EP3213159A1

EP3213159A1 - Method and robot system for using an industrial robot for test jobs

Info

Publication number: EP3213159A1
Application number: EP15787548.5A
Authority: EP
Inventors: Thomas Sturm
Original assignee: KUKA Systems GmbH
Current assignee: KUKA Systems GmbH
Priority date: 2014-10-27
Filing date: 2015-10-27
Publication date: 2017-09-06
Also published as: DE102014221798A1; WO2016066616A1

Abstract

The invention relates to a method and a robot system (1) for verifying the position of components (200, 201, 202, 203, 204) in an assembly process. A multi-shaft articulated-arm robot (100), the shafts (A1-An) of which are preferably equipped with torque sensors for sensing the torques acting on the shafts, is used for approaching various checkpoints (220, 221, 222, 223) on the components, and the measured signals from the torque sensors are compared with expected signals corresponding to the correct positions of the components.

Description

METHOD AND ROBOT SYSTEM FOR USING AN INDUSTRIAL ROBOT FOR TEST TESTING Field of the Invention

The present invention relates to a method and a robot system which is set up to autonomously check the correct arrangement of components before, during and / or after an assembly process, preferably in a production line.

Technical background

Robots, and in particular industrial robots, are used for various work processes in, for example, assembly or production in an industrial environment. An industrial robot is an automatically controlled, freely programmable manipulator that can be programmed in three or more axes. Industrial robots can be used mobile or in a fixed location.

An articulated robot, or articulated robot, is a three-dimensional mobile industrial robot, which is composed of several hinges. Usually, the hinges are connected to arm members, and further, each hinge is characterized by a hinge axis. Typically, articulated arm robots have at least six joints. Equipping with additional joints or axes increases the flexibility of the robot. In addition to swivel joints, linear axes can also be used.

In larger assembly plants, such as in the automotive industry, which consist of manual and / or automatic stations, it is common practice

extensive joining processes the correct placement and setting of

Equipment such as assembly pallets and / or the correct structure of the pre-assembled assemblies with AOI systems (Automatic Optical Inspection) to check. AOI systems operate by means of image processing methods in order to determine errors, in particular assembly errors or setting errors of assembly pallets or preassembled assemblies, in an assembly process. These systems are used in almost all sectors of industrial production of goods, such as in the electronics, automotive, aerospace and related industries. It checks

Camera system constantly and autonomously by means of image recognition the correct placement and adjustment of equipment or the correct structure of the preassembled module (s) and recognizes automatically errors, such as a

Component variant, a component position and / or concern the component presence.

The disadvantage, however, is that for the cameras concealed inspection features can not be checked and detected errors can not be corrected immediately. In addition, AOI systems are relatively expensive.

In the following example of an assembly assembly of a car, the current state of the art will be described. As a rule, different vehicle variants are mounted on an aggregate assembly line. At the beginning of the process assembly pallets are equipped with the various components such as front axle with engine, rear axle, radiator, propeller shaft, exhaust system, etc., partially automatic, semi-automatic and / or manual. Furthermore, any screws or fasteners for attaching the aforementioned modules to the

Body of the vehicle, spent in appropriate receptacles on the assembly pallets. Before the fully pre-assembled assembly pallet leaves the assembly area and is transported to the actual assembly assembly line, the assembly pallet usually passes through a control station.

In the control station, among other things, a target / actual comparison is carried out with AOI systems with regard to component variants, component positions and component presence and, in general, the component arrangement. Similarly, pre-assembled modules can be checked. Depending on the vehicle variant, about 50 features are usually tested. An AOI system, which is suitable for three different

To test vehicle variants requires, for example, about 40 cameras and accordingly represents a high investment. The term components are herein understood all components, elements, assemblies, etc. of the assembly process, such as in particular the product components but also the tool, pallet or

Teaching components.

This relatively high cost is justified because in the case of an unrecognized, incorrectly assembled component in the assembly line disturbances or

Damage (such as damage to the body, destruction of the joining device) may occur. In addition, the removal of such a disturbance in the assembly station can lead to high downtime. Furthermore, with a possible extension of the assembly plant to a

Vehicle variant the installation of additional cameras and a complex

Commissioning to detect the new vehicle type required.

The object of the present invention is to provide a method and a robot system which eliminates or reduces the mentioned disadvantages of the AOI systems. These and other objects, which are mentioned in the present description or can be recognized by the person skilled in the art, are achieved by the method according to claim 1 and the robot system according to claim 12. The scope of the present invention is not limited to the previously described aggregate mounting, but extends to the

Checking the arrangement of components, as well as checking of

essential properties of the components and also on a control of

Assembly area itself.

Detailed description of the invention

The inventive method relates to the review of the arrangement of

Components in an assembly process by means of a multi-axis articulated arm robot whose axes are preferably provided with torque sensors for detecting the torques acting on the axles. Alternatively, the articulated arm robot can also be provided with a force sensor on its tool or its end or Abtriebsflansch. The term component includes within the meaning of the invention in addition to individual parts of several parts existing assemblies. The verification of the arrangement of components relates in particular to the control of the presence of components at the predetermined position for the components, the control of the correct orientation, the control of the absence of components and the verification of the correct component variant. Desweitern can, as explained in more detail later, also force-dependent or torque-dependent component-specific

Properties of the component, such as the tightening torque of screws or the belt tension of belt gears are checked by the method according to the invention. The method according to the invention has at least the following steps:

First, a tactile test tool is provided on the articulated arm robot. In this case, the tactile test tool is preferably attached to the tool flange of the robot. The tactile test tool has at least one feeler finger, the tool center point (Tool Center Point, TCP) on the axis position of

Industrial robot is determinable.

Subsequently, the articulated arm robot moves with the tactile test tool to a predetermined control point of at least one component. The control point of the component is typically characteristic of the correct placement of the component. In the case of checking the provision of screws in one

Screw magazine, for example, the screw head of the screw as

Serve checkpoint. To detect whether the magazine is fitted with screws of correct length, the scanning finger of the test tool is guided to the predetermined desired position of the screw head. When the sensing finger comes in contact with the screw head, a force is applied to the feeler finger, which with a suitable

Force sensor can be detected or monitored. The position of the TCP of the

Touch finger when touching the screw head is finally information about the screw length.

In order to detect a touch of tactile test tool and component, preferably an articulated arm robot is used with torque sensors, wherein the signals of the torque sensors of the axes of the articulated robot are monitored and evaluated by a control device. Alternatively, it is also possible to use the motor currents the drive motors of an industrial robot to draw conclusions about the contact of the test tool with a component. If the tactile finger encounters a resistance, such as the screw head, becomes an event-based

Signal change of the signals of the torque sensors detects which signal change preferably comprises rising or falling edges of the signal. The person skilled in the art understands an event-based signal change as follows: Due to the movements of the links of the articulated arm robot, the moment sensors of the axes for the movement measure typical torque profiles that arise, for example, from the force of gravity acting on the links of the robot. If the signals of one or more sensors deviate from the signal typical for pure motion, then it can be concluded that another force or another moment is acting on the links of the articulated arm robot. Such a force (or torque) can be caused for example by the contact of the tactile test tool with a component. The detection of a force or a moment on

Articulated arm robots that are not affected by the mere movement of the limbs of the

Articulated robot comes from, is referred to as an event. The resulting

Signal change of the torque sensors is therefore event-based.

This event-based signal change is compared in a further method step with a desired signal. Becomes a checkpoint, such as a

Screw head, approached with the tactile test tool, so it is known at which position the control point with correct arrangement of the component is (target position). If the tactile test tool reaches the checkpoint, the event-based signal change should occur at this known position if the component is arranged correctly. The measured signal coincides in this case with the desired signal. If this is not the case, it can be concluded that the component is not arranged correctly. The thus determined actual arrangement of the checked component is detected. The actual arrangement may include not only the actual position, orientation and variant of the component but also information about the absence of components, as will be explained in more detail below with reference to the figures. Preferred embodiments

In the following the invention will be explained in more detail with reference to the illustrated figures. Hereby shows:

Fig. L a Gelenkarmroboter and a mounting pallet with to be tested

Components in a side view;

Figure 2 shows the elements of Figure l in a 90 ⁰ rotated view..;

3 shows a test tool, which is mounted on a hinge of the articulated arm robot, according to an embodiment of the invention.

Figs. 4 A-D various tests of the arrangement and properties of the component by means of the test tool;

5 shows a check of the chain or belt tension of a component; and

Fig. 6 is a test of the variant of a component.

1 shows a robot system 1 comprising a multi-axis articulated-arm robot 100 whose axes are provided with torque sensors for detecting the moments acting on the axles, and which is attached to a frame 300 via a moving unit 310. The articulated arm robot 100 has at least one tactile test tool 110 and is part of a control station of an assembly process of a

automated, semi-automated or manual assembly line.

By way of example, here an assembly pallet 210 is shown on which a component 200 is located, in the illustrated case consisting of a vehicle engine with associated transmission and the front and rear axle of a car. The assembly pallet is moved as part of the assembly process with the components thereon according to specifications of the assembly line. Before the assembly pallet is introduced into the actual assembly line, in the control station, the inventive method for checking the correct arrangement and alignment of the components carried out. Only after passing the test, the mounting pallet 210

Approved.

Fig. 2 shows the elements of Fig. 1 in a 90 ^° rotated view. Of the

Multi-axis articulated arm 100 includes the axes Αι, A2, A3 and A4 (possible other axes are not shown) which is attached to the movement 310. The movement unit 310 is set up to linearly move the articulated-arm robot 100 in order to increase the mechanical range of the articulated-arm robot. The

Track movement can also be adapted to the robot in one

to lead curved track. The mechanical range of the articulated arm robot is determined by the length and mobility of the articulated arm robots and defines the range that can be achieved with the tactile test tool.

The trajectory is according to a preferred embodiment of the invention, a linear moving unit, such as a linearly movable portal. Alternatively, the trajectory may also be a rotational trajectory, such as a carousel. Due to the use of a robot provided with moment sensors, the present invention allows direct human-robot collaboration, i. it is e.g. no safety device like a protective fence necessary. The human-robot collaboration method is a method for

Ensuring safe and at the same time efficient cooperation between worker (human) and robot. The human-robot collaboration (MRK) offers a multitude of advantages compared to purely manual or purely robot-based systems. For example, the accessibility of the control station comprising the robot system 1 is significantly improved for humans. This is another advantage over conventional AOI systems.

In Fig. 2, a reference point 230 is shown for the assembly pallet. This

Reference point is used to determine the position and position of the mounting pallet.

Assembly pallets are all aids in the assembly process, which serve for the transport and / or the admission of components. By approaching the reference point of

Assembly palette with the tactile inspection tool can be a transformer matrix for transforming the assembly pallet coordinate system into a robot-specific Coordinate system can be determined. Thus, the verification of the arrangement of moving components is possible. For example, if parts of a vehicle body are moved by means of a mounting pallet through an assembly line, the reference point 230, which is located on the mounting pallet is the reference point for determining the arrangement of the components on which the subsequent assembly process is based.

Fig. 3 shows a tactile test tool 110 and to be tested components 201, 202 and a control point 220. The component 201 is in the case shown a tool for screwing the component 202. This tool is a two-part tool, the lower part the so-called. Spindle extension indicates, sitting on the upper part of a Schraubernuss. Both parts can, as explained in more detail in Figures 4B and 4D, are checked. The tactile test tool is on

Gelenkarmroboter 100, which in Fig. 3 only by the last member of

Articulated arm robot 100 is shown attached. The test tool 110 has at least one touch finger and / or at least one touch contour, with three touch fingers 111, 112, 113 being shown by way of example in FIG. Moreover, the tactile testing tool 110 has a tactile contour 114, which serves to determine the arrangement of a component, such as the determination of the central axis of a screw, or a bolt. The detailed method of determining a central axis is described below in connection with FIG. 4C. The tactile contour 114 may be a closed contour, such as a ring or an open contour, similar to a fork wrench.

In the embodiment shown, an additional optical sensor 400, which is preferably an optical probe, is attached to the articulated arm robot 100. In the illustrated embodiment, the optical sensor 400 is attached to the tactile test tool 110. Optical buttons according to the invention preferably consist of a light emitter, such as a light-emitting diode or a laser diode, and a light receiver, such as a photosensitive resistor (LDR) or a photodiode. The light receiver evaluates the intensity, the color or the

Term of the light received from the light emitter, wherein the received light is preferably reflected light. If an optical sensor 400 is mounted on the articulated-arm robot 100, then the arrangement of components can also take place outside the mechanical range of the articulated-arm robot by means of the following method steps be checked. For this purpose, a control point for checking the arrangement of at least one component is first approached, wherein the control point does not have to lie on the component. Subsequently, the distance between the optical sensor and the component is measured. A comparison of the measured distance with a nominal distance and an evaluation of the possible deviation provides information about the arrangement of the tested component.

4A shows the case of a first component 201, here a screw receptacle of a tool, to which a second component 202, here a screw, is attached. The second component has a first checkpoint 220, which serves to check the correct screw length. To check whether the screw 202 is mounted with the correct length on the first component 201, the articulated arm robot 100 drives the tactile test tool 110 with the sensing finger 111 on the theoretical (target) screw position and then moves down. If the touch finger 111 reaches the control point 220, an event-based signal change of the signals of the torque sensors is detected. This event-based signal change is used in a further method step, e.g. compared with a desired signal. If the determined arrangement of the screw coincides with the checkpoint 220, then a correct screw length is present. If there are deviations, the misfired screw can be detected.

According to a further embodiment of the invention, a correction tool is provided on the articulated arm robot in order, for example, to populate misfired screws and / or missing screws. Retrofitting and correcting detected faults is not limited to screws, but generally applies to incorrect or missing components. For this purpose, first the deviation from the actual arrangement and desired arrangement of a component is determined. The actual arrangement describes the arrangement measured by the tactile test tool or the optical sensor and the desired arrangement is the correct arrangement of the component. Subsequently, an error to be corrected in the arrangement of the component is determined and the error corrected by means of the correction tool.

The correction tool comprises according to a preferred embodiment of the invention, at least one gripper, which is adapted to missing components to properly position misplaced components, align misaligned components,

correctly mount incorrectly assembled components and / or incorrect components

exchange. Thus, errors can already be eliminated during the checking of the arrangement of components and thus costs and time can be saved.

4B illustrates an application in which the first component 201 is spring-mounted. In order to check the spring force of the mounting of the first component 201, the tactile test tool with the sensing finger 111 on the

Control point 221 moves. Then the feeler finger is moved further and the

Signals of the moment sensors of the axes of the articulated arm robot evaluated. The reaction force acting on the sensing finger 111 can be evaluated via the torque sensors and thus the spring force of the bearing can be checked. Fig. 4C shows the case of checking the position of the first component 201 by means of the tactile contour 114 of the tactile Prüfwerkszeugs. The contact contour 114 in this case has a semicircular floor plan. In order to check the position of the first component 201, the tactile test tool 110 is moved with its contact contour 114 transversely to the spindle axis and the event-based signal change is detected on contact with control point 222. If the Tastkontur 114 then in a second direction transverse to

Spindle axis moves and detects the event-based signal change, so the center axis of the tested component can be determined.

4D shows the case of checking a further force-dependent test feature, namely the checking of the tight fit of the first component 201. For this purpose, the tactile test tool is hooked with an angled test finger 112 under the component to be tested at the checkpoint 223 and with a defined force, which checked by the moment sensors of the axes of the articulated arm robot, pulled upwards. If no event-based signal change, such as a sudden drop in force, detected, it can be concluded that the component is stuck.

5 shows a belt or chain transmission 207, which comprises a tensioning device 206 and a belt 205. Such a belt transmission may for example be mounted on a mounting pallet. To check the belt tension is the tactile test tool 120, which is mounted on the articulated arm 100 and the tactile finger 121 has moved against the belt. Subsequently, the force and / or the moment acting on the tactile test tool are detected.

In addition, a distance measurement can be done. The measured force and / or moment are compared to a desired force and / or torque representative of the desired belt tension. Further, with a suitable correction tool, the tensioning device 206 can be actuated by the articulated arm robot 100 and the belt tension can be adjusted accordingly. Fig. 6 shows the verification of a variant of a component by means of the on

Gelenkarmroboter 100 attached test tool 120, which has a sensing finger 121. The component is shown in two variants. The first variant is identified by the reference numeral 203a and has a checkpoint 224a. The second variant is identified by the reference numeral 203b and has a checkpoint 224b. In order to check whether the existing variant of the component corresponds to the first variant 203a, the tactile test tool 120 is moved with its feeler finger 121 to the control point 224a and an event-based signal change is detected on contact with the component. If the position of the tactile finger 121 coincides with the control point 224a at the time of the detected event-based signal change, it can be assumed that the first variant of the component is present. If, however, an error is detected, it can be determined in the same way by starting the checkpoint 224b whether the second variant 203b is present. The skilled artisan will recognize that by the appropriate choice of test criteria and control points, in addition to the component assembly and component-specific, force-dependent and / or

torque-dependent inspection features and variants of components according to the inventive method can be detected.

The invention includes various modifications of the described

Embodiments, since in particular the robot in the number and design of its axes, and the tactile test tool in its geometric configuration, can vary. The robot can be any number and combination of

have rotational and / or translational axes. Likewise, that can

Test tool can be arbitrarily shaped and is only by the load of the

Articulated robot limited. LIST OF REFERENCE NUMBERS

l: robot system

100: articulated arm robot

110, 120: tactile test tool

111, 112, 113, 121: touch fingers

114: Tastkontur

200, 201, 202, 203a, 203b: components

205: Belts

206: clamping device

207: belt transmission

210: Mounting pallet

220, 221, 222, 223, 224a, 224b: checkpoints

23O: Reference point

3OO: frame

3IO: Track Motion

4OO: optical sensor

Ai, A2, A3, A4: axles

Claims

Claims 1 to 12

Method for checking the arrangement of components (200, 201, 202, 203, 204) in a mounting process by means of a multi-axis articulated arm robot (100), the method comprising the following steps:

a) providing a tactile test tool (110, 120) on the articulated arm robot

(100);

b) approaching a control point (220; 221; 222; 223) of at least one component (200; 201; 202; 203; 204) with the tactile testing tool (110; 120);

c) monitoring the signals of one or more force sensors arranged to detect a force acting on the test tool;

d) detecting an event-based signal change of the signals of step c), which signal change preferably comprises rising or falling edges of the signal;

e) comparing the event-based signal change with a desired signal; and f) based on step e): detecting an actual arrangement of the inspected component (200; 201; 202; 203; 204).

2. The method of claim 1, wherein the axes (Ai - An) of the multi-axis articulated arm robot (100) are provided with torque sensors for detecting the torques acting on the axes, and wherein these torque sensors are used as force sensors in step c).

3. The method of claim 2, wherein the moment sensors are the only ones

Force sensors are with which acting on the test tool forces are detected or monitored.

4. The method according to claim 2, wherein the signals of the torque sensors of the axes of the articulated arm robot depend on a force acting on the tactile test tool and on the tactile test tool ) Acting moment to be monitored, where the force and / or the moment are compared with a desired force and / or a desired moment, and

whereby a component-specific, force-dependent and / or torque-dependent inspection feature is checked.

5. The method according to any one of the preceding claims, wherein the tactile test tool (110; 120) at least one sensing finger (111; 112; 113; 121) and / or at least one Tastkontur (114).

6. The method according to any one of the preceding claims, wherein the

Articulated arm robot (100) an optical sensor (400) is mounted, and the optical sensor is preferably an optical probe, and the method comprises at least the following method steps:

Approaching a checkpoint to check the arrangement of at least one component (200; 201; 202; 203; 204);

Measuring a distance between the optical sensor and a component (200; 201; 202; 203; 204);

Comparing the measured distance with a desired distance;

Evaluation of the measured distance with regard to the arrangement of the component (200; 20i; 202; 203; 204), wherein the component to be tested can also lie outside the mechanical range of the articulated arm robot (100).

7. The method according to any one of the preceding claims, wherein the method further comprises at least the following method steps:

Providing a correction tool on the articulated arm robot (100);

Determination of the deviation between actual arrangement and intended arrangement of a component (200, 201, 202, 203, 204), or a deviation in one

force-dependent and / or torque-dependent test feature;

Detecting an error to be corrected of the arrangement of the component (200; 201; 202; 203; 204) and / or a fault of a force-dependent and / or

torque-dependent test feature;

Correction of the error by means of the correction tool.

8. The method according to any one of the preceding claims, wherein the

Correction tool comprises at least one gripper, and the at least one gripper is adapted to at least one or more of the following steps:

to provide missing components;

Correctly position misplaced components;

align misoriented components;

correctly mount incorrectly assembled components; and or

replace wrong components.

9. The method according to any one of the preceding claims, wherein a

Positioning unit (310) is provided, on which the articulated arm robot (100) is mounted, and which is adapted to the articulated arm robot (100) to move, so as to increase the mechanical range of the articulated arm robot.

10. The method according to any one of the preceding claims, wherein both the articulated arm robot (100) and the moving unit (310) are operated in the human-robot collaboration method and in particular the working area of the robot is not surrounded by a protective device.

A method according to any one of the preceding claims, wherein the method is applied in an assembly process of an automated, semi-automated or manual assembly line to assembly pallets and / or pre-assembled

Check assemblies.

12. robotic system (1), comprising a multi-axis articulated arm robot (100), which is preferably mounted on a moving unit (310), which

Articulated arm robot (100) is provided with at least one tactile test tool (110; 120), wherein the robot system (1) is adapted to carry out a method according to one of claims 1-11.