DE102015118362A1 - DEVICE AND METHOD FOR DETERMINING A POINT CLOUD REPRESENTING A SURFACE OF A SPATIAL BODY - Google Patents

Abstract

Shown is a device (10) for determining a point cloud, which represents a surface of a spatial body (30). The apparatus (10) comprises a first measuring device (12) arranged to continuously determine a position and orientation of the spatial body (30) relative to the first measuring device (12) and a second measuring device (14) arranged to measure coordinates of a plurality of Points on the surface of the spatial body (30) relative to the second measuring device (14), wherein the coordinates of each point of the plurality of points is associated with an indication of a time of measurement of the coordinates. The apparatus further comprises computing means (32) arranged to correct the coordinates of the plurality of points for the influence of relative movement between the spatial body (30) and the second measuring device (12) based on continuously determining the position and orientation of the spatial Body (30) relative to the first measuring device (12) and a positional relationship between the first measuring device (12) and the second measuring device (14), wherein the corrected by the influence of the relative movement coordinates of the plurality of points determine the point cloud.

Description

TERRITORY

 The present invention relates to determining a point cloud representing a surface of a spatial body. In particular, the present invention relates to determining a point cloud representing the surface of a moving spatial body.

BACKGROUND

 The determination of the geometry of spatial bodies opens up a variety of technical applications. However, while the determination of the geometry of a stationary body by means of a stationary measuring system is known from the prior art, in the determination of the geometry of spatial bodies which are moved relative to the measuring system, a large number of unsolved or insufficiently solved technical challenges.

SUMMARY

 The present invention provides an apparatus enabling the determination of a point cloud representing a surface of a spatial body. The term "point cloud" is to be understood in particular as meaning a multiplicity of (spatially distributed) points which at least approximately reproduce or reproduce the surface of a spatial body. As a spatial body in this context, in particular, such a body is considered, which expands in three mutually orthogonal spatial directions. The term "surface" is further intended to mean both the entire surface of the spatial body, i. H. the envelope of the spatial body, as well as one or more portions of the envelope of the spatial body are understood.

 The device according to the invention comprises a first measuring device configured to continuously determine a position and orientation of the spatial body relative to the first measuring device, a second measuring device configured to measure coordinates of a plurality of points on the surface of the spatial body relative to the second measuring device, wherein the Coordinates of each point of the plurality of points is associated with an indication as to a time point of the measurement of the coordinates; and calculating means arranged to correct the coordinates of the plurality of points for the influence of a relative movement between the spatial body and the second measuring device based on the continuous one Determining the position and orientation of the spatial body relative to the first measuring device and a (known time-invariant or continuously measured) positional relationship between the first measuring device and the second fair device, wherein the corrected by the influence of the relative movement coordinates of the plurality of points determine the point cloud.

 The device according to the invention thus comprises, in addition to a measuring device which scans / scans the surface or the surface profile of the spatial body, a further measuring device which determines the relative movement between the first measuring device and the spatial body during the scanning / scanning. The relative movement can be determined in particular by determining a (measurement) time series based on successive position and / or orientation of features of the spatial body. As characteristics, both intrinsic and extrinsic features of the spatial body, such as characteristic contours present on the spatial body or markings applied to the spatial body, are to be considered in the context of the application, which are removed again after operation of the device. Further, the determination of the relative movement may be supported by determining the velocity or acceleration of the spatial body.

The coordinates of the points measured by the second measuring device, insofar as they are assigned different measuring times, are transformed to a common point in time by taking into account the positional relationship between the first measuring device and the second measuring device by the relative movement between the first Measuring device and the spatial body is corrected. If the first measuring device and the second measuring device are in a fixed (time-invariant) positional relationship to one another, for example by being mounted on a rigid holder, then the relative movement determined by the first measuring device can be used directly. The device thus makes it possible to determine a point cloud, which represents the surface of the spatial body, with simultaneous movement of the device, the spatial body, or the device and the spatial body. Furthermore, the device can also be used when there is no relative movement or no continuous relative movement between the device and the spatial body. Furthermore, during operation, the device can be guided around the spatial body, so that the entire surface of the spatial body can be scanned / scanned. Furthermore, interesting regions or regions can be more complex Surface or surface curve are scanned / scanned several times (optionally under different perspective angles).

 Preferably, the second measuring device is adapted to emit electromagnetic radiation and to detect backscattered electromagnetic radiation on the spatial body.

 The electromagnetic radiation can be, for example, electromagnetic radiation in the visible spectrum, infrared spectrum or radar radiation. By measuring the signal travel between emitted and backscattered electromagnetic radiation, for example (polar) coordinates of reflection points on the surface of the spatial body can be measured. As an alternative to electromagnetic radiation, the device can also emit (ultra) sound waves, for example when the device is used in a body of water or when very short distances between the second measuring device and the three-dimensional body are to be expected.

 Preferably, the first measuring device comprises a stereo camera module and the second measuring device comprises a laser scanner module.

 By using a stereo camera module, it is possible in particular to determine a movement of the spatial body relative to the first measuring device by following the contour of the spatial body and / or one or more markings on the spatial body, for example by calculating the optical flow in the stereo camera image data or by feature detection. The use of a laser scanner as a laser light source, which emits light cyclically in predetermined spatial directions, allows a systematic scanning / scanning of the surface of the spatial body for reflection points. Further, the first measuring device and the second measuring device may be calibrated together, for example, by placing reflective colored markers in locations of known position relative to the device, and then operating the device in a calibration mode.

 The computing device is preferably set up to assign a body-fixed coordinate system to the spatial body, and the corrected coordinates relate to the body-fixed coordinate system.

 For example, the body can be assigned a Cartesian or polar coordinate system whose origin and orientation are in constant relation to the spatial body. The term "constant relationship" in this context means that a real point on the surface of the spatial body in an ideal (error-free) body-fixed coordinate system has identical (time-invariant) coordinates at all times.

 Preferably, the computing device is configured to determine a movement of the body-fixed coordinate system relative to the first measuring device based on the continuously determined position and orientation of the spatial body.

 By determining the relative movement, the position and orientation of the spatial body can be interpolated at arbitrary times. For example, the position and orientation of the spatial body may be described as a transformation comprising a translation vector (position) and a rotation matrix (orientation) comprising 6 degrees of freedom. Each translation vector and each transformation matrix is assigned the time that they represent. In order to interpolate a translation vector and a transformation matrix between two times, the translation vector and the transformation matrix can be corrected for expected motion based on the determined relative motion so that they approximately describe the position and orientation of the spatial body at the interpolated time.

 Preferably, the computing device is adapted to estimate a movement model of the determined relative movement of the body-fixed coordinate system and to use this to support the continuously determined position and orientation of the spatial body.

 For example, the computing device may be configured to implement a Kalman filter algorithm during operation. By using the Kalman filtering algorithm, given the appropriate estimation of the accuracy of the measurements of the first measuring device and the movement descriptive motion model, the new transformation can be improved in accuracy by a predicted (averaged) averaging transformation.

 The computing device is preferably set up to assign an accuracy value to each point of the point cloud.

For example, the accuracy value may be a numerical value that allows one to estimate with what probability a distance between a particular point and a corresponding surface point of the spatial body is less than a predetermined value. Of the Accuracy value may be calculated from an accuracy value of the current transformation, for example represented by the corresponding covariance matrix of the Kalman filter, and an accuracy value of the measurement of the second measurement device.

 Preferably, the accuracy value is a weighted average based on measurement accuracy values of the first and second measuring devices.

 By assigning accuracy values inaccurately recorded surface areas can be determined and measured again in response to it. Furthermore, thus based on the determination of the point cloud (successive) operations or decisions can be adapted to the achieved accuracy.

 Preferably, the first and second measuring devices are mounted pivotably relative to one another and the device comprises sensors which are configured to continuously transmit measured values regarding the relative position and / or relative orientation between the first and second measuring devices to the computing device during operation and the computing device is adapted to to use the continuously transmitted measured values with regard to relative position and / or relative orientation for updating the positional relationship.

 For example, the first measuring device can be coupled to the second measuring device by means of one or two or a plurality of ball or rotary joints. Further, an incremental encoder or an electric (step) motor may be attached to one or more joints, allowing it to set an angle between the arms forming the joint.

 A method for determining a point cloud, which represents a surface of a spatial body, preferably comprises operating the device according to the invention, wherein the device and the spatial body are moved during operation relative to a fixed point on the earth's surface.

 By the term "fixed point on the earth's surface" is meant any point on the earth's surface which rests during operation of the device.

 Preferably, the first measuring device and the second measuring device are synchronized, for example by (at least some) measurements being carried out at (approximately) the same time or triggered by a common triggering signal. Furthermore, a measuring frequency of the second measuring device is preferably an integer multiple of the measuring frequency of the first measuring device, or vice versa.

BRIEF DESCRIPTION OF THE DRAWINGS

 The invention is explained below with reference to an exemplary embodiment, reference being made to drawings in which:

1 a schematic representation of a preferred embodiment of the device according to the invention; and

2 a schematic flow diagram of the operation of the device shows.

DETAILED DESCRIPTION

1 shows a schematic representation of a preferred embodiment of the device according to the invention 10 , The device 10 includes a first measuring device 12 , a second measuring device 14 and a coupling device 16 , which is the first measuring device 12 with the second measuring device 14 combines. The coupling device 16 includes several arms 18 . 20 . 22 , which are connected to each other via ball joints or hinges, whereby the first measuring device 12 and the second measuring device 14 be adapted to different application scenarios in terms of their position and orientation. The coupling device 16 further comprises means for determining the angles between the arms 18 . 20 and 22 such as incremental encoders (eg encoders), which together with the known lengths of the arms, determine the position and orientation of the first measuring device 12 relative to the second measuring device 14 can be determined at any time. Furthermore, it can be provided, the arms 18 . 20 and 22 relative to each other by stepper motors to move. The stepper motors can be controlled by a control module arranged in the device, which, for example, controls the stepper motors according to a predetermined movement pattern. Furthermore, the control module can provide an interface for the remote control of the stepper motors, which receives control commands via a (radio) receiving module (for example a W-LAN module) arranged in the device. Alternatively, the coupling device 16 be rigid, for example by the first measuring device 12 and the second measuring device 14 in a common housing (not shown) are arranged.

The first measuring device 12 includes a stereo camera module that continuously images images from a variety of markers 24 . 26 and 28 takes on a spatial body 30 are attached. The marks 24 . 26 and 28 In their shaping and / or color / reflection behavior, they thus stand out from the spatial body 30 , the environment of the spatial body 30 and from each other that they by means of an image processing module, which is also in the first measuring device 12 is arranged and connected to the stereo camera module via a data line, in image data, the markers 24 . 26 and 28 can be clearly identified. From the identification and position determination of at least three clearly identifiable markers 24 . 26 and 28 firmly on the spatial body 30 are attached, for each recorded image pair, the position and orientation of the spatial body 30 uniquely determined and to a computing device 32 the device 10 be transmitted. If appropriate, a relative movement between the spatial body can then be determined from the time series of the position and orientation data obtained in this way 30 and the first measuring device 12 determined and further position and alignment data are interpolated. As in 1 shown, the transmission can be wireless, for example via a device in the device 10 provided (radio) transmission module (eg the W-LAN module) to the computing device 32 be transmitted. Alternatively, the computing device 32 be integrated into the common housing and the transmission via a data line (eg, via Ethernet) done.

The second measuring device 14 includes a laser scanner module, which continuously emits electromagnetic radiation and the spatial body 30 backscattered electromagnetic radiation detected. As in 1 indicated, the beams emitted by the laser scanner module lie in a plane 34 so that upon movement of the device 10 relative to the spatial body 30 with a direction vector 36 which is not parallel to the plane (eg the normal to the plane 34 ), one of the device 10 facing, extending in three dimensions portion of the envelope of the spatial body 30 (completely) can be scanned / scanned. By comparing the transit time between emitted and backscattered electromagnetic radiation, taking into account the (cyclically changing) radiation angle between emitted electromagnetic radiation and the second measuring device 14 the coordinates of a plurality of points on the surface of the spatial body 30 relative to the second measuring device 14 can be measured, wherein the coordinates of each point of the plurality of points can be assigned an indication of a time of measurement of the coordinates. The second measuring device 14 thus generates a plurality of surface reflection points, which together with an indication of the associated measurement time point to the computing device 32 the device 10 can be transferred. The transmission may, as above in connection with the first measuring device 12 described wirelessly, for example, about that in the device 10 provided (radio) transmission module, or if the computing device 32 is integrated in the common housing, by means of a data line (eg via Ethernet) done.

The computing device 32 , which has a (radio) receiving module (for example a W-LAN module) and / or via an interface for a data line, receives the information about the position and orientation of the spatial body 30 (relative to the first measuring device 12 ) and the coordinates of a plurality of points on the surface of the spatial body 30 (relative to the second measuring device 14 ), wherein the coordinates of each point of the plurality of points is associated with an indication of a time of measurement of the coordinates. From the coordinate time series to the point cloud, which is the surface of the spatial body 30 represents, to be determined, the coordinates of the points to the possibly occurring relative movement between the second measuring device 14 and the spatial body 30 corrected. For this purpose, the computing device generates 32 a body-fixed coordinate system 38 ie a coordinate system in which the surface points of the spatial body 30 are associated with movement of the same motion invariant coordinates. The computing device 32 further calculates a transformation (eg, translation vector values and rotation matrix values) that determine the position and orientation of the body-fixed coordinate system 38 relative to the first measuring device 12 defined (hereinafter referred to as "transformation between body-fixed coordinate system 38 and first measuring device 12 " designated). The transformation between a body-fixed coordinate system 38 and first measuring device 12 can then be based on the determined relative movement between the spatial body 30 and the first measuring device 12 be updated continuously. For this purpose, a movement model of the specific relative movement of the body-fixed coordinate system 38 which includes, for example, an acceleration vector can be estimated. The motion model can be used to support the continuous update, for example, by implementing a Kalman filter algorithm (KF, EKF, UKF, etc.). The motion model may also be used to interpolate the transformation for times for which the position and orientation of the spatial body 30 through the first measuring device 12 was not measured directly.

Taking into consideration the positional relationship between the first measuring device 12 and the second measuring device 14 can for everyone Measuring time from the (interpolated) transformation between body-fixed coordinate system 38 and first measuring device 12 a transformation between the body-fixed coordinate system 38 and the second measuring device 14 which calculates the position and orientation of the spatial body 30 relative to the second measuring device 14 defined (hereinafter referred to as "transformation between body-fixed coordinate system 38 and second measuring device 14 " designated). The second measuring device 14 measured coordinates of the plurality of points on the surface of the spatial body 30 relative to the second measuring device 14 can then be applied by applying transformations (in terms of time) between body-fixed coordinate system 38 and second measuring device 14 be corrected to the possibly occurring relative movement.

2 shows a schematic flow diagram 40 the operation of the device 10 out 1 , where optional steps are indicated by rectangles with a dashed line. The flowchart starts at 42 and 44 with taking pictures through the first measuring device 12 and detecting a laser beam reflection by the second measuring device. After taking the pictures are at 46 the marks 24 . 26 and 28 searched in the image data. From the found marks 24 . 26 . 28 is at 48 the position and orientation of the spatial body 30 certainly. At the same time or slightly delayed, be at 50 from the detected laser beam reflection coordinates of a point on the surface of the spatial body 30 measured. In this context, it should be noted that the use of a stereo camera module in the first measuring device 12 and a laser scanner module in the second measuring device 14 is purely exemplary. So can in the first measuring device 12 In principle, any (non-contact) measuring technology is used, which is capable of a position and orientation of the spatial body 30 relative to the first measuring device 12 to determine. Furthermore, in the second measuring device 14 In principle, any (non-contact) measuring technology is used, which is capable of coordinates of a plurality of points on the surface of the spatial body 30 relative to the second measuring device 14 to eat.

The coordinates are included 52 a relative movement between the second measuring device 14 and the spatial body 30 corrected to compensate for the relative movement occurring during the continuous measurement of the coordinates. The corrected coordinates are included 54 summarized to a point cloud, which represent or emulate the surface or the surface profile of the spatial body. Are the measuring times, which include the position and orientation of the spatial body 30 relative to the first measuring device 12 was not synchronous with the times of measurement of coordinates, can at 56 the position and orientation of the spatial body 30 relative to the first measuring device 12 from the specific positions and orientations of the spatial body 30 relative to the first measuring device 12 be interpolated. The interpolation can at 58 by following the relative movement between the spatial body 30 and the first measuring device 12 be supported. Tracking the relative movement between the spatial body 30 and the first measuring device 12 can also be a movement model 60 use. Furthermore, as with 62 shown, the markers are tracked. The tracking of the marks can be based solely on the analysis of the image data (optical flow) or additionally supported by the tracked relative movement.

LIST OF REFERENCE NUMBERS

10

contraption

12

First measuring device

14

Second measuring device

16

coupling device

18

(Joint) arm

20

(Joint) arm

22

(Joint) arm

24

mark

26

mark

28

mark

30

Spatial body

32

computing device

34

level

36

direction vector

38

Body-fixed coordinate system

40

flow chart

42

Process step: taking pictures

44

Process step: detecting a laser beam reflection

46

Process step; Finding marks

48

Process step: Determining the position and orientation of the body

50

Process step: measuring the reflection coordinates

52

Process step: Correct the coordinates by the (interpolated) relative movement

54

Process step: Determining the point cloud

56

Process step: Interpolation of the relative movement

58

Process step: tracking the relative movement

60

movement model

62

Process step: Tracing marks

Claims (10)

Contraption ( 10 ) for determining a point cloud, which is a surface of a spatial body ( 30 ), comprising: a first measuring device ( 12 ) arranged to continuously determine a position and orientation of the spatial body ( 30 ) relative to the first measuring device ( 12 ); a second measuring device ( 14 ) arranged to measure coordinates of a plurality of points on the surface of the spatial body ( 30 ) relative to the second measuring device ( 14 ), wherein the coordinates of each point of the plurality of points is associated with an indication of a time of measurement of the coordinates; and a computing device ( 32 ) arranged to correct the coordinates of the plurality of points for the influence of a relative movement between the three-dimensional body ( 30 ) and the second measuring device ( 12 ), based on the continuous determination of the position and orientation of the spatial body ( 30 ) relative to the first measuring device ( 12 ) and a positional relationship between the first measuring device ( 12 ) and the second measuring device ( 14 ), the coordinates of the plurality of points corrected for the influence of the relative movement determining the point cloud. Contraption ( 10 ) according to claim 1, wherein the second measuring device ( 14 ) is adapted to emit electromagnetic radiation and to the spatial body ( 30 ) to detect backscattered electromagnetic radiation. Contraption ( 10 ) according to claim 1 or 2, wherein the first measuring device ( 12 ) a stereo camera module and the second measuring device ( 14 ) comprises a laser scanner module. Contraption ( 10 ) according to one of the preceding claims, wherein the computing device ( 32 ) is adapted to the spatial body ( 30 ) a body-fixed coordinate system ( 38 ) and the corrected coordinates are based on the body-fixed coordinate system ( 38 ) Respectively. Contraption ( 10 ) according to claim 4, wherein the computing device ( 32 ) is adapted to a movement of the body-fixed coordinate system ( 38 ) relative to the first measuring device ( 12 ) based on the continuously determined position and orientation of the spatial body ( 30 ) Contraption ( 10 ) according to claim 5, wherein the computing device ( 32 ) is adapted to a movement model of the determined relative movement of the body-fixed coordinate system ( 38 ) and this in support of the continuously determined position and orientation of the spatial body ( 30 ) to use. Contraption ( 10 ) according to one of the preceding claims, wherein the computing device ( 32 ) is arranged to assign an accuracy value to each point of the point cloud. Contraption ( 10 ) according to claim 7, wherein the accuracy value comprises a weighted average based on measurement accuracy values of the first measuring device ( 12 ) and the second measuring device ( 14 ). Contraption ( 10 ) according to one of the preceding claims, wherein the first measuring device ( 12 ) and the second measuring device ( 14 ) are mounted pivotably relative to each other and the device ( 10 ) Sensors, which are set up in operation to measure relative position and / or relative orientation between the first and second measuring devices ( 12 . 14 ) continuously to the computing device ( 32 ) and the computing device ( 32 ) is adapted to use the continuously transmitted measured values with regard to relative position and / or relative orientation for updating the positional relationship. Method for determining a point cloud which covers a surface of a spatial body ( 30 ), comprising: operating a device ( 10 ) according to one of claims 1 to 9, wherein the device ( 10 ) and the spatial body ( 30 ) are moved during operation relative to a fixed point on the earth's surface.

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