JPH1114474A - Method and device for detecting transfer torque in wave motion decelerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect torque with a wave motion decelerator without being affected by elastic deformation of flake spline due to a wave generator. SOLUTION: A torque sensor 20 which detects a transfer torque transferred through a wave motion decelerator, an encoder 51 for detecting the rotational angle position of a wave generator, and a ROM 43 where a torque correction data is measured and stored are provided, and the torque detected with the torque sensor 20 is corrected based on the torque correction data stored in the ROM 43, for obtaining a transfer torque. As the torque correction data, a no-load detected torque which is detected by the torque sensor under no load is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for detecting a torque transmitted from a wave reducer used as a reducer of a robot, for example.

[0002]

2. Description of the Related Art In recent years, robots have been widely used, but in controlling such robots, it is very useful to measure the torque of a joint or the like and use the measured torque for controlling the robot. is there. Further, if failure diagnosis is performed using the measured torque, safety can be improved.

[0003] In view of the above, various devices for detecting a transmission torque in a wave reducer used for driving a robot have been conventionally proposed. As an example, there is a wave reducer disclosed in Japanese Patent Application Laid-Open No. 7-103291, in which a coil is disposed around a flex spline that constitutes a wave reducer, and a torque acting on the flex spline is transmitted to the flex spline. Is detected from a change in impedance based on a change in the magnetic characteristics of the device.

[0004]

Devices for detecting the torque transmitted through the wave reducer based on the elastic deformation of the flexspline due to the torque have been conventionally known. However, since flex splines are transformed by wave generators,
The flex spline has a problem that elastic deformation by the wave generator occurs in addition to elastic deformation by the transmission torque, and the elastic deformation by the wave generator may reduce the detection accuracy of the transmission torque. This problem can be solved by arranging the sensors as described in Japanese Patent Application No. Hei 8-47724 filed earlier by the present applicant. However, there is a problem that the detection error due to the imbalance in the manufacturing of the flex spline cannot be corrected. is there.

In view of such a problem, the present invention provides a transmission torque detecting device and method capable of accurately detecting a transmission torque in a wave speed reducer without being affected by elastic deformation of a flex spline by a wave generator. The purpose is to:

[0006]

In order to achieve the above object, in a transmission torque detecting device according to the present invention, a torque sensor for detecting a transmission torque transmitted via a wave speed reducer, and a rotation of a wave generator. A rotation angle sensor for detecting the angular position, and correction data storage means for measuring and storing torque correction data corresponding to the rotation angle position of the wave generator, wherein the detected torque detected by the torque sensor is stored in the correction data storage means. The transmission torque is obtained by performing correction based on the stored torque correction data.
It should be noted that the no-load detection torque detected by the torque sensor at the time of no load can be used as the torque correction data. In this case, the transmission torque is obtained by subtracting the no-load torque from the detection torque detected by the torque sensor. .

The elastic deformation of the flexspline generated by the wave generator is constant in accordance with the rotation angle of the wave generator, and therefore, the torque correction data corresponding to the rotation angle position of the wave generator is independent of the transmission torque. It is constant. For this reason, the torque detected based only on the elastic deformation of the flexspline by the wave generator in accordance with the rotation angle of the wave generator is stored as torque correction data in correspondence with the rotation angle of the wave generator, and By subtracting this torque correction data from the detected torque, it is possible to obtain an accurate transmission torque in which the influence of the elastic deformation of the flexspline by the wave generator is removed.

However, the torque correction data fluctuates according to the temperature of the wave reducer. This is because, for example, at low temperatures, the viscosity of the lubricating oil increases and the driving resistance increases. For this reason, it is preferable to measure and set the torque correction data for each temperature of the wave speed reducer, and to calculate the transmission torque using the torque correction data corresponding to the actual temperature of the wave speed reducer.

Further, according to the transmission torque detecting method of the present invention, first, the transmission torque of the wave reducer in the no-load state is detected in accordance with the rotational angle position of the wave generator. Is stored as torque correction data, the transmission torque of the wave reducer in the torque transmission state is detected in accordance with the rotational angle position of the wave generator, and the rotation of the wave generator is determined from the detected torque thus detected. The transmission torque is obtained by matching the angle phase and reducing the torque correction data. Here, since the transmission torque detected in the no-load state is generated only by the elastic deformation of the flexspline by the wave generator, this is used as it is as the torque correction data, and the no-load detection torque is calculated from the actual detection torque. By withdrawing, the influence of the elastic deformation of the flexspline by the wave generator can be removed, and accurate transmission torque detection can be performed.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A transmission torque detecting device and method according to the present invention will be described below with reference to the drawings. FIG. 1 shows an example of a wave reducer according to the present invention. In this reduction gear, the following members are mounted in bearings 8a and 8b in a space surrounded by a substantially cylindrical support case 1 on which an internal tooth circular spline 1a is formed and a flange cover 2 connected to the support case 1. To be rotatably supported. The support case 1 and the flange cover 2 are usually fixedly held.

The wave reducer reduces the rotation of the input shaft 3 to a very large reduction ratio (a very large reduction ratio of several tens to several hundreds).
The speed reducer transmits the output to the output shaft 13 after being decelerated. Since the speed reducer itself is conventionally known, the description of the speed reducer itself will be made simply.

The input shaft 3 is rotatably supported by the flange cover 2 via a bearing 8a. One end protrudes outward and the other end is connected to the elliptical cam 5. A plurality of pressing balls 6a are arranged at equal intervals along the outer periphery of the elliptical cam 5 to form a wave generator 6. On the other hand, the output shaft 13 is rotatably supported by the support case 1 via a bearing 8b, and has one end protruding outward from a side surface of the support case 1 and the other end disposed in the support case 2. It is connected to the member 10.

The flex spline member 10 is a member formed of an elastic material, and has an external tooth flex spline 1 at its tip.
1 and a thin cylindrical coupling portion 12 having a disc-shaped bottom wall 12a for connecting the external tooth flexspline 11 and the output shaft 13. The wave generator 6 is located along the inner peripheral surface of the external tooth flexspline 11, and the external tooth flexspline 11 is located at a position where it meshes with the internal tooth circular spline 1a.

In the wave generator 6, the elliptical cam 5 pushes up the ball 6a in the outer peripheral direction corresponding to the elliptical shape, and the flexspline 11 is elastically deformed into an elliptical shape. At this time, the portion of the flexspline 11 corresponding to the major axis of the ellipse is deformed so as to be pushed to the outermost side, and the flexspline 11 meshes with the internal toothed circular spline 1a at two places separated by 180 degrees.

In the above-structured wave reducer, when the input shaft 3 is rotationally driven, the wave generator 6 (elliptical cam 5) connected thereto is rotated together, and the flex spline 11 and the internal tooth circular spline 1a are rotated. Is rotated with this rotation. Here, the number of teeth of the flex spline 11 is formed one to several less than the number of teeth of the internal tooth circular spline 1a, and when the meshing position is rotationally moved according to the rotation of the input shaft 3 as described above, When the input shaft 3 makes one rotation, the flexspline member 10 rotates by the number of the different teeth. That is, for one rotation of the input shaft 3, the output shaft 13 is rotated by only one or several teeth of the flexspline 11, and the rotation is transmitted at a very large reduction ratio.

A torque sensor 20 for detecting a torque transmitted through the flexspline member 10 is attached to an outer surface of the disc-shaped bottom wall 12a of the flexspline member 10 in the wave reduction gear. . A protective cover 15 is mounted on the torque sensor 20. FIG. 2 shows the flexspline member 10 with the protective cover 15 removed.

As shown in FIG. 3, the torque sensor 20 of this embodiment is formed in the shape of a donut disk having an opening in the center, and excites an exciting coil constituting the torque sensor 20 and induces a detection coil. A processing circuit 30 for detecting electric power is connected to the torque sensor 20.

FIG. 4 shows a state where the torque sensor 20 is attached to the flex spline member 10. The torque sensor 20 has a first magnetic layer 22 formed from an amorphous sheet or an amorphous alloy sheet,
The first magnetic layer 22 is firmly adhered to the outer surface of the disc-shaped bottom wall 12a of the flexspline member 10 by a carbon cloth sheet 21 impregnated with an adhesive. An excitation coil pattern 23 is formed on the first magnetic layer 22.
a, a printed wiring board 23 for excitation on which a and 23b are formed;
The detection printed wiring board 24 on which the detection coil patterns 24a and 24b are formed is disposed in an overlapping manner, and second magnetic layers 25a and 25b made of an amorphous sheet or an amorphous alloy sheet are disposed thereon. .

As shown in FIG. 5, the first magnetic layer 22
A plurality of slits 22a, 2 are formed by forming a sheet made of an amorphous or amorphous alloy into a disk shape having a circular opening 22c at the center.
2b are formed in a ring shape in two rows. As shown, the inner peripheral side slit 22a and the outer peripheral side slit 2
2b are inclined at 45 degrees with respect to the circumferential direction, the inner circumferential slit 22a is tilted at 45 degrees to the left with respect to the circumferential direction, and the outer circumferential slit 22b is tilted at 45 degrees with respect to the circumferential direction. It is formed at an angle. Note that the inner peripheral slit 22a may be inclined 45 degrees to the right and the outer peripheral slit 22b may be inclined 45 degrees to the left.

As shown in FIG. 6, the exciting printed wiring board 23 is formed on a surface of a flexible printed circuit board 23e made of an insulating material by a first exciting coil pattern 23a located on the inner peripheral side and formed clockwise. , And a second exciting coil pattern 23b formed on the outer peripheral side and formed in a counterclockwise direction. In the drawing, each of the coil patterns 23a and 23b is formed so as to make approximately two turns, but a coil pattern having a larger number of turns may be formed.

Incidentally, in FIG.
Although a and 22b are schematically shown in a circular cross section, they are actually conductive material patterns formed on a printed circuit board. In FIG. 6, the solid line coil pattern is formed on the front surface of the flexible printed circuit board 23e, and the broken line coil pattern is formed on the back surface. Note that both coil patterns may be formed in multiple layers on the front surface or the back surface with an insulating layer interposed therebetween.

The outer peripheral end of the first exciting coil pattern 23a is connected to the inner peripheral end of the second exciting coil pattern 23b, and the inner peripheral end of the first exciting coil pattern 23a is
The outer peripheral ends of the exciting coil pattern 23b are connected to the exciting connector 23c, respectively.
The coil patterns other than 3c are coated with insulation. The exciting connector portion 23c is exposed, and if a current flows between these connector portions 23c, magnetic fields indicated by arrows P and Q in FIG. 4 are generated by the current flowing through the first and second exciting coil patterns 23a and 23b. I do. At this time, since the winding directions of the two coil patterns 23a and 23b are opposite, the two magnetic fields P and Q are also magnetic fields in opposite directions.

As shown in FIG. 7, the detection printed wiring board 24 is formed on a surface of an insulating material flexible printed circuit board 24e with a first detection coil pattern 24a formed on the inner peripheral side and formed clockwise. , A second detection coil pattern 24b formed on the outer peripheral side and formed in a counterclockwise direction
And are formed. Also in this detection printed wiring board 24, the number of turns of each of the coil patterns 24a and 24b may be larger, and a solid line coil pattern is formed on the front surface of the flexible printed circuit board 23e, and a broken line coil pattern is formed on the back surface. You. The first detection coil pattern 24a is connected to the first detection connector 23c.
And the second detection coil pattern 24b is connected to the second detection connector portion 23d.

In a state where the printed wiring boards 23 and 24 are overlapped on the first magnetic layer 22, the first excitation coil pattern 23a and the first detection pattern 24a both overlap the inner circumferential slit 22a. , The second excitation coil pattern 23b and the second detection pattern 24b both overlap the outer peripheral side slit 22b.

The second magnetic layer 2 located on the inner peripheral side
5a is formed in a ring shape that covers the first excitation coil pattern 23a and the first detection pattern 24a, and is mounted on and superimposed on them. Similarly, the second outer peripheral side
The magnetic layer 25b is formed in a ring shape that covers the second excitation coil pattern 23b and the second detection pattern 24b, and is mounted on the ring. These second magnetic layers 25a and 25b function as magnetic attraction when current flows between the exciting connector portions 23c to generate the magnetic fields P and Q shown in FIG. 4, and serve as the first and second exciting coil patterns. Magnetic fields P and Q are clearly generated around 23a and 23b.

Since the first magnetic layer 22 is adhered to the outer surface of the disc-shaped bottom wall 12a of the flexspline member 10, when the torque is transmitted through the flexspline member 10, the flexspline member 10 is When the first magnetic layer 22 is elastically deformed by receiving the torque, the first magnetic layer 22 is also deformed, and the deformation changes the magnetostriction characteristics of the first magnetic layer 22 and the magnetic permeability. When the magnetic permeability changes in this way, the strengths of the magnetic fields P and Q change, so that the first and second magnetic fields P and Q change.
If a change in the induced electromotive force generated in the detection coil patterns 24a, 24b is taken out from the first and second connector portions 24c, 24d and detected, a change in the magnetic permeability can be detected.

Since the change in the magnetic permeability detected in this manner is proportional to the elastic deformation of the flexspline member 10, the torque transmitted through the flexspline member 10 is calculated based on the change in the magnetic permeability. be able to. Since the flexspline member 10 is elastically deformed into an elliptical shape by the wave generator 6, the magnetostriction characteristics of the first magnetic layer 22 are also affected by the elastic deformation. For this reason, a process for correcting this effect is performed to perform accurate transmission torque detection. This configuration will be described later.

As described above, the torque sensor of the present invention has the first
The torque is detected by detecting a change in the magnetic permeability of the magnetic layer 22. The first magnetic layer 22 is inclined by 45 degrees with respect to the direction in which the change in the magnetic permeability is maximum, that is, the circumferential direction. The slits 22a and 22b are formed in the directions. As shown in FIG. 5, when the torque T acts on the flexspline member 10, a compression force acts in the direction of the slit 22 a as shown by an arrow A in a portion where the inner peripheral slit 22 a is formed, and the outer peripheral side A pulling force acts on the portion where the slit 22a is formed in the direction of the slit 22b as shown by the arrow B. At this time, a change in the magnetic permeability of the first magnetic layer 22 can be amplified by obtaining the shape anisotropy effect by the slits 22a and 22b, and the torque detection accuracy is further improved.

The apparatus for detecting a change in magnetic permeability as described above, that is, the processing circuit 30 shown in FIG.
This will be described with reference to FIG. The circuit 30 has an AC power supply 31. An AC current from the AC power supply 31 is supplied to the first and second excitation coil patterns 23a and 23b via the excitation connector 23c to excite them. . As a result, the magnetic fields P and Q in opposite directions corresponding to this current are applied to these coil patterns 2 as shown in FIG.
It occurs around 3a and 23b.

The magnetic fields P and Q generate mutual induction electromotive force in the first and second detection coil patterns 24a and 24b, and the mutual induction electromotive force generates the first and second connector sections 2a and 2b.
It is taken out to the bridge circuits 32a and 32b via 4c and 24d. Here, since the directions of the magnetic fields P and Q are opposite, one of the induced electromotive forces has a positive value and the other has a negative value.
This is extracted from the detection terminal 33 via the bridge circuits 32a and 32b as a voltage corresponding to the difference between the two.

In summary, when the rotation of the input shaft 3 of the wave speed reducer is reduced and transmitted to the output shaft 13, torque is transmitted via the flexspline member 10, so that the magnitude of the transmitted torque is reduced. In response, the flex spline member 10 is elastically deformed. Therefore, the first magnetic layer 22
, The strengths of the magnetic fields P and Q change, and the voltage detected at the detection terminal 33 also changes. The change in the magnetic permeability is calculated from this voltage change, and the flex spline member 1 is calculated.
The magnitude of the torque transmitted via the zero can be determined.

As described above, the torque sensor is incorporated in the wave reducer. Since the detection value of this torque sensor also detects the elastic deformation of the flex spline by the wave generator as described above, the torque sensor is corrected. Thus, a torque sensor system (transmitted torque detection device) that performs accurate transmission torque detection is configured. This torque sensor system will be described below.

FIG. 9 shows the configuration of this torque sensor system. This system comprises a wave reducer HD having the torque sensor 20 configured as described above and a signal processing circuit 30 for processing signals from the torque sensor. The input shaft 3 of the speed reducer HD is rotationally driven by the electric motor 60. The system further includes an encoder 51 for detecting the rotational angle position of the drive shaft of the motor 60, and a speed reducer H
A temperature sensor 52 for detecting the temperature of D, and a signal processing circuit 3
0 to the encoder 51
A torque correction calculator 40 for correcting based on the detection value of the temperature sensor 52; and a servo amplifier 50 for controlling the driving of the electric motor 60 based on the transmission torque obtained by the torque correction calculator (computer) 40.

The torque correction calculator 40 includes an A / D converter 41 for converting an analog signal output from the signal processing circuit 30 and an analog signal obtained by detection by the temperature sensor 52 into a digital signal, and an encoder. A counter 42 that counts the output of the torque correction data T
A ROM (read only memory) 43 storing c and an arithmetic processing unit (CPU) 44 for performing a torque correction operation are provided.

Here, the detected torque T obtained by processing the output signal of the torque sensor 20 in the signal processing circuit 30 is shown.
The signal o is obtained by adding the influence of the elastic deformation of the flexspline 11 by the wave generator 6 to the torque transmitted via the speed reducer HD. For example, as shown in FIG. This value changes correspondingly, and changes in cycles proportional to the number of rotations of the wave generator (an integer multiple of the number of rotations).
Since the speed reducer HD has the elliptical cam 5 and the wave generator 6, the waveform is changed every half rotation as shown in FIG. In this figure, the upper line To (+10) is a detection signal when the transmission torque T = 10 (Nm), and the center line To (0) is the transmission torque T =
0 (Nm) and the lower line To (−1
0) is a detection signal when the transmission torque T = −10 (Nm).

The detected torque signal To is calculated based on the A / D
After being digitized in the converter 41, the arithmetic processing unit 4
4 is corrected. This correction is performed using the torque correction data Tc stored in the ROM 43 and the counter 4.
The rotation angle position (phase) is adjusted based on the count of 2. The torque correction data Tc is data that can cancel the detected torque signal detected only by the elastic deformation of the flexspline 11 by the wave generator 6, and is detected when the transmission torque via the speed reducer HD is zero. Torque (referred to as no-load detection torque) To (0) is used. That is, when the torque transmitted through the input shaft 3 of the speed reducer HD is zero, the input shaft 3
No-load detection torque To detected when rotating
(0) is stored in the ROM 43 as the torque correction data Tc.

The torque correction is performed based on the detected torque signal To output from the signal processing circuit 30 as described above.
The torque correction data Tc stored in M43 is subtracted after adjusting the rotational angle position θw of the wave generator 6, and thereby the transmission torque Tt is calculated.
Instead of this subtraction, a value obtained by reversing the plus / minus sign of the no-load detection torque To (0) is stored as torque correction data Tc (that is, as Tc = -To (0)). Output detected torque signal T
The transmission torque Tt may be calculated by adding the torque correction data Tc to o.

FIG. 11 shows an example of such a torque correction. A value obtained by reversing the plus / minus sign of the no-load detection torque To (0) is set as the correction torque Tc ｛= − To (0)｝. Then, for example, the detection signal To (+1) when the transmission torque T = 10 (Nm) shown by the solid line in the drawing
When the torque correction data Tc indicated by the broken line in FIG. 0) is added in a state where the rotation phases are matched, a substantially flat transmission torque Tt (+10) is obtained as shown in FIG.

The detected torque detected only by the elastic deformation of the flexspline 11 by the wave generator 6 is equal to the no-load detected torque To (0), and does not change depending on the magnitude of the transmission torque. It is. However, the no-load detection torque To
(0) changes when the temperature of the reduction gear HD changes. This is because the viscosity of the lubricating oil changes according to the temperature. For this reason, the no-load detection torque To (0) corresponding to each temperature is detected, and all of these data are stored in the ROM 43. Have been. Then, when performing the torque correction, the torque correction data Tc corresponding to the temperature detected by the temperature sensor 52 is read to perform the torque correction.

Instead of storing the data for each temperature in this way, only the torque correction data at the reference temperature is stored in the ROM 43, and the correction coefficient of the torque correction data for the temperature change is measured and stored. When performing torque correction, a correction coefficient for the detected temperature may be read, and data obtained by multiplying the correction coefficient by the torque correction data read from the ROM 43 may be used.

[0041]

As described above, according to the present invention,
The transmission torque is obtained by correcting the detected torque detected by the torque sensor based on the torque correction data stored in the correction data storage means. The transmission torque of the flex spline by the wave generator is determined in accordance with the rotation angle of the wave generator. The torque detected based only on the elastic deformation is stored as torque correction data corresponding to the rotation angle of the wave generator, and the torque correction data is subtracted from the actual detected torque. Accurate transmission torque without influence of deformation can be obtained. The no-load detection torque detected by the torque sensor at the time of no load can be used as the torque correction data.

However, since the torque correction data fluctuates according to the temperature of the wave speed reducer, the torque correction data is measured and set for each temperature of the wave speed reducer, and the torque correction data corresponding to the actual temperature of the wave speed reducer is set. It is preferable to determine the transmission torque using

[Brief description of the drawings]

FIG. 1 is a sectional perspective view showing a wave reducer in which a transmission torque detecting device according to the present invention is used.

FIG. 2 is a perspective view showing a flex spline member constituting the speed reducer and a torque sensor attached to the flex spline member.

FIG. 3 is a perspective view showing a torque sensor and a processing circuit.

FIG. 4 is a cross-sectional view showing a torque sensor attached to a flex spline member.

FIG. 5 is a plan view of a first magnetic layer constituting the torque sensor.

FIG. 6 is a plan view of an exciting printed wiring board constituting the torque sensor.

FIG. 7 is a plan view of a detection printed wiring board constituting the torque sensor.

FIG. 8 is an electric circuit diagram showing a processing circuit.

FIG. 9 is a block diagram illustrating a configuration of a transmission torque detection device according to the present invention.

FIG. 10 is a graph showing a detected torque signal detected by a torque sensor.

FIG. 11 is a graph illustrating a process of correcting a detected torque signal using torque correction data.

FIG. 12 is a graph showing a result of correcting a detected torque signal with torque correction data.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Support case 6 Wave generator 10 Flex spline member 20 Torque sensor 30 Signal processing circuit 40 Torque correction arithmetic unit 50 Servo amplifier 51 Encoder 52 Temperature sensor 60 Electric motor HD Wave reduction gear

Claims (4)

[Claims] An apparatus for detecting a transmission torque of a wave reducer having a wave generator and a flex spline, comprising: a torque sensor for detecting a transmission torque transmitted via the wave reducer; and a rotation of the wave generator. A rotation angle sensor that detects an angular position; a correction data storage unit that measures and stores torque correction data corresponding to the rotation angle position of the wave generator; and a detection torque detected by the torque sensor, the correction data storage unit. A transmission torque detecting device for a wave speed reducer, comprising: torque correction means for obtaining a transmission torque by correcting based on stored torque correction data. 2. The torque correction data is a no-load detection torque detected by the torque sensor when there is no load, and the torque correction unit subtracts the no-load torque from the detection torque detected by the torque sensor. The transmission torque detecting device according to claim 1, wherein the transmission torque is obtained by using the following method. 3. The correction data storage means measures and stores torque correction data corresponding to the temperature of the wave speed reducer, has a temperature sensor for detecting the temperature of the wave speed reducer, and the torque correction means. Reading torque correction data corresponding to the temperature detected by the temperature sensor from the correction data storage means, and correcting the detected torque based on the read torque correction data. The transmission torque detecting device according to any one of the preceding claims. 4. A method for detecting transmission torque of a wave reduction gear having a wave generator and a flexspline, wherein the transmission torque of the wave reduction gear in a no-load state is detected in accordance with a rotation angle position of the wave generator. The detected torque in the no-load state thus detected is stored as torque correction data, and the transmission torque of the wave reducer in the torque transmission state is detected in accordance with the rotational angle position of the wave generator. A transmission torque detection method for a wave speed reducer, wherein the transmission torque is obtained by adjusting the rotation angle phase of the wave generator from the detected torque and subtracting the torque correction data.