Device and method for positioning an auxiliary joining element in a workpiece hole

Abstract

Device for positioning an auxiliary joining element (1), in particular a screw, in a workpiece hole (3), comprising a receiving unit (9), in particular a screw unit, controlled by a robot control unit (11), in which the auxiliary joining element (1) is held, wherein in a positioning operation the robot-controlled receiving unit (9) inserts the auxiliary joining element (1) into the workpiece hole (3) in a feed movement perpendicular to the workpiece surface, wherein the receiving unit (9) is designed with a sensor system (13) with an evaluation module (15) with which a positional offset transverse to the joining direction (F) between the auxiliary joining element (1) and the workpiece hole (3) can be determined, and wherein the robot control unit (11) performs a fine adjustment on the basis of the positional offset determined by the evaluation module (15),in which the robot-controlled holding unit (9) can be adjusted via an alignment path (y) while reducing the positional offset into a positionally correct orientation that enables interference-free threading of the auxiliary joining element (1) into the workpiece hole (3), characterized in that the sensor system (13) has at least three laser sensors (17, 19, 21, 23) which are uniformly circumferentially distributed on the robot-controlled holding unit (9) with respect to a sensor system central axis (M) aligned in line with the joining direction (F), that the line-shaped laser beams (24) of the laser sensors (17, 19, 21, 23) converge at the same angles of incidence (α) at ​​a laser beam vertex (S) lying on the sensor system central axis (M), that the positioning process has a first process step in which the robot-controlled holding unit (9) moves in a feed movement into The joining direction (F) approaches the workpiece hole (3) up to a pre-position (VP),and that the pre-position (VP) is reached as soon as at least one of the laser sensors (17, 19, 21, 23) detects a hole edge (25) of the workpiece hole (3) and the laser beam vertex (S) has moved into the workpiece hole (3) by a feed path (I1) detected by the robot control unit (11), and that the evaluation module (15) calculates a radius (r1) of a virtual circle (27) using a trigonometric function from the feed path (I1) and the angle of incidence (α), which runs in a hole edge plane (L) facing the robot-supported holding unit (9) and whose center point lies on the sensor system central axis (M).

Description

[0001] The invention relates to a device for positioning an auxiliary joining element, in particular a screw, in a workpiece hole according to the preamble of claim 1 and a corresponding method according to the preamble of claim 9.

[0002] In mass production, the positioning of screws in a workpiece hole can be fully automated using a screw unit, which is mounted, for example, on the end link of a robot arm. The screw to be inserted into the workpiece hole is held in the screw unit during the setting process.

[0003] The robot arm is controlled in a setting or positioning process based on coordinates stored in a robot controller, ensuring that the screw can be inserted into the workpiece hole without interference and subsequently tightened, for example, with a nut. However, due to manufacturing / workpiece tolerances, there is a risk that the workpiece hole and the screw will not be perfectly aligned during the setting process. In this case, the screw may collide with the edge of the workpiece hole during the setting process. To avoid such a collision, the prior art involves excessively large clearance between the screw and the workpiece hole to accommodate these manufacturing / workpiece tolerances. However, excessive clearance can negatively impact the strength of the screw connection.

[0004] DE 10 2022 114 425 A1 discloses a generic device for inserting a connecting element into a component. US 2006 / 0167587 A1 discloses a robot-assisted process control for the manufacture of a motor vehicle. CN 112140045 A discloses a screw tool with alignment elements. The elements are arranged at 90° intervals around the circumference of the screw tool. US 2006 / 0167587 A1 discloses a robot arm with a system for aligning screw elements with respect to a thread. The alignment is performed using laser sensors.

[0005] The object of the invention is to provide a device and a method in which, compared to the prior art, the positioning of an auxiliary joining element, in particular a screw, in a workpiece hole can be carried out without interference contours despite tight manufacturing / workpiece tolerances.

[0006] The problem is solved by the features of claim 1 or 9. Preferred embodiments of the invention are disclosed in the dependent claims.

[0007] The invention relates to a device for positioning an auxiliary joining element, in particular a screw, in a workpiece hole. The device comprises a receiving unit, in particular a screw unit, controlled by a robot control unit, in which the auxiliary joining element is held. In a setting / positioning process, the robot-assisted receiving unit with the auxiliary joining element is inserted into the workpiece hole in a feed motion, in particular perpendicular to the workpiece surface, by control from the robot control unit. According to the invention, the robot-controlled receiving unit is equipped with a sensor system with an evaluation module. With the aid of the evaluation module, a positional offset transverse to the joining direction between the auxiliary joining element and the workpiece hole can be determined. The robot control unit can perform a fine adjustment based on the positional offset determined by the evaluation module.During fine adjustment, the robot-controlled receiving unit is moved via an alignment path, reducing the positional offset, into a positionally correct alignment, thus ensuring that the auxiliary joining element can be threaded into the workpiece hole without interference contours.

[0008] The sensor system comprises at least three, and in particular four, laser sensors, which may optionally include a rangefinder function. The laser sensors are uniformly distributed around the circumference of the robot-controlled receiving unit with respect to a sensor system central axis aligned with the insertion direction. Preferably, the sensor system comprises four laser sensors, two of which are located opposite each other on a vertical axis with respect to the sensor system central axis, while the other two are located opposite each other on a horizontal axis. The pair of sensors arranged on the vertical axis and the pair arranged on the horizontal axis preferably remain in their horizontal and vertical orientations, respectively, during the positioning process.Furthermore, the laser sensors are arranged such that their linear laser beams converge at a common laser beam apex located on the sensor system's central axis, all at the same angle of incidence. The respective angle of incidence is defined between the sensor system's central axis and the linear laser beam of the respective laser sensor.

[0009] The positioning process can be divided into several process steps, which are preferably designed with a view to reduced computational effort and reduced sensor effort: In the first process step, the robot-controlled gripper unit approaches the workpiece hole, which is typically circular, in a feed motion in the joining direction until it reaches a pre-position. This pre-position is reached when at least one of the laser sensors detects the edge of the workpiece hole and the apex of the laser beam has moved into the workpiece hole by a feed path determined by the robot control unit. If this occurs, the evaluation module can calculate the radius of a virtual circle using a trigonometric function based on the feed path and the angle of incidence. The virtual circle lies in a plane of the hole's edge facing the robot-controlled gripper unit, with its center point on the sensor system's central axis.

[0010] The first process step can preferably be carried out using cost-effective and structurally simple laser sensors. During the positioning process, the laser sensors integrated into the sensor system only need to detect whether the laser beam's point of impact is outside or inside the workpiece hole. Upon detecting such a change in the point of impact, the laser sensor detects the edge of the workpiece hole and triggers a corresponding edge signal, which is then sent to the evaluation module.

[0011] In the second process step, the evaluation module determines the spatial orientation of the virtual circle with respect to the workpiece hole. This is done using a query program stored within the evaluation module. The query program checks which and how many of the laser sensors triggered a hole edge signal in the first process step. Based on the query result, the evaluation module can calculate the alignment path as follows: When only one hole edge signal is triggered, the evaluation module recognizes that the virtual circle lies within the workpiece hole and tangentially touches the hole edge at a point of contact. In this case, the alignment path is calculated as the difference between the workpiece hole radius and the radius of the virtual circle. The alignment path extends along a movement axis towards the center of the workpiece hole. In the case of a four-sensor system with a vertical sensor pair and a horizontal sensor pair, the system determines which of the four laser sensors triggered the hole edge signal. Depending on the position of the triggered sensor, the alignment path extends along either the vertical or the horizontal axis towards the center of the workpiece hole.

[0012] When two circumferentially adjacent laser sensors are triggered, the evaluation module recognizes that the center of the virtual circle is located inside the workpiece hole and / or that the virtual circle intersects the edge of the workpiece hole at two points.

[0013] The evaluation module can use a trigonometric function to calculate the distance I from the coordinates of the intersection points recorded by the robot control unit and from the radius of the virtual circle. 45° The distance between the center of the virtual circle and the edge of the workpiece hole is determined. The evaluation module can then calculate the alignment path from the difference between the hole radius and the distance I. 45° Determinable. In addition, the alignment path extends along a movement axis towards the center of the workpiece hole, which, viewed in the circumferential direction, is located centrally between the two triggered laser sensors.

[0014] An embodiment of the invention is described below with reference to the accompanying figures.

[0015] They show: Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7 to Fig. 8 different views, each illustrating the device and the method for positioning a screw in a workpiece hole.

[0016] In the Fig. Figure 1 is a device for positioning a screw 1 in a workpiece hole 3 of a workpiece 5, indicated to the extent necessary for understanding the invention. The device comprises an articulated robot arm 7, on the distal end 8 of which a screw unit 9 is mounted. The screw 1 is held on the screw unit 9 during a setting or positioning process. The screw unit 9 and the articulated robot arm 7 are controlled by a robot control unit 11, based on coordinates stored in the robot control unit 11. Using the coordinates stored in the robot control unit, a coarse positioning is performed, in which the screw unit 9 is moved to a close proximity of the workpiece hole 3.

[0017] After the rough positioning, the robot control unit 11 performs a fine adjustment, in which a positional offset between screw 1 and workpiece hole 3 that exists transversely to the joining direction F is detected, and in which the robot control unit 11 aligns the screwdriver unit 9 via an alignment path y ( Fig. 6 or Fig. 6) by reducing the positional offset into a positionally correct alignment which allows the screw 1 to be threaded into the workpiece hole 3 without interference contour.

[0018] For fine-tuning, the screwdriver unit 9 is equipped with a sensor system 13 and an evaluation module 15. The sensor system 13 comprises a total of four laser sensors 17, 19, 21, 23. These are uniformly spaced at 90° intervals around the circumference of the screwdriver unit 9 with respect to a sensor system central axis M. The laser sensors 17, 19, 21, 23 are arranged on the screwdriver unit 9 such that their linear laser beams 24 converge at a single laser vertex S, located on the sensor system central axis M, at equal angles of incidence α.

[0019] The four laser sensors 17, 19, 21, 23 are arranged in pairs horizontally and vertically relative to each other: Laser sensors 17 and 19 are positioned opposite each other on a vertical axis V with respect to the sensor system's central axis M, while laser sensors 21 and 23 are positioned opposite each other on a horizontal axis H with respect to the sensor system's central axis M. The horizontal and vertical orientation of these two sensor pairs remains unchanged throughout the entire setting / positioning process.

[0020] The following will be based on the Fig. 3, Fig. 4, Fig. 5, Fig. 6 to Fig. Section 7 describes the positioning / setting process for positioning the screw 1 in the workpiece hole 3 without interference contours. A key aspect of the invention is that the positioning process is carried out with the lowest possible computational effort in the evaluation module 15 and with the lowest possible sensor effort.

[0021] Accordingly, the positioning process is divided into a total of three process steps. In a first process step, the screw unit 9 approaches a pre-position VP with a feed movement in the joining direction F ( Fig. 3 or Fig. 4) the circular workpiece hole 3. The preliminary position VP is reached as soon as at least one of the laser sensors 17, 19, 21, 23 detects a hole edge 25 of the workpiece hole 3 and the laser beam apex S has moved into the workpiece hole 3 by a feed path I1 detected by the robot control unit 11.

[0022] The evaluation module 15 calculates a radius r1 of a virtual circle 27 from the feed path I1 and the angle of incidence α using the following trigonometric function ( Fig. 6 or Fig. 7): tan(β)=l1r1 β=90°−α r1=l1tan(β)

[0023] The virtual circle line 27 runs in a hole edge plane L ( Fig. 4), which faces the robot-assisted screwdriving unit 9. The center point of the virtual circle 27 lies on the sensor system's central axis M.

[0024] The laser sensors 17, 19, 21, 23 are cost-effective and have a simple design. During the positioning process, they simply detect whether the laser beam's point of impact is outside or inside the workpiece hole 3. By detecting such a change in the point of impact, the respective laser sensor 17, 19, 21, 23 can detect the hole edge 25 of the workpiece hole 3 and generate a corresponding hole edge signal S. L trigger. If necessary, the laser sensor 17, 19, 21, 23 can also perform a distance measurement. According to the Fig. 3 and Fig. 4. The upper laser sensor 17 detects a change in the point of impact, for example from outside the workpiece hole 3 to inside the workpiece hole 3. The upper laser sensor 17 therefore generates a hole edge signal S. L ( Fig. 3), which is routed to the evaluation module 15. The other laser sensors 19, 21, 23, however, do not detect such a change in the point of impact and therefore do not generate a hole edge signal S. L .

[0025] In a second process step, the evaluation module 15 determines the spatial orientation of the virtual circle 27 with reference to the workpiece hole 3. In a third process step, the evaluation module 15 calculates the alignment path y, over which the robot-controlled screw unit 9 must be adjusted until it is correctly aligned.

[0026] To carry out the second process step, a query program is required in evaluation module 15 ( Fig. 5) stored. The query program asks which and how many of the laser sensors 17, 19, 21, 23 received a hole edge signal S in the first process step. LThe evaluation module 15 can calculate the alignment path y based on the query result using simple equations or trigonometric functions.

[0027] When only the upper laser sensor 17 is triggered, the evaluation module 15 recognizes that the virtual circle 27 is located inside the workpiece hole 3 and tangentially touches the hole edge 25 at a contact point B, as specified in the query program of the Fig. 5 is shown in query 5. In this case, the alignment path y results according to the Fig. 6. Calculate simply from the difference in the workpiece hole radius r L minus the radius r1 of the virtual circle 27, as can be seen from the following equation: γ=r1−dL2

[0028] If only one laser sensor is triggered, the alignment path y extends along a movement axis towards the center of the workpiece hole, with the movement axis in the Fig. 6 corresponds to the vertical axis V. The alignment path y is in the Fig. 6 is shown as a vector.

[0029] Triggering of two circumferentially adjacent laser sensors 17, 19, 21, 23 is performed in the query program of the Fig. 5 is determined during queries 1 to 4. If the triggering of two adjacent laser sensors is detected, the evaluation module 15 recognizes that the virtual circle 27 intersects the workpiece hole edge 25 at two intersection points S1, S2, as shown in the query diagram of the Fig. 5 is indicated in queries 1 to 4. Furthermore, evaluation module 15 recognizes in which angular range or quadrant the intersection between virtual circle line 27 and workpiece hole edge 25 is located. In the Fig. The virtual circle line 27 is located, for example, in the upper right quadrant.

[0030] The evaluation module 15 can calculate a distance I from the intersection point coordinates recorded by the robot control unit 11 and from the radius r1 using the following trigonometric function. 45° Determine the distance between the center of the virtual circle 27 and the edge of the workpiece hole 25: l45°=rHole−124rHole2−(r12+r32)+r122

[0031] The alignment path y can be easily calculated from the difference between the hole radius r and the distance between the hole radius and the distance between the hole radius and the hole radius. L minus the distance I 45° -determinable, as can be seen from the following equation: γ=rL−l45°

[0032] The one in Fig.7 The alignment path y, also shown as a vector, extends along a movement axis towards the workpiece hole center point, which is located approximately midway between the two intersection points S1 and S2.

[0033] After the third process step, the process sequence from the first to third process steps can be repeated until the screw 1 is inserted into the workpiece hole 3 without interference contours. REFERENCE MARK LIST 1 screw 3 workpiece holes 5 workpieces 7 articulated arm robots 8 Robot end link 9 Recording unit / screwdriver unit 11 Robot control unit 13 Sensor system 15 Evaluation module 17, 19, 21, 23 laser sensors 24 linear laser beam 25 hole edge 27 virtual circles B Point of contact F Leading direction S Laser beam vertex S1, S2 Intersection points S L Hole edge signal H Horizontal axis L Hole edge plane M Sensor system - center axis V Vertical axis VP Preliminary Position y alignment path r1 Radius of the virtual circle 27 r L Workpiece hole radius d1 Diameter of the virtual circle 27 d L workpiece hole diameter I1 Feed path I 45° Distance α Angle of incidence

Claims

[1] Device for positioning an auxiliary joining element (1), in particular a screw, in a workpiece hole (3), comprising a receiving unit (9), in particular a screw unit, controlled by a robot control unit (11), in which the auxiliary joining element (1) is held, wherein in a positioning operation the robot-controlled receiving unit (9) inserts the auxiliary joining element (1) into the workpiece hole (3) in a feed movement perpendicular to the workpiece surface, wherein the receiving unit (9) is designed with a sensor system (13) with an evaluation module (15) with which a positional offset transverse to the joining direction (F) between the auxiliary joining element (1) and the workpiece hole (3) can be determined, and wherein the robot control unit (11) performs a fine adjustment on the basis of the positional offset determined by the evaluation module (15),in which the robot-controlled receiving unit (9) can be adjusted via an alignment path (y) while reducing the positional offset into a positionally correct orientation, which enables interference-free threading of the auxiliary joining element (1) into the workpiece hole (3), characterized by, that the sensor system (13) has at least three laser sensors (17, 19, 21, 23) which are uniformly circumferentially distributed around the circumference of the robot-controlled holding unit (9) with respect to a sensor system central axis (M) aligned in line with the joining direction (F), that the line-shaped laser beams (24) of the laser sensors (17, 19, 21, 23) converge at the same angles of incidence (α) at ​​a laser beam vertex (S) located on the sensor system central axis (M), that the positioning process has a first process step in which the robot-controlled holding unit (9) approaches the workpiece hole (3) in a feed movement in the joining direction (F) up to a pre-position (VP), and that the pre-position (VP) is reached as soon as at least one of the laser sensors (17, 19, 21,23) a hole edge (25) of the workpiece hole (3) is detected and the laser beam vertex (S) has moved into the workpiece hole (3) by a feed path (I1) detected by the robot control unit (11), and that the evaluation module (15) calculates a radius (r1) of a virtual circle (27) using a trigonometric function from the feed path (I1) and the angle of incidence (α), which runs in a hole edge plane (L) facing the robot-supported holding unit (9) and whose center point lies on the sensor system central axis (M). [2] Device according to claim 1, characterized by , that the angle of incidence (α) is spanned between the sensor system central axis (M) and the laser beam (24) of the respective laser sensor (17, 19, 21, 23). [3] Device according to claim 1 or 2, characterized by, that the respective laser sensor (17, 19, 21, 23) detects during the positioning process whether the laser beam impact point is outside or inside the workpiece hole (3), and that the laser sensor (17, 19, 21, 23) detects the hole edge (25) of the workpiece hole (3) upon detecting such a change in impact point and triggers a corresponding hole edge signal (SL). [4] Device according to any one of the preceding claims, characterized by , that the positioning process has a second process step in which the evaluation module (15) determines the spatial orientation of the virtual circle line (27), and that in particular in a third process step the evaluation module (15) calculates the alignment path (y) over which the robot-controlled recording unit (9) can be adjusted until it is correctly aligned. [5] Device according to claim 4, characterized by, that after the third process step the process sequence from the first to third process steps can be carried out again until the auxiliary joining element (1) is inserted into the workpiece hole (3) without interference contours. [6] Device according to claim 4 or 5, characterized by , that in the second process step the spatial orientation of the virtual circle line (27) with reference to the workpiece hole (3) can be determined by means of a query program stored in the evaluation module (15), that in particular the query program queries which and how many of the laser sensors (17, 19, 21, 23) received a hole edge signal (S) in the first process step L ) have triggered, and that the evaluation module (15) calculates the alignment path (y) based on the query result using trigonometric functions. [7] Device according to claim 6, characterized by, that when only one laser sensor (17, 19, 21, 23) is triggered, the evaluation module (15) recognizes that the virtual circle (27) lies within the workpiece hole (3) and tangentially touches the edge (25) of the workpiece hole (3) at a point of contact (B), so that the alignment path (y) is calculated from the difference in the workpiece hole radius (r) L ) minus the radius (r1) of the virtual circle (27), and that the alignment path (y) extends along a movement axis towards the workpiece hole center point, which preferably corresponds to the horizontal axis or the vertical axis. [8] Device according to claim 6 or 7, characterized by, that when two circumferentially adjacent laser sensors (17, 19, 21, 23) are triggered, the evaluation module (15) recognizes that the center of the virtual circle (27) lies within the workpiece hole (3) and / or that the virtual circle (27) intersects the edge (25) of the workpiece hole (3) at two intersection points (S1, S2), and that the evaluation module (15) uses a trigonometric function to calculate a distance (I) from the intersection point coordinates detected by the robot control unit (11) and from the radius (r1) of the virtual circle (27). 45° ) between the center of the virtual circle (27) and the edge of the workpiece hole (25) is determined, and in particular the alignment path (y) is determined from the difference between the hole radius (r) L ) minus the distance (I 45°) can be determined, and in particular the alignment path (y) extends along a movement axis towards the workpiece hole center point, which is located midway between the two intersection points (S1, S2). [9] Method for positioning an auxiliary joining element, in particular a screw (1), in a workpiece hole (3), using a device according to one of the preceding claims, wherein the device has a receiving unit (9), in particular a screw unit, controlled by a robot control unit (11), in which the auxiliary joining element (1) is held, wherein in a positioning operation the robot-controlled receiving unit (9) inserts the auxiliary joining element (1) into the workpiece hole (3) in a feed movement perpendicular to the workpiece surface, wherein the receiving unit (9) is designed with a sensor system (13) with an evaluation module (15) with which a positional offset transverse to the joining direction (F) between the auxiliary joining element (1) and the workpiece hole (3) is determined, and wherein the robot control unit (11) performs a fine adjustment on the basis of the positional offset determined by the evaluation module (15),in which the robot-controlled receiving unit (9) is adjusted via an alignment path (y) while reducing the positional offset into a positionally correct orientation, which enables interference-free threading of the auxiliary joining element (1) into the workpiece hole (3), characterized by, that the sensor system (13) has at least three laser sensors (17, 19, 21, 23) which are uniformly circumferentially distributed around the circumference of the robot-controlled holding unit (9) with respect to a sensor system central axis (M) aligned in line with the joining direction (F), that the line-shaped laser beams (24) of the laser sensors (17, 19, 21, 23) converge at the same angles of incidence (α) at ​​a laser beam vertex (S) located on the sensor system central axis (M), that the positioning process has a first process step in which the robot-controlled holding unit (9) approaches the workpiece hole (3) in a feed movement in the joining direction (F) up to a pre-position (VP), and that the pre-position (VP) is reached as soon as at least one of the laser sensors (17, 19, 21,23) a hole edge (25) of the workpiece hole (3) is detected and the laser beam vertex (S) has moved into the workpiece hole (3) by a feed path (I1) detected by the robot control unit (11), and that the evaluation module (15) calculates a radius (r1) of a virtual circle (27) using a trigonometric function from the feed path (I1) and the angle of incidence (α), which runs in a hole edge plane (L) facing the robot-supported holding unit (9) and whose center point lies on the sensor system central axis (M).

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