WO2020004715A1

WO2020004715A1 - Integrated actuator using magnetic sensor

Info

Publication number: WO2020004715A1
Application number: PCT/KR2018/011474
Authority: WO
Inventors: Sun-Woo Lee; Kook-sun LEE; Jun-Ho Kim; Hyeon-Woo Park
Original assignee: Alienrobot Inc.
Priority date: 2018-06-27
Filing date: 2018-09-28
Publication date: 2020-01-02
Also published as: JP2020528995A

Abstract

The present invention relates to an integrated actuator using a magnetic sensor. According to one aspect of the present invention, a measurement apparatus of at least one of an absolute angle and a relative angle which are related to rotation of a gear by a motor includes: a magnet; and a magnetic sensor in which at least one of the size and orientation of a magnet field of the magnet detects a change in the magnetic property of the magnet by rotation of the gear.

Description

INTEGRATED ACTUATOR USING MAGNETIC SENSOR

The present invention relates to an integrated actuator using a magnetic sensor. Particularly, the present invention relates to a hollow-type magnetic encoder using a plurality of magnetic sensors which requires no multi pole magnet or precise gear and an integrated actuator using a magnetic sensor which is coupled with the encoder, allowing epoch-marking enhancement of the performance of products.

Recently, robots have been applied to simple and repetitive jobs or potentially dangerous jobs in the industry world, allowing increasing productivity and allocating manpower to high efficiency of jobs.

As one example, it is essential to install a conveyor belt for transferring necessary parts and to load and unload such parts for the assembly process, in the assembly line of a factory. These jobs were performed manually by peoples in the past and caused injuries, such as spinal cord compression.

Recently, articulated robots have replaced these jobs, allowing dramatically increasing safety and productivity.

Meanwhile, a joint of a robot may be equipped with a motor for applying torque, a reducer for multiplying torque of the motor, and a device for measuring a rotation angle of the joint.

However, conventionally such parts have been manufactured individually and then assembled, allowing generating error when assembled and causing a drawback in minimization.

Recently, robot actuators incorporating such parts have been being sold, allowing solving these problems.

When using a motor-gear-encoder integrated actuator, it has advantages of easy manufacture of the joint of a robot.

Conventional integrated actuator mounts an On-axis magnetic sensor, allowing measuring the location of an output axis. Some manufacturers have been dominating the additional design method for mounting the magnetic sensor in advance.

However, currently in the technology of a magnetic encoder, the Off-axis manner enabling the design of a hollow axis has been developing more rapidly than On-axis manner. Thus, it is required to develop the technology of a magnetic encoder applying the Off-axis manner and also an integrated actuator mounting such a magnetic sensor.

The present invention relates to an integrated actuator using a magnetic sensor.

Particularly, the present invention relates to a hollow-type magnetic encoder using a plurality of magnetic sensors which requires no multi pole magnet or precise gear and an integrated actuator using a magnetic sensor which is coupled with the encoder, allowing epoch-marking enhancement of the performance of products.

Meanwhile, the present invention is not limited to the above-mentioned technical problems, and unless specifically stated otherwise herein, other technical problems will be clearly understood by those of ordinary skilled in the art from the following description.

According to a first aspect of the present invention, a measurement apparatus of at least one of an absolute angle and a relative angle which are related to rotation of a gear by a motor may include: a magnet; and a magnetic sensor in which at least one of the size and orientation of a magnet field of the magnet measures a change in the magnetic property of the magnet by rotation of the gear.

According to another aspect of the present invention, the magnet is a single-sided round two pole magnet.

According to another aspect of the present invention, the magnetic sensors may exist in a plurality, and the plurality of magnetic sensors may be disposed at a predetermined separation distance about the magnet.

According to another aspect of the present invention, the magnet may be a single-sided round two pole magnet, the magnet sensors may exist in a plurality, and the plurality of magnet sensors may be disposed at a predetermined separation distance adjacent to the single-sided round two pole magnet, allowing compensating a distortion in values changed due to a rotation by the gear.

According to another aspect of the present invention, the measurement apparatus may apply a hollow-type actuator.

According to a second aspect of the present invention, an actuator may include: a motor; a gear which is rotated by the motor; a gear box which is coupled with the gear; and a measurement apparatus according to claim 1 which is inserted into at least a portion of the gear box and measures at least one of an absolute angle and a relative angle related to rotation of a gear by a motor.

According to another aspect of the present invention, the gears may exist in a plurality, and the actuator may further include: an input case 2; a first internal gear 5 which is coupled to the input case 2 among the plurality of gears; an eccentric shaft 3 which is coupled to an external gear 4 and the input case 2 among the plurality of gears, and which one end engages with the first internal gear 5, allowing rotation; a second internal gear which engages with opposite end of the eccentric shaft 3 among the plurality of gears, allowing rotating together; an output carrier 6 which outputs power transferred to the second internal gear 7; and an output case 8 which is equipped with a bearing 9 which the output carrier 6 passes through.

According to another aspect of the present invention, at least a portion of the input case 2 and the first internal gear 5, the second internal gear 7 and the output carrier 6, and the gear box and the measurement apparatus is manufactured to be integrated.

According to another aspect of the present invention, at least a portion of the eccentric shaft 3, the external gear 4, the output carrier 6, the gear box and the measurement apparatus is manufactured into a hollow-type.

Therefore, the present invention is capable of providing a user with an integrated actuator using a magnetic sensor.

Particularly, the present invention is capable of providing a user with a hollow-type magnetic encoder using a plurality of magnetic sensors which requires no multi pole magnet or precise gear and an integrated actuator using a magnetic sensor which is coupled with the encoder, allowing epoch-marking enhancement of the performance of products.

Meanwhile, effects of the present invention are not limited to the aforementioned effects, and other effects not covered herein will be clearly understood by those of ordinary skilled in the art from the following description.

FIG. 1 shows one example of a conventional cycloid gear related with the present invention.

FIG. 2 shows one example of a structure in which a separate sensor support is installed and a location is measure using a sensor, such as a magnetic encoder, with respect to the present invention,

FIG. 3 shows one example in which the structure provided in FIG. 2 is improved, allowing forming a hole which a reducer and a shaft penetrate and installing a rotation load inside a hollow type shaft.

FIG. 4 shows one example of an integrated actuator using a small cycloid reducer, with respect to the present invention,

FIG. 5 is a view for describing the On-axis manner and The Off-axis manner, with respect to a magnetic sensor.

FIG. 6 is a view for describing the operation of an integrated actuator related to the present invention.

FIG. 7A to FIG. 7C show one example of an integrated actuator which mounts an On-axis magnetic sensor, with respect to the present invention.

FIG. 8 shows a structure using conventional hollow axis and spur gear, and a structure of an integrated actuator using a magnetic sensor according to the present invention.

FIG. 9 and FIG. 10 show an integrated actuator using a magnetic sensor according to the present invention.

FIG. 11 is one example of a hollow-type actuator according to the present invention.

A joint of a robot may be equipped with a motor for applying torque, a reducer for multiplying torque of the motor, and a device for measuring a rotation angle of the joint.

Robot actuators incorporating such parts have been being sold, allowing solving these problems.

Referring to FIG. 1, a conventional cycloid gear 100 uses inner circumferential surface of a case as an internal gear 30. Two sheets of

external gears

40 and 50 are installed, allowing being contacted with an inner gear 30. The

external gears

40 and 50 are coupled with an output carrier 70 by using a plurality of output pins 60 penetrating each hole formed on the external gears. A described above, the conventional cycloid gear requires complicated manufacturing and assembling processes. Therefore, this causes a drawback in minimization.

A rotation angle of the output carrier 70 of the reducer even corresponds to a rotation angle of the joint of the robot. Therefore, a measurement method therefor should be equipped together.

FIG. 2 shows one example of a structure in which a separate sensor support is installed to an output carrier and a location is measured using a sensor, such as a magnetic encoder, with respect to the present invention.

Referring to FIG. 2, a separate sensor support 210 may be installed to the output carrier 70, and a location may be measured using a sensor 130a, such as a magnetic sensor.

However, according to the structure shown in FIG. 2, the separate sensor support 210 for supporting the sensor 130a may preclude a joint from rotating a full 360 degrees. Further, a shaft direction length is increased and thus such a structure may be without merit in an aspect of design when used for the articulated robot which has a shaft integrated structure.

Related art for solving such problems is discloses in Korea Patent Laid-open No. 10-2013-0045692, and Fig. 3 will be described herein after.

FIG. 3 shows one example in which the structure according to FIG. 2 is improved, allowing forming a hole which penetrates a reducer and a shaft and installing a rotation load inside a hollow type shaft.

Referring to FIG. 3, a hole is formed, allowing penetrating a reducer 90 and a shaft 220 and a rotation load is installed inside a hollow type shaft.

However, according to the structure shown in FIG. 3, it is positively necessary to use the hollow type shaft. Therefore, a stiffness may become weaker likewise a conventional hollow type actuator. Further, as the rotation load is installed inside the shaft, the interior region of the hollow shat could not be used in the wiring connection.

Further, FIG. 4 shows one example of an integrated actuator using a small size cycloid-type reducer according to the present invention.

Referring to FIG. 4, the small size cycloid-type reducer included in an actuator according to the present invention has a definitely different structural type from that of the conventional actuator of FIG. 1.

In particular, according to the present invention, an eccentric shaft 3 is fixed to a motor 1 by a bearing, and the eccentric shaft 3 is likewise fixed to a 2-tier external gear 4 by a bearing.

Further, each of a first tier and a second tier of the external gear 4 engages with a first internal gear 1 attached to the input case 2 and a second internal gear 7 attached to the output carrier 6, respectively, allowing rotation. The output carrier 6 attached with the second internal gear 2 penetrates a crossed roller bearing 9 which is fixed to the output side case 8.

At this time, a pin roller bearing may be additionally added between the external gear 4 and the first internal gear 5, or between the external gear 4 and the second gear 7, allowing reducing friction between gears engaging with each other.

Therefore, the structure in FIG.4 according to the present invention is different from the aforementioned conventional structure in FIG. 1 in that there is no need for a plurality of output pins to penetrate a plate gear, allowing simple assembly and minimizing a size dramatically.

Meanwhile, encoders capable of being applied to the aforementioned actuator may include a rotary encoder, an optical encoder, a magnetic encoder, etc.

The rotary encoder is an angle measurement sensor which converts a mechanical displacement of the rotation direction into a digital signal, and the importance thereof is being magnified in the field which requires precise measurement of speed/location of a rotation part for high-performance control of machine tools or robots.

Further, the optical encoder uses a disc having slits disposed at regular intervals in a rotation axis, and an optical detector (light-emitting part and light-receiving part).

At this time, if the light of the light-emitting part passes through the slits etched on the disc and then reaches to the light-receiving part, such encoders may be classified into an absolute encoder and an incremental encoder according to the shape of the slits in the manner of outputting patterns of the disc by using the detector.

The absolute optical encoder has drawbacks that the number of output signal lines is not only increased but the size of the disc is relatively big.

As an alternative therefor, the following magnetic encoder using the magnetic sensor may be used.

The magnetic encoder may detect the location of the rotation axis in various manners according to the kind of magnetic sensors or that of magnets.

The kind of magnetic sensors in use includes a hall sensor or a magnetroresistor. Recently, as the integration technology of semiconductors has been applied, semiconductor IC device types are on sale.

Referring to FIG. 5, an installation method of a magnetic sensor is classified into the On-axis manner for installing a sensor in the central part of a rotation axis and the Off-axis manner for installing such a sensor at a separation distance from the central part of the rotation axis.

Referring to FIG. 5, since the Off-axis manner installs the magnetic sensor at a separation distance from the rotation axis whose rotation angle needs to be measured, it is possible to use a hollow-type rotation axis. However, it has been known that the distortion of a measurement signal and the noise become increased relatively more than in On-axis manner.

Referring to (a) to (c) of FIG. 6, a motor may be embodied as DC / BLDC / PMSM, and a gear may be embodied as Harmonic gear / Cycloid gear / Planetary gear.

Further, location measurement sensors (encoders) are used, wherein an incremental encoder of the input axis may be embodied as high resolution and an absolute encoder of the output axis may be used for the purpose of measuring a rotation angle of a joint of a robot.

Conventional integrated actuators mount a magnetic sensor mainly in On-axis manner, allowing measuring a location of the output axis, and additional mechanism design methods have been developing for mounting the magnetic sensor.

On the other hand, a method according to the present invention applies The Off-axis manner, allowing having advantages of enabling minimization and a hollow-type design compared to the conventional integrated actuator. Further, drawbacks of The Off-axis manner, such as signal distortion, may be overcome by using a plurality of the magnetic sensors.

Prior to detailed description of the present invention, an integrated actuator mounting the magnetic sensor in the On-axis manner will be described.

FIG. 7A and FIG. 7B show one example of an integrated actuator which mounts an On-axis magnetic sensor, with respect to the present invention.

Referring to FIG. 7A, the On-axis manner is illustrated, wherein a plurality of spur gears is installed and each of

magnetic sensors

343b and 353b is installed to the rotation axis of two

spur gears

340 and 350 which maintain a rotation ratio of 1:1 with an output axis by combining gear ratios of the spur gears, respectively.

A structure illustrated in FIG. 7A has not an advantage of the hollow type design, whereas such a structure also has drawbacks of the weight increase and complicated structure due to the use of the plurality of spur gears.

Further, referring to FIG. 7B, the Off-axis manner is illustrated, wherein a hollow-type shaft is installed penetrating a gear and a rotation rod is passed through the interior region of the hollow-type shaft, allowing installing the magnetic sensor to an end portion of the rotation rod 600.

A structure illustrated in FIG. 7B is distinctive in using the interior region of a 2-tier cycloid gear which is suitable for the easy hollow-type design. However, such a structure has a drawback not enabling the hollow-type design due to the installation of the rotation rod.

Further, referring to FIG. 7C, a structure is illustrated, wherein a portion of an output carrier 6 of a small cycloid reducer is molded into a spur gear shape 10, and an angle detection part for measuring an absolute angle and a relative angle may be equipped to the side of another spur gear 11 which engages with the spur gear 10, wherein the angle detection part may include a magnetic encoder 12 and a magnet 13.

Accordingly, a method applied to the present invention is to mold a portion of a dynamic power transmission structure together with the output carrier 6 of the cycloid reducer.

That is, FIG. 7C shows the On-axis manner in which a spur shape is molded to an output member of a cycloid gear, and a magnetic sensor is installed to a rotation axis of the spur gear having a rotation ratio of 1:1 with an output axis.

Herein, there are advantages of reducing a length in the axial direction and enabling the hollow-type design. However, there is also a drawback of location measurement errors which may be occurred due to the abrasion of the spur shape of the output member for dynamic power transmission and the spur gear.

As described above in FIG. 7A to 7C, notwithstanding additional mechanism (gear, rotation rod) is required, the on-axis manner is used rather than The Off-axis manner.

That is, in a case of the Off-axis manner using a multi pole magnet, it is relatively difficult to manufacture the multi pole magnet compared to a single-sided two pole magnet. It is also difficult to detect an absolute location.

Since two ring magnets having a specific type arrangement of the N and S poles and a phase difference are used, there are difficulties in manufacture thereof and absolute location detection.

Further, even though there is the Off-axis manner using the single-sided two pole magnet, a complicated signal processing method is required so as to overcome harmonic errors and nonlinear properties occurred due to a separation distance from the magnet.

Ultimately, in such a current state, it is required to develop a hollow-type magnetic encoder which requires neither a multi pole magnet using a plurality of magnetic sensors that are the main cause of price increases nor precise gears. In addition thereto, required are products which are coupled with an integrated actuator and whose performance is thus dramatically enhanced.

Therefore, the present invention intends to provide an integrated actuator using a magnetic sensor to solve the aforementioned problems.

In particular, the present invention intends to provide a user with a hollow-type magnetic encoder using a plurality of magnetic sensors which requires no multi pole magnet or precise gear and an integrated actuator using a magnetic sensor which is coupled with the encoder, allowing epoch-marking enhancement of the performance of products.

Referring to (a) and (b) of FIG. 8, methods for using a hollow axis and a spur gear are illustrated as methods for using an additional mechanism and an On-axis magnetic sensor.

Further, referring to (c) of FIG. 8, methods for using a signal processing algorithm, a sing-sided two pole magnet 3400 and a plurality of Off-axis magnetic sensors 3600 are illustrated as a structure according to the present invention.

Referring to FIG. 9 and FIG. 10, since the Off-axis manner according to the present invention is capable of solving the above described problems, it is predictable to replace the conventional On-axis manner.

In particular, a method according to the present invention overcomes limitations of the Off-axis manner by using a plurality of magnetic sensors 3600.

Features of the structure and method according to the present invention via FIG. 9 are as follows.

Firstly, a single-sided two pole magnet 3400 is used.

Since a multi pole magnet is manufactured by using a relatively complicated type magnetizing yoke compared to a single-sided two pole magnet 3400, it is difficult to manufacture such a multi pole magnet and a specific type arrangement of poles is required so as to measure an absolute location.

On the other hand, the manufacture of the single-sided two pole magnet 3400 is relatively simple and it is easy to measure an absolute location, allowing increasing the productivity and price competitiveness of products.

Secondly, a signal processing part is used in the present invention. When using the single-sided magnet 3400, it may be possible to overcome problems that measurement errors are generated due to the weak output of a sensor which is perpendicular to a magnetic field, besides signal distortions occurred by noise.

That is, a method according to the present invention applies a signal processing method that disposes a plurality of magnetic sensors 3600 around a magnet 3400 at a specific separation distance, allowing compensating the signal distortion.

Further, the present invention may apply an embodiment that disposes the magnetic sensor 3600 to not an output end but an input end, allowing using the sensed information additionally.

Further, the sensor disposed to the input end may use different type of a sensor (for example, an optical sensor) which is capable of sensing the move of the input end, besides the magnetic sensor 3600.

Lastly, the present invention is characterized by enabling manufactured into a hollow-type design.

That is, additional mechanisms (a rotation rod, a gear, etc.) mentioned in FIG. 7A to FIG. 7C are not needed, allowing reducing the weight of products and the design complexity thereof dramatically.

In particular, when mounted to an integrated actuator, the magnetic sensor 3600 and a ring magnet 3400 are directly installed to an output axis, allowing a compact size hollow-type design.

For example, FIG. 9 illustrates a method for measuring a rotation angle of the input axis as the On-axis manner similar to the conventional method. However, it may be excluded or used combined with other methods.

In particular, FIG. 11 illustrates an embodiment of a compact size hollow-type actuator in which the method according to the present invention is applied.

Therefore, the present invention may provide a user with an integrated actuator using a magnetic sensor.

In particular, the present invention may provide a user with a hollow-type magnetic encoder using a plurality of magnetic sensors which requires no multi pole magnet or precise gear and an integrated actuator using a magnetic sensor which is coupled with the encoder, allowing epoch-marking enhancement of the performance of products.

The embodiments of the present invention as described above may be implemented via a variety of means. For example, the embodiments of the present invention may be implemented via hardware, firmware, software, or combination thereof.

In a case of implementation through hardware, a method according to the embodiments of the present invention may be implemented through one or more of Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), Field Programmable Gate Array s(FPGAs), processors, controllers, micro-controllers, microprocessors, etc.

In a case of implementation through firmware or software, a method according to the embodiments of the present invention may be implemented into a type of a module performing technical functions or operations, a procedure, a mathematical function, etc. A software code may be stored in a memory unit and operated by a processor. The memory unit may be positioned inside or outside the processor, allowing transmitting and receiving data with the processor by publicly known means.

The detailed description of preferable embodiments of the present invention disclosed as the above is provided, allowing being embodied and implemented by those of ordinary skilled in the art. Even though describing referring to preferable embodiments of the present invention in the above, those of ordinary skilled in the art may understand that the present invention may be modified and changed within the scope of the present invention. For example, those of ordinary skilled in the art may use the respective elements described in the aforementioned embodiments by combination thereof. Therefore, the present invention is not limited to the embodiments disclosed herein, but intends to grant the widest scope corresponding to principals and novel features disclosed herein.

The present invention may be embodied in any other specific forms within the scope of the concept and essential features. Therefore, the above detailed description should not be interpreted restrictively in all aspects but considered as examples. The scope of the present invention should be determined by rational interpretation, and all modifications within the scope equivalent to the present invention should be included in the present invention. The present invention is not limited to the embodiments disclosed herein, but intends to grant the largest scope corresponding to principals and novel features disclosed herein. Further, embodiments may be configured by combination of claims which are not explicitly in citation relation with the scope of claimed inventions, or may be included as new claims by amendments after filing an application.

Claims

A measurement apparatus of at least one of an absolute angle and a relative angle which are related to rotation of a gear by a motor comprising:

a magnet; and

a magnetic sensor in which at least one of the size and orientation of a magnet field of the magnet measures a change in the magnetic property of the magnet by rotation of the gear.
The measurement apparatus of claim 1, wherein

the magnet is a single-sided round two pole magnet.
The measurement apparatus of claim 1, wherein

the magnetic sensors exist in a plurality, and

the plurality of magnetic sensors is disposed at a predetermined separation distance about the magnet.
The measurement apparatus of claim 1, wherein

the magnet is a single-sided round two pole magnet,

the magnet sensors exist in a plurality, and

the plurality of magnet sensors is disposed at a predetermined separation distance adjacent to the single-sided round two pole magnet, allowing compensating a distortion in values changed due to a rotation by the gear.
The measurement apparatus of claim 1, wherein

the measurement apparatus applies a hollow-type actuator.
An actuator comprising:

a motor;

a gear which is rotated by the motor;

a gear box which is coupled with the gear; and

a measurement apparatus according to claim 1 which is inserted into at least a portion of the gear box and measures at least one of an absolute angle and a relative angle related to rotation of a gear by a motor.
The actuator of claim 6, wherein

the gears exist in a plurality, and

the actuator further comprises:

an input case 2;

a first internal gear 5 which is coupled to the input case 2 among the plurality of gears;

an eccentric shaft 3 which is coupled to an external gear 4 and the input case 2 among the plurality of gears, and which one end engages with the first internal gear 5, allowing rotation;

a second internal gear which engages with opposite end of the eccentric shaft 3 among the plurality of gears, allowing rotating together;

an output carrier 6 which outputs power transferred to the second internal gear 7; and

an output case 8 which is equipped with a bearing 9 which the output carrier 6 passes through.
The actuator of claim7, wherein

at least a portion of the input case 2 and the first internal gear 5, the second internal gear 7 and the output carrier 6, and the gear box and the measurement apparatus is manufactured to be integrated.
The actuator of claim7, wherein

at least a portion of the eccentric shaft 3, the external gear 4, the output carrier 6, the gear box and the measurement apparatus is manufactured into a hollow-type.