256 results about "Coil array" patented technology

The invention provides an intelligent eddy current nondestructive testing method and system based on a flexible GMR sensor array, and relates to the technical field of nondestructive testing. According to the invention, a GMR sensor array and a micro excitation coil array are integrated on a flexible substrate, and synchronous acquisition under multi-frequency and multi-phase excitation is realized by establishing a probe-workpiece unified space coordinate system and a time synchronization reference; performing temperature drift compensation, attitude correction and gap normalization processing on the original response tensor to generate a corrected response tensor; the intelligent inversion model based on the prior constraint of the electromagnetic field jointly identifies the conductivity, the thickness and the crack parameters, and outputs a defect parameter map and a confidence map; and a detection report containing the position, the size, the depth and the confidence coefficient is generated through spatial clustering and connectivity analysis, so that high-sensitivity and high-reliability nondestructive detection under a complex curved surface structure is realized.

The invention belongs to the technical field of magnetic particle imaging, particularly relates to a magnetic particle imaging system and method based on a flexible receiving coil array, and aims to solve the problems that an existing rigid receiving coil is poor in biological surface adaptability and low in signal-to-noise ratio for micro geometric texture imaging. According to the structure, a receiving coil array adheres to the surface of an object to be measured, the receiving coil array and a compensation coil array are distributed on the two sides of a flexible substrate, the receiving coil array is used for receiving magnetic nanoparticle signals, and the partitioned small compensation coil array is used for conducting feed-through interference and electromagnetic interference compensation on a receiving coil; the reconstruction method comprises the following steps: sequentially carrying out Fourier transform on the collected receiving signals, extracting in-phase third harmonics and superposing to obtain processed signals, interpolating to construct a sinogram for Cartesian coordinate distribution, and reconstructing the three-dimensional particle concentration distribution of a measured object by a filtering back projection method. A flexible receiving coil array strategy is adopted, an adaptive reconstruction method is provided, and the imaging signal-to-noise ratio is improved.

The invention relates to the technical field of geophysical exploration equipment, and particularly discloses a double-top umbrella type multi-angle adjustable transient electromagnetic transmitting coil array detection device which comprises a main supporting system, a framework supporting system, a coil system, a multi-angle adjusting mechanism and a rapid storage system. The device has the beneficial effects that accurate adjustment in a continuous angle range is realized, and the adaptability of the device to different exploration environments is improved; a double-coil system design is adopted, so that two typical working modes are realized; in structural design, a double-top umbrella type folding structure is combined with a light-weight material, so that the weight of equipment is reduced. According to the device, conversion of multiple detection modes is achieved, traditional multiple fixed angle devices are replaced, the equipment investment cost is reduced, and the equipment operation efficiency is improved.

The invention discloses a dynamic electromagnetic shielding method for a complex electromagnetic environment and a shielding device thereof, and the method comprises the steps: obtaining real-time voltage data in the complex electromagnetic environment, carrying out the voltage feature analysis, outputting a feature vector of a real-time voltage signal, and analyzing the type of an interference source of a current electric field according to the feature vector, performing interference trend time sequence prediction processing on the feature vector through a pre-trained LSTM model according to the interference source type to obtain a time domain voltage value and a phase deviation value, and performing composite loss coefficient calculation on the time domain voltage value and the phase deviation value to obtain a composite loss coefficient; and performing reverse offset signal synthesis processing on the voltage interference signal according to the calculated composite loss coefficient, performing coil dynamic activation processing on a preset multi-coil array according to the synthesized reverse offset signal, generating a directional offset magnetic field corresponding to the real-time electromagnetic interference, and performing electromagnetic offset shielding on the current electromagnetic interference. According to the invention, transient interference can be responded in time, and the electromagnetic shielding effectiveness can be improved.

The invention discloses a distribution network area emergency insurance supply method and system based on vehicle network interaction, and relates to the technical field of distribution network area emergency insurance supply, and the method comprises the following steps: obtaining a distribution network area fault position and electric vehicle distribution data, and constructing a vehicle scheduling instruction set; driving the electric vehicle to move to a target area according to the scheduling instruction set, and transmitting magnetic field disturbance signals of different frequency bands through a vehicle-mounted coil array to obtain a magnetic field disturbance signal set; constructing a dynamic sensing matrix for each magnetic field disturbance signal, and performing compression reconstruction by adopting an orthogonal matching pursuit algorithm to obtain a line impedance feature vector group; constructing a security constraint set based on the line impedance feature vector group, and respectively applying the security constraint set to a multi-objective optimization algorithm to solve the optimal capacity calling proportion of the electric vehicle battery pack; and controlling the electric vehicle to output reverse power to the distribution network area based on the optimal capacity calling proportion, thereby solving the problem that power supply is difficult to optimize due to the fact that difference between multi-vehicle cooperation and a power line is not considered in a traditional method.

The invention relates to the technical field of robot intelligent actuators, and discloses a magneto-rheological end effector accurate grasping system based on force feedback, which comprises a multi-curved-surface bionic fingertip formed by a magneto-rheological elastomer, and a three-dimensional distributed excitation coil array is embedded in the fingertip. The coil array is excited by a high-frequency chopping constant-current driving module to generate a space gradient magnetic field, and the magnetic field changes the shear modulus of the elastomer within millisecond-level time, so that the fingertip surface hardness jumps in real time along with a control instruction; and the force feedback closed-loop control unit comprises an ultrathin film strain sensing net attached to the inner curved surface of the fingertip. Through time-sharing switching of a negative pressure micropore adsorption layer and a magneto-rheological rigidity keeping mode, traditional adsorption and rigid clamping are changed into a pre-fixing and rigidity gradual change two-section type process, instantaneous force impact during adsorption release is eliminated, meanwhile, thin film wrinkling caused by continuous negative pressure is avoided, and it is ensured that an ultrathin and high-added-value workpiece is kept flat and traceless in the whole transfer process.

The invention discloses a planar two-dimensional micro-displacement sensor based on a four-quadrant eddy current effect, which comprises a detection coil array plate and a target conductor array plate which are parallel up and down, and is characterized in that the detection coil array plate is provided with four planar coils arranged in a shape like a Chinese character'tian 'on an insulating substrate; the target conductor array plate is provided with four metal panels which are arranged in a shape like a Chinese character'tian 'on an insulating substrate. According to the invention, identical excitation signals are introduced into four planar coils on a detection coil array plate, two-dimensional micro-displacement of the detection coil array plate relative to a target conductor array plate is converted into voltage signals of the four planar coils by using an inductance measurement circuit, and the four voltage signals are processed by using a microprocessor system; therefore, the two-dimensional plane relative displacement of the detection coil array plate and the target conductor array plate is obtained. The device is simple in structure, high in measurement precision and suitable for scenes requiring precise measurement of planar two-dimensional micro-displacement in severe environments such as dust and greasy dirt.

The invention discloses an annular electric pole steel bar corrosion detection method, system and device and a storage medium, and relates to the technical field of corrosion detection.The method comprises the steps that an annular coil is arranged in the circumferential direction of an electric pole, adjustable alternating current is applied, and magnetic field changes are detected to obtain signal data; respectively detecting deep corrosion and surface microcracks by utilizing low-frequency excitation and high-frequency excitation, and carrying out frequency domain fusion to obtain fusion data containing corrosion depth and area characteristics; in combination with eddy current response data, reconstructing three-dimensional corrosion distribution by using an improved back projection algorithm, and outputting related data and a thermodynamic diagram; in combination with the thickness of the concrete protection layer and historical data, the excitation frequency is adjusted, and a machine learning model is applied to obtain an optimization frequency, a corrosion mode and a development trend prediction result; according to the invention, the eddy current in the reinforcing steel bar is excited through the annular coil array, and the non-contact and high-precision detection of the corrosion of the reinforcing steel bar in the cylindrical concrete pole is realized by combining a multi-frequency excitation strategy and a three-dimensional signal reconstruction technology.

The invention discloses an anti-offset wireless charging method, which comprises the following steps of: constructing a transmitting coil array as a charging end, detecting a relative position between a receiving coil of equipment needing wireless charging and the charging end, calculating offset data of the receiving coil, and taking a current state of each sub-coil in the transmitting coil during charging as a decision variable; constructing a dual-objective optimization mathematical model taking the minimum mutual inductance deviation and the maximum system transmission efficiency as optimization objectives, solving the dual-objective optimization mathematical model by adopting a genetic algorithm, searching to obtain a Pareto optimal solution set, selecting the Pareto optimal solution set, and controlling the current state of a transmitting coil in a charging end; through a decision variable control mechanism based on the sub-coil current state, the control granularity is refined from the whole coil unit to the sub-coil level, so that the system can dynamically adjust the current distribution mode in the unit according to the tiny offset of the receiving coil, local fine tuning of the magnetic field intensity is realized, and the precision of the magnetic field intensity is improved. And the coupling requirement under the complex offset working condition can be effectively met.

The invention relates to the technical field of industrial control, in particular to an SMT production process quality control method and system. The SMT production process quality control system comprises a soldering paste distribution condition real-time acquisition module, an electromagnetic coil array parameter adjustment module and a reinforcement learning module. The electromagnetic coil array is arranged around the reflow soldering furnace, the infrared thermal imaging technology is combined, the thermal image of the PCB is obtained in real time and sent into the soldering paste segmentation model to be processed, the flowing state of the soldering paste is accurately represented, the system can dynamically adjust the control parameters of the electromagnetic coil array based on the soldering paste distribution thermodynamic diagram, and the stability of the reflow soldering system is improved. Comprise current intensity, current frequency, waveform and the like, so that the electromagnetic field is accurately adjusted, the flowability of the solder paste is optimized, excessive or too little solder paste accumulation is avoided, and the risks of solder bridge and insufficient solder are reduced.

The invention discloses an intelligent magnetic field generator device based on deep learning and a control method. The device comprises a coil array, a programmable current control module and a deep learning module. The coil array adopts an equidistant square matrix structure and is used for generating specific magnetic flux density distribution in a space target area; the programmable current control module is used for adjusting the power-on current amplitude and direction of each coil of the coil array; and the deep learning module is used for establishing a nonlinear mapping relation between the magnetic field distribution of the space target area and the coil current configuration of the coil array so as to realize magnetic field reverse reconstruction and current parameter prediction. The invention aims to solve the problems of complex modeling, difficulty in solving an inverse problem, low control precision and poor flexibility in a magnetic field adjustment process in the prior art, and quick inverse solution and high-precision reproduction from target magnetic field distribution to coil current parameters are realized through the magnetic field generator device.

The invention relates to the technical field of aero-engine state monitoring, and discloses an aero-engine blade tip gap measuring probe and system based on an eddy current method.The aero-engine blade tip gap measuring probe adopts a coplanar Archimedes spiral double-coil array, and in the measuring process, the blade tip gap can be measured by applying anti-phase excitation; the common-mode noise suppression in the blade tip clearance measurement process is realized by combining a differential amplification circuit; signal extraction and temperature drift compensation are realized through a phase-locked amplification technology and an impedance-resistance orthogonal decoupling architecture, and finally micron-order gap analysis is realized. The aero-engine blade tip clearance measurement system provided by the invention can still keep excellent reliability under extreme working conditions of high temperature, high rotating speed and the like of a turbine, and meanwhile, the measurement precision of the blade tip clearance can be remarkably improved.

A multilayer coil and a multilayer coil array, each including a body in which a magnetic layer is laminated, a first coil including a plurality of first coil conductor layers in a lamination direction, and a second coil including a plurality of second coil conductor layers in the lamination direction. The first and second coils are inside the body, first and second external electrodes are electrically connected to the first coil, and third and fourth external electrodes are electrically connected to the second coil. The first to fourth external electrodes are on a bottom surface of the body, the second coil is at a position farther from the bottom surface of the body than the first coil is in the lamination direction, and the multilayer coil includes a first extended conductor inside the body and connecting an end of a first coil conductor layer closest to the bottom surface.

The invention discloses a paper folding structure inductance type self-decoupling miniature six-dimensional force sensor, which belongs to the technical field of force sensors and comprises a base, a folding flexible circuit board, a metal shell, a communication cable, a coil inductance measuring circuit and an elastic body. The folding flexible circuit board comprises a coil array and an inductance measuring circuit, the coil array is folded on the upper surface and the four side faces of the base, the inductance measuring circuit is folded at the bottom of the base, and a communication cable is led out of the inductance measuring circuit. The metal shell is arranged above the base and surrounds the surface, except the bottom surface, of the folding flexible circuit board; an elastic body is arranged between the metal shell and the base. The elastomer converts six-dimensional force borne by the metal shell into six-dimensional displacement. According to the sensor, the characteristic that the eddy current effect is sensitive to normal displacement and insensitive to tangential displacement and rotation is utilized, self-decoupling measurement of six-dimensional displacement of the metal shell is achieved in combination with three-dimensional coil layout, and therefore self-decoupling six-dimensional force measurement is achieved, and the sensor can be integrated to the fingertip of the dexterous hand to provide endogenous tactile perception.

The invention discloses a six-degree-of-freedom magnetic suspension workbench structure and a control method thereof, belongs to the technical field of magnetic suspension workbenches, and aims to solve the problems that the stroke of a traditional workbench is difficult to expand, the modeling precision is low, and the influence of a coil edge effect is large. The magnetic suspension workbench structurally comprises a stator capable of being spliced with a PCB coil array, a rotor of a symmetric two-dimensional Halbach permanent magnet array, a data processing module with an information fusion function and an H-bridge-containing driving and real-time control system. According to the control method, a high-precision electromagnetic force model is established, a magnetic field area is divided, a compensation coefficient is introduced to correct an end effect, a pseudo-inverse method based on least square is adopted to decouple and calculate the size of a driving current, and the saturation suppression of the current and the dynamic gating of the coil are realized in combination with a current calculation result; the method can be applied to the fields of precision machining and micro-nano manufacturing, and high-precision long-stroke motion control is achieved.

An RF coil array includes: a first coil unit including a first fixing belt formed of a first stretch material stretchable in a first direction and RF coils independently disposed on the first fixing belt; and a second coil unit including a second fixing belt formed of a second stretch material stretchable in the first direction and RF coils independently disposed on the second fixing belt. The first coil unit is mounted on a subject with a distal end of the first fixing belt directed from one side to the other side of the subject in the first direction, and the second coil unit is mounted on the subject with a distal end of the second fixing belt directed from the other side to the one side of the subject in the first direction such that at least a part of the second coil unit overlaps the first coil unit.

The invention discloses an intelligent glasses box based on artificial intelligence and a wireless charging control method thereof, and relates to the technical field of intelligent wearable equipment, and the method comprises the steps: generating a cooperative charging strategy matrix in a local network through an equipment group distributed voting mechanism based on an encrypted prediction parameter packet; generating an electromagnetic field focusing parameter configuration table through a time-frequency-space three-dimensional resource allocation scheme based on the cooperative charging strategy matrix and the three-dimensional coordinates of the equipment in the glasses box; the electromagnetic field focusing parameter configuration table drives the programmable coil array to dynamically adjust the charging signal and generate a charging efficiency real-time monitoring curve; and detecting the actual charging efficiency in the charging efficiency real-time monitoring curve, and dynamically generating an increment optimization parameter packet. Through space coordinate mapping and dynamic spectrum isolation in time-frequency-space three-dimensional resource allocation, accurate directional transmission of electromagnetic energy is realized, wireless interference among multiple devices is eliminated, and charging efficiency optimization and compatibility guarantee are achieved.

This invention relates to the field of magnetic stimulation technology, providing a time-coherent, multi-target, precisely adjustable magnetic stimulation method and system. The method includes constructing a coil array at the desired magnetic stimulation site. The coil array includes a first coil positioned at the center of the array and multiple second coils positioned around the periphery of the first coil. The first coil and the desired second coils are then energized. The frequency of the high-frequency alternating current supplied to the first coil and the energized second coils is controlled to generate a low-frequency envelope induced electric field between the first and second coils. The current amplitude ratio of the coil pair consisting of the first coil and one of the energized second coils is adjusted to adjust the focusing area of ​​the low-frequency envelope induced electric field, precisely locating and stimulating the desired target point. This invention improves stimulation depth and focus, and enables simultaneous stimulation of multiple targets, achieving adjustable, controllable, and precisely positioned stimulation without moving the coil positions.

A system, comprising a target, a first receiving coil array, and a second receiving coil array. The target includes: (i) a first array of conductive features that are arranged in a line or arc and separated from one another by voids, and (ii) a second array of conductive features that are arranged in a line or arc and separated from one another by voids, the conductive features in the first array being staggered with respect to the conductive features in the second array. The first receiving coil array is configured to sense a first magnetic field that is associated with the first array of conductive features. The second receiving coil array is configured to sense a second magnetic field that is associated with the second array of conductive features.

Tracking a pose of a portion of an anatomical structure using an inverted-direction electromagnetic navigation system may comprise generating a signal comprising a plurality of frequencies. The signal comprising the plurality of frequencies may be received at a transmitter coil array. The transmitter coil array comprises a plurality of transmitting micro coils. Each of the plurality of transmitting micro coils is coupled to a portion of an anatomical structure of a patient. In response to receiving the signal comprising the plurality of frequencies, an electromagnetic field may be generated at each of the plurality of transmitting micro coils based on the received signal. Each of the generated electromagnetic fields may be detected at a receiver coil array comprising at least one receiving coil. A pose of at least one of the plurality of transmitting micro coils may then be determined.

The invention provides a marine electromagnetic take-off and landing transportation system based on a heavy-load unmanned aerial vehicle, and belongs to the technical field of unmanned aerial vehicle marine heavy-load transportation. The system comprises a shipborne electromagnetic take-off and landing subsystem, a shore-based electromagnetic take-off and landing subsystem, a heavy-load fixed-wing unmanned aerial vehicle, a marine low-altitude communication monitoring network and a comprehensive scheduling platform; the shipborne electromagnetic take-off and landing subsystem is of a multi-section coil array structure, the effective length of a coil array of the shipborne electromagnetic take-off and landing subsystem can be matched with the available space of a fishing ship deck, the take-off and landing distance is controllable, and therefore the problem of take-off and landing in the narrow space of the deck is solved. The shore-based electromagnetic take-off and landing subsystem is integrated with a three-dimensional terrain modeling module, the real-time environment of a landing area is pre-judged through laser radar and satellite remote sensing data, parameters of an electromagnetic propulsion device and an electromagnetic adsorption device of the shore-based electromagnetic take-off and landing subsystem are dynamically adjusted, then the shore-based electromagnetic take-off and landing subsystem adapts to rugged terrain, and the limitation that a traditional unmanned aerial vehicle depends on a flat take-off and landing field is avoided. And through data linkage and intelligent scheduling of multiple subsystems, the overall efficiency and reliability of marine transportation are greatly improved.

The invention provides a chassis universal function safety test platform which comprises a platform plate, a roller, a clamping mechanism, an upper computer and a friction adjusting mechanism. The friction adjusting mechanism comprises magnetorheological fluid, a covering film, an electromagnetic coil array, an electric sliding table, a liquid pump, a filtering pipeline, a magnetic sieve plate, an L-shaped pipe, a transverse pipe, a telescopic pipe, an insertion pipe, a top plate, a first electric push rod and a conveying pipe, the wheels make contact with the magnetorheological fluid through the covering film, and a magnetic field generated by the electromagnetic coil array can change the state of the magnetorheological fluid; the magneto-rheological fluid can be switched between a liquid state and a semi-solid state, road surfaces with different friction coefficients are simulated, rich and comprehensive test scenes are provided, the accuracy of a chassis test result is improved, meanwhile, the magneto-rheological fluid can enter the filter pipeline under the action of the liquid pump, metal scraps are filtered through the magnetic sieve plates arranged in the filter pipeline in a gradient mode, and the test efficiency is improved. Failure caused by agglomeration effect is avoided, influence on magnetic field intensity is reduced, and accuracy of test results is further guaranteed.

The invention belongs to the technical field of wireless charging, and particularly relates to an in-vitro charging device of a wireless charging system and implantable medical equipment, the in-vitro charging device comprises an inverter and a transmitting coil array, and the inverter is electrically connected with the transmitting coil array so that a transmitting coil can generate an induced magnetic field; wherein the transmitting coil array comprises at least two coil units which are connected in series, and all the coil units are coaxially superposed; the coil unit comprises two coils connected in series, and the two coils are symmetrically arranged and partially overlapped. The four-coil array is innovatively adopted as the transmitting end, magnetic decoupling is achieved among the coils through a special spatial arrangement mode, and it can be always guaranteed that at least part of the coils and the receiving coil of the in-vivo charging device are in a good coupling state under the condition of deviation in any direction through the design.

The invention provides a reactor turn-to-turn short circuit online monitoring system and method based on a detection coil array, and the system comprises a signal collection unit which obtains the differential voltage signal data of a plurality of detection coil groups of a to-be-detected annular air-core reactor; the filter circuit is used for carrying out filtering processing on the data to obtain differential voltage signal data after filtering processing; the A / D conversion circuit is used for performing analog-to-digital conversion on the data to obtain a plurality of groups of discrete data; the controller is used for processing the plurality of groups of discrete data by adopting a second-order difference method to obtain change rates of the plurality of groups of discrete data; and the monitoring center upper computer analyzes whether a turn-to-turn short circuit fault occurs in the to-be-detected annular air-core reactor based on the change rate of the plurality of groups of discrete data. The turn-to-turn short-circuit fault part can be timely removed at the early stage of the turn-to-turn short-circuit fault, the monitoring device and the monitoring process are simple, the monitoring cost is reduced, and the sensitivity and the accuracy of turn-to-turn short-circuit fault monitoring are improved.

An inductive coil array 6, for determining a shape of an object 10, comprises an active coil 7, for providing an output signal through an output connection 9 and one or more passive coils 9, magnetica

The invention provides a coil array and a wireless power transmission system, the coil array comprises at least one coil structure, the coil structure comprises three coil units, and the three coil units respectively form three sides of the same triangle so as to form the coil structure; wherein each coil unit in the same coil structure is configured to allow the current flowing through the coil unit to form a current loop, and the coil units in the same coil structure are the same or different; moreover, each coil unit in the same coil structure is configured to be excited by an independent amplitude-modulated wave and obtain a driving current, so that the coil array is allowed to be configured to obtain optimal magnetic field distribution and magnetic field polarization according to different phases and current directions and form a three-dimensional rotating magnetic field.

An MRI system includes an MRI scanner having a bore and a table configured to move a subject to be imaged into and out of the bore. The MRI system includes a flexible RF receiving coil array integrated within the bore and electronically coupled directly to the MRI scanner, wherein the flexible RF receiving coil array remains in the bore regardless of a position of the table, and the flexible RF receiving coil array is located underneath the table when the table is located within the bore. The MRI system includes an automated mechanism configured to automatically move the flexible RF receiving coil array from underneath the table on a first side of the subject, to pull the flexible RF receiving coil array over the subject from the first side to a second side of the subject, and to fasten the flexible RF receiving coil on the second side.

The application discloses a kind of pipe inner wall high-pressure pulse cleaning system and method suitable for central air conditioner, it is related to pipeline cleaning technical field, including movable electromagnet coil array, for generating the magnetic field inside the elbow of pipeline, change the motion trajectory of magnetite particles;Pulse synchronous controller, for detecting the working state of pulse cleaning equipment and with pulse cleaning equipment synchronous control movable electromagnet coil array power-on time and magnetic field intensity;Eddy current buffer flow guide, the application is by movable electromagnet coil array, with pulse cleaning equipment electric connection pulse synchronous controller and install in elbow inside eddy current buffer flow guide, realizes the accurate control of magnetite particles motion trajectory in high-pressure pulse cleaning process and kinetic energy buffer, thoroughly solves the centrifugal acceleration wear problem at elbow under the premise of not reducing cleaning effect.

The present invention discloses an inductive linear absolute position measuring device, which relates to the field of linear position measurement. The inductive linear absolute position measuring device includes a single-track grating scale and a reading head. The reading head includes: a substrate; an induction coil drawn on the substrate. The induction coil includes an S coil array and an R coil array. Each coil array includes n independent complementary coils. Each independent complementary coil is composed of 2 sub-coils wound in opposite directions in series; an excitation coil surrounding the induction coil. The excitation coil is a multi-turn closed coil connected in series; a hardware processing circuit arranged on the substrate, including an excitation signal driving circuit, a selection switch circuit, a demodulation circuit, an operational amplifier circuit and a programmable logic device. Compared with the prior art, the inductive linear absolute position measuring device provided by the present invention is smaller in size, higher in reliability, higher in measurement accuracy, and stable and accurate in measurement.

The present application is drawn to a system and method, as well as method for manufacture of a device and system for determining the position and orientation of at least one magnetic field sensor comprising: a rigid structure comprising an array of at least five electromagnetic coils; at least one wire that connects to and powers the electromagnetic coils; wherein the placement and orientation of the electromagnetic coils on the rigid structure are predetermined; wherein the electromagnetic coils, each having a predefined magnetic moment per unit current, are constructed with a printed circuit board (PCB) comprising at least one conductive layer; and wherein the system is configured such that a stray magnetic field emanating from the at least one, as measured at the location of the at least one magnetic field sensor, generates substantially lower magnetic field intensity than that produced by each of the at least five electromagnetic coils.