34 results about "Harmonic fields" patented technology

The invention provides a target field method for design shimming coils for cylindrical Halbach magnet (commonly known as a magic ring magnet). All orders of shimming rings which are designed according to the invention are respectively fixed on all coaxial cylindrical surfaces on the inner side of the permanent magnet. Closed loops as shown in Drawings 3 to 10 are cut into 'open loops' at appropriate positions, and the close open loops are sequentially and serially connected and an order of shimming coil is formed. Every order of shimming coil is electrified and generate precise corresponding order of harmonic magnetic field in an interested area in the center of the magnet. When in design, the value of a stream function meets the condition that the magnetic fields of the coils do not exceed a target harmonic field for a certain threshold, the power consumption functions of the coils are minimum, and the projection of the isolines of the stream function realizes the distribution of leads. After being fed with appropriate reversing current, all orders of harmonic shimming coils designed according to the invention can precisely offset harmful harmonic components in the magnetic fields, so that the purpose of shimming horizontal magnetic fields Bx of the magic ring permanent magnet is achieved, and simultaneously, the cylindrical Halbach magnet shimming coils have the characteristics that the power consumption of the coils is low and the shimming efficiency is high.

The invention discloses a computer interaction type method for segmenting a single tooth crown from a three-dimensional jaw model. The method includes the steps: reading and visually displaying the three-dimensional jaw grid model; detecting anatomic characteristic points and an occlusion plane of upper teeth of a jaw in the three-dimensional jaw grid model; assigning constraint points of harmonic fields of the three-dimensional jaw grid model; calculating the harmonic fields according to constraint conditions to obtain a tooth crown segmenting border line; performing grid cutting according to the obtained tooth crown segmenting border line to obtain a tooth crown model. By the method, a tooth segmenting border can be accurately obtained, the method is simple to use, and a user interactively determines two border points on a visual view of the jaw model for a single tooth to be separated, so that the tooth crown grid model of the tooth can be accurately obtained. The method has important significance for dental orthodontics, virtual jaw surgery simulation and the like.

The invention discloses a self-starting permanent magnet motor with a three-section-circular-arc magnetic pole structure, belonging to the technical field of motors. The permanent magnet motor consists of a stator and a rotor, wherein a permanent magnet in the rotor adopts an embedded structure in which magnetic poles N and magnetic poles S are arranged alternatively; the surface of each magnetic pole of the rotor consists of three sections of circular arcs; the radius of a middle section circular arc of each magnetic pole is the same as that of the outer circle of the rotor, so that a smallest air gap of the permanent magnet motor is ensured; the circle center of the middle section circular arc of each magnetic pole is the same as that of the inner circle of the stator; the radiuses of two lateral circular arcs of each magnetic pole are smaller than the radius of the outer circle of the rotor; and the circle centers of the two lateral circular arcs are closer to the surface of the rotor than the circle center of the middle section circular arc, so that the permanent magnet motor with a non-uniform air gap structure is formed. The angle of the middle circular arc of each magnetic pole and the eccentric distance between the circle centers of the two lateral circular arcs are adjusted, so that the harmonic content of a no-load air gap magnetic field is lower and a reasonable magnetic pole shape is obtained. The influences of the harmonic field and harmonic current of the permanent magnet motor on the motor efficiency and the torque fluctuation are improved remarkably; and the permanent magnet motor is suitable for long-time continuous running working occasions.

The invention discloses an off-network inverter control method based on frequency division virtual impedance. The off-network inverter control method comprises the steps of measuring a voltage u<c> of an inverter capacitor, an output current i<L> of an inverter and an output current i<o> of an LC filter; extracting a fundamental wave from the voltage of the capacitor C to obtain u<cf>, and extracting an angular frequency Omega<f> of the u<cf>; giving a reference voltage amplitude /U<ref>/, wherein the reference voltage amplitude /U<ref>/ and the angular frequency Omega<f> form a reference capacitance voltage u<creff>; employing a fundamental wave field P regulator by a current regulation ring; setting frequency division virtual resistances z<vir5>, z<vir7> until z<virh>; obtaining harmonic virtual impedance voltages u<vir5>, u<vir7> until u<virh>; employing harmonic fields PR5, PR7 until PRh regulators by a voltage outer ring, and generating an inductive current reference value; employing harmonic fields P5, P7 until Ph regulators by the current regulation ring to obtain a harmonic field modulation signal; and subtracting the harmonic field modulation signal from the fundamental field modulation signal, and outputting a switch pulse to control switch-on and switch-off of an inverter power device after pulse width modulation (PWM). By the off-network inverter control method, a harmonic current is suppressed, balanced running without circulation current of a parallel inverter is achieved, and the system reliability is improved.

The invention discloses an automatic whole dental crown segmentation method through a harmonic-field-based three-dimensional tooth jaw model. The automatic whole dental crown segmentation method includes the steps that a three-dimensional tooth jaw grid model is read in and visually displayed; automatic detection and classification are conducted on anatomical feature points of upper tooth jaw teeth in the three-dimensional tooth jaw grid model, and the occlusion plane is automatically recognized; useless data representing the non-tooth-crown part at the bottom of the tooth jaw are eliminated; the constraint point of the harmonic field of the three-dimensional tooth jaw grid model is specified; the harmonic field is calculated according to the constraint condition so as to obtain a tooth crown segmentation boundary line; grid segmentation is conducted according to the obtained tooth crown segmentation boundary line to obtain a tooth crown model. By means of the method, all tooth segmentation boundaries are obtained accurately through one-time processing, and the automated degree is high. The method has great significance to dental orthodontics, virtual tooth jaw operation simulation and the like.

The invention relates to a mechatronic alternating current (ac) motor stator core of a compressor and a wire embedding method thereof and especially relates to an ac motor stator core of a piston refrigeration compressor used in a refrigerator. The motor stator core comprises an iron core body. A rotor aperture is arranged in a middle part of the iron core body. Wire embedding slots, which penetrate along an axial direction, are arranged along a circumferential direction of a hole wall of the rotor aperture. Inner sides of the wire embedding slots are provided with notches. A circumferential width (chord length) Bs0 of the notch is 0.1-1.0 mm. By using the stator core and the method of the invention, iron core surface losses and tooth pulse vibration losses can be reduced; an air gap coefficient is decreased; a field current is reduced; a power factor is raised so that working efficiency of the motor can be raised. Through redesigning a slot type size of the wire embedding slot, the additional losses generated by a harmonic field can be reduced so that the working efficiency of the motor can be further raised. A computer simulation experiment shows that the working efficiency of the motor can be increased by 1.5% by using the stator core of the invention. The stator core and the method is especially suitable for the single-phase asynchronous ac motor used in the totally enclosed refrigeration compressor.

An electrical machine includes a first part-winding, a second part-winding, a core having slots in which the first and the second part-windings are wound, and a switching device for connecting the first part-winding to the second part-winding. In each of the slots, one of the two part-windings forms a bottom layer at the slot base, and the other part-winding is disposed as a top layer parallel above the bottom layer. The two part-windings are capable of being connected in parallel with the switching device during operation of the electrical machine. It is thus possible for a symmetrical field distribution to be achieved in a startup circuit. In addition, no additional components caused by harmonic fields occur in the torque curve which could impede runup.

The invention relates to a underwater acoustic sensor network routing algorithm and system. The underwater acoustic sensor network routing algorithm comprises the following steps: step S1, acquiring a network topological structure; step S2, electric potential distributing; and step S3, constructing routing. The technical problem that the routing finding is failed due to local minimum point is overcome by use of the underwater acoustic sensor network routing algorithm disclosed by the invention, and the method is especially suitable for determining the routing in a underwater acoustic sensor network in the marine environment.

The invention relates to a three-phase asynchronous motor special for YZS series injection molding machines. The three-phase asynchronous motor is mainly characterized in that: a front end cover and a rear end cover are fixedly connected with a motor shell; a motor shaft is supported in the motor shell by a bearing assembly; a rotor is arranged on the motor shaft; a stator is arranged on the motor shell; a fan is fixed on the motor shaft; and a fan cover is fixed on the rear end cover. The three-phase asynchronous motor is characterized in that: an axial end of the motor shaft extends out of the front end cover; and a key is arranged in a key groove in front of the motor shaft. A wave-shaped spring is arranged between the bearing assembly and the front end cover; an elastic retainer ring for a hole is arranged between the bearing assembly and the rear end cover; the upper part of the stator is connected with a junction box through a bolt; and a gap is formed between the stator and a rotor core. The three-phase asynchronous motor can reduce the cost and raw materials, has high power, can improve the starting torque, can eliminate synchronous accessory torque and rotor harmonic field, is favorable for reducing electromagnetic noise, can improve the starting torque and reduce non-uniformity of the air gap of the motor, and can improve the process flow and processing assembly quality.

The invention provides a femur segmenting method in a tomographic image. The method comprises the steps that a tomographic picture with a hip joint is acquired; a bone tissue region is extracted from the tomographic picture; a joint gap region between femoral head and acetabulum is marked; the harmonic field contour of the joint gap region is calculated; and femoral head is segmented according to the harmonic field contour. The joint gap region is marked to acquire the approximate range of the joint gap region. The harmonic field contour of the joint gap region is calculated to acquire the exact joint gap region boundary and the femoral head boundary. Femoral head is efficiently and accurately segmented. The degree of automation is high. The femur segmenting method has an important significance for the assessment of joint wear, hip arthritis auxiliary diagnosis, hip replacement surgery simulation and other follow-up applications.

The invention belongs to the field of design and manufacture of the AC motor and particularly relates to a low-loss stator punching sheet of an AC motor. The structure provided by the invention is similar to that of the stator punching sheet of the conventional AC motor the power of which is between 0.55kW and 315kW, but the width of a stator rabbet of the low-loss stator punching sheet of the AC motor is 50 to 85 percent of that of the stator rabbet of the stator punching sheet for the same type of conventional AC motor. The improvement makes the stator rabbet narrowed and makes a tooth crest widened and correspondingly makes additional loss generated by a harmonic field on the surface of an rotor core and in the tooth crest region of the rotor obviously reduced. Moreover, an air gap coefficient is decreased, an effective air gap is correspondingly decreased, then a no-load current is reduced therewith, a power factor is also correspondingly improved in the full-load running process and a full-load current is increased, thus, copper loss and iron loss of the motor are reduced to achieve obvious energy-saving effect.

The invention discloses an anisotropic finite element modeling method based on harmonic field for patient-specific sclera, which comprises the following steps that high precision laser scanning is applied to attain a stereoscopic model of a patient-specific sclera; the stereoscopic model is designated with a sclera weight and provided with a umbrella operator to attain the harmonic field; the harmonic field is provided with constrained conditions, the gradient field and the contour field of the harmonic field are distributed; through the gradient field and the contour field, a regular hexahedral mesh is distributed smoothly on an irregular sclera; the stereoscopic model is provided with anisotropic material parameters based on the harmonic field; the experiment result is compared. The anisotropic finite element modeling method based on harmonic field for patient-specific sclera can provide effective modeling for patient-specific sclera. Anisotropic material orientation field are added, thereby high accuracy and quality of the modeling being guaranteed, and irregular hemisphere sclera being provided with individual parameters.

The invention discloses a civil house platform distortion field intensity safety assessment method under multi-condition constraint. The method comprises the following steps of: A, establishing a house model and a human body model; B, calculating a quasi-static time-harmonic field mathematical model; C, measuring a distortion electric field at a civil house platform; D, measuring a distortion electric field, a potential and an open-circuit current near the human body; and E, evaluating the distortion field intensity at the civil house platform. The defects in the prior art can be overcome, and the accuracy of power frequency electric field evaluation at the civil house platform is improved.

The invention relates to a scene-divided Norton equivalent harmonic source model identification method considering distributed new energy, and the method comprises the following steps: S1, generating interval type data based on harmonic monitoring data and meteorological data, dividing a user typical harmonic scene considering distributed new energy power generation characteristics by using a density clustering and linear comprehensive change point detection method; S2, solving a probability density function of a system side harmonic impedance module value in a user typical harmonic scene by using kernel density estimation; and S3, constructing a scene-divided Norton equivalent harmonic source model based on harmonic monitoring statistics and meteorological data and considering distributed new energy. According to the method, the change of the harmonic characteristics of the system and the user and the influence of meteorological conditions on the distributed new energy harmonic characteristics can be identified.