be described below.
5A and 5B show the overall configuration of the present embodiment, where FIG. 5A is a side view and FIG. 5B is a front view.
A motor 2 is attached to the top of the linear guide 1 so that the vertical position can be adjusted by an L-shaped jig. The coupling 3, air bearing groups 4a to 4c, such as an optical non-contact rotary encoder, etc. A current / voltage measuring device main body 6 is connected via a high-resolution rotary encoder 5. The air bearing groups 4a to 4c are also attached by an L-shaped jig so that the vertical position can be adjusted.
FIG. 5 shows a state in which the output shaft of the motor 2, the coupling 3, and the rotary encoder 5 are separated from each other. During operation, the motor 2 and the air bearing groups 4a to 4c are also L-shaped jig linear guides. They are joined together by adjusting their position on one.

In this embodiment, the current / voltage measuring device main body 6 is a substantially rectangular parallelepiped or a cube, and a shaft extending from the lower surface side of the rotary encoder 5 is connected to the center point of the upper surface thereof so as to penetrate the inside. A rectangular coil 7 is detachably attached to the lower part of the current / voltage measuring device body 6 through connection terminals T1 and T2.
On the other hand, a U-shaped yoke 8 is fixed to the lowermost part of the linear guide 1, and the opposite pole type magnetism is provided by the N pole and S pole of the magnet 9 attached to the inner surface of the yoke 9 so as to face each other. A circuit is formed, and a rectangular coil 7 is inserted therein. The magnet 9 may be a permanent magnet or an electromagnet.

A detection signal from the rotary encoder 5 is input to the control CPU 10 via the interface 11, and a current value and a voltage value measured by the current / voltage measuring device body 6 are input via the receiving unit 12. Yes.
Based on these detection values, the control CPU 10 drives the motor 2 via the drive circuit 13 to control the rotational speed and stop position of the rectangular coil 7.

As shown in FIG. 6, a battery 14 (two in this embodiment) for supplying current to the rectangular coil 7 is mounted on one surface of the inner wall surface of the current / voltage measuring device body 6; On the other inner wall surfaces, a control CPU 10, a wireless communication module 15 that transmits to the receiving unit 12, and a current / voltage measuring unit 16 are mounted.
Instead of incorporating the battery 14 in the current / voltage measuring device body 6, external power may be supplied through a rotary connector. In any case, it is preferable to balance the weight distribution of the built-in equipment so that a large eccentric motion does not occur with the rotation of the current / voltage measuring device body 6.

FIG. 7 shows an overall block diagram of this embodiment. The negative side of the battery 14 connected in series is connected to the terminal T1, the positive side is connected to the terminal T2 via the switch S, and the current control unit 17 of the current / voltage measuring unit 16. Each is connected, and a current is supplied to the coil 7 by turning on the switch S. Further, the voltage measurement unit 18 of the current voltage measurement unit 16 measures the voltage between the terminals T1 and T2.
The current value I supplied to the rectangular coil 7 by the current control unit 17 and the measured value V of the voltage measuring unit 18 are transmitted to the receiving unit 12 by the wireless communication module 15.

When measuring the maximum value V _max of the induced electromotive force V, the control CPU 10 drives the drive circuit based on the detection signal from the rotary encoder 5 input via the interface 11 with the switch S turned off. The rotational speed of the motor 2 is controlled via 13.
On the other hand, when the torque converter is calibrated, the switch S is turned on, and the current value I supplied to the rectangular coil 7 is controlled via the current control unit 17 and input via the interface 11. Based on the detection signal from the non-contact rotary encoder 5, the stationary position control by the motor 2 is performed via the drive circuit 13.

The motor 2 is a motor (servo motor or stepping motor) capable of high-precision speed control and positioning, receives a command from the control CPU 10, has a positioning accuracy of 2 ²⁴ counts per revolution, and has a stable speed. Can be maintained. In addition, a voltmeter for measuring the induced electromotive force provided in the current / voltage measuring device main body 6 and an ammeter for measuring the current flowing through the rectangular coil 7 also use those having an accuracy of ± 0.01 V or less and ± 0.001 A. Even if the resolution of the part is taken into account, the induced electromotive force of the rectangular coil 7 and the current flowing through the coil 7 are input to the control CPU 11 with an accuracy of ± 0.01 V or less and ± 0.001 A.

  As shown in FIG. 5, the air bearing groups 4 a to 4 c provided between the coupling 3 and the non-contact rotary encoder 5 include air bearings 4 a that support in the thrust direction on the upper surface (coupling 3 side), It is composed of a total of three air bearings, that is, air bearings 4b and 4c that support the radial direction on both side surfaces. The air bearing 4a supports the weights of the non-contact rotary encoder 5, the current / voltage measuring device main body 6 and the rectangular coil 7 attached below, and when the torque converter 22 is attached, the air bearing 4a is positioned below the torque converter 22. The weight of the device is prevented from acting on the torque transducer 22.

On the other hand, the air bearings 4b and 4c are mounted in directions in which the flows of compressed air supplied to each other face each other, and maintain the rotation center of the entire apparatus in the vertical direction at all times, thereby improving the rotation accuracy.
Compressed air from the air manifold 21 is introduced into these air bearing groups 4a to 4c via valves 19a to 19c and speed controllers 20a to 20c. In order to hold the rectangular coil 7 at a precisely determined angular position, the flow rate can be adjusted automatically or manually by the speed controllers 20a to 20c so that the rotational force due to the compressed air can be canceled out and the stationary state can be maintained. I have to.

Hereinafter, a procedure for performing torque calibration according to the present embodiment will be described.
First, in order to evaluate the magnetic flux density B and the shape (number of turns N, area A) of the rectangular coil C, the drive circuit 13 receives a command from the control CPU 10 and is formed by the motor 2 with the yoke 8 and the magnet 9. The rectangular coil 7 is rotated in a magnetic field having a magnetic flux density B, the induced electromotive force V is generated by the voltage measuring unit 18 in the current / voltage measuring device body 6, and the rotational angular velocity ω and the angular position p of the rectangular coil C are set to the rotary. Obtained by the encoder 5 and recorded in the memory of the control CPU 10.
This is repeated, and the maximum value V _max of the induced electromotive force V and the angular position p ₀ where the maximum value V _max occurs are recorded.

The rotational angular velocity omega _i is sequentially changed, by repeating, seeking _{V Max_i} and _{p 0 - i} for each rotational angular velocity omega _i, rotating the horizontal axis angular velocity omega, the vertical axis _{V max,} the slope (= N · A · B ) Is obtained by the least square method or the like, and the magnetic flux density B and the shape of the rectangular coil C are evaluated.
_Further, an average value p _{0 /} of the angular position p _{0 — i} is also obtained.
If the above operation is performed once for each combination of the magnetic circuit and the rectangular coil and recorded in the memory, it is necessary to perform it every time the torque converter is calibrated unless there is a change in the magnetic flux density or the shape of the rectangular coil. Absent. However, if it is once disassembled for conveyance or if the measurement environment conditions are poor and a change with time is expected, it is necessary to re-evaluate the magnetic flux density B and the shape of the coil C.

Next, a procedure for calibrating a torque transducer to be torque calibrated will be described.
First, as shown in FIG. 8, by adjusting the position on the linear guide 1, a torque converter 22 to be calibrated is interposed below the coupling 3, and the torque converter 22 and the air bearing groups 4 a to 4 are arranged. 4c is connected by the second coupling 23. The torque converter 22 is connected to the control CPU 10 via a torque converter indicating instrument 24.

In response to the command from the control CPU 10, the motor 2 is set so that the rectangular coil 7 becomes the average value _{p0 /} of the angular position _{p0_i} obtained in advance by the procedure of evaluating the magnetic flux density B and the shape of the coil C as described above. When the current I is supplied from the battery 14 to the rectangular coil 7 in a state where it is stopped at that position, the magnetic field formed by the opposite-polarity facing magnetic circuit formed by the yoke 8 and the magnet 9 is expressed by the following equation (4). The torque T shown is generated.
Although the rectangular coil 7 is about to rotate by this torque T, the control CPU 10 determines the angular position input from the rotary encoder 5 in advance by the procedure for evaluating the magnetic flux density B and the shape of the coil C as described above. A command is issued to the motor 2 to hold it at the obtained angular position p _{0 /} .
At this time, control is performed so that the speed of the motor 2 can be reduced step by step so that the angular position of the rectangular coil 7 does not overshoot from p0 _/ .

When the angular position of the rectangular coil 7 can be held at p _{0 /} by the motor 2 via the torque converter 22 (there is a change), the torque converter 22 is screwed by the torque T _max generated in the rectangular coil 7. Will be. Therefore, the current I flowing through the rectangular coil 7 is measured, and T _max is obtained from the equation (10) from the relationship between the magnetic flux density B and the shape of the rectangular coil 7 obtained from the relationship between V _max and ω described above. The torque measuring device can be calibrated based on the correspondence between the calculated T _max and the output value S of the torque converter 22.

In the above embodiment, the motor 2, the coupling 3, the air bearing groups 4 a to 4 c, the high-resolution optical non-contact rotary encoder 5, and the current / voltage measuring device main body 6 are arranged along the linear guide 1 in the vertical direction. However, these may be arranged along the linear guide 1 in the horizontal direction.
In addition, although the two batteries 14 are housed in the current / voltage measuring device body 6, one or three or more batteries may be used, and external power may be supplied using a rotor connector.
The current / voltage measuring device body 6 may be a cylindrical body, and the shape of the coil is not limited to a rectangle.

As described above, according to the present invention, it is possible to accurately reproduce even a small torque by flowing a current through a coil in a magnetic field regardless of the shape of the coil and the magnetic field density generated by the opposite-polarity opposed magnetic circuit. The torque calibration device can be reduced in weight, size and cost.
In addition, since it is not greatly affected by vibrations and shocks, the primary standard of torque can be easily realized even at the manufacturing site and the like, so that it can be expected to be widely adopted as a torque calibration device.

1: Linear guide 2: Motor 3: (First) coupling 4a to 4c: Air bearing group 5: Rotary encoder 6: Current voltage measuring device body 7: Rectangular coil 8: Yoke 9: Magnet 10: CPU for control
DESCRIPTION OF SYMBOLS 11: Interface 12: Reception part 13: Drive circuit 14: Battery 15: Wireless communication module 16: Current voltage measurement part 17: Current control part 18: Voltage measurement part 19a-19c: Valve 20a-20c: Speed controller 21: Air manifold 22: Torque transducer 23: (second) coupling 24: Torque transducer indicating instrument

Claims (5)

An opposite-polarity-type magnetic circuit that forms a magnetic field having a magnetic flux density B;
A coil inserted into the opposite-polarity opposed magnetic circuit;
A motor that rotates the coil at a rotational angular velocity ω and stops at a specific angular position;
A rotary encoder that detects a rotational angle position p and a rotational angular velocity ω of the coil;
A voltage measuring unit that measures an induced electromotive force V generated in the coil when the motor is rotated at a rotational angular velocity ω;
A memory recording the maximum value V _max of the induced electromotive force V and the angular position p ₀ at that time;
A control device for causing a current I to flow through the coil and causing the coil to stand still at the angular position p ₀ against a torque generated in the coil;
A torque calibration apparatus, wherein the output torque of the motor is input to a torque converter to be calibrated.   A voltage measuring unit that is mounted with the coil and includes a current / voltage measuring device main body connected to the motor via the rotary encoder, and that measures the induced electromotive force inside the current / voltage measuring device main body, A current control unit that supplies current I to the coil, the control device, and a wireless communication module that wirelessly transmits voltage data measured by the voltage measurement unit and current data supplied by the current control unit. The torque calibration device according to claim 1, wherein   The torque calibrating device according to claim 1 or 2, wherein the motor and the rotary encoder are connected by an air bearing group that supports thrust and radial directions.   The motor and the air bearing group are attached by a linear guide so that the position of the motor and the air bearing group can be adjusted. The torque calibration device according to claim 3, wherein the torque calibration device is input to a converter. A coil is rotated at a rotational angular velocity ω inside a different pole facing magnetic circuit that drives a motor and forms a magnetic field having a magnetic flux density B, and a maximum value V _max of the induced electromotive force V generated in the coil, and the induced electromotive force A first step of recording in the memory the angular position p ₀ where V is the maximum value V _max ;
A second step of connecting a torque measuring device to be calibrated between the motor and the coil;
A third step of passing the current I through the coil and causing the motor to stand still at the angular position p ₀ against the torque generated in the coil;
The output torque of the motor is input to a torque converter provided in the torque measuring device, and the fourth step of calibrating the torque measuring device according to the instruction value to the torque converter. Torque calibration method characterized by

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