191 results about "Magnetic chain" patented technology

The invention discloses a motor synchronous modulation method and a control system thereof. Under the offline state, the optimization calculation on the switching angle of an inverter is carried out according to the total harmonic loss of the motor; the modulation ratio is taken as an independent variable; m switching angles (Alpha1, Alpha2,..., Alpha m) corresponding to the modulation ratio are worked out by the optimization algorithm; the modulation frequency division number obtained by the m switching angles is 2m+1; the m switching angles are used as a data table memorized in a memory; during the working process, according to the target modulation ratio, the m switching angles can be obtained by searching the data table, thus carrying out conduction control on the inverter switch device. By adopting the method and the technical scheme described by the control method, the running track of the motor magnetic chain can be a regular polygon so as to reduce the output current harmonicsof the inverter, thus improving the control performance of the transmission system.

The invention discloses a multitooth magnetic bridge type hybrid excitation magnetic flux switching motor. Permanent magnets, an armature winding and a single-phase excitation winding are installed on a stator; the tooth number of the stator is four times of the number of the permanent magnets; and part of a rotor part is a salient pole, and a rotor has no winding or permanent magnets and has simple and firm structure. An air gap magnetic field comprises an electric excitation magnetic field generated by the excitation winding and a magnetic field generated by the permanent magnets and is adjusted by changing the magnitude and the direction of excitation current, thereby improving the rotating speed operating range and the magnetic weakening capability of the motor. An electric excitation magnetic force line is connected with a magnetic bridge for closing after penetrating through an iron core at the top of the permanent magnets, which is beneficial to reducing the electric excitation ampere turns. The invention has parallel connecting structure of the excitation winding and the permanent magnet in space, bipolarity of phase magnetic flux, large magnetic chain change amplitude value and higher torque output capability and power density and is suitable for a low-speed straight application occasion.

The invention discloses a polyphase motor fault-tolerant control method and system based on a multi-neural-network inverse model in the field of motor control. The polyphase motor fault-tolerant control method comprises the following steps of: respectively acquiring a normal state inverse model and a fault state inverse module of a motor by adopting a neural network inverse model; selecting a corresponding inverse module and a current converter to be serially connected in front of a hysteresis current comparer by a current detection magnetic-chain observation inverse model switching module under a normal state or a fault state to obtain a constant pseudo-linear system; only considering to convert current of d axis and q axis of a stator, inversely output by the neural network after circuit-opening into four phases of reference current, and only adjusting phase relationships of the rest four phases of current; and when motor model parameters changes because the motor has a fault, approaching to a motor inverse system still accurately without the need of correcting control parameters of additional controllers again. According to the polyphase motor fault-tolerant control method and system disclosed by the invention, the adaptability of a fault-tolerant controller to the winding fault of the motor is improved, and the requirements and the circuit cost of an inverter power device are reduced; and the polyphase motor fault-tolerant control method and system have stronger fault tolerance and robustness.

The invention discloses a curved surface self-adaption magnetic adsorption wall-climbing robot, which includes a vehicle body and chain driving assemblies arranged on the two sides of the vehicle body, wherein each chain driving assembly includes a driving motor, a driving chain wheel and a driven chain wheel; each driving motor is fixedly mounted at the bottom of the vehicle body; the driving chain wheels are coaxially and fixedly mounted on driving shafts of the driving motors; and the driven chain wheels are coupled at the bottom of the vehicle body. The curved surface self-adaption magnetic adsorption wall-climbing robot is characterized in that a magnetic chain is arranged between each driving chain wheel and each driven chain wheel; and self-adaption mechanisms are fixedly mounted on the two sides of the vehicle body respectively, and each self-adaption mechanism is positioned on the magnetic chain on the same side where the self-adaption mechanism is arranged. The curved surface self-adaption magnetic adsorption wall-climbing robot has the advantages that the self-adaption mechanisms arranged on the inner sides of the magnetic chains can better clung to and fit with the warped curved surface when the wall-climbing robot walks on a steel curved surface or a warped wall surface, so that the magnetic adsorption area is enlarged, the adsorption efficiency is improved, and the exercise safety performance of the wall-climbing robot is improved, and as lifting wheels arranged on connecting racks can be used for tensioning the magnetic chains, chain slippage and dropping can be prevented during the movement of the wall-climbing robot, and the wall-climbing robot can adapt to and climb the wall with an upright even inverted warped curved surface.

The invention discloses a device and a method for efficiently polishing and processing high-precision balls in a cluster magneto-rheological mode. The device comprises upper and lower polishing discs,and a magnetic field generator. Under action of magnetic fields, viscosity of magneto-rheological fluid which enters V-shaped slots of the polishing discs is increased within extremely short time, and a magnetic chain string clamps abrasive particles to form a flexible polishing pad; ceramic balls are coated by the flexible polishing pad in the V-shaped slots; and along with motion (auto-rotationduring revolution) of the polishing discs, the surfaces of the ceramic balls are polished by the abrasive particles in the magneto-rheological flexible polishing pad. The device does not need to adopt a circulating device for regenerating the magneto-rheological fluid, so that the whole process from rough polishing to fine polishing of the ball bodies can be realized through once clamping; and anobtained workpeice is good in surface consistency, is stable in shape precision, is high in processing efficiency, and is free of surface and sub-surface damages; and moreover, the device is low in cost, and is suitable for high-efficiency ultra-smooth uniform grinding and polishing of high-precision ceramic balls in ceramic ball bearings.

The invention discloses a position-sensor-free control method suitable for four-quadrant operation of a switch reluctance motor, and belongs to a switch reluctance motor control method. The position-sensor-free control method comprises the following steps of constructing a simplified inductance model according to a fourier series expression of inductance of the switch reluctance motor; fitting a function relation in which an inductance model parameter is changed along with phase current by measuring inductances at three special positions of the switch reluctance motor at different phase currents on line, and constructing a non-linear inductance model of the switch reluctance motor; deriving an analysis formula for estimating a position of a rotor of the switch reluctance motor through phase inductance according to the non-linear inductance model; and when the motor runs, detecting the phase current and phase voltage in real time, estimating an excitation phase magnetic chain according to a voltage equation to obtain excitation phase inductance, calculating the current position of the rotor according to the estimation analysis formula by using the derived position of the rotor, and realizing sensor-free running control over the switch reluctance motor according to the estimated position of the rotor. The algorithm is simple, small in calculated amount, favorable for real-time implementation of a micro controller and higher in position estimation precision.

The invention discloses a permanent magnetic synchronous motor control system under variable damping-based two-degree-of-freedom passive control. The system consists of a main circuit and a control circuit, wherein the control circuit comprises a signal detection circuit, a rotating speed control outer ring and a torque control inner ring. A rotating speed outer ring controller is designed by adopting a PI (Proportion Integration) control method, and the output is a given signal of passive control; a variable-damping two-degree-of-freedom passive control method is adopted in a torque magnetic chain inner ring controller, and the output is a two-phase alternating-current voltage on a two-phase rotary coordinate system; and passive control of the permanent synchronous motor is realized through space vector pulse width modulation conversion and a power switching device acting on a main circuit inverter. Due to the adoption of a passive control method disclosed by the invention, independent setting of the tracking performance and interference performance is realized, the rotating speed of the motor meets the requirement of accurate control, and the overall performance of the system can be improved effectively.

The invention discloses a vector control device for an induction motor and relates to a vector control device without speed sensor for the induction motor. The invention solves the problem of the vector control method of the conventional induction motor that a system is unstable in a low-speed power generation state and has a bigger rotating speed observation error under a low-speed condition because a rotating speed adaptive rate cannot guarantee the stability of an algorithm. In the invention, the speed of the motor can be observed by adding the exciting current error between the actual value and observed value of an exciting current and the product of a q axis stator magnetic chain observed value and a variable gain (M) into the general product of the observed current bias and the observed rotor magnetic chain and through a PI regulator; and thus, the speed of the motor can be controlled. The device reduces the low-speed performance of the system considerably and solves the unstable problem of the system in a power regeneration state effectively. The device is used for controlling the rotating speed of the induction motor.

The invention discloses a method for predicting direct power of an improved T type three-level permanent magnetic direct drive wind power system. A topological structure of the permanent magnetic direct drive wind power system is an improved T type three-level converter. According to an SVPWM technology, the problem that a switching frequency is not fixed, the system loss is reduced and a power factor of the system is improved. A machine side converter control strategy is a prediction direct power control strategy. A rotating speed loop is an external loop. A power loop is an internal loop. The power loop is prediction power control. A PI adjustor is not required. A control structure is simple and an effect is good. A network side direct power control strategy is a direct power control strategy based on virtual flux orientation. A power network voltage does not need to be sampled. A structure is simple. The system cost is reduced. The dynamic stability is improved. The prediction direct power control strategy and the direct power control strategy based on virtual flux orientation are based on space vector pulse width modulation (SVPWM), so the system has a fixed switching frequency and unit power factor.

The invention relates to a method for realizing the stable operation of a frequency converter under V / F (voltage / frequency) control. The method comprises the steps of sampling, coordinate conversion, power calculation, one-order low-pass filtering, P (power) regulator regulation, amplitude limitation and integration processing. The method concretely comprises the steps that the motor three-phase current is sampled and filtered, and the motor input voltage is sampled; the three-phase current and the voltage are converted into two-phase current and voltage, and the current and the voltage on the alpha axis and the beta axis are calculated; the active power P and the apparent power S input into a motor are calculated; the efficiency error is subjected to P regulation and is multiplied by the rated frequency to obtain the compensation frequency; the compensation frequency is subjected to amplitude limitation; and for the integration processing, a rotating angle theta is obtained through the integration operation on the angle frequency omega. The active power change is controlled, the rotating angle can be dynamically regulated through adopting a frequency compensation method in the magnetic chain vector coordinate system, the current oscillation is inhibited, and the stability of the system is maintained. In the application, the stability of the system can be regulated through regulating the KP values according to the actual conditions.

The invention provides floating agglomeration electromagnetic concentrating equipment. The lower end of a cylinder is provided with a concentrate discharging port or connected with a concentrate discharging pipe, a discharging port of a feeding pipe extends into the cylinder and is positioned on the middle upper portion in the cylinder, an output port of a micronano bubble generating device is communicated with an inner cavity of the cylinder tangentially and corresponds to the discharging port of the feeding pipe in position, an alternating magnetic field generator is positioned on the periphery of the cylinder and provides a nonuniform alternating magnetic field, and an overflow tank is positioned above the cylinder and communicated with the upper end of the cylinder. The equipment can generate a lot of micronano bubbles, especially nano bubbles, and the micronano bubbles and the alternating pulse electromagnetic field jointly act to enable magnetic or strongly-magnetic minerals and nonmagnetic or weakly-magnetic gangue minerals in material ore pulp to be in dispersion, agglomeration, re-dispersion and selective agglomeration respectively so as to enable the nonmagnetic or weakly-magnetic gangue minerals to thoroughly break away from a magnetic chain finally, so that escape of tailings is avoided effectively, and high-grade magnetic iron concentrate or titanomagnetite concentrate is obtained finally.

The invention provides a variable speed pumped storage unit (Variable Speed Pumped Storage Units, VSPSU) water pump working condition self-start control device and a method thereof. The stator winding is short-circuited, the rotor current is controlled through its own alternate current excitation device, so as to control the rotor magnetic field, drag torque is generated by the interaction between the stator and the rotor magnetic field, to drive the rotor to start. A full order state observation device is built, the precise stator magnetic chain location is estimated, the decoupling control of rotor current is achieved, and rotor speed is controlled; after the rotor speed reaches a preset value, the corresponding period grid-connected control is conducted, the decline of stator current is controlled; after the rotor voltage amplitude, the frequency and the phase meet the requirements, stator sides and a grid contact device are switched; the scheme does not need the static frequency device and other additional starting devices, while having a high degree of control precision and reliability.

The invention discloses a motor train unit ground loop electrical coupling effect coefficient calculating method. The motor train unit ground loop electrical coupling effect coefficient calculating method comprises the main steps of, firstly, according to traction network structures corresponding to different power supply manners, determining a train ground loop and the loops structured by different traction networks; secondly, calculating the magnetic chain of every traction network hoop, which is generated by current in a transmission conductor A and a return conductor B and is in mutual inductance with CD intersecting chains of the train ground loop; thirdly, calculating the electrical coupling coefficient of every traction network loop to the train group loop; lastly, superposing the calculating results to obtain the electric coupling effect coefficient of the entire traction network loop to the motor train unit ground loop. The motor train unit ground loop electrical coupling effect coefficient calculating method enhances the accuracy of train-network coupled modeling and is significant to train voltage fluctuation research, train ground circulation mechanism analysis and ground system optimization.

The invention discloses an automatic calibration method for a driving motor rack of a new energy automobile, which improves the rack calibration efficiency, enhances the calibration precision and reduces the labor intensity of a calibration engineer. According to the technical scheme, during matching of the rack of a driving motor of the new energy automobile, system resources of the rack are integrated; by automatic temperature returning control, automatic current setting and automatic data processing, motor control current can be automatically set, so that the precision of calibrating the motor rack is improved, and the motor rack calibration working efficiency is greatly improved. Particularly, the fluctuation of a magnetic chain of a rotor is reduced by controlling the temperature of the motor, a reading error is eliminated, and the precision of calibrating the motor control current is improved; therefore, an automatic procedure replaces frequent manual operation and visual inspection of the engineer, to realize continuous running and unattended operation, so that the working efficiency of motor rack calibration is greatly improved, and precious engineer resources are saved.

The invention relates to a method for suppressing low-speed oscillation of a hybrid stepping motor, which is characterized in that: according to feedback winding currents and given winding voltages existing in the micro-step control system of a hybrid stepping motor, adopting a magnetic chain estimator, a rotor torque estimator, a band-pass filter and a proportion regulator to effectively inhibit the given winding current phase angle modulation quantity in low-speed rotor oscillation, and then adopting a given winding current phase modulator and a closed-loop type winding current control mode to realize the real-time modulation of the actual winding current phase, thereby suppressing the low-speed rotor oscillation. The control method of the invention is applicable to both two-phase hybrid stepping motors and multi-phase hybrid stepping motors. Moreover, no additional speed or acceleration sensors, idling devices and the like are required, thereby reducing the cost of the stepping driver.

The invention relates to a control method for a variable excitation synchronous motor MTPA (Maximum Torque per Ampere) based on multi-line fitting, and provides a multi-line fitting method for a rectangular axis current solving module in a control structure drawing. An excitation magnetic chain is discretized in the variable scope; and then under each specific excitation magnetic chain, an electromagnetic torque is used as a single argument to carry out the quadratic polynomial fitting of a rectangular axis current solving function, and then a plurality of fitting curves under different excitation magnetic chains can be obtained. When the system runs, at the excitation magnetic chain at one moment, two closest fitting curves are selected firstly to carry out the current calculation of the rectangular axis respectively; then based on the two sets of values, the size of the excitation magnetic chain at the moment is used as a node to carry out linear interpolation, and the set value of the current value of the rectangular axis at the moment can be obtained; and finally, the control of the current ratio of the maximum torque of the variable excitation synchronous machine is completed.

The invention discloses a single-phase transformer model for calculating direct current magnetic bias through an equivalent differential electric / magnetic path principle. The single-phase transformer model is implemented through the following steps: a, establishing a circuit model based on a single-phase transformer iron core topological structure and transformer parameters; b, establishing a differential magnetic path model based on a differential magnetic path principle; c, deriving a relational expression among an iron core differential magnetic flux, a differential magnetomotive force, a magnetic chain and a loop differential magnetic flux based on a transformer differential magnetic path model; d, deriving a differential inductance matrix based on conclusions obtained by the steps a, b and c; e, establishing a single-phase transformer group circuit model based on a single-phase transformer winding connecting form and a differential pole matrix; f, solving a transformer differential circuit equation group based on a numerical algorithm, and solving a target variable; g, verifying the credibility of the model. According to the single-phase transformer model, the distortion degree of transformer excitation current and primary and secondary winding current during the invasion of different direct current quantities can be accurately obtained, the safe operation of an alternating current-direct current hybrid power grid is ensured, and the economic rationality of equipment selection is effectively guaranteed.

The present invention discloses a series quasi Z source inverter based grid-tied PV control method. A PV battery inverter system is seen as a virtual synchronous generator, and an integral of an output voltage of a series quasi Z source inverter is taken as a virtual motor magnetic chain. An outer ring is controlled by using a power ring, so that active power transmission and reactive power compensation are realized. An inner ring is a current ring, so that current rapid tracking is realized. PI modulation is performed on the current inner ring, so as to generate a modulated wave signal. Three times of harmonic wave modulation is performed on a modulated signal obtained at a PV side and the modulated wave signal. On and off of an inverter bridge are controlled, so as to realize power adjustment of the grid-tied PV system. According to the method, a virtual synchronous generator quasi direct power control policy is adopted for controlling the system, the virtual magnetic chain directly orients, an alternating current voltage sensor is omitted, system reliability is improved, device cost is saved, quasi direct power control can directly control active power and reactive power of the grid-tied inverter, and the system has the advantages of simple structure and good dynamic response performance.

The invention relates to a determination and adjustment method for high-slip motor-driven beam-pumping unit balance. The method comprises the steps: a magnetic linkage observation method of a motor is utilized for calculating the rotating speed of a pumping unit motor, dynamic analysis of the pumping unit is combined, and further motion law of a pumping unit crank is obtained; coupling relationship is relieved between a crank motion equation and a wave equation of a sucker rod string, kinematical analysis and dynamical analysis can be carried out on a pumping unit hanging point respectively, the speed, acceleration and displacement of the pumping unit hanging point and load of the hanging point are respectively calculated, torque of the pumping unit crank is calculated, the maximum torques of up stroke and down stroke are compared, and the ratio of the maximum torques is taken as a determination basis for the walking beam balance. The method provided by the invention is high in accuracy and strong in anti-interference performance.

A method for preparing a magnetic chain structure is provided. The method comprises providing a plurality of magnetic particles; dispersing the plurality of magnetic particles in a solution comprisinga dopamine-based material to form a reaction mixture; applying a magnetic field across the reaction mixture to align the magnetic particles in the reaction mixture; and polymerizing the dopamine-based material on the aligned magnetic particles to obtain the magnetic chain structure. A magnetic chain structure prepared by the method is also provided.

The invention discloses a magnetic pretreatment device for a rolled emulsion. The magnetic pretreatment device comprises a cylindrical pretreatment box, wherein a liquid inlet on the sidewall of the lower part of the pretreatment box is connected to an emulsion outlet of an emulsion recycling box; a liquid outlet on the sidewall of the upper part of the pretreatment box is connected to a filtered liquid inlet of a magnetic chain filtering device; a top cover is arranged at the top part of the pretreatment box; an adsorption magnetic bar which extends to the bottom of the inner cavity of the pretreatment box is suspended at the inner side of the top cover; the adsorption magnetic bar penetrates through a slag scraper which is fixed in the inner cavity of the pretreatment box; and a slag discharge hole is arranged at the bottom of the pretreatment box. As the magnetic pretreatment device is arranged between the magnetic chain filtering device and the rolled emulsion recycling box, most suspended residual iron particles are statically deposited; and as the flow speed is relatively fast, the rising iron powdery particles are driven to be adsorbed and deposited by the adsorption magnetic bar in the pretreatment box. The magnetic pretreatment device for the rolled emulsion has a simple structure, and reduces workload of a magnetic chain and a scraper, and the maintenance cost as most iron substances are removed from the emulsion after being treated by the device.

The invention is suitable for the field of motors, and discloses a rotor and a motor. The rotor comprises a rotor core, a rotating shaft passing through the center of the rotor core, and a plurality of magnet steels which are embedded in the rotor core at intervals in a circumferential direction. The rotor core is provided with a plurality of magnet steel grooves which are used for the storage and positioning of the plurality of magnet steels. Each magnet steel is provided with an inner end close to the rotating shaft, and an outer end far from the rotating shaft. The rotor core is also provided with a plurality of outer magnetic bridge gaps which extend from the edge of the rotor core to the outer ends of the magnet steels in a concave manner. The rotor gets rid of a magnetic isolation sleeve, thereby effectively simplifying the structure of the rotor and the assembly technology of the rotor. Meanwhile, the outer edge of the rotor core is additionally provided with the outer magnetic bridge gaps, thereby opening an outer magnetic bridge of the rotor core, enabling more magnetic chains of the magnet steels to pass through a stator winding linkage, reducing the magnetic leakage of the rotor, greatly improving the effective utilization rate of the magnetic flux of the rotor, and finally achieving a purpose of improving the output capability of the motor.

The invention discloses a magnetic chain coupling type memristor analog circuit with an adjustable coupling coefficient. The magnetic chain coupling type memristor analog circuit comprises two memristor simulators and a coupling resistor, wherein the memristor simulator is a magnetic chain control type memristor simulator, and the coupling resistor is a sliding resistor with continuously smooth adjustable level; and each memristor simulator comprises two suspension interfaces and at least one coupling interface, and access a variable directly proportional to an equivalent magnetic chain signal square value of the other memristor simulator through the coupling interface. The magnetic chain coupling type memristor analog circuit can not only express the dynamics and stable state properties of the single memristor, but also can simulate the magnetic chain coupling relation between more than two memristors, so as to research the magnetic chain coupling type memristor analog circuit from experiments and the characteristics of a series parallel dynamic circuit of other circuit elements; and the magnetic chain coupling type memristor analog circuit can be easily expanded to a multi-magnetic chain coupling type memristor analog circuit to replace the common resistors for application in the design and development of non-volatile memorys, neural network feedback systems and logic operation and other novel circuits and function circuits.

The present invention provides an umbrella-tooth double-shaft synchronously driving magnetic chain wheel running device, which relates to a device with four synchronously running driving devices which can be freely steered at 360 degrees at the surfaces of various objects. The device is characterized in that a steering shaft is located at the center of a driving shaft and is connected with the magnetic chain wheel by a steering bracket, so as to achieve the purpose of synchronous steering. The driving shaft and the steering shaft can turn while the centers are opposite. One end of the driving shaft is equipped with a synchronous wheel and a synchronous belt, and another end is provided with a level umbrella-tooth which meshes a vertical umbrella-tooth and then changes the level running to the vertical running and drives a magnet chain wheel unit by the manner of a driving chain wheel. The synchronous steering and the synchronous driving are respectively achieved synchronously by a motor through the synchronous wheel and the synchronous belt.

The invention relates to an implanting instrument capable of preventing gastroesophageal reflux. The implanting instrument comprises a magnetic chain and auxiliary lines, the magnetic chain comprises multiple magnetic devices, multiple connecting units and a lock catch device, each magnetic device comprises one or more annular magnets and a shell, and the internal circumferential face of each shell is an internal concave cambered surface; the adjacent magnetic devices are movably connected through one connecting unit, and each connecting unit comprises a connecting part and limiting parts arranged at the ends of the connecting part; the lock catch device comprises a first lock catch device body and a second lock catch device body, the magnetic chain is further provided with a starting magnetic device and a tail end magnetic device, the first lock catch device body and the second lock catch device body are arranged on a shell of the starting magnetic device and a shell of the tail end magnetic device respectively, and when the first lock catch device body and the second lock catch device body are combined, a closed annular magnetic chain ring is formed by the magnetic chain. According to the implanting instrument capable of preventing the gastroesophageal reflux, the design is reasonable, and the shape formed by connecting the magnetic chain in series is closer to a circle, so that the implanting instrument is more attached to the outer wall of esophagus after being implanted to the outer side of lower esophageal sphincter, and the effect of strengthening the LES through the instrument is exerted more sufficiently.

The invention discloses an optimized modeling method of a soft measuring instrument for a magnetic chain based on a least squares support vector machine during the stable suspended movement process of a bearingless asynchronous motor. The modeling method comprises the following two parts: modeling via the least squares support vector machine and the determination of an optimal model based on the improved particle swarm optimization. A soft measuring instrument model based on the least squares support vector machine is provided for the magnetic chain variable of the bearingless asynchronous motor difficult to measure in an online way, and the defects of low control accuracy and the like caused by time lag in the traditional offline measuring method can be well overcome. The modeling method has various advantages of automatic parameter optimization, high prediction accuracy, small sample demand size, strong anti-interference capability and the like.

The invention discloses a terahertz liquid crystal phase shifter based on magnetic nanoparticles and a preparation method thereof. The phase shifter disperses the magnetic fluid of Fe<3>O<4> magneticnanoparticle dispersion liquid into liquid crystal 5CB solvent at a normal temperature to form ferromagnetic liquid crystal, wherein the concentration ratio of the magnetic fluid of Fe<3>O<4> magneticnanoparticle dispersion liquid and the liquid crystal 5CB solvent is 0.05 wt%, and encapsulates the ferromagnetic liquid crystal into a non-oriented liquid crystal box with an interval of 1 mm by UVglue. The phase shifter utilizes the magnetic interaction between the magnetic chain formed by the Fe<3>O<4> magnetic nanoparticles under the action of an external magnetic field and the liquid crystal so as to achieve the initial anchoring orientation of the randomly arranged liquid crystal molecules in a thick liquid crystal box, so that the optical axis of the liquid crystal molecules can be deflected by 90 degrees only by changing the size of a magnetic field. Compared with the traditional liquid crystal phase shifting device based on magnetic control, the terahertz liquid crystal phase shifter based on magnetic nanoparticles does not need to change the direction of a magnetic field and require the pre-orientation of liquid crystal molecules, so that the practicability and the stability of the phase shifter are greatly improved. Thus, the phase shifter can be used in terahertz phase and polarization control devices and the like.

The invention provides a mechanical rotating type pulse magnetic field generator used for magneto-rheological polishing. The mechanical rotating type pulse magnetic field generator mainly comprises amagnet disc rotating mechanism and a magnet disc vertical direction adjusting mechanism. The magnet disc rotating mechanism comprises a driving motor, a rotating shaft, a motor support, a magnet discand a permanent magnet cluster. The permanent magnet cluster is fixedly installed on the magnet disc and generates a magnetic field required for polishing; the magnet disc is fixedly connected with the rotating shaft; the driving motor drives the rotating shaft to rotate, and the rotating shaft drives the magnet disc to rotate; and the magnet disc vertical direction adjusting mechanism is fixedlyconnected with the magnet disc and drives the magnet disc to move up and down. According to the mechanical rotating type pulse magnetic field generator, large-area polishing areas can be evenly formed; by rotating the magnet disc, the static magnetic field is converted into a dynamic pulse magnetic field; and a magnetic chain in a flexible polishing head can be forced to be rearranged so as to achieve rapid regenerating of abrasive particles, the contact frequency of the abrasive particles and the surface of a workpiece is increased, the abrasion speed of the abrasive particles is reduced, andthe polishing efficiency is improved.

The invention discloses characteristic value analysis model and step for the subsynchronous resonance analysis of a multi-machine power system, relating to the field of characteristic value analysis models of the subsynchronous resonance analysis of the power system. The deducing and calculating process of a method comprises the following step of: respectively writing a rotor motion equation of amultimass block model of a shaft system of a steam turbine generator, an electromagnetic transient state equation of a magnetic chain and the voltage of a generator, an electromagnetic transient state equation of a power transmission line, an electromagnetic transient state equation of a series-connected compensation capacitor and a control system equation of an excitation controller and the like. The invention obtains a differential equation set related to a state quantity by linearizing the equations on a stable-state operating point and can solve the characteristic value and the characteristic vector of a state equation coefficient matrix on the basis, obtain much information related to resonance damping characteristics by judging the stability of the subsynchronous resonance of the multi-machine power system and can be used for designing a controller to inhibit the subsynchronous resonance of the multi-machine power system by combining with a control theory.