Quick clamping system for connecting machine tools to robots

Abstract

To provide a lamp system that is relatively simple and has sufficient accuracy for many applications. [Solution] A clamping system for mounting a tool or machine tool to a manipulator, the system comprising: a chuck having a base plate configured to be mounted to a flange positionable under force control by the manipulator; a tool holder configured to be mounted to the machine tool, the tool holder having a mounting plate adjacent to the base plate in a locked state; a pin configured to align the mounting plate with the base plate in the mounted state and prevent movement of the mounting plate relative to the base plate in a plane parallel to the base plate; at least one resilient member; and a clamp coupling configured to lock the tool holder to the base plate of the chuck, wherein in the locked state the resilient member deforms to apply a pretensioning force between the base plate and the mounting plate.

Description

[Technical Field]

[0001] The present invention relates to a quick clamping system for connecting a machine tool to a robot. [Background technology]

[0002] In robot-assisted surface processing, machine tools (e.g. grinding, drilling, milling, polishing, etc.) are guided by manipulators, e.g. industrial robots. The machine tool and the so-called TCP (Tool Center Point) of the manipulator can be coupled in various ways. The manipulator usually has virtually free control over the position and orientation of the TCP and can move the machine tool, 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 or other surface treatment processes, control of the grinding force is often necessary, but conventional industrial robots often struggle to achieve sufficient precision. Because industrial robots have large, heavy arms, their inertial mass is high, making their controllers (closed-loop control) unable to respond quickly to fluctuations in the grinding force. To solve this problem, a linear actuator, smaller and lighter than the industrial robot, can be placed between the TCP of the manipulator and the machine tool, coupling the TCP of the manipulator and the machine tool. In surface processing, the linear actuator controls only the grinding force (the contact force between the tool and the workpiece), while the manipulator is position-controlled to move the machine tool along the desired trajectory together with the linear actuator. Force control allows the linear actuator to compensate (within a certain range) for inaccuracies in the position and shape of the workpiece being machined and inaccuracies in the manipulator's trajectory. However, there are robots that can adjust the grinding force using force / torque control, even without the aforementioned linear actuator. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] US 2018 / 126512 A1 Summary of the Invention [Problem to be solved by the invention]

[0005] Various clamping systems are known that are suitable for connecting and disconnecting various machine tools to a robot. Simple systems require an operator to manually change the tool on the robot. The precision requirements for robots are usually relatively high, and the clamping systems currently on the market are relatively complex and expensive.

[0006] The inventors set themselves the task of creating a quick clamping system for connection to machine tools that is relatively simple and accurate enough for many applications. [Means for solving the problem]

[0007] The above problem is solved by a device according to claim 1. Different embodiments and further developments are the subject of the dependent claims.

[0008] A quick clamping system for mounting a tool or machine tool to a manipulator is described. In one embodiment, the quick clamping system includes a chuck having a base plate configured to be mounted to a flange positionable under force control by a manipulator, a tool holder configured to be mounted to a machine tool, the tool holder having a mounting plate adjacent to the base plate in a locked state, a plurality of pins configured to align the mounting plate with the base plate in a mounted state and prevent movement of the mounting plate relative to the base plate in a plane parallel to the base plate, at least one resilient member, and a clamping coupling configured to lock the tool holder to the base plate of the chuck, wherein in a locked state, the resilient member deforms to apply a pretensioning force between the base plate and the mounting plate. [Effects of the Invention]

[0009] It is possible to provide a quick clamping system for connection to machine tools that is relatively simple and has sufficient accuracy for many applications. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is an exemplary schematic diagram of a robot-assisted grinding apparatus with a grinding machine coupled to an industrial robot by a force-controlled linear actuator, which allows for partial mechanical decoupling of the industrial robot and the grinding machine. [Figure 2] FIG. 1 is an exploded perspective view showing an example of a quick clamp system for connecting a machine tool and a robot. [Figure 3] FIG. 3 is a side view of the example shown in FIG. 2. [Figure 4] FIG. 1 is a perspective view showing the quick clamping system in a clamped state. [Figure 5] FIG. 5 illustrates the system of FIG. 4 including a machine tool. DETAILED DESCRIPTION OF THE INVENTION

[0011] Various embodiments will now be described in more detail using illustrative examples, which are not necessarily to scale and are not intended to limit the invention to the illustrated embodiments, but rather to illustrate the principles underlying the invention.

[0012] Before describing various embodiments of the present invention in detail, a general example of a robot-assisted grinding machine will first be described. The concepts described here can be applied to other types of surface finishing (e.g., polishing, milling, drilling) and are not limited to grinding. The quick clamping system described below allows any part to be quickly connected to the robot.

[0013] According to FIG. 1, the robot-assisted grinding device comprises a manipulator 80, for example an industrial robot, and a grinding machine 10 (for example an orbital grinding machine) equipped with a rotating grinding tool 51, the grinding machine 10 being connected to the manipulator via a linear actuator 20, which in this embodiment is implemented as a linear actuator, for example. 80 The TCP is connected to the so-called Tool Center Point (TCP) of the robot. Strictly speaking, the TCP is not a point but a vector, and can be described, for example, by three spatial coordinates (position) and three angles (directions). In robotics, generalized coordinates in 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 the "pose." The position (including orientation) of the TCP defines the motion of the grinding tool as a function of time, and this motion is called the trajectory. The TCP is often defined as the center of the robot's end-effector flange, but this is not necessarily the case. The TCP can be any point (theoretically even outside the robot) at which the robot can adjust its position and orientation. The TCP can also define the origin of the tool coordinate system.

[0014] Alternatively, in the case of an industrial robot with six degrees of freedom, the manipulator 80 may be composed of four segments 82, 83, 84, and 85 connected by joints G11, G12, and G13, respectively. The first segment 82 is typically (but not necessarily) rigidly connected to the base 81. Joint G11 connects segments 82 and 83. Joint G11 may be biaxial, allowing segment 83 to rotate about a horizontal axis of rotation (elevation) and a vertical axis of rotation (azimuth). Joint G12 connects segments 83 and 84, allowing segment 84 to pivot relative to the position of segment 83. Joint G13 connects segments 84 and 85. Joint G13 may be biaxial, allowing pivoting in two directions (similar to joint G11). The TCP has a fixed relative position with respect to the segment 85, which typically includes a revolute joint (not shown) that allows pivoting movement of an end effector flange 86 disposed on the segment 85 about a longitudinal axis A (shown in dashed lines in FIG. 1 and corresponding to the axis of rotation of the grinding tool in the illustrated example). Each axis of the joint is assigned an actuator (e.g., an electric motor) that can cause rotational movement about the respective joint axis. The joint actuators are controlled by the robot controller 70 according to a robot program. Various industrial robots / manipulators and associated controls are known and will not be further described here.

[0015] The manipulator 80 is typically position-controlled; that is, the robot controller determines the TCP's pose (position and orientation) and moves it along a predefined trajectory. In Figure 1, the longitudinal axis of the segment 85 on which the TCP is located is labeled A. When the actuator 90 is at its end stop, the TCP's pose also determines the pose of the grinding machine 50 (and the grinding disk 51). As mentioned earlier, the actuator 90 sets the contact force (machining force) between the tool and the workpiece 60 to a desired value during the grinding process. Direct force control by the manipulator 80 is typically too imprecise for grinding applications. This is because the high mass inertia of the manipulator's segments 83-85 makes rapid correction of force peaks (e.g., when positioning the grinding tool on the workpiece 60) virtually impossible with conventional manipulators. For this reason, the robot control unit 70 is configured to control the posture (position and direction) of the TCP of the manipulator 80, and the actuator 90 is configured to control the force.

[0016] As already mentioned, during the grinding process, the contact force F between the grinding tool (the grinding machine 50 with the grinding plate 51) and the workpiece 60 K is the contact force F between the grinding plate 51 and the workpiece 60 (in the direction of the longitudinal axis A). K can be set by the linear actuator 90 and force control (which can be realized in the control unit 70, for example) so that the contact force F K is the actuator force F with which the linear actuator 90 presses the surface of the workpiece. A When there is no contact between the workpiece 60 and the tool 51, the actuator 90 acts as an end stop (actuator 90) due to the lack of contact force on the workpiece 60. 90The actuator 90 then moves to the end stop (not shown, as it is integrated into the workpiece) and presses it with a predetermined force. At this time, the force control is constantly active. Therefore, in this situation (non-contact), the displacement of the actuator 90 is at its maximum and the actuator 90 is located at its end. The force with which the actuator 90 presses the end stop can be limited to be very small or (theoretically) zero, in order to enable the smoothest contact with the workpiece surface.

[0017] The position control of the manipulator 80 (which can also be achieved by the control unit 70) can be performed completely independently of the force control of the actuator 90. The actuator 90 is not used to position the grinding machine 50, but rather to control the desired contact force F during the grinding process. K and to detect contact between the tool 51 and the workpiece 60. This contact is easily recognized, for example, by the actuator moving away from its end position (the actuator displacement a is equal to the end maximum displacement a MAX smaller than

[0018] The actuator 90 may be a pneumatic actuator, for example a double-acting pneumatic cylinder. However, it is also possible to use other pneumatic actuators, for example bellows cylinders or air muscles. Alternatively, an electric direct drive (gearless) is also conceivable. It should be noted that the direction of action of the actuator 90 and the axis of rotation of the grinding machine 50 do not necessarily coincide with the longitudinal axis A of the segment 85 of the manipulator 80. In the case of a pneumatic actuator, the control of the force can be realized in a manner known per se by means of a control valve, a control device (for example implemented in the control unit 70), and a compressed air accumulator or compressor. Since the tilt with respect to the vertical direction is important to take into account gravity (i.e. the weight of the grinding machine 50), the actuator 90The actuator 90 may include a tilt sensor, or this information may be determined based on the joint angles of the manipulator 80. The determined tilt is taken into account during force control. However, since specific implementations of force control are known per se, a detailed description will be omitted. The actuator 90 not only provides a certain degree of mechanical decoupling between the manipulator 80 and the workpiece 60, but also makes it possible to compensate for inaccuracies in the positioning of the TCP.

[0019] FIG. 2 shows an exemplary embodiment of a quick clamping system that allows machine tools, such as grinding, polishing, and milling machines, to be attached and detached from a robot with relative ease. FIG. 2 shows a portion of the linear actuator 90 described above, which is coupled at one end to the end effector flange 85 (on the robot's distal arm segment 85, see FIG. 1 ) and has a flange 91 at its other end for attaching the machine tool. The actuator 90 is therefore often referred to as an "active flange" because it can actively set the force between the end effector flange and the machine tool. FIG. 3 is a side view corresponding to FIG. 2. FIG. 4 is a perspective view of the assembled quick clamping system in a locked state.

[0020] According to FIG. 2 , the quick clamping system essentially consists of a chuck 10 (clamping chuck) that can be mechanically coupled to a flange 91 (e.g., by a screw), an elastic element configured as a rubber washer 20 in this example, and a tool holder 30 that can be mechanically rigidly coupled to a machine tool. The washer 20 can be made of rubber or plastic, particularly an elastomer. The flange 91 has multiple threaded holes 210. In the illustrated example, the flange 91 has six threaded holes 210, three of which are threaded with cylindrical pins 11. The cylindrical pins have a cylindrical upper portion and a threaded lower portion 110 that can be threaded into the threaded holes 210. Cylindrical pins are also often called dowel pins. Instead of using screws, the cylindrical pins can also be glued or pressed (without threads) into the corresponding holes. The threaded cylindrical pin 11 acts as a guide for the tool holder 30, preventing tilting of the tool holder 30, particularly about the z-axis (axis perpendicular to the plane of the base plate 15, see FIG. 2). More generally, the pin 11 serves to prevent relative movement of the mounting plate 31 of the tool holder 30 with respect to the base plate 15 of the chuck 10 in a plane parallel to the plane of the plate (the xy-plane), while allowing some movement perpendicular to that plane.

[0021] The chuck 10 basically comprises a base plate 15 and two or more clamping brackets 13 attached to the sides of the base plate 15. The base plate 15 has a plurality of holes 12 (usually drilled holes). In the example shown in FIG. 3, the base plate 15 has six holes, three of which receive cylindrical pins 11 threaded into a flange 91 to fix the position of the chuck. The other three holes 12 are for receiving screws 14 that can be threaded into corresponding threaded holes 21 in the flange 91 to secure the base plate 15 to the flange 91. In the example shown in FIG. 2, the six screw holes 210 are offset from each other by 60°, resulting in the three cylindrical pins 11 and three screws 14 being offset from each other by 120° (relative to the z-axis).

[0022] The base plate 15 has two lateral projections 16 that project towards the flange 91, forming an angle of substantially 90° with the base plate 15 (see FIG. 3). The clamping bracket 13 is attached to these projections (e.g., by screws). Note that the cylindrical pin 11 could alternatively be attached (e.g., screwed) to the base plate 15 (rather than to the flange 91). However, in terms of compliance with the required tolerances, the example shown in FIG. 2, in which the cylindrical pin 11 is screwed into the flange 91, may be better (depending on the specific application). To function properly, the cylindrical pin 11 must project from the base plate 15 at a right angle to it.

[0023] The tool holder 30 is rigidly connected to the machine tool (not shown in Figures 2 to 4). The specific configuration of the tool holder 30 depends on the machine tool. In particular, the part of the tool holder 30 that serves to fix the tool holder 30 to the machine tool varies depending on the machine tool and is adapted to the machine tool. The tool holder 30 functions as an interface, so to speak, by which the machine tool can be clamped to the chuck 10. The tool holder 30 comprises a mounting plate 31 having holes 33 and hooks 32. Mounting Plate 31 The tool holder 30 is fitted to the base plate 15 of the chuck 10. When assembled, the mounting plate of the tool holder 30 is inserted so that the cylindrical pin 11 passes through the hole 33. 31 The cylindrical pin 11 is fitted to the tool holder 30. The cylindrical pin 11 therefore defines the position of the tool holder 30 (and therefore the position of the machine tool) in the x and y directions (i.e., the xy plane that intersects the z axis). In the clamped state, the mounting plate of the tool holder 30 31 The clamp bracket 13 (bracket) is adjacent to the base plate 15 of the chuck 10, and is clamped by engaging with the corresponding hook 32 (the hook is sometimes called a keeper). Therefore, the clamp 13 and the hook form a clamp connection (draw latch). The base plate 15 and the mounting plate 31A slight elastic displacement of the tool holder 30 relative to the chuck 10 in the z-direction is possible by an elastic element (e.g., rubber washer 20) arranged between the clamping brackets 13 and the corresponding hooks 32. The elastic element (e.g., rubber washer 20) can be deformed (the rubber washer 20 is crushed) when the clamping connection is locked, and can provide a pretensioning of the clamping connection when locked. That is, in the locked state, the clamping brackets 13 pull the respective hooks 32 (and vice versa). At the same time, the elastic body / rubber washer 20 is deformed and in a pretensioned state. The clamping brackets 13 and the corresponding hooks 32 are known per se and commercially available, and will not be described further here.

[0024] The clamp connection (draw latch) formed by combining the clamp bracket 13 and hook 31 with an elastic element is also called a dead-center lock (over-center latch) because when the clamp bracket 13 is hooked onto the corresponding hook 32 and locked, it rotates around the joint 131 to and beyond the dead center of the rotational movement. Therefore, the clamp bracket 13 cannot return beyond the dead center unless an external force is applied, so the clamp connection / dead-center lock is safe from accidental release. This external force must be applied manually by the operator when locking and unlocking.

[0025] It should be noted that the rubber washer 20 is merely one example of an elastic body. Generally, any elastic element disposed (somewhere in the quick clamping system) that elastically deforms when the clamp connection (between the clamp bracket 13 and the hook 32) is locked and applies a pretension force in the z direction to the clamp connection between the chuck 10 and the tool holder 30 in the locked state is suitable. This elastic deformation allows the tool holder 30 to move slightly in the z direction relative to the chuck 10, but relative movement in the x and y directions is prevented by the cylindrical pin 11, which serves as a linear guide. Instead of the rubber washer 20, one or more elastic elements can be incorporated into the clamp bracket 13 or the hook 32. In this case, the rubber washer 20 can be omitted. For example, the hook 32 and / or a portion of the clamp bracket 13 itself may be formed (at least partially) from an elastic or flexible material. In this case, the term flexible clamp connection (flexible draw latch) or clamp band connection may also be used. Alternatively, the clamping bracket 13 may be supported by a spring at the overhang 16 of the base plate 15 so as to be elastically displaceable in the z direction. Additionally or alternatively, the hook 32 may be supported by a spring or other elastic element so as to be elastically displaceable on the mounting plate 31. Additionally or alternatively, the bearing bush of the joint 131 of the clamping bracket 13 may also be made of an elastic material so as to undergo the aforementioned elastic deformation when locking the clamp connection.

[0026] Figure 5 shows a linear actuator 90 mounted to a robot (not shown in Figure 5, see Figure 1) having a locked quick clamping system according to the embodiment of Figures 2-4, with a rod grinding machine 50 mounted to a tool holder 30. As previously mentioned, the tool holder 30 serves as an interface for clamping the machine tool to the chuck 10 of the quick clamping system.

[0027] The quick clamping system presented here can be used in particular with robots that can control the contact force between the tool and the workpiece surface. This force control can be performed by the actuator 90, as described above, or by the robot itself, if the robot is suitable for this purpose. In this case, it is also possible to omit the actuator 90 and mount the chuck 10 directly on the end effector flange 86 (see FIG. 1) rather than on the flange 91 of the actuator 90. In either case (with or without the actuator 90), the contact force (machining force) is controlled during surface machining. The z direction shown in FIGS. 2-4 is typically perpendicular to the workpiece surface being machined and is also the direction of action of the controlled contact force. Inaccuracies in the machine tool's z-direction are compensated for by force control; the machine tool is always pressed against the workpiece with a defined and controlled force. Therefore, inaccuracies in the machine tool's position, which are the result of deformation of elastic elements (e.g., rubber washer 20), are practically insignificant. Furthermore, these errors are essentially automatically corrected by force control. However, rotational moments that may act on the quick clamping system do not cause substantial tilt or xy displacement of the tool holder 30 relative to the chuck 10, since these movements are prevented by the cylindrical pin 11 guided in the hole 33. In other words, the rotational moments are absorbed by the quick clamping system. The only degree of freedom is a (very small) elastic displacement in the z direction, which is compensated for by force control as described above.

[0028] Finally, the positions of the hook 32 and the clamping bracket 13 are interchangeable, but in practice the clamping bracket (mounting plate 13 of the tool holder 30) 31It is more appropriate to mount the pins on the base plate of the chuck 10 (rather than on the base plate itself). Similarly, it does not matter whether the cylindrical pins are immobile relative to the base plate 15 of the chuck 10 and pass through holes 33 in the mounting plate 31, as shown in FIG. 2, or whether the cylindrical pins are fixed (e.g., screwed) to the mounting plate 31 and pass through corresponding holes in the chuck 10. Furthermore, the pins (11) do not necessarily have to be separate components; theoretically, they could be made integral with the base plate 15 or the mounting plate 31 (although this could make manufacturing more complicated). In this case, the base plate (or mounting plate) and the pins would be an integrated part. Furthermore, the pins do not have to be cylindrical. They can have any shape that can engage with a corresponding hole in the opposite part to prevent movement in a plane parallel to the base plate while allowing slight movement in the perpendicular direction.

[0029] In another example, the linear actuator 90, together with the quick clamping system and machine tool, is not attached to a manipulator (industrial robot) but to a stationary base. In this case, the robot holds a workpiece and positions it so that the machine tool can contact and process the workpiece. The robot operates under position control, moving the workpiece along a predetermined trajectory during processing, while the linear actuator 90 attached to the fixed base performs force control and presses the machine tool against the workpiece held by the robot. An example of such a system that does not include a quick clamping system is described in US 2018 / 126512 A1 (Patent Document 1). [Explanation of symbols]

[0030] 11...pin 12, 33...holes 13...Clamp bracket 13, 32...Clamp joint 15...Base plate 20...Elastic member 30...Tool holder 31...Mounting plate 32...Hook 50…Machine tools 60...Workpiece 80...Manipulator 86...End effector flange 86, 91...Flanges 90...Linear actuator

Claims

1. a chuck (10) having a base plate (15) configured to be attached to a flange (86, 91) that can be positioned by force control using a manipulator (80, 90) or a linear actuator (90); a tool holder (30) configured to be attached to a machine tool, the tool holder having a mounting plate (31) adjacent to a base plate (15) in a locked state; a plurality of pins (11) configured to align the mounting plate (31) with the base plate (15) in an attached state and to prevent movement of the mounting plate (31) relative to the base plate (15) in a plane parallel to the base plate (15); At least one elastic member (20) having a washer of elastic material disposed between the base plate (15) and the mounting plate (31); a clamp coupling (13, 32) configured to lock the tool holder (30) to the base plate (15) of the chuck (10), wherein in a locked state, the elastic member (20) of the clamp coupling (13) deforms to apply a pretension force between the base plate (15) and the mounting plate (31); Quick clamping system.

2. 2. The quick clamping system according to claim 1, wherein the clamping connection comprises a plurality of clamping brackets (13) and a plurality of hooks (32) respectively assigned to the clamping brackets (13).

3. The hook (32) is attached to the tool holder (30), and the clamp bracket (13) is pivotally supported on the base plate (15), or 3. The quick clamping system according to claim 2, wherein the hook (32) is attached to the base plate (15), and the clamping bracket (13) is rotatably supported on the tool holder (30).

4. the pins (11) extend into corresponding holes in the mounting plate (31) in the mounted state; and / or 4. A quick clamping system according to any one of claims 1 to 3, wherein the pins (11) extend into corresponding holes in the base plate (32) when mounted.

5. 4. The quick clamping system of claim 1, wherein the pin (11) is attached to the flange (86, 91) and extends through corresponding holes (12, 33) in the base plate (15) and the mounting plate (31).

6. 6. A quick clamping system according to any one of claims 1 to 5, wherein the clamping connection (13, 32) has a dead center lock.

7. 1. An apparatus for robotically assisted machining of a workpiece surface, comprising:

7. A quick clamping system according to claim 1, wherein the force-controlled positionable flange is a first flange of the linear actuator (90); a manipulator (80) wherein a second flange of the linear actuator (90) is coupled to an end effector flange (86) of the manipulator (80); and The manipulator (80) is position-controlled and configured to position the linear actuator (90) relative to the workpiece (60) together with a machine tool (50) coupled to the linear actuator (90) by the quick clamping system, and the linear actuator (90) is configured to adjust the force between the machine tool (50) and the workpiece (60). Device.

8. 1. An apparatus for robotically assisted machining of a workpiece surface, comprising:

7. A quick clamping system according to claim 1, wherein the force-controlled positionable flange is a first flange of the linear actuator (90); a fixed base to which the second flange of the linear actuator (90) is attached; a manipulator (80) configured to hold the workpiece and position the workpiece relative to a machine tool (50) that is position-controlled and coupled to the linear actuator (90) by the quick clamping system; and The linear actuator (90) is configured to adjust the force between the machine tool (50) and the workpiece. Device.

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