DE102023108739A1 - Calibration tool, calibration system and method for autonomous calibration of a robot - Google Patents

Abstract

The invention relates to a calibration tool (1) for the independent calibration of a robot (60) for the repeated, highly precise locating of one or more different processing positions of the robot (60), wherein the calibration tool (1) comprises: a first calibration element (10) which is designed to be arranged on a robot arm (64) of a mobile or stationary robot (60), and a second calibration element (30) which is designed to be arranged on a stationary or mobile calibration station (5), wherein the first or the second calibration element (10, 30) comprises a centering pin (12), and wherein the second or the first calibration element (30, 10) comprises a bushing (32) contoured complementarily to the centering pin (12), wherein the centering pin (12) is designed to be immersed in an immersion direction (f1) into the bushing (32) up to an end position, and wherein the first or the second calibration element (10, 30) a rotary centering part (42) arranged laterally of the centering pin (12) or the bushing (32), which interacts with a rotary counterpart (22) arranged on the second or first calibration element (30, 10) by rotating about the immersion direction (f1) in order to determine the rotary position of the first or second calibration element (10, 30) from these rotary movements of the first or second calibration element (10, 30).

Description

The invention relates to a calibration system for the independent calibration of a robot for the repeated, high-precision locating of one or more different processing positions of the robot.

The term mobile robotics means that a robot can be used flexibly in different locations. If it changes its position, it must be precisely aligned in its new location so that it can execute the program it once learned without errors in its new position.

Calibration systems are known from the state of the art. For example, the JP 5 337 856 A a first calibration element in the form of a cone, which is arranged at a distal end of a robot and is inserted into a complementarily designed socket as a second calibration element. When the drive and brake are switched off, the first calibration element falls into the socket due to gravity in order to determine a calibration position.

In the EP 2 328 724 A1 A calibration tool for calibrating an industrial robot, in particular a six-axis one, is described, in which a pin, rod or pin of a first calibration element is inserted into a complementary socket of a second calibration element. The calibration is also effected here by means of mechanical forced guidance, which is effected by the calibration tool in conjunction with a measuring arrangement, in particular a force sensor.

The known calibration tools are sometimes difficult to handle and sometimes difficult to set up. In particular, they require complicated zero clamping systems or very complex and expensive camera technology. In addition, they are not suitable for many applications.

It is an object of the present invention to provide a calibration tool, a calibration system and a method for the independent calibration of a robot, which enables a safe and repeated approach to a calibration station with high precision and thus the independent calibration of a robot, in particular also of a movable robot, for which the requirements in terms of precision are particularly high.

This problem is solved by the subject matter of the independent claims.

According to the invention, a calibration tool is provided that comprises a first calibration element and a second calibration element, both of which are designed to be complementary or corresponding to one another. One of the two calibration elements comprises a centering pin and the other calibration element comprises a bushing designed to correspond to the centering pin. The centering pin can be inserted into the bushing in an immersion direction (or vice versa) until it assumes a defined end position. The calibration tool also comprises a rotary centering part that is provided to the side of the centering pin or the bushing and, preferably in the at least partially immersed state of the centering pin in the bushing, cooperates with a rotary counterpart in order to determine the rotational position of the first or second calibration element.

By means of the invention, a calibration can be carried out in which, in addition to the three spatial coordinates x, y, z, the angles in space (represented by rotation vectors rx, ry, rz) are also repeatedly determined and - if necessary - corrected. The three spatial coordinates are determined or confirmed in particular by the forced immersion of the centering pin into the bushing when the centering pin is in its end position. In this case, the tip of the centering pin preferably defines the spatial coordinates x, y and z. The three rotation vectors are determined by means of the rotary centering part and the rotary counterpart. In this case, two of the three rotation vectors are preferably already determined by determining the rotary centering part or the rotary counterpart; the third rotation vector is then determined by rotating the rotary centering part relative to the rotary counterpart.

The phrase "plunging in of the centering pin" also includes the relative movement of the bushing being moved in the direction of the centering pin and being pulled over it, not just the movement of the centering pin in the direction of the bushing and into the bushing. This is repeatedly pointed out in some places.

The term "robot" refers to automated handling devices controlled by computer programs that carry out repetitive mechanical work. They can be mobile or stationary machines. In particular, the term "robot" includes industrial robots and collaborative robots (so-called cobots) of all kinds, whereby the robots can in particular be designed with 5 to 7 axes.

The rotary centering part can consist of one or more components, which in the latter case can also be arranged spatially separated from each other can be, for example, as spatially separated projections. The same applies to the rotating counterpart.

According to a preferred embodiment, the rotary centering part and the rotary counterpart are arranged spatially separated from the centering pin and the bushing. For example, the rotary centering part is provided laterally from the centering pin or the bushing at a distance of a few millimeters or centimeters, for example on a base plate on which the centering pin or the bushing is also arranged. In this case, for example, the longitudinal axis of the centering pin or the bushing is aligned in the immersion direction. The rotary centering part is then arranged laterally of the longitudinal axis of the centering pin or the bushing, which can also be aligned in the immersion direction. The same applies to the rotary counterpart, which in this case is provided laterally offset from the bushing or the centering pin, for example also on a base plate for the bushing or the centering pin.

According to an alternative, the rotary centering part has at least one projection that projects outwards at an angle relative to the longitudinal axis of the centering pin. The rotary counterpart in turn has at least two projections. The projection of the rotary centering part can now be rotated in the end position of the centering pin between the two projections of the rotary counterpart until it strikes the two projections, from which the control device can in turn determine the angular or rotary position of the first calibration element.

According to a further alternative, the rotary centering part also has at least one projection that protrudes outwards at an angle relative to the longitudinal axis of the centering pin. In this alternative, the rotary counterpart is designed as a blind hole into which the projection enters and can be rotated in the angular range of the elongated hole.

According to a further alternative, the rotary centering part is arranged on the centering pin or the bushing and the rotary counterpart is arranged on the inner wall of the bushing or the outer wall of the centering pin. For example, a relatively narrow, elongated, projection on the outer wall of the centering pin is provided as the rotary centering part, which can be rotated around the immersion direction in a recess set back in the radial direction (as a rotary counterpart) in the bushing. The recess runs over a partial circumference of the bushing. Alternatively, such a recess is also possible in the centering pin and a projection in the bushing.

According to a further advantageous embodiment, the rotary centering part can touch a first contact surface of the rotary counterpart when the centering pin is (relatively) immersed in the bushing and can slide along this first contact surface by rotating the first or second calibration element around the immersion direction until the rotary centering part can engage or retract into the rotary counterpart by moving the first or second calibration element in the immersion direction. In this immersed state, the rotary centering part can then be rotated in the rotary counterpart according to this embodiment. Alternatively, the rotary counterpart is designed in the form of a shaft that preferably runs linearly in the immersion direction and no longer allows rotation of the rotary centering part once it has been inserted into the shaft. The end position of the centering pin, which can then no longer be rotated, is reached after it has been completely inserted into the bushing. In this case, the rotary centering part can also have, for example, two projections that protrude outwards at an angle relative to the longitudinal axis of the centering pin, which are opposite one another and each penetrate into correspondingly opposite shafts that form the rotary counterpart. These designs ensure that the rotary centering part can actually interact with the rotary counterpart, even if it initially only hits one or more first contact surfaces of the rotary counterpart, but is then guided into the inserted state.

An advantageous embodiment provides that the rotary centering part comprises at least one dowel pin and the rotary counterpart comprises a curved elongated hole. The dowel pin is provided, for example, on the side of the bushing and protrudes against the immersion direction of the centering pin, while the elongated hole is provided on the side next to the centering pin, corresponding to the dowel pin and can be arranged in alignment with it. The elongated hole preferably extends in a direction that is perpendicular to the immersion direction. Preferably, the dowel pin and bushing on the one hand and the elongated hole and centering pin on the other hand are each integral or at least part of the respective calibration element in a fixed spatial relationship to one another.

According to an alternative, the dowel pin can also be provided on the side of the centering pin and the rotating counterpart on the side of the bushing.

Preferably, the dowel pin can be inserted into the slot by moving the first or second calibration element in the insertion direction. By rotating the first or second calibration element about the insertion direction, which preferably coincides with the longitudinal axis of the centering pin when rotating, the dowel pin then comes to at least at least one, preferably both ends of the elongated hole. Alternatively, one of the two end positions of the dowel pin can be determined if it slides along the wall of one of the hole ends when the centering pin is inserted. In each of these cases, the rotational position of the first or second calibration element can then be determined with the aid of a computer.

In a further development, for example, a support pin can be arranged on the opposite side of the dowel pin and also protruding from the projection, which ends at the same height as the dowel pin, but is preferably arranged radially further outwards (alternatively further inwards) than the dowel pin. When the first calibration element is immersed, the base plate comes into contact with the support pin just as it does with the dowel pin when the elongated hole is aligned with the dowel pin. The load of the base plate is then distributed over both the dowel pin and the support pin, so that the dowel pin is not subjected to excessive loading. So that the support pin does not get in the way of the elongated hole being retracted when the elongated hole is above the dowel pin, another curved elongated hole is provided in the base plate, which is arranged opposite the elongated hole. The elongated hole for the support pin, which also runs at a greater (alternatively smaller) radial distance from the longitudinal axis of the bushing than the elongated hole, expediently extends over a larger angular range than the elongated hole. This design ensures that the support pin actually only serves to support the load and does not influence the calibration or cause an incorrect measurement.

The centering pin preferably has a non-linear side surface contour as an outer contour, while the bushing has a corresponding inner contour. It has been found that such an outer contour of the centering pin prevents a control or monitoring device from rocking (see also below). The inventors observed such rocking in particular in designs in which the centering pin was cylindrical or conical. The inventors suspect that the unstable behavior of the monitoring device resulted from an ambiguous determination of the position of such a centering pin in the bushing and/or from excessive friction between the centering pin and the bushing when immersed.

It has proven to be particularly advantageous if the centering pin, which preferably generally tapers towards its tip, is stepped and preferably double-stepped. Good and highly precise results were obtained with a double-stepped cone as the centering pin, with the bushing being designed to complement it with a double-stepped inner cone.

Preferably, both the centering pin and the bushing are rotationally symmetrical. When the centering pin moves from above into the bushing, the immersion direction is simultaneously the z-axis and the longitudinal axis of the centering pin.

However, it is also possible for the insertion direction of the centering pin (or the bushing) into the bushing (or into the centering pin) to be in the x or y direction or in any other direction in space. The rotational and longitudinal axis of the centering pin also advantageously coincides with the insertion direction here.

A preferred embodiment provides that the bushing has an opening pointing downwards. In this case, dirt that adheres to the centering pin, for example, and falls off through contact with the bushing or through other movement, can fall downwards out of the bushing through this opening. This prevents the measurement precision from being impaired by the presence of dirt on the centering pin and/or bushing.

The invention also relates to a calibration system with a calibration tool as described above. The calibration system comprises a robot with a robot arm to which the first or second calibration element can be attached and to which a tool or workpiece can be held in a fixed relation to the first or second calibration element. The robot arm is force-controlled by providing a force measuring device on or in the robot arm, preferably a sensor device with at least one force and/or torque sensor and preferably designed as one or more multi-axis force-torque sensors. Alternatively, the force measuring device can also estimate the forces without sensors, e.g. based on the motor currents in the drives of the robot arm segments. The force measuring device records the contact points of the centering pin and bushing and/or the forces arising from contact between the centering pin and bushing, as well as the contact points of the rotary centering part and rotary counterpart and/or the forces arising from contact between the rotary centering part and rotary counterpart. The force measuring device transmits the corresponding measured values to a computer-controlled control device which carries out control and/or regulating functions and in particular controls the movement of the centering pin relative to the bushing and the movement of the rotary centering part relative to the rotary counterpart.

Force control here refers to the control of the force with which the calibration element on the robot arm acts on the calibration element on the calibration station. The force acting is usually measured for control purposes using force sensors or estimated using the motor current. The control device uses the corresponding results to control the relative movement of the first calibration element to the second.

• - durch Bewegen des ersten oder zweiten Kalibrierelements werden, solange noch nicht vorliegend, die beiden Konturen von Drehzentrierteil und Drehgegenstück zueinander in Flucht gebracht,
• - der Zentrierzapfen wird kraftgeregelt in Eintauchrichtung relativ zur Buchse bewegt, bis der Zentrierzapfen seine Endstellung in der Buchse erreicht,
• - durch kraftgeregeltes Drehen des ersten Kalibrierelements relativ zum zweiten Kalibrierelement wird auf Grundlage der von der Kraftmesseinrichtung erfassten Kontaktpunkte von Drehzentrierteil und Drehgegenstück und/oder der durch Kontakt von Drehzentrierteil und Drehgegenstück auftretenden Kräfte die exakte Winkelposition des Zentrierzapfens ermittelt.

Advantageously, the control device is designed to control the following process steps:

• - by moving the first or second calibration element, the two contours of the rotary centering part and the rotary counterpart are aligned with each other, as long as they are not yet present,
• - the centering pin is moved in a force-controlled manner in the immersion direction relative to the bushing until the centering pin reaches its end position in the bushing,
• - by force-controlled rotation of the first calibration element relative to the second calibration element, the exact angular position of the centering pin is determined on the basis of the contact points of the rotary centering part and the rotary counterpart detected by the force measuring device and/or the forces occurring due to contact between the rotary centering part and the rotary counterpart.

The last two procedural steps, listed by bullet points, can also be carried out in reverse order, depending on the specific design of the system.

Preferably, by comparison with a stored data set, it is checked whether the rotary centering part actually strikes the rotary counterpart and/or whether there is a faulty movement of the first calibration element relative to the second calibration element.

The control device is particularly preferably designed in such a way that it creates or updates a coordinate system or generates correction values for a coordinate system based on the detection of the said contact points and/or occurring forces. For example, at least one previously saved coordinate system in which the robot carries out its movements is shifted on the basis of the measurement results in order to move the robot arm with the tool (or workpiece) it has picked up precisely and repeatedly to a processing position on the basis of the coordinate system newly set or corrected in this way. This at least one coordinate system is corrected at regular intervals, for example, by moving the two calibration elements towards each other using the control device in such a way that the centering pin moves into the bushing (or vice versa) and the rotary centering part is rotated relative to the rotary counterpart.

In an advantageous development of the invention, an RFID chip is provided in the area of or on the first or second calibration element and at least one RFID reading device, preferably also with an RFID transmission function, is provided in the area of or on the second or first calibration element. On the one hand, this can be used to check that original calibration elements are actually being used, and on the other hand, various information can be transmitted to the robot using RFID technology if the robot has at least one RFID reading device. In particular, it is advantageous if information is transmitted from the RFID device in the area of the stationary calibration element to the RFID device of the mobile calibration element. For example, data or complete programs can be transmitted to the robot in this way, particularly if the robot is mobile, the program containing, for example, work instructions for activities to be carried out by the robot at the workstation. After loading the program in the robot, communication can take place via WLAN, for example, with a control system, which initiates the start of the program sequence after positive confirmation of the loaded program. Furthermore, RFID technology can be used to transfer the individual identification number of the respective workstation to the mobile robot so that it knows which station it is at and which program it needs to call up. A protocol about, for example, the duration of work at this workstation, the number of pieces processed, an error list or similar could also be written into the protocol at one or more workstations and then transferred to the robot's RFID reader. If this also has a transmission function, this protocol can be transferred, for example, to the RFID chip that is provided in the area of or on the stationary calibration element.

According to a further development, a camera system is provided to assist in guiding the first or second, movable calibration element to the second or first, stationary calibration element. This is particularly advantageous if the movable calibration element can no longer find the original calibration point, which is determined by the stationary calibration element, on a return journey to the calibration station, which can have various causes. In this case, the camera system, together with the control device evaluating the camera images, can help fen, the calibration element to be brought to the calibration station is to be moved towards the stationary calibration element until the positive guide by the centering pin-socket combination aligns the two calibration elements with each other and then the corrected calibration point can be determined.

The robot can be designed in particular as a movable or mobile robot. Especially with this type of robot, the repeatable, high-precision approach to a work station by the robot has not yet been satisfactorily solved, since the travel movements and the travel distances lead to relatively high deviations in the approach accuracy and processing accuracy. In this case, a movable or mobile robot equipped with the first calibration element measures the coordinates of the stationary calibration station with the second calibration element.

A mobile robot can, for example, be mounted on a driverless transport system (DTS), whereby the calibration element on the robot can be exchanged for a work tool by hand or using an automatic tool changing system. The work tool, for example a finger gripper, is located in the tool holder on the stationary work station. The calibration element with the centering pin can, for example, be carried in the tool holder on the DTS. After calibration, the calibration element with the centering pin is placed in a corresponding holder on the DTS and the finger gripper is picked up on a holder on the work station. Once the work is finished, the finger gripper is placed there again.

According to an alternative, a movable robot is placed on a frame without its own drive, whereby the frame can then be moved manually to the calibration station.

Alternatively, the robot can be set up stationary. In particular, the robot can interact with its first calibration element held on the robot arm with a second calibration element on an automated guided vehicle (AGV) in order to calibrate the robot's working position for the precise approach and processing of workpieces on the AGV. In this case, a stationary robot equipped with the first calibration element measures the coordinates of the AGV with the second calibration element, which now represents the calibration station.

The invention also includes a method according to the corresponding independent method claim. The method according to the invention is preferably carried out by the described calibration tool and the described calibration system, but this does not necessarily have to be the case.

An example of the calibration process is explained below. A first or second calibration element, for example the bushing described above, is arranged on a stationary calibration station, which is preferably located on or near a work station, and the centering pin is arranged on the second or first calibration element. The position of the bushing is preferably taught before calibration so that the control device knows its coordinates. In addition, the centering pin is preferably assigned a pre-position with a small distance to the bushing. When the command comes to search for the position of the bushing, the calibration run begins and the centering pin dips into the bushing. After this has been completed, if necessary after exchanging its calibration element for a work tool using an automatic tool changing system, the robot carries out the work program at the work station. If the robot returns to the calibration station, if necessary after exchanging its work tool for the calibration element using the automatic tool changing system, it can - for example, standing in the pre-position with a maximum tolerance of 40 mm - find the bushing again with a search run and repeat the calibration run. After its completion, a new temporary coordinate system is preferably created or the existing one corrected. This makes it possible to move a robot from one location to another and have it perform new tasks after the calibration run has been performed.

• 1 ein Kalibriersystem mit einem verfahrbaren Roboter;
• 2 ein Kalibriersystem mit einem stationären Roboter;
• 3 eine Seitenansicht eines ersten Ausführungsbeispiels eines ersten Kalibrierelements;
• 4 eine perspektivische Unteransicht des ersten Kalibrierelements der 3;
• 5 eine Unteransicht des ersten Kalibrierelements der 3 und 4;
• 6 eine geschnittene Seitenansicht (entlang A-A der 8) eines ersten Ausführungsbeispiels eines zweiten Kalibrierelements;
• 7 eine perspektivische Draufsicht auf das zweite Kalibrierelement der 6;
• 8 eine Draufsicht des zweiten Kalibrierelements der 6 und 7;
• 9 eine teils geschnittene Seitenansicht eines nicht-lotrechten Eintauchens der ersten in das zweite Kalibrierelement;
• 10 eine teils geschnittene Seitenansicht eines lotrechten Eintauchens der ersten in das zweite Kalibrierelement;
• 11 eine Seitenansicht eines zweiten Ausführungsbeispiels eines ersten Kalibrierelements;
• 12 eine Draufsicht auf das erste Kalibrierelement der 11;
• 13 eine perspektivische Draufsicht auf ein zweites Ausführungsbeispiels eines zweiten Kalibrierelements;
• 14 eine Draufsicht auf das zweite Kalibrierelement der 13;
• 15a-d eine schematische Darstellung der Kalibrierung durch Korrigieren eines Koordinatensystems, und
• 16 eine schematische Darstellung der Kalibrierung durch Korrigieren von mehreren Koordinatensystemen.

The invention is explained below with reference to drawings. They show:

• 1 a calibration system with a movable robot;
• 2 a calibration system with a stationary robot;
• 3 a side view of a first embodiment of a first calibration element;
• 4 a perspective bottom view of the first calibration element of the 3 ;
• 5 a bottom view of the first calibration element of the 3 and 4 ;
• 6 a sectioned side view (along AA of the 8 ) of a first embodiment of a second calibration element;
• 7 a perspective top view of the second calibration element of the 6 ;
• 8 a top view of the second calibration element of the 6 and 7 ;
• 9 a partially sectioned side view of a non-vertical immersion of the first into the second calibration element;
• 10 a partially sectioned side view of a vertical immersion of the first into the second calibration element;
• 11 a side view of a second embodiment of a first calibration element;
• 12 a top view of the first calibration element of the 11 ;
• 13 a perspective top view of a second embodiment of a second calibration element;
• 14 a top view of the second calibration element of the 13 ;
• 15a -d a schematic representation of the calibration by correcting a coordinate system, and
• 16 a schematic representation of calibration by correcting multiple coordinate systems.

In 1 is a calibration system 50 according to the invention with a movable robot and in 2 an inventive calibration system 50 with a stationary robot is shown.

According to the 1 A movable robot 60 is arranged on a chassis 62, which is designed to be self-propelled as a driverless transport system (FTS) and in particular also has its own drive (not shown). The robot 60 is, for example, a 6-axis robot with a robot arm 64, at the free end of which a holder 66 for a first calibration element is provided. According to the 1 the first calibration element 10 is detachably attached to the holder 66 and can preferably be automatically exchanged for a processing tool. The holder 66 is preferably also designed to accommodate at least one processing tool. A corresponding exchange of the first calibration element and processing tool is expediently carried out with a defined spatial relationship, ie it is clearly defined at which spatial coordinates the processing tool is picked up by the holder 66 on the robot arm 64 after the first calibration element 10 has been deposited so that the calibration can be transferred to the processing tool. The same naturally also applies when exchanging the processing tool for the first calibration element 10 if a new calibration is to be carried out.

A second calibration element 30 is arranged on a stationary base 7, which together with the first calibration element 10 on the robot arm 64 forms a calibration tool 1, as will be explained in more detail below. The second calibration element 30 is stationary and its position is not changed for calibration.

The robot 60 has, as an example of a force measuring device, a sensor device 70 with several force and/or moment sensors 72, preferably multi-axis force-moment sensors 72, which are integrated in at least some axes of the robot arm 64 and measure the forces and/or moments that arise when the first calibration element 10 comes into contact with surrounding objects and here in particular with the second calibration element 30. The measured values are made available to a program-controlled control device 80 (see dashed lines from the sensors to the control device 80), which is integrated in the robot 60 (as in 1 shown schematically) or can be arranged externally (as in 2 shown schematically). In particular, the control device 80 controls the robot arm 64 on the basis of the measured values in such a way that the first calibration element 10 is aligned and positioned with respect to the second calibration element 30 in order to determine the exact position and direction in space of the first calibration element 10 based on the second calibration element 30 which is precisely positioned in space.

According to the 2 the robot 60 with the first calibration element 10 is arranged on a fixed substructure 7, while the second calibration element 30 is provided on a driverless transport system 90 (FTS). In this embodiment, workpieces 92 are stored on the FTS 90 in a loading container 94, preferably in an orderly manner, which are processed by a tool which, after exchanging the first calibration element 10, processes the workpieces 92, picks them up and places them again at another location, etc.

In the following, it is explained how a calibration tool 1 with first and second calibration elements 10, 30 as well as a calibration system 50 with such a calibration tool 1 are developed and used for the calibration of a robot 60.

The 3-10 show a first embodiment of a first calibration element 10 with a corresponding second calibration element 30.

In the 3 to 5 a first calibration element 10 of a calibration tool 1 according to the invention is shown in three different views. The 3 shows a calibration element 10 in side view view that 4 in perspective view from below and the 5 in bottom view. The first calibration element 10 comprises a centering pin 12, which is arranged on the underside of a base plate 11 and is designed as a double-stepped double cone. The double cone has surfaces 13a-13d that are stepped relative to one another. The centering pin 12 is rounded at its tip 14. Four holes 15 are provided on its outer contour, distributed around the circumference, through which fastening means (e.g. screws) for fastening the first calibration element 10 to a robot arm 64 (see. 1 and 2 ) can be passed through.

In addition, the first calibration element 10 has a rotary counterpart 22 on the underside of the base plate 11 and laterally offset from the centering pin 12, which in this case is designed as a curved elongated hole 23 that extends over an angular range of approximately 30°. The elongated hole 23 is preferably designed as a blind hole, but can also be an open hole in the base plate 11.

A second calibration element 30 is in the 6 to 8 shown, where 6 a sectional view along AA of the 8 , the 7 a perspective view and the 8 shows a top view. The second calibration element 30 can be used for stationary mounting in a calibration station 5 (see 1 ) so that a fixed starting station is provided for the then movable robot 60, which carries the first calibration element 10. The second calibration element 30 has a base body 34 in which a bushing 32 is arranged that is complementary to the centering pin 12. Accordingly, the bushing 32 is designed as a hollow double cone with a double step. The bushing 32 has an opening 36 at the bottom, from which dirt that would otherwise collect in the bushing 32 can fall.

A rotary centering part 42 with a dowel pin 43 is provided on the top of the base body 34, laterally offset from the bushing 32, which in this case is inserted into a corresponding blind hole in the base body 34. The dowel pin 43 is designed to penetrate into the elongated hole 23 of the first calibration element 10 and to move along the curved contour of the elongated hole 23 by rotating about the longitudinal axis of the centering pin 12, as will be explained in more detail below.

On the circumference of the base body 34, a circumferential projection 35 is provided, in which preferably several boreholes (not shown) are arranged in order to fix the second calibration element 30 to a table or the like, in particular a substructure 7 (see 1 ) using screws, for example. Other fastening options are also possible.

Preferably, both the first and the second calibration element are made in one piece and preferably from stainless steel, although the dowel pin 43 of the rotary centering part 42 can be designed as a separate component (see above), which is also preferably made from stainless steel. The use of other materials is also possible without any problem, for example aluminum or Teflon.

The 8 shows the beginning of an immersion process of the first calibration element 10 into the second calibration element 30. It can be seen that the longitudinal axis L of the centering pin 12 runs at an angle of approximately 15° to the immersion direction f1, which is perpendicular here. In this position, it is inevitable that the first calibration element 10 abuts the second calibration element 30, in this case at a contact point designated K, and possibly slides along it for at least a short distance. The sensors 72 in the axes of the robot arm 64 register the force resulting from the contact and accordingly control the further immersion of the first calibration element 10 into the second calibration element 30, with the further contacts between the two calibration elements 10, 30 also being correspondingly detected and used to control the first calibration element 10.

The 9 shows how the first calibration element 10 dips vertically into the second calibration element 30 in the immersion direction f1, after it has been inserted, for example, as in the 8 shown from an inclined position into this vertical position. It is shown how the dowel pin 43 is positioned above the slot 23 and engages when the first calibration element 10 is inserted into the slot 23. If the slot 23 is not above the dowel pin 43, the first calibration element 10 is rotated about the insertion direction f1, here synonymous with the rotation axis L of the centering pin 12 and the z-axis in space, about the rotation direction f2 (see double arrow). In this case, the rotary centering part 42 or the dowel pin 43 touches a first contact surface 22a of the rotary counterpart 22 (see also 4 and 5 ) and slides along this first contact surface 22a when the first calibration element 10 is rotated, until the rotary centering part 42 or the dowel pin 43 is located below the rotary counterpart 22 or the slot 23. The first calibration element 10 can then be lowered so that the centering pin 12 can assume its final position in the bushing 32, with the dowel pin 43 simultaneously being laterally enclosed by the slot 23. In this final position the centering pin 12 has reached its positively guided end position, in which its tip 14 is in a defined position in relation to the spatial coordinates x, y and z. This design ensures that the rotary centering part 42 in the retracted state can actually interact with the rotary counterpart 22 when the first calibration element 10 rotates, even if it initially only hits the first contact surface 22a of the rotary counterpart 22, but is then guided into the inserted state.

The first calibration element 10 is then rotated about the rotational or longitudinal axis L of the centering pin 12 (see double arrow f2), so that the dowel pin 43 first comes into contact with one end 23b or 23c of the elongated hole 23 and then with the other end 23c or 23b of the elongated hole 23. These contacts and/or the forces occurring during these contacts are measured with the sensor device 70 and passed on to the control device 80. The control device 80 determines a calibration point from the measurement results, based on the coordinated geometries of the centering pin 12 and bushing 32 and the angular positions of the elongated hole 23 in relation to the dowel pin 43. This calibration point may be different from the calibration point determined during a previous calibration. The newly determined calibration point is then determined here, preferably by shifting or otherwise correcting the coordinate system.

Furthermore, the control device 80 can determine from the measurement results whether a faulty run of the first calibration element 10 has occurred.

In a further development, for example, on the opposite side of the dowel pin 43 and also protruding from the projection 35, a support pin (not shown) can be arranged, which ends at the same height as the dowel pin 43, but is preferably arranged radially further outwards (alternatively further inwards) than the dowel pin 43. The base plate 11 comes into contact with the support pin when the first calibration element 10 is immersed, as well as against the dowel pin 43 when the elongated hole 23 is aligned with the dowel pin 43. The load of the base plate 11 is then distributed both over the dowel pin 43 and over the support pin, so that the dowel pin 43 is prevented from being subjected to too much stress. So that the support pin does not get in the way of the elongated hole 23 being retracted when the elongated hole 23 is above the dowel pin 43, another curved elongated hole (not shown) is provided in the base plate 11, which is arranged opposite the elongated hole 23. The elongated hole for the support pin, which also runs at a larger (alternatively smaller) radial distance from the longitudinal axis of the bushing 32 than the elongated hole 23, expediently extends over a larger angular range than the elongated hole 23. This design ensures that the support pin actually only serves to absorb the load and does not influence the calibration or cause an incorrect measurement.

In the 11-14 A second embodiment of a first calibration element 10 with a corresponding second calibration element 30 is shown. The 11 and 12 show the first calibration element 10 in side view and top view, respectively, while the 13 and 14 show the second calibration element 30 in perspective and frontal plan view. Identical or at least comparable elements of this second embodiment are provided with the same reference numerals as in the first embodiment.

The main difference between the two embodiments is the different design of the rotary centering part 42 and the rotary counterpart 22. According to the 13 and 14 the rotary centering part 42 comprises a pin-shaped first projection 46 and a pin-shaped second projection 47, which are provided in the projection 35 and protrude perpendicularly from it. The two projections 46, 47 are arranged on the same circumferential circle, i.e. at the same distance from the longitudinal axis of the bushing 32. In the example shown, they cover an angular range W of approximately 90°, whereby this angular range is in no way to be understood as restrictive.

A rotary counterpart 22 is provided on the edge of the base plate 11 of the first calibration element 10, which has a pin-shaped projection 26 protruding in the radial direction. This comes into contact with the projection 35 of the second calibration element 30 after the centering pin 12 has been immersed in its end position, and this contact is detected by the sensors 72. The centering pin 12 is then rotated about its longitudinal axis L until the projection 26 comes into contact with the first or second projection 46, 47, and is then rotated in the opposite direction until it strikes the second or first projection 47, 46 (see double arrow f3 in 12 ). These contacts are detected by the sensors 72 due to the change in force at the stop, so that the control device 80 can determine the exact angular position of the first calibration element 10.

If the projection 26 enters the 270° angle range between the two projections 46, 47 and rests against the projection 35 there, the same applies, ie the first calibration element 10 is first pushed against the one projection 46, 47 until the projection 26 stops and then in the opposite direction tion until it stops against the other projection 47, 46.

If, however, the projection 26 comes to rest on the first or second projection 46, 47 when the centering pin 12 is inserted into the bushing 32, this contact is registered by the sensors 72, which then cause the control device 80 to rotate the first calibration element 10 in order to then attempt to continue the immersion process. If this further immersion is successful, the projection 26, in the end position of the centering pin 12 in the bushing 32, comes to rest on the projection 35 as described above, whereupon the two projections 46, 47 are approached by rotation. If, however, the centering pin 12 cannot be inserted further into the bushing 32 with the projection 26, which is again registered by the sensors 72, the centering pin 12 is already in its end position in the bushing 32.

In 15a -d shows the schematic sequence of a calibration according to the present invention. A robot 60, which can be moved for example, determines an original calibration point in a coordinate system at a calibration station 5 by means of a calibration tool 1 according to the invention, advantageously by approaching it several times in order to achieve a higher precision ( 15a) . This process is also known as teaching. This original calibration point is stored in a program-controlled control device 80. Based on this original calibration point, the coordinates of a working point at a processing station of the robot 60 are communicated to the robot 60, which the movable robot 60 - equipped with a corresponding tool - moves to in order to carry out processing steps ( 15b) . At regular and/or irregular intervals or when caused by an event (e.g. unintentional displacement of the robot 60 or after a collision or similar), the robot 60 returns to the calibration station 5 and determines there, if necessary, a new calibration point that differs from the original calibration point and is thus displaced ( 15c ), namely by means of the forced guidance of the centering pin 12 and bush 32 as well as the angle determination with the rotary centering part 42 and rotary counterpart 22. This new calibration point is then used to calculate a new working point so that the robot 60 can then continue the processing precisely at the processing station to which it returns after the calibration ( 15d ). The original coordinate system is shifted by the change from the original to the new calibration point. In the 15c the original coordinate system is shown in dashed lines and the shifted coordinate system with the new, corrected calibration point is shown in solid lines. In 15d The coordinate system with the original operating point is shown in dashed lines and the coordinate system shifted according to the calibration is shown in solid lines.

The invention enables calibration in which, in addition to the three spatial coordinates x, y, z, which are determined by assuming the forced end position of the centering pin 12 in the bushing 32, the angles in space (represented by rotation vectors rx, ry, rz) can also be determined repeatedly. The three rotation vectors are determined by means of the rotary centering part 42 and the rotary counterpart 22, whereby preferably two of the three rotation vectors are already determined by determining the rotary centering part 42 or the rotary counterpart 22 and the third rotation vector is determined by rotating the rotary centering part 42 relative to the rotary counterpart 22. The six coordinates are determined again during calibration and used to correct coordinate systems when the centering pin 12 is in its end position.

Based on the 16 It is clear that there can be several coordinate systems in the working area of a robot 60. In the control software of the control device 80, the operator can select whether several and which coordinate systems should be taken into account. In the 16 Three coordinate systems are shown, each of which contains one or more work points for the robot 60. All three original coordinate systems (shown in dashed lines) are shifted according to the correction of the original calibration point and also partially rotated (shown in solid lines) in order to illustrate the flexibility of the calibration system for approaching various work stations distributed in the room after calibration.

The invention is not limited to the embodiments described. For example, the roles of the first and second calibration elements can be swapped in the figures, so that a bushing 32 is provided on the first calibration element 10 and extends into a centering pin 12 on the second, stationary calibration element 30.

Furthermore, the first or the second calibration element 10, 30 can comprise not only one centering pin 12, but several, and accordingly the second or the first calibration element 30, 10 can comprise one or more bushings 32. A combination of pins 12 and bushings 32 in the first or second calibration element 10, 30 is also possible with a corresponding design of the second or first calibration element 30, 10 is possible. Furthermore, the rotary centering part 42 and the rotary counterpart 22 can have other configurations than the dowel pin 43 and the curved slot 23.

list of reference symbols

1

calibration tool

5

calibration station

7

substructure

10

first calibration element

11

base plate

12

centering pin

13a-d

surfaces

14

Great

15

drilling

22

rotating counterpart

22a

first contact surface

23

slot

26

projection

23b,c

ends of the slot

30

second calibration element

32

socket

33a-d

surfaces

34

base body

35

overhangs

36

opening

42

rotary centering part

43

dowel pin

46

first lead

47

second lead

50

calibration system

60

robot

62

chassis

64

robot arm

66

bracket

70

sensor device

72

sensors

80

control device

90

driverless transport system

92

workpieces

94

assembly container

L

longitudinal axis of the centering pin

K

contact point

f1

immersion direction

f2

direction of rotation

f3

direction of rotation

W

angular range

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• JP 5337856 A [0003]
• EP 2328724 A1 [0004]

Claims (25)

Calibration tool (1) for the independent calibration of a robot (60) for the repeated, high-precision locating of one or more different processing positions of the robot (60), wherein the calibration tool (1) comprises: a first calibration element (10) which is designed to be arranged on a robot arm (64) of a mobile or stationary robot (60), and a second calibration element (30) which is designed to be arranged on a stationary or mobile calibration station (5), wherein the first or the second calibration element (10, 30) comprises a centering pin (12), and wherein the second or the first calibration element (30, 10) comprises a bushing (32) contoured complementarily to the centering pin (12), wherein the centering pin (12) is designed to be immersed in an immersion direction (f1) into the bushing (32) up to an end position, and wherein the first or the second calibration element (10, 30) a rotary centering part (42) arranged laterally of the centering pin (12) or the bushing (32), which interacts with a rotary counterpart (22) arranged on the second or first calibration element (30, 10) by rotating about the immersion direction (f1) in order to determine the rotary position of the first or second calibration element (10, 30) from these rotary movements of the first or second calibration element (10, 30). Calibration tool (1) after claim 1 , characterized in that the rotary centering part (42) and the rotary counterpart (22) are arranged spatially separated from the centering pin (12) and the bushing (32). Calibration tool (1) after claim 1 , characterized in that the rotary centering part (42) comprises a projection which projects outwards at an angle relative to the longitudinal axis (L) of the centering pin (12) and that the rotary counterpart (22) comprises at least two projections, wherein the projection of the rotary centering part (42) in the end position of the centering pin (12) in the bushing (32) can be rotated between the two projections of the rotary counterpart (22) and can thereby strike against these two projections. Calibration tool (1) after claim 1 , characterized in that the rotary centering part (42) is arranged on the centering pin (12) or the bushing (32) and the rotary counterpart (22) is arranged on the inner wall of the bushing (32) or the outer wall of the centering pin (12). Calibration tool (1) according to one of the preceding claims, characterized in that the rotary centering part (42) and the rotary counterpart (22) are designed such that the rotary centering part (42) can touch a first contact surface (22a) of the rotary counterpart (22) when the centering pin (12) is immersed in the bushing (32) and can slide along this first contact surface (22a) by rotating the first or second calibration element (10, 30) about the immersion direction (f1) until the rotary centering part (42) can immerse into the rotary counterpart (22) by moving the first or second calibration element (10, 30) in the immersion direction (f1). Calibration tool (1) according to one of the preceding claims, characterized in that the rotary centering part (42) comprises at least one dowel pin (43) and the rotary counterpart (22) comprises a curved elongated hole (23). Calibration tool (1) according to the preceding claim, characterized in that the elongated hole (23) extends in a direction which is perpendicular to the immersion direction (f1). Calibration tool (1) according to one of the two preceding claims, characterized in that the dowel pin (43) can be immersed in the elongated hole (23) by moving the first or second calibration element (10, 30) in the immersion direction (f1) and can come to rest on both ends (23b, 23c) of the elongated hole (23) by rotating the first or second calibration element (10, 30) about the immersion direction (f1) in order to determine the rotational position of the first or second calibration element (10, 30) therefrom. Calibration tool (1) according to one of the preceding claims, characterized in that the centering pin (12) has a side surface contour that is non-linear in a side view. Calibration tool (1) according to one of the preceding claims, characterized in that the centering pin (12) is stepped, preferably double-stepped, particularly preferably as a double-stepped cone. Calibration tool (1) according to one of the preceding claims, characterized in that the circumferential contours of the centering pin (12) and the bushing (32) are rotationally symmetrical. Calibration tool (1) according to one of the preceding claims, characterized in that the bushing (32) has a downwardly directed opening (36). Calibration system (50) with a calibration tool (1) according to one of the preceding claims, characterized in that the calibration system (50) comprises a robot (60) with a robot arm (64), wherein a holder (66) for the first or the second calibration element (10, 30) and a holder for a tool or workpiece are provided on the robot arm (64), wherein the holders are preferably identical, wherein the robot arm (64) is designed to be force-controlled, for which purpose a force measuring device, preferably designed as a sensor device (70) with force and/or torque sensors (72) and these preferably designed as multi-axis force-torque sensors (72), is provided on the robot arm (64), wherein the calibration system (50) further comprises a computer-controlled control device (80) which receives and processes measured values of the force measuring device, and wherein the control device (80) is designed such that it controls the immersion of the centering pin (12) in the bushing (32) and the relative movement of the rotary centering part (42) and the rotary counterpart (22) controls, wherein the force measuring device detects the contact points of the centering pin (12) and the bushing (32) and/or the forces occurring through contact between the centering pin (12) and the bushing (32) as well as the contact points of the rotary centering part (42) and the rotary counterpart (22) and/or the forces occurring through contact between the rotary centering part (42) and the rotary counterpart (22). Calibration system (50) according to the preceding claim, characterized in that the control device (80) is designed to control the following method steps: - by moving the first or second calibration element (10, 30), the two contours of the rotary centering part (42) and rotary counterpart (22) are brought into alignment with one another, as long as they are not yet present, - the centering pin (12) is moved in a force-controlled manner in the immersion direction (f1) relative to the bushing (32) until the centering pin (12) reaches its end position in the bushing (32), - by force-controlled rotation of the first calibration element (10, 30) relative to the second calibration element (10, 30), the exact angular position of the centering pin (12) is determined. Calibration system according to one of the preceding system claims, characterized in that the control device (80) is further designed to control the method step of checking, by comparison with a stored data set, whether the rotary centering part (42) actually strikes the rotary counterpart (22) and/or whether an incorrect travel has occurred. Calibration system (50) according to one of the preceding system claims, characterized in that the control device (80) is designed such that, based on the detection of said contact points and/or occurring forces, it creates or updates a coordinate system or generates correction values for a coordinate system on the basis of which the robot arm (64) moves a tool picked up by it to a processing position, wherein the coordinates of the processing position are stored in an electronic memory and can be called up by the control device (80). Calibration system (50) according to one of the preceding system claims, characterized in that an RFID chip is provided in the region of or on the first or second calibration element (10, 30) and at least one RFID reading device is provided in the region of or on the second or first calibration element (30, 10). Calibration system (50) according to one of the preceding system claims, characterized in that a camera system is provided for assisting in guiding the first or second calibration element (10, 30) to the second or first calibration element (30, 10). Calibration system (50) according to one of the preceding system claims, characterized in that the robot (60) with the first calibration element (10) is designed to be movable, for example by being arranged on a mobile chassis (62), and that the second calibration element (30) is arranged stationary. Calibration system (50) according to one of the preceding system claims except for the immediately preceding one, characterized in that the robot (60) with the first calibration element (10) is set up stationary, and that the second calibration element (30) is arranged on a driverless transport system (90). Method for the independent calibration of a mobile or stationary robot (60) for the repeated high-precision locating of one or more different processing positions of the robot (60), in particular by means of a calibration system (50) according to one of the preceding system claims, wherein the method comprises the following steps: - a first calibration element (10) is provided which is designed to be arranged on a robot arm (64) of the mobile or stationary robot (60); - a second calibration element (30) is provided which is designed to be arranged on a stationary or mobile calibration station (5) wherein the first or the second calibration element (10, 30) comprises a centering pin (12) and the second or the first calibration element (30, 10) comprises a bushing (32) contoured complementarily to the centering pin (12); - a rotary centering part (42) provided on the first or second calibration element (10, 30) to the side of the centering pin (12) and a rotary counterpart (22) arranged on the second or first calibration element (30, 10) are provided; - the first calibration element (10) is moved into the second calibration element (30) in an immersion direction (f1) by force-controlled movement of the robot arm (64), using a force measuring device arranged on the robot arm (64), preferably designed as a sensor device (70) with several force and/or moment sensors (72) and these advantageously designed as force-moment sensors (72); - after this or beforehand, the first or second calibration element (10, 30) is rotated about the immersion direction (f1) and the rotational position of the first or second calibration element (10, 30) is determined from the contact between the rotary centering part (42) and the rotary counterpart (22); - a control device (80) controls the immersing relative movement of the centering pin (12) to the bushing (32) and the rotation of the first or second calibration element (10, 30) about the immersion direction (f1) on the basis of the following measured variables recorded by the force measuring device: - contact points of the centering pin (12) and bushing (32) and/or the forces occurring through contact between the centering pin (12) and bushing (32); and - contact points of the rotary centering part (42) and rotary counterpart (22) and/or the forces occurring through contact between the rotary centering part (42) and rotary counterpart (22). Method according to the preceding method claim, characterized in that it further comprises the following method steps: - when the rotary centering part (42) touches a first contact surface (22a) of the rotary counterpart (22) when the centering pin (12) is immersed in the bushing (32), it is guided in a sliding manner along this first contact surface (22a) by rotating the first or second calibration element (10, 30) about the immersion direction (f1) until the rotary centering part (42) can immerse into the rotary counterpart (22) by moving the first or second calibration element (10, 30) in the immersion direction (f1). Method according to one of the preceding method claims, characterized in that it further comprises the following method steps: - the rotary centering part (42) comprises a dowel pin (43) and the rotary counterpart (22) comprises a curved elongated hole (23); - under the control of the control device (80), the robot arm (64) with the first or second calibration element (10, 30) is moved in such a way that, if not already present, the two contours of the dowel pin (43) and the elongated hole (23) are brought into alignment; - under the control of the control device (80), the centering pin (12) is moved in a force-controlled manner relative to the bushing (32) in the immersion direction (f1) until the centering pin (12) reaches an end position in the bushing (32); - under the control of the control device (80), the first calibration element (10) is rotated relative to the second calibration element (30) on the basis of the contact points of the dowel pin (43) and the elongated hole (23) detected by the force measuring device and/or the forces occurring due to contact between the dowel pin (43) and the elongated hole (23) until the dowel pin (43) stops at at least one, preferably both ends of the elongated hole (23), thus determining the exact angular position of the first or second calibration element (10, 30); - by comparing this angular position with a stored data set, it is checked whether the centering pin (12) has actually been moved into the bushing (32) of the calibration system and/or whether an incorrect travel has occurred. Method according to one of the preceding method claims, characterized in that the control device (80) creates or updates a coordinate system based on the detection of the said contact points and/or occurring forces or generates correction values for a coordinate system on the basis of which the robot arm (64) moves a tool picked up by it to a processing position, wherein the coordinates of the processing position are stored in an electronic memory and can be called up by the control device (80). Method according to one of the preceding method claims, characterized in that the centering pin (12) is provided in a stepped configuration, preferably in two stages, particularly preferably as a double-stepped cone.

Images