Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
  • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
  • B25J9/00—Programme-controlled manipulators
  • B25J9/16—Programme controls
  • B25J9/1679—Programme controls characterised by the tasks executed
  • B25J9/1692—Calibration of manipulator
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
  • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
  • B25J9/00—Programme-controlled manipulators
  • B25J9/003—Programme-controlled manipulators having parallel kinematics
  • B25J9/0054—Programme-controlled manipulators having parallel kinematics with kinematics chains having a spherical joint at the base
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
  • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
  • B25J9/00—Programme-controlled manipulators
  • B25J9/16—Programme controls
  • B25J9/1615—Programme controls characterised by special kind of manipulator, e.g. planar, scara, gantry, cantilever, space, closed chain, passive/active joints and tendon driven manipulators
  • B25J9/1623—Parallel manipulator, Stewart platform, links are attached to a common base and to a common platform, plate which is moved parallel to the base
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
  • G05B2219/00—Program-control systems
  • G05B2219/30—Nc systems
  • G05B2219/39—Robotics, robotics to robotics hand
  • G05B2219/39018—Inverse calibration, find exact joint angles for given location in world space
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
  • G05B2219/00—Program-control systems
  • G05B2219/30—Nc systems
  • G05B2219/39—Robotics, robotics to robotics hand
  • G05B2219/39019—Calibration by cmm coordinate measuring machine over a certain volume
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
  • G05B2219/00—Program-control systems
  • G05B2219/30—Nc systems
  • G05B2219/39—Robotics, robotics to robotics hand
  • G05B2219/39024—Calibration of manipulator
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
  • G05B2219/00—Program-control systems
  • G05B2219/30—Nc systems
  • G05B2219/39—Robotics, robotics to robotics hand
  • G05B2219/39032—Touch probe senses constraint known plane, derive kinematic calibration
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
  • G05B2219/00—Program-control systems
  • G05B2219/30—Nc systems
  • G05B2219/39—Robotics, robotics to robotics hand
  • G05B2219/39044—Estimate error model from error at different attitudes and points
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
  • G05B2219/00—Program-control systems
  • G05B2219/30—Nc systems
  • G05B2219/39—Robotics, robotics to robotics hand
  • G05B2219/39552—Stewart platform hand, parallel structured hand
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
  • G05B2219/00—Program-control systems
  • G05B2219/30—Nc systems
  • G05B2219/40—Robotics, robotics mapping to robotics vision
  • G05B2219/40267—Parallel manipulator, end effector connected to at least two independent links
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
  • G05B2219/00—Program-control systems
  • G05B2219/30—Nc systems
  • G05B2219/50—Machine tool, machine tool null till machine tool work handling
  • G05B2219/50162—Stewart platform, hexapod construction

Definitions

• the invention relates to a method for use-related calibration of parallel kinematics having a programmable control and an arrangement for carrying out this method.
• So-called parallel kinematics in particular hexapods, which are also known as Stewart platforms, are used, among other things, in the high-precision positioning of parts in production processes, and their area of application has expanded dramatically in recent years. For newly developed areas of application, such as in semiconductor technology and the manufacture of integrated circuits, the highest level of accuracy is required.
• US 2013/0006421 A1 discloses an arrangement for use-related calibration of parallel kinematics having a programmable control, with a pose marking body and a kinematic coupling for the detachable, tilt-proof attachment of the pose marking body on the platform of the parallel kinematics in a clearly defined position and angular position.
• Corresponding arrangements can also be found in publications WO 2010/128 441 A1, DE 10 2018 124 898 A1 and DE 198 58 154 A1.
• the reference coordinate systems of a parallel robot are those coordinate systems to which the commanded poses refer. Usually there is an excellent reference coordinate system, which is given in the construction plans, but the exact position can be moved to another place depending on the calibration method. If at one parallel robot, none of the reference coordinate systems is designated as a canonical reference coordinate system, one of the reference coordinate systems is arbitrarily designated as a canonical reference coordinate system since a designated reference coordinate system is designated in this specification.
• the reference coordinate system defines the pivot point in the zero pose through its zero point, and through its orientation it defines both the Cartesian directions of movement and the zero angles to which the specification of the Euler angles refers.
• a pose marker is a marker on a rigid body that can be used to measure a pose in space relative to a reference pose of that rigid body.
• Pose markers make it possible to attach a coordinate system to a rigid body, the origin and orientation of which can be metrologically determined from the pose marker.
• three non-linearly arranged balls that are firmly connected to the rigid body are suitable as pose markers.
• the coordinates of their centers can be used to determine the position of an attached coordinate system.
• Another pose marking can be realized by a fixed cube, since a coordinate system can already be fixed to three pairs of non-parallel planes.
• a space registration is a prescription for how rigid bodies are assigned a pinned coordinate system based on their pose tag.
• a spatial registration can be used to assign a pose to a rigid body that has a pose tag, provided a reference coordinate system exists in which to define its pose.
• a coordinate system can be grasped if its position and orientation in relation to a spatial registration is defined by a coordinate transformation.
• Tangible reference coordinate system A tangible reference coordinate system of a parallel robot is a coordinate system whose origin coordinates and orientation relative to the first coordinate system of a calibration artifact can be specified when it is connected to the nacelle by a kinematic interface and the parallel robot has assumed a designated distinguished pose, which is usually its initialization pose.
• Kinematic interfaces are devices for the rigid and detachable connection of two rigid bodies, whereby the two rigid bodies can be fixed in the same pose against one another in an exactly reproducible and deterministic manner.
• This device consists of two coordinated parts, referred to in this document as interface parts, each of the two rigid bodies to be connected to one another having such an interface and the connection being effected by the kinematic interface.
• the interface parts are matched to each other, according to the "plug and socket" concept in electrical engineering. It is essential that the plug and socket can be coupled to one another in exactly one way, which rules out symmetries such as with a Euro plug.
• Interface parts are functional equipment of rigid bodies. Kinematic interfaces are used to create a rigid connection between two rigid bodies, resulting in a new rigid body. To do this, each of the two rigid bodies must have an interface part. Kinematic interfaces therefore offer a connection option for rigid bodies. Kinematic interfaces are designed so that the connection is detachable while being as deterministic and reproducible as possible, and the connection is rigid and stiff. The kinematic interfaces should be dimensionally stable against forces and moments. A first class of kinematic interfaces is called "kinematic coupling". In a preferred embodiment of the invention, “kinematic couplings" are used.
• kinematic couplings of the "Maxwell coupling” type are used, referred to in this document as "three groove kinematic coupling".
• Three groove kinematic couplings are used as an example in the exemplary embodiments and figures without loss of generality.
• a “three groove kinematic coupling” is shown in FIG.
• Each of the three balls of the ball part has a point contact at two points of a groove of the groove part when there is a form fit, so that there is contact at six points when there is a form fit. There is then a static determinateness.
• This first class of kinematic interfaces are statically determinate and therefore offer the highest accuracy and utility within the scope of the invention.
• a second class of kinematic interface is called “quasi-kinematic coupling”.
• kinematic interfaces of this class are used according to the invention.
• a third class of kinematic interfaces are those that can neither be assigned to the class of "kinematic couplings" nor to the class of "quasi-kinematic couplings".
• kinematic interfaces of this type are used. These interfaces are mostly form-fitting connections.
• the interface parts of the kinematic interface are clearly referred to in this document as a ball part or groove part, corresponding to the interface parts in "three groove kinematic coupling".
• An interface bearing artifact is a rigid body fitted with an interface piece. reference artifact
• a datum artifact is an interface-carrying artifact that has a pose marker that is accompanied by a spatial registration. So it has a defined, pinned coordinate system, which is referred to as the first coordinate system of the reference artifact.
• Reference artifacts can be cuboids whose outer faces represent a pose marker.
• the cuboids can be suitable for moving an applied mass.
• plate-shaped cuboids can have markings embossed on their upper side with regard to their spatial marking, in the direction of the outer surfaces.
• the pose marking consists of stop surfaces on the plate-shaped cuboids.
• the calibration artifact is, in principle, an arbitrarily selected reference artifact that serves to relate the first coordinate systems of all reference artifacts to one another. Where the location of the first coordinate system of a reference artifact is compared to the location of the first coordinate system of the calibration artifact, represented as a datum of 6 real numbers describing a coordinate transformation, is a datum inherent to each reference artifact. If a reference artefact registered in this way is attached to the groove part of a "three groove kinematic coupling", then a coordinate system can be defined based on its pose marking, the position of which in relation to the calibration artefact is known. The position of the reference coordinate system can thus also be determined if its Location relative to the calibration artifact is known.
• a fixture artifact is a reference artifact used to hold, for example, a tool (fiber fixture clamp, probe fixture, milling cutter fixture), workpiece, or gauge.
• the effective location of the tool, the coordinate system of the workpiece or the measurement location of the measuring device is referred to here as the second coordinate system of the mounting artifact.
• the benefit of such an artifact lies in the fact that the second coordinate system of the mounting artifact always points directly to the Reference coordinate system of the respective hexapod can be specified.
• the coordinate transformation between the first and second coordinate system of a mounting artifact can usually be determined using a coordinate measuring machine. As a rule, one can dispense with the use of the pose marking of the mounting artifact, one then considers the tool, the workpiece or the measuring device itself as a pose marking based on its shape, so that the first and second coordinate systems coincide.
• a further preferred embodiment of mounting artifacts are mirror mounts whose surface normal is aligned in relation to the calibration artifact. These mirror artifacts facilitate interferometric measurements on the hexapod, since the mirror can be aligned according to the laser beam alignment. Artifacts of this kind make it easier to qualify hexapod accuracies. Since the control of hexapods can read its leg lengths and use this to calculate the pose of a hexapod, hexapods are themselves pose detection devices. This makes it possible to specify the normal vector of the mirror in the reference coordinate system even if the hexapod itself is not in its initialization pose, but has been aligned with a laser beam.
• a further preferred embodiment of mounting artifacts are geometric bodies, which are used to align the hexapod with the coordinate system of an apparatus or an arrangement, in that these bodies define the effective site of a measurement or manipulation.
• these bodies define the effective site of a measurement or manipulation.
• the coordinate system mentioned can be related to the reference coordinate system of the hexapod.
• mounting artifacts are geometric bodies that serve as a stop in order to relate world coordinate systems to the reference coordinate system of the hexapod.
• plates with defined contact surfaces or edged rods should be mentioned.
• reference artifacts can be constructed in such a way that tools, stops, workpieces are fastened in an adjustable and lockable manner in order to make the use of the mounting artifact more flexible.
• An example would be the ball head clamps used in camera mounts. After such a displacement of stops, etc., a new reference to the calibration artifact must be established with a pose measuring device.
• Mount artifacts are datum artifacts by definition, so they have a pose marker.
• the functionality would also be given without pose marking, for example in the case of mirror-bearing mounting artifacts, in which only the normal vector of the mirror or mirrors is relevant.
• artifacts derived from them that do not have a pose marking can also be used within the meaning of the invention.
• Movements in the visual space also viewed and referred to as coordinate transformation depending on the context, form a group, the special Euclidean group.
• This mathematical group property can be used without restriction in the inventive use of reference artifacts and mounting artifacts for making the reference coordinate system tangible.
• Reference coordinate systems of hexapods, first coordinate systems of different reference artifacts, etc. can therefore be related to one another in a simple manner.
• Fig. 14 to Fig. 16 representations for the use of the invention in parallel robots and 17 is an illustration of an example reference artifact.
• Figures 1 to 3 are perspective views of a hexapod. Drawings of this type can be found in the hexapod technical manuals.
• the position of the coordinate system referred to here as the reference coordinate system, which is drawn in FIGS. 1 and 3, is of particular importance.
• This reference coordinate system defines the so-called pivot point, i.e. the point around which the upper platform rotates when rotary movements are commanded.
• the orientation of this coordinate system defines the zero angles for all angular movements.
• the coordinate axes of the coordinate system define the directions of the Cartesian movements.
• the position and orientation of the reference coordinate system must be known. In this context, reference is made in the prior art to drawings, similar to those in FIG. 1 to 3, with the drawings in the manuals also containing dimensions.
• the horizontal plane of the origin of the reference coordinate system lies on the lower surface of the cylindrical nacelle.
• this height can be found through the difference between the overall height and the thickness of the gondola. The same procedure must be followed with regard to the top side of the gondola.
• the zero point is still rotationally symmetrical to the cylindrical cover plate, shown in FIG. point direction.
• a hexapod If a hexapod is now used, then one requires movements in an external coordinate system, which is given, for example, by an experimental setup, or movements/alignments with respect to a coordinate system, which is attached to the platform, such as that of a Fiber optic mount during fiber alignment. It is therefore important to be able to specify the position and orientation of the reference coordinate system in relation to a given coordinate system so that movements can take place in a given coordinate system.
• the reference coordinate system can be brought into relation with other coordinate systems using measuring aids such as calipers for applications with low demands on the positioning accuracy.
• the procedure mentioned is inadequate.
• highly precise dimensional tolerances are only specified for the kinematically relevant components.
• the kinematically relevant components are specifically the upper and lower leg joints and their position vectors in the reference coordinate system, which are referred to as pivot points.
• the base plate and the cover plate only have the function of connecting these pivot points in a rigid body and are therefore not manufactured with great precision.
• the outer shapes of the hexapod only provide a rough indication of the position and orientation of the reference coordinate system, which must lead to imponderable uncertainties in the position and orientation of the reference coordinate system of the hexapod with respect to the outer coordinate systems.
• FIG. 1 The position of the pivot points relative to the reference coordinate system is shown in FIG.
• a hexapod is shown schematically, whose legs end in ball joints, whose sockets lie in the nacelle and the base plate.
• the tasks in connection with the kinematic accuracy lie exclusively in the precise determination of the 12 position vectors of the sphere centers with regard to the constructively specified reference coordinate system.
• kinematic calibrations of hexapods are based on a large number of measurements of commanded poses using a pose detection device and subsequent evaluation in which the measured poses are compared with the commanded poses.
• the coordinate system of a pose detection device is an auxiliary coordinate system whose position and orientation in space can in principle be defined arbitrarily and which no longer has any significance after the evaluation of the pose measurements.
• the information about the position of this coordinate system, which survives the evaluation, consists of approximate information about the position of individual assemblies of the hexapod if they were recorded with the antics recording device.
• the temporary coordinate system of the pose detection device is not precisely recorded in the course of the calibration in relation to a persistent, tangible coordinate system of the hexapod. From this it immediately follows that even after a calibration, the directions of movement of the hexapod and the position of its pivot point in particular can only be specified more or less vaguely.
• the question of a tangible coordinate system does not arise with serial robots in this form, because the poses of all their moving limbs are part of a single kinematic chain and must be known in order to implement the end effector pose, with the poses of each individual limb being based on the pose of the preceding limb and wherein the reference coordinate systems of the individual limbs have physical embodiment in the joints between the limbs.
• Parallel robots should realize poses. This is described by bringing a coordinate system, which is identical to the reference coordinate system of the parallel robot in the initialization pose, into coincidence with a second predetermined coordinate system by means of a general movement in space (rotation and translation).
• 6 common parameters are selected for parameterizing the position of this second coordinate system.
• the first three parameters specify the Cartesian shift and are denoted by X,Y and Z
• the last three parameters specify the cardan angle and are denoted by U,V and W.
• pose markings For this purpose, carried coordinate systems defined by means of pose markings are established. These pose markings can either be derived from the external shape of the nacelle, be stamped into the nacelle, or sit on a rigid body that is attached to the nacelle.
• poses After the measurements of the pose-transformed coordinate systems of the pose markings, poses must be assigned to these coordinate systems.
• the pose markings are related to a constructively provided reference coordinate system of the hexapod. This is improvised in the prior art by makeshift measurements and estimates, since this reference coordinate system has no physical embodiment.
• the planar surface of the nacelle defines a Z-direction through its plumb vector, engraved lines 201 on the nacelle top point in the X and Y directions, and the origin of the reference coordinate system lies on the Z-axis in defined Distance to the flat surface of the gondola. Additional features such as a cable connector 202 distinguish X-direction from Y-direction.
• the nacelle is not a suitable reference body to which a coordinate system can be attached, since the top of the nacelle, as a machine part, is neither extremely flat nor is it manufactured with high precision. There is also no stop to accurately position a rigid body on the platform. As explained above, all this leads to pose errors, since there is no suitable pose marking and therefore there is no precise coordinate transformation to the reference coordinate system.
• WO 2017/064 392 A1 describes how all relevant geometry parameters of a Stewart platform can be determined, ie the kinematically relevant data of the hexapod should ideally ultimately be available with high-precision measurements. If one assumes the success of such a calibration in an ideal manner, the calibration would have been carried out perfectly in view of the prior art, and the positioning of the parallel robot would theoretically also be completely error-free.
• the invention recognizes prerequisites that are essential for high-precision positioning with parallel kinematics, but are not met in the prior art.
• the invention specifies these requirements and discloses devices and methods with which they can be met.
• Fig. 5 shows a so-called “three groove kinematic coupling", which consists of two parts, namely a groove part 501, which has three grooves 501a, 501b, 501c, and a ball part 502, which has three balls 502a, 502b, 502c.
• the first coordinate transformation is that between the first coordinate system of the calibration artifact and the first coordinate system of the reference artifact.
• the second coordinate transformation is that between the reference coordinate system of the robot individual and the first coordinate system of the calibration artifact. Both coordinate transformations must be known to the robot's controller.
• the coordinate transformation between the first coordinate system of a calibration artifact and the first coordinate system of the reference artifact is independent of the robot individual.
• the coordinate transformation between the first coordinate system of the calibration artifact and the reference coordinate system of a robot specimen can be achieved in two different ways.
• a reference artifact is already used during calibration, so that this coordinate transformation can be defined or determined during calibration, see FIGS. 10 to 12.
• the calibration is carried out using a mapping method, the reference coordinate system on which the mapping function is based of the mapping function based on the first coordinate system of the calibration artifact result in the coordinate transformation.
• the underlying reference coordinate system with the first coordinate system of the calibration artifact would also be the one sought when determining the parameters result in coordinate transformation.
• a calibration in the manner of such a parameter selection leaves this possibility open.
• the misleading way of speaking of "parameter identification" for a calibration by "correcting" geometry parameters only apparently excludes such a possibility, because the so-called parameter identification uses the geometry parameters only as parameters of a fit function, which minimize the error in the poses measured during calibration target
• the gondola already has a pose marker whose spatial registration together with a constructively given coordinate transformation provide the reference coordinate system and thus the determination of the sought-after coordinate transformation between the reference coordinate system and the Allow coordinate system of a calibration artifact, see Fig. 8 and Fig. 9.
• the determination of the desired coordinate transformation can be done, for example, using a coordinate measuring machine that detects the pose marking on the hexapod and also the pose marking on the calibration artifact.
• two reference artifacts can be attached one after the other and the coordinate transformation of the two coordinate systems of the reference artifacts can be determined by measurement.
• the above coordinate transformation between the coordinate systems of two reference artifacts is independent of the individual part of the groove.
• the groove parts do not have to be manufactured with the greatest accuracy. Since no particularly high accuracy requirements have to be placed on the grooved parts, there are no increased costs here.
• the ball parts can be manufactured relatively easily with the highest level of accuracy.
• the balls themselves can be purchased with the highest accuracy, for example as balls for ball bearings or as balls for probes used in coordinate measuring machines.
• the highly precise arrangement in a triangle can be achieved if the balls are, for example, sunk in half into blind holes, whereby they can then be cemented in exactly the desired triangular arrangement using a template.
• the parallel kinematics are brought into the measuring volume of a coordinate measuring machine (CGM), and the first coordinate system of the reference artifact is determined in the coordinate system of the CGM and then the position of its coordinate system in the coordinate system of the CGM is determined using pose markings on the rigid body to be positioned. See Fig. 12.
• CGM coordinate measuring machine
• This provides the coordinate transformation between the body coordinate system and the reference coordinate system of the parallel kinematics.
• a corresponding coordinate transformation can be activated on the controller to move the body in its own coordinate system.
• a mounting artifact such as a fiber mount is used.
• the second coordinate system of this mount is given by a coordinate transformation, based on the first coordinate system of the reference artifact. This allows the coordinate systems of tools, workpieces, measuring devices to be related to the reference coordinate system of the hexapod. If a body is in a holder of a Mounting artefacts, with a corresponding design of the mounting and shape of the body, the coordinate system of this body is also given in relation to the reference coordinate system of the hexapod.
• the nacelle surface must be manufactured with high precision and have directional markings; mounted stops are also possible. Characteristics of the nacelle surface such as the directional vector of the nacelle plane and the direction of the grooves or the position of the stop surfaces are measured with a KGM and related to the reference coordinate system using a reference artifact. If possible, the rigid body is placed or attached to the gondola in a precisely aligned manner. This third option is limited in its accuracy and generally does not make sufficient use of the advantages of the invention.
• Reference artifacts are used, which have flat surfaces for aligning the rigid body and which represent its pose marking. 6 shows the relationships between the various coordinate systems defined in the introduction and their linking transformations.
• Boxes 601 through 610 symbolize coordinate systems, so a coordinate system is shown to the right for identification.
• the drawing to the left of the coordinate system symbolizes the type or purpose of this coordinate system.
• the boxes in which a hexapod is depicted, 607, 608 and 609, represent reference coordinate systems of hexapods.
• the reference artifact boxes, 604, 605 and 606 denote the first coordinate system of a reference artifact.
• Boxes with a tool drawn in here 601, 602 and 603, denote the tool coordinate system of a tool or the coordinate system assigned to a rigid body that is moved along with it.
• the term in the glossary for this is mounting artifact, the coordinate system is referred to above as the second coordinate system of the mounting artifact
• the coordinate system In 601 the coordinate system is between the jaws of a pair of pliers, ie the effective location of a gripper.
• the coordinate system relates to the tip of a cone-shaped material sample to be machined. This material sample is therefore a workpiece.
• the coordinate system relates to the position of a ring coil for measuring magnetic fields, ie to the measurement location of this measuring device.
• the first coordinate system of the calibration artifact 610 is shown in the center of FIG. This calibration artifact does not differ in design and function from other reference artifacts, for example those reference artifacts shown in 604, 605 and 606. However, it has proven to be expedient to choose a reference artifact as the calibration artifact in order to be able to relate comparisons of the pose of the first coordinate system of different reference artifacts to one another in a uniform manner.
• the three coordinate transformations T7, T8 and T9 determined in the course of the application-related calibration determine the positions and orientations of the corresponding reference coordinate system of the respective hexapod through the first coordinate system of the calibration artifact and given the respective predetermined coordinate transformation rule.
• the reference coordinate system of the respective hexapod can also be determined here in relation to the first coordinate system of the respective reference artifact using the reference artifacts 604, 605 and 606 and the three coordinate transformations T4, T5 and T6 as intermediate coordinate transformations.
• the first coordinate systems of reference artifacts can be related to one another at any time by a pose detection device with other first coordinate systems of other usage artifacts by means of a coordinate transformation.
• This reference is indicated by the coordinate transformations T4, T5 and T6 to the calibration artifact.
• These three coordinate transformations provide the basis for the intermediate coordinate transformations mentioned. On the right you can see three reference artifacts as an example.
• the coordinate transformations T4, T5 and T6 between the respective first coordinate systems have been determined according to the invention. Due to the aforementioned mathematical group property, the coordinate transformations between all first coordinate systems of the reference artifacts and specifically also of the calibration artifact can now also be determined in pairs. For example, the coordinate transformation T10 between the first coordinate system 604 and the first coordinate system 605 can be calculated from T4 and T5.
• the coordinate transformation between the first coordinate system of any reference artifact, for example 604, and the use coordinate system 607 can be determined from T4 and T7.
• the coordinate transformation between the first coordinate system of the reference artifact and the calibration artifact is required, as well as the coordinate transformation between the first coordinate system of the calibration artifact and the reference coordinate system of the hexapod.
• the coordinate transformation TU shown can be calculated from TI and T2, for example.
• the coordinate transformation between a first coordinate system of a reference artifact and the first coordinate system of a mounting artifact can also be calculated in this way.
• any reference artifact for which a coordinate transformation to the calibration artifact can be specified can fully assume the role of a calibration artifact.
• the leg lengths for given poses are read out in the hexapod's function as a pose detection device, the associated pose is calculated from this and evaluated as part of the process.
• Each pose mark which is mounted on a hexapod and has the shape of a cuboid, can be positioned analogously to the 3-2-1 rule defined in tolerance management, by bringing 6 surface points into abutment contact.
• the first plane of the cuboid is called the primary plane and brought into contact with three probe tips, the second plane called the secondary plane and brought into contact with 2 probe tips, the third plane finally brought into contact with one probe tip as a tertiary plane. This determines the position of the cuboid in space in its 6 degrees of freedom.
• a suitable device for this stop contacting is shown in FIG.
• the cuboid pose marking can be aligned automatically and iteratively with the six-point pose markings.
• the arrangement of the 6 proximity switches can itself be understood as a pose marking.
• a hexapod with such a reference artifact equipped as a pose marker can work cooperatively in the same coordinate system that has a reference to both reference coordinate systems by rendevous with a hexapod that carries a cuboid-bearing reference artifact.
• the measurement of the transformations is shown in FIG.
• the transformations are collected with the aid of pose detection devices.
• a coordinate measuring machine is used for this purpose, with which pose markings are touched.
• the coordinate system in which the pose detection device measures is shown in black at 708 .
• the exact position of this coordinate system is irrelevant, it has the meaning of an auxiliary coordinate system in the process.
• the box next to this auxiliary coordinate system shows the groove part of a "three groove kinematic coupling".
• No coordinate system can be assigned to an interface part itself.
• the interface part is firmly anchored in the measuring space of the pose detection device and cannot move with respect to the auxiliary coordinate system.
• the groove part of a kinematic interface is fixed in the measuring space of the pose detection device.
• the calibration artefact 707 is placed on this part of the groove and the position of its first coordinate system in the auxiliary coordinate system is determined.
• the same measurements are performed on the other reference artifacts 704, 705, and 706.
• the poses of the second coordinate systems of the mounting artifacts 701, 702 and 703 are also determined. In this way the poses T701, T702, T703, T704, T705, T706 and T707 can be determined immediately, which relate to the auxiliary coordinate system, and the various first and second coordinate systems of the reference artifacts and mounting artifacts can be related to one another.
• a normalization of the transformations T701 to T706 to the calibration artifact is possible with the aid of the transformation T707 of the first coordinate system of the calibration artifact.
• the high-precision manufactured hexapod shown here as an example already has a tangible coordinate system due to the presence of a pose marking 801 designed here as a cuboid.
• the location of the reference coordinate system of the hexapod is given by a coordinate transformation that refers to the reference coordinate system from the spatial registration of the pose marker.
• This well-known coordinate transformation between the spatial registration of the pose marking and the reference coordinate system results from the highly precisely realized kinematically relevant geometry parameters, which also include the pose marking.
• the float marking is attached to the base plate here, it is also possible to attach such a marking to the gondola.
• the type of pose marker is also selectable, for example flat surfaces in high precision orientation attached to the platform could form a pose marker, or three non-collinear spheres.
• the high-precision production mentioned refers to the position of the kinematically relevant components, in particular the position vectors and direction vectors of the joints.
• the position and orientation of the pose marker must also be defined with high precision in the same coordinate system.
• FIG. 9 shows how the coordinate transformation between the first coordinate system of the calibration artifact and the reference coordinate system of the hexapod can be implemented on a pose detection device.
• the coordinate system 906 represents the coordinate system of the pose detection device.
• the pose TX5 of the coordinate system 905 of the pose marker 801 and the pose TX4 of the first coordinate system of the calibration artifact 903 are measured.
• the coordinate transformation TX1 which represents the relationship sought between the reference coordinate system 902, 904 of the hexapod 907 and the first coordinate system 903 of the calibration artifact 801, i.e. the coordinate transformation between the coordinate systems 903, 901 and 904, can be determined as follows:
• the pose TX4 of the first coordinate system 903 of the reference artifact is measured with respect to the coordinate system of the pose detection device.
• the coordinate systems 903, 904 and 905 are drawn in black because they relate to the auxiliary coordinate system 906.
• the pose TX5 of the pose marking of the hexapod with respect to the auxiliary coordinate system 906 is measured in an analogous manner.
• This coordinate transformation is combined with the coordinate transformation TX2, so that the pose of the reference coordinate system is given in relation to the auxiliary coordinate system.
• Kinematic calibration measurements are based on the measurement of the hexapod poses in a large number of different poses, the calibration being intended to bring about a correction of the pose deviations, which consists of a comparison of the measured poses with the commanded poses.
• the pose commands must be based on a reference coordinate system in order to be able to define poses.
• the platform is then commanded into a variety of poses with the calibration artifact attached to the hexapod.
• a few example poses taken by the calibration artifact are shown in FIG.
• the first current coordinate system 1101, 1102, 1103, 1104, 1105, 1106 of the attached calibration artifact becomes one with respect to the coordinate system pose detection device measured as shown in FIG.
• the number of pose measurements required for calibration is usually three digits.
• the pose of a reference coordinate system in the coordinate system of the pose detection device is now calculated from the large number of measured poses by means of a compensation calculation, and this is related to the position of the first coordinate system of the calibration artifact in the initialization pose of the hexapod. This defines the position of the reference coordinate system in relation to the first coordinate system of the calibration artifact.
• the reference coordinate system is established as described, it is tangible since it is related to the pose of the first coordinate system of the calibration artifact.
• a calibration is then carried out on the basis of the measurement results and the reference coordinate system. This calibration is intended to ensure that the deviations of the commanded poses from the measured poses are minimized or eliminated.
• Rigid bodies can be permanently mounted on the nacelle.
• kinematic couplings are unsuitable for transmitting large forces and moments, which is why it may be necessary to mount a body directly on the nacelle.
• quadsi-kinematic couplings can transmit larger forces and moments, but are not kinematically intended and for Less suitable for high-precision applications than kinematic couplings.
• a workpiece or a sensor is connected to the platform with a non-positive connection (frictional connection), for example using machine screws, or with a material connection (e.g. adhesive bonding, welding, soldering), the exact pose of the body placed on it is in relation to the reference coordinate system of the hexapod initially determined imprecisely.
• a non-positive connection for example using machine screws
• a material connection e.g. adhesive bonding, welding, soldering
• the hexapod is first fixed in the working space of a pose detection device and commanded into its initialization pose.
• the pose T132 of the first coordinate system 1303 of a reference artifact placed on the hexapod is first determined.
• the pose 1304 of the reference coordinate system of the hexapod in relation to the auxiliary coordinate system of the pose detection device is therefore also known as the coordinate transformation T134.
• T133 stands for the predetermined first transformation rule and describes the coordinate transformation between the first coordinate system of the calibration artifact and the reference coordinate system of the hexapod
• Sample 1305 is a cuboid structure that is glued to the platform in the example.
• the pose detection device determining the coordinate system 1302 based on pose markings of the workpiece. This gives the transformation T131.
• Fig. 14 shows a parallel robot, 1404 designates the chassis, 1405 the gondola.
• the gondola has a grooved part, the grooves are in 1401,1402 and 1403 shown.
• the grooves are realized by two parallel embedded cylinders 1401 each.
• FIG. 15 shows the robot from FIG. 14, a ball part 1501 is placed on the gondola here. The view of the balls is obscured.
• Fig. 16 shows the underside of the ball part 1506.
• the balls 1601, 1602 and 1603 of the ball part can be seen, as well as a holding magnet 1604.
• Figure 17 shows a reference artifact where the pose marker consists of 6 touch points.
• 1708 denotes the primary plane, consisting of the three points 1704,1705 and 1706, the secondary plane is shown with 1707 with the associated points 1702 and 1703, the tartiary plane is marked with 1709 and bears the point 1701.
• the pose marking shown can clearly be associated with a cuboid Pose markers are created so that two coordinate systems can be related to one another by coordinate transformations.
• coordinate systems can be related to one another as desired by means of a coordinate transformation in the manner of a modular system.

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• Health & Medical Sciences (AREA)
• General Health & Medical Sciences (AREA)
• Orthopedic Medicine & Surgery (AREA)
• Manipulator (AREA)
• Length Measuring Devices With Unspecified Measuring Means (AREA)
• Transmission Devices (AREA)

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• 2020
  • 2020-09-16 DE DE102020124136.4A patent/DE102020124136B4/de active Active
• 2021
  • 2021-08-09 US US18/025,785 patent/US20230347526A1/en active Pending
  • 2021-08-09 EP EP21755987.1A patent/EP4214027A1/de active Pending
  • 2021-08-09 CN CN202180075857.8A patent/CN116457158A/zh active Pending
  • 2021-08-09 WO PCT/EP2021/072185 patent/WO2022058092A1/de active Application Filing
  • 2021-08-09 JP JP2023516812A patent/JP2023541642A/ja active Pending
  • 2021-08-09 KR KR1020237012233A patent/KR20230066086A/ko unknown

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