Abstract:
The shock isolation system for an inertial sensor arrangement, on the one hand, causes an advantageous moment of inertia by the special arrangement of the individual sensors, especially of the gyroscope used. On the other hand, an advantageous long interval of the required shock-absorbing components (“shock mounts”) is provided by the use of several tubular shells. A measurement device with this inertial sensor arrangement thus achieves improved accuracy and reliability.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to a shock isolation system for an inertial sensor arrangement. 
   2. Description of Related Art 
   A system for isolation or damping of vibrations acting on an inertial sensor arrangement is known from U.S. Pat. No. 5,890,569 (inventor—Goepfert). 
   Making available a shock isolation system for inertial sensor arrangements, especially those with optically operating gyroscope systems, or highly sensitive accelerometers, always poses an especially serious problem for the engineer. On the one hand, long enough spring paths must be prepared to reliably capture impacts or mechanical shock effects, on the other hand, the relative position of the inertial sensor arrangement to be protected or isolated in relation to the measurement surfaces or edges to be defined may not be significantly changed by the effect of temperature or its position changes within the framework of measurement accuracy. In this connection, it has been proposed that these devices be equipped with very compliant impact protection devices which are deactivated for a short time at the instant of measurements, and during the remaining time impart shock and impact protection (U.S. Pat. No. 6,457,373). 
   SUMMARY OF THE INVENTION 
   The object of the invention is to devise improved shock, impact and vibration isolation for an inertial sensor arrangement which is continually active, which distinctly improves the measurement accuracy of the inertial sensor arrangement, which is insensitive to position and temperature, and which is characterized by especially low weight, particularly for construction volumes as small as possible. 
   The invention is based on use of a multiple casing to increase the positional stability of the inertial sensor arrangement relative to a surrounding housing, hollow cylindrical components which are arranged essentially concentrically to one another being provided as shells in an innovative manner. 
   The invention is furthermore based on a long spacing of the required shock damping components (“shock mounts”) being formed by using several tubular shells, which spacing significantly increases the precision of the inertial sensor arrangement but, nevertheless, offers the required protection against higher external accelerations. 
   In particular, the invention calls for a number of shock mounts to be provided, with centers which span the volume of a prism with an area which has a diameter of a maximum 50% of the length of the prism. 
   The invention is also based on the fact that, in one special arrangement of the individual gyro systems within the inertial sensor arrangement, an especially advantageous mass distribution or an especially advantageous moment of inertia is achieved. The moment of inertia created in this way greatly improves the effectiveness of the so-called dithering within the gyroscope. This applies especially to gyro systems which are designed primarily for determining the angle coordinates “azimuth” (=“yaw”) and “elevation” (=“pitch”). 
   The invention is explained in detail below with reference to the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows the general structure of an inertial probe in accordance with the invention; 
       FIG. 2  shows the arrangement of shock reducing supports within the inertial probe; 
       FIG. 3  shows the shock reducing supports with shock mounts; 
       FIG. 4  shows the combination of shock reducing supports, shock mounts and an internal sensor platform; 
       FIG. 5  shows the internal sensor platform with shock mounts and an electrical connection; 
       FIG. 6  shows the combination of internal sensor platform, internal sensor mounting and a sensor; 
       FIG. 7  shows an internal sensor mounting; and 
       FIG. 8  shows a preferred arrangement of three sensor mountings for three sensors. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  shows, in a outside view, the general shape of the inertial probe in accordance with the invention. It has an essentially cylindrical shape; this is due to a cylindrical outside jacket  10 . Carrying handles  20 ,  30  are attached to it. With these carrying handles, the inertial probe can be seated by means of skids  40 ,  50  on the articles to be measured, or can be pivoted on cylindrical objects according to the teaching of German Patent Application DE 101 94459.4 and corresponding U.S. Pat. No. 6,591,218, which is incorporated by reference to the extent necessary to complete an understanding of this aspect of the invention. Using the cylindrical outside jacket  10  yields an economical arrangement which is characterized by especially high mechanical stability. 
   As  FIG. 2  shows, a set of shock reducing supports  60 ,  70  is provided in a concentric arrangement within the cylindrical outside jacket  10 . A number of shock mounts  82 ,  83 ,  84 ,  85  etc. are attached to them precisely and without mechanical play. The important function of the shock mounts is to damp impacts possibly acting on the skids or the cylindrical outside jacket  10  of the probe so that the gyro systems of the probe are protected against high acceleration values. 
   In particular, the invention calls for a number of shock mounts to be provided, with centers which span the volume of a prism with an area which has a diameter of a maximum 50% of the length of the prism. The corresponding configuration of the shock reducing supports  60 ,  70  with a total of six high-precision shock mounts is shown separately in  FIG. 3 . 
     FIG. 4  shows how an internal sensor platform  80  is mounted coaxially to the outside cylindrical jacket by means of shock reducing supports and the shock mounts  82 - 87 . The internal sensor platform is preferably likewise of a stable, tubular (hollow cylindrical) shape and can have an opening so that electrical connections  89  to external electronics (not shown) can be set up by means of a plug device  88  or the like. 
   The internal sensor platform  80 , together with the holding shock mounts, is shown separately in  FIG. 5 . It is advantageous to produce the inner sensor platform from several pieces, for example, to provide end caps,  81 ,  81 ′ of roughly conical shape. 
     FIGS. 6 &amp; 7  show the arrangement of an internal sensor mounting  90 ,  92  within the internal sensor platform  80 . The mounting elements  90 ,  93  are especially suited to stably accommodate a gyroscope which senses azimuth and elevation. For this purpose, there can advantageously be a hollow cylindrical recess  93 . There can not only be a single mounting element, but also two or more combinations of mounting elements  90 ,  93  within the internal sensor platform  80 . 
   For an arrangement of three gyroscopes which interact in a gyro triad, an innovative arrangement of mounting elements and inertial sensors attached there, as shown in  FIG. 8 , is especially advantageous. The mounting elements  90 ,  94  arranged in the middle are suited in interplay with a mounting element  95  for holding a gyroscope (not shown) which detects mainly rolling revolutions around the lengthwise axis  100 . A mounting element  92  is flanged to it on the left and a mounting element  91  is in turn attached to it. This combination is suited to holding a gyro which detects mainly yaw movements. The mounting element  97 , together with the respective mounting element  96 , is flanged on the right to the mounting element  94 . The mounting element  97  is suited to holding a gyroscope which detects mainly pitch movements. 
   The important advantage of the arrangement shown in  FIG. 8  is especially that ring laser gyroscopes held in mounting elements  92 ,  97 , work with significantly better precision than if the conventional arrangements are used which are aligned essentially cubically. This is based on the fact that the reaction moments which are delivered by the so-called dither motors of the gyros and which are ultimately buffered by the shock mounts, now meet with distinctly increased moments of inertia, i.e., the inertial sensors are arranged such that effective moments of inertia of their masses, as compared to the compliance of the shock mounts by which the inertial sensors are attached, assume values that are as large as possible. The intended small vibration motion of the gyro housing around this theoretical axis, in this way, becomes smaller than in the normal case, but, due to the ratio of the moments of inertia to elasticities, in an altogether more reproducible and thus more accurate manner.