COMPENSATING UNIT FOR AN AUTOMATION SYSTEM

Abstract

Compensating unit for an automation system, in particular for arranging between a handling apparatus and a tool, having a main part and having a fastening part, wherein the fastening part is arranged such that it can be moved in relation to the main part along at least one compensating direction from a basic position into a compensating position, and having spring means for returning the fastening part from the compensating position into the basic position, characterized in that drive means are provided within the compensating unit for the purpose of adjusting the basic position of the fastening part along the at least one compensating direction.

Claims

1. Compensating unit for an automation system , having a main part and having a fastening part, the fastening part being arranged such that it can be moved in relation to the main part along at least one compensating direction from a basic position into a compensating position, and having spring means for returning the fastening part from the compensating position into the basic position, drive means are being provided within the compensating unit for the purpose of adjusting the basic position of the fastening part along the at least one compensating direction, characterized in that at least one of the first and the second drive means each have a drive and a positioning element which can be axially shifted in the respective x-direction or y-direction by means of the respective drive, at least one of the first and the second drive being designed as a rotary drive which has a drive pinion and the positioning element being designed as a rack which engages with the drive pinion.

2. Compensating unit according to claim 1, characterized in that a control unit is provided for controlling the drive means on the basis of the forces and/or moments acting on the compensating unit.

3. Compensating unit according to claim 2, characterized in that the control unit is further set up in such a way that it determines the forces and/or moments acting on the compensating unit on the basis of the positional deviation of the compensating position from the basic position.

4. Compensating unit according to any of the preceding claims, characterized in that the fastening part is arranged such that it can be moved into a by means of activating the drive means along an x-direction extending perpendicularly to the longitudinal axis of the fastening part and along a y-direction extending perpendicularly to the longitudinal axis of the fastening part and to the x-direction.

5. Compensating unit according to claim 4, characterized in that the fastening part has a first plane which is arranged such that it is guided in the x-direction on the main part and can be moved along the x-direction when a first drive means is activated, and in that the fastening part has a second plane which is arranged such that it is guided in the y-direction on the first plane and can be moved along the y-direction when a second drive means is activated.

6. Compensating unit according to claim 5, characterized in that the main part has an x-axis guide for guiding the first plane in the x-direction, and in that the first plane has a y-axis guide for guiding the second plane in the y-direction.

7. Compensating unit according to claim 5, characterized in that an adapter coupled to the respective plane for displacing the respective plane in the x-direction or y-direction is provided on the respective positioning element in each case, and the respective adapter being arranged such that it is movably guided in the x-direction or y-direction on the respective positioning element and being arranged such that it is preloaded in the respective basic position by means of the spring means so that said adapter can swerve into the respective compensating direction in order to compensate.

8. Compensating unit according to claim 7, characterized in that the actuator is arranged as a rack which engages with the drive pinion and has a shaft portion, and in that the adapter is displaceably arranged on the shaft portion, the adapter being arranged between two spring elements in such a way that it is pushed into the basic position by the spring elements and can swerve into the compensating position against the spring force of the spring elements.

9. Compensating unit according to claim 8, characterized in that the adapter of the first drive means is driven by the first drive in the x-direction and is directly movement-coupled to the first plane in the x direction.

10. Compensating unit according to claim 8, characterized in that the adapter of the second drive means has a first adapter part which is guided in the y-direction on the positioning element and has an adapter guide extending in the x-direction, and a second adapter part which is guided so as to be freely movable in the x-direction along the adapter guide, whereby the second adapter part being movement-coupled to the second plane in the y-direction.

11. Compensating unit according to claim 8, characterized in that the positioning element of the first drive means and the positioning element of the second drive means form an angle of 90° .

12. Compensating unit according to claim 8, characterized in that the drives are designed as motors, the longitudinal axes of the two motors being arranged so as to extend in parallel with one another.

13. Compensating unit according to claim 1, characterized in that a controllable locking unit for locking the fastening part relative to the main part is provided in the main part.

14. Compensating unit according to claim 1, characterized in that position sensors are provided for detecting the position of the fastening part in the respective compensating direction.

15. Automation system having a handling apparatus and a tool, a compensating unit according to claim 1 being provided between the handling apparatus and the tool.

16. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In the drawings:

[0032] FIG. 1 shows an automation system according to the invention having a compensating unit according to the invention and a tool;

[0033] FIG. 2 shows the compensating unit according to FIG. 1 in an inclined view from below;

[0034] FIG. 3 shows the compensating unit according to FIG. 1 without side panels in an inclined view from above;

[0035] FIG. 4 shows the compensating unit according to FIG. 1 with dismantled planes,

[0036] FIG. 5 shows the plan view of the main part of the compensating unit according to FIG. 4 without a fastening part and a locking unit;

[0037] FIG. 6 shows the main part according to FIG. 5 without drives having position sensors;

[0038] FIG. 7 shows a longitudinal sectional view along the line VII in FIG. 5;

[0039] FIG. 8 shows a view according to FIG. 6 without the drive means but having a locking unit;

[0040] FIG. 9 shows a control structure for controlling an automation system according to the invention having a compensating unit according to the invention;

[0041] FIG. 10 shows a process diagram for the control sequence of the compensating unit according to the invention; and

[0042] FIG. 11 shows a course of the trajectories of the tool and the handling apparatus during active regulation.

DETAILED DESCRIPTION

[0043] A compensating unit 12 arranged on an automation system 10 is shown in FIG. 1. The compensating unit 12 is arranged between a handling apparatus in the form of a robot arm 14 and a tool 16 in the form of a gripping device. As is clear from FIG. 2, the underside, i.e., the fastening part 20, of the compensating unit 12 has a fastening portion 21 having fastening holes for fastening the gripping device 16. As is particularly clear from FIG. 3, the compensating unit 12 has a flange portion 17 on its side facing the robot arm 14, which flange portion can be mounted on or fastened to the free end of the robot arm 14. The compensating unit 10, or its main part 18, has a longitudinal axis 26 which extends in the z-direction and, as is clear from FIG. 1, lies in the longitudinal axis 28 of the link of the robot arm 14 to which the main part 18 is attached.

[0044] The compensating unit 12 which is shown in more detail in FIGS. 2 to 8 has a main part 18 which can be clearly seen in FIGS. 3 to 4 as well as a fastening part 20 which is movably arranged relative to the main part 18. The fastening part 20 comprises a first plane 22 and a second plane 24. The arrangement of the two planes 22 and 24 is such that the plane 22 is arranged on the main part so that it can be shifted in the x-direction perpendicularly to the z-direction and that the plane 24 is arranged on the second plane 22 so that it can be shifted in the y-direction perpendicularly to the z-direction and the x-direction.

[0045] While the second plane 24 is preferably closed, the first plane 22 has a comparatively large opening 25 in its central region, through which various components which interact with the second plane 24 can engage in the assembled state. These components are, in particular, an adapter 44, which is described below, and a locking unit 80, which is shown in FIG. 8 and is also described below.

[0046] As is clear from FIG. 4, an x-axis guide 28 is provided on the main part 18, which x-axis guide supports the first plane 22 so that it can move in the x-direction. The x-axis guide 28 has guide rails 30 arranged on the main part 18 and guide carriages 32 which are displaceably arranged thereon and are firmly fastened to the first plane 22 in the assembled state. To guide the second plane 24 in the y-direction, a y-axis guide 34 is provided on the first plane 22, as is also clear from FIG. 4. The y-axis guide 34 has, like the x-axis guide 28, guide rails 30 but these extend in the y-axis guide 34 and in the y-direction. As shown in FIG. 4, guide carriages 32 which can be shifted in the y-direction and are fastened to the second plane 24 in the assembled state are provided on the guide rails 30 of the y-axis guide 34. As a result of the design described, the fastening part 20, or the second plane 24 according to the arrow 25 in FIG. 3 in the x-direction and according to the arrow 27 in the y-direction, can be moved from a basic position to a compensating position. The movement in the x-direction takes place by shifting the first plane 22 relative to the main part 18 and the shift in the x-direction takes place by shifting the second plane 24 relative to the first plane 22.

[0047] Spring means 36, which can be clearly seen in FIG. 5, are provided to cause the fastening part 20, or the two planes 22, 24, to return from the compensating position to the basic position. The spring means 36 comprise a first pair of coil springs 38 which interacts with the first plane 22 via an adapter 40. The spring means 36 also comprise a second pair of coil springs 42 which interacts with the second plane 24 via a second adapter 44. The adapters 40, 44 are each held between the pairs of coil springs 38, 42 under preloading, with it being possible for said adapters to be moved in the x-direction or y-direction when the respective spring force is exceeded.

[0048] The adapter 40 is therefore spring-loaded along the double arrow 46, as shown in FIG. 5, but can be slid in the x-direction.

[0049] As is particularly clear from FIGS. 5 and 6, the adapter 44 comprises a first adapter part 48 which is mounted so as to be displaceable in the y-direction and is acted upon by the coil springs 44, and a second adapter part 50 which is mounted so as to be freely displaceable in the x-direction on the first adapter part 48 by means of an adapter guide 52. The second adapter part 50 can move the second plane 24 in the x-direction without interference. In the y-direction, on the other hand, the first adapter part 48, and also the second adapter part 50, is spring-loaded in the basic position due to the coil springs 42 but is arranged displaceably in the y-direction. If the fastening part 20 or the second plane 24 is subjected to a force in the y-direction that is greater than the spring force of the coil springs 22, the adapter 44, or the two adapter parts 48, 50, can be moved along the double arrow 54 in the y-direction from the basic position to a compensating position.

[0050] As is also clear from FIGS. 4 and 5 in particular, the compensating unit 12 has two drive means 56, 58 which can be controlled by a control unit 55, it being possible for the position of the adapter 40 to be shifted in the x-direction by means of the first drive means 56 so that ultimately the basic position of the first plane 22 and the second plane 24, and thus also the basic position of the fastening part 20, can be shifted in the x-direction. The drive means 58 are also arranged in such a way that they can be used to adjust the position of the adapter 44 in the y-direction, and thus the basic position of the second plane 24 or the fastening part 20 in the y-direction. For the sake of clarity, only the two drive means 56 and 58 having the adapters 40 and 44 are shown in FIG. 5; further components in the main part 18 are not shown.

[0051] The drive means 56 and 58 each comprise a drive 60 in the form of an electric motor, the drives 60 each driving a pinion 62 which is arranged so as to be rotatably mounted in a respective pinion housing 64. In the sectional view according to FIG. 7, the pinion 62 of the first drive means 56 can be clearly seen. The pinion 62 engages with a positioning element 66 in the form of a rack guided in the pinion housing 64 in the x-direction, a shaft portion 68 being arranged on the positioning element 66, on which shaft portion the adapter 40 is arranged so as to be freely displaceable in the x-direction by means of a sliding guide. In the sectional view according to FIG. 7, the coil springs 42 can also be clearly seen, each of which is supported on the adapter 40 at one end and acts against a stop provided on the shaft portion 68 at the other end in each case. As already described, the adapter 40 can swerve in the x-direction when subjected to a force that is greater than the preloading force of the coil springs 42. By activating the drive 60 or turning the pinion 62, the basic position of the adapter 40 and thus of the fastening part 20 can be adjusted in the x-direction.

[0052] The drive means 58, which are provided for the purpose of adjusting the adapter 44 in the y-direction, correspond in structure to the drive means 56. A positioning element 66 in the form of a rack having a shaft portion 68 is accordingly mounted in the pinion housing 64 of the drive means 58. In contrast to the drive means 56, the drive 60 in the drive means 58 is driven in rotation via a bevel gear mechanism 70 with the associated pinion 22. This has the advantage that the two drives 60, as is clear from FIG. 5, can be arranged in parallel with one another in the main part 18 in a space-saving manner. The two positioning elements 66, or the racks having the shaft portions 68, form a right angle, as is also clear from FIG. 5.

[0053] For the sake of clarity, the drives 60 and the associated pinions 62 are not shown in FIG. 6. However, FIG. 6 shows two optical position sensors 72 and 74, it being possible for the distance from a reflector element 76 arranged on the first plane 22, and thus the respective position of the fastening part 20 in the x-direction, to be determined by means of the position sensor 72. The reflector element 76 can also be seen clearly in FIG. 4. The distance from the first adapter part 48 in the y-direction is determined by means of the position sensor 74, as a result of which the respective position of the fastening part 20 in the y-direction can ultimately be detected. By providing the position sensors 72 and 74, the respective actual position (compensating position) of the fastening part 20 in the x-direction and y-direction can therefore always be determined.

[0054] The control unit 55 is set up in such a way that it can determine the basic position, which corresponds to the target position of the fastening part 20 in the x-direction and y-direction, in particular via rotary position encoders provided on the drives. From the deviation AL between the actual position determined by means of the position sensor 72, 74, i.e., the compensating position, and the basic position determined via the rotary position encoder, the control unit 55 can use Hooke's law, with a known spring rate c, to determine the force F.sub.x,y acting on the fastening part in the x-direction and y-direction as follows: F.sub.x,y=c*ΔL.sub.x,y

[0055] In order to allow for compensation in the z-direction, it is conceivable for a z-compensating module (not shown in the figures) to be provided on the main part 18, which module has drive means which can be controlled by the control unit 55 for the purpose of adjusting the basic position of the main part in the z-direction. If such a z-compensating module is provided, the control unit 55 can determine the force F.sub.z acting in the z-direction from a deviation in the z-direction ΔLz.

[0056] The control unit 55 is preferably designed in such a way that it controls the drive means 56, 58 on the basis of the forces and/or moments acting on the compensating unit 12. By adjusting the basic position on the basis of the forces and/or moments acting on the compensating unit 12, active force regulation in particular can be made possible. If it is determined that the forces and/or moments acting on the compensating unit 12 are too high and exceed a threshold value, then the drive means 56, 58 can be accordingly controlled in order to avoid overloading and, in particular, damage. It is advantageous if the control unit 55 compensates for the forces and/or moments acting on the compensating unit 12 with a slight delay. The handling apparatus 14 having the tool 16 and the compensating unit 12 follows a preprogrammed path 90 which corresponds to the shape and/or position of the object to be machined or to be handled. A deviation in the shape and/or position of the object results in a change in the force acting on the tool 16 and the compensating unit 12. This change in force results in a positional deviation of the fastening part 20 along the compensating direction from the basic position to the compensating position. Due to the provided spring means 36, 38, 42, the actual force acting on the tool 16 can be deduced from the positional deviation by means of the position sensors 72, 72 via the spring constant c. The determined actual force is compared with the target force. From the comparison, the control unit 55 determines the changed basic position to compensate for the change in force. The control unit 55 controls the drive means 55, 58 in such a way that the basic position is changed according to the calculation while the tool 16 is making contact with the deviation. Consequently, the programmed path 90 of the handling apparatus 14 remains unchanged, whereas the path 91 of the tool 16 and the compensating unit 12 is adapted by the compensating unit 12 to the deviation of the object by means of changing the basic position. The deviation of the paths 90 and 91 therefore result from the change in position of the basic position.

[0057] This is possible, inter alia, in that the position sensors 72 and 74 as well as the drive means 56 and 58 are provided for the purpose of adjustment in the compensating unit 12. The small distance between the deviation contacted by the tool 16 and the adjustable fastening part 20 as well as the drive means 56 and 58 as well as the low inertia of the fastening part 20 in comparison with the inertia of the entire handling apparatus 14 and the low latency with respect to the intervention in the handling control are favorable dynamic properties, and therefore the active force regulation can be carried out with a short time delay and load changes in the range of the compensating position caused by deviations can be compensated for by the compensating unit 12.

[0058] Furthermore, the control unit 55 is set up in such a way that when an object is moved over it several times, deviations of the object that have already been determined after the first contact are taken into account, and therefore the basic position is adjusted beforehand for each further contact.

[0059] The main part 18 is shown in FIG. 8 without the drive means 56 and 58 and without the position sensors 72 and 74. A locking unit 78 is shown in the central region of the main part 18, which unit has a locking part 80 that can be shifted in the z-direction. The arrangement is such that the locking part can be acted upon in the z-direction against the underside of the second plane 24 so that it is fixed in its respective position by frictional locking. The axial shift of the locking part 80 can preferably take place pneumatically or magnetically.

[0060] A control structure for controlling the automation system 10 by means of a force controller 92 and a servo controller 93 is shown in FIG. 9. The target force F.sub.des acting on the tool 16 can be set depending on the service life to be achieved for the tool 16 or the process and represents the reference variable. The true actual force F.sub.act can be determined from the shift of the fastening part 20 and the spring rate c of the spring means 36, 38, 42, the actual force corresponding to the control variable. The control difference from the target force F.sub.des and the actual force F.sub.act is supplied to the force controller 92. The force controller 92 determines, using the target speed ;x.sub.a, the positioning variable which serves as a reference variable for the servo controller 93. As a further control difference, the target speed ;x.sub.a of the force controller 92 and the target speed ;x.sub.TG of the trajectory planner 94 of the tool calculates the target speed ;x.sub.des of the active system. The target speed ;x.sub.des of the active system is supplied to the servo controller 93 for controlling the drive means 56, 58. Alternatively, the speed controller can also intervene on the current or position plane in the servo control structure.

[0061] In addition to the control structure shown in FIG. 9, FIG. 10 shows a block diagram which shows the control sequence when contact is made with a deviation in the position or shape of a component by the tool 16. According to step S1, the coupling of the fastening part 20 to the tool 16 causes both the tool 16 and the fastening part 20 to be shifted when there is an unevenness. Due to the interaction of the fastening part 20 and the spring means 36, 38, 42, there is a relationship between the shifting of the fastening part 20 and the actual force acting on the tool 16 via the spring constant c of the spring means 36, 38, 42 in step S2. Subsequently, in step S3, the determined actual force is compared with a definable target force. The difference results, for example, in an increase in force which is transformed into a speed to be compensated for in step S4. In step S5, the speed to be compensated for is offset against the speed which corresponds to the trajectory. The target speed resulting from this is used in step S6 to control the drive means for shifting the basic position.

[0062] A two-dimensional coordinate system is shown in FIG. 11 for a simple illustration of the functioning of the compensating unit 12. The coordinate system can have up to 6 dimensions. In the coordinate system, a preprogrammed path 90 of the handling apparatus 14 is shown as a continuous line between the axes, which line corresponds to an object to be machined. The paths 90, 91 represent the movement of the handling apparatus 14 and the tool 16. The path 91 of the tool 16 is shown as a separate dashed line, this path 91 substantially coinciding with the path 90 of the handling apparatus 14. In addition, the path 91 of the tool 16 would correspond completely to the path 90 of the handling apparatus 14 if regulation by the compensating unit 12 is not activated. In this case, if the object deviates, an undesirable change in force occurs. The change in force is compensated for by the compensating unit 12 with active regulation. This is shown in FIG. 10 where a difference between the dashed line, path 91 of tool 16, and the solid line, path 90 of handling apparatus 14, can be seen. The two deviations result in the compensating unit 12 changing the basic position so that the path 91 of the tool 16 is adapted to the deviation of the object. Consequently, without changing the path 90 of the handling apparatus 16, there is no change in force despite deviation on the object by only the fastening part 20 and the tool 16 being adjusted in their path 91.