WO2024145853A1

WO2024145853A1 - Failure indicator for plastic structural member of industrial robot

Info

Publication number: WO2024145853A1
Application number: PCT/CN2023/070563
Authority: WO
Inventors: Wei Song; Jiafan ZHANG; Kaiyuan CAO
Original assignee: ABB Schweiz AG
Current assignee: ABB Schweiz AG
Priority date: 2023-01-04
Filing date: 2023-01-04
Publication date: 2024-07-11
Anticipated expiration: 2025-07-04

Abstract

Embodiments of present disclosure relate to a failure indicator for a plastic structural member (110) of an industrial robot. The failure indicator comprises a body (210) adapted to be fixed to the plastic structural member (110); and a weakened portion (220) provided on the body (210) and having a weaker strength than the body (210). With provision of the weakened portion, the breakage of the weakened portion can be used to indicate an early failure or a potential failure of the plastic structural member in the industrial robot.

Description

FAILURE INDICATOR FOR PLASTIC STRUCTURAL MEMBER OF INDUSTRIAL ROBOT

FIELD

Embodiments of the present disclosure generally relate to an industrial robot comprising plastic structural members, and more particularly to a failure indicator for detecting a failure in the plastic structural members.

BACKGROUND

There are increasing demands in industrial robots for industrial applications, such as, food, beverage, medical and hygiene industries, and the like. Plastic structural members are more and more used in the industrial robot due to its plurality of advantages, such as no requirement of painting, no additional machining for the parts, and low cost for massive production. But these plastic structural members are also subject to some drawbacks, such as lower stiffness, aging effects of fatigue, and the like. These failures should be detected as early as possible since continuous use of the plastic structural members with failures may cause disastrous consequences. Thus, there is a need to detect these failures in the plastic structural members as early as possible.

SUMMARY

Example embodiments of the present disclosure provide a failure indicator for a plastic structural member of an industrial robot which can detect the failures, in particular, in their initial phase, or potential failures ahead of its real happening, in the plastic structural members.

In a first aspect of the present disclosure, it is provided a failure indicator for a plastic structural member of an industrial robot. The failure indicator comprises: a body adapted to be fixed to the plastic structural member; and a weakened portion provided on the body and having a weaker strength than the body. With provision of the weakened portion, the weakened portion having a weaker strength is configured to break earlier than the body. Thus, the breakage of the weakened portion can be used to indicate an early failure or a potential failure of the plastic structural member.

In some embodiments, the body and the weakened portion may form a part of a circuit, and the weakened portion may be configured to increase, in response to being broken, a resistance of the part of the circuit, or disconnect the circuit. With this arrangement, by forming an electrical circuit, the breakage of the weakened portion can be easily detected.

In some embodiments, the body and the weakened portion are formed of a metal material. With this arrangement, the metal material has better load distribution performances than a plastic material and the lifetime of the weakened portion during operations of the failure indicator thus can be precisely predicated.

In some embodiments, the failure indicator may further comprise an electrical conductor provided in the body and the weakened portion and configured to disconnect the circuit in response to breakage of the weakened portion, the body and the weakened portion being formed of a plastic material. With this arrangement, when the body and the weakened portion are formed of a plastic material, an electrical circuit can be easily formed.

In some embodiments, the failure indicator may further comprise an alarm device provided in the circuit and configured to issue an alarm, in response to disconnection of the circuit or the resistance exceeding a predetermined threshold. With this arrangement, an alarm can be automatically issued once a breakage of the weakened portion is detected. In some embodiments, the failure indicator may further comprise an indicator light, a buzzer or a combination thereof.

In some embodiments, the body is an elongated member and comprises at least a first portion and a second portion, and the weakened portion is arranged between the first portion and the second portion.

In some embodiments, the body is fixed to the plastic structural member by a screw, adhesion, welding, fusion, or insert molding. With this arrangement, the body can be attached to the plastic structural member.

In some embodiments, the body comprises a mounting hole adapted to receive a screw assembly, and the body is configured to be fastened to the plastic structural member by the screw assembly.

In some embodiments, the screw assembly may comprise: a spacing sleeve (216) arranged in the mounting hole; a screw extending through the spacing sleeve; and an insertion block adapted to be disposed in the plastic structural member and configured to threadly engage with the screw.

In a first aspect of the present disclosure, it is provided an industrial robot. The industrial robot comprises: a plastic structural member; and one or more failure indicators according to the first aspect fixed to the plastic structural member.

In some embodiments, the body and the weakening portion may be configured to bear a load applied to the plastic structural member when the industrial robot operates.

In some embodiments, the load may comprise at least one of a compressive force, a tensile force, a shear force, a bending force, and a torsional force.

In some embodiments, the plastic structural member may comprise a fiber reinforced plastic material.

DESCRIPTION OF DRAWINGS

Through the following detailed descriptions with reference to the accompanying drawings, the above and other objectives, features and advantages of the example embodiments disclosed herein will become more comprehensible. In the drawings, several example embodiments disclosed herein will be illustrated in an example and in a non-limiting manner, wherein:

Fig. 1 is a schematic overall perspective view of an industrial robot including a failure indicator according to one example embodiment of the present disclosure;

Fig. 2 is a perspective view of a failure indicator according to one example embodiment of the present disclosure;

Fig. 3 is a perspective view of a failure indicator according to another example embodiment of the present disclosure;

Fig. 4 is a section view showing how the failure indicator is attached to the plastic structural member via a screw assembly according to one example embodiment of the present disclosure;

Fig. 5 is a schematic view of showing two failure indicators configured to detect a torsion of a plastic shaft according to one example embodiment of the present disclosure.

Fig. 6 is a schematic view of showing a failure indicator configured to detect a force of a plastic beam according to one example embodiment of the present disclosure; and

Fig. 7 is a schematic view of an alarm device according to one example embodiment of the present disclosure.

Throughout the drawings, the same or similar reference symbols are used to indicate the same or similar elements.

DETAILED DESCRIPTION OF EMBODIMENTS

Principles of the present disclosure will now be described with reference to several example embodiments shown in the drawings. Though example embodiments of the present disclosure are illustrated in the drawings, it is to be understood that the embodiments are described only to facilitate those skilled in the art in better understanding and thereby achieving the present disclosure, rather than to limit the scope of the disclosure in any manner.

The term “comprises” or “includes” and its variants are to be read as open terms that mean “includes, but is not limited to. ” The term “or” is to be read as “and/or” unless the context clearly indicates otherwise. The term “based on” is to be read as “based at least in part on. ” The term “being operable to” is to mean a function, an action, a motion or a state that can be achieved by an operation induced by a user or an external mechanism. The term “one embodiment” and “an embodiment” are to be read as “at least one embodiment. ” The term “another embodiment” is to be read as “at least one other embodiment. ” The terms “first, ” “second, ” and the like may refer to different or same objects. Other definitions, explicit and implicit, may be included below. A definition of a term is consistent throughout the description unless the context clearly indicates otherwise.

Fig. 1 is a schematic overall perspective view of an industrial robot 100. The industrial robot 100 comprises robotic arms (also referred as manipulator) configured to handle various workpieces or objects in an industrial field. The robotic arms comprise a plurality of structural members 110, such as arms and joints including shafts. These structural members 110 are subject to various loads, such as a compressive force, a tensile force, a shear force, a bending force, a torsional force, and the like, during operations of the industrial robot 100. Due to a plurality of advantages, such as lower costs, plastic structural members are more and more used to form the structural members of the industrial robot 100. The plastic materials, for example, include fiber-reinforced plastic materials (such as Nylon, PPS, or PEEK) . However, the plastic materials are low-strength materials compared to metal materials, and the failure always happens in a shorter time. To improve safety of plastic robot structural members, early failure detection or prediction solution may be needed.

It is, however, normally difficult to predict precise lifetime of the plastic structural members. The plastic structural members are subject to various failure types and surfaces of plastic structural members may appear stress whitening, crazing, crack, and so on. Thus, one conventional method for detecting failures of the plastic structural members is to monitor a surface feature of the plastic members. But this solution needs a camera which should be placed to a proper position which can visibly detect the whole surface of the plastic structural members. This solution is costly and is not satisfying. Another conventional method for detecting failures of the plastic structural members is use of a sensor such as strain gauge which may appear an abrupt change of strain value in case of a crack happens. However, failure positions in the plastic structure are generally hard to predict. For example, some failures, such as a crack, in the plastic structure may start from a corner or a side of the plastic structure which are generally hard to arrange the sensors. This solution is not satisfying either. According to the present disclosure, a failure indicator 200 is provided which can easily and reliably detect an early failure in the plastic structural member 110 of the industrial robot.

As shown in Fig. 1, the failure indicator 200 comprises a body 210 adapted to be fixed to the plastic structural member 110 and a weakened portion 220. Since the body 210 is fixed to the plastic structural member 110, the body 210 experiences substantially the same loads as the plastic structural member 110 during operations of the industrial robot 100. The weakened portion 220 is provided at a proper position on the body 210 and has a weaker strength than the body 210. The weakened portion 220 is configured to break earlier than the body 210 during operation of the industrial robot. The weakened portion 220 is designed with predetermined lifetime. The life time can be determined, for example, based on the material property of the plastic structural member using finite element analysis. For example, the life time of the plastic structural member used for the industrial robot can be known in advance, for example, by calculation or simulation. The weakened portion can be designed in accordance with life time of the plastic structural member such that the weakened portion can break earlier than a failure occurs in the plastic structural member. Thus, the breakage of the weakened portion can be used to indicate an early failure or a potential failure of the plastic structural member 110 before the plastic structural member 110 really fails during operations of the industrial robot.

The failure indicator 200 may be of various forms as long as the body 210 of the failure indicator 200 can be reliably attached to the critical positions of the plastic structural member 110 and undergoes the same loads as the plastic structural member 110, such as tension, compression, bending, shearing and torsion loads. In the shown example, the weakened portion 220 is formed by material removal. It is to be understood that the weakened portion 220 may be of any other proper forms as long as the weakened portion breaks earlier than the body.

With provision of the failure indicator, the weakened portion 220 breaks earlier than or at the same time as a real failure occurs in the industrial robot. Thus, the failure indicator can be used to predict a failure of the plastic structural member. It provides a good indicator for the real robot structure failure.

Figs. 2 and 3 show exemplary forms of the failure indicator according to one example embodiment of the present disclosure. As shown in Figs. 2 and 3, the failure indicator 200 is of an elongated member, for example, a sheet shape, and includes a large area to contact the plastic structural member 110. The body 210 comprises a first portion and a second portion. The first portion and the second portion can be used as load bearing portions to undergo the loads exerted thereon. The first portion and the second portion can also be used as fixing portions of attaching the body to the plastic structural member 110. The weakened portion 220 is arranged between the first portion and the second portion and connects the first portion and the second portion. In the shown example, the weakened portion 220 is centrally located in the body 210. It is to be understood that there is merely illustrative and the weakened portion 220 may be located at any other proper positions as long as the weakened portion 220 can break earlier than the body 210 during operation of the industrial robot. In the shown example, the body 210 comprises two portions for connections. It is to be understood that the body 210 may comprise more than two portions for connections and the shapes and the arrangement of the fixing portions may be of any other forms.

In Fig. 2, the first portion and the second portion are arranged along the line. This configuration is advantageous in detecting loads such as tension, compression, bending, shearing and torsion loads. In Fig. 3, the first portion and the second portion are arranged at an angle, such as 90 degrees. This configuration is advantageous in detecting loads such as bending, shearing and torsion loads.

It is to be understood that the failure indicator 200 is shown to be of an elongated member. This is merely illustrative and the failure indicator 200 may be any other proper shapes as long as the loads that undergoes by the plastic structural member 110 can be transmitted to the body 210. The first portion and the second portion may be formed as any proper shapes as long as the body can readily absorb loads applied on the plastic structural member 110.

The failure indicator 200 may be attached to the plastic structural member 110 via various means. In some embodiments, the failure indicator 200 may be formed as separate component from the plastic structural member 110. The failure indicator 200, for example, can be produced in advance and are attached to different plastic structural members 110 at a later stage. The failure indicator 200 may be fixed to an external surface of the plastic structural members 110 via various means such as adhesive, a screw, welding, thermal fusion and the like. In some embodiments, as shown in Figs. 2 and 3, the body 210 may comprise a mounting hole 212 for fixing. The mounting hole 212 is adapted to receive a screw assembly. The body 210 can be fastened to the plastic structural member 110 by the screw assembly. In some embodiments, the failure indicator 200 may be embedded in the plastic structural members 110, for example, by insert molding.

In some embodiments, the weakened portion 220 is made of the same material as the body 210. In one example, both the weakened portion 220 and the body 210 are formed of metal. The failure properties of a metal material can be precisely determined compared with a plastic material. Thus, the lifetime of the failure indicator 200 made of metal can be more precisely predicated. In another example, both the weakened portion 220 and the body 210 are formed of plastic material. This is advantageous in terms of being easier to manufacture and with lighter weight. In some embodiments, the weakened portion 220 is made of different material as the body 210. For example, the weakened portion 220 may be made metal while the body 210 is made of plastic material.

According to the present disclosure, after the failure indicator 200 is attached to the plastic structural member 110, the failure indicator 200 undergoes the loads that the plastic structural member 110 undergoes. Due to the fact that the failure indicator 200 bears the same loads as the plastic structural member 110, the weakened portion 220 can detect early failures in the plastic structural member 110. That is, the weakened portion 220 breaks earlier before the plastic structural member 110 fails, such as stress whitening, crazing, crack, and the like. The breakage of the weakened portion 220 of the failure indicator 200 indicates that the plastic structural member 110 fails or is close to a failure. Some counter measures, such as maintenance or replacement of the related parts, should be made. In some embodiments, the breakage of the weakened portion 220 can be visually checked. In some embodiments, the breakage of the weakened portion 220 can be automatically detected by triggering an alarm device.

In some embodiments, the body 210 and the weakened portion 220 form a part of a circuit. When the weakened portion 220 is broken, a resistance of the part of the circuit increases or the circuit is disconnected. The signal that a resistance of the part of the circuit increases or disconnection of the circuit can be used to trigger an alarm device. The part of a circuit can be formed in various means.

In some embodiments, when the body 210 and the weakened portion 220 are made of a metal, the body 210 and the weakened portion 220 can be directly connected to a circuit. In some embodiments, for example, at an early stage of the failure, the weakened portion 220 breaks but is still connected to the body 210. In this event, the resistance of the part of the circuit increases more than a predetermined threshold. The increase of the resistance of the part of the circuit indicates an early failure of the plastic structural member 110. In some embodiments, the weakened portion 220 may be completely disconnected to the body 210. In this event, the circuit can be disconnected when the failure occurs.

In some embodiments, when the body 210 and the weakened portion 220 are made of a plastic material, an electrical conductor, such as a wire or a metal sheet, may be provided in the body 210 and the weakened portion 220. When the weakened portion 220 is broken in case of a failure, the electrical conductor disconnects the circuit.

In some embodiments, the alarm device is provided in the circuit and is configured to issue an alarm when the weakened portion 220 is broken. The alarm device may comprise various forms, such as a visual signal (for example, an indicator light) , an audible signal (for example, a buzzer) . With the alarm device, the engineer can know the conditions of the plastic structural member quickly.

Fig. 4 shows one example showing how the failure indicator 200 is attached to the plastic structural member via a screw assembly according to one example embodiment of the present disclosure. As shown in Fig. 4, the failure indicator 200 may comprise a mounting hole 212 for receiving a screw assembly. The screw assembly 230 may comprise a spacing sleeve 216 and a screw 232 including threads. The spacing sleeve 216 is arranged in the mounting hole 212 and is used to protect the body 210 of the failure indicator 200. The screw 232 includes a head 231 and a stem 233 with threads. The screw 232 is threadly fixed to the plastic structural member 110. With the spacing sleeve 216, the compressive force applied onto the body 210 can be limited. The failure indicator 200 can be sandwiched between the screw 232 and the plastic structural member 110. In this way, the failure indicator 200 can be fixed to the plastic structural member 110 by screws. Since the failure indicator 200 is fixed to the plastic structural member 110, the failure indicator 200 is subject to the same loads applied on the plastic structural member 110 during operation of the industrial robot. Thus, the failure indicator 200 can detect early failure conditions of the plastic structural member 110.

In some embodiments, a washer 234 may be provided. With this arrangement, the force distribution can be improved. Also, an insertion block 238 may be embedded in the plastic structural member 110. The insertion block 238 may be arranged in the plastic structure in advance. The stem 233 of the screw 232 can threadly engage with the plastic structural member 110. In some example, the insertion block may be made of a metal. Also, the strength for fixing the failure indicator 200 can be improved.

One or more failure indicators 200 may be attached to the critical positions of the plastic structural member 110. Fig. 5 is a schematic view of showing two failure indicators 200 configured to detect a torsion load of a plastic shaft 120 according to one example embodiment of the present disclosure. The plastic shaft 120 may be a rotation shaft of a joint. The plastic shaft 120 may be connected to a motor and rotates to adjust the angles of the joint. During movements of the robotic arm, the plastic shaft 120 is subject to a torsion load. As shown in Fig. 5, two failure indicators 200 are circumferentially arranged around the plastic shaft 120 so as to detect the torsion loads at different circumferential positions. In the shown example, the two failure indicators 200 are fixed to the plastic shaft 120 via screws. It is to be understood that this is merely illustrative, and the failure indicators 200 can be fixed to the plastic shaft 120 via other proper means. With the failure indicators 200, the early failure of the plastic shaft 120 can be detected reliably.

Fig. 6 is a schematic view of showing a failure indicator 200 configured to detect a force of a plastic beam 130 according to one example embodiment of the present disclosure. The plastic beam 130 may be a main support beam for bearing the loads. The plastic beam 130 may be subject to a compressive load, a tensile load, a shear load, or a bending load according to the posture of the robotic arm. As shown in Fig. 6, one failure indicator 200 is linearly arranged along the plastic beam 130. In the shown example, the failure indicator 200 is fixed to the plastic beam 130 via adhesion. It is to be understood that this is merely illustrative, and the failure indicator 200 can be fixed to the plastic beam 130 via other proper means. With the failure indicator 200, the early failure of the plastic beam 130 can be detected reliably.

It is to be understood that the plastic shaft 120 and the plastic beam 130 are merely exemplary members of the plastic structural member 110. The plastic structural member 110 may be any other plastic structural member of the industrial robots. It is also to be understood that positions and number of the failure indicator 200 are also merely illustrative, and the failure indicators 200 may be arranged at any other critical positions that is vulnerable to breakage. These critical positions may be determined in advance, for example, by experience or by simulation.

Fig. 7 is a schematic view of an alarm device 300 according to one example embodiment of the present disclosure. As shown in Fig. 7, two input ends are connected to the failure indicator 200. When the weaken portion 220 on the body 210 breaks, the signal of the two inputs ends are used to trigger a buzzer 308. As shown in Fig. 7, the alarm device 300 may comprise a power supply 302 and a buzzer 308. A trigger switch 304 is connected in series with the buzzer 308. A resistance 306 is connected in parallel with the buzzer 308. Where there is no failure, the trigger switch is not triggered. When a failure is detected by the failure indicator 200, the trigger switch is switched on. The buzzer 308 rings. A reset switch 306 may also be provided to reset the buzzer 308.

In the shown example, the alarm device 300 is powered by itself. The whole alarm device 300 along with the failure indicator 200 may be formed as accessories of the industrial robot. It is to be understood that this is merely illustrative, and the alarm device 300 may be formed as any other proper forms as long as the failure signal from the failure indicator 200 can be visually or audibly detected. Instead of use of a buzzer 308, a lighting device may be used. In some examples, the failure signals from the failure indicator 200 can be communicated to a control center of the robot which is further configured to process or display the failure conditions of the plastic structural member. In this case, the failure signal from the failure indicator 200 may be used as a failure signal source. With the alarm device, early failures of the components in the industrial robot can be notified to the user.

Through the teachings provided herein in the above description and relevant drawings, many modifications and other embodiments of the disclosure given herein will be appreciated by those skilled in the art to which the disclosure pertains. Therefore, it is understood that the embodiments of the disclosure are not limited to the specific embodiments of the disclosure, and the modifications and other embodiments are intended to fall within the scope of the disclosure. In addition, while exemplary embodiments have been described in the above description and relevant drawings in the context of some illustrative combinations of components and/or functions, it should be realized that different combinations of components and/or functions can be provided in alternative embodiments without departing from the scope of the disclosure. In this regard, for example, it is anticipated that other combinations of components and/or functions that are different from the above definitely described will also fall within the scope of the disclosure. While specific terms are used herein, they are only used in a general and descriptive sense rather than limiting.

Claims

A failure indicator for a plastic structural member (110) of an industrial robot, comprising:

a body (210) adapted to be fixed to the plastic structural member (110) ; and

a weakened portion (220) provided on the body (210) and having a weaker strength than the body (210) .
The failure indicator according to claim 1, wherein the body (210) and the weakened portion (220) form a part of a circuit, and

the weakened portion (220) is configured to increase, in response to being broken, a resistance of the part of the circuit, or disconnect the circuit.
The failure indicator according to claim 2, wherein the body (210) and the weakened portion (220) are formed of a metal material.
The failure indicator according to claim 2, further comprising an electrical conductor provided in the body (210) and the weakened portion (220) and configured to disconnect the circuit in response to breakage of the weakened portion (220) , the body (210) and the weakened portion (220) being formed of a plastic material.
The failure indicator according to claim 2, further comprising an alarm device provided in the circuit and configured to issue an alarm, in response to disconnection of the circuit or the resistance exceeding a predetermined threshold.
The failure indicator according to claim 5, further comprising an indicator light, a buzzer or a combination thereof.
The failure indicator according to any of the preceding claims, wherein the body (210) is an elongated member and comprises at least a first portion and a second portion, and the weakened portion (220) is arranged between the first portion and the second portion.
The failure indicator according to any of the preceding claims, wherein the body (210) is fixed to the plastic structural member (110) by a screw, adhesion, welding, fusion, or insert molding.
The failure indicator according to any of the preceding claims, wherein the body (210) comprises a mounting hole (212) adapted to receive a screw assembly, and the body (210) is configured to be fastened to the plastic structural member (110) by the screw assembly.
The failure indicator of claim 9, wherein the screw assembly comprises:

a spacing sleeve (216) arranged in the mounting hole (212) ;

a screw (232) extending through the spacing sleeve; and

an insertion block (238) adapted to be disposed in the plastic structural member (110) and configured to threadly engage with the screw (232) .
An industrial robot (100) , comprising:

a plastic structural member (110) ; and

one or more failure indicators according to any one of claims 1 to 10 fixed to the plastic structural member (110) .
The industrial robot according to claim 11, wherein the body (210) and the weakening portion (220) are configured to bear a load applied to the plastic structural member (110) when the industrial robot operates.
The industrial robot of claim 12, wherein the load comprises at least one of a compressive force, a tensile force, a shear force, a bending force, and a torsional force.