A magnetic sensor device comprises a substrate. A first magnetic sensor, a second magnetic sensor, and one or more inductors are disposed over the substrate and are controlled by a magnetic sensor controller having a control circuit. The control circuit is adapted for controlling the first magnetic sensor to measure magnetic fields under presence of a first set of magnetic fields, and for controlling the second magnetic sensor to measure magnetic fields under presence of a second set of magnetic fields generated by the inductors. The control circuit calculates a relative sensitivity matching value that converts magnetic field values measured by the second magnetic sensor to a comparable magnetic field value measured by the first magnetic sensor or vice versa. The control circuit is further adapted for correcting a measurement by the second magnetic sensor using the relative sensitivity matching value to produce a corrected measurement, and for calculating a magnetic field gradient by combining a measurement by the first magnetic sensor with the corrected measurement.

A structure for magnetic flux sensor conditioning is presented which partitions an input analog signal of unknown integrity into two: susceptible and insusceptible. The structure scrutinizes the susceptible signal partition, in view of additional guard sensor information, through a mixed-signal processing side-chain that employs a non-invasive physical magnetic attack detection algorithm. The side-chain either validates, or replaces with a best estimate, the susceptible signal partition, depending upon the absence or presence of attack, respectively. The structure finally recombines the scrutinized susceptible signal partition with the insusceptible signal partition. The result is an analog magnetic flux sensor signal that is robust against skillful, surreptitious, spoofing attacks. If unmitigated, such attacks may induce catastrophic consequences into systems relying upon the magnetic flux sensor.

The invention relates to an apparatus as well as a method for calibrating a magnetic sensor system including at least one magnetic field source and one magnetic field sensor arrangement with several individual magnetic field sensors. Here, a plurality of individual measurements is performed, wherein each individual measurement provides a number of measurement values depending on the number of the individual magnetic field sensors. The magnetic field of the magnetic field source is varied at the location of the magnetic field sensor arrangement between two successive individual measurements. Based on the measurement values and by applying an optimization or estimation method, one or several magnetic field sensor-specific parameters and/or magnetic field source-specific parameters are determined, which are used as correction values for calibrating the magnetic sensor system. According to the invention, a magnetic field source is used that generates an inhomogeneous magnetic field.

A method for estimating an angular deviation between a reference axis of a magnetic object and a magnetic axis co-linear to a magnetic moment of the magnetic object, including: a) positioning the magnetic object facing at least one magnetometer; b) rotating the magnetic object about the reference axis; c) measuring, during the rotating, the magnetic field, using the magnetomenter; and d) estimating the angular deviation from the magnetic field measurements.

A calibration device comprising: a plurality of magnetic sensors positioned at the calibration device, the plurality of magnetic sensors defining a space; a controller configured to be positioned in the space defined by the plurality of magnetic sensors, wherein the controller includes a magnetic transmitter; and one or more processors configured to: cause the magnetic transmitter to generate magnetic fields; receive signals from the plurality of magnetic sensors that are based on characteristics of the magnetic fields received at the plurality of magnetic sensors; calculate, based on the signals received from the plurality of magnetic sensors, positions and orientations of the plurality of magnetic sensors relative to a position and orientation of the magnetic transmitter; and determine whether the calculated positions and orientations of the plurality of magnetic sensors are within one or more threshold limits of known positions and orientations of the plurality of magnetic sensors.

Methods and systems estimate calibration errors of magnetic sensor measurements collected at mobile devices. Each measurement is associated with a location of one of the mobile devices and has a calibration error. Data from the sensor measurements is partitioned into sets. Each set is associated with a respective calibration error associated with the measurements that generated the data in the set. Pairs of data items are identified, where each pair includes a data item from a first of the sets corresponding to a measurement, associated with a first location, that generated the data in the first set, and a data item from a second of the sets corresponding to a measurement, associated with a second location that is approximately the same as the first location, that generated the data in the first set. The calibration error associated with each of the sets is estimated based in part on the pairs.

A mobile robot includes a body movable over a surface within an environment, a calibration coil carried on the body and configured to produce a calibration magnetic field, a sensor circuit carried on the body and responsive to the calibration magnetic field, and a controller carried on the body and in communication with the sensor circuit. The sensor circuit is configured to generate calibration signals based on the calibration magnetic field. The controller is configured to calibrate the sensor circuit as a function of the calibration signals, thereby resulting in a calibrated sensor circuit configured to detect a transmitter magnetic field within the environment and to generate detection signals based on the transmitter magnetic field. The controller is configured to estimate a pose of the mobile robot as a function of the detection signals.

Methods and apparatuses are provided, in which a magnetic field is measured using a coil in a first operating mode and a magnetic field is generated using the coil in a second operating mode in order to test a further magnetic field sensor.

Disclosed is a MTJ sensing circuit for measuring an external magnetic field and including a plurality of MTJ sensor elements connected in a bridge configuration, the MTJ sensing circuit having an input for inputting a bias voltage and generating an output voltage proportional to the external magnetic field multiplied by the bias voltage and a gain sensitivity of the MTJ sensing circuit, wherein the gain sensitivity and the output voltage vary with temperature; the MTJ sensing circuit further including a temperature compensation circuit configured to provide a modulated bias voltage that varies as a function of temperature over a temperature range, such that the output voltage is substantially constant as a function of temperature. Also disclosed is a method for compensating the output voltage for temperature.

A magnetic field sensor configured to sense an angle of a magnetic field associated with a rotatable target includes a first magnetic field sensing structure configured to generate a first signal indicative of the magnetic field and a second magnetic field sensing structure configured to generate a second signal indicative of the magnetic field, wherein the first and second magnetic field sensing structures are configured to detect quadrature components of the magnetic field. A controller responsive to the first and second signals includes an angle tracking observer having a sine block and a cosine block operatively coupled to compute the angular position of the target using a control loop based in part on a non-orthogonality error term and a magnitude calculator that uses the sine block and the cosine block to compute a magnitude of the magnetic field.