WO2011036033A1

WO2011036033A1 - Method and device for determining the orientation and position of an object

Info

Publication number: WO2011036033A1
Application number: PCT/EP2010/062636
Authority: WO
Inventors: Frank Hoeller; Marc Tremont; Oliver Schmidt; Marc Wagener; Christian Koos
Original assignee: Carl Zeiss Ag; Carl Zeiss Industrielle Messtechnik Gmbh
Priority date: 2009-09-23
Filing date: 2010-08-30
Publication date: 2011-03-31
Also published as: DE102009042702A1

Abstract

The invention relates to a method and device wherein a position at a segment (31) of a multi-axis kinematic linkage (2) is determined by an optical measurement, and the orientation of the segment (31) is obtained on the basis of control data of the multi-axis kinematic linkage (2). For other embodiment examples, the position and orientation of other objects can be determined and/or other data can be used as control data for determining the orientation.

Description

Methods and devices for determining the orientation and position of an object

The present invention relates to methods and apparatus for determining the orientation and position of an object, such as a point on a multi-axis kinematics, i. a point of a multi-axis kinematics or a point of an object attached to the multi-axis kinematics.

A multi-axis kinematics is understood to mean a device in which movements can be realized by a plurality of axes coupled to one another. Examples of such multi-axis kinematics are robot arms, wherein at the ends of such robot arms or at other points of the robot arm encoders, tools and the like may be attached.

For measuring objects with such encoders or for processing objects with such tools, it is necessary, depending on the encoder or tool, the position of the point of the multi-axis kinematics on which the encoder or the tool is mounted, and the orientation of the multi-axis kinematics This point, which then influences the orientation of the encoder or tool, to know exactly.

A particular example of such multi-axis kinematics devices are industrial coordinate measuring machines in which a tactile or optical sensor is mounted on the end of a robotic arm to measure a surface of an object. In order to be able to draw conclusions about the coordinates of the point being measured from the signal from the tactile or optical sensor, it is necessary to know the position and orientation of the sensor, which in turn depends on the position and orientation of a point of the robot arm to which the sensor is attached. depends on knowing. Basically, a determination of position and orientation based on multi-axis kinematics control data is possible. At typical angular resolutions in the range of 0.00005 degrees to 0.0002 degrees, in a typical multiple 6-axis rachskinematik an accuracy of determination of position of about +/- 0.025 mm. This is too imprecise for some applications, such as the coordinate measuring machines mentioned above. Therefore, methods and devices have been developed in which the position of, for example, an end point of a robot arm can be determined with high accuracy.

The realization of devices and methods in which positions in spaces of a few meters in length is determined with an accuracy in the micrometer range, thereby posing a technical challenge. This is especially true when positions are to be determined at a high rate and short signal processing time to a To enable position determination in real time, and a Jus- days of components of the measuring device should be as simple vornehmbar.

Laser trackers, which allow the determination of the three spatial coordinates of an object, combine a laser path length measuring device with a high-precision, double-cardanically mounted deflection mirror. From the measured distance and the two deflection angles of the deflection mirror, the object position can be determined. However, such laser trackers require precise control of the deflection mirror and accurate knowledge of the respective deflection angle of the deflection mirror. The corresponding Akto k represents a significant cost factor.

In geometrically optical methods, for example, a light source fixed to the object is observed with at least two cameras, and from this the object position is determined by means of triangulation. However, these methods often become inaccurate when the distance from camera to object varies greatly.

DE 101 18 392 A1 discloses a system and a method for determining a position of two objects relative to one another. The method uses the coherence properties of laser radiation for distance detection, in which several light beams are coherently superimposed.

Laser displacement gauges allow the determination of a distance of an object. In K. Minoshima and H. Matsumoto, "High-accuracy measurement of 240-meter distance in an optical tunnel by use of a compact femtosecond laser", Applied Optics, Vol. 39, No. 30, pp. 5512-5517 (2000 ), a distance measurement is used described by frequency combs. Although the measurement can be done with high accuracy, but limited to one dimension.

The above-mentioned methods merely provide one position of a multi-axis kinematics point, but provide no information about its orientation.

A device is known from DE 10 2004 021 892 A1, in which, to determine a position and an orientation, successively 6 different retro-reflectors are adapted by means of a so-called laser tracker. However, such a system is relatively expensive metrology.

It is therefore an object to provide methods and apparatuses wherein position and orientation of a multi-axis kinematics point can be easily determined with high accuracy.

This object is achieved by a method according to claim 1 and an apparatus according to claim 11. The dependent claims define further embodiments of methods and devices according to the invention.

According to the invention, a method is provided, comprising:

Determining a position of an object by an optical measurement,

and

Determining an orientation based on data obtained from a source different from the optical measurement.

By combining an optical measurement of the position with the orientation obtained from the data of the source, a high accuracy can be achieved with simultaneously reduced measuring effort.

The optical measurement can be in particular an optical length measurement. The source can then differ in particular from an optical length measurement.

In one embodiment, the object is a multi-axis kinematics section or an object attached to a multi-axis kinematics section. In the- In this case, for example, the source may be multi-axis kinematics control, and the data may be multi-axis kinematics control data.

The control data can be, for example, data from a multi-axis kinematics control program or data obtained from multi-axis kinematics.

The object may correspond to a multi-axis kinematics point, and at the point a transducer or tool may be mounted. In this case, the method may further enable determining an end position of the encoder or tool based on the orientation at the point and the position of the point.

In another embodiment, in the optical measurement via one or more movable mirrors, light, for example laser light, is directed into a desired spatial area and light reflected from the desired spatial area is measured in order to obtain a distance for determining the position. For example, starting from a section of multi-axis kinematics, the light can be directed to fixed retroreflectors and the light backscattered by the retroreflectors can be measured. In other embodiments, light from stationary measuring devices may be directed to a retroreflector mounted on a multi-axis kinematics or other object.

In such embodiments, the one or more movable mirrors may serve as a source, and the data may describe positions of the mirrors from which, in turn, the orientation may be obtained.

In this case, a deviation of the reflected light beam from a desired value can be used to correct the angular data thus obtained, wherein for determining the deviation, for example, a quadrant diode can be used.

In still other embodiments, the orientation may be obtained based on an image analysis of an image taken by a source camera, such as an image that captures stationary patterns from a moving object, such as a multi-axis kinematics section. In other embodiments, other types of sensors, such as gravitational sensors, inertial sensors, and / or magnetic field sensors may be used as the source for determining the orientation.

Further, partially optional or optional features and properties will become apparent from the following description of exemplary embodiments of the present invention with reference to the accompanying drawings. 1 shows an embodiment of a device according to the invention,

2 shows a further embodiment of a device according to the invention,

3 shows an embodiment of a measuring device according to the invention,

4 shows an embodiment of a measuring device according to the invention,

5 shows a further embodiment of a measuring device according to the invention,

6 shows an embodiment of a measuring device according to the invention,

7 is a flowchart illustrating an embodiment of a method according to the invention,

8 shows a further embodiment of a measuring device according to the invention, and

FIGS. 9a and 9b are schematic diagrams for illustrating the mode of operation of the embodiment of FIG. 8.

In the embodiment shown in Fig. 1 is used as an application robot arm 2, which is an example of a multi-axis kinematics. As explained in more detail below, a retroreflector 25 is mounted on a last member 31 of the robot arm 2, the position of which is optically determined. Furthermore, a transducer 29 is attached to the last member 31 of the robot arm, For example, an optical or a tactile encoder, such as a stylus, with which a surface 30 is measured.

A device 1 serves to optically determine the position of the retroreflector 25. It should be noted that the illustrated device 1 is to be understood as an example only, and in other embodiments, other devices, such as conventional laser trackers, may be used to determine the position of a point of the robot arm 2, for example the point at which the retractive reflector 25 and the dispenser 29 are mounted, in an optical way.

The device 1 comprises a light source 3 which generates a sequence of short light pulses at a repetition rate, a light-deflecting device formed by a plurality of optical elements 4-9, a pair of reference-signal detectors 11, 12 having a first reference-signal detector 1 and a second one Reference signal detector 12, a detector arrangement with a plurality of optical detectors 13, 14 and an evaluation circuit 15. The light-deflecting device receives the sequence of light pulses and directs the sequence of light pulses to the pair of reference signal detectors 1 1, 12 and into an area generally designated 28 in which the position of the reflector 25 attached to the robot arm 2 is to be determined. For reasons of simplicity, the light guided by the light-directing device to the reference signal detectors 11, 12 and into the spatial region 28 will hereinafter also be referred to as the sequence of light pulses, it being understood that in each case only a portion of the light pulse intensity generated by the light source 2 the reference signal detectors 1 1, 12 or in the space area 28 is directed. The sequence of light pulses is reflected in the spatial area by the reflector 25 arranged on the robot arm 2. The reflected sequence of light pulses is detected by the detectors 13, 14. The evaluation circuit 15 determines from the signals from the reference signal detectors 1 1, 12, which are received at a reference signal input 16, and from the signals from the detectors 13, 14, a Phaseniage of signal components of the detected light at the detectors 13, 14 in a light Relationship to the duration of the light pulses in the space region 28 and thus the distance of the reflector 25 from different elements of the light-guiding device is. In this way, the position of the reflector 25 can be determined. The determination of the phase position by the evaluation circuit 15 is based in the illustrated embodiment on signal components of the detectors 13, 14. detected light signals that have a frequency which is a multiple of the repetition rate.

The detectors 13, 14 and reference signal detectors 1 1, 12 are designed for example as photodetectors and detect the incident light intensity.

While in FIG. 1, for the sake of clarity, only two radiation fans 5, 7, from which light is directed into the spatial region 28, and two detectors 13, 14 associated therewith, light can also project from more than two different positions be directed into the space area in which the position of the object is to be determined. If all three spatial coordinates of the retro-reflector 25 are to be determined, the sequence of light pulses can be directed from at least one further irradiation position into the spatial region 28, which is not arranged on a straight line passing through the beam passing points at the beam dividers 5 and 7 is defined.

The operation of the various components of the device 1 will be explained in more detail below. The light source 3 generates an optical signal which is modulated with a periodic function and which has a fundamental frequency f0 and distinct portions of harmonics of the fundamental frequency f0, i. has distinct frequency components with frequencies that are multiples of f0. Such a signal is generated, for example, by a short pulse laser which produces a train of light pulses at a well-defined time interval T0 = 1 / f0, i. with a repetition rate f0, wherein the duration of each pulse is short in comparison to the time interval TO between successive pulses.

The duration of each light pulse can be very small compared to the time interval TO between successive light pulses, for example of the order of 1 -1 Cf ⁵ . In the device 3, the repetition rate f0 and the duration of each pulse may be suitably dependent on a desired measurement accuracy in the position determination, an initial uncertainty about the position of the object, and the signal component of the light signal detected at the detectors 13, 14, for the one phase position should be determined, or chosen depending on other factors. If the nth harmonic of f0 is used to determine the phase difference, the duration of each light pulse and the time interval are used. stand TO between successive Lichtpuisen chosen so that the output from the light source 3 sequence of light signals still has a sufficient spectral weight at the frequency n fO. The light pulses can form a series of rectangular pulses. Other suitable pulse shapes may also be chosen, for example the square of a hyperbolic secant or a Gaussian function.

A corresponding sequence of light pulses can be generated by different lasers, which are set up for the generation of short light pulses. In particular, optical frequency synthesizers can be used. For example, an electrically pumped diode laser, e.g. a Q-switched laser, a gain-switched laser, an active or passive mode-locked laser or a hybrid mode-locked laser, or a vertical-cavity surface-emitting vertical-cavity emitting laser (VCSEL) may be used as the light source 3 , Also, an optically pumped laser, such as a passive mode-locked external vertical cavity (VECSEL) surface-emitting laser or a photonic-crystal-fiber laser may be used as the light source 3. Exemplary pulse durations of the light source 3 are in a range of 100 fs and 100 ps. Exemplary repetition rates range from 50 MHz to 50 GHz. Exemplary average powers are in a range of 1 mW to 10 W. Exemplary values for the pulse jitter are between 10 fs and 1 ps effective value (root mean square).

As shown in FIG. 1, the sequence of light pulses output from the light source 3 is directed by the light directing means to the reference signal detectors 11, 12 and into the space portion 28. The light-directing device comprises in the device 1 a plurality of beam splitters 4, 5 and 7, a mirror 6 and beam expander 8, 9, which are associated with the beam splitters 5 and 7, respectively. The beam splitter 4 receives the sequence of light pulses from the light source 3. A sub-beam 20 of the sequence of light pulses is directed by the beam splitter 4 as a reference signal to the reference signal detectors 11, 12. If necessary, an optical element for beam splitting, in particular a beam splitter, can also be arranged downstream of the beam splitter 4 in order to ensure that the sub-beam strikes both the reference signal detector 1 1 and the reference signal detector 12. Another sub-beam of the sequence of light pulses is transmitted by the beam splitter 4 and impinges on the beam splitter 5. The beam 5 directs a partial beam 21 of the sequence of light pulses over the beam 8 into the spatial region 28, wherein the beam expander 8 expands the partial beam 21 into a light cone 22. Another partial beam is transmitted by the beam splitter 5 and directed to the beam splitter 7 via the mirror 6. The beam splitter 7 deflects a partial beam 26 of the sequence of light pulses via the beam expander 9 into the spatial region 28, wherein the beam expander 9 expands the partial beam 26 into a cone of light 27. A portion of the light beam received by the mirror 6, which is transmitted by the beam splitter 7, can be directed in the direction of the spatial region 28 via a further beam splitter (not shown in FIG. 1). The space area 28 in which the position of the object can be determined corresponds to the overlapping area of the different light cones 22, 27. If the sequence of light pulses is directed from more than three positions in the direction of the area in which the object position is to be determined, is the space area in which a determination of the object position is possible, the union of all overlapping areas of at least three different light cones, which are radiated from at least three starting points that are not on a straight line.

The sequence of light pulses directed via the beam divider 5 and the light expander 8 in the light cone 22 into the spatial region 28 strikes the retroreflector 25 and is reflected by it back in the direction of the light expander 8. The light reflected back from the retroreflector 25 in the direction of the light expander 8 forms a first light signal 23, which is directed onto the detector 13 via the light expander 8 and the beam splitter 5. The sequence of light pulses directed via the beam splitter 7 and the light expander 9 in the light cone 26 into the spatial region 28 strikes the retroreflector 25 and is reflected by it back in the direction of the light expander 9. The light reflected by the retroreflector 25 back in the direction of the light expander 9 forms a second light signal 24, which is directed onto the detector 14 via the light expander 9 and the beam splitter 7. If the retroreflector 25 is arranged in the light cone of further combinations of beam splitter, light expander and detector, correspondingly further light signals are reflected by the retroreflector 25, which light signals are directed to the corresponding detector via the light expander and beam splitter.

The light guiding device which directs the sequence of light pulses into the spatial region 28 and the detectors 13, 14 of the detector arrangement are arranged such that the light signal 23 reflected in the direction of the detector 13 is reflected in a different direction than the light signal 24 reflected in the direction of the detector 14. The retroreflector 25 provided on the robot arm 2 can be designed, for example, as a Corner Cube Reflector (CCR), as a triple prism or as a cat-eye reflector (cat-eye) or as a ball lens (ball lens). The Eckwürfeireflektor and the triple prism, the light is reflected back parallel to the incident beam directions. A divergent beam remains divergent. In the cat-eye reflector or in the ball lens, these retroreflectors can be optimized for a certain distance in such a way that the reflected beam is essentially reflected back into itself, as a result of which a higher signal level is present at the detector.

Instead of a retrorefiector, it is also possible to use a small scattering element which differs significantly in its scattering behavior from its surroundings in order to scatter light from the relevant object point to the detectors. In order for the detector to have a usable signal that is distinguishable from the noise of the scattering environment, the small element should scatter light strongly.

The light signals 23 and 24 are detected by the detectors 13 and 14, respectively. The detectors 13, 14 and reference signal detectors 1 1, 12 are configured as a photoreceiver. The detectors 13 and 14 detect the light power of the incident on them sequence of light pulses, which propagates via the detector 13 and 14 respectively associated beam splitter 5 and 7 to the retroreflector 25 and from this back to the detector 13 and 14 respectively. The different optical path length of a light pulse, on the one hand to one of the reference signal detectors 1 1, 12 and on the other hand to reach after a reflection at the retroreflector 25 to one of the detectors 13 and 14, leads to a time shift τι or τ ₂ between the Arrival of one and the same light pulse on one of the detectors 3 and 14 and on the reference signal detectors 1 1, 12, which is equal to the difference in optical path length of the light paths divided by the speed of light c. Since typically only a small proportion of the light directed into the space region 28 is reflected by the retroreflector 25, the signal at the detectors 13, 14 is attenuated with respect to the reference signal at the reference signal detectors 11, 12.

The path length difference includes on the one hand distances that depend on the geometry of the device, in particular the distances between the beam splitters 5, 7 and the beam splitter 4 and the distances between the beam splitters 4, 5, 7 and the detectors 13, 14 and the reference signal detectors 1 1, 12, each along the beam and, on the other hand, a component which, for the light signal detected at the detector 13, is the optical path length between the beam splitter 5 or the virtual starting point of the light cone 22, and the retroreflector 25 and for the signal detected at the detector 14 Path length between see the beam splitter 7 or the virtual starting point of the light cone 27, and the retroreflector 25 depends. Since with known geometry of the device 1 of the device geometry dependent proportion of the path length difference is known, by measuring the time shift τι between the light signal 23 at the detector 13 and the reference signal 20 to the reference signal detectors 11, 12, the distance traveled by the light pulse optical path length between the Beam splitter 5 and the retroreflector 25 and thus the distance of the retroreflector 25 from the beam passing point of the beam splitter 5 and from the virtual starting point of the light cone 22 are determined. Similarly, by measuring the time shift τ ₂ between the light signal 24 at the detector 14 and the reference signal 20 at the reference signal detectors 1 1, 12 the distance traveled by the light optical Wegiänge between the beam splitter 7 and the retroreflector 25 and thus the distance of the retroreflector 25 of the Beam penetration point of the beam splitter 7 and be determined by the virtual starting point of the light cone 27. The detectors 13 and 14 and the reference signal detectors 11, 12 are coupled to the evaluation circuit 15, which determines a phase difference between the light signals 23, 24 and the reference signal 20. In one embodiment, the evaluation circuit 15 of the device 1 determines the phase difference between the light signal 23, 24 and the reference signal 20 for a signal component whose frequency is substantially a multiple of the repetition rate.

The phase difference is directly related to the above-mentioned time shift, and based on the phase difference, the evaluation circuit 15 can then determine the position of the retroreflector 25.

The device 1 thus determines the position of the retroreflector 25, ie a point of the last member of the robot arm 2, on which the encoder 29 is mounted, in a coordinate system S of the device 1. To an end point of the element 29, ie the encoder or tool to receive, or in other words, to determine an interaction point of the encoder 29 with the surface 30, it is necessary, in addition to the position of the last In addition, member 31 is to know the orientation of the last member 31 of the robot arm 2 to which the sensor 29 and also the retroreflector 25 are fastened. In one embodiment, the orientation of this member and thus the orientation of the encoder 29 is obtained from control data of the robot arm 2. For this purpose, the evaluation unit 15 receives in the illustrated embodiment, the corresponding control data of the robot arm 2. This control data, for example, from a software-based control of the robot 2 or coupled to the axes of the robot arm 2 angle encoders, ie angle measuring devices originate.

The orientation of the last member 31 of the robot arm 2 can be expressed, for example, with three angles φ, θ,,, where Θ the azimuth angle, ie the angle between the positive x-axis of the coordinate system S and the projection of the last member of the robot arm 2 in the x, y-plane of the coordinate system S, while the angle φ may be the so-called polar angle, ie the angle between the positive z-axis of the coordinate system S and the last member of the robot arm, φ has a value in such a system between 0 and π (0 degrees to 180 degrees), and Θ has a value between 0 and 2π (0 degrees to 360 degrees), both angles are measured counterclockwise, ψ denotes a rotation about the longitudinal axis of the last one 2 of the robot arm 2. As shown in FIG. 1, the retroreflector 25 is attached to the end of the last link 31, and I is the length of the encoder 29, and is an interaction region of the encoder 29 with the surface 30 symmetrical with respect to a central axis of the last member 31, eg a point lying on the central axis, so that a change of the angle ψ does not change the interaction region, coordinates x _W w, yww and zww of a center of the interaction region in the result Coordinate S to

CpCOS Θ

yww = y _mess + l-sin cpsin Θ

wherein Xmess, Ymess and z _me ss are the coordinates of the retroreflector 25 determined by the apparatus 1, ie the end point of the last member 31.

In such cases, in which the interaction point is symmetrical to the axis of the last member 31, the angle φ must therefore not be used. If another element, for example a tool with an elongated interaction region, is used instead of the transducer 29 with a substantially punctiform interaction region with the surface 30, the position of such an interaction region can be determined with additional use of the angle ψ.

In a typical robotic system and apparatus 1, with the apparatus of the invention of FIG. 1, with a length I of the encoder 29 of 50 mm, positional determinations of the interaction range with an accuracy on the order of 2-5 μm, i. about an order of magnitude better than the accuracy based only on control data of the robot arm, as described in the introduction. However, these values are to be understood only as an example, and depend on the robot arm 2 used in actual use and the device 1 actually used.

By making the interaction region, e.g. Interaction point, the encoder 29 is determined with the surface 30, the surface 30 in the coordinate system S of the device 1 can be measured accurately and the data thus obtained, for example, CAD data, or more generally a specification compared. For such a measurement, the surface 30 is fixedly clamped in the coordinate system S, for example by means of a tenter.

It should be noted that in optical encoders, the length I is composed of the length of the encoder itself and the distance to the optical measured distance to the surface 30. In tactual encoders, the length I is also from a position of a respective measuring pin or other sensor, where Position is determined by the encoder depends.

It should also be noted that in principle the encoder 29 itself may comprise one or more joints. In this case, angles of these joints as well as dimensions of the encoder are taken into account in the determination of the point of interaction when the retroreflector 25 is mounted on the last link or generally on the multi-axis kinematics as shown in FIG. On the other hand, in such a case, the retroreflector 25 can be attached to a corresponding end of the encoder, and in addition to the control data of the multi-axis kinematics and angular data of the encoder are then taken into account for determining the interaction position. As already mentioned, in other embodiments instead of the encoder 29 a tool may be attached to the last member 31 of the robot arm, for example a cutting tool, a drilling tool or a welding tool. By determining position and orientation according to the present invention, the interaction point or the interaction region of such a tool with a surface to be machined in the coordinate system S can be approached precisely and thus the corresponding processing of the surface S, for example, according to a desired value, as with a CAD system has been defined.

It should be noted that the retroreflector 25 in Fig. 1 instead of the last member 31 can be mounted directly on the encoder 29. In this case, control data of the robot arm 2 are also used to determine the orientation of the encoder 29. The same applies if a tool is used instead of the encoder.

In the embodiment of Fig. 1, as described, a retroreflector 25 is attached to the last member 31 of the multi-axis kinematics, illuminating the retroreflector from a plurality of fixed locations and measuring the reflected light. The illumination can also be directed by means of movable mirrors into a spatial region in which the retroreflector 25 is located, if the light cones 22 and 27 have an expansion which, without pivoting the light cones, is insufficient to illuminate the entire area of interest.

In other embodiments, the reverse arrangement may also be used, that is, light may be directed from a last member of a multi-axis kinematics or other object to be measured to a plurality of fixed retroreflectors, and the reflected light may be measured, for example, by the same measurement principles Measure distances as described above to determine the position. A corresponding embodiment will now be explained with reference to Figures 2-5. In Fig. 2, a robot arm 40, which substantially corresponds to the robot arm 2 of Fig. 1, is shown. The robot arm 40 has several axes in order to che he can be rotated or pivoted, and thus also represents a multi-axis kinematics.

In turn, a measuring element or a tool can be attached to a last link 41. The position and orientation of the last member 41 are to be determined, that is, the last member 41 represents an object whose position and orientation is to be determined.

To determine the position, a measuring device 42 is mounted on the last link 41, which measures by optical measurement distances to retroreflectors 43, 44 and 45 as indicated by dashed lines. In particular, the measuring device 42 can transmit light beams to the retroreflectors 43, 44, 45 and then detect light reflected back from the retroreflectors 43, 44 and 45. Instead of the retroreflectors, as already explained with reference to FIG. 1, other reflecting or scattering elements may also be provided. By determining a distance to the three retroreflectors 43, 44, 45, a determination of the position in three spatial directions is possible.

The evaluation of the detected light and the determination of the position can be carried out by an evaluation unit 46. In the embodiment of FIG. 2, the position of the measuring device 42 can be determined on the basis of the optical length measurements to the retroreflectors 43, 44, 45, while the orientation of the measuring device 42 and thus the portion 41 of control data of the robot arm 40 is obtained.

The measuring device 42 can measure the retroreflectors 43, 44, 45 in succession, that is to say sequentially. In other embodiments, the measuring device 42 comprises, for example, three separate measuring devices, each measuring device measuring one of the retroreflectors. An example of this is shown schematically in FIG. 3.

In the example of FIG. 3, three measuring devices 51, 52, 53, which are symbolized by light cones, are arranged in a triangular shape 50. It should be noted that, for this purpose, the measuring devices 51, 52 and 53 can be arranged on a triangular plate, but can also be arranged on any other carrier. The light cones of the measuring devices 51, 52 and 53 can be pivotable about a respective retroreflector, for example one of the retroreflectors 43, 44, 45, to be irradiated. This configuration is characterized in particular by the fact that three lengths can be measured simultaneously. This is particularly advantageous if position and orientation during movement is to be measured. In such a configuration, three lengths, which are the distance of 3 pairs of different measuring devices, for example, the measuring devices 51,

52 and 53, to 3 pairs of different retroreflectors e.g. the retroreflectors 43, 44 and 45 measure the position to be calculated accurately only when the orientation of the coordinate system defined by the IVI devices is known to the coordinate system of the retroreflectors.

In one embodiment, the measuring devices 51, 52 and

53 emitted light beams may be marked in various ways to allow a separation of the reflected light. For example, various modulations, for example, different pulse rates, may be used, or different wavelengths may be used in conjunction with corresponding filters.

In a further embodiment, the emitted light beams can be emitted collimated or largely collimated, so that it is ensured that the light beams only illuminate exactly one retroreflector,

An exemplary embodiment of an implementation of a measuring device such as one of the measuring devices 51, 52, 53 is shown schematically in FIG. 4. In the embodiment of FIG. 4, a light source 60, for example a laser, generates a light beam 61. The light beam 61 is directed to a mirror 63 via a light guide 62, for example a glass fiber. By using the light guide 62, the light source 60 may be disposed away from the mirror 63. For example, in the embodiment of FIG. 2, the mirror 63 may be disposed in the measuring device 42, while the light source 60 may even be disposed outside the robot arm 40. In particular, the light source 60 may be a short pulse laser.

If several measuring devices are present, as in the exemplary embodiment of FIG. 3 or FIG. 5, separate light sources 60 can be used. However, it is also possible to use a common light source 60, with a light beam generated by the light source 60, for example a laser beam, being split by beam splitters or other means. optical elements can be split to provide light beams for three devices.

The mirror 63 is in the embodiment of Fig. 4, a movable mirror, which is movable via a device 64. For example, the mirror 63 may be an electro-electromechanical system, that is, an EMS mirror. In such mirrors, mechanical elements are integrated together with an actuator, for example on a silicon substrate. In the embodiment of FIG. 4, the mirror 63 may be tiltable, for example, in two mutually perpendicular spatial directions. Thus, a reflected beam 65 within the limits shown in FIG. 4 by dashed lines 68 may be adjusted, for example, to irradiate a desired retroreflector.

In the case of E S mirrors, the adjustment range of the reflected beam 65 is typically in the range of plus minus 10 degrees.

To enlarge this adjustment range, a wide-angle optical system 66 may be provided, which is shown in FIG. 4 as a simple lens, but may also comprise a plurality of lenses or other optical elements. As a result, an adjustment range of the beam 67 which has passed through the optics 66 can be increased, as indicated by dashed lines 69, in order to be able to detect a larger angular range. Parts of the wide-angle optics 66 may also be arranged in front of the MEMS mirror so that the EMS mirror becomes part of the objective.

It should be noted that the representations of FIG. 4 are to be regarded as schematic and, for example, additional lenses, for example for collimating the laser beam 61 at the exit from the light guide 62, may be provided.

As summarized in FIG. 5, three retroreflectors 74, 75, 76 can be irradiated in this manner by three measuring devices 71, 72, 73 arranged in a triangular shape 70, which can be configured in each case as shown in FIG. 4, for example 77, 78, 79 measured by measuring the respective reflected beam. In an embodiment as explained with reference to FIGS. 4 and 5, the three lengths 77, 78, 79 for determining the position of the measuring device and thus of the object to which the measuring device is attached, for example the section 41 of FIG. 2, may be determined become. Instead of determining the orientation from control data, the orientation can also be obtained from the position of the mirrors, for example the mirror 63 from FIG. 4, in such exemplary embodiments. By the angular position of the mirrors 63 in the measuring devices 71, 72, 73 in FIG. 5, for example, an angular position of the triangle 70 relative to the respective reflector 74, 75 and 76 can be derived, whereby the orientation of the triangle 70 can be obtained. If in each case the position of the respective mirror is detected in two mutually perpendicular axes, an emerging system of equations is even overdetermined, since basically three angles are sufficient to determine the orientation. The mirror angle can either be taken from a mirror control or be measured directly by a coupled to the mirror measuring device, for example by detecting a reflected beam on the mirror.

In embodiments where a light beam such as the laser light beam 61 of FIG. 4 is widened to produce a cone of light, the center of the light cone need not exactly hit the respective retroreflector to measure, rather, there is a tolerance within the angular range of the light cone. A deviation of the measuring beam from the center of the reflector can also result, for example, from the fact that the mirror is controlled digitally and thus can occupy only a limited number of positions. This can lead to a corresponding inaccuracy of the determination of the orientation based on the angular positions of the mirror. In some embodiments, mechanisms may be provided to correct for such a deviation. Such an embodiment will now be explained in more detail with reference to Figures 6 and 7.

FIG. 6 schematically shows a measuring device similar to the measuring device of FIG. 4. A light beam 85, for example a laser beam, is conducted via an optical waveguide, for example a glass fiber 80, to a collimator 81 at the exit of the optical fiber 80. The beam collimated by the collimator 81 passes through a beam splitter 82 to a movable mirror 83 which directs the beam to a retroreflector 84. Light reflected by the retroreflector 84 is in turn directed via the mirror 83 to the beam splitter 82 and from there to a detector 86. The detector 86 may in particular be a quadrant detector, for example a quadrant diode. By measuring the deviation of the point of incidence of the light beam on the detector 86 from a center point, a deviation of the measuring beam from the reflector center of the reflector 84 can then be detected and this deviation can be used to correct the orientation calculation on the basis of the angle of the mirror 83. It should be noted that the embodiments of Figures 4 and 6 can be combined. Thus, in the exemplary embodiment of FIG. 6, a wide-angle optical system such as the wide-angle optical system 66 from FIG. 4 may be provided, or in the exemplary embodiment of FIG. 4, a radiation interrupter and a detector such as beam splitter 82 and detector 86 may be provided.

Furthermore, it should be noted that a further detector and a further beam splitter can be provided for detecting the beam backscattered by the respective reflector for measuring the distance, as is also shown in FIG. 1 (beam splitter 5 and detector 13, beam splitter 7 and detector 14) ).

FIG. 7 shows a flow diagram of a method according to the invention, with which in embodiments such as the exemplary embodiments of FIGS. 4 and 3, light beams for position determination are directed through a movable mirror to a retroreflector or other reflector and the backscattered light is evaluated to determine a distance. In step 90, three distances are measured. This can be done in parallel with an arrangement with three measuring devices as shown in FIGS. 3 and 5, but can also proceed sequentially with a single measuring device, which, for example, by changing a mirror position of a movable mirror successively three different reflectors targeted.

In parallel, in step 92, the mirror angles in the measurement of the three distances from step 90 are detected. In step 93, a deviation of a used measuring beam from a reflector center, for example by means of a quadrant detector such as the detector 86 from FIG. 6, is optionally also detected. In step 94, the angle measurement performed in step 92 is corrected based on the deviation detected in step 93. In step 95, an orientation of the measuring device used and thus of the object to which the measuring device is attached is then determined on the basis of the corrected angle measurements.

In step 91, a position is determined by trilateration based on the three distances and optionally the orientation from step 95. In a configuration in which the distance to three retro-reflectors is measured with a single measuring device on the object or from e.g. If the distance to a reflector on the object is measured by three fixed measuring devices, the position in step 91 can be determined directly from the three distances measured in step 90 without the need for the orientation information. In a configuration with three measuring devices as in FIG. 3, which simultaneously measure the distance to three retro-reflectors, the orientation is also used to determine the position of the measuring device and thus of the object based on the length measurements, as indicated by a dashed arrow is indicated in Fig. 7.

In step 96 position and orientation are then output. Another possibility for determining an orientation of a measuring device or an object to which the measuring device is attached is shown in FIGS. 8 and 9.

FIG. 8 shows a measuring device which has three measuring devices 101, 102, 103, which are arranged in the form of a triangle 100. The measuring devices 101, 102, 103 may be measuring devices as described with reference to FIGS. 3-6, which direct light to respective reflectors 104, 105, 106 by means of mirrors. In other embodiments, measuring devices 101, 102, 103 may also be provided without movable mirrors, in which a beam is, for example, expanded in such a way that it detects the respective reflector to be measured in a total desired movement space of the measuring device. In still other embodiments, a single measuring device may be provided which measures, for example, successively three different retroreflectors ren. In this way, three lengths 107, 108 and 109 are determined, from which the position can be determined, as in the preceding embodiments. In order to determine the orientation, a camera 110 is provided in the embodiment of FIG. 8, for example a digital camera with an image sensor such as a CCD sensor or a CMOS sensor. In addition, in addition to the fixed reflectors 104, 105, 106 fixed patterns 1 1, 1 2 are provided, which consist in the illustrated example of four luminous points, such as light emitting diodes. However, other patterns with, for example, more or less dots, other geometric shapes and / or non-luminous patterns are possible.

The patterns 111, 112 are recorded to determine the orientation of the measuring device with the camera 1 10. An evaluation unit such as the evaluation unit 46 of FIG. 2 performs an image analysis to detect the patterns. For example, it can be deduced from a distortion of the pattern as a function of the viewing angle on the orientation of the measuring device. For example, the patterns 1 1 1, 112 may appear as viewed in a grader manner as shown in FIG. 9a, while they may appear obliquely as shown in FIG. 9b. Thus, such a camera is another possible source for obtaining data from which the position of the measuring device and thus of the object to which the measuring device is attached can be determined.

The above embodiments are not to be construed as limiting the scope of the invention. In particular, other sources for determining the orientation are possible. For example, a measuring device may be equipped with a gravitational sensor and / or inertial sensor to determine the orientation, or a magnetic field sensor such as a SQUID may be provided, which detects the orientation relative to a predetermined, for example homogeneous, magnetic field. Combinations of the different possibilities can also be used.

While in the illustrated embodiment a measuring device was attached to a robot arm, a corresponding measuring device can also be attached to another object, for example a manually movable device such as a measuring device. A robotic arm like FIGS. 1 and 2 can also be moved as a whole in space, for example, by mounting on a movable platform.

The length measurements described can be carried out, for example, based on interferometry as described, in particular heterodyne interferometry, based on tunable lasers and / or based on pulsed lasers.

As can be seen from the above, a variety of variations and modifications are possible. Accordingly, the invention is not limited to the above-described embodiments.

Claims

PAT EN TA NSPR O CHE

1 . Method, comprising:

Determining a position of an object based on an optical measurement, and

Determining an orientation of the object based on data obtained from a source different from the optical measurement.

2. The method of claim 1, wherein the object is a section (31, 41) of a multi-axis kinematics (2; 40).

3. The method of claim 2, wherein the data comprises multi-axis kinematics control data (2) and the source comprises multi-axis kinematics control (2).

The method of claim 2 or 3, wherein determining the orientation from control data comprises evaluating data from multi-axis kinematics encoders

(2).

A method according to any one of claims 2-4, wherein the portion is an end portion (31), and wherein determining a position at an end portion (31) of the multi-axis kinematics (2) comprises determining a position of an end of the end portion (31) ,

6. The method of claim 2, wherein determining the position comprises determining the position of a point of an element (29) attached to the end portion (31).

The method of any of claims 2-6, further comprising:

Determining an interaction region of an element (29) attached to the end section (31) with a surface (30) of a workpiece.

8. The method of claim 7, wherein the interaction region is substantially punctiform.

9. The method according to any one of claims 6-8, wherein the element is selected from the group consisting of a transducer (29) and a tool.

The method of claim 7 or 8, wherein the element comprises a transducer (29), the method further comprising:

Comparing the determined interaction region with a desired interaction region.

1 1. The method of claim 7 or 8, wherein the element comprises a tool, further comprising:

Moving the multi-axis kinematics (2) such that the interaction region corresponds to a predetermined interaction region, and

Edit the surface with the tool.

12. The method of claim 1, wherein determining the position comprises illuminating a retroreflector with at least one light beam, and detecting the at least one light beam reflected by the retroreflector.

13. The method of claim 12, wherein the retroreflector is a stationary retroreflector, and the light beam is directed from the object to the retroreflector.

14. The method of claim 13, wherein the at least one light beam comprises three light beams which are directed to three different retroreflectors.

15. The method of claim 13, wherein steering the at least one light beam comprises adjusting a movable mirror,

wherein the source comprises the movable mirror and the data comprises an angular position of the movable mirror.

16. The method of claim 15, further comprising determining a deviation of the light beam from a center of the retroreflector, and

Correct the data based on the deviation.

17. The method of claim 16, wherein determining the deviation is performed by a quadrant detector.

18. The method of claim 1, wherein the source comprises a camera, the data comprising image data of the camera.

The method of claim 18, wherein the camera is mounted on the object, wherein the image data includes fixed pattern photographs.

20. The method of claim 1, wherein the source comprises a gravitational sensor.

21. The method of any one of claims 1 to 20, wherein the source comprises an inertial sensor.

22. The method of claim 1, wherein the source comprises a magnetic field sensor.

23. The method of claim 1, wherein determining the position is based on the optical measurement and the orientation.

24. Apparatus comprising:

an optical measuring device (1) for carrying out at least one optical length measurement,

an evaluation unit (15; 46) which is configured, a position of an object (31; 41) based on the at least one optical length measurement and an orientation of the object (31; 41) based on data from a source (2; 40; 83; 63, 1 10), where the data is not optical length measurement data.

25. The apparatus of claim 24, further comprising a multi-axis kinematics (2;

40), the object being a multi-axis kinematics section (31; 41).

26. The apparatus of claim 25, further comprising an element (29) attached to the portion (31), the controller (15) further configured to determine an interaction point of the element (29) with a surface (30).

27. The apparatus of claim 26, wherein the element is selected from the group comprising a transducer (29) and a tool.

The apparatus of any one of claims 25-27, wherein the source comprises multi-axis kinematics control (2) and the data comprises multi-axis kinematics control data.

29. Device according to one of claims 24-28, wherein the measuring device for position determination () comprises a short pulse laser (3).

30. The device of claim 24, wherein the optical measuring device comprises a movable mirror for directing a light beam to a reflector, the source comprising the movable mirror, the data comprising an angular position of the movable mirror.

31. An apparatus according to claim 30, further comprising detecting means (82, 86) for determining a deviation of the light beam from a center of the reflector.

The apparatus of any of claims 24-31, wherein the source comprises a camera and the data comprises image data of the camera.

33. The device of claim 24, wherein the source comprises one or more sensors from the group comprising an inertial sensor, a gravitational sensor and a magnetic field sensor.

34. Device according to one of claims 24-33, wherein the device for carrying out the method according to one of claims 1-23 is configured.