CH707495B1 - Assembly system with an opto-electronic instrument and an inertial navigation system for a carrier vehicle. - Google Patents

Abstract

The invention relates to a mounting system with an opto-electronic instrument and an inertial navigation system for a carrier vehicle. The optoelectronic instrument (1) is connected to an inertial navigation system (23) for detecting the orientation of the instrument in space to a rigid module (3), which inertial navigation system is capable of resolving periodic movements up to a defined cutoff frequency, the corresponding data with the measured values of the optoelectronic instrument, can be linked to data sets, and the module (3) formed from the instrument (1) and the navigation system (23) is connected to the structure of the carrier vehicle via spring / damping elements (24, 26) which together with the mass of the module (3) form a mechanical low-pass filter, which substantially absorbs vibrations that are above the cutoff frequency, while the module (3) follows low-frequency movements and the data of the respectively changed spatial orientation of the module (3) for linking with the measured values of the instrument (1).

Description

Description: The invention relates to a mounting system with an optoelectronic instrument and an inertial navigation system for a carrier vehicle, the optoelectronic instrument with the inertial navigation system for detecting at least the orientation of the instrument in space, but possibly also for determining the position of the same in a coordinate system is connected to a rigid module, which inertial navigation system is able to resolve periodic movements up to a defined cut-off frequency, the corresponding data being able to be linked to the measured values of the optoelectronic instrument, for example those of a laser rangefinder or a laser scanner, and that from the module formed by the instrument and the navigation system is connected to the structure of the carrier vehicle via spring / damping elements, also referred to here as “damping elements, in particular spring elements”.

The carrier vehicles can be land or rail vehicles, watercraft or aircraft such as surface planes or helicopters, in which, during the same movement, measurements, photographic recordings or the like are made. All these carrier vehicles have in common that they can move about one or more axes during these measurements, recordings or the like. In order to ensure a corresponding assignment to the space to be measured or recorded, it is known to combine the optoelectronic instrument with an inertial navigation system (IMU) and to connect it as rigidly as possible, so that the orientation of each measurement, recording or the like optical axis of the instrument in space can be recorded in terms of data. As a rule, such an instrument is also combined with a navigation system with which its respective position is determined in a higher-level, for example global, coordinate system. In principle, wheel sensors can also be used as such navigation systems in rail and land vehicles, but satellite-based systems (GNNS, for example GPS) have largely proven themselves for all of these applications, which in many cases use an inertial navigation system (IMU) to form an integrated IMU / GNNS System are combined. This gives you the exact coordinates for each measuring point in a higher-level coordinate system.

The optoelectronic instruments are not only exposed to the intended movements of the carrier vehicle during use, but also shocks, shocks, vibrations, etc., which are transmitted from the structure of the carrier vehicle to the instruments. Such instruments usually include shock and vibration sensitive components and must therefore be connected to the structure of the carrier vehicle with spring / damping elements to protect them.

According to the invention, the spring / damping elements form, in a manner known per se, together with the mass of the module, a mechanical low-pass filter which essentially absorbs vibrations of the carrier vehicle, which are above the limit frequency of the inertial navigation system, and thus stabilizes the module in space, while the module follows lower-frequency movements of the carrier vehicle and provides the data of the respective changed spatial orientation of the module for linking to the measured values of the instrument.

Mechanical low-pass filters are, as mentioned above, already known per se and, for example, in US Pat. No. 6,688,174-B1 (Pierre Gallon et.al.) and in German Offenlegungsschrift DE 10 2010 062 017 A1 (Robert Bosch GmbH). The first publication relates to the vibration-damped suspension of a laser gyroscope system, the second to the shock and vibration damping of micro-projectors. The mechanical low-pass filters are described in a completely different context in both applications and therefore could not provide any suggestion for the present invention.

In some installations of optoelectronic instruments, these are not mounted directly on the carrier vehicle, but on a stabilized platform arranged on the carrier vehicle. In such a case, according to the invention, at least the module formed from the instrument and the navigation system is mounted on the stabilized platform with the interposition of spring / damping elements, the spring / damping elements together with the mass of the module forming a mechanical low-pass filter which is known per se, which essentially absorbs vibrations of the stabilized platform, which lie above the limit frequency of the inertial navigation system, but transmits low-frequency vibrations to the module.

According to a further feature of the invention, the mounting system comprises a two-stage mechanical decoupling, wherein on the one hand the rigid module is mechanically decoupled from the support structure by means of damping elements in order not to transmit deformations of the same to the module and on the other hand the spring / damping elements which together form with the mass of the module and its support structure a mechanical low-pass filter which is known per se and which essentially absorbs vibrations of the support vehicle which are above the cutoff frequency, but transmits low-frequency vibrations to the module.

For the most commonly used inertial navigation systems (IMU) and carrier vehicle / instrument configurations, the cutoff frequency is preferably about 25 Hz.

According to a further feature of the invention, the module is movably suspended or braced in all three coordinate directions.

CH 707 495 B1 [0010] The spring and damping elements at the individual points of attack on the module are preferably designed, taking into account their position with respect to the center of gravity of the module, so that both longitudinal and torsional vibrations or deformations can be largely damped.

According to the invention, the spring / damping elements are designed and positioned on the module such that, based on the center of gravity of the module, the sum of the moments of those forces that can be transmitted to the module is essentially zero.

In applications in which the measuring distance is significantly greater than the dimensions of the instrument module, displacements of the module in longitudinal directions have only a very slight effect on the measurement results, while the system is extremely sensitive to rotary movements of the module. In order to avoid the excitation of such rotary movements or torsional vibrations as far as possible, the spring and damping elements according to the invention are designed at the individual points of attack on the module, taking into account their position with respect to the center of gravity of the module, so that torsional vibrations can be largely damped.

Preferably, the spring / damping elements are designed and positioned on the module that based on the center of gravity of the module, the sum of the moments of those force components that are transferable to the module and normal to the optical axis of the optoelectronic instrument, in Is essentially zero. This measure allows longitudinal movements in the direction of the optical axis of the instrument and normal to it, while excitation of torsional vibrations is suppressed.

In order to avoid interference with the module when mounting additional devices such as digital photo or video cameras or navigation devices or their sensors, connecting pieces are provided on the outside of the module for rigid attachment of these additional devices. Since the total mass of the module is changed by the installation of such additional devices, which has an effect on the coordination of the mechanical low-pass filter formed from the spring / mass system, it is advantageous to first provide compensation masses on the connecting pieces on the outside of the module, which reduces accordingly when installing additional devices become.

Further features of the invention will become apparent from the following description of some exemplary embodiments and with reference to the drawing. 1 shows, as an example of an optoelectronic instrument, a laser scanner for airborne applications, partly in section. 2 shows a ready-to-install instrument in an axionometric view, FIGS. 3 and 4 illustrate two different mounting systems for two essentially identical instrument modules.

The laser scanner shown in FIG. 1 as an example of an optoelectronic instrument for “airborne” applications essentially comprises a laser range finder 1 according to the pulse transit time method and a downstream beam deflection device 2. In the example shown, the Beam deflecting device a glass wedge prism 11 which rotates at high speed around the optical axis 7 of the laser range finder 1.

The instrument is built on a mounting plate 31 which is connected to four columns 32 with a plate 33 and forms a stable and rigid frame with these. A laser source 4 is arranged within this frame 31-33 and reflects a laser beam into the optical axis 7 of the instrument via a mirror system 5, 6. Instead of the mirror system 5, 6, a flexible glass fiber light guide can also be used.

Under the laser rangefinder 1, a cylinder 8 is provided which is rotatably supported in bearings 9 about the optical axis 7 of the laser rangefinder 1 and is driven by an electric motor 10 at high speed. The glass wedge prism 11 is mounted in this cylinder, through which the transmission laser beams are deflected. When the wedge prism 11 rotates, these laser beams 12 in their entirety form a beam cone which scans a flat area lying under the laser scanner in the manner of a circular arc. The laser beams are generally diffusely reflected by the terrain and the objects, vegetation etc. present on it. A small part of this radiation reaches the laser scanner again, is aligned parallel to the optical axis 7 by the wedge prism 11 and is imaged on the light-sensitive cell of the receiver 15 by the receiver optics 14. In the receiver 15, the incoming optical pulses are converted into electrical signals. In an evaluation device, not shown, which can also be arranged externally and connected to the laser scanner with a cable, the electrical pulses are possibly digitized. The distance from the laser scanner is determined from the time period from the transmission of the laser pulses to the arrival of the received pulses. An angle decoder (not shown) is attached to the rotating cylinder 8 or to the drive motor 10. The respective direction of the laser beam 12 in an instrument-related coordinate system results from the data of this decoder. Digital photo cameras 17 and / or video cameras 18 can be arranged on the stationary lower part 16 of the instrument. These cameras and the laser scanner are protected against environmental influences by an exit window 19. The distance data supplied by the evaluation device are linked to the instrument-related coordinates derived from the angle decoder and are stored together with the data from any digital cameras 17, 18 as a data record.

In order to be able to transform the instrument-related data into a higher-level, for example global, coordinate system, it is necessary on the one hand to determine the orientation of the instrument 1, 2 in space and to link this with data derived from a navigation system. An inertial navigation system (IMU), 23, is used to determine the position of the instrument in space. The navigation system ba

CH 707 495 B1 is usually based on a satellite-based system (GNNS, e.g. GPS). When this navigation system 23 is arranged on the instrument 1, 2, it is of crucial importance that the inertial navigation unit (IMU), 23 is connected to the instrument in a completely rigid manner, in this case with the laser scanner 1, 2 to form a module 3. This module 3 comprises a platform 20 on which on the one hand the lower instrument part 16 with the rotating wedge prism 11 is arranged, on the other hand the platform 20 carries the receiver optics 14 with the receiver unit 15, as well as four columns 21 which are welded to a plate 22. The inertial navigation unit (IMU), 23 is rigidly attached to this plate 22.

The laser source 4 is also connected to this frame 21, 22. The module 3 consisting of laser scanner 1, 2 and the inertial navigation unit IMU, 23 is connected to the mounting plate 31 and the plate 33 with damping elements 24. These elements 24 serve primarily to prevent deformations of the outer structure 31-33 of the instrument, which may result, for example, from uneven heating thereof, to the module 3.

The optoelectronic instruments installed in the carrier vehicles, for example in planes and helicopters, are exposed to vibrations and a wide spectrum of vibrations and shocks, which are excited by drive motors, but also by external influences. The same applies to water, land and rail vehicles. If the instruments are exposed to these forces, many of these optoelectronic instruments react relatively insensitively to dislocations in the direction of the optical axis 7 and normal to it. What is critical, however, is when these forces excite torsional vibrations of the instruments around axes normal to the optical axis. As a rule, the measuring distance is several orders of magnitude larger than the instrument, so that there are considerable displacements of the measuring points even with small torsional vibrational amplitudes. In the case of low-frequency vibrations, this can be compensated for by measuring the inertial navigation system (IMU), 23, the changes in the orientation of the instrument and assigning the measured values correspondingly changed instrument-related coordinates. With higher-frequency vibrations, which the IMU cannot follow, unacceptable measurement errors occur. This problem occurs not only with laser scanners, but also, for example, with digital photo and video cameras and many other instruments with a wide variety of optoelectronic sensors. According to one feature of the invention, this problem can be solved in that the mounting points of the instrument in the carrier vehicle are selected such that the forces introduced into the system are directed towards the center of gravity of the instrument, or the moments of these forces relating to the center of gravity of the instrument are compensated.

Such an arrangement is shown in FIG. 2. The laser scanner 1, 2 has been changed slightly from that shown in FIG. 1, in particular as regards the arrangement of the damping elements 24 and their support on the outer frame and the instrument module 3. A further plate 25 is provided under the mounting plate 31 of the laser scanner 1, 2, on which four so-called wire rope springs 26 are fastened. The other side of these springs 26 is connected to the platform 27, which can be fastened to the structure of the carrier vehicle with screws, not shown. The springs are matched to the mass of the instrument module 3 in such a way that, together with the latter, they form a mechanical low-pass filter. The cut-off frequency is selected such that only vibrations can reach the instrument module 3 that can still be measured by the IMU, 23. The plate 25 is positioned on the instrument in such a way that the plane of its underside, via which forces excited by the carrier vehicle are introduced into the system, contains the center of gravity 28 of the instrument, including the plate 25. This largely suppresses torsional vibrations of the instrument around axes that are normal to the optical axis.

The spring arrangement 25 to 27 represents an integrating part of the instrument, which is specially matched to the system and is installed or removed together with this in the carrier vehicle. In the example shown, a two-stage mechanical decoupling is implemented. A first, 24, which prevents the transfer of deformations to the module and a second, 25 to 27, which minimizes the effects of the vibrations, vibrations and forces introduced into the system by the carrier vehicle.

3 shows a further example of the assembly of an optoelectronic instrument which is intended for use in a carrier vehicle, with the illustration of the rigid frame structure fastened to the carrier vehicle being dispensed with for reasons of better clarity. The module 3 consisting of laser scanner 1, 2 and IMU, 23 is supported on the one hand with the plate 31 and three spring / damping elements 29 and with the IMU housing via a single, similar spring / damping element 29 on this frame construction. Vibrations, vibrations etc. of the carrier vehicle act on the three spring / damping elements 29 attached to the mounting plate 31 and the single element 29 attached to the IMU housing via the frame construction. In this example, the center of gravity 28 of the module 3 lies on the instrument axis 7 at a distance a from this individual element 29. To the three elements 29 on the mounting plate 31, the distance from the center of gravity 28 is b, where a is 3 χ b. This balances the moments of the force components introduced, which are directed normal to the optical axis 7, and the excitation of a torsional vibration of the module is avoided.

4 shows an alternative arrangement of the spring / damping elements 29. These are arranged in the corners of a virtual cube and aligned with the center of the cube. The elements 29 are supported on the other side analogously to FIG. 3 on a frame construction, not shown, connected to the structure of the carrier vehicle. The center of the virtual cube essentially coincides with the center of gravity 28 of the module 3, so that no torsional vibrations of the module 3 are excited by the forces introduced. The elements 29 are coordinated in their entirety with the mass of the module 3 and represent a spring / mass system that is mechanical

CH 707 495 B1

Low-pass filter acts and only transmits forces in a frequency range to the module, which excite movements of module 3, which can be measured by the IMU, 23.

Instead of arranging the spring / damping elements 29 at the corner points of a virtual cube, this can also be arranged at the corner points of other regular bodies, for example at the corner points of a regular virtual tetrahedron.

In contrast to the instrument shown in FIG. 2 with a two-stage mechanical decoupling, the systems shown in FIGS. 3 and 4 have a one-stage mechanical decoupling.

Claims (12)

claims 1. Mounting system with an optoelectronic instrument and an inertial navigation system for a carrier vehicle, the optoelectronic instrument being connected to the inertial navigation system for detecting at least the orientation of the instrument in space, but also, if appropriate, for determining the position thereof in a coordinate system to form a rigid module, which Inertial navigation system is able to resolve periodic movements up to a defined cut-off frequency, the corresponding data can be linked to the measured values of the optoelectronic instrument, for example those of a laser range finder or a laser scanner, to form data records and the module formed from the instrument and the navigation system can also be linked the structure of the carrier vehicle can be connected via damping elements, in particular spring elements, characterized in that the damping elements, in particular spring elements (24, 26, 29) together with d he mass of the module (3) form a mechanical low-pass filter, which essentially absorbs vibrations of the carrier vehicle, which are above the cut-off frequency of the inertial navigation system (23), and thus stabilizes the module (3) in space, while the module (3) low-frequency movements follows the carrier vehicle and provides the data of the respective changed spatial orientation of the module (3) for linking to the measured values of the instrument (1, 2). 2. Mounting system according to claim 1, with a stabilized platform to be arranged on the carrier vehicle, characterized in that at least the module (3) formed from the instrument (1, 2) and the navigation system (23) with the interposition of the damping elements, in particular spring elements (24, 26, 29) is mounted on the stabilized platform, the damping elements, in particular spring elements (24, 26, 29), together with the mass of the module (3), forming a mechanical low-pass filter which vibrates the stabilized platform above the limit frequency of the inertial navigation system (23) are essentially absorbed, but transmits low-frequency vibrations to the module (3). 3. Mounting system according to claim 2, characterized in that the mounting system comprises a two-stage mechanical decoupling, wherein on the one hand the rigid module (3) is mechanically decoupled from the platform by means of first damping elements (24) in order not to deform the module (3) to transmit, and on the other hand second damping elements, in particular spring elements (26) together with the mass of the module (3) and its platform form a mechanical low-pass filter, which essentially absorbs vibrations of the carrier vehicle, which are above the cut-off frequency, but low-frequency vibrations on the Module (3) transmits. 4. Mounting system according to one of claims 1 to 3, characterized in that the cut-off frequency is approximately 25 Hz. 5. Mounting system according to one of the claims 2 to 4, characterized in that the module (3) is movably suspended on the platform in all three coordinate directions. 6. Mounting system according to one of claims 1 to 5, characterized in that the damping elements, in particular spring elements (24, 26, 29) at the individual points of attack on the module (3) taking into account their position with respect to the center of gravity (28) of the module (3rd ) are designed in such a way that both longitudinal and torsional vibrations can be damped. 7. Mounting system according to claim 6, characterized in that the damping elements, in particular spring elements (24, 26, 29) are designed and positioned on the module (3) that related to the center of gravity (28) of the module (3) the sum of Moments of those forces that can be transferred to the module (3) is essentially zero. 8. Mounting system according to one of claims 1 to 5, characterized in that the damping elements, in particular spring elements (24, 26, 29) at the individual points of attack on the module (3) taking into account their position with respect to the center of gravity (28) of the module (3rd ) are designed so that torsional vibrations can be damped. 9. Mounting system according to claim 8, characterized in that the damping elements, in particular spring elements (24, 26, 27) are formed and positioned on the module (3) that related to the center of gravity (28) of the module (3) the sum of Moments of those force components that can be transferred to the module (3) and that are normal to the optical axis (7) of the optoelectronic instrument (1, 2) are essentially zero. CH 707 495 B1 10. Mounting system according to one of the preceding claims, characterized in that on the module (3) connecting pieces for rigid attachment of video (18) and / or photo cameras (17) and / or of navigation systems especially their sensors and, if necessary, of compensation masses are provided. 11. Mounting system according to one of claims 2 to 10, characterized in that the platform (27) can be rigidly connected to the structure of the carrier vehicle and that the damping elements, in particular spring elements (26) between the module (3) and the platform (27) are provided. 12. Mounting system according to claim 11, characterized in that a housing of the module (3) has a flange (25) and damping elements, in particular spring elements (26) are arranged between this flange (25) and the platform (27) and the center of gravity ( 28) of the module (3) lies essentially in the plane of the flange (25). CH 707 495 B1 CH 707 495 B1