WO2017036519A1

WO2017036519A1 - Device, system and method for teaching a position with a hand-held position teaching device

Info

Publication number: WO2017036519A1
Application number: PCT/EP2015/069983
Authority: WO
Inventors: Fan Dai; Arne WAHRBURG; Björn MATTHIAS; Hao Ding
Original assignee: ABB Schweiz AG
Current assignee: ABB Schweiz AG
Priority date: 2015-09-02
Filing date: 2015-09-02
Publication date: 2017-03-09
Anticipated expiration: 2018-03-02

Abstract

Hand-held position teaching device (12, 42, 82, 104) and a method for teaching a robot a position and an orientation with a Hand-held position teaching device, wherein the teaching device comprises a teaching device-TCP (18, 56), force sensors (32, 50, 52) and inertial sensors (20, 58) and its' coordinate system is calibrated to the robots' coordinate system, and wherein the teaching device is held in the desired position and orientation and transmits the teaching device-TCP position and orientation to the robot controller (116) to be stored. The user (102) may also apply force to a gripper (44, 48, 84, 88) of the teaching device and grip a workpiece (108, 110) in order to teach a gripping function. The robot controller may afterwards use the plurality of stored positions and orientations to control and move the robot. This is significantly easier than moving the whole robot arm with a teaching device mounted thereon or controlled by it. The user interface of the gripper comprises springs.

Description

DEVICE, SYSTEM AND METHOD FOR TEACHING A POSITION WITH A HAND-HELD POSITION TEACHING DEVICE

Description The invention is related to a hand-held position teaching device for robot programming.

It is known, that robots are widely used in industrial production, such as for handling tasks like gripping, welding or painting. Dependent on their respective purposes ro- bots have typically a robot arm with a length in the range of 0,5 to 3,5m that consists of several robot members and that are connected by respective hinged joints to a kinematic chain. A robot arm typically comprises five to seven joints, so that in total five to seven degrees of freedom in movement are gained. Usually a mechanical interaction tool is mounted at the tip of the robot arm to mechanically go into contact with a workpiece to be treated or gripped. A mechanical interaction tool might be a tip, a gripper or a welding gun for example.

In principle a robot with at least six degrees of freedom in movement has the ability to reach all coordinates within its working range in each desired orientation with the tip of its arm. Dependent on the coordinate system of the robot three degrees of freedom in movement are required to reach any x, y, z coordinate, whereas the other three degrees of freedom in movement are required to gain any orientation around the coordinate. Such flexibility is required for example for complex robot tasks like gripping a workpiece or welding or the like. Of course six degrees of freedom in movement are of also advantage for tasks with no direct mechanical contact to the workpiece to be treated such as robotic paint spraying. The robot joints are driven by dedicated motors that usually are controlled by a common robot controller. A typical robot controller comprises a computing unit and several amplifiers for the electric supply of the motors with a respective suitable variable voltage signal. The robot controller is foreseen to execute a respective robot program on its computing unit. A robot program usually comprises data about the desired movement path of the tip of the robot arm respectively of a reference point in a fixed relation thereto, which is a so-called tool center point (TCP). Based on the robot program executed by the computing unit the motors of the respective robot joints are controlled in that way, that the tip of the robot arm respectively the TCP is moving along the desired movement path.

Normally a desired movement path is described within the robot program by subsequent coordinates along its extension. A coordinate might include - besides values for desired x, y, z position - a desired orientation of the tip of the robot arm respectively the TCP, so that - dependent on the coordinate system used - three values per coordinate are required to define the coordinate as such within the three dimensional x, y, z coordinate system and further three values per coordinate are required to define the orientation. The robot controller interpolates the movement path in between the subsequent coordinates provided within the robot program. In order to get the coordinates within the robot program aligned with the coordinate system of the real robot, both, the coordinates in the robot program and the coordinate system of the robot itself, have to be aligned to the same reference coordinate system.

A robot movement program might additionally include some reference values for a force on a workpiece to be treated that has to be applied by the mechanical interac- tion tool. This might be for example a gripping force that is applied by the gripper fingers of a gripper on a gripped object in between them. But also a mechanical force that is applied by use of a tip-like mechanical interaction tool mounted on the tip of a robot arm on a workpiece in order to move it to another location might be subject to be defined in a robot program. The observance of such a force during execution of the robot program might be enabled as well by use of force sensors implemented in the mechanical interaction tool as by an indirect calculation of a force by use of the electrical currents of the motors of the robot joints for example. In case that the given maximum force is reached the respective motors are controlled in that way that the prescribed maximum force is not exceeded.

Disadvantageous within the state of the art is that during generation of a robot program the teaching of the coordinates of the movement path is very elaborate, especially in case of a desired mechanical interaction of the mechanical interaction tool with the workpiece to be treated. Teaching of coordinates might be done for example by use of an offline CAD simulation system, which requires a lot of simulation data (CAD models), effort, experiences and time in a disadvantageous way.

Another but also disadvantageous possibility of teaching coordinates of a movement path consists in moving a real robot arm with its mechanical interaction tool mounted thereon manually around the workpiece to be treated and to set a respective coordinate in the robot program when a desired location has been reached. Each movement of the robot arm requires the control of its motors with a teach pendant or the like. Thus also this procedure is very time consuming, especially in case of a mechanical interaction of the mechanical interaction tool with the workpiece to be treated since only a very low tolerance of the TCP is admitted then, otherwise a mechanical collision would be the consequence during teaching or execution of the robot program.

Automated spraying application for example has a much higher tolerance since a typical spraying distance might be in between 20cm to 25cm, so that deviations of +/- 1 cm in the distance to the surface of the object to be treated will not cause a collision or even a measurably reduction of the paint result.

Objective of the invention is to provide a device and a method, which facilitate the teaching respectively determination of coordinates of a movement path when generating a robot program. The problem is solved by a hand-held position teaching device for robot programming of the aforementioned kind. This is characterized by

• a hand-held base body,

· a mechanical interaction device mounted on the hand-held base body and defining a reference tool center point,

• wherein the mechanical interaction device comprises at least one force sensor,

• a position determination device integrated in the hand-held base body that is foreseen to determine the position of the reference tool center point relatively to a reference coordinate system that is aligned to the mechanical interaction device,

• a communication interface for data exchange with a computing device, in particular with a robot controller,

· wherein the hand-held position teaching device is foreseen to provide data to its communication interface that describe the current position of the reference tool center point relatively to the aligned reference coordinate system and a force measured by the at least one force sensor. Basic idea of the invention is to use a hand-held position teaching device for manually teaching a position by holding the tool center point (TCP) of its mechanical interaction device on the desired location on the surface of a real reference workpiece of a type that is foreseen to be treated by a robot later on. This is significantly easier than moving the whole robot arm with a mechanical interaction device mounted thereon around a workpiece for position teaching. The position of the TCP of the mechanical interaction device is determined with respect to an aligned reference coordinate system by the integrated position determination device.

Afterwards the determined position is transmitted by the communication interface to, for example, an external computing device, which might be a personal computer with a simple text editor running thereon, so that the data of the position transmitted thereto can easily become implemented into a robot program. Of course it is also possible to have for example a CAD system running on the computing device so that CAD programming is extremely facilitated by providing the respective position by the hand- held position teaching device according to the invention. The computing device might also be part of a robot controller itself, which is foreseen to control a robot for executing a respective robot program using those positions. According to the invention preferably a mechanical contact in between the mechanical interaction device and the workpiece to be treated is foreseen when determining the data of a position to be taught. Thus the mechanical interaction device mounted on the hand-held base body is designed in that way, that it is defining a reference tool center point. This might be in the easiest case a tip whose end corresponds to the tool center point. Thus it is possible to manually press the end of the tip, which is corresponding to the tool center point, onto the surface of the workpiece to be treated. Due to the mechanical contact in between the mechanical interaction device and the workpiece a deviation of the taught x, y, z coordinate to the desired x, y, z coordinate is excluded in an advantageous way. Thus the teaching of position coordinates with a hand-held device according to the invention will lead to high precision position data, which are of extreme importance for robot tasks like gripping or welding for example and which require a mechanical contact to the workpiece to be treated.

As mentioned before, the mechanical interaction device of the hand-held position teaching device is foreseen to go into mechanical contact with the workpiece to be treated so that accordingly a respective contact force in between mechanical interaction device and workpiece is caused.

Thus it is possible, to manually and intuitively teach a force with the mechanical in- teraction device of the hand-held position teaching device and use the force data determined with the at least one force sensor as control data for a robot program to be generated.

According to another embodiment of the hand-held position teaching device it further comprises a user interface for manual interaction to initiate providing of data to the communication interface, in particular a button. Of course also a touch display or the like is a suitable interface. Thus it is facilitated to precisely position the hand-held position teaching device as desired and to trigger the determination of the position and a respective force afterwards by using the user interface respectively by pushing a button.

According to a further embodiment of the hand-held position teaching device, the us- er interface for manual interaction to initiate providing of data to the communication interface comprises a button, means for detecting a galvanic contact of the mechanical interaction device with a work piece or other objects, means for detecting a predetermined threshold force to be achieved by a contact with a work piece or other objects and/or other sensory means.

Thus it is also possible to use a mechanical respectively galvanic contact of for example a tip of the mechanical interaction device representing the tool center point with a work piece to trigger the data transfer at the communication interface. This is a very intuitive way of teaching. Exceeding a threshold of a respective contact force as optional additional trigger criterion will reduce the risk that providing data is triggered unintentionally.

According to another embodiment of the invention the mechanical interaction device comprises a tip defining the reference tool center point. Thus the end of the tip can easily be used as pointer to define a coordinate on the surface of a workpiece. Preferably the end of the tip is covered with a soft material so that scratches or the like on the surface of the workpiece are avoided therewith.

According to a further embodiment of the hand-held position teaching device the me- chanical interaction device comprises a gripper with gripper fingers defining the reference tool center point in between them. Grippers might have two or more gripper fingers which can be opened and closed. A gripper mounted on the arm of a robot is typically driven by a motor or another actuator. According to another embodiment of the invention the gripper comprises a manual usable spring mechanism, so that - other than a manual force - no drive, motor or actuator is required for opening and closing the gripper fingers. This enables the intuitive gripping of a workpiece in an advantageous way so that a position and a force required for gripping are teachable synchronously. According to another embodiment of the invention the hand-held position teaching device comprises a user interface for manual interaction to initiate opening and/or closing the gripper fingers. This might be in the easiest case one or more buttons to initiate an opening or closing movement of the gripper fingers, which might be driven be a manipulator.

According to a further embodiment of the hand-held position teaching device it comprises a display as part of a user interface. A touch display for example is an easy way for active communication in between of a user and an electric device. Optionally a further computing device integrated in the hand-held position teaching device could be foreseen to perform tasks like preprocessing of measurement values and controlling the dialogue with the user. According to another embodiment of the hand-held position teaching device the at least one force sensor is foreseen to measure a contact force applied with the reference tool center point on an external object and/or in case of a gripper an applied gripping force in between the gripper fingers. According to another embodiment of the invention a mechanical interaction device is extending along a reference axis, wherein the position- and orientation determination device is also foreseen to determine the orientation of the reference axis relatively to the aligned reference coordinate system and wherein the hand-held position teaching device is foreseen to provide data to its communication interface which describe the orientation of the reference axis relatively to the aligned reference coordinate system. Thus it is possible to determine a full position vector by use of the hand-held position teaching device. Generating a robot program is facilitated using those position vectors since no subsequent tuning of the orientation is required any more. The problem of the invention is also solved by a position teaching system, comprising a hand-held position teaching device according to the invention and further comprising a computing device, in particular a robot controller, which is connected to the communication interface of the hand-held position teaching device and that is foreseen to receive and store provided data. The advantages resulting therefrom have already been previously presented, in particular the facilitating of generating a robot program by use of the hand-held position teaching device.

According to another variant of the position teaching system it further comprises a robot, which is controllable by the computing device, in particular by the robot controller, wherein the coordinate system of the robot is aligned to the same reference coordinate system than the mechanical interaction device. Thus it is possible to verify for example a robot program based on coordinates determined by a hand-held position teaching device immediately after generating the robot program. Preferably the same workpiece is used for teaching than for verifying.

The problem of the invention is also solved by a method for teaching a position by use of a position teaching system according to the invention, comprising the following steps:

· moving the mechanical interaction device into a position to be taught,

• determining the position of the reference tool center point relatively to the aligned reference coordinate system,

• providing data to the communication interface that describe the current position of the reference tool center point relatively to the aligned reference coor- dinate system,

• storing the data on the computing device, in particular on the robot controller.

In the case that the mechanical interaction device is not yet aligned with the reference coordinate system, the following step should be done previously:

· moving the mechanical interaction device into a reference position that is related to the reference coordinate system and calibrating the position- determination device thereto, so that the mechanical interaction device is aligned to the reference coordinate system. Thus it is facilitated to teach coordinates for a robot program by use of the position teaching system according to the invention.

According to a further variant of the invention the following additional steps are foreseen: • applying a force on a force sensor of the mechanical interaction device in the position to be taught, in particular applying a force with the reference tool center point on an external object and/or in case of a gripper applying a force in between the gripper fingers,

· providing also those data to the communication interface that describe the force measured by the at least one force sensor.

In particular teaching of a gripping process is facilitated therewith since the coordinate of the gripping location as the gripping force itself is teachable in the same intui- tive step therewith. But also the teaching of a handling process is simplified therewith.

According to another embodiment of the method of the invention it is repeated for several positions to be taught. Thus it is possible to teach a complete movement path.

Another variant of the method of the invention is characterized by the following additional steps:

• generating a robot program describing the desired movement path of a tool center point of a robot by using the data received and stored by the computing device as movement path coordinates, wherein the robot is aligned to the same reference coordinate system than the mechanical interaction device.

Since the robot is aligned to the same reference coordinate system than the mechan- ical interaction device the coordinates determined with the hand-held teaching device can be imported into the robot program to be generated without any adaptations. In case of a displacement the coordinates have to be adapted accordingly.

Further advantageous embodiments of the invention are mentioned in the dependent claims.

The invention will now be further explained by means of an exemplary embodiment and with reference to the accompanying drawings, in which: Figure 1 shows an exemplary first hand-held position teaching device,

Figure 2 shows an exemplary second hand-held position teaching device,

Figure 3 shows an exemplary third hand-held position teaching device,

Figure 4 shows an exemplary position teaching system,

Figure 5 shows an exemplary first robot system and

Figure 6 shows exemplary second robot system.

Figure 1 shows an exemplary first hand-held position teaching device 10. A mechanical interaction device 14 - in this case an elongated part with a tip - is mounted on a hand-held base body 12 and is extending along a reference axis 1 6. The end of the elongated part is defining a reference tool center point 18, which is foreseen to be manually hold in a respective desired orientation on several locations on the surface of a workpiece so that respective position vectors can be determined by use of a position- and orientation determination device 20, which is also integrated in the hand- held base body 12. A position vector might be described by three data values for x-, y- and z- coordinates of the tool center point and three data values for orientation of the reference axis 1 6. The position- and orientation determination device 20 might be based on a gyrostatic compass or an inertial measurement device, for example, and is aligned 24 to a reference coordinate system 22.

A force sensor 32 is foreseen to determine any force which is applied through the mechanical interaction device 14 on an external workpiece. The respective measurement data of a respective force are provided to the communication interface 26 in the same way than the coordinate data of the tool center point respectively the orien- tation of the reference axis. A computing unit 30 is foreseen for performing smaller computing tasks such as preprocessing of measurement values for example.

A communication interface 26 is foreseen to communicate the respective determined measurement data of position of the tool center point and the determined measure- ment data of the orientation of the reference axis 16, which in combination are defining a position vector, via a data exchange 28 to an external computing unit that is not depicted in this figure. Providing of data to the communication interface 26 can be initiated by a manual action, for example by pushing a button 34. Thus it is possible to place and align the hand-held position teaching device 10 respectively its tool center point 18 in the desired position before transmitting the measurement data to an external computing device.

Figure 2 shows an exemplary second hand-held position teaching device 40. A mechanical interaction device 44 - in this case gripper with gripper fingers 46, 48 - is mounted on a hand-held base body 42 and is extending along a reference axis 54. A tool center point 56 is defined on the reference axis 54 in between the gripper fingers 46, 48 at the height of their axial end. Each gripper finger 46, 48 is provided with a respective force sensor 50, 52, so that a clamping force in between the gripper fingers 46, 48 is determinable therewith. Respective position vectors can be determined by use of a position- and orientation determination device 58, which is also integrated in the hand-held base body 42. The position- and orientation determination device 58 is aligned 62 to a reference coordinate system 60. A communication interface 64 is foreseen to communicate the respective determined measurement data of position of the tool center point and the determined measurement data of the orientation of the reference axis 54 via a data exchange 66 to an external computing unit that is not depicted in this figure. A computing unit 68 is foreseen for performing smaller computing tasks such as preprocessing of measurement values. Providing of data to the communication interface 64 can be initiated by a manual action, for example by pushing a button 70, or by detecting the contact with the work piece by galvanic contact, or by determining a predetermined threshold force to be achieved by the contact with the work piece or other objects, or by other sensory means.

Figure 3 shows an exemplary third hand-held position teaching device 80. A mechanical interaction device 84 - in this case gripper with gripper fingers 86 - is mounted on a hand-held base body 82. A user interface 90 respectively a button is foreseen to initiate providing position and orientation data determined by a not shown position- and orientation determination device integrated within the hand-held base body 82.

The gripper fingers 86 can be opened and closed by manually compressing a clamp- like user interface 88 for manual interaction. This is a very simple and intuitive method that also provides a simple force feedback to the hand of the user. In case that also a force value has to be determined the hand-held position teaching device 80 can easily be equipped with one or more force sensors. Figure 4 shows an exemplary position teaching system 100 with a user 102. A conveyor 1 12 is foreseen to provide workpieces to be gripped. The user 102 held in his right hand an exemplary hand-held position teaching device 104 in a desired pose to be taught. He is manually applying a force 106 on a gripped workpiece 108, wherein the force is determined by a force sensor integrated in the hand-held position teach- ing device 104.

The hand-held position teaching device 104 further comprises a position- and orientation determination device that is aligned 120 to a reference coordinate system 1 18. A communication interface is foreseen for data exchange 1 14 with an external com- puting device 1 1 6, so that measurement data of the tool center point, orientation and the force in between the gripper fingers can be provided to the external computing device 1 1 6.

Figure 5 shows an exemplary first robot system 130. A conveyor 138 is providing workpieces to be gripped. A robot 140 is controlled by a computing device 142 - in this case a robot controller - and has a further mechanical interaction device 132 respectively a gripper mounted on the tip of its arm. The gripper applies a force 134 on a gripped workpiece 136. The movements of the robot 140 and of the gripper are controlled according to a movement program running on the computing device 142. The position vectors within the robot program defining the movement path of the robot arm have been taught by use of a hand-held position teaching device as depicted in figure 4. The robot 140 respectively the computing device 142 is aligned 146 to a reference coordinate sys- tem 144 that is the same as the reference coordinate system for the hand-held position teaching device shown in figure 4. Thus it is ensured, that the taught position vectors are fitting to the desired robot movement. Figure 6 shows an exemplary second robot system 150. A robot 152 is controlled by a computing device 154 - in this case a robot controller - and has a further mechanical interaction device 1 62 respectively a gripper mounted on the tip of its arm. The robot 152 respectively the computing device 154 is aligned 1 60 to a coordinate system that is different from a coordinate system 156, which has been used for teaching the coordinate vectors of the robot program running on the computing device 154. In order to compensate a shift in between the respective coordinate systems a coordinate system adjustment 158 is foreseen.

List of reference siqns

10 exemplary first hand-held position teaching device

12 hand-held base body

14 mechanical interaction device (tip)

16 reference axis

18 reference tool center point

20 position- and orientation determination device

22 reference coordinate system

24 alignment

26 communication interface

28 data exchange

30 computing unit

32 force sensor

34 user interface for manual interaction (buttons)

40 exemplary second hand-held position teaching device

42 hand-held base body

44 mechanical interaction device (gripper)

46 gripper finger

48 gripper finger

50 force sensor

52 force sensor

54 reference axis

56 reference tool center point

58 position- and orientation determination device

60 reference coordinate system

62 alignment

64 communication interface

66 data exchange

68 computing unit

70 user interface for manual interaction (buttons)

80 exemplary third hand-held position teaching device

82 hand-held base body

84 mechanical interaction device (gripper)

86 gripper fingers 88 user interface for manual interaction (clamp)

90 user interface for manual interaction (button)

100 exemplary position teaching system

102 user

104 exemplary fourth hand-held position teaching device

106 manually applied force

108 gripped workpiece

1 10 further workpieces

1 12 conveyor

1 14 data exchange

1 1 6 computing device

1 18 reference coordinate system

120 alignment

130 exemplary first robot system

132 further mechanical interaction device (gripper)

134 force applied by further mechanical interaction device

136 gripped workpiece

138 conveyor belt

140 robot

142 computing device (robot controller)

144 reference coordinate system

146 alignment

150 exemplary second robot system

152 robot

154 computing device (robot controller)

156 alternative reference coordinate system

158 coordinate system adjustment

160 alignment

162 further mechanical interaction device (gripper)

Claims

1 . Hand-held position teaching device (10, 40, 80, 104) for robot (140, 152) programming, comprising

• a hand-held base body (12, 42, 82),

• a mechanical interaction device (14, 44, 84) mounted on the hand-held base body (12, 42, 82) and defining a reference tool center point (18, 56),

• wherein the mechanical interaction device (14, 44, 84) comprises at least one force sensor (32, 50, 52)

• a position determination device (20, 58) integrated in the hand-held base body (12, 42, 82) that is foreseen to determine the position of the reference tool center point (18, 56) relatively to a reference coordinate system (22, 60, 1 18, 144) that is aligned (24, 62, 120) to the mechanical interaction device (14, 44, 84),

• a communication interface (26, 64) for data exchange (28, 66, 1 16) with a computing device (1 1 6, 142, 154), in particular with a robot controller,

• wherein the hand-held position teaching device is foreseen to provide data to its communication interface (26, 64) that describe the current position of the reference tool center point (18, 56) relatively to the aligned (24, 62, 120) reference coordinate system (22, 60, 1 18, 144) and a force (106) measured by the at least one force sensor (32, 50, 52).

2. Hand-held position teaching device according to claim 1 , characterized in that it further comprises a user interface (34, 70, 90) for manual interaction to initiate providing of data to the communication interface (26, 64).

3. Hand-held position teaching device according to claim 2, characterized in that the user interface (34, 70, 90) for manual interaction to initiate providing of data to the communication interface (26, 64) comprises a button (70), means for detecting a galvanic contact of the mechanical interaction device (14, 44, 84) with a work piece or other objects, means for detecting a predetermined threshold force to be achieved by a contact with a work piece or other objects and/or other sensory means.

4. Hand-held position teaching device according to any of the previous claims, characterized in that the mechanical interaction device (14, 44, 84) comprises a tip defining the reference tool center point (18, 56).

5. Hand-held position teaching device according to claim 1 to 3, characterized in that the mechanical interaction device (14, 44, 84) comprises a gripper with gripper fingers (46, 48, 86) defining the reference tool center point (18, 56) in between them.

6. Hand-held position teaching device according to claim 5, characterized in that the gripper comprises a manual usable spring mechanism, so that - other than a manual force - no drive or actuator is required for opening and closing the gripper fingers (46, 48, 86).

7. Hand-held position teaching device according to claim 5, characterized in that it comprises a user interface (34, 70, 88, 90) for manual interaction to initiate opening and/or closing the gripper fingers (46, 48, 86).

8. Hand-held position teaching device according to any of the previous claims, characterized in that it comprises a display as part of a user interface.

9. Hand-held position teaching device according to any of the previous claims, characterized in that the at least one force sensor (32, 50, 52) is foreseen to measure a contact force applied with the reference tool center point (18, 56) on an external object and/or in case of a gripper an applied gripping force (106) in between the gripper fingers (46, 48, 86).

10. Hand-held position teaching device according to any of the previous claims, characterized in that a mechanical interaction device is extending along a reference axis (16, 54), wherein the position- and orientation determination device (20, 58) is also foreseen to determine the orientation of the reference axis (1 6, 54) relatively to the aligned reference coordinate system (22, 60, 1 18, 144) and wherein the hand- held position teaching device is foreseen to provide data to its communication interface (26, 64) that describe the orientation of the reference axis (1 6, 54) relatively to the aligned (24, 62, 120) reference coordinate system (22, 60, 1 18, 144).

1 1 . Position teaching system, comprising a hand-held position teaching device (10, 40, 80, 104) according to claim 1 to 9, characterized in that it further comprises a computing device (1 16, 142, 154), in particular a robot controller, which is connected to the communication interface (26, 64) of the hand-held position teaching device and that is foreseen to receive and store provided data.

12. Position teaching system according to claim 10, characterized in that it further comprises a robot (140, 152), which is controllable by the computing device (1 16, 142, 154), in particular by the robot controller, wherein the coordinate system of the robot (140, 152) is aligned (24, 62, 120) to the same reference coordinate system (22, 60, 1 18, 144) as the mechanical interaction device (14, 44, 84).

13. Method for teaching a position by use of a position teaching system according to claim 1 1 or 12, comprising the following steps:

• moving the mechanical interaction device (14, 44, 84) into a position to be taught,

• determining the position of the reference tool center point (18, 56) relatively to the aligned (24, 62, 120) reference coordinate system (22, 60, 1 18, 144),

• providing data to the communication interface (26, 64) that describe the current position of the reference tool center point (18, 56) relatively to the aligned (24, 62, 120) reference coordinate system (22, 60, 1 18, 144),

• storing the data on the computing device (10, 40, 80, 104), in particular on the robot controller.

14. Method according to claim 13, characterized by the following additional steps:

• applying a force (106) on a force sensor (32, 50, 52) of the mechanical interaction device (14, 44, 84) in the position to be taught, in particular applying a force with the reference tool center point (18, 56) on an external object and/or in case of a gripper applying a force in between the gripper fingers (46, 48, 86), • providing also those data to the communication interface that describe the force (106) measured by the at least one force sensor (32, 50, 52).

15. Method according to claim 13 or 14, characterized in that it is repeated for several positions to be taught.

16. Method according to 13 to 15, characterized by the following additional steps:

• generating a robot program describing the desired movement path of a tool center point of a robot (140, 152) by using the data received and stored by the computing device (1 1 6, 142, 154) as movement path coordinates, wherein the robot (140, 152) is aligned (24, 62, 120) to the same reference coordinate system (22, 60, 1 18, 144) as the mechanical interaction device (14, 44, 84).