60 results about "Absolute gravity" patented technology

The invention discloses a simple and feasible calibration method for the relative attitude of a binocular stereo camera and an inertial measurement unit on the basis of the absolute gravity direction. The method comprises the steps that a gravity direction vector serves as a reference vector, expressions of the gravity direction vector under a camera coordinate system and under an IMU coordinate system are solved respectively to obtain the expressions of the same vector under the two different coordinate systems, and then the attitude change relationship between the two coordinate systems can be solved; finally, precision verification is performed through reprojection errors, and application of the calibration method in a visual odometer is supplied. Experiments show that the relative attitude between the camera and the IMU can be accurately solved through the method. The method can be used for assisting in vision positioning of mobile robots and spherical robots.

The invention discloses an absolute gravity measuring system and measuring method as well as a falling method of a free-falling body. The absolute gravity measuring system comprises a free-falling body device, a laser interference measuring device and a vibration isolation platform, wherein the free-falling body device is used for realizing free-falling motion of a falling object; the laser interference measuring device is used for measuring displacement generated during the free-falling motion of the falling object, and can realize accurate calibration of a measuring beam in a vertical direction by adopting a simplified structure; and the vibration isolation platform is arranged between the laser interference measuring device and the ground and is used for isolating influence of ground vibration on measurement. The absolute gravity measuring system has the beneficial effects that free-falling motion of the falling object is realized by adopting an elastic falling member suspension method, vibration influence of a motor drive system on the free-falling body device is reduced, and the accuracy of the gravity measuring result is improved; meanwhile, the zero crossing point (ZCP) feature of an interference fringe signal is computed by computer software so as to eliminate possible measurement deviation caused by a hardware circuit.

Gravity information for a gravity survey is obtained by using an array of relative gravimeters whose relative gravity measurement signals have been calibrated by using an absolute gravimeter to approximate absolute gravity measurements.

The invention provides a system for measuring absolute gravity of a freely falling body based on double interferometers. The system is provided with the interferometers which are symmetrical up and down; each interferometer comprises a fixed prism, a movable prism and a beam splitter; the interferometers are exposed to the irradiation of a laser light source of the same frequency to generate interference, respectively; the upper and lower movable prisms are arranged in the same falling body; optic centers of the upper and lower movable prisms are separated by a predetermined distance; the center of mass of the falling body is located between the two optic centers in the vertical direction. The system for measuring the absolute gravity of the freely falling body based on double interferometers is capable of eliminating the influence of deflection of the falling body on the measurement accuracy of the absolute gravity of the freely falling body. The invention also provides a method for measuring the absolute gravity of the freely falling body based on double interferometers.

The invention belongs to the field of inertial navigation and in particular relates to a method for compensating gravity of a nine-accelerometer gyro-free inertial navigation system. The method comprises the following steps: collecting output signals of nine accelerometers of the gyro-free inertial navigation system; obtaining a local latitude according to output of GPS (Global Positioning System); calculating a local absolute gravity value; mounting the system on a static base, enabling the system to be in a static state, only sensing the gravity by the accelerometers, recording output of the accelerometers at the moment and calculating a primary error conversion matrix of the gravity to the system according to a linear speed equation of the system; calculating an angular speed of the system; calculating a gravity compensation value; compensating the gravity of the system. The invention discloses a new gravity estimating method. The method can be used for compensating gravity in the navigation and is capable of effectively removing the influence of the gravity on measurement results of the accelerometers, calculating simply, generating no pressure on the calculation of the system and compensating the gravity of the system in real time.

The present invention provides devices and methods for reducing or eliminating sources of systematic errors in the measurement of absolute gravity or gravity field gradients; specifically, an improved test mass for an interferometer is disclosed that reduces the influence of nearby electromagnetic fields on a freefalling test mass.

The invention discloses a vibration isolation mechanism based on a ratio electromagnet. The vibration isolation mechanism comprises a load rod, a first balance mechanism, the ratio electromagnet, a second balance mechanism, a micrometric displacement sensor and a PID operation control unit. The longitudinal central axis of the load rod coincides with the longitudinal central axis of the ratio electromagnet. One end of the load rod is used for bearing a system where vibration isolation is going to be conducted. The first balance mechanism and the second balance mechanism are used for providing the horizontal tension capable of limiting the load rod on the longitudinal central axis of the ratio electromagnet. The output end of the micrometric displacement sensor is connected with the PID operation control unit. The output end of the PID operation control unit is connected with the ratio electromagnet. The PID operation control unit is used for outputting a closed-loop control signal after conducting PID operation on the longitudinal opposite position. The ratio electromagnet works in a linear working area under the effect of the closed-loop control signal, outputs the force unrelated to displacement, and acts on the load rod so that the load rod can be in a suspended state and low-frequency vibration isolation can be achieved. The requirement for vibration isolation during high-precision absolute gravity measurement can be met.

The invention discloses an optical multiple-frequency laser interference system for a high-precision absolute gravity meter. The optical multiple-frequency laser interference system comprises a frequency stabilized laser, a collimation and beam expanding mirror, an adjustable reflector, a beam splitter, a reference prism, a faller prism, a horizontal liquid level, a reflecting prism, a diaphragm, a focusing lens and a photoelectric detector, wherein laser is emitted by the frequency stabilized laser, after passing through collimation and beam expanding mirror vertically downwards transmitted after being reflected by the adjustable reflector, and then split into a test light beam vertically downwards transmitted and a reference light beam horizontally transmitted to the right by the beam splitter, wherein the test light beam is shot to the horizontal liquid level after being reflected by the reference prism and the faller prism for many times, then returns according to the original light path after being reflected to join with the reference light beam to generate interference fringes, and the interference fringes pass through the opened diaphragm and are focused on the photoelectric detector by the focusing lens. The invention also discloses an absolute gravity meter adopting the system. According to the optical multiple-frequency laser interference system for the high-precision absolute gravity meter and the application thereof, the test precision can be improved for multiple times, and the direction of the test light beam can be simply and effectively adjusted to ensure that the direction is parallel to the direction of the gravity acceleration.

The invention provides an absolute gravity measurement system and a measurement method. The absolute gravity measurement system comprises a free fall device, a laser interference measurement device and an isolation platform. The free fall device comprises a casing body, a vacuum bin arranged in the casing body, and a power device in transmission connection with the vacuum bin. The power device is used to control the movement of the vacuum bin in the vertical direction. The faller is arranged in the vacuum bin. The bottom of the vacuum bin is provided with a vacuum bin observation window which is used for observing the free fall movement of the faller. The absolute gravity measurement system further comprises a vacuum bin displacement measurement device arranged within the casing body. The vacuum bin displacement measurement device comprises a grating scale which is arranged in the casing body and a reading head which is fixedly arranged on the casing body of the vacuum bin. The absolute gravity measurement system further comprises an air refractive index measurement device which is used for measuring the air refractive index inside the casing body.

The invention discloses a gravity measurement device and method based on an optical trap. The device comprises an optical trap capturing module, a vacuum module, a feedback module and a position detection module, wherein the vacuum module is used for enabling microspheres to be in a high-vacuum environment during gravity testing; the optical trap capturing module is used for capturing the microspheres in the vacuum environment and cooling the microspheres to perform centroid motion; the laser intensity is adjusted to be zero through an acoustic optical modulator (AOM) so as to close the optical trap; at the moment, the microspheres fall freely under the action of gravity, after a short time, the AOM is controlled to open the optical trap again, the microspheres are captured again, the freefalling process of the microspheres is measured through the position detection module, and absolute gravity measurement can be carried out according to the falling process of the microspheres. By repeating the process, continuous measurement of absolute gravity can be realized. According to the invention, free falling of the suspended microspheres is realized by utilizing the optical trap under ahigh vacuum condition so that the absolute gravity of the environment is calibrated, and the device has the advantages of short test time, small size and capability of continuously measuring the absolute gravity.

The invention discloses a high-precision absolution relative gravity measurement instrument driven by optical force. The measurement instrument comprises a first laser, a collimation beam extending system, a reflection mirror, a first beam divider, a second beam divider, a falling body prism, a reference prism, a photoelectric detector, a second laser, a steering lens, a focusing lens and a four-quadrant detector. A hollow photonic crystal fiber light trap system is arranged between the second laser and the steering lens. Micro particles are arranged in the light trap system. According to the invention, high-precision gravity accelerated speed is achieved by use of optical force effects; when the gravity accelerated speed is precisely measured, the measured dynamic range is quite wide; by use of different parts to work, high precision measurement of the absolute gravity accelerated speed can be achieved and real-time measurement of the relative gravity accelerated speed can be achieved; the measurement dynamic range is wide; and the measurement instrument is suitable for aerospace and sailing field.

A prestress type falling body prism release apparatus for an absolute gravity meter includes a vacuum cabin, a support plate, clamps, a falling body prism, prestress springs, a prism tray, a lifting tray, buffer springs, guide rails and a perspective window mirror, wherein the lifting tray is slidably connected with the guide rails. A lower end of each buffer spring is connected with an upper surface of the lifting tray. The guide rails penetrate the prism tray without contact. The prism tray is arranged above the buffer springs. After a process of lifting the falling body prism is completed, a lower end of each prestress spring is in contact with an upper surface of the prism tray, and the prestress springs are compressed and generate push-down prestress on the prism tray. When the falling body prism is released, the prestress separates the falling body prism and the prism tray. According to the apparatus, release time of the falling body prism can be shortened, effects of frictional force, and electromagnetic and electrostatic disturbing force on the falling body prism are small and the apparatus is beneficial to precise measurement of gravity.

The embodiment of the invention relates to gravity measurement, and discloses a method and equipment for airborne gravity measurement. The method for the airborne gravity measurement is applied to anairborne gravity measurement device, and comprises the steps that according to an airborne measurement air route, the position of a to-be-measured point is acquired, and an airplane flies to the to-be-measured point; under the situation that the airplane and the to-be-measured point are in a relative rest state, a test block is released on the to-be-measured point, and displacement data and time data of the test block in vacuum falling body space are detected, wherein the vacuum falling body space is located in the airborne gravity measurement device; according to the displacement data and thetime data, an absolute gravity value of the to-be-measured point is calculated. The method and equipment for the airborne gravity measurement have the advantages that the near-earth airborne gravitycan be measured rapidly and accurately, and the accuracy of the airborne gravity measurement is improved.

The invention provides a method for measuring and calibrating Antarctic ship load capacity. The method comprises the following steps: constructing an absolute gravity reference point of a polar region; calibrating the grid value of the relative gravimeter through a known point method or an inclination method; carrying out gravity joint measurement between a ship gravity chamber and a station areaor wharf absolute gravity datum point; using the gravity joint measurement result of the ship gravity chamber as an absolute gravity value at the position of the ship gravity meter, and realizing thecalibration of polar region ocean ship load capacity measurement by correcting the height of the gravity meter and the sea level. According to the method for measuring and calibrating Antarctic ship load capacity, the problem that the land reference point on the scientific investigation station cannot be directly utilized to perform base point comparison of ship load capacity measurement can be solved.

The invention discloses a mine goaf deformation and stability evaluation method based on Bouguer gravity anomaly. The mine goaf deformation and stability evaluation method comprises a step1, arrangement of relative gravimeter observation points; a step2, arrangement of base points; a step3, erecting of gravimeters and absolute gravimeters; a step 4, acquisition of relative gravity observation values and absolute gravity observation values; a step 5, the acquisition of the deformation amounts of the relative gravity observation points; a step 6, drafting of a relative gravity observation point deflection curve and acquisition of stable deformation amounts. The mine goaf deformation and stability evaluation method is advantageous in that the steps are simple, a design is reasonable, costs are low, and use operation is convenient; by adopting the Bouguer gravity anomaly, the deformation amounts of the mine goaf is monitored, and monitoring results are accurate; the stability of the mine goaf is evaluated according to the deformation amounts of the mine goaf, and the stable deformation amounts of the mine goaf are acquired, and practicability is strong.

The invention discloses a miniaturized absolute gravimeter based on a micro-nano chip, relates to the field of absolute gravity measurement, and aims to overcome the defect that a power system and an optical path system of a traditional absolute gravimeter are complex, reduce the size and the mass of an absolute gravity measurement system and meet the engineering use requirements of miniature gravity measurement. The miniaturized absolute gravimeter based on a micro-nano chip comprises a 980nm laser, an optical fiber isolator, a wavelength division multiplexer, the micro-nano chip, a 1550nm laser, an optical fiber circulator, a photoelectric detector, an A/D converter, an FPGA chip, a single-mode optical fiber, a polystyrene bead, a capillary tube and an electric injector. A stable polystyrene sphere sequence is output through an electric injector, polystyrene spheres are captured and emitted through 980 nm laser, and then the local absolute gravity value is measured through the 1550 nm laser interference effect. Gravity measurement is achieved through combination of the micro-nano chip and the optical fiber optical path, the size and power consumption of the gravimeter are greatly reduced, and the gravimeter can be suitable for absolute gravity measurement application scenes with limited sizes.