Method for calibrating a light section sensor, and associated robot system
Patent Information
- Application Number
- EP2024706035
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-03-03
- Filing Date
- 2024-02-15
- Publication Date
- 2026-01-14
AI Technical Summary
Existing methods for calibrating light section sensors attached to robot kinematics require manual intervention and do not allow for automatic conversion of sensor coordinates to a reference coordinate system, limiting their accuracy and efficiency in manufacturing processes.
A method for automatically calibrating a light section sensor by moving it along different routes parallel to line features on a calibration object, recording intersection points, and storing positions in the robot coordinate system to determine a transformation matrix for converting sensor coordinates to the reference coordinate system, eliminating the need for manual action.
Enables automatic and precise calibration of light section sensors, improving their accuracy and efficiency in manufacturing processes by allowing for the conversion of sensor values from the sensor coordinate system to the reference coordinate system without manual intervention.
Smart Images
Figure EP2024053862_12092024_PF_FP_ABST
Abstract
Description
[0001] Method for calibrating a light section sensor and associated robot system
[0002] The invention relates to a method for calibrating a light-section sensor with respect to a member of a robot kinematic system controllable by a robot control device, comprising a plurality of members and joints that adjustably connect the members, wherein the light-section sensor is attached to one member. The invention also relates to an associated robot system.
[0003] EP 1 931 503 B1 describes a method for determining the position of a virtual tool center point with respect to a known coordinate system of a robot with a robot arm, wherein firstly the position difference between a feature of a reference component and the virtual tool center point is determined, then the robot arm is moved until the coordinates of the feature of the reference component and the virtual tool center point match, and then by determining the robot axis positions for this position of the virtual tool center point the position of the virtual tool center point in the robot coordinate system is determined.
[0004] The object of the invention is to create a method for calibrating a light section sensor that can automatically determine a sufficient number of positions from which a transformation matrix can be determined in order to automatically convert position values between a sensor coordinate system of the light section sensor and a reference coordinate system of the robot kinematics. The object is achieved by a method for calibrating a light section sensor with respect to a member of a robot kinematics that can be controlled by a robot control device and has several members and joints that adjustably connect the members, wherein the light section sensor is attached to one member, comprising the steps:
[0005] - Providing a calibration object with a first line feature and a second line feature different from the first line feature on a base surface in a pose known to the robot control device,
[0006] - Recording an intersection point of the first line feature and the second line feature by means of a teach-in method and storing the position of the intersection point in the robot coordinate system in the robot control device,
[0007] - Automatically moving the light section sensor at a first height along a first path parallel to the first line feature towards the second line feature of the calibration object until the projected line meets the second line feature of the calibration object, and storing the current position of a predetermined reference point of the robot kinematics in the robot coordinate system as a first calibration position,
[0008] - Automatically moving the light section sensor along a second path parallel to the first line feature, which is different from the first path, towards the second line feature of the calibration object until the projected line meets the second line feature of the calibration object, and storing the current position of the predetermined reference point of the robot kinematics in the robot coordinate system as a second calibration position, and
[0009] - Automatically moving the light section sensor at a second elevation different from the first elevation along a third distance parallel to the first line feature, which is different from the first distance and the second distance, towards the second line feature of the calibration object until the projected line meets the second line feature of the calibration object, and storing the current position of the predetermined reference point of the robot kinematics in the robot coordinate system as a third calibration position.
[0010] Robot systems are used in automated manufacturing to automatically perform a wide variety of different manufacturing processes. Robot systems consist of at least one robot kinematics, such as a robot arm, which is automatically controlled by a robot control device, i.e. the joint positions of the robot kinematics can be automatically adjusted. With such robot systems and the specifically associated tools that are automatically guided by the robot kinematics, for example, weld seams can be created, adhesive beads can be applied, or sealants can be applied to a workpiece via a nozzle guided by the robot kinematics.The desired path along which a reference point of a tool guided by the robot kinematics, such as a welding gun tip, a glue nozzle, or a dispensing nozzle, is to move automatically can be stored in the robot controller. A robot program can call up the stored path to automatically guide the corresponding tool along the desired path using the robot controller by automatically adjusting the joints of the robot kinematics.
[0011] Since each individual workpiece can have certain deviations in its actual shape from its ideal shape, it is often not sufficient for the saved path, which represents a target path, to be followed in the same way for each individual workpiece. For this reason, what is known as seam tracking is implemented. This includes an optical sensor that is preferably attached to a flange of the robot kinematics and that, while the tool is moving along the desired path, optically detects a feature of the workpiece assigned to the path so that this feature can be evaluated by the robot control device. The feature on the workpiece can, for example, be the butt between two components that are to be joined by means of a weld seam.The feature on the workpiece can, for example, also be a groove or an edge on a workpiece along which an adhesive bead or a sealing bead is to be applied.
[0012] The optical sensor detects the feature on the workpiece at every moment of the tool's movement along the target path and detects any deviations in the pose of the tool with respect to the feature on the workpiece. The robot control device is designed and configured to automatically move the tool guided by the robot kinematics along an actual path that deviates from the target path based on deviations that were detected by the optical sensor. In such a case, the actual path is then modified from the stored target path in accordance with the deviations present in the individual case of a workpiece and the tool is automatically moved accordingly by the robot kinematics.
[0013] The characteristic according to which the robot control device is designed means that the robot control device is constructed in this specific way. The characteristic according to which the robot control device is set up means that the robot control device is programmed in this specific way by means of a program or software.
[0014] The optical sensor suitable for this type of seam tracking is also called a light-section sensor. A light-section sensor typically comprises a laser light source and an optical system that expands the generated laser light into a flat fan beam or, using a beam deflection unit, continuously deflects a laser beam within a predetermined angular range in order to repeatedly cover this angular range. This allows an optical line to be projected onto the respective workpiece.
[0015] The projected line can be captured and evaluated by an optical camera. The optical camera is usually combined with the laser light source in a common device of the light section sensor. The light section sensor as a standalone sensor device can be mounted on a link of the robot kinematics, in particular on a
[0016] Tool flange of the robot kinematics.
[0017] Typically, the sensor values, i.e., the recorded position values of the light-section sensor, are provided relative to a sensor coordinate system. The path to be followed by the tool, automatically guided by the robot kinematics, is usually in the form of support points, which are available or stored as position values in a robot coordinate system.
[0018] The robot coordinate system can generally be placed at any point in the robot kinematics.
[0019] Typically, a basic robot coordinate system is placed in the proximal base link, such as the base frame of the robot kinematics. This means that the position and orientation of the robot coordinate system remain the same in all possible axis positions or poses of the robot kinematics. This robot coordinate system can also be referred to as the base coordinate system. The light section sensor is generally attached to the last, distal end link of the robot kinematics. This distal end link of the robot kinematics can also be referred to as the flange or tool flange. Since the tool to be handled by the robot kinematics, such as a welding tool, is usually attached there, it is then also expedient to attach the light section sensor there.It is usually practical to attach the light section sensor to this link, although the light section sensor can generally also be attached to any other link in the robot kinematics. In both cases it is also useful to place a separate reference coordinate system in the link to which the light section sensor is to be attached or is attached. This reference coordinate system can then also be referred to as a flange coordinate system or hand coordinate system, depending on the case. The reference coordinate system selected in each specific case should be defined in such a way that when the light section sensor is attached its position and orientation with respect to the sensor coordinate system no longer changes, i.e. it is fixed, even if the joints of the robot kinematics are adjusted, i.e. the robot kinematics are moved.
[0020] In order for the sensor values acquired by the guided light-section sensor to be correctly evaluated, they must be converted from the sensor coordinate system in which they are located into the specific reference coordinate system. Such a conversion can be performed, for example, using a transformation matrix. However, the transformation matrix depends on the exact position and attitude (pose) of the light-section sensor, i.e., the sensor device relative to the link in the robot kinematics to which the light-section sensor or sensor device is attached.
[0021] Therefore, after the light section sensor has been mounted for the first time on the relevant link of the robot kinematics, the light section sensor must be calibrated with respect to the robot kinematics.
[0022] For this purpose, at least three different positions of the light-section sensor must be assumed with respect to a calibration object, and the corresponding position values must be recorded in each of these positions. From the at least three position values obtained, a transformation matrix can be calculated, which allows a computational transformation between the sensor coordinate system of the light-section sensor and the reference coordinate system of the robot kinematics. According to the invention, the recording of such at least three different positions for calibration should be able to take place automatically, so that no manual intervention by a person is necessary.
[0023] The task mentioned at the beginning is therefore solved by :
[0024] - Providing a calibration object with a first line feature and a second line feature different from the first line feature on a base surface in a pose known to the robot control device,
[0025] - Recording an intersection point of the first line feature and the second line feature by means of a teach-in method and storing the position of the intersection point in the robot coordinate system in the robot control device,
[0026] - Automatically moving the light section sensor at a first height along a first path parallel to the first line feature towards the second line feature of the calibration object until the projected line meets the second line feature of the calibration object, and storing the current position of a predetermined reference point of the robot kinematics in the robot coordinate system as a first calibration position,
[0027] - Automatically moving the light section sensor along a second path parallel to the first line feature, which is different from the first path, towards the second line feature of the calibration object until the projected line meets the second line feature of the calibration object, and storing the current position of the predetermined reference point of the robot kinematics in the robot coordinate system as a second calibration position, and
[0028] - Automatically moving the light section sensor at a second elevation different from the first elevation along a third distance parallel to the first line feature, which is different from the first distance and the second distance, towards the second line feature of the calibration object until the projected line meets the second line feature of the calibration object, and storing the current position of the predetermined reference point of the robot kinematics in the robot coordinate system as a third calibration position.
[0029] With regard to the provision of the calibration object, the calibration object can be a body of largely any design, provided that it has at least a first line feature and a second line feature. The first line feature and the second line feature can be formed, for example, by outer edges, inner edges, steps, scribe lines, grooves and / or flutes on the calibration body. The calibration object can be placed on a flat surface of a machining table. The machining table can, for example, comprise clamping devices designed to hold a workpiece firmly during its machining by the robot system. The calibration body itself can be calibrated in its assumed position before the start of the further method steps, i.e. the position and orientation of the calibration body with respect to the robot coordinate system is known to the robot system.For example, position and attitude values of the calibration body can be stored in the robot control device of the robot system.
[0030] The intersection point of the first line feature and the second line feature is then recorded using a teach-in process and the position of the intersection point is stored in the robot coordinate system in the robot control device.
[0031] It should also be mentioned here that the light section sensor must of course be attached to the link of the robot kinematics before starting the further process steps.
[0032] The light section sensor is moved in particular in a central alignment along the first line feature, automatically controlled by the robot kinematics and the robot control device, in a second direction. The second direction is aligned perpendicular to the light fan stretched onto the laser light emitted by the light section sensor. The light section sensor is moved in this second direction until the projected line of the light section sensor hits the second line feature of the calibration object. At this moment the current position of the light section sensor is stored in the robot control device in the form of position values in the robot coordinate system as a position in the second direction. This stored second position then forms a second calibration position. This second calibration position is also determined automatically, as is the case with the first calibration position.
[0033] The procedure for automatically determining the third calibration position can essentially correspond to the procedure for automatically determining the first calibration position or the second calibration position, wherein the automatic determination takes place, for example, in a second altitude of the light section sensor that differs from the first altitude.
[0034] In a further development of the method, the automatic movement of the light section sensor in the first height position along the first path parallel to the first line feature towards the second line feature of the calibration object can be carried out starting from a first starting position which is obtained by the following steps:
[0035] - Pre-positioning the light section sensor with respect to the calibration object at the first height with respect to the calibration object by controlled adjustment of the joints of the robot kinematics controlled by the robot control device such that a line projected by the light section sensor lies outside the first line feature of the calibration object,
[0036] - Automatically moving the light section sensor at the first height position in a first direction parallel to the projected line towards the first line feature of the calibration object until the projected line meets the first line feature of the calibration object, and storing the current position of the predetermined reference point of the robot kinematics in the robot coordinate system as a first position in the first direction,
[0037] - Automatically moving the light section sensor in the first direction parallel to the projected line over the first line feature of the calibration object while maintaining the first elevation until the projected line leaves the first line feature of the calibration object again, and storing the current position of the predetermined reference point of the robot kinematics in the robot coordinate system as a second position in the first direction,
[0038] - Automatically determining a first intermediate position in the first direction that lies between the stored first position and the stored second position, and using the first intermediate position as the first start position.
[0039] In an alternative and supplementary development of the method, the automatic movement of the light section sensor along the second path parallel to the first line feature towards the second line feature of the calibration object can be carried out starting from a second starting position which is obtained by the following steps:
[0040] - Pre-positioning the light section sensor with respect to the calibration object at a specific altitude, which may in particular be the first altitude or the second altitude, with respect to the calibration object by controlled adjustment of the joints of the robot kinematics controlled by the robot control device such that a line projected by the light section sensor lies outside the first line feature of the calibration object,
[0041] - Automatically moving the light section sensor at the specific height in a first direction parallel to the projected line towards the first line feature of the calibration object until the projected line meets the first line feature of the calibration object, and storing the current position of the predetermined reference point of the robot kinematics in the robot coordinate system as a third position in the first direction,
[0042] - Automatically moving the light section sensor in the first direction parallel to the projected line over the first line feature of the calibration object while maintaining the first elevation until the projected line leaves the first line feature of the calibration object again, and storing the current position of the predetermined reference point of the robot kinematics in the robot coordinate system as a fourth position in the first direction,
[0043] - Automatically determining a second intermediate position in the first direction, which lies between the stored third position and the stored fourth position, and using the second intermediate position as the second starting position. The pre-positioning of the light section sensor with respect to the calibration object at a first height relative to the calibration object by controlled adjustment of the joints of the robot kinematics controlled by the robot control device can be carried out in such a way that a line projected by the light section sensor initially lies outside the first line feature of the calibration object.
[0044] Pre-positioning can be carried out by a person controlling and moving the robot kinematics, for example by means of a robot hand control device, in such a way that the light section sensor assumes a corresponding position and orientation.
[0045] A main optical axis of the light section sensor can, for example, be aligned perpendicular to the plane of the surface of the machining table and / or perpendicular to a surface of the calibration object. The light section sensor projects a line onto the surface of the machining table, or later also onto the surface of the calibration object. The projected line then corresponds to the measuring field or measuring line along which the optical detection device of the light section sensor can record the reflections of the emitted laser light.
[0046] The light section sensor is then automatically moved toward the calibration object parallel to the projected line or in the direction of the projected line. The robot control device automatically adjusts the joints of the robot kinematics in order to move the guided light section sensor accordingly. The height of the light section sensor with respect to the surface of the processing table and / or the calibration object, i.e. the distance of the light section sensor in height from the surface of the processing table and / or from the calibration object, remains constant.
[0047] In a further, alternative and supplementary development of the method, the automatic movement of the light section sensor along the third path parallel to the first line feature towards the second line feature of the calibration object can be carried out starting from a third starting position which is obtained by the following steps:
[0048] - Pre-positioning the light section sensor with respect to the calibration object at a further altitude, which can in particular be a third altitude different from the first altitude and the second altitude, with respect to the calibration object by controlled adjustment of the joints of the robot kinematics controlled by the robot control device such that a line projected by the light section sensor lies outside the first line feature of the calibration object,
[0049] - Automatically moving the light section sensor at the further elevation in a first direction parallel to the projected line toward the first line feature of the calibration object until the projected line meets the first line feature of the calibration object, and storing the current position of the predetermined reference point of the robot kinematics in the robot coordinate system as a fifth position in the first direction, - Automatically moving the light section sensor further in the first direction parallel to the projected line beyond the first line feature of the calibration object while maintaining the further elevation until the projected line leaves the first line feature of the calibration object again, and storing the current position of the predetermined reference point of the robot kinematics in the robot coordinate system as a sixth position in the first direction,
[0050] - Automatically determining a third intermediate position in the first direction which is between the stored fifth position and the stored sixth position, and using the third intermediate position as the third start position.
[0051] Accordingly, the light section sensor is automatically moved at a first elevation in a first direction parallel to the projected line toward the first line feature of the calibration object until the projected line encounters the first line feature of the calibration object. As soon as the projected line encounters the first line feature of the calibration object, the current position of the light section sensor is stored at that moment in the form of position values in the robot coordinate system as a first position in the first direction in the robot control device.
[0052] The light section sensor is then automatically moved in the first direction parallel to the projected line, past the first line feature of the calibration object, while maintaining the first elevation, until the projected line leaves the first line feature of the calibration object. As soon as the projected line leaves the first line feature of the calibration object, the current position of the light section sensor is stored in the robot controller in the form of position values in the robot coordinate system as a second position in the first direction.
[0053] The stored position values of the first position and the stored position values of the second position are both in the robot coordinate system.
[0054] Now, from the stored position value of the first position and the stored position value of the second position, an intermediate position can be determined that lies on a distance between these two positions. The intermediate position should preferably be close to the planned operating point of the tool. The operating point can, for example, be a center point of a welding gun tip, a glue nozzle, or an application nozzle. The intermediate position is stored as a first calibration position in the first direction in the robot control device.
[0055] The automatic determination of the first intermediate position in the first direction, which lies between the stored first position and the stored second position, can be carried out by determining as the first intermediate position the point which lies halfway along the path traveled by the light section sensor in the first direction when the light section sensor moves from the first position to the second position, and / or the automatic determination of the second intermediate position in the first direction, which lies between the stored first position and the stored second position, can be carried out by determining as the second intermediate position the point which lies halfway along the path traveled by the light section sensor in the first direction when the light section sensor moves from the third position to the fourth position, and / or the automatic determination of the third intermediate position in the first direction,which lies between the stored fifth position and the stored sixth position, can be done by determining as the third intermediate position the point which lies halfway along the path traveled by the light section sensor in the first direction when the light section sensor moves from the fifth position to the sixth position.
[0056] Alternatively, the automatic determination of the first intermediate position in the first direction, which lies between the stored first position and the stored second position, can be carried out by determining as the first intermediate position the point which, when the light section sensor moves from the first position to the second position, lies on a route point which deviates from half the route which the light section sensor travels in the first direction, and / or the automatic determination of the second intermediate position in the first direction, which lies between the stored third position and the stored fourth position, can be carried out by determining as the second intermediate position the point which, when the light section sensor moves from the third position to the fourth position, lies on a route point which deviates from half the route which the light section sensor travels in the first direction,and / or the automatic determination of the third intermediate position in the first direction, which lies between the stored fifth position and the stored sixth position, can be carried out by determining as the third intermediate position the point which, when the light section sensor moves from the fifth position to the sixth position, lies on a route point deviating from half the distance which the light section sensor travels in the first direction,
[0057] A supplementary fourth calibration position or an alternative further calibration position can be obtained automatically by the further step :
[0058] - Automatically moving the light section sensor in a height direction which is oriented perpendicular to the first direction and perpendicular to the second direction, in particular perpendicular to the projected line of the light section sensor, from the first height position to the second height position until the light section sensor has a higher height position with respect to the calibration object.
[0059] On the basis of at least three different stored calibration positions from the group of calibration positions comprising the first calibration position, the second calibration position, the third calibration position and the further calibration position, a mathematical transformation matrix can be automatically determined, which is designed for automatic, computational transformation between a sensor coordinate system of the light section sensor and a reference coordinate system, in particular a flange coordinate system or a hand coordinate system, of the robot kinematics.After providing the calibration object with the first line feature and the second line feature different from the first line feature on a base surface in a pose known to the robot control device and before automatically moving the light section sensor at the first height position in a first direction parallel to the projected line towards the first line feature of the calibration object until the projected line meets the first line feature of the calibration object, an intersection point of the first line feature and the second line feature can be recorded by means of a teach-in method and stored in the robot control device.
[0060] The first line feature of the calibration object intersects the second line feature of the calibration object at the intersection point. In the case of a cuboid as the calibration object, the intersection point can be formed, for example, by a corner of the cuboid. However, the intersection point can also be another outer edge, inner edge, or inner corner of a calibration body.
[0061] In particular, a cuboid having a known length, width and height stored in the robot control device can be used as the calibration object, wherein a first edge of the cuboid forms the first line feature and a second edge of the cuboid, which abuts the same corner of the cuboid as the first edge, forms the second line feature.
[0062] The object is also achieved by a robot system comprising a robot control device and a robot kinematics with a plurality of links and joints which connect the plurality of links to one another in an adjustable manner and which comprise electric drives which can be driven automatically by the robot control device, wherein the robot control device is designed and configured to automatically carry out a method according to one of the described embodiments.
[0063] A specific embodiment of the invention is explained in more detail in the following description with reference to the accompanying figures. Regardless of the specific context in which they are mentioned, specific features of this exemplary embodiment may, if appropriate, also represent general features of the invention, whether considered individually or in further combinations.
[0064] It shows :
[0065] Fig. 1 is a flow chart of the steps in the basic inventive
[0066] Procedure,
[0067] Fig. 2 is a partial view of an exemplary configuration of a robot system according to the invention with a light section sensor and a calibration object,
[0068] Fig . 3 a schematic representation of the
[0069] Pre-positioning of the
[0070] light section sensor such that the projected line lies outside the first line feature,
[0071] Fig. 4 is a schematic representation of the automatic movement of the
[0072] light section sensor until the projected line is aligned with the first
[0073] Line feature tri f ft ,
[0074] Fig. 5 is a schematic representation of the automatic movement of the light section sensor until the projected line leaves the first line feature again,
[0075] Fig. 6 to 8 a schematic representation of the third step of the method for determining the first calibration position,
[0076] Fig . 9 to 11 a schematic representation of the fourth step of the method for determining the second calibration position with a different
[0077] intermediate position, and
[0078] Fig. 12 is a side view of an exemplary configuration of a robot system according to the invention.
[0079] Fig. 1 shows the method for automatically calibrating a light section sensor 1 with respect to a member 2 of a robot kinematics 4 which can be controlled by a robot control device 3 and has a plurality of members 2 and joints 5 which adjustably connect the members 2 to one another, the light section sensor 1 being fastened to one member 2, which in the case of the present embodiment is a tool flange 2a of the robot kinematics 4.12 shows an exemplary configuration of a robot system 6, comprising the robot control device 3 and the robot kinematics 4, which in the present exemplary embodiment is designed as an articulated arm robot 4a, with the plurality of links 2 and joints 5 which adjustably connect the plurality of links 2 to one another and which comprise electric drives 7 which can be driven automatically by the robot control device 3, wherein the robot control device 3 is designed and configured to automatically carry out a method according to the invention.
[0080] The method comprises the following steps as shown in Fig . l :
[0081] In a first step S1, a calibration object 8 having a first line feature LI and a second line feature L2 different from the first line feature LI is provided on a base surface 9 in a pose known to the robot control device 3. The calibration object 8, the first line feature LI, the second line feature LI, and the base surface 9 are shown in Fig. 2 and Fig. 12.
[0082] In the case of the present embodiment, the calibration object 8 is designed as a cuboid with a known length, width and height stored in the robot control device 3, wherein a first edge of the cuboid forms the first line feature LI and a second edge of the cuboid, which abuts the same corner 11a of the cuboid as the first edge, forms the second line feature L2.
[0083] After providing the calibration object 8 with the first line feature LI and the second line feature L2, which is different from the first line feature LI, on the base surface 9 in a pose known to the robot control device 3 and before automatically moving the light section sensor 1 in the first height position in a first direction RI parallel to the projected line 10 towards the first line feature LI of the calibration object 8 until the projected line 10 meets the first line feature LI of the calibration object 8, in a second step S2 an intersection point 11 of the first line feature LI and second line feature L2 can be recorded by means of a teach-in method and stored in the robot coordinate system in the robot control device 3. In the case of the present exemplary embodiment, the intersection point 11 is accordingly formed by the corner 11a of the cuboid.
[0084] In a third step S3, the light section sensor 1 is automatically moved in the first height position along a first path parallel to the first line feature LI towards the second line feature L2 of the calibration object 8 until the projected line 10 meets the second line feature L2 of the calibration object 8, and the current position of a predetermined reference point of the robot kinematics 4 is stored in the robot coordinate system R as a first calibration position. This is also illustrated in particular in Figs. 6 to 8.
[0085] In a fourth step S4, the light section sensor 1 is automatically moved along a second path parallel to the first line feature LI, which is different from the first path, towards the second line feature L2 of the calibration object 8 until the projected line 10 meets the second line feature L2 of the calibration object 8, and the current position of the predetermined reference point of the robot kinematics 4 is stored in the robot coordinate system R as a second calibration position. This is also illustrated in particular in Figs. 9 to 11.
[0086] In a fifth step S5, the light section sensor 1 is automatically moved at a second altitude different from the first altitude along a third distance parallel to the first line feature LI, which is different from the first distance and the second distance, towards the second line feature L2 of the calibration object 8 until the projected line 10 meets the second line feature L2 of the calibration object 8, and the current position of the predetermined reference point of the robot kinematics 4 is stored in the robot coordinate system R as a third calibration position.
[0087] In a first development of the method, the automatic movement of the light section sensor 1 in the first height position along the first path parallel to the first line feature LI towards the second line feature L2 of the calibration object 8 can take place, starting from a first starting position which is obtained by the following steps.
[0088] In a first step, the light section sensor 1 is pre-positioned with respect to the calibration object 8 in the first height position with respect to the calibration object 8 by controlled adjustment of the joints 5 of the robot kinematics 4 controlled by the robot control device 3 such that a line 10 projected by the light section sensor 1 lies outside the first line feature LI of the calibration object 8,
[0089] In a second step, the light section sensor 1 is automatically moved in the first height position in a first direction RI parallel to the projected line 10 towards the first line feature LI of the calibration object 8 until the projected line 10 meets the first line feature LI of the calibration object 8, and the current position of the predetermined reference point of the robot kinematics 4 is stored in the robot coordinate system R as a first position in the first direction RI,
[0090] In a third step, the light section sensor 1 is automatically moved further in the first direction RI parallel to the projected line 10 over the first line feature 10 of the calibration object 8 while maintaining the first height position until the projected line 10 leaves the first line feature LI of the calibration object 8 again, and the current position of the predetermined reference point of the robot kinematics 4 is stored in the robot coordinate system R as a second position in the first direction RI,
[0091] And in a fourth step, a first intermediate position in the first direction RI, which lies between the stored first position and the stored second position, is automatically determined and the first intermediate position is used as the first start position.
[0092] In an alternative or supplementary development of the method, the automatic movement of the light section sensor 1 along the second path parallel to the first line feature LI toward the second line feature L2 of the calibration object 8 can be carried out starting from a second starting position which is obtained by the following steps:
[0093] Pre-positioning of the light section sensor 1 with respect to the
[0094] Calibration object 8 in a specific altitude, which in particular can be the first altitude or the second altitude, with respect to the calibration object 8 by controlled adjustment of the joints 5 of the robot kinematics 4 controlled by the robot control device 3 such that a line 10 projected by the light section sensor 1 lies outside the first line feature LI of the calibration object 8,
[0095] Automatically moving the light section sensor 1 at the specific height in a first direction RI parallel to the projected line 10 towards the first line feature LI of the calibration object 8 until the projected line 10 meets the first line feature LI of the calibration object 8, and storing the current position of the predetermined reference point of the robot kinematics 4 in the robot coordinate system R as a third position in the first direction RI,
[0096] Automatically moving the light section sensor 1 in the first direction RI parallel to the projected line 10 over the first line feature 10 of the calibration object 8 while maintaining the first height position until the projected line 10 leaves the first line feature LI of the calibration object 8 again, and storing the current position of the predetermined reference point of the robot kinematics 4 in the robot coordinate system R as a fourth position in the first direction RI,
[0097] Automatically determining a second intermediate position in the first direction RI, which lies between the stored third position and the stored fourth position, and using the second intermediate position as the second starting position. In a further, alternative or supplementary development of the method, the automatic movement of the light section sensor 1 along the third path parallel to the first line feature LI toward the second line feature L2 of the calibration object 8 can be carried out starting from a third starting position, which is obtained by the following steps:
[0098] Pre-positioning the light section sensor 1 with respect to the calibration object 8 at a further altitude, which can in particular be a third altitude different from the first altitude and the second altitude, with respect to the calibration object 8 by controlled adjustment of the joints 5 of the robot kinematics 4 controlled by the robot control device 3 such that a line 10 projected by the light section sensor 1 lies outside the first line feature LI of the calibration object 8,
[0099] Automatically moving the light section sensor 1 in the further height position in a first direction RI parallel to the projected line 10 towards the first line feature LI of the calibration object 8 until the projected line 10 meets the first line feature LI of the calibration object 8, and storing the current position of the predetermined reference point of the robot kinematics 4 in the robot coordinate system R as a fifth position in the first direction RI,
[0100] Automatically moving the light section sensor 1 in the first direction RI parallel to the projected line 10 over the first line feature 10 of the calibration object 8 while maintaining the further height position until the projected line 10 leaves the first line feature LI of the calibration object 8 again, and storing the current position of the predetermined reference point of the robot kinematics 4 in the robot coordinate system R as a sixth position in the first direction RI,
[0101] Automatically determining a third intermediate position in the first direction RI that is between the stored fifth position and the stored sixth position, and using the third intermediate position as the third start position.
[0102] In the case of the steps according to Fig. 6 to Fig. 8, the automatic determination of the intermediate position in the first direction RI, which lies between the stored first position and the stored second position, takes place in that the point is determined as the intermediate position which, when the light section sensor 1 moves from the first position to the second position, lies halfway along the path which the light section sensor 1 travels in the first direction RI (Fig. 3 to Fig. 5), and / or the automatic determination of a second intermediate position in the first direction RI, which lies between the stored third position and the stored fourth position, takes place in that the point is determined as the second intermediate position which, when the light section sensor 1 moves from the third position to the fourth position, lies halfway along the path which the light section sensor 1 travels in the first direction RI.
[0103] In the case of the steps according to Fig. 9 to Fig. 11, however, the automatic determination of the intermediate position in the first direction RI, which lies between the stored first position and the stored second position, takes place in that the point which, when the light section sensor 1 moves from the first position to the second position, lies on a route point which deviates from half the route which the light section sensor travels in the first direction (Fig. 3 to Fig.5 ), and / or the automatic determination of the second intermediate position in the first direction, which lies between the stored third position and the stored fourth position, takes place in that the point which, when the light section sensor 1 moves from the third position to the fourth position, lies on a route point which deviates from half the route which the light section sensor 1 travels in the first direction RI. In the embodiment according to Fig. 9 to Fig. 11, the intermediate position can be located on a route point of the projected line 10 which divides the projected line 10, as shown, into partial routes of, for example, three quarters and one quarter.
[0104] On the basis of at least three different stored calibration positions from the group of calibration positions comprising the first calibration position, the second calibration position, the third calibration position and the further calibration position, a mathematical transformation matrix can be automatically determined which is designed for automatic, computational transformation between a sensor coordinate system S (Fig. 12) of the light section sensor 1 and a robot coordinate system R of the robot kinematics 4. The calibration object 8 can be assigned its own calibration object coordinate system K. The pose of the calibration object coordinate system K can be known with respect to the robot coordinate system R of the robot control device R.In addition, if necessary, a further world coordinate system W can be defined, which can form a common reference point with regard to the poses of the robot coordinate system R, the calibration object coordinate system K and the sensor coordinate system S.
[0105] The third calibration position can be obtained, for example, by repeating the method as illustrated in Fig. 3 to Fig. 5, or the method as illustrated in Fig. 6 to Fig. 8 or as illustrated in Fig. 9 to Fig. 11, this time not at the first altitude, but at a second altitude different from the first altitude.
[0106] Accordingly, the light section sensor 1 can be automatically moved in a height direction which is oriented perpendicular to the first direction RI and perpendicular to the second direction R2, in particular which is oriented perpendicular to the projected line 10 of the light section sensor 1, from the first height position to a second height position until the light section sensor 1 has a higher height position with respect to the calibration object 8.
[0107] Subsequently, a pre-positioning of the light section sensor 1 with respect to the calibration object 8 in the second height position with respect to the calibration object 8 can be carried out by controlled adjustment of the joints 5 of the robot kinematics 4 controlled by the robot control device 3 in such a way that a line 10 projected by the light section sensor 1 lies outside the first line feature LI of the calibration object 8.
[0108] Then an automatic movement of the light section sensor
[0109] 1 at the second height level, in a first direction RI parallel to the projected line 10 towards the first line feature LI of the calibration object 8 until the projected line 10 meets the first line feature LI of the calibration object 8, wherein the current position of the light section sensor 1 is also stored in the robot coordinate system R as a first position in the first direction RI.
[0110] The light section sensor 1 can then be moved further automatically in the first direction RI parallel to the projected line 10 over the first line feature LI of the calibration object 8 while maintaining the second height position until the projected line 10 leaves the first line feature LI of the calibration object 8 again, wherein the current position of the light section sensor 1 is stored in the robot coordinate system R as a second position in the first direction RI.
[0111] Finally, a second intermediate position in the first direction RI can be automatically determined, which lies between the stored first position and the stored second position, wherein the second intermediate position is also stored as a third calibration position in the first direction RI.
[0112] Alternatively, the light section sensor 1 can be automatically moved in a height direction that is oriented perpendicular to the first direction RI and perpendicular to the second direction R2, which in particular runs perpendicular to the projected line 10 of the light section sensor 1, from the first height position to the second height position until the light section sensor 1 has a higher height position with respect to the calibration object 8. The light section sensor 1 can then be automatically moved to the second height position in the second direction R2, which is perpendicular to the projected line 10, towards the second line feature L2 of the calibration object 8 until the projected line 10 meets the second line feature L2 of the calibration object 8, the current position of the light section sensor 1 being stored in a robot coordinate system R as a further position in the second direction R2.The further position can thus in particular form a third or further calibration position in the second direction R2.
Claims
Patent claims 1. A method for calibrating a light section sensor (1) with respect to a member (2) of a robot kinematics (4) which can be controlled by a robot control device (3) and has a plurality of members (2) and joints (5) which adjustably connect the members (2), the light section sensor (1) being fastened to one member (2), comprising the steps of: - Providing a calibration object (8) with a first line feature (LI) and a second line feature (L2) different from the first line feature (LI) on a base surface (9) in a pose known to the robot control device (3), - Recording an intersection point (11) of the first line feature (LI) and second line feature (L2) by means of a teach-in method and storing the position of the intersection point (11) in the robot coordinate system (R) in the robot control device (3), - Automatically moving the light section sensor (1) at a first height along a first path parallel to the first line feature (LI) towards the second line feature (L2) of the calibration object (8) until the projected line (10) meets the second line feature (L2) of the calibration object (8), and storing the current position of a predetermined reference point of the robot kinematics (4) in the robot coordinate system (R) as a first Calibration position, - Automatically moving the light section sensor (1) along a second path parallel to the first line feature (LI), which is different from the first path, towards the second line feature (L2) of the calibration object (8) until the projected line (10) meets the second line feature (L2) of the calibration object (8), and storing the current position of the predetermined reference point of the robot kinematics (4) in the robot coordinate system (R) as a second calibration position, and - Automatically moving the light section sensor (1) at a second altitude different from the first altitude along a third distance parallel to the first line feature (LI), which is different from the first distance and the second distance, to the second line feature (L2) of the calibration object (8) until the projected line (10) meets the second line feature (L2) of the calibration object (8), and storing the current position of the predetermined reference point of the robot kinematics (4) in the robot coordinate system (R) as a third calibration position.
2. Method according to claim 1, characterized in that the automatic movement of the light section sensor (1) in the first height position along the first path parallel to the first line feature (LI) towards the second line feature (L2) of the calibration object (8), starting from a first starting position obtained by the following steps: - Pre-positioning the light section sensor (1) with respect to the calibration object (8) at the first height relative to the calibration object (8) by controlled adjustment of the joints (5) of the robot kinematics (4) controlled by the robot control device (3) such that a line (10) projected by the light section sensor (1) lies outside the first line feature (LI) of the calibration object (8), - Automatically moving the light section sensor (1) in the first height position in a first direction (RI) parallel to the projected line (10) towards the first line feature (LI) of the calibration object (8) until the projected line (10) meets the first line feature (LI) of the calibration object (8), and storing the current position of the predetermined reference point of the robot kinematics (4) in the robot coordinate system (R) as a first position in the first direction (RI), - Automatic movement of the light section sensor (1) in the first direction (RI) parallel to the projected line (10) over the first line feature (10) of the calibration object (8) while maintaining the first height position until the projected line (10) leaves the first line feature (LI) of the calibration object (8) again, and storing the current position of the predetermined reference point of the robot kinematics (4) in the Robot coordinate system (R) as a second position in the first direction (RI), - Automatically determining a first intermediate position in the first direction (RI) that lies between the stored first position and the stored second position, and using the first intermediate position as the first start position.
3. Method according to claim 1 or 2, characterized in that the automatic movement of the light section sensor (1) along the second path parallel to the first line feature (LI) towards the second line feature (L2) of the calibration object (8) takes place starting from a second starting position which is obtained by the following steps: - Pre-positioning the light section sensor (1) with respect to the calibration object (8) at a specific height, which can in particular be the first height or the second height, with respect to the calibration object (8) by controlled adjustment of the joints (5) of the robot kinematics (4) controlled by the robot control device (3) such that a line (10) projected by the light section sensor (1) lies outside the first line feature (LI) of the calibration object (8), - Automatic movement of the light section sensor (1) at the specific height in a first direction (RI) parallel to the projected line (10) towards the first line feature (LI) of the calibration object (8) until the projected line (10) meets the first line feature (LI) of the calibration object (8), and storing the current position of the predetermined reference point of the robot kinematics (4) in the robot coordinate system (R) as a third position in the first direction (RI), - Automatic movement of the light section sensor (1) in the first direction (RI) parallel to the projected line (10) over the first line feature (10) of the calibration object (8) while maintaining the first height position until the projected line (10) leaves the first line feature (LI) of the calibration object (8) again, and storing the current position of the predetermined reference point of the robot kinematics (4) in the Robot coordinate system (R) as a fourth position in the first direction (RI), - Automatically determining a second intermediate position in the first direction (RI) that lies between the stored third position and the stored fourth position, and using the second intermediate position as the second start position.
4. Method according to one of claims 1 to 3, characterized in that the automatic movement of the light section sensor (1) along the third path parallel to the first line feature (LI) towards the second line feature (L2) of the calibration object (8), starting from a third starting position obtained by the following steps: - Pre-positioning the light section sensor (1) with respect to the calibration object (8) at a further altitude, which can in particular be a third altitude different from the first altitude and the second altitude, with respect to the calibration object (8) by controlled adjustment of the joints (5) of the robot kinematics (4) controlled by the robot control device (3) such that a line (10) projected by the light section sensor (1) lies outside the first line feature (LI) of the calibration object (8), - Automatically moving the light section sensor (1) in the further height position in a first direction (RI) parallel to the projected line (10) towards the first line feature (LI) of the calibration object (8) until the projected line (10) meets the first line feature (LI) of the calibration object (8), and storing the current position of the predetermined reference point of the robot kinematics (4) in the robot coordinate system (R) as a fifth position in the first direction (RI), - Automatic movement of the light section sensor (1) in the first direction (RI) parallel to the projected line (10) over the first line feature (10) of the calibration object (8) while maintaining the further elevation until the projected line (10) leaves the first line feature (LI) of the calibration object (8) again, and Storing the current position of the predetermined reference point of the robot kinematics (4) in the robot coordinate system (R) as a sixth position in the first direction (RI), - Automatically determining a third intermediate position in the first direction (RI) that is between the stored fifth position and the stored sixth position, and using the third intermediate position as the third start position.
5. Method according to one of claims 2 to 4, characterized in that the first intermediate position is determined as the point which lies halfway along the path covered by the light section sensor (1) in the first direction (RI) when the light section sensor (1) moves from the first position to the second position, and / or the second intermediate position is determined as the point which lies halfway along the path covered by the light section sensor (1) in the first direction (RI) when the light section sensor (1) moves from the third position to the fourth position, and / or the third intermediate position is determined as the point which lies halfway along the path covered by the light section sensor (1) in the first direction (RI) when the light section sensor (1) moves from the fifth position to the sixth position.
6. Method according to one of claims 2 to 4, characterized in that the first intermediate position is determined as the point which, during the movement of the Light section sensor (1) from the first position to the second position lies on a route point which deviates from half the route, which the light section sensor (1) travels in the first direction (RI), and / or the second intermediate position is determined to be the point which, when the light section sensor (1) moves from the third position to the fourth position, lies on a route point which deviates from half the route, which the light section sensor (1) travels in the first direction (RI), and / or the third intermediate position is determined to be the point which, when the light section sensor (1) moves from the fifth position to the sixth position, lies on a route point which deviates from half the route, which the light section sensor (1) travels in the first direction (RI).
7. Method according to one of claims 1 to 6, characterized in that on the basis of at least three different stored calibration positions from the group of calibration positions comprising the first calibration position, the second calibration position, the third calibration position and optionally a further calibration position, a mathematical transformation matrix is automatically determined, which is designed for the automatic, computational transformation between a sensor coordinate system (S) of the light section sensor (1) and a reference coordinate system (R), in particular a flange coordinate system or a hand coordinate system, of the robot kinematics (4).
8. Method according to one of claims 1 to 7, characterized by the further step: - Automatically moving the light section sensor (1) in a height direction which is oriented perpendicular to the first direction (RI) and perpendicular to a second direction (R2), in particular perpendicular to the projected line (10) of the light section sensor (1), from the first height position to the second height position until the light section sensor (1) has a higher height position with respect to the calibration object (8).
9. Method according to one of claims 1 to 8, characterized in that a cuboid with a known length, width and height stored in the robot control device (3) is used as the calibration object (8), wherein a first edge of the cuboid forms the first line feature (LI) and a second edge of the cuboid, which abuts the same corner (11a) of the cuboid as the first edge, forms the second line feature (L2).
10. Robot system, comprising a robot control device (3) and a robot kinematics (4) with a plurality of links (2) and joints (5) which adjustably connect the plurality of links (2) to one another and which comprise electric drives (7) which can be driven automatically by the robot control device (3), wherein the robot control device (3) is designed and configured to automatically carry out a method according to one of claims 1 to 9.