# US 2009/0260433 A1 · Actuatory and Gravity Gradiometer > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2009/0260433 A1 - Document ID: US20090260433A1 - Status: Published application - Kind: A1 - Application number: 11/722,058 - Filed: 2006-08-31 - Published: 2009-10-22 - Earliest claimed: 2005-10-06 - Assignees: Technological Resources Pty. Limited - Inventors: Frank Joachim Van Kann; John Winterflood - Web page: https://patentgrep.com/patent/US20090260433A1 ## CPC - G01V 7/16: specially adapted for use on moving platforms, e.g. ship, aircraft - G01V: GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS (means for indicating the location of accidentally buried, e.g. snow-buried, persons A63B29/02) ## Abstract A gravity gradiometer is disclosed which has a sensor in the form of bars (41 and 42) which are supported on a mounting (5) which has a first mount section (10) and a second mount section (20). A first flexure web (33) pivotally couples the first and second mount sections about a first axis. The second mount has a first part (25), a second part (26) and a third part (27). The parts (25 and 26) are connected by a second flexure web (37) and the parts (26 and 27) are connected by a third flexure web (35). The bars (41 and 42) are located in housings (45 and 47) and form a monolithic structure with the housings (45 and 47) respectively. The housings (45 and 47) are connected to opposite sides of the second mount section 20. The bars (41 and 42) are connected to their respective housings by flexure webs (59). Transducers (71) 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 stabilise the mount. The actuator comprises a hollow disc housing (310) which defines a chamber (312). A coil plate (313) is located in the chamber (312) and supports windings (W1 and W2). A tube (330) supports a hollow rod (328) to minimise flux leakage from the windings (W1 and W2). Lead wires for the windings pass through the rod (328) to the windings (W1 and W2) mounted on the support plate (313). ## Claims ### Claim 1 A gravity gradiometer for measuring components of the gravitational gradient tensor, comprising: a sensor for measuring the components of the gravitational gradient tensor; a mount for supporting the sensor, the mount being for providing movement about three orthogonal axes; a plurality of actuators for moving the mount about the three axes to stabilise.orientation of the mount during use of the gradiometer; each actuator comprising a first housing part for coupling to one of the mounting and a fixed portion of the gradiometer; a moveable member for connection to the other of the mounting and the fixed portion; at least one coil; a reaction member carried by one of the housing part and the moveable member so that when the coil receives a signal, the reaction member is moved relative to the coil to in turn move the moveable member relative to the housing part and therefore the mounting relative to the fixed portion; and wherein the actuator has an elongate passage for minimising leakage of magnetic flux from the actuator. ### Claim 2 (depends on 1) The gravity gradiometer of claim 1 wherein linear and angular accelerometers are provided for detecting movement of the sensor due to angular accelerations for producing signals to counteract error induced by those accelerations. ### Claim 3 (depends on 1) The gravity gradiometer of claim 1 wherein the actuators counteract error produced by angular disturbance of the sensor. ### Claim 4 (depends on 1) The gravity gradiometer of claim 1 wherein the actuators reduce angular motion to further reduce errors produced due to centrifugal forces or angular acceleration. ### Claim 5 An actuator for producing a force to adjust the position of one component relative to another component, comprising: a first part for coupling to one of the said one component and another component; a moveable member for connection to the other of the said one component and another component; at least one coil carried by one of the first part and the moveable member so that when the coil receives a signal, the moveable member is moved relative to the first part to in turn move the first component relative to the second component; and wherein the actuator has an elongate passage for minimising leakage of magnetic flux from the actuator. ### Claim 6 (depends on 5) The actuator of claim 5 wherein the moveable member has the passage. ### Claim 7 (depends on 5) The actuator of claim 5 wherein the passage is in the form of a tube. ### Claim 8 (depends on 7) The actuator of claim 7 wherein the tube has a length to maximum width ratio of about 10:1. ### Claim 9 (depends on 7) The actuator of claim 7 wherein the tube is substantially circular in cross-section. ### Claim 10 (depends on 5) The actuator of claim 5 wherein the first part has a rod located in the passage for receiving leads for supplying current to the coil to energize the coil. ### Claim 11 (depends on 5) The actuator of claim 5 wherein the coil is a pancake coil. ### Claim 12 (depends on 7) The actuator of claim 7 wherein the moveable part is a hollow disc housing which supports the tube. ### Claim 13 (depends on 12) The actuator of claim 12 wherein the first part is a disc plate located in the hollow disc housing, the disc plate supporting the rod within the tube, the coil being located on the disc plate, the rod being connected to said one component, and the disc housing being connected to the other component.