WO2022041064A1

WO2022041064A1 - Method and apparatus for robot joint status monitoring

Info

Publication number: WO2022041064A1
Application number: PCT/CN2020/111857
Authority: WO
Inventors: Ge Xiong; Sheng Zhang
Original assignee: Rethink Robotics Gmbh; Siemens Ltd., China
Priority date: 2020-08-27
Filing date: 2020-08-27
Publication date: 2022-03-03

Abstract

A method, apparatus, system and computer-readable medium for robot joint status monitoring are presented. A method (600) for robot joint status monitoring includes: calculating (S601) accumulative damage to a joint of a manipulator of an industrial robot; determining (S602) healthy status of the joint based on the calculated accumulative damage; indicating (S603) the healthy status of the joint. With calculation of accumulative damage to a joint, healthy status of the joint can be determined based on the accumulative damage, rest life can be predicted for operator's replacement preparation and also be a caution in case of large accumulative damage to the joint.

Description

Method and apparatus for robot joint status monitoring

Technical Field

The present invention relates to techniques of robot status monitoring, and more particularly to a method, apparatus and computer-readable storage medium for robot joint status monitoring.

Background Art

As shown in FIG. 1, an industrial robot 100 can include a controller 10 and a manipulator 20. The controller 10 is for controlling motions of the manipulator 10.

The manipulator 20 may have several arms 201 which are connected by at least one joint 202. Usually in each joint 202, there is a control board 203 and variety of sensors, such as temperature sensor, vibration sensor, etc. The control board 203 is connected with the controller 10, collecting sensor data and encoding controlling command from the controller 10.

Because of high-speed working requirements, joints are the most vulnerable parts in a manipulator and not easy to be found by a field operator (most of time, joints can still move, but precision or performance gets worse) .

FIG. 2 shows a current robot which has an indicator on top of the terminal joint back. However, the indicator is just for detecting the robot’s basic status/mode such as running, programming and error.

Summary of the Invention

Considering that each joint has a life cycle. From large amount of research work, it is found that a joint’s life depends mostly on accumulative damage. Broken joints will badly influence performance of a manipulator, so how to get information of left life of a joint and make necessary preparation of replacement will be crucial for production line’s normal working with a robot. In the present disclosure, accumulative damage of a joint will be calculated and based on which healthy status of a joint will be shown to operators.

According to a first aspect of the present disclosure, a method for robot joint status monitoring is presented. The method includes following steps:

- calculating accumulative damage to a joint of a manipulator of an industrial robot;

- determining healthy status of the joint based on the calculated accumulative damage;

- indicating the healthy status of the joint.

According to a second aspect of the present disclosure, an apparatus for robot joint status monitoring is presented, which include modules configured to execute each step of the method according to the first aspect.

According to a third aspect of the present disclosure, an apparatus for robot joint status monitoring is presented, which includes at least one processor, and at least one memory, coupled to the at least one processor, configured to execute method according to the method according to the first aspect.

According to a fourth aspect of the present disclosure, a computer-readable medium for robot joint status monitoring is presented, which stores computer-executable instructions, wherein the computer-executable instructions when executed cause at least one processor to execute method according to the first aspect.

With the calculation of accumulative damage to a joint, healthy status of the joint can be determined based on the accumulative damage, rest life can be predicted for operator’s replacement preparation and also be a caution in case of large accumulative damage to the joint.

Optionally, when calculating accumulative damage, at least one item of following data of the joint: temperature, torque and speed can be collected, unit accumulative damage to the joint cab be calculated according to the collected data, and accumulative damage to the joint can be calculated according to the unit accumulative damage.

Temperature, torque and speed are most important factors which can influence joint’s accumulative damage, data of the above three items can be collected timely and based on which accurate value of damage can be calculated.

Optionally, when calculating unit accumulative damage to the joint according to the collected data, a first unit accumulative damage to the flexible bearing inside the joint can be calculated, a second unit accumulative damage to the flexible gear inside the joint can be also calculated; then the larger one of the first unit accumulative damage and the second unit accumulative damage can be taken as the unit accumulative damage to the joint.

Considering that the flexible bearing and the flexible gear are the main parts of a joint, the accumulative damage of the joint can be calculated based on the larger one of them.

Optionally, when determining healthy status of the joint based on the calculated accumulative damage, comparing the calculated accumulative damage with at least one predefined threshold of accumulative damage and determining healthy status of the joint based on the comparison result.

So, the healthy status can be differentiated corresponding to different predefined thresholds.

Optionally, before calculating accumulative damage to a joint of a manipulator of an industrial robot, working time of the joint can be determined, if the working time of the joint is longer than predefined time threshold, then at least one item of following data: vibration of the joint, temperature increase of the joint and change of transmission characteristics of the joint can be acquired, and healthy status of the joint can be determined based on the acquired item of data, then the healthy status of the joint can be indicated.

Working time of the joint is over predefined time threshold may mean that the accumulative damage ot the joint is quite large, in such a case, from external presentation, the vibration, the temperature increase and change of transmission characteristics of the joint can provide an easier and more apparent way for detecting the joint’s healthy status.

Optionally, the healthy status of the joint can be indicated via lamp on the joint, wherein different colors display different healthy statuses of the joint, which provides an intuitive way for operators’ observation.

Brief Description of the Drawings

The above mentioned attributes and other features and advantages of the present technique and the manner of attaining them will become more apparent and the present technique itself will be better understood by reference to the following description of embodiments of the present technique taken in conjunction with the accompanying drawings, wherein:

FIG. 1 depicts a block diagram of an industrial robot.

FIG. 2 depicts a current industrial robot with an indicator on top of the terminal joint back.

FIG. 3 depicts an industrial robot with joint status monitoring in accordance with one embodiment of the present disclosure.

FIG. 4 depicts a controller of an industrial robot in accordance with one embodiment of the present disclosure.

FIG. 5 depicts a control board inside a joint of manipulator of an industrial robot in accordance with one embodiment of the present disclosure.

FIG. 6 depicts flow diagrams of a method for robot joint status monitoring in accordance with one embodiment of the present disclosure.

Reference Numbers:

100, an industrial robot

10, controller of the robot 100

20, manipulator of the robot 100

201, arms of the manipulator 20

202, joints of the manipulator 20 connecting the arms 201

203, control board corresponding to joint 201

204A, thermal sensor inside joint 201

204B, torque sensor inside joint 201 and/or encoder which can measure motor’s speed

204C, vibration sensor inside joint 201

205, lamp on joint 201 displaying healthy status of joint 201

101, at least one memory

102, at least one processor

103, I/O port

104, Graphic Processing Unit (GPU)

105, communication module

301, mouse

302, keyboard

40, monitor

50, a robot joint status monitoring program

60, sensor data

501～503, modules configured to execute robot joint status monitoring method 600

2031, at least one memory

2032, at least one processor

2033, 2034 I/O port

57, a robot joint status monitoring program

80, sensor data

600, a method for robot joint status monitoring

S601～S614, steps of method 600

Detailed Description of Example Embodiments

Hereinafter, above-mentioned and other features of the present technique are described in detail. Various embodiments are described with reference to the drawing, where like reference numerals are used to refer to like elements throughout. In the following description, for purpose of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more embodiments. It may be noted that the illustrated embodiments are intended to explain, and not to limit the invention. It may be evident that such embodiments may be practiced without these specific details.

When introducing elements of various embodiments of the present disclosure, the articles “a” , “an” , “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising” , “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.

Now the present disclosure will be described hereinafter in details by referring to FIG. 3 to FIG. 6.

FIG. 3 depicts an industrial robot with function of displaying healthy status of joints presented in the present disclosure. As shown in FIG. 3, the healthy status can be displayed via lamps 205 on joints 202. Optionally, one lamp 205 corresponds to one joint 202. Different colors can display different healthy statuses of the joint. For example, lamp 205 in light blue can display healthy running status, lamp 205 in orange can display overloaded running status, and lamp 205 in red can display damaged status. Other colors can be displayed to show that the amount of accumulative damage to a joint 202. Sounds can be also used for indicating healthy status of joints 202. Different waves of sounds correspond to different healthy status.

Accumulative damage calculating, healthy status determination and indication can be implemented via controller 10 (following embodiment 1) or via control boards 203 (following embodiment 2) . Control boards 203 are connected with sensors, such as thermal sensor 204A, torque sensor and/or encoder which can measure motor’s speed 204B and vibration sensor 204C. Control boards collect sensor data from sensors, then control boards 203 execute accumulative damage calculation and healthy status determination, or control boards 203 send the sensor data to controller 10 for accumulative damage calculation and healthy status determination. Now embodiment 1 and embodiment2 will be described in detail referring FIG. 4 and FIG. 5

Embodiment 1

healthy status determination and indication implemented via controller 10

Now referring to FIG. 4, controller 10 is connected to a control board 203 corresponding to a joint 202 (preferably inside the joint 202) , the control board 203 collects sensor data from

sensors

204A, 204B and 204C, and optionally from other sensors, and sends to controller 10. Controller 10 receives sensor data via communication module 105 from the control board 203, then the sensor data 60 can be stored in at least one memory 101 for further processing, such as accumulative damage calculation and healthy status determination. Commands indicating healthy status of the joint 202 will be sent via the communication module 105 to the control board 203, then based on the command, the control board 203 will control indicating the healthy status, such as controlling color of the lamp mounted on the joint 202. All the processing can be controlled by the at least one processor 102, which execute computer-executable instructions prestored in the at least one memory 101. Optionally, the computer-executable instructions can compose a robot joint status monitoring program 50. Optionally, controller 10 can be connected other control board 203 for monitoring other joints healthy status.

The at least one memory 101, which includes computer-readable medium, such as a random access memory (RAM) . The at least one processor 102, coupled with the at least one memory 101. The at least one processor 102 may include a microprocessor, an application specific integrated circuit (ASIC) , a digital signal processor (DSP) , a central processing unit (CPU) , a graphics processing unit (GPU) , state machines, etc. embodiments of computer-readable medium include, but not limited to a floppy disk, CD-ROM, magnetic disk, memory chip, ROM, RAM, an ASIC, a configured processor, all optical media, all magnetic tape or other magnetic media, or any other medium from which a computer processor can read instructions. Also, various other forms of computer-readable medium may transmit or carry instructions to a computer, including a router, private or public network, or other transmission device or channel, both wired and wireless. The instructions may include code from any computer-programming language, including, for example, C, C++, C#, Visual Basic, Java, and JavaScript.

Users can set parameters such as thresholds to be used in the robot joint status monitoring program 50 via an input device, such as a mouse 301 and/or a keyboard 302, can be received via an I/O port 103. And programming user interfaces, such as can be displayed via a GPU 104 on an output device 40.

The robot joint status monitoring program 50 can include:

- a calculation module 501, configured to calculate accumulative damage to a joint 202 of a manipulator 20 of an industrial robot 100;

- a determination module 502, configured to determine healthy status of the joint 202 based on the calculated accumulative damage;

- a indicating module 503, configured to indicate the healthy status of the joint 202.

Details of the implementation of the modules will be described in processing procedure shown in FIG. 6.

Embodiment 2

healthy status determination and indication implemented via control board 203

Now referring to FIG. 5, control board 203 collects sensor data via I/O port 2034 from

sensors

204A, 204B and 204C, and optionally from other sensors, then the sensor data 80 can be stored in at least one memory 2031 for further processing, such as accumulative damage calculation and healthy status determination. Optionally, commands indicating healthy status of the joint 202 will be sent via I/O port 2033 to a lamp 205 mounted on the joint 202. All the processing can be controlled by the at least one processor 2032, which execute computer-executable instructions prestored in the at least one memory 2031. Optionally, the computer-executable instructions can compose a robot joint status monitoring program 70.

The at least one memory 2031 can include computer-readable medium, such as a random access memory (RAM) . The at least one processor 2032, coupled with the at least one memory 2031. The at least one processor 2032 may include a microprocessor, an application specific integrated circuit (ASIC) , a digital signal processor (DSP) , a central processing unit (CPU) , a graphics processing unit (GPU) , state machines, etc. embodiments of computer-readable medium include, but not limited to a floppy disk, CD-ROM, magnetic disk, memory chip, ROM, RAM, an ASIC, a configured processor, all optical media, all magnetic tape or other magnetic media, or any other medium from which a computer processor can read instructions. Also, various other forms of computer-readable medium may transmit or carry instructions to a computer, including a router, private or public network, or other transmission device or channel, both wired and wireless. The instructions may include code from any computer-programming language, including, for example, C, C++, C#, Visual Basic, Java, and JavaScript.

The robot joint status monitoring program 70 can include:

- a calculation module 701, configured to calculate accumulative damage to a joint 202 of a manipulator 20 of an industrial robot 2030;

- a determination module 702, configured to determine healthy status of the joint 202 based on the calculated accumulative damage;

- a indicating module 703, configured to indicate the healthy status of the joint 202.

Details of the implementation of the modules will be described in processing procedure shown in FIG. 6. Although the above-mentioned calculation modules, determination modules and indicating modules are described above as software modules of the robot joint status monitoring programs. Also, they can be implemented via hardware, such as ASIC chips. They can be integrated into one chip, or separately implemented and electrically connected.

It should be mentioned that the present disclosure may include apparatuses having different architecture than shown in FIG. 4 and FIG. 5. The architecture above is merely exemplary and used to explain the exemplary method 600 shown in FIG. 6.

Various methods in accordance with the present disclosure may be carried out. One exemplary method 600 according to the present disclosure includes steps S601 to S614:

- S611: determining working time of the joint; if the working time of the joint is longer than predefined time threshold, then executing step S612～S614, otherwise, executing step S601～S603. Working time of the joint is over predefined time threshold may mean that the accumulative damage ot the joint is quite large, in such a case, from external presentation, the vibration, the temperature increase and change of transmission characteristics of the joint can provide an easier and more apparent way for detecting the joint’s healthy status.

- S612: acquiring at least one item of following data: vibration of the joint, temperature increase of the joint and change of transmission characteristics of the joint; the above data can be sensor data acquired from

sensors

204A, 204B, 204C, etc.

- S613: determining healthy status of the joint based on the acquired item of data; thresholds can be predefined for determination of the healthy status for vibration, temperature increase and change of transmission characteristics.

- S614: indicating the healthy status of the joint.

- S601: calculating accumulative damage to a joint of a manipulator of an industrial robot. Optionally, the step S601 may include following sub steps:

- S6011: collecting at least one item of following data of the joint: temperature, torque and speed. Optionally the data are sensor data collected from

sensors

204A, 204B, 204C, etc.

- S6012: calculating unit accumulative damage to the joint according to the collected data. Optionally, the step S6012 may include sub steps S6012a to S6012C.

For flexible bearing and flexible gear are two major parts which can be broken and influence mostly performance of the joint, so the accumulative damage to them can be calculated and taken as the accumulative damage to joint.

- S6012a: calculating a first unit accumulative damage to the flexible bearing inside the joint.

In sub step S6012a, firstly, the operating life of a flexible bearing Lhcan be calculated with following equations 1 to4:

Values for Ln can be referred to following table, Wherein,

calculated according to following equation 2:

The average output speed can be calculated according to following equation 3:

The average input speed can be calculated according to following equation 4:

n _iv av=i·n _out av … (4)

In above equations speed and torque are considered for calculation of operating life of a flexible bearing. However, temperature may also make influences.

Then, The operating life taking into account of temperature coefficient L _ht can be calculated according to following equation 5:

L _ht=L _h* (f _T) ³ … (5)

wherein, f _T is temperature coefficient.

Next, unit accumulative damage D _i during time period t _i can be calculated according to following equation 6:

D _i=t _i/L _hti… (6)

Wherein, ti is the time period for calculation unit accumulative damage, for example 5 minutes; L _hti is the operating life taking into account of temperature coefficient during the time period t _i.

-S6012b: calculating a second unit accumulative damage to the flexible gear inside the joint.

Firstly, N, maximum allowable impact times during one time impact load can be calculated according to following equation 7:

N= (1.0*10 ⁴) / (2*n*t/60) … (7)

Wherein, t is the impact torque executing time, n is the speed of wave generator.

Then, accumulative damage during one time impact load can be calculated according to following equation 8:

D _i=1/N _i … (8)

Wherein, D _i is the unit accumulative damage during the i _th time impact load, Ni is the maximum allowable impact times during the i _th time impact load .

- S6012c: taking the larger one of the first unit accumulative damage (calculated in sub step S6012a) and the second unit accumulative damage (calculated in sub step S6012b) as the unit accumulative damage to the joint.

- S6013: calculating accumulative damage to the joint according to the unit accumulative damage.

- S602: determining healthy status of the joint based on the calculated accumulative damage;

Optionally, the step S602 determining healthy status of the joint based on the calculated accumulative damage includes:

- S6021: comparing the calculated accumulative damage with at least one predefined threshold of accumulative damage;

- S6022: determining healthy status of the joint based on the comparison result.

- S603: indicating the healthy status of the joint.

Optionally, when in steps S603 and S614, displaying the healthy status of the joint, indicating via lamp on the joint, wherein different colors display different healthy statuses of the joint.

A computer-readable medium is also provided in the present disclosure, storing computer-executable instructions, which upon execution by a computer, enables the computer to execute any of the methods presented in this disclosure.

A computer program, which is being executed by at least one processor and performs any of the methods presented in this disclosure.

A robot joint status monitoring enhancement solution is provided in the present disclosure, with temperature vibration, torque, speed and other data are monitored for calculation accumulative damage to a joint, the healthy status of the joint can be indicated in an intuitive way for operators’ reference.

Normally robot is suggested to be used under typical average power, which is much less than max design power, if a robot continuously works at design power, temperature of joints will exceed the limit. High temperature may lead to malfunction or even damage of electrical parts like PCB and sensors. From mechanical side, firstly high load can directly damage the gear and make brake failure; secondly continuous high load increases inside temperature of joints, influence performance of gear, cause lubrication problem of gear and bears by reducing viscosity of grease.

The healthy status indication provides an intuitive way for programmer’s safety motion plan in robot commissioning period. During operation, the light helps operators to find shutting off point ahead of failure and show them which joint is in most critical status.

While the present technique has been described in detail with reference to certain embodiments, it should be appreciated that the present technique is not limited to those precise embodiments. Rather, in view of the present disclosure which describes exemplary modes for practicing the invention, many modifications and variations would present themselves, to those skilled in the art without departing from the scope and spirit of this invention. The scope of the invention is, therefore, indicated by the following claims rather than by the foregoing description. All changes, modifications, and variations coming within the meaning and range of equivalency of the claims are to be considered within their scope.

Claims

A method (600) for robot joint status monitoring, comprising:

- calculating (S601) accumulative damage to a joint of a manipulator of an industrial robot;

- determining (S602) healthy status of the joint based on the calculated accumulative damage;

- indicating (S603) the healthy status of the joint.
the method according to claim 1, wherein calculating (S601) accumulative damage to a joint of a manipulator of an industrial robot comprises:

- collecting (S6011) at least one item of following data of the joint: temperature, torque and speed;

- calculating (S6012) unit accumulative damage to the joint according to the collected data;

- calculating (S6013) accumulative damage to the joint according to the unit accumulative damage.
the method according to claim 2, wherein calculating (S6012) unit accumulative damage to the joint according to the collected data comprises:

- calculating (S6012a) a first unit accumulative damage to the flexible bearing inside the joint;

- calculating (S6012b) a second unit accumulative damage to the flexible gear inside the joint;

- taking (S6012c) the larger one of the first unit accumulative damage and the second unit accumulative damage as the unit accumulative damage to the joint.
the method according to claim 1, wherein

- determining (S602) healthy status of the joint based on the calculated accumulative damage comprises:

- comparing (S6021) the calculated accumulative damage with at least one predefined threshold of accumulative damage;

- determining (S6022) healthy status of the joint based on the comparison result.
the method according to claim 1, before calculating (S601) accumulative damage to a joint of a manipulator of an industrial robot, further comprising:

- determining (S611) working time of the joint;

- if the working time of the joint is longer than predefined time threshold, then

- acquiring (S612) at least one item of following data: vibration of the joint, temperature increase of the joint and change of transmission characteristics of the joint;

- determining (S613) healthy status of the joint based on the acquired item of data;

- indicating (S614) the healthy status of the joint.
the method according to claim 1 or 5, wherein displaying (S603, S614) the healthy status of the joint comprises:

- indicating (S603, S614) via lamp on the joint, wherein different colors display different healthy statuses of the joint.
An apparatus (10, 203) for robot joint status monitoring, comprising modules configured to execute each step of the method (600) according to any of the claims 1 to 6.
An apparatus (10, 203) for robot joint status monitoring, comprising:

- at least one processor;

- at least one memory, coupled to the at least one processor, configured to execute method according to any of the claims 1 to 6.
A computer-readable medium for robot joint status monitoring, storing computer-executable instructions, wherein the computer-executable instructions when executed cause at least one processor to execute method according to any of the claims 1 to 6.