Compensation of positioning errors in robot-assisted surface machining.

Abstract

To suppress defects in surface processing when the direction of the processing force is not perpendicular to the surface of the workpiece. [Solution] An apparatus is disclosed that includes a bracket having a base plate configured to be attached to a manipulator, and an assembly having a machine tool and suspended from the bracket, the bracket having a tilt mechanism that couples the assembly to the bracket such that the assembly can be tilted relative to the base plate about two axes of rotation that intersect and extend below the base plate and through the assembly.

Description

[Technical Field]

[0001] The present specification relates to the field of machine tools, in particular to orbital grinding machines for automated robot-assisted grinding. [Background technology]

[0002] In robot-assisted surface treatment, machine tools such as grinding or polishing machines (e.g., electric grinders that use a rotating abrasive disk as the grinding tool) are guided by a manipulator, e.g., an industrial robot. The so-called TCP (Tool Center Point) of the machine tool and manipulator can be coupled in various ways. The manipulator usually has virtually free control over the machine's position and orientation, allowing the machine tool to move, for example, along a trajectory parallel to the workpiece surface. The industrial robot usually performs position control and can move the TCP precisely along the desired trajectory.

[0003] To achieve good results in robot-assisted grinding, it is often necessary to control the processing force (grinding force), but it is often difficult to achieve sufficient precision with conventional industrial robots. Because industrial robots have large, heavy arms, their inertial mass is high, and their controllers (closed-loop control) cannot quickly respond to fluctuations in the processing force. To solve this problem, a linear actuator smaller than that of an industrial robot can be placed between the TCP of the manipulator and the machine tool, which can couple the TCP of the manipulator to the machine tool. In surface processing, the linear actuator only controls the processing force (contact force between the tool and workpiece), and the manipulator is position-controlled to move the machine tool along the desired trajectory together with the linear actuator. Summary of the Invention [Problem to be solved by the invention]

[0004] There are situations where the trajectory along which the manipulator moves the machine tool is not parallel to the surface, and as a result, the direction of movement of the linear actuator (i.e., the direction of the machining force) is not perpendicular to the surface of the workpiece. This angular deviation (deviation from perpendicularity to the surface) not only deteriorates the machining quality but also leads to surface machining defects.

[0005] The inventors have developed a method for robotic surface processing. Improved equipment The challenge is to develop it. [Means for solving the problem]

[0006] The above problem is solved by claim 1 By the system described in It is resolved. Different embodiments and further developments are the subject of the dependent claims.

[0007] A robot-assisted surface processing apparatus is described below. According to one embodiment, the apparatus includes a bracket having a base plate configured to be attached to a manipulator, and an assembly having a machine tool and suspended from the bracket. The bracket includes a tilt mechanism that couples the assembly to the bracket such that the assembly can be tilted relative to the base plate about two axes of rotation that intersect and extend below the base plate through the assembly.

[0008] Another embodiment of the present invention provides an apparatus including a bracket having a base plate configured to be attached to a manipulator, and an assembly including a machine tool suspended from the bracket. The bracket includes a tilt mechanism coupling the assembly to the bracket such that the assembly is tiltable about two rotational axes relative to the base plate. The tilt mechanism includes stops that limit tilt about the two rotational axes to a defined maximum angle. The tilt mechanism is lockable to prevent tilting.

[0009] Another embodiment of a robot-assisted surface machining system is described. The system includes a manipulator, an assembly having a machine tool coupled to a TCP (Tool Center Point) of the manipulator, and a controller for controlling movement of the TCP of the manipulator. The controller is configured to detect an angular deviation between a longitudinal axis of the machine tool and a normal to the surface of the workpiece while a tool attached to the machine tool is in contact with the surface of the workpiece. The controller is also configured to adjust the orientation of the TCP to reduce the angular deviation based on the detected angular deviation.

[0010] In yet another embodiment, the system includes a manipulator and an apparatus coupled to the TCP of the manipulator. The apparatus includes a bracket having a base plate configured to be attached to the manipulator, and an assembly having a machine tool suspended from the bracket. The bracket includes a tilt mechanism that couples the assembly to the bracket such that the assembly can tilt relative to the base plate about two rotational axes, the two rotational axes intersecting each other and extending below the base plate through the assembly. The apparatus further includes sensors configured to detect tilt angles about the two rotational axes. [Effects of the Invention]

[0011] To suppress defects in surface processing when the direction of the processing force is not perpendicular to the surface of the workpiece. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram illustrating an example of a robot-assisted grinding device. [Figure 2] FIG. 1 is a diagram showing an example of correcting the angular error of the orientation of the tool center point (TCP) of a robot-assisted grinding device relative to the workpiece surface by adjusting the TCP. [Figure 3]FIG. 10 is a diagram showing an example in which the angle error in the attitude of the tool center point (TCP) is corrected by a universal joint, eliminating the need for TCP adjustment. [Figure 4] As shown in Figure 3, the coupling of the grinding device to the TCP of the manipulator is shown in more detail, with the coupling being via a bracket with a lockable universal joint. [Figure 5] FIG. 5 is a diagram showing the example of FIG. 4 in which the universal joint is unlocked and the grinding device is tilted. [Figure 6] FIG. 10 is an isometric view of another example of a robotic assisted grinding device having a universal joint for correcting angular errors. [Figure 7] 7 is a cross-sectional view showing a locking device (unlocked state) for fixing the universal joint in the embodiment according to FIG. 6. FIG. [Figure 8] 8 shows the locking device of FIG. 7 in more detail. [Figure 9] FIG. 8 is a diagram showing the example shown in FIG. 7 in which the locking device locks the universal joint to prevent tilting of the grinding machine relative to the TCP. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will now be described in more detail with reference to the embodiments shown in the drawings. The illustrations are not necessarily to scale, and the invention is not limited to the illustrated aspects. Rather, emphasis is placed on illustrating the principles underlying the invention.

[0014] Before describing various embodiments of the present invention in detail, an example of a robot-assisted grinding machine will first be described, as the concepts described herein are applicable to other types of surface finishing (e.g., polishing, milling) and are not limited to grinding.

[0015] According to FIG. 1, the apparatus comprises a manipulator 1, e.g., an industrial robot, and a grinding machine 10 (e.g., an orbital grinding machine) equipped with a rotating grinding tool. The grinding machine 10 is coupled to the so-called tool center point (TCP) of the manipulator 1 via a compensation device 20, which in this embodiment is implemented, e.g., as a linear actuator. Strictly speaking, the TCP is not a point but a vector, which can be described, for example, by three spatial coordinates and three angles. In robotics, generalized coordinates in the configuration space (usually the six joint angles of a robot) are sometimes used to describe the position of the TCP. The position and orientation of the TCP are sometimes called "pose." More generally, the compensation device 20 is configured to compensate for changes in the position of the TCP relative to the workpiece surface. Furthermore, the compensation device 20 is intended to generate a machining force between the machine tool (in this embodiment, the grinding machine 10) and the workpiece surface. In the simplest case, the compensation device 20 can be a spring. The linear actuator described above allows for precise control of the machining force. For feedback control, the compensation device 20 can include a force measurement system capable of measuring the machining force. In the case of a pneumatic linear actuator, the force measurement system can have a pressure sensor that measures the air pressure inside the actuator, from which the machining force can be determined (taking into account the actuator's characteristics). However, it is also possible to combine a spring with a load cell (force measurement container). In this case, force control must be performed by the manipulator.

[0016] The function of the compensator can also be provided by the manipulator itself if it is capable of force control. For this reason, the robot usually requires force-torque sensors and a corresponding complex control system.

[0017] Alternatively, in the case of an industrial robot with six degrees of freedom, the manipulator may consist of four segments 2a, 2b, 2c, and 2d, connected by joints 3a, 3b, and 3c, respectively. The first segment is typically (but not necessarily) rigidly connected to the base 41. Joint 3c connects segments 2c and 2d. Joint 3c may be biaxial, allowing segment 2c to rotate about a horizontal axis of rotation (elevation) and a vertical axis of rotation (azimuth). Joint 3b connects segments 2b and 2c, allowing segment 2b to pivot relative to the position of segment 2c. Joint 3a connects segments 2a and 2b. Joint 3a may be biaxial, allowing pivoting in two directions (as does joint 3c). The TCP has a fixed relative position with respect to the segment 2a, which typically includes a revolute joint (not shown) that allows pivoting about the longitudinal axis A of the segment 2a (shown in dashed lines in FIG. 1 and corresponding to the axis of rotation of the grinding tool). Each axis of the joint is assigned an actuator that can cause rotational movement about the respective joint axis. The joint actuators are controlled by the robot controller 4 according to the robot program. Various industrial robots / manipulators and associated controls are known and will not be further described here.

[0018] The manipulator 1 is typically position-controlled; that is, the robot controller determines the pose (position and orientation) of the TCP and can move it along a predefined trajectory. In Figure 1, the longitudinal axis of the segment 2a on which the TCP is located is labeled A. When the actuator 20 is at its end stop, the pose of the TCP also determines the pose of the grinding machine 10 (and the grinding disk 11). As mentioned earlier, the actuator 20 sets the contact force (machining force) between the tool and the workpiece 40 to a desired value during the grinding process. Direct force control by the manipulator 1 is typically too inaccurate for grinding applications. This is because the high mass inertia of the segments 2a-c of the manipulator 1 makes rapid correction of force peaks (e.g., when placing the grinding tool on the workpiece 40) virtually impossible with conventional manipulators. For this reason, the robot controller 4 controls the pose (position and orientation) of the TCP of the manipulator 1, while force control is solely performed by the actuator 20.

[0019] As already mentioned, during the grinding process, the contact force F between the grinding tool and the workpiece 40 K is the contact force F between the grinding tool and the workpiece 40 (in the direction of the longitudinal axis A). K can be set by the (linear) actuator 20 and the force control (which can be realized in the control unit 4, for example) so that the contact force F K is the actuator force F that the linear actuator 20 presses against the surface of the workpiece. A When there is no contact between the workpiece 40 and the tool, the actuator 20 moves to the end stopper (not shown as it is integrated with the actuator 20) due to the lack of contact force with the workpiece 40, and presses it with a predetermined force. Therefore, in this situation (non-contact), the displacement of the actuator 20 is at its maximum (a = a MAX ) and the actuator is located at the (outer) end.

[0020] The position control of the manipulator 1 (which can also be realized by the control unit 4) can be performed completely independently of the force control of the actuator 20. The actuator 20 is not used for positioning the grinding machine 10, but rather for controlling the desired contact force F during the grinding process. K The actuator is only used to set and maintain the maximum displacement a of the tool and to detect contact between the tool and the workpiece. This contact is easily recognized, for example, by the actuator moving away from its end position (the actuator displacement a is equal to the maximum end displacement a). MAX smaller than

[0021] The actuator may be a pneumatic actuator, such as a double-acting pneumatic cylinder. However, other pneumatic actuators, such as bellows cylinders or air muscles, can also be used. Alternatively, an electric direct drive (gearless) is also conceivable. Note that the direction of action of the actuator 20 does not necessarily coincide with the longitudinal axis A of the manipulator segment 2a. In the case of a pneumatic actuator, force control can be realized in a manner known per se by a control valve, a control device (implemented in the control unit 4), and a compressed air accumulator. Since the tilt with respect to the vertical direction is important to take into account gravity (i.e., the weight force of the grinding machine 10), the actuator 20 includes a tilt sensor. The measured tilt is taken into account during force control. However, the specific implementation of force control is known per se, and therefore a detailed description will be omitted.

[0022] The grinding machine 10 typically comprises an electric motor which drives a grinding disc 11. In an orbital grinding machine, the grinding disc 11 is mounted on a support plate (grinding pan 12), to which the motor shaft of the electric motor is connected. The electric motor can be an asynchronous or synchronous motor. A synchronous motor has the advantage that its speed does not change with the load (only the slip angle), whereas an asynchronous machine will slow down as the load increases. The load on the motor is essentially determined by the contact force F K and is proportional to the friction between the grinding disc 11 and the surface of the workpiece 40 being machined.

[0023] Instead of electrically driven grinding machines, grinding machines with pneumatic motors (compressed air motors) can also be used. Compressed air motors usually have a low power-to-weight ratio, so grinding machines operated with compressed air can be relatively compact. Rotation control is easily possible with a pressure control valve (e.g., electrically controlled by the control unit 4) (also additionally or alternatively with a throttle), while synchronous and asynchronous motors require a frequency converter (e.g., electrically controlled by the control unit 4) for rotation control. The concepts described here can be implemented in various types of grinding, polishing, and other surface processing machines.

[0024] As mentioned above, the manipulator 1 moves the TCP (and thus the grinding machine 10) along a predetermined trajectory that follows the surface (contour) of the workpiece. In practice, situations may arise where the TCP does not follow the surface exactly, resulting in an angular deviation. This angular deviation may be the result of, on the one hand, the position tolerance of the workpiece 40 or an inaccurate (intentional or unintentional) programming of the trajectory. Figure 2 shows an example of a situation where the trajectory x(t) is not parallel to the workpiece surface but is tilted by an angle φ. Therefore, it can be seen that the TCP is also tilted by an angle φ with respect to the surface normal, i.e., the movement direction of the actuator 20 is not perpendicular to the workpiece surface but is tilted by an angle of 90°-φ. According to Figure 1, the actuator 20 has a displacement a(t) at the TCP position x(t) at time t. At time t, the TCP (and therefore the entire grinding machine 10 including the actuator 20) moves to position x(t), which means the displacement Δx = x(t) - x(t). The tilt by angle φ has reduced the deflection of actuator 20 by Δa (Δa=a(t1)-a(t0)). Since the values Δx and Δa are known to the robot controller, the (local) tilt angle between the workpiece surface and the TCP trajectory can be calculated as follows: φ = tan -1 (Δa / Δx) (1) Alternatively, the angle can be measured, for example, by measuring the distance between the TCP on opposite sides of the grinding machine and the workpiece surface. The difference in the measured distances gives the tilt angle. However, as mentioned above, measurement is not absolutely necessary, as the angle can be calculated from quantities known to the robot controller (e.g., Δa and Δx). In the example at the beginning, the manipulator itself performs the function of the linear actuator (compensator), so the robot itself must perform the movements that the linear actuator would perform, and therefore the robot controller "knows" both quantities Δa and Δx.

[0025] As mentioned above, the tilt angle φ between the workpiece surface and the TCP trajectory is equal to the angular deviation of the motion direction of the actuator 20 (and thus the direction of the machining force) from the surface normal. According to the calculation of the angular deviation φ (e.g., according to Equation 1), the robot controller can correct the TCP's orientation so that the machining force acts perpendicular to the surface. The right side of Figure 2 shows this situation, where the TCP moves further at position x(t2) to correct the angular deviation φ. Figure 2 is a simplified example of one-dimensional robot motion. This angular correction can also be performed in several spatial directions.

[0026] Figure 2 illustrates "active" determination and correction of angular deviations by a robot controller. The example in Figure 3 shows a "passive" approach, where the grinding machine 10 (including the actuator 20) is "suspended" from the TCP and can be swiveled to orient the TCP. For example, a bracket 30 with a kind of universal joint (Cardan joint) can be used as a support, allowing tilting in two directions (in the feed direction and transversely to the feed direction, i.e., along the trajectory and transversely to it). The actuator 20 presses the grinding machine 10, and thus the grinding plate 11, against the surface of the workpiece 40 with a defined (actuator) force, causing the grinding machine 10 to apply a contact force F KThe robot is positioned "automatically" (without actively positioning) parallel to the surface normal Ns so that it acts perpendicular to the surface. This allows the robot controller to correct the angular error without knowing how to correct it, and the TCP direction N T The change in the normal distance between the surface and the TCP is proportional to the contact force F K Since the force controller always controls the actuator 20 so that the force corresponds to the target force, the force is "automatically" compensated by the actuator 20 and the force control.

[0027] The connection of the TCP of the robot to the assembly comprising the grinding machine 10 and the actuator 20 is shown in more detail in FIGS. 4 and 5. As mentioned above, this connection is made by a bracket 30 with a kind of universal joint, so that the grinding machine 10 together with the actuator 20 can be tilted with respect to the direction NT of the TCP about two axes Rx and Ry, so that in the zero position (no tilt), the two axes Rx and Ry are perpendicular to each other and to the direction NT of the TCP. According to the illustrated example, the bracket 30 has an L-shaped bracket 31, with a base plate 31a and a protruding portion 31b forming the two legs of the bracket 31. The base plate 31a is rigidly connected (fixed) to the TCP of the robot 1 (for example, by a screw connection), and the protruding portion 31b is arranged substantially parallel to the direction NT of the TCP (in the non-tilted state). In this case, the upper side of the base plate is placed in front of the arm segment 2a of the robot 1, but in the example shown in Figure 1, the upper mounting plate 22 (flange) of the actuator 20 is directly connected to the manipulator. In the example shown, the angle between the overhanging portion 31b and the base plate 31a is formed to be a right angle.

[0028] The first rotation axis Rx of the universal joint described above passes through the protruding portion 31b, and a mounting bracket 32 is further attached to the protruding portion 31b so as to be rotatable (around the rotation axis Rx). A first leg (not visible in Figures 4 and 5) of the mounting bracket 32 is rotatably attached to the protruding portion 31b, and a third mounting bracket 33 (or mounting bar) is rotatably attached (around the rotation axis Ry) to a second leg of the mounting bracket 32 that projects at a right angle from the protruding portion 31b. Thus, the third mounting bracket 33 can be tilted around both the rotation axis Rx and the rotation axis Ry, forming a universal joint. The actuator 20 is configured such that (in a non-tilted state) the direction of movement of the actuator 20 (and therefore the direction of the rotation axis of the grinding disc 11) is aligned with the TCP direction N. T The upper mounting plate 22 and the mounting bracket 33 are connected so as to be coaxial with each other. The grinding machine 10 is connected to the lower mounting plate 21 (flange) of the actuator 22 (e.g., by a screw connection). The rotation axes Rx, Ry intersect each other below the base plate 31a. In the illustrated example, the intersection of the rotation axes Rx and Ry may be located above the grinding machine 10, i.e., inside the actuator 20. In other examples, the intersection may be located further below, i.e., inside the grinding machine 10.

[0029] As shown in Figure 3, when the grinding machine 10 equipped with the grinding disc 11 is pressed against the surface of the workpiece, the grinding machine 10 tilts about the rotation axes Rx and Ry, allowing it to "automatically" adapt to the surface of the workpiece. However, there are situations in which this tilting is undesirable. According to the example shown in Figures 4 and 5, a locking mechanism is provided between the upper part (upper mounting plate 22) of the actuator 20 and the lower part of the base plate 31a, which locks the mount 30 so that tilting about the rotation axes Rx and Ry is no longer possible, and the grinding machine 10 is adapted to be fixedly (non-movably / non-tiltably) (rigidly) coupled to the TCP of the robot 1.

[0030] 4 and 5, the locking mechanism includes an actuator 53, which is mounted, for example, on top of the actuator 20 and includes a latch configured to engage a corresponding recess 51 in the bottom surface of the base plate 31a when the actuator 53 is in an extended state, thus securing the actuator 20 to the base plate 31a. The actuator 53 may be, for example, a pneumatic or solenoid actuator suitable for reciprocating the latch 52 between an end retracted position (unlocked state) and an end extended position (locked state).

[0031] The recess 51 may have a shape that is symmetrical with respect to the longitudinal axis of the actuator 20 (and the axis of rotation of the grinding machine 10 in the non-tilted state). For example, the recess may have a conical, cylindrical, pyramidal, or spherical segment (concave) shape. Also, the latch 52 has a symmetrical (convex) shape (e.g., cylindrical, spherical segment, pyramidal, etc.). The specific shapes are not important, and the symmetrical shapes of the recess 51 and latch 52 ensure that when the actuator 53 presses the latch 52 into the recess 51, the actuator 20 and the grinding machine 10 (i.e., their axis of rotation) are aligned with the TCP (normal vector N T ) so that the locking mechanism is self-aligning.

[0032] The left side of Fig. 4 shows the device in an unlocked state (i.e., the actuator 20 and grinding machine 10 can tilt), while the right side of Fig. 4 shows the device in a locked state (i.e., the actuator 20 and grinding machine 10 are rigidly coupled (fixed) to the TCP). Locking is particularly desirable in situations where the grinding disc 11 is not intended to remain stationary tangentially to the workpiece surface, for example when grinding narrow edges. Furthermore, it is desirable for the robot 1 to be locked when it moves the grinding machine 10 to a replacement station to remove the grinding disc 11 and install a new one. Suitable replacement stations for automatically replacing the grinding disc 11 are known per se.

[0033] The latch 52 and the recess 51 are inclined at a maximum angle φ such that the edge of the recess 51 forms a stopper for the latch 52. MAX The left part of Figure 5 is substantially the same as the left part of Figure 4. The right part of Figure 5 shows the grinding machine 10 and actuator 20 in an inclined position, with the latch 52 resting against the end of the recess 51 (forming the stopper mentioned above). In this position, the angle of inclination is limited to a maximum angle of inclination φ MAX is equivalent to

[0034] 6 is an isometric view of another example of a robot-assisted grinding machine with a universal joint for correcting angular errors. As shown, the grinding machine 10 has a support disc 12 onto which a grinding disc can be mounted. The grinding machine 10 is connected to the lower mounting plate 21 of the actuator 20 (e.g., by a screw connection), and a first leg of the mounting bracket 33 is connected to the upper mounting plate 22 of the operating unit 20 (e.g., also by a screw connection). The second leg of the mounting bracket 33 is connected to the mounting bracket 32 (hidden by the actuator 20 in FIG. 6; see FIG. 5) so as to be rotatable about a rotation axis Ry, and the mounting bracket 32 is further connected to the protruding portion 31b of the mounting bracket 31 so as to be rotatable about a rotation axis Rx. The base plate 31a of the mounting bracket 31 is substantially parallel to the mounting plate 22 of the actuator 20 in the non-tilted state. The two rotation axes Rx and Ry are orthogonal and can form a universal joint as described above with reference to FIGS. 4 and 5. As shown in FIG. 6, one or more hoses and / or cables can be attached to the mounting bracket 31 (e.g., to the protruding portion 31b) and connected to the grinding machine 10. The hose 15 shown in Figure 6 can be used, for example, for dust suction. The cable is used, for example, to supply power to the electric motor of the grinding machine. Also shown in Figure 6 is a screw 310 by which the mounting bracket 31 can be attached to the TCP of the manipulator.

[0035] Figure 7 shows the device of Figure 6 in a side view with partial cross section, in which the locking mechanism already described above with reference to Figures 4 and 5 can be seen. Furthermore, in this view the mounting bracket 32 can be seen. Figure 8 is an enlarged view of the upper part of Figure 7. In the situation shown, the actuator 53 is retracted and therefore the latch 52 is in its lowermost position. The grinding machine 10 and the actuator 20 are rotated about the axis Ry at a maximum angle φ MAX 5a, so that the (symmetrical, convex) protrusion 521 of the latch 52 abuts the edge of the (concave) recess in the part 50. For manufacturing reasons, in this example the recess 51 is not located directly on the base plate 31, but on the part 50 that is mated with the latch 52 and connected to the base plate 31a. However, in other embodiments the mating part 50 and the base plate 31a may be an integral part. However, in some applications it may be useful to make the part 50 with the recess 51 interchangeable, in order to use a device with different parts 50 each having a differently shaped recess 51. By changing the part 50, it is possible to change, for example, the maximum tilt angle φ MAX Furthermore, if the shape of the part 50 can be adapted to the dimensions of the actuator 20 and grinding machine 10, the device can be made to work with different actuators 20 and grinding machines 10.

[0036] 9 shows the same embodiment as in FIG. 7, but with actuator 53 extended and latch 52 engaging recess 51 in part 50 such that tilting movement of grinding machine 10 and actuator 20 is no longer possible. In this state, grinding machine 10 and actuator 20 are rigidly coupled to the TCP of robot 1.

[0037] 7-9, the intersection of rotation axis Rx and rotation axis Ry is located within actuator 20 or below base plate 31a within grinding machine 10. In operation (i.e., when the grinding machine is in contact with the workpiece surface), the longitudinal axis of grinding machine 10 (and therefore the direction of movement of actuator 20) is aligned perpendicular to the workpiece surface, and the surface normal Ns and the TCP orientation N T The inclination angle is between φ<φ MAX The maximum tilt angle is φ MAX As long as the grinding disc 10 is moved to the center of the workpiece, it is no longer ensured that the longitudinal axis of the grinding machine 10 is essentially perpendicular to the workpiece surface (and therefore that the grinding disc is tangent to the surface).

[0038] In some applications, the tilt angle with respect to the rotation axes Rx and Ry is measured and / or the maximum angle φ MAX 50 and latch 52 contacts part 50. Based on this information, the robot controller can take various actions, such as raising the grinding machine until contact between the grinding tool and the workpiece surface is released. For this purpose, for example, an angle sensor can be coupled to the revolute joint having rotation axes Rx and Ry, thereby providing the controller 4 with information about the actual tilt angle. The angle sensor is not shown in the drawings. Methods for measuring the angles that rotatable parts make with each other in a revolute joint are known to those skilled in the art, and therefore the sensor technology will not be described in further detail here.

[0039] Furthermore, it should be noted that the "active" approach according to Fig. 2 can be combined with the "passive" approach according to Figs. 3 to 5. That is, even in the case of the device according to Fig. 3, the robot controller can be configured to constantly readjust the orientation of the TCP so that the tilt angle φ remains below a predetermined threshold, i.e., the tilt angle φ is greater than the maximum tilt angle φ. MAX(the bulge 521 hits the edge of the recess 51, see FIG. 8 ), the robot controller can adjust the TCP to reduce the tilt angle φ. If the tilt angle φ is known (for example, based on measurements), it can be controlled to be approximately zero (taking into account unavoidable tolerances). To avoid constant readjustment of the TCP, the controller 4 adjusts the TCP so that the measured angle φ is equal to or smaller than the threshold φ R The tilt angle φ can be configured to decrease by adjusting the TCP only when the threshold φ R is the maximum angle φ MAX can be made smaller than

[0040] The configuration examples of the embodiments of the present invention are summarized as follows.

[0041] (Configuration example 1) a bracket (30) having a base plate (31a) configured to be attached to the manipulator (1); an assembly having a machine tool (10) suspended from said bracket (30); An apparatus having: the bracket (30) has a tilting mechanism, and the tilting mechanism connects the assembly (10, 20) to the bracket (30) so that the assembly (10, 20) can be tilted relative to the base plate (31 a) around two rotation axes (Rx, Ry); The two rotation axes (Rx, Ry) intersect each other and extend through the assembly below the base plate (31a). Device.

[0042] (Configuration example 2) The apparatus according to configuration example 1, wherein the two rotation axes (Rx, Ry) intersect substantially perpendicularly to each other.

[0043] (Configuration example 3) The apparatus according to configuration example 1 or 2, wherein the tilting mechanism has a gimbal that can tilt the assembly relative to the base plate (31a) about the two rotation axes (Rx, Ry).

[0044] (Configuration Example 4) the bracket (30) has a first mounting bracket (31), a second mounting bracket (32), and a third mounting bracket (33), which are mechanically coupled to one another such that the second mounting bracket (32) is tiltable relative to the first mounting bracket (31) about a first rotation axis (Rx) of the two rotation axes, and the third mounting bracket (33) is tiltable relative to the second mounting bracket (32) about a second rotation axis (Ry) of the two rotation axes; The assembly is rigidly attached to the third mounting bracket (33), and the base plate (31a) is part of the first mounting bracket (31). The device according to configuration example 1 or 2.

[0045] (Configuration Example 5) The apparatus of any one of configurations 1 to 4, further comprising a locking mechanism configured to secure the assembly to the base plate (31a) and prevent tilting.

[0046] (Configuration Example 6) The device according to configuration example 5, wherein the locking mechanism comprises an actuator (53), a latch (52), and a part (50) having a recess (51), which are configured such that the actuator (53) can push the latch (52) into the recess (51).

[0047] (Configuration Example 7) 7. The device according to configuration example 6, wherein the part (50) having the recess (51) is integral with the base plate (31a) or rigidly connected to the base plate (31a).

[0048] (Configuration Example 8) The device of configuration example 6 or 7, wherein in the unlocked state, the side surfaces of the recess form stops that limit tilting about the two rotation axes (Rx, Ry) to a defined maximum angle.

[0049] (Configuration Example 9) The device according to any one of configuration examples 5 to 7, wherein the locking mechanism is configured to allow tilting of the assembly relative to each of the two rotation axes (Rx, Ry) in an unlocked state, as long as the tilt angle is smaller than the maximum angle corresponding to each of the two rotation axes (Rx, Ry).

[0050] (Configuration Example 10) The device according to configuration example 9, wherein the locking mechanism has a stopper that prevents the tilt angle from exceeding the maximum angle.

[0051] (Configuration Example 11) 11. The apparatus of any one of configurations 1 to 10, further comprising a sensor configured to detect an angle of inclination relative to the two axes of rotation.

[0052] (Configuration Example 12) 12. The apparatus of any one of configurations 1 to 11, wherein the assembly further comprises a force measurement system configured to measure a force exerted by the machine tool on a surface of a workpiece.

[0053] (Configuration Example 13) The apparatus of any one of configuration examples 1 to 12, wherein the assembly further comprises a compensation device (20) coupled to the machine tool and configured to compensate for changes in the position of the bracket (30) relative to the surface of the workpiece.

[0054] (Configuration Example 14) 14. The device according to example 13, wherein the compensation device (20) is an actuator, in particular a linear actuator, or a spring.

[0055] (Configuration Example 15) A manipulator (1) and an assembly coupled to the TCP of the manipulator (1) and having a machine tool (10); a control unit (4) for controlling the movement of the TCP of the manipulator (1); A system having: The control unit (4) Detecting an angular deviation (φ) between a longitudinal axis of the machine tool (10) and a normal to the surface of the workpiece while a tool (11) attached to the machine tool (10) is in contact with the surface of the workpiece; and adjusting the orientation of the TCP based on the detected angular deviation (φ) so that the angular deviation (φ) becomes smaller. system.

[0056] (Configuration Example 16) the assembly includes a linear actuator (20) coupled to the machine tool (10); The control unit is configured to calculate the angular deviation (φ) based on the deflection (Δx) of the TCP and the corresponding change (Δa) in deflection of the linear actuator (20). The system described in configuration example 15.

[0057] (Configuration Example 17) A manipulator (1) and The device according to configuration example 11 coupled to the TCP of the manipulator (1); a control unit (4) for controlling the movement of the TCP of the manipulator (1); A system having: The control unit (4) is configured to adjust the orientation of the TCP based on the angle measured by the sensor. system.

[0058] (Configuration Example 18) a bracket (30) having a base plate (31a) configured to be attached to the manipulator (1); an assembly including a machine tool (10) suspended from said bracket (30); An apparatus having: the bracket (30) has a tilting mechanism, and the tilting mechanism couples the assembly (10, 20) to the bracket (30) so that the assembly (10, 20) can be tilted about two rotation axes (Rx, Ry) relative to the base plate (31 a); The tilt mechanism is configured to tilt the two rotation axes (Rx, Ry) up to a defined maximum angle (φ MAX ) and a stopper that limits the The tilt mechanism is lockable to prevent tilting Device. [Explanation of symbols]

[0059] 1...Manipulator 4...Control unit 10…Machine tools 11...Tools 10, 20…Assembly 30…Bracket 31, 32, 33...Mounting bracket 31a… base plate 50...Parts 51...recess 52...Latch 53...Actuator Rx, Ry...Rotation axis φ…Angle deviation φ MAX …Maximum angle

Claims

1. A manipulator (1), an assembly coupled to the TCP of the manipulator (1) and having a machine tool (10); a control unit (4) for controlling the movement of the TCP of the manipulator (1); A system having: The control unit (4) Detecting an angular deviation (φ) between a longitudinal axis of the machine tool (10) and a normal to the surface of the workpiece while a tool (11) attached to the machine tool (10) is in contact with the surface of the workpiece; and adjusting the orientation of the TCP based on the detected angular deviation (φ) so that the angular deviation (φ) becomes smaller; the assembly includes a linear actuator (20) coupled to the machine tool (10); The system, wherein the controller is configured to calculate the angular deviation (φ) based on a deflection (Δx) of the TCP and a corresponding change (Δa) in deflection of the linear actuator (20).

2. 10. The system of claim 1, wherein the assembly further comprises a force measurement system configured to measure a force exerted by the machine tool on a surface of a workpiece.

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