WO2011036033A1 - Procédé et dispositifs de détermination de l'orientation et de la positon d'un objet - Google Patents

Procédé et dispositifs de détermination de l'orientation et de la positon d'un objet Download PDF

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Publication number
WO2011036033A1
WO2011036033A1 PCT/EP2010/062636 EP2010062636W WO2011036033A1 WO 2011036033 A1 WO2011036033 A1 WO 2011036033A1 EP 2010062636 W EP2010062636 W EP 2010062636W WO 2011036033 A1 WO2011036033 A1 WO 2011036033A1
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WIPO (PCT)
Prior art keywords
light
determining
data
retroreflector
orientation
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PCT/EP2010/062636
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German (de)
English (en)
Inventor
Frank Hoeller
Marc Tremont
Oliver Schmidt
Marc Wagener
Christian Koos
Original Assignee
Carl Zeiss Ag
Carl Zeiss Industrielle Messtechnik Gmbh
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Application filed by Carl Zeiss Ag, Carl Zeiss Industrielle Messtechnik Gmbh filed Critical Carl Zeiss Ag
Publication of WO2011036033A1 publication Critical patent/WO2011036033A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/002—Measuring arrangements characterised by the use of optical techniques for measuring two or more coordinates

Definitions

  • 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.
  • 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.
  • a tactile or optical sensor is mounted on the end of a robotic arm to measure a surface of an object.
  • 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.
  • a determination of position and orientation based on multi-axis kinematics control data is possible.
  • 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.
  • 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.
  • 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.
  • 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.
  • a so-called laser tracker is relatively expensive metrology.
  • a method comprising:
  • the optical measurement can be in particular an optical length measurement.
  • the source can then differ in particular from an optical length measurement.
  • the object is a multi-axis kinematics section or an object attached to a multi-axis kinematics section.
  • the source may be multi-axis kinematics control
  • 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.
  • 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.
  • light for example laser light
  • the 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.
  • the light can be directed to fixed retroreflectors and the light backscattered by the retroreflectors can be measured.
  • light from stationary measuring devices may be directed to a retroreflector mounted on a multi-axis kinematics or other object.
  • 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.
  • 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.
  • 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.
  • a source camera such as an image that captures stationary patterns from a moving object, such as a multi-axis kinematics section.
  • sensors such as gravitational sensors, inertial sensors, and / or magnetic field sensors may be used as the source for determining the orientation.
  • FIG 3 shows an embodiment of a measuring device according to the invention
  • FIG. 5 shows a further embodiment of a measuring device according to the invention
  • FIG. 6 shows an embodiment of a measuring device according to the invention
  • FIG. 7 is a flowchart illustrating an embodiment of a method according to the invention.
  • FIG. 8 shows a further embodiment of a measuring device according to the invention.
  • FIGS. 9a and 9b are schematic diagrams for illustrating the mode of operation of the embodiment of FIG. 8.
  • a retroreflector 25 is mounted on a last member 31 of the robot arm 2, the position of which is optically determined.
  • 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.
  • 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.
  • 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 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.
  • 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 .
  • 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.
  • optical frequency synthesizers can be used.
  • 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
  • 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.
  • VECSEL passive mode-locked external vertical cavity
  • 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).
  • 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.
  • 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).
  • CCR Corner Cube Reflector
  • the Eckchiefeireflektor and the triple prism the light is reflected back parallel to the incident beam directions.
  • a divergent beam remains divergent.
  • 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.
  • the small element 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 ⁇ or ⁇ 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.
  • 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.
  • 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.
  • 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 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.
  • 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.
  • the orientation of this member and thus the orientation of the encoder 29 is obtained from control data of the robot arm 2.
  • 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 ⁇ , ⁇ ,,, where ⁇ 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 ⁇ 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, ⁇ has a value in such a system between 0 and ⁇ (0 degrees to 180 degrees), and ⁇ has a value between 0 and 2 ⁇ (0 degrees to 360 degrees), both angles are measured counterclockwise, ⁇ denotes a rotation about the longitudinal axis of the last one 2 of the robot arm 2.
  • 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 ⁇ 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 ⁇
  • 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.
  • the angle ⁇ 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 ⁇ .
  • 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.
  • the surface 30 is fixedly clamped in the coordinate system S, for example by means of a tenter.
  • the length I is composed of the length of the encoder itself and the distance to the optical measured distance to the surface 30.
  • the length I is also from a position of a respective measuring pin or other sensor, where Position is determined by the encoder depends.
  • 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.
  • 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.
  • 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.
  • the retroreflector 25 in Fig. 1 instead of the last member 31 can be mounted directly on the encoder 29.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • retroreflectors instead of the retroreflectors, as already explained with reference to FIG. 1, other reflecting or scattering elements may also be provided.
  • the evaluation of the detected light and the determination of the position can be carried out by an evaluation unit 46.
  • 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.
  • 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.
  • three measuring devices 51, 52, 53 which are symbolized by light cones, are arranged in a triangular shape 50.
  • 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,
  • 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.
  • the measuring devices 51, 52 and 53 are identical to the measuring devices 51, 52 and 53.
  • 53 emitted light beams may be marked in various ways to allow a separation of the reflected light.
  • various modulations for example, different pulse rates, may be used, or different wavelengths may be used in conjunction with corresponding filters.
  • 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,
  • FIG. 4 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.
  • 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.
  • the light source 60 may be disposed away from the mirror 63.
  • 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.
  • the light source 60 may be a short pulse laser.
  • separate light sources 60 can be used.
  • 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.
  • 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.
  • the mirror 63 may be tiltable, for example, in two mutually perpendicular spatial directions.
  • 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.
  • the adjustment range of the reflected beam 65 is typically in the range of plus minus 10 degrees.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • the orientation can also be obtained from the position of the mirrors, for example the mirror 63 from FIG. 4, in such exemplary embodiments.
  • an angular position of the mirrors 63 in the measuring devices 71, 72, 73 in FIG. 5 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.
  • 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.
  • 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
  • An optical waveguide for example a glass 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • step 92 the mirror angles in the measurement of the three distances from step 90 are detected.
  • 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.
  • step 94 the angle measurement performed in step 92 is corrected based on the deviation detected in step 93.
  • 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.
  • a position is determined by trilateration based on the three distances and optionally the orientation from step 95.
  • the position in step 91 can be determined directly from the three distances measured in step 90 without the need for the orientation information.
  • 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.
  • 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.
  • 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.
  • a single measuring device may be provided which measures, for example, successively three different retroreflectors ren.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Length Measuring Devices By Optical Means (AREA)
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Abstract

L'invention concerne un procédé et des dispositifs permettant de déterminer, par une mesure optique, une position sur une section (31) d'une cinématique multiaxiale (2), l'orientation de la section (31) étant obtenue sur la base de données de commande de la cinématique multiaxiale (2). Pour d'autres exemples de réalisation, on peut déterminer la position et l'orientation d'autres objets et/ou utiliser d'autres données comme données de commande pour la détermination de l'orientation.
PCT/EP2010/062636 2009-09-23 2010-08-30 Procédé et dispositifs de détermination de l'orientation et de la positon d'un objet WO2011036033A1 (fr)

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DE102009042702A DE102009042702A1 (de) 2009-09-23 2009-09-23 Verfahren und Vorrichtung zur Bestimmung von Orientierung und Position eines Punktes einer Mehrachskinematik

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