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.

Abstract: In an AC magnetic tracker one or more multi-axis field sources, each operating at a different frequency, or frequency set, are detected and tracked in three-dimensional space, even when wireless or otherwise not physically connected to the tracking system. Multiple sources can be tracked simultaneously as they each operate with their own unique detectable set of parameters. The invention not only provides the ability to uniquely identify one or more sources by their frequencies, but also to synchronize with these frequencies in order to measure signals that then allow tracking the position and orientation (P&O) of the source(s). Further, these sources need not be present at the time of system start-up but can come and go while being detected, discriminated and tracked. It also should be noted that application of such systems in multiples with more sensors not synchronized to a source or sources also could be employed to give the reverse appearance of a known source phase and incoherency with the sensors.

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.

Abstract: Techniques for removing distortion in an AC magnetic tracker identify a characteristic frequency in the distortion environment which is then utilized to extract distortion components from the tracker receiver signals so that the corrected position and orientation can be calculated. A multiplicity of alternative techniques for determining this characteristic frequency are disclosed, several of which can be done during operation without interrupting system operation while others can be done off-line. The invention also allows the use of a tuned tracker transmitter since it does not need to operate at multiple frequencies. The invention differs from the prior art by treating an extended conductor characteristic as just another unknown. The position and orientation algorithm solves the 6 unknown coordinates of position and orientation plus the one more unknown—the extended conductor characteristic frequency.

Abstract: A highway safety net for catching and controlling a vehicle travelling towards the opposite direction of traffic comprises netting connected to a lower cable. A first post top is connected to the netting for supporting the netting. A second post top is connected to the first post top. A first stabilizer bar is connected to the lower cable. The first stabilizer bar is connected adjacent to the first post bottom. A second stabilizer bar is connected to the lower cable. The second stabilizer bar is connected adjacent to the second post bottom.

Abstract: A cap-attachable peripheral-viewing mirrors assembly for allowing the users to view all areas about oneself without having to turn one's head which could spook the game animal. The cap-attachable peripheral-viewing mirrors assembly includes a cap having a bill portion; and also includes fasteners being fastenable to the bill portion of the cap; and further includes contortable tentacle-like support members being attachable to the fasteners; and also includes plate members being attached to the contortable tentacle-like support members; and further includes mirrors being attached to the plate members.

Abstract: A retractable cover for recreational vehicle to provide retractable sunshade comprises a support frame connectable to a recreational vehicle roof. A cover spindle is connected to the support frame. A cover first end is windably connected to the cover spindle. A cover arm is rotatably connected to the support frame. The cover arm is connected to the cover second end. Multiple arched truss arms are rotatably connected to the support frame.

Abstract: Methods and apparatus for position/orientation tracking within a bounded volume employ at least one stationary sensor, called a “witness sensor,” having a fixed position and orientation near or within the volume to account for electromagnetic distortion. One or more probe sensors are placed on an object to be tracked within the volume, and the output of each witness sensor is used to compute the parameters of a non-real effective electromagnetic source. The parameters of the effective source are used as inputs to the computation of position and orientation as measured by each probe sensor, as if the object were in the non-distorted electromagnetic field produced by the effective source or sources. In addition to trackers for helmet-mounted displays in aircraft, tank, and armored-vehicle applications, the invention finds utility in any electromagnetic tracking system which might be subject to electromagnetic distortion or interference.

Abstract: Electromagnetic field mapping is accelerated by acquiring data from the surface bounding a volume of interest and solving the boundary value problem (BVP) using Green's function in a preferred embodiment. Instead of measuring electromagnetic field components on a step-by-step basis at each point within a region of interest, only a component of the field, preferably the normal component, is measured on the surface bounding the volume. The use of surface data acquisition, a solution to the BVP using Green's function, and optional error correction based on the treatment of errors as virtual sources, combine to produce a process of defining of the electromagnetic field within the volume that reduces to a few minutes what presently takes days or longer, and sometimes impossible.

Abstract: A method and apparatus for determining the position and orientation of a remote object relative to a reference coordinate frame includes a source having a plurality of field-generating elements for generating electromagnetic fields, a drive for applying, to the generator element, signals that generate a plurality of electromagnetic fields that are distinguishable from one another, a remote sensor having a plurality of field-sensing elements for sensing the fields generated by the source, and a processor for processing the outputs of the sensing elements into remote object position and orientation relative to the source reference coordinate frame. The processor compensates the position and orientation values as a function of displacement of either the field-generating elements from a common center, or the field-sensing elements from a common center, or both.

Abstract: A method and apparatus is provided for determining remote object orientation and position with an electromagnetic coupling. A plurality of radiating antennas are provided for radiating electromagnetic energy. Each of the radiating antennas have independent components for defining a source reference coordinate frame. A transmitter is provided for applying electrical signals to the radiating antennas for generating a plurality of electromagnetic fields. The signals are multiplexed so that the fields are distinguishable from one another. A plurality of receiving antennas are disposed on a remote object for receiving the transmitted electromagnetic fields. The receiving antennas have a plurality of independent components for detecting the transmitted electromagnetic fields and defining a sensor reference coordinate frame.