Technological Resources Pty. Limited

Other

Frank Joachim Van Kann

John Winterflood

Alexey Vladimirovich Veryaskin

Anthony Gordon Mann

A capacitance sensing assembly is provided. The capacitance sensing assembly includes an op-amp arranged with four complex impedance circuits and a sensing capacitor connected to the fourth complex impedance circuit and ground; or to the non-inverting input of the op-amp, the fourth complex impedance circuit, ground and the second terminal of the fourth complex impedance circuit, wherein the fourth complex impedance circuit is connected in parallel to the sensing capacitor. The complex impedance circuits are configured to increase a gradient of a phase to frequency response curve of the capacitance sensing assembly relative to that of an all-pass filter with a second electrode of a capacitor connected to the non-inverting input of the op-amp and the ground without the fourth complex impedance circuit.

Capacitance sensing method and assembly

The present disclosure provides a gravity gradiometer that comprises a detector for detecting a gravity gradient. The detector comprises at least one movable sensing element and that is arranged to generate a signal in response to a change in gravity gradient. The gravity gradiometer also comprises a support structure for supporting the detector in an aircraft and a component that is arranged to reduce transmission of an aircraft acceleration to the detector. The at least one movable sensing element and the support structure together are arranged to reduce an influence of the aircraft acceleration on the signal by a factor of at least 10when the gravity gradiometer is airborne and exposed to the aircraft acceleration.

Gravity gradiometer

The present disclosure provides a gravity gradiometer for detecting a gravity gradient. The gravity gradiometer comprises at least two sensor masses that are pivotable about respective axes and each experience a change in torque in response to a change in gravity gradient whereby the at least two sensor masses move relative to each other in response to the change in gravity gradient and wherein a signal indicative of the gravity gradient is generated in response to the relative movement of the at least two sensor masses. Further, the gravity gradiometer comprises an acceleration sensor for sensing an acceleration associated with an external acceleration applied to the gravity gradiometer. The gravity gradiometer also comprises an actuator for generating an adjustment force that is dependent on an acceleration sensed by the acceleration sensor. The adjustment force is also dependent on a mechanical response parameter associated with at least one of the at least two sensor masses. The adjustment force is applied such that a difference between the magnitudes of the torques experienced by the at least two sensor masses in response to the change in gravity gradient is reduced.

Detector for detecting a gravity gradient

A gravity gradiometer is disclosed which has a sensor in the form of bars (and) which are supported on a mounting () which has a first mount section () and a second mount section (). A first flexure web () pivotally couples the first and second mount sections about a first axis. The second mount has a first part (), a second part () and a third part (). The parts (and) are connected by a second flexure web () and the parts (and) are connected by a third flexure web (). The bars (and) are located in housings (and) and form a monolithic structure with the housings (and) respectively. The housings (and) are connected to opposite sides of the second mount section. The bars (and) are connected to their respective housings by flexure webs (). Transducers () are located in proximity to the bars for detecting movement of the bars to in turn enable the gravitational gradient tensor to be measured.

The present invention provides a method of tuning properties of a gravity gradiometer for measuring components of the gravity gradient tensor. The gravity gradiometer comprises a pair of first and second transversely arranged sensor masses that are arranged for movement about an axis and relative to each other in response to a gravity gradient. The gravity gradiometer further comprises first and second capacitors for sensing and influencing the movement of the first and second sensor masses. The method comprising applying a bias voltage to at least one of the capacitors for generating an electrostatic force which acts on one of the sensor masses and thereby influences the movement of that sensor mass.

A gravity gradiometer is disclosed which has a sensor in the form of bars (and) which are supported on a mounting () which has a first mount section () and a second mount section (). A first flexure web () pivotally couples the first and second mount sections about a first axis. The second mount has a first part (), a second part () and a third part (). The parts (and) are connected by a second flexure web () and the parts (and) are connected by a third flexure web (). The bars (and) are located in housings (and) and form a monolithic structure with the housings (and) respectively. The housings (and) are connected to opposite sides of the second mount section. The bars (and) are connected to their respective housings by flexure webs (). Transducers () are located in proximity to the bars for detecting movement of the bars to in turn enable the gravitational gradient tensor to be measured. The sensor masses not only serve to provide measurements of the gravity gradient tensor but also provide signals indicative of angular movement of the mounting and therefore form one of a plurality of angular accelerometers for detecting angular movement so that control signals can be generated to stabilize the mounting ().

A gravity gradiometer is disclosed which has a sensor in the form of bars (and) which are supported on a mounting () which has a first mount section () and a second mount section (). A first flexure web () pivotally couples the first and second mount sections about a first axis. The second mount has a first part (), a second part () and a third part (). The parts (and) are connected by a second flexure web () and the parts (and) are connected by a third flexure web (). The bars (and) are located in housings (and) and form a monolithic structure with the housings (and) respectively. The housings (and) are connected to opposite sides of the second mount section. The bars (and) are connected to their respective housings by flexure webs (). Transducers () are located in proximity to the bars for detecting movement of the bars to in turn enable the gravitational gradient tensor to be measured. The first mount section () has cut-outs () and the second mount section () has lugs () which pass through the cut-outs for connecting the first and second mount sections (and) in a Dewar ().

A gravity gradiometer is disclosed which has a sensor in the form of bars (and) which are supported on a mounting () which has a first mount section () and a second mount section (). A first flexure web () pivotally couples the first and second mount sections about a first axis. The second mount has a first part (), a second part () and a third part (). The parts (and) are connected by a second flexure web () and the parts (and) are connected by a third flexure web (). The bars (and) are located in housings (and) and form a monolithic structure with the housings (and) respectively. The housings (and) are connected to opposite sides of the second mount section. The bars (and) are connected to their respective housings by flexure webs (). Transducers () are located in proximity to the bars for detecting movement of the bars to in turn enable the gravitational gradient tensor to be measured. First and second feedback controllers are provided for monitoring disturbances of an external platform and an internal platform which mount the gradiometer for producing forces to stabilise the sensor.

A gravity gradiometer is described which comprises a pair of sensor bars arranged in housings. Transducers are arranged adjacent the bars for measuring movement of the bars in response to the gravity gradient tensor. At least one of the transducers has a sensing coil and a capacitor plate having a concentric arrangement with the sensing coil for providing one plate of a capacitor used in a balancing circuit for measuring the balance of the sensor mass.

A gravity gradiometer is disclosed which has a sensor in the form of bars (and) which are supported on a mounting () which has a first mount section () and a second mount section (). A first flexure web () pivotally couples the first and second mount sections about a first axis. The second mount has a first part (), a second part () and a third part (). The parts (and) are connected by a second flexure web () and the parts (and) are connected by a third flexure web (). The bars (and) are located in housings (and) and form a monolithic structure with the housings (and) respectively. The housings (and) are connected to opposite sides of the second mount sectionThe bars (and) are connected to their respective housings by flexure webs (). Transducers () are located in proximity to the bars for detecting movement of the bars to in turn enable the gravitational gradient tensor to be measured. An actuator is provided for moving the mount to stabilize the mount. The actuator comprises a hollow disc housing () which defines a chamber (). A coil plate () is located in the chamber () and supports windings (Wand W). A tube () supports a hollow rod () to minimize flux leakage from the windings (Wand W). Lead wires for the windings pass through the rod () to the windings (Wand W) mounted on the support plate ().

Actuatory and gravity gradiometer

A gravity gradiometer and method for forming a pivot flexure web for a gradiometer is disclosed. The gradiometer has measurement barssupported in housingsandand transducersfor measuring movement of the bars to provide an indication of the gravity gradient tensor. The barsare mounted on flexure webs. The webs are formed in separate elements to the housing and bars.

A gravity gradiometer is disclosed which has a sensor in the form of bars (and) which are supported on a mounting () which has a first mount section () and a second mount section (). A first flexure web () pivotally couples the first and second mount sections about a first axis. The second mount has a first part (), a second part () and a third part (). The parts (and) are connected by a second flexure web () and the parts (and) are connected by a third flexure web (). The bars (and) are located in housings (and) and form a monolithic structure with the housings (and) respectively. The housings (and) are connected to opposite sides of the second mount section. The bars (and) are connected to their respective housings by flexure webs (). Transducers () are located in proximity to the bars for detecting movement of the bars to in turn enable the gravitational gradient tensor to be measured. A calibration sensor is provided for sensing whether the masses are balanced at room temperature so the balance of the masses can be adjusted by adjustable screws to balance the masses for cryogenic operation of the gradiometer. The calibration sensor comprises a resonant circuit () and an oscillator (). The resonant circuit includes a capacitor () which is formed by part of the sensor mass and a space plate ().

The present invention provides a gravity gradiometer for measuring components of the gravity gradient tensor. The gravity gradiometer includes at least one sensor mass for movement in response to a gravity gradient and a sensor and actuator unit for generating an electrical signal in response to the movement of the at least one sensor mass and for influencing the movement of the at least one sensor mass. The gravity gradiometer also includes an electronic circuit for simulating an impedance. The electrical circuit is arranged for amplifying the electrical signal received from the sensor and actuator unit and for directing an actuating signal to the sensor and actuator unit. The electronic circuit includes a differential amplifiers having first and second amplifier input terminals and an amplifier output terminal and impedances ZZZat least one of the impedances have an imaginary impedance component.

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Nedlands, Australia

Frank Joachim Van Kann