JP2001082913A - Angle sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an angle sensor capable of being easily incorporated into a ball joint and measuring the rotating angles of the ball joint on three axes. SOLUTION: Two first coils 22a, 22b with their centers coinciding with the center of the sphere portion 12 of a ball joint are wound on the outer surface of the sphere portion 12, and the sphere portion is freely rotatably and slidably mounted within an approximately spherical recess formed in a receiving member 14. A joint shaft 10 extends from the spherical portion. Two second coils 24a, 24b surrounding the recess and having their centers coinciding with the center of the sphere portion are wound on the receiving member. Voltages of different frequencies are supplied to the second coils to generate alternating magnetic fields, and electromotive forces induced on the first coils by the alternating magnetic fields are separated from one another according to frequency and detected. The rotating angles of the joint shaft about three axes are calculated from the induced electromotive forces detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an angle detection sensor, and more particularly to an angle detection sensor for detecting a rotation angle of a ball joint about three axes.

[0002]

2. Description of the Related Art In recent years, there has been provided a robot using a ball joint having three degrees of freedom as a bearing for an operating lever such as a joint or a joystick of a robot. For example, in the field of robots, joints having three degrees of freedom, such as hip joints and ankle joints, are configured using ball joints in order to achieve weight reduction and multi-degree of freedom of motion. Such a ball joint has the advantage that the mechanism can be made lightweight and simple.

When a ball joint is used, it is necessary to measure the rotation angles of three axes of the ball joint in order to control the joint angle by pulling with a wire or the like. In general,
For three-dimensional angle measurement, a measuring element using a Hall element,
It is known to use a three-dimensional position measuring device for VR use using an alternating magnetic field.

[0004]

However, the measuring element and the three-dimensional position measuring apparatus using the Hall element as described above are difficult to incorporate into a ball joint due to their structures, and the rotation angle of the ball joint is difficult. Not suitable for detection. Therefore, an object of the present invention is to provide an angle detection sensor which can be easily incorporated into a ball joint and can measure a three-axis rotation angle of a ball joint.

[0005]

In order to achieve the above-mentioned object, an angle detection sensor according to the present invention has coils incorporated in a spherical portion of a ball joint and a receiving member slidably receiving the spherical portion. The angle of the joint axis provided in the ball joint is measured from the strength of the magnetic coupling of these coils.

The basic principle of the above angle detection sensor is that, for example, a magnetic field is generated in an outer transmitting coil provided on a receiving member and guided to a receiving coil provided in a sphere and located in a loop of the outer transmitting coil. The angle between the two coils is detected by measuring the electromotive force. The magnitude of the induced electromotive force is determined only by the angle between the transmitting coil surface and the receiving coil surface, that is, the angle of the joint axis, and does not depend on the direction.

To measure all the rotation angles around three axes as the degrees of freedom of the ball joint, at least two transmitting coils and two receiving coils are required. The combination of the transmitting and receiving coils is four coils, but the frequency of the voltage supplied to the transmitting coil is changed for each coil, and the frequency component received by each receiving coil is decomposed by a separating unit such as a band-pass filter. The angle between the two coils on the transmitting side and each coil on the receiving side can be obtained independently, and the rotation angles of all three axes can be detected.

Based on the above basic principle, the angle detection sensor according to the present invention has a spherical portion having a spherical outer surface, a joint shaft extending from the spherical portion, and a substantially spherical inner surface. And a receiving member having a recess in which the spherical portion is rotatably engaged. The angle detecting sensor detects the three-axis rotation angle of the joint shaft in the ball joint, and is wound around the outer surface of the spherical portion. And two first coils each having a center coinciding with the center of the spherical portion, and a center provided on the receiving member surrounding the recess and coincident with the center of the spherical portion. A voltage supply unit for supplying voltages having different frequencies to one of the first and second coils to generate an alternating magnetic field; and The induced electromotive force generated in the other two coils of the first and second coils according to the field is detected for each of the frequencies, and the rotational angles around the three axes of the joint shaft are calculated from the detected induced electromotive force. And a calculation unit that performs the calculation.

[0009] Further, the angle detection sensor according to the present invention comprises:
A separation unit is provided for separating the induced electromotive force generated in each coil into output voltages for each frequency, and further stores function data for defining the relationship between the angle between the first coil and the second coil and the output voltage. A storage unit is provided, wherein the calculation unit calculates the rotation angle of the joint shaft based on the detected output voltage for each frequency and the function data stored in the storage unit.

The angle between the one first coil and the one second coil is θ1a, the angle between the one first coil and the other second coil is θ2a, and the other first coil and the one second coil are θ2a. The angle between the second coil and the second coil is θ1b, and the angle between the other first coil and the other second coil is θ1b.
2b, the angle formed by the coil surfaces of the two second coils is 2ω, and the angles formed by the joint axis with respect to the x, y, and z axes passing through the center of the sphere are roll angle γ, pitch angle β, and yaw, respectively. When the angle is α, the calculation unit calculates
The θ1a, θ2a, θ1 based on the detected output voltage for each frequency and the function data stored in the storage unit.
b and θ2b are calculated, and the roll angle γ, pitch angle β, and yaw angle α are calculated based on the following equations.

[0011]

(Equation 2)

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a ball joint provided with an angle detecting sensor according to an embodiment of the present invention will be described in detail with reference to the drawings. As shown in FIG. 1, the ball joint includes a spherical portion 12 having a spherical outer surface and fixed to a joint shaft 10, and a receiving member 14 rotatably receiving the spherical portion 12. The spherical portion 12 and the receiving member 14 are formed of, for example, a synthetic resin. The joint shaft 10 is formed of, for example, brass, and extends from the outer surface of the spherical body 12 along a direction passing through the center c of the spherical body 12.

The receiving member 14 is formed in a cylindrical shape, and has a substantially spherical recess 16 opened at one end surface thereof. Most of the spherical portion 12 is slidably and rotatably mounted in the recess 16, and the joint shaft 10 extends through the opening of the recess 16. As a result, the joint shaft 10 has three axes x passing through the center c of the spherical body portion 12,
Each is freely rotatable around y and z. In addition,
The receiving member 14 is formed to be separable into two parts so that the spherical body part 12 can be attached to and detached from the recess 16.

On the other hand, an angle detection sensor 20 for detecting the rotation angle of the joint shaft 10 is provided in the ball joint configured as described above. As shown in FIG. 2, the angle detection sensor 20 is provided on the outer peripheral surface of the receiving member 14 so as to surround the two first coils 22 a and 22 b provided on the outer surface of the spherical body portion 12 and the recess 16. And two second coils 24a and 24b.

The second coils 24a and 24b function as transmitting coils, and generate alternating magnetic fields when supplied with a voltage. The first coils 22a and 22b function as receiving coils, and the second coils 24a and 24b
Generates an induced electromotive force in accordance with the alternating magnetic field formed by. Then, the induced electromotive force generated in each of the first coils 22 a and 22 b becomes a detection output of the angle detection sensor 20.

The first coils 22a and 22b are formed by winding the coated copper wires around two grooves cut on the outer surface of the spherical body 12. And 2
The first coils 22a and 22b are wound so that their centers coincide with the center c of the spherical body portion 12, respectively. The first coils 22a and 22b are wound on a circle having a normal vector perpendicular to the axial direction of the joint shaft 10, and are provided at an angle of 90 degrees with each other.
That is, in the present embodiment, the two first coils 22a and 22b are wound along a circumferential groove intersecting with the joint shaft 10 and the coil surfaces are orthogonal to each other.

The angle between the first coils 22a and 22b is set in the range of 30 ° to 90 °, more preferably in the range of 60 ° to 90 °. Also, the first coil 2
2a and 22b are provided substantially flush without protruding from the outer peripheral surface of the spherical body portion 12 so as not to hinder the movement of the spherical body portion 12 in the concave portion 16.

On the other hand, two second coils 24a, 24b
Are respectively wound in an annular shape, and the center thereof is
Is fixed to the outer peripheral surface of the receiving member 14 in a state of being coincident with the center c. Each of the second coils 24a and 24b is
Are inclined at an angle ω with respect to a plane orthogonal to the central axis of And the second coils 24a, 24b are:
It functions as a transmitting coil and generates an alternating magnetic field by passing a sinusoidal waveform voltage.

The angle 2ω formed between the two second coils 24a and 24b is set in the range of 30 ° to 90 °, and more preferably in the range of 60 ° to 90 °.

In this embodiment, the first coil 22
a and 22b have 5 turns, a diameter of 24 mm, and a second coil 24.
a and 24b are 10 turns, 35 mm in diameter, and angle ω = 15.
° formed. In this case, the first coil and the second coil
The inductances of the coils are 1.9 μH and 9.
It becomes 4 μH.

As shown in FIG. 3, the angle detection sensor 20 includes a voltage supply unit 30 such as a function generator for supplying voltages of different frequencies to the transmission second coils 24a and 24b to generate an alternating magnetic field. And a measuring unit 32 such as a spectrum analyzer for measuring the electromotive force induced in the second coils 22a and 22b for transmission. After the electromotive force measured by the measurement unit 32 is separated for each frequency by a separation unit 34 such as a band-pass filter, that is, after being separated into four outputs, the electromotive force is input to a CPU 36 functioning as a control unit and a calculation unit. Is done.

Further, as will be described later, the memory 40 serving as a storage unit stores function data which is obtained in advance through experiments or the like and defines the relationship between the output voltage and the angle. Then, the CPU 36 determines the three-axis rotation angle of the joint shaft 10, that is, the roll angle, based on the function data and the detection voltage of each frequency obtained through the separation unit 34.
Calculate the pitch angle and yaw angle.

Here, angles formed by the joint axis 10 with the x, y, and z axes are a roll angle γ, a pitch angle β, and a yaw angle α, respectively. The angle between the first coil 22a and the second coil 24a is θ1a, the angle between the first coil 22a and the second coil 24b is θ2a, and the first coil 22
Assuming that the angle between b and the second coil 24a is θ1b and the angle between the first coil 22b and the second coil 24b is θ2b, the roll angle γ, the pitch angle β, and the yaw angle α are expressed by the following equations. .

[0024]

(Equation 3)

The function between the output voltage and the angle described above is obtained by the following method. That is, using one second coil on the transmitting side and one first coil on the receiving side, the relationship between the angle formed by these two coils and the amplitude of the output voltage is measured. For example, a sine wave having an amplitude Vcc = 5 (V) and an oscillation frequency f = 1 (MHz) is supplied from the voltage supply unit 30 to the second coil 24a to generate an alternating magnetic field, and the first coil 22a
The component Vout (V) of the frequency f of the electromotive force induced by the measurement unit 32 is measured via the measurement unit 32 and the separation unit 34.

FIG. 4 shows the results of the above measurement.
In the figure, x represents actual measured values, and these measured values are approximated by straight lines. Then, from the obtained approximate straight line, the second
A function indicating the relationship between the angle θ1a of the first coil 22a with respect to the coil 24a and the output voltage is obtained.

In the same manner as above, a function indicating the relationship between the other angles θ1b, θ2a, θ2b and the output voltage is obtained. The four functions thus obtained are stored in the memory 40 as data.

On the other hand, by separating the electromotive force induced in the first coil 22a on the receiving side for each of two frequencies, output voltages corresponding to the angles θ1a and θ2a are obtained, and the first coil 22b on the receiving side is obtained. The detection voltage corresponding to the angles θ1b and θ2b can be obtained by separating the electromotive force induced in the above for every two frequencies.

For example, one of the second coils 24a has an amplitude of 5
V, a voltage having an oscillation frequency of 1 MHz, and the other second coil 24
When a voltage of 5 V and a voltage of an oscillation frequency of 1.5 MHz are supplied to b, the induced electromotive force generated in one first coil 22a is as shown in FIG. Fig. 5
As shown in (b), the first coil 22a and the second coil 2
4a, and an output voltage corresponding to an angle θ2a between the first coil 22a and the second coil 24b as shown in FIG. 5C.

The induced electromotive force generated in the other first coil 22b is as shown in FIG. 6A. When the induced electromotive force is separated for each frequency by the separation unit 34, FIG.
As shown in (b), the first coil 22b and the second coil 2
4a, and an output voltage corresponding to an angle θ2b between the first coil 22b and the second coil 24b as shown in FIG. 6C.

Then, the angles θ1a, θ2a, θ1b, θ2b are obtained from the obtained four detected voltages and the above-mentioned functions, and the roll angle γ, pitch angle β, yaw angle α Is calculated.

The present inventors conducted the following experiment in order to check the detection accuracy of the angle detection sensor 20 configured as described above. As shown in FIG. 7, the pitch angle γ of the joint axis 10 of the ball joint is fixed at 50.8 ° and the roll angle β is fixed at 0 °, and the yaw angle α is changed from 0 ° to 360 ° every 15 °. The output voltage at the time was measured.
Multiplexing of transmission by frequency was not performed, and a sinusoidal voltage having an amplitude of 5 (V) and an oscillation frequency of 1 (MHz) was independently applied to the second coil for transmission.

FIG. 8 shows a roll angle γ, a pitch angle β, and a yaw angle α calculated from the obtained output voltages. However, the output of the pitch angle β is turned back at 180 °. As can be seen from this figure, the average value of the pitch angle β is 44.9.
And the average value of the roll angle γ was −2.9 °, and values substantially similar to the actual pitch angle γ = 50.8 ° and the roll angle β = 0 ° could be obtained. At the same time, the yaw angle α was shifted by about 5 ° on average from the actual value.

The value shift as described above is a drift in a certain direction, and an error caused by noise or the like is small. For this reason, the approximation straight line for obtaining the function indicating the angle-output voltage described above is more accurately determined, and by winding each coil with higher accuracy, the above-described error is reduced and highly accurate detection becomes possible.

As described above, according to the angle detection sensor 20 having the above-described configuration, the first coils 22a and 22b are provided on the outer surface of the spherical body 12 forming the ball joint, and the second member surrounding the recess 16 is formed in the receiving member 14. By providing the coils 24a and 24b, it is possible to easily incorporate the coils into the ball joint. At the same time, a voltage is supplied to the second coils 24a and 24b to generate an alternating magnetic field, and the electromotive force induced in the first coils 22a and 22b is detected. Can be accurately detected.

The present invention is not limited to the above-described embodiment, but can be variously modified within the scope of the present invention. For example, in the above-described embodiment, the first coil is the receiving side, and the second coil is the transmitting side. Conversely, the voltage is supplied to the first coil to be the transmitting side, and the second coil is used as the receiving side. You may.

The number of the first coil and the number of the second coil are each two, but may be three or more, and the detection accuracy can be improved by increasing the number. Furthermore,
The materials of the spherical body, the receiving member, and the joint shaft can be changed as necessary.

[0038]

As described in detail above, according to the present invention, it is possible to provide an angle detection sensor which can be easily incorporated into a ball joint and can accurately measure the three-axis rotation angle of the ball joint. .

[Brief description of the drawings]

FIG. 1 is a plan view and a sectional view showing a ball joint according to an embodiment of the present invention.

FIG. 2 is a diagram showing first and second coils of an angle detection sensor provided on the ball joint.

FIG. 3 is a block diagram schematically showing a configuration of the angle detection sensor.

FIG. 4 is a graph showing a result of measuring a relationship between a coil angle and an output voltage.

FIG. 5 is a graph showing an induced electromotive force generated in one second coil of the angle detection sensor and an induced electromotive force separated for each frequency.

FIG. 6 is a graph showing the induced electromotive force generated in the other second coil of the angle detection sensor and the induced electromotive force separated for each frequency.

FIG. 7 is a view showing an experimental method for measuring a three-axis rotation angle of the ball joint.

FIG. 8 is a graph showing measurement results of a roll angle, a pitch angle, and a yaw angle in the above experiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Joint axis 12 ... Spherical part 14 ... Receiving member 16 ... Concave part 20 ... Angle detection sensor 22a, 22b ... 1st coil 24a, 24b ... 2nd coil

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F063 AA35 BA30 CA40 DA01 GA29 GA33 GA37 KA01 KA06 LA04 LA07 2F077 AA49 JJ01 JJ06 PP06 TT06 TT23

Claims (6)

[Claims] 1. A sphere having a spherical outer surface, a joint shaft extending from the sphere, and a recess having a substantially spherical inner surface and rotatably engaged with the sphere. An angle detection sensor for detecting a three-axis rotation angle of the joint shaft in a ball joint having a receiving member, the center being wound on the outer surface of the spherical portion and coinciding with the center of the spherical portion. Two first coils respectively provided with the receiving member surrounding the recess, and two second coils each having a center coinciding with the center of the spherical portion; A voltage supply unit for supplying voltages having different frequencies to one of the two coils and the second coil to generate an alternating magnetic field, and the other two coils of the first and second coils by the alternating magnetic field The induced electromotive force generated at the joint axis is detected for each frequency, and the detected induced electromotive force
An angle detection sensor, comprising: a calculation unit that calculates each of the rotation angles about the axis. 2. The angle detection sensor according to claim 1, further comprising a separation unit for separating an induced electromotive force generated in each of the coils into an output voltage for each frequency. 3. A storage unit for storing function data defining a relationship between an angle between the first coil and the second coil and an output voltage, wherein the calculation unit is configured to output the output voltage for each of the detected frequencies. The angle detection sensor according to claim 2, wherein the rotation angle of the joint shaft is calculated based on the function data stored in the storage unit. 4. An angle between the one first coil and the one second coil is θ1a, an angle between the one first coil and the other second coil is θ2a, and the other first coil and the second coil are θ1a. The angle between one of the second coils is θ1b, and the angle between the other first coil and the other second coil is θ1b.
2b, the angle formed by the coil surfaces of the two second coils is 2ω, and the angles formed by the joint axis with respect to the x, y, and z axes passing through the center of the spherical portion are a roll angle γ, a pitch angle β, and a yaw, respectively. When the angle is α, the calculation unit calculates the θ1 based on the detected output voltage for each frequency and the function data stored in the storage unit.
The angle detection sensor according to claim 3, wherein a, θ2a, θ1b, and θ2b are respectively calculated, and the roll angle γ, the pitch angle β, and the yaw angle α are calculated based on the following equations. (Equation 1) 5. The angle between the coil surfaces of the two first coils is set to 30 ° to 90 °, and the angle between the coil surfaces of the two second coils is set to 30 ° to 90 °. The angle detection sensor according to any one of claims 1 to 4, wherein: 6. The angle detection sensor according to claim 5, wherein the angle formed between the coil surfaces of the two second coils is set to 50 to 60 °.