RU2683117C1 - Method of measurement on moving object of absolute value of gravity and gravimeters for its implementation - Google Patents

Abstract

FIELD: measurement.SUBSTANCE: invention relates to gravimetry and can be used for measurement of absolute values of acceleration of free fall on moving objects. Essence: gravimeter comprises one or two test bodies having two angle reflectors and a ballistic unit. Ballistic unit represents a ring rotating around the horizontal axis, on which one or several pairs of diametrically located carriages are fixed with functions of lowering and pickup of sample bodies. Besides, the ballistic unit is designed so that to enable falling one or simultaneously two test bodies along the measured trajectory and picking up them in the lower position by the carriage of the same or the next pair.EFFECT: technical result is exclusion of vertical translational movement of carriages, increased frequency of shots due to reduction of idle time, continuity of measurements.2 cl, 2 dwg

Description

The invention relates to the field of gravimetry and can be used to measure the absolute values of the acceleration of gravity in a moving object.

At present, gravity acceleration (USP) on a moving base is measured by the relative method [1], the disadvantage of which is inertia, since relative gravimeters are built on a highly damped elastic mechanical system. This leads to the fact that when measuring USP on a moving object, they get a smoothed profile, without its detail. If necessary, a detailed picture reduces the speed of the object, which increases the time and cost of shooting.

Symmetric [2] and asymmetric methods [3, 4] of absolute measurement of gravitational acceleration are known. In the symmetric method, the test body is thrown up and lowered to the starting point. The parameters of the ascending and descending branches of the trajectory are measured. The disadvantage of the symmetric method is the need to throw a test body with an acceleration many times greater than the acceleration of gravity. In this case, large mechanical loads and vibration of the system occur. In the asymmetric method, the body rises to the upper position without overloads, is released, falls freely, is picked up in the lower position, and then the cycle repeats. The parameters of only the descending branch of the trajectory are measured. A disadvantage of the known gravimeters [4] with an asymmetric measurement method is the use of a reciprocating movement of the carriages in the corresponding guides to pick up the test body below and raise it upward, which reduce the rigidity of the structure and the manufacturability of the device due to sliding friction pairs. Low manufacturability leads to a significant increase in the cost of manufacturing the device and prevents its serial use. In addition, reciprocating motion limits the frequency of the shots. During the movement of the test body to the upper position, an undesirable interruption in measurements occurs.

The invention is aimed at improving the manufacturability of the design and increasing the frequency of measurements.

This goal is achieved by the fact that the carriages are placed on a rotating ring and raised along an arc of a circle. Two corner reflectors are mounted symmetrically on opposite sides on the test body. Laser beams are sent to the test body from above and below. Provide measurement of the parameters of the general trajectory for two simultaneously falling test bodies. The ballistic block ring is rotated continuously.

The ballistic block of an absolute gravimeter is a ring with a horizontal axis of rotation, on which one or more pairs of diametrically located carriages are fixed. Each pair of carriages has one test body. On the test body, two corner reflectors are installed on opposite sides. Laser beams are directed at the incident body from above and below. If there are several pairs of carriages, in one pair test bodies are placed in both carriages. One or two test bodies may be on the measured fall path. The ballistic unit ring rotates discretely or continuously.

The technical effect consists in eliminating vertical translational movements of the carriages, increasing the frequency of the throws by reducing, up to the exception, the idle time and ensuring continuity of measurements, which can be useful when measuring the gravitational field on a fast moving object.

The gravimeter device is shown in FIG. 12.

The figures show: 1 - ring, 2 - axis of rotation of the ring, 3, 4, 5 - bearings, 6 - drive rotation of the ring, 7, 8, 9, 10 - carriage, 11, 12 - the first and second test bodies, 13, 14 - laser beams, 15 - third test body, 16 - brake, 17, 18, 19, 20 - gaps with springs, ω - direction of rotation of the ring.

Ring 1 with a horizontal axis of rotation 2 is installed in the supports 3, 4, 5. Its rotation is carried out by the drive 6. On the ring, the carriages 7, 8 and 9, 10 are open in pairs and open towards the axis of rotation. In figures 1 and 2 shows two pairs of carriages. In one of the carriages of each pair, the first and second test bodies 11, 12 with two corner reflectors located on opposite sides of the body are fixed. The measurements are made by two laser beams 13, 14. To ensure the continuity of measurements, a third test body 15 is used, which is initially installed in the carriage 10. If the ring rotates without stops, the carriages are held by the brake 16 and remain stationary by reducing the size of the gaps 17, 18, 19 , 20 and compression springs.

In FIG. 1, ring 1 is rotated clockwise around axis 2 in bearings 3, 4, 5 by means of drive 6. Rotation is stopped when one of the pairs of carriages, for example 7, 8, is mounted vertically. Other carriages are randomly positioned. The locking device of the upper carriage releases the test body 11, and it falls into the lower carriage, where it is attached. At this time, another test body 12 remains stationary. In FIG. 1, the body falls from the carriage 7 into the carriage 8. During the fall, the acceleration of gravity is measured using laser beams 14, 15 directed from above and below by two corner reflectors of the test body. The ring is rotated using drive 6 and stopped when the next pair of carriages is located vertically. Measurements are repeated.

To ensure the continuity of measurements (Fig. 2) in one of the pairs of carriages, for example 9, 10, put test bodies in both carriages. In this case, when the carriages 9.10 rise vertically from the carriage 10, the test body 15 falls out. While it is flying, they rotate so that the next pair 7, 8 is installed in the vertical and the test body 11 begins to fall. In FIG. 2, body 11 falls from carriage 7 to carriage 10, body 15 - from carriage 10 to carriage 8, and body 12 - from carriage 9 to carriage 7. As a result, two test bodies are in flight, each of which will fall into the carriage of the next pair.

With continuous rotation of the ring, the carriages are provided with a backward shift due to gaps 17-20. When abutting the brake 16, the movement of the carriage stops, compressing the corresponding springs. The test body falls out of the carriage. The brake is released and the carriage spring returns to its original position on the ring. Since the mass of the carriage and its moment of inertia during rotation around the axis of the ring are at least 10 times less than the same characteristics of the entire ring, its stop will be accompanied by less overloads and vibrations.

The calculations are based on the parameters of the known gravimeter [4]

. Если измерять УСП по двум пробным телам, падающим одновременно (фиг. 2), то частоту бросков можно увеличить до f₂=12 Гц с увеличением точности за счет увеличения количества измерений. Если считать один бросок - одно измерение, то при движении объекта со скоростью звука -

, ускорение свободного падения можно измерять через ΔS=25 м. Это дает возможность съемки детального гравитационного рельефа местности и точной навигации по рельефу, причем и то и другое делать на высоких скоростях движения объекта. Учитывая возможность [5] измерения УСП при прохождении пробным телом расстояния в длину волны света, можно увеличить дискретность измерений. Например, после отпускания в свободном падении первый участок в длину волны пробное тело пройдет за τ₁=3*10^-4 с, а последующие быстрее. В этом случае дискретность измерений сократится до ΔS₁<0,1 м.If we take the fall height [4] h = 34 mm, and the fall time τ = 0.083 s, then, together with the time for turning, releasing and fixing, one measurement cycle will take, let us assume, τ ₁ = 0.15 s. For the circuit of FIG. 1 throws can be made with a frequency

. If USP is measured by two test bodies falling simultaneously (Fig. 2), then the frequency of the surges can be increased to f ₂ = 12 Hz with an increase in accuracy due to an increase in the number of measurements. If we consider one throw - one measurement, then when the object moves with the speed of sound -

, the acceleration of gravity can be measured through ΔS = 25 m. This makes it possible to shoot a detailed gravitational terrain and accurate navigation along the terrain, both of which can be done at high speeds of the object. Given the possibility [5] of measuring USP when a test body travels a distance in the wavelength of light, it is possible to increase the discreteness of measurements. For example, after letting go in free fall, the first section in the wavelength of the test body will pass in τ ₁ = 3 * 10 ^-4 s, and the subsequent faster. In this case, the discreteness of measurements will be reduced to ΔS ₁ <0.1 m

In the case of continuous rotation, only the upper carriage stops. The test body should fall into the carriage of the next pair. In this case, the rotation speed should be constant and depend on the number of carriages n. For an example with four carriages n = 4, the turn time per quarter turn should be equal to the time of the fall of the body

The angular velocity of rotation and the linear velocity of the ring in this case are equal

При остановке каретки, а не всего кольца, значительно уменьшаются механические нагрузки и вибрации, так как плавно тормозится сравнительно небольшой элемент гравиметра - каретка.If we accept the gaps 17, 18, 19, 20 with the value l = 0.005 m, then the overload when the carriage stops is insignificant

When the carriage stops, and not the entire ring, mechanical loads and vibrations are significantly reduced, since a relatively small element of the gravimeter — the carriage — is smoothly braked.

Using the inertia of absolute measurements, you can measure the profile or navigate the profile of the change in gravity at high speeds of the object.

Literature

1. Device and method for measuring gravity. Pat. RU 21984140 2002.03.03.14. Grew up. Federation: IPC G01C; Applicant and patent holder of the Federal State Unitary Enterprise Central Research Institute Elektropribor.

2. Germak A., Desogus S., Origlia C. Interferometer for the IMGC rise-and-fail gravimeter. Metrologia, 2002, vol. 39 n. 5, pp 471-475.

3. Vitukshkin L.F., Orlov O.A. Absolute ballistic gravimeter. Pat. RF №2475786 dated 05/06/2011.

4. Vitouchkine A.L., Faller J.E. Measurement results with a small cam-driven absolute gravimeter, Metrologia, 2002, vol. 39, n. 2, p. 465-469.

5. The method of measuring on a moving base the absolute value of the acceleration of gravity and gravimeters for its implementation. Pat. RU 2523108 2013 02 28 Ros. Federation: IPC G01C; Applicant and patent holder A. Popov B.

Claims (2)

1. An asymmetric method of measuring the absolute acceleration of gravity, which consists in moving the carriages with the test body to the upper position, releasing the test body, measuring the parameters of its fall path and picking it up in the lower position, characterized in that two opposite sides of the test body are installed corner reflector, one or more pairs of carriages are placed on a ring with a horizontal axis of rotation, the body is moved around the circumference to the upper position, then released from the upper carriage of one of the pairs, and measure the parameters of the trajectory of the fall of one or the common trajectory of two test bodies, and in the lower position, the body is picked up into the carriage of the same or subsequent pair. 2. An absolute gravimeter containing a test body falling along the measured path and a ballistic block with a carriage for lifting to the upper position of the test body, releasing it and picking it up in the lower position, characterized in that the test body is made with two angular reflectors located on opposite sides of the body , the ballistic block is a ring rotating around a horizontal axis, on which one or more pairs of diametrically arranged carriages are fixed with the functions of releasing and picking up a test bodies each, and ballistic unit configured to provide a drop of the measured trajectory of one or both of two test bodies and their pick-up carriage in the lowered position of the same or a subsequent pair.

Images