669 results about "Earth's magnetic field" patented technology

Apparatus and methods are disclosed for reducing the potentially harmful effects of electromagnetic waves on an implantable medical device. In one embodiment of the present invention, an implantable medical system comprising a dual threshold magnetic sensor capable of detecting an elevated magnetic field is disclosed. The sensor can comprise a solid-state sensor capable of detecting a static magnetic field in excess of about 1500 Gauss. The magnetic sensor can be operatively coupled to electronics that are capable of altering the operation of the system upon detection of an elevated magnetic field by the magnetic sensor.

A tilt-compensated electronic compass can be realized by calculating rather than measuring Earth's magnetic field component Z in a direction orthogonal to the two measurement axes of a 2-axis magnetic sensor. The orthogonal component Z can be calculated using a stored value for the Earth's magnetic field strength applicable over a wide geographic region. The calculation also requires using measured field values from the 2-axis sensor. Once Z is known, and using input from a 2-axis tilt sensor, compensated orthogonal components X and Y can be calculated by mathematically rotating the measured field strength values from a tilted 2-axis sensor back to the local horizontal plane. Thus, a very flat and compact tilt-compensated electronic compass is possible.

An electronic compass system includes a magnetic sensor circuit having at least two sensing elements for sensing perpendicular components of the Earth's magnetic field vector. A processing circuit is coupled to the sensor circuit to filter, process, and compute a heading. The processing circuit further selects an approximating geometric pattern, such as a sphere, ellipsoid, ellipse, or circle, determines an error metric of the data points relative to the approximating pattern, adjusts the pattern to minimize the error, thereby obtaining a best fit pattern. The best fit pattern is then used to calculate the heading for each successive sensor reading provided that the noise level is not noisy and until a new best fit pattern is identified. The electronic compass system is particularly well suited for implementation in a vehicle rearview mirror assembly.

A micro integrated Global Positioning System (GPS)/Inertial Measurement Unit (IMU) System, which is adapted to apply to output signals proportional to rotation and translational motion of a carrier and GPS measurements of the carrier, respectively from angular rate sensors, acceleration sensors, and GPS chipset, is employed with MEMS angular rate and acceleration sensors and GPS chipset. Compared with a conventional IMU/GPS system, the system of the present invention uses an integrated processing scheme by means of digital closed loop control of the dither driver signals for MEMS angular rate sensors, a feedforward open-loop signal processing scheme of the IMU, digital temperature control and compensation, the earth's magnetic field-based heading damping, robust error estimator, and compact sensor and circuit architecture and dramatically shrinks the size of mechanical and electronic hardware and power consumption, meanwhile, obtains highly accurate motion measurements.

An electronic compass system includes a magnetic sensor circuit having at least two sensing elements for sensing perpendicular components of the Earth's magnetic field vector. A processing circuit is coupled to the sensor circuit to filter, process, and compute a heading. The processing circuit may determine whether too much noise is present in the output signals received from said magnetic sensor circuit as a function of the relative strength of the Earth's magnetic field vector. The magnetic sensor circuit may include three magnetic field sensing elements contained in a common integrated package having a plurality of leads extending therefrom for mounting to a circuit board. The sensing elements need not be perpendicular to each other or parallel or perpendicular with the circuit board. The electronic compass system is particularly well suited for implementation in a vehicle rearview mirror assembly.

A compass compensation system is provided for automatically and continuously calibrating an electronic compass for a vehicle, without requiring an initial manual calibration or preset of the vehicle magnetic signature. The system initially adjusts a two axis sensor of the compass in response to a sampling of at least one initial data point. The system further calibrates the compass by sampling data points that are substantially opposite to one another on a plot of a magnetic field and averaging an ordinate of the data points to determine a respective zero value for the Earth magnetic field. The system also identifies a change in magnetic signature and adjusts the sensor assembly.

A mirror or other reflecting surface is used for collecting and reflecting incident solar radiation. The mirror is supported for independent motion about a pair of axes. An accelerometer generates signals representative of an amount and direction of motion of the mirror about each of the axes. Motors or other drive mechanisms independently drive the mirror about each of the axes. A tracking device provides information about the current position of the Sun. A control is connected to the accelerometer, the motors and the tracking device for maintaining a predetermined optimum orientation of the mirror as the Sun moves across the sky. Position sensors that sense the position of the mirror relative to the earth's magnetic field may also be employed.

A wellbore tool for locating a target wellbore containing a conductive member from a second wellbore and directing the trajectory of the second wellbore relative to the target wellbore includes an electric current driver having an insulated gap; a three-axis magnetometer positioned within a non-magnetic housing that is disposed within a non-magnetic tubular, the three-axis magnetometer positioned below the electric current driver; a drill bit positioned below the three-axis magnetometer; a hollow tubular connected between the electric current driver and the three-axis magnetometer; and a measurement-while-drilling tool. The current driver generates an electric current across the gap to the portion of the tool below the insulated gap. In a method a current is generated across the insulated gap to the portion of the tool below the insulated gap to the conductive material in the target wellbore returning to a portion of the bottom hole assembly above the insulated gap thereby producing a target magnetic field. Measuring the target magnetic field at the bottom hole assembly and the earth's magnetic field; and determining the position of the second wellbore relative to the target wellbore. Then steering the bottom hole assembly to drill the second wellbore along a trajectory relative to the target wellbore.

Described herein, in certain embodiments, are devices and methods for modulating the electrical activity of a brain in a targeted manner using a weak magnetic field, generally field with a strength of less than about 100 Gauss. The magnetic field is varied over time in a periodic manner, generally with a frequency tuned to specifically affect one of the intrinsic frequencies of the brain, optionally the alpha frequency. The “Low Field Magnetic Stimulation” devices and methods described herein modulate the electrical activity of a brain without requiring medication. Methods and devices described herein gently “tune” the brain and affect mood, focus, and cognition of human subjects.

PCT No. PCT/EP97/00583 Sec. 371 Date Nov. 10, 1997 Sec. 102(e) Date Nov. 10, 1997 PCT Filed Feb. 10, 1997 PCT Pub. No. WO97/34125 PCT Pub. Date Sep. 18, 1997A method for determining the direction of the Earth's magnetic field, which may be interfered with by magnetic materials built into equipment and by electric currents, using an electronic magnetic compass which contains three magnetic field sensors and two devices for measuring inclination is provided. The electronic magnetic compass is arranged in N different spatial positions, in each of these N positions, the inclination sensor signals and the magnetic field sensor signals being measured and inclination values and magnetic field values being determined from these signals. On the basis of these inclination values and magnetic field values, the magnitude of the Earth's magnetic field vector is determined using the vector equationconst=bg=bEsin(i)=gTL(bE)=gTm(bmes-bo)with N having to be at least equal to the number of parameters to be determined in the vector equation.

There is provided a solution comprising detecting that a positioning device is within a predetermined control area associated with a building, acquiring a first sequence of magnetic field measurements carried out by the positioning device, wherein the first sequence represents at least one of the magnitude and the direction of Earth's magnetic field; determining that an operational environment of the positioning de-vice has changed between an indoor environment and an outdoor environment when a at least one predetermined criterion with respect to the first sequence is met; and causing actuation of a predetermined software function in or with respect to the positioning device when the operational environment of the positioning device has changed.

The present invention provides a radiotherapy treatment apparatus that includes a treatment beam, a magnetic field disposed parallel collinear to the treatment beam, and a target that is disposed along the treatment beam. The treatment beam can be a charged particle beam, a proton beam, an electron beam, or a linear accelerator (Linac) beam. The magnetic field is from a magnetic resonance imager (MRI), a megavolt x-ray imager, or a kilovolt x-ray imager and is disposed to operate in coordination with operation of the treatment beam and to narrow the beam. The tumor is disposed to rotate with respect to the treatment beam and the magnetic field, or the treatment beam and the magnetic field are disposed to rotate up to 360° with respect to the target when mounted to a ring gantry. The apparatus can include a rotation angle dependent shim disposed to account for Earth's magnetic field.

A method for characterizing distortions in the earth's magnetic field caused by a vehicle having a magnetometer affixed therein is described. The method includes repeatedly measuring the distorted magnetic field utilizing the magnetometer and obtaining a three-dimensional orientation of the vehicle axes with respect to the earth at a time of each magnetometer measurement. The method also includes receiving undistorted earth magnetic field data for the vicinity of the vehicle relative to the earth at the time of each magnetometer measurement and characterizing distortions caused by one or more of the vehicle and magnetometer errors utilizing the magnetic field measurements, the orientations of the vehicle, and the undistorted earth magnetic field data.

There is provided an apparatus, wherein the apparatus is caused to acquire a location estimate of a positioning device that is to determine its location inside a building, wherein the location estimate is acquired on the basis of an indoor non-magnetic field based location discovery system; access an indoor Earth's magnetic field, EMF, map of plurality of buildings, wherein the indoor EMF map represents at least one of magnitude and direction of the Earth's magnetic field affected by the local structures of a corresponding building; and select a part of the indoor EMF map on the basis of the location estimate of the positioning device, wherein the selected part of the indoor magnetic field map includes the indoor EMF map for the area in which the positioning device currently is.

A stylus that operates utilizing magnetic fields, wherein a permanent magnet is disposed within a passive stylus that is detectable by a plurality of magnetic sensors that remove the magnetic field of the stylus from the earth's relative magnetic field to thereby obtain vectors that are used in a triangulation equation to determine the location of the stylus in two or three dimensions, depending upon the number of magnetic sensors that are used, wherein one set of magnetic sensors can be used as a reference for earth's magnetic field, and wherein each of the magnetic sensors includes a polarizing coil to change direction of sensitivity, a null coil and a flipping coil.

There is provided an apparatus caused to acquire information indicating a measured magnetic field vector and information relating to an uncertainty measure of the measured magnetic field vector in at least one known location inside the building, wherein the indicated magnetic field vector represents magnitude and direction of the earth's magnetic field affected by the local structures of the building, and to generate the indoor magnetic field map for at least part of the building on the basis of at least the acquired information and the floor plan.

Method and apparatus of integrating a three-axis magnetometer and a three-axis accelerometer to provide attitude and heading, calibrated magnetometer and accelerometer data, and angular rate, while removing sensor error sources over time and temperature and to compensate for hard and soft iron distortions of the Earth magnetic field. Filtered accelerometer data are corrected to account for various error sources. The magnetic heading is calculated from a horizontal magnetic field vector transformed from three dimensional Earth's magnetic field vector by using quasi-static roll and pitch angles from the filtered accelerometer data. A first Kalman filter estimates the state vector, based on the principle that the magnitude of local Earth's magnetic field vector is constant, to form hard and soft iron correction matrices. A second Kalman filter estimates a correction matrix of coupled remaining soft iron and the misalignment of the magnetometer and the accelerometer, as the dot product of local Earth's magnetic field vector and a corrected gravitational acceleration vector, at a quasi-static position, is constant. The three dimensional Earth's magnetic field vector is received by removing the hard and soft irons through the soft iron and hard iron correction matrixes.

The present invention relates to an autonomous underwater vehicle (“AUV”) for monitoring underwater fluid currents by detecting electrical currents induced by the flow of a conductive liquid through the Earth's magnetic field. More particularly, the present invention relates to the gathering of data related to underwater fluid currents and the control of AUV motion during data gathering.