WO2010060475A1

WO2010060475A1 - Industrial robot

Info

Publication number: WO2010060475A1
Application number: PCT/EP2008/066240
Authority: WO
Inventors: Soenke Kock
Original assignee: Abb Research Ltd.
Priority date: 2008-11-26
Filing date: 2008-11-26
Publication date: 2010-06-03

Abstract

An industrial robot assembly (101 ) and a method for controlling such an industrial robot assembly (101) is provided. The industrial robot comprises at least one movable arm (102). The at least one movable arm (102) has at least seven internal degrees of freedom of motion. The industrial robot assembly (101 ) comprises sensor means (107, 108, 121) for determining the position of a moving object (112) in relation to the industrial robot assembly (101 ). The industrial robot assembly (101 ) when performing operations is arranged to adapt the configuration of said at least one movable arm (102) in response to the determined position of the object (102), when the moving object (112) is within a predetermined first zone (115) surrounding the industrial robot.

Description

INDUSTRIAL ROBOT

Technical field The present invention relates to an industrial robot and to a method for controlling an industrial robot. More specifically the present invention relates to a kinematically redundant industrial robot and a method for controlling such an industrial robot.

Prior art

Industrial robots have been used for many decades to perform different production steps. The industrial robot may be designed in dependence of the task to be performed by the industrial robot. An industrial robot comprises a base and a grip member for gripping objects to be handled by the industrial robot. In order to be able to translate an object in 3 dimensions and to rotate the object around 3 axes of rotation, the industrial robot has to have 6 internal degrees of freedom. Such an industrial robot may be provided in a number of different ways and is well known in the art. One example of such an industrial robot is an industrial robot comprising a jointed arm with a grip member attached to the outer arm by means of a wrist, wherein the wrist provides for rotation of the object around 3 rotational axes and the jointed arm provides for translation of the object in 3 dimensions in a spherical coordinate system. With such a jointed arm industrial robot a given location and orientation of the tool corresponds to a single discrete set of joint angles and an associated discrete arm configuration. Other tools than a grip member may be attached to the industrial robot, such as, e.g., a weld gun, glue dispenser or a polishing tool.

In many cases non-removable obstacles are positioned in the workspace of the industrial robot. This makes it impossible for a jointed arm industrial robot having at least 6 internal degrees of freedom to move an object to an arbitrary position without the arm interfering with the obstacle. Furthermore, the object itself may have such a shape that the object itself makes it impossible for the industrial robot to position the object in an arbitrary position and an arbitrary orientation without the object interfering with the arm.

US patent 5, 155,423 provides a solution to this problem by providing at least one additional joint to the arm, giving the jointed arm at least 7 internal degrees of freedom. The arm described in said US patent makes it possible to reach points in space without interfering with stationary obstacles.

An industrial robot with 7 or more internal degrees of freedom can be controlled to move along a pathm but also to exhibit self-motion, which is a combination of movements of at least one joint, which movement does not affect the position of the tool due to self- cancellation. The industrial robot can be smoothly re-configured without interrupting the operation of the industrial robot.

The solution with the industrial robot having at least 7 internal degrees of freedom may be applied also to other industrial robots than jointed arm industrial robots.

The industrial robot described in the above US patent may avoid static objects. However, in many industries persons or moving objects may move in the vicinity of the industrial robot. There is a risk that the industrial robot may hit the person or moving object. This may be harmful to the person or moving object and may also be harmful to the industrial robot.

Summary of the invention

An object of the present invention is to provide an industrial robot which is arranged to avoid hitting persons or moving objects moving in the vicinity of the industrial robot. Another object of the present invention is to provide an industrial robot which is arranged to avoid hitting persons or moving objects without affecting the operation of the industrial robot.

At least one of these objects is fulfilled with an industrial robot according to claim 1.

Further advantages are achieved with the features of the dependent claims.

A basic idea of the present invention is to provide an industrial robot having at least seven internal degrees of freedom with means for sensing persons or objects in the vicinity of the industrial robot and to control the industrial robot in such a way that the distance between any part of the industrial robot and the person or object in the vicinity of the industrial robot. Such an industrial robot is usually called a kinematically redundant industrial robot.

According to the invention an industrial robot assembly is provided. The industrial robot assembly comprises at least one movable arm with a tool holder on which a grip member may be attached, which tool holder is arranged in a first end of the arm, and a base part arranged to be attached to a base. The industrial robot assembly has at least seven internal degrees of freedom of motion. The industrial robot assembly is characterized in that the industrial robot assembly comprises sensor means for determining the position of a moving object in relation to the industrial robot assembly. The industrial robot assembly, when performing operations, is arranged to adapt the configuration of said at least one movable arm in response to the determined position of the object, when the moving object is within a predetermined first zone surrounding the industrial robot.

With tool holder is meant a part of the object on which a tool or a grip member may be attached. The tool holder may have the form of a plate or similar and does not have to be especially adapted for holding a tool. The industrial robot assembly may be controlled by a control unit which may be a standard computer programmed to control the industrial robot assembly.

With an industrial robot assembly according to the invention the risk of the industrial robot colliding with a moving object is minimized, while the industrial robot may still continue to perform operations. The configuration to which the arm has been reconfigured may be chosen in many different ways.

The industrial robot assembly may be arranged to adapt the configuration of said at least one movable arm in order to maximize the smallest distance between the moving object and the at least one movable arm.

There are a number of different ways of reconfiguring the arm. The movable arm may comprise joints, wherein the industrial robot is arranged to adapt the configuration of said at least one movable arm in order to maximize the distance between at least one of the joints and the moving object.

As an alternative to maximizing the distance between the object and the arm or one of the joints of the arm the industrial robot assembly may be arranged to provide a predetermined minimum distance between the object and the arm or one of the joints of the arm.

The sensor means may comprise at least one camera which is arranged to monitor the area surrounding the industrial robot assembly. The camera may be of any type known to men skilled in the art.

As an alternative or additionally the sensor means may comprise ultrasonic distance sensors. Ultrasonic distance sensor rely on the transmission and detection of ultrasonic pulses to measure the distance to an object. As an alternative or additionally the sensor means may comprise optical distance sensors. The optical distance sensors may be of any type known to men skilled in the art and rely on the transmission and reception of optical pulses to determine the distance from the distance sensor to an object.

The ultrasonic distance sensors and/or the optical sensors may be arranged on the movable arm. With such a placement of the sensors the distance between the arm and the moving object is measured directly. This is in contrast to the case when the ultrasonic distance sensor, the optical sensor and/or the camera are arranged on the side of the industrial robot assembly to monitor the area surrounding the industrial robot assembly. In such a case the industrial robot assembly has to compare the detected position of an object with the current configuration of the arm in order to be able to determine whether there is any need for reconfiguration of the arm.

The industrial robot assembly may be arranged to determine the shape of the moving object, to add a safety zone around the moving object and to consider the object to be the size of the safety zone.

By adding a safety zone around the object the risk of the arm hitting the object is further decreased. Alternatively or additionally, a safety zone may be arranged around the industrial robot arm. This, will increase the safety distance to the object.

The industrial robot assembly may be arranged to stop performing any operations if the movable arm enters the safety zone. When this occurs the industrial robot assembly has already exhausted all possibilities of reconfiguring of the arm to avoid the arm from entering the safety zone.

The industrial robot assembly may be arranged to lower the speed of movement of the industrial robot assembly if the moving object enters a predetermined second zone surrounding the industrial robot assembly. When this occurs the industrial robot assembly has already reconfigured the arm to maximize the distance between the object and the arm or a joint of the arm.

The industrial robot assembly may be arranged to stop performing any operations if the moving object enters a predetermined third zone surrounding the industrial robot assembly. When this occurs the risk of the arm hitting the object is imminent.

The industrial robot assembly may comprise a base to which the base part of the movable arm is attached. The base may be fixed to the floor of an industrial building. Alternatively, the base may be movable. In the latter case the movement of the base adds one internal degree of freedom to the industrial robot assembly.

The movable arm may have six internal degrees of freedom of motion. In this case the arm is arranged on a movable base which adds at least one internal degree of freedom.

The movable arm may alternatively have at least seven internal degrees of freedom of motion. In this case the arm may be attached to a fixed base.

As indicated above the industrial robot may have two or more arms. Each one of them may be controlled as has been described above.

According to a second aspect of the present invention a method of controlling an industrial robot assembly is provided. The robot assembly comprises at least one movable arm with a tool holder on which a grip member may be attached. The tool holder is arranged in a first end of the arm. The robot assembly also comprises a base part arranged to be attached to a base. The robot assembly has at least seven internal degrees of freedom of motion. The method is characterized by the steps of when the industrial robot assembly is performing operations determining the position of a moving object in relation to the industrial robot assembly, and adapting the configuration of said at least one movable arm in response to the determined position of the object, when the moving object is within a predetermined first zone surrounding the industrial robot assembly.

In the following preferred embodiments of the invention will be described with reference to the appended drawings.

Short description of the drawings

Fig 1 shows an industrial robot assembly according to an embodiment of the present invention.

Fig 2 shows schematically the industrial robot and a moving object.

Fig 3 shows schematically the industrial robot assembly with a first zone, a second zone and a third zone surrounding the industrial robot assembly.

Description of preferred embodiments In the following description of preferred embodiments of the invention similar features will be denoted with the same reference numeral in the different figures.

Fig 1 shows an industrial robot assembly according to an embodiment of the present invention. The industrial robot assembly

101 comprises a movable arm 102 with a tool holder 103 on which a grip member 104 may be attached, which tool holder is arranged in a first end of the arm 102, and a base part 105 arranged in a second end of the arm. The base part 105 is attached to a base 106. The tool holder 103 is movable in space and in orientation by configuration of the arm 102. The arm has seven internal degrees of freedom of motion. The degrees of motion are provided by the rotations 1 -7 shown in Fig 1. The industrial robot shown in Fig 1 is provided with sensor means for determining the position of a moving object in relation to the industrial robot assembly. The sensor means comprises a camera 107 which is arranged to monitor the area surrounding the industrial robot assembly 101. The sensor means also comprises ultrasonic distance sensors 108 and optical distance sensors 121 which are arranged on the movable arm 102. In the embodiment shown in Fig 1 the distance sensors are ultrasonic distance sensors. The industrial robot is controlled by a control unit in the form of a computer 113. The arm 102 comprises a number of joints 120, of which the elbow 118 is one. The base 106 may be arranged movable along rails 122.

Fig 2 shows in a view from above the industrial robot assembly 101 of Fig 1 arranged in a working environment. The industrial robot assembly 101 is arranged to handle objects in a first area 109. Due to the seven internal degrees of freedom of the arm 102 the arm may be configured in different configurations for a given position and orientation of the grip member 104. The dotted line 110 shows the arm 102 in a first position during operation. A camera 107 is arranged to monitor the area surrounding the industrial robot assembly 101. Furthermore, optical distance sensors 108 are arranged on the arm 102. The camera 107 and the optical distance sensors 108 together monitor an area 111 surrounding the industrial robot assembly 101. When an object 112 enters the area 111 the computer 1 13 adds a safety zone around the object 112 and considers the object to have the size of the dotted line 1 12^'. Then the computer 113 controls the arm to reconfigure into a second configuration, shown by the full line 1 14, while continuing handling objects in the first area 109. In the second configuration 114 of the arm 102 the distance d from the elbow 118 to the object 112^' has increased, which decreases the risk of the elbow 118 of the arm 102 hitting the object 112. It is possible to control the arm in other ways. It is for example possible to control the arm so that the minimum distance between the arm 102 and the object 112 is maximized.

Fig 3 shows schematically the industrial robot assembly 101 with a first zone 115, a second zone 116 and a third zone 117 surrounding the industrial robot assembly 101. If an object 112 enters the first zone 115 the industrial robot assembly 101 reconfigures the arm EP2008/066240

102 into a configuration in which a distance to the arm 102 increase in order to minimize the risk for a collision between the arm 102 and the object 112. If the arm is unable to reconfigure or if the speed of the object 1 12 is sufficiently high the object 112 might enter the second zone 116 or even the third zone 1 17. If the object enters the second zone 116 the industrial robot assembly lowers the speed of the arm 102. If the object 112 enters the third zone 1 17 the industrial robot assembly controls the arm to stop moving.

Apart from the position of the movable object 102 the industrial robot assembly may also control the arm 102 in response to the speed, the acceleration, the direction of motion and/or the change of direction of the object 112. To this end the computer 113 may comprise a prediction filter such as a Kalman filter.

The embodiments described above may be amended in many ways without departing from the spirit and scope of the present invention which is limited only by the appended claims.

The distance sensors may also or alternatively comprise optical sensors. The optical sensors have the same function as the ultrasonic sensors described above.

Even if the industrial robot assembly in the described embodiments have been described as having only one arm the industrial robot assembly may comprise two or more arms. Each one of the arms is controlled as has been described above.

it is possible within the scope of the invention that the industrial robot assembly has an arm having six internal degrees of freedom of motion. In that case one additional degree of freedom of motion is provided in another way. The arm may for example be arranged on a movable base.

Claims

1. An industrial robot assembly (101) comprising at least one movable arm (102) with a tool holder (103) on which a grip member (104) may be attached, which tool holder (103) is arranged in a first end of the arm (102) and a base part (105) arranged to be attached to a base (106), wherein the industrial robot assembly (101) has at least seven internal degrees of freedom of motion, characterized in that the robot assembly (101) comprises sensor means (107, 108, 121 ) for determining the position of a moving object (1 12) in relation to the robot assembly (101), wherein the robot assembly (101) when performing operations is arranged to adapt the configuration of said at least one movable arm (102) in response to the determined position of the object (102), when the moving object (112) is within a predetermined first zone (115) surrounding the robot assembly (101).

2. The industrial robot assembly (101 ) according to claim 1 , wherein the robot assembly (101) is arranged to adapt the configuration of said at least one movable arm (102) in order to maximize the smallest distance between the moving object (1 12) and the at least one movable arm (102).

3. The industrial robot assembly (101) according to claim 1 , wherein the movable arm (102) comprises joints (120) and wherein the robot assembly (101 ) is arranged to adapt the configuration of said at least one movable arm (102) in order to maximize the distance between at least one of the joints (120) and the moving object.

4. The industrial robot assembly (101) according to any one of the preceding claims, wherein the sensor means (107, 108, 121) comprises at least one camera (107) which is arranged to monitor the area (111) surrounding the robot assembly (101).

5. The industrial robot assembly (101) according to any one of claims 1-4, wherein the sensor means (107, 108, 121 ) comprises ultrasonic distance sensors (108).

6. The industrial robot assembly (101 ) according to claim 5, wherein the ultrasonic distance sensors (108) are arranged on the movable arm.

7. The industrial robot assembly (101) according to any one of the preceding claims, wherein the sensor means (107, 108, 121) comprises optical distance sensors (121).

8. The industrial robot assembly (101) according to claim 7, wherein the optical distance sensors (121 are arranged on the movable arm (102).

9. The industrial robot assembly (101 ) according to any one of the preceding claims, wherein the robot assembly (101) is arranged to determine the shape of the moving object (112), to add a safety zone (112^') around the moving object (112) and consider the object (112) to be the size of the safety zone (112^').

10. The industrial robot assembly (101 ) according to claim 9, wherein the robot assembly (101) is arranged to stop performing any operations if the movable arm (102) enters the safety zone (112^').

11. The industrial robot assembly (101 ) according to any one of the preceding claims, wherein the industrial robot assembly (101) is arranged to lower the speed of movement of the industrial robot assembly if the moving object (112) enters a predetermined second zone (1 16) surrounding the industrial robot assembly (101).

12. The industrial robot assembly (101) according to any one of the preceding claims, wherein the industrial robot assembly (101 ) is arranged to stop performing any operations if the moving object enters a predetermined third zone (117) surrounding the industrial robot assembly (101).

13. The industrial robot assembly (101) according to any one of the preceding claims, wherein the industrial robot assembly (101) comprises a base (106) to which the base part (105) of the movable arm (102) is attached.

14. The industrial robot assembly (101) according to claim 13, wherein the base (106) is movable.

15. The industrial robot assembly (101) according to any one of the preceding claims, wherein the movable arm has at least six internal degrees of freedom of motion.

16. The industrial robot assembly (101 ) according to any one of the preceding claims, wherein the movable arm has at least seven internal degrees of freedom of motion.

17. A method of controlling an industrial robot assembly (101) comprising at least one movable arm (102) with a tool holder (103) on which a grip member (104) may be attached, which tool holder (103) is arranged in a first end of the arm (102) and a base part (105) arranged to be attached to a base (106), wherein the industrial robot assembly (101) has at least seven internal degrees of freedom of motion, characterized by the steps of when the industrial robot assembly (101) is performing operations determining the position of a moving object (112) in relation to the industrial robot assembly (101), and adapting the configuration of said at least one movable arm (102) in response to the determined position of the object (102), when the moving object (112) is within a predetermined first zone (115) surrounding the industrial robot assembly (101).