Abstract: An apparatus and method for determining position and orientation (PnO) of an object within an environment and for automatically determining a hemisphere of the object relative to a source location using an electromagnetic tracking system and a non-magnetic tracking device. The method involves seeding two candidate PnO solutions, one in each hemisphere, based on initial data from the magnetic tracker. Then, as the sensor moves within the tracking volume, both the magnetic tracker and the non-magnetic tracking device are used to track changes in each of the candidate PnO solutions and to determine a correct one of the candidate PnO solutions.

Abstract: A safety system for a machine having a danger zone includes an induction coil having one or more turns extending along the periphery of a part of a worker's body as, for example, extending alone the fingers of a glove worn by the worker. A drive circuit applies a time-varying current having an identifiable characteristic such as the frequency of an alternating current. A magnetic field having the characteristic of the time-varying current is induced in an omnidirectional magnetic field sensor mounted adjacent the danger zone. The magnitude of this field is monitored. When the magnitude exceeds a threshold, a warning signal is issued and protective action may be taken, such as stopping or reversing the machine.

Abstract: A safety system for a machine having a danger zone includes an induction coil having one or more turns extending along the periphery of a part of a worker's body as, for example, extending alone the fingers of a glove worn by the worker. A drive circuit applies a time-varying current having an identifiable characteristic such as the frequency of an alternating current. A magnetic field having the characteristic of the time-varying current is induced in an omnidirectional magnetic field sensor mounted adjacent the danger zone. The magnitude of this field is monitored. When the magnitude exceeds a threshold, a warning signal is issued and protective action may be taken, such as stopping or reversing the machine.

Abstract: A method and system for magnetic locating resolves phase ambiguity. The system uses time-division multiplexed magnetic fields emitted from plural transmit coils. The magnetic fields are alternating fields at a carrier frequency, and the fields emitted from different coils in different transmit intervals have known phase relationship with one another as, for example where the alternating fields are coherent with one another. A receiver uses a plurality of sensor coils and derives plural components using the common phase reference or plural phase reference times having a known relationship. If the determinant of a matrix of the components has a first value, the phase information in the components is correct, and position and orientation are derived from the components. If the determinant has a second value, the phase information in the components is incorrect.

Abstract: Plural transmitter coils of a magnetic locating system are driven with widely-separated main frequencies. One of the transmitter coils is also driven with a marker frequency close to the main frequency applied to that coil. The receiver determines a phase relationship with the transmitter based on the main and marker frequencies, so that the receiver does not suffer from phase ambiguity. The main and marker frequencies may interfere with one another, and the receiver may correct for such interference based on known characteristics of the signals at the main and marker frequencies.