The bearingless motor is a combination of an electromagnetic bearing and an AC motor. It inserts an electromagnetic bearing winding that generates a radial magnetic levitation force into an armature core of a rotating electric machine, so that the motor rotor has both the ability to rotate and self-suspend support. It has solved the theoretical basis and technical key of realizing high-speed and large-capacity motors at the same time, and has opened up wider application prospects than electromagnetic bearings. In order to achieve a stable suspension of the rotor, it is necessary to effectively control the radial magnetic levitation force, but there is a coupling between the levitation force and the electromagnetic torque, and between the vertical and horizontal levitation forces. Because the magnetic levitation force is the result of the active imbalance of the air-gap field generated by the torque winding and the suspension winding of the bearingless motor, it is necessary to use the air-gap field oriented control to achieve the solution fee and ensure a stable suspension operation. Many domestic and foreign researchers have conducted research on air gap magnetic field orientation control of induction bearingless motors. This control method can achieve stable suspension of the rotor under load and dynamics, but it cannot achieve complete decoupling of the suspension force in both vertical directions. . Further analysis shows that complete decoupling of the levitation forces does not occur in the exact air-gap flux-orientation mode, but rather when the flux-vectors and the stator-flux vectors are oriented on a certain flux vector. This means that it is necessary to perform real-time correction of the amplitude and phase of the air gap flux vector. In this paper, a concept of a general-purpose field-oriented controller is proposed, which can set the position of the directional flux vector by setting the parameter 'V/' to adapt to any of the existing field-oriented control methods. Problems were raised, but these ideas were not used to constitute a complete decoupling solution for bearingless motors, and no analysis was performed on the effects of changes in rotor parameters and the nonlinear ferromagnetic saturation of motors. In order to deepen and achieve this decoupled control idea, this paper first establishes an air gap magnetic field orientation control model for induction bearingless motors, and performs stable suspension operation simulation. For actual conditions in which bearingless motors actually exist in ferromagnetic non-linear saturation, large dynamic and overloaded rotor parameters, this paper points out that it is necessary to modify the amplitude and phase of the directional air gap flux linkage through nonlinear modeling and simulation. Then, a novel dynamic solution for cost control to optimize air gap magnetic field orientation is proposed. At the same time, the structure of the optimized air gap magnetic field orientation control system based on the universal magnetic field orientation controller is proposed, and the realization technology of tracking and dynamic adjustment of the orientation magnetic flux vector during operation is solved, and the nonlinear dynamic required for the stable suspension of the induction type bearingless motor is solved. Decoupling control provides an implementation path. 2 Air gap magnetic field directional control 2.1 Overview The schematic diagram of the magnetic suspension force generation principle of the induction type bearingless motor, wherein 1 and 4 are 4-pole torque windings, and 2-pole suspension windings. If the corresponding current is supplied to each winding according to the polarity shown in the figure, the two-pole magnetic field will be superimposed with the four-pole magnetic field, so that the magnetic density of the air gap in the area 1 increases, the magnetic density of the air gap in the area 2 decreases, and the magnetic suspension force of the uneven bearingless motor is generated. The magnetic flux density of the air gap in the principle diagram makes the rotor of the motor withstand the magnetic levitation force along the direction, which causes the rotor to float. In order to realize the precise control of the levitation force, the key is to establish the air gap magnetic field orientation control model that realizes the decoupling of the bearingless motor system, including the levitation force model and the torque model. 2.2 Suspension force model According to the text, without considering the influence of rotor eccentricity, the induction bearingless motor is magnetically levitated in the horizontal and vertical orthogonal directions under the air gap magnetic field orientation. Can be expressed as a 4-pole air-gap field and torque winding cross-linked flux chain; i4, the magnetizing inductance of the torque winding, /.4, the torque winding excitation current amplitude;/2l/,/2l/respectively For the suspension winding at the synchronous speed What is the component current in the coordinate system; r is the outer diameter of the rotor; / is the length of the effective iron core of the motor; call and place are the effective number of turns per phase of the torque winding and the suspended winding respectively; Ge is the average air gap length. It can be seen that under the air-gap field orientation condition, the component current of the suspended winding can independently control the magnetic levitation force in two perpendicular directions. In this way, the levitation force value can be generated by detecting the rotor displacement in the bearingless motor levitation control, and then the current of the levitation winding can be calculated according to the following formula. 2.3 Torque model Synchronous speed What type of induction bearingless motor torque is represented in the 9 coordinate system? The winding voltage equation is the mutual inductance with the rotor; (1) is the power supply angular frequency; it is called the rotational speed angular frequency; D=d/d/ is the differential operator. What are the three-axis component of the torque winding? *V, / is the stator and rotor quantity. The air-gap flux linkage produced by the torque winding can be expressed as substituting the formula (6) into the third and fourth rows of the formula (3) under the condition of the air-gap magnetic field orientation, respectively, yielding /2=i2-M; 2;=i,. /i,. Is the rotor time constant; (=out-called slip angle frequency, = motor torque equation is taken into account in Equation (6) = universal D屮', then Us can be seen in air-gap field oriented conditions, adjusting the torque winding The g-axis current can independently control the electromagnetic torque and achieve the solution between the electromagnetic torque and the levitation force.The principle of the torque control under the air gap field orientation is as shown. Influencing, the air gap field-oriented magnetic field oriented vector control simulation was performed on the induction bearingless motor in the Appendix. The correctness of the analytical model (1) of magnetic levitation force has been analyzed and verified by finite element analysis using ANSOFT, a special design software for electromagnetic field of the motor. It is the change of the direction displacement of the rotor in the no-load starting process of the bearingless motor. The initial air gap eccentricity is assumed to be AFA at rest; 0=O.3mm. It can be seen from (a) and (b) that the speed is “quick From the standstill to 1420r/min, the overshoot of rotation speed is less than 0.6%, and the steady-state error of the rotation speed is less than 0.3r/min. Under the control of air-gap magnetic field orientation, the rotor has stable suspension, and the displacement in the crucible direction is stable within ±60|im. . (c), (d) are the air gap flux amplitude and its phase %, respectively, and the phase angle refers to the phase deviation between the actual air gap flux linkage and the orientation air gap flux linkage. 3 Rotor parameters and influence of ferromagnetic saturation on levitation The above operation simulation is based on the ideal working condition of the bearingless motor, but in the acceleration, load or overload of the actual operation, the sudden increase of the load causes the motor slip to increase and the rotor circuit operating frequency increases. Ascending, the skin effect will make the rotor resistance increase, the rotor leakage inductance becomes smaller, the rotor current increases, resulting in increased motor saturation. The actual factors in these operations will affect the levitation performance in the dynamics of bearingless motors. When the rotor resistance increases 1.5 times, the rotor leakage inductance decreases by 20%, and the rotor time constant decreases by nearly half, the motor suddenly increases the displacement of the rotor in the direction of 5N+m rated load. After the load is found, the air gap magnetic field amplitude generated by the torque winding increases by 1.28 times, and the phase shift is 0.16 rad. That is, the actual air gap flux shifts to the direction of the rotor flux, destroying the original air gap magnetic field. Accurate orientation results in an increase in rotor displacement from ±60|jm to ±160|jm. In order to investigate the influence of ferromagnetic nonlinear saturation on the levitation performance, the air-gap flux density of the prototype is obtained through calculation of the electromagnetic field of ANSOFT software. Moment winding winding current nonlinear curve, rated operating point in the excitation current / 4, = 2.8A, air gap flux density 1.2T. According to this nonlinear relationship and the levitation force formula of equation (1), the a, direction levitation force expression is obtained. When the levitation winding current is increased, due to the effect of direct saturation, the air gap flux density increase decreases and the levitation decreases. Force is no longer proportional to current. The maximum levitation force appears at the excitation current /4, =2.8A. If the excitation current further increases, the levitation force will also decrease. The currents /4 of the excitation components of different torque windings are calculated, and the flux linkage of the air gap is affected by the torque component current /,. It can be seen that the air-gap flux linkage decreases with the increase of the torque component current /, and the rate of drop of the air-gap flux linkage becomes slower at larger excitation current /4. This is because the q-axis torque current is increased, the cross-saturation degree is further increased, so that in the same exciting component current, the air-gap flux linkage decreases with the torque component current, and the direction of the air-gap flux linkage is also It will change with the increase of the torque component current. Obviously, this will cause the magnetic levitation force to decrease and affect the stable operation of the motor. The relationship between the rotor levitation force F obtained by ANSOFT software, the fe component current of the torque winding /4m, and the levitation winding current/2. It can be seen that the ferromagnetic saturation in a bearingless motor is basically caused by two reasons: one is the direct action of the suspension winding current required to generate the suspension force, and the other is the indirect effect of the torque winding torque component current required to generate the torque. . Since the air gap magnetic field of the bearingless motor is mainly generated by the excitation component current in the torque winding, the indirect effect of the torque component current on saturation is actually a manifestation of the shaft cross saturation. In order to consider the influence of the magnetic field saturation of the above air gap into the levitation force model after considering the ferromagnetic non-linear saturation and the relationship between the flux component of the air gap flux and the torque component of the torque winding, the simulation of the effect of saturation on the rotor levitation can be performed. . When the load suddenly doubles from zero to lON.m, both the rotor direction displacement and the amplitude and phase of the air gap flux linkage change, as shown. It can be seen that due to the increase in enthalpy, the air gap magnetic field generated by the torque winding is saturated, the magnetic flux amplitude is reduced to 0.81 times the original, the phase shift is advanced by 0.15 rad, so that the air gap magnetic field cannot be accurately oriented, and the rotor gap flux linkage is oriented. Based on factors such as changes in rotor parameters, influence of motor ferromagnetic saturation, etc., the size and phase of air gap fluxes for orientation are corrected to find an optimized air gap field orientation method to ensure complete dynamic and overload conditions. Decoupled. 4 Optimized air gap magnetic field orientation control strategy This is a new type of dynamic orientation decoupling control that is different from standard air gap field orientation and requires a universal magnetic field orientation controller. General Field Oriented Controller Functional Block Diagram As shown in 0, the controller defines a coefficient ', / ', by selecting different values, you can flexibly select the orientation of the magnetic flux vector. Table 1 gives the different "values ​​corresponding to Flux vector. Using the concept of a general-purpose magnetic field director, it is possible to process changes in the amplitude and phase of the air-gap flux vector due to actual factors such as motor rotor parameter changes and magnetic saturation effects; by selecting an appropriate value, the magnetic flux of the controller is dynamically changed. Vector, realizing precise orientation after real-time correction of air gap flux. The law of the phase lead angle of the air-gap flux linkage is given when the rotor resistance and leakage inductance change, and the resistance and leakage inductance of each phase of the rotor are standard values. It can be seen that as the rotor resistance increases and leakage inductance decreases, the actual air-gap flux linkage in the motor will lag behind the selected flux linkage vector, ie, it is biased toward the direction of the rotor flux linkage, as shown in Table 2, J and 2 The relationship between the choice of the value of the universal magnetic field orientation controller and the phase angle of the magnetic flux linkage. At 1 o'clock, with the increase in the direction of the stator flux vector, the phase of the air gap flux chain becomes advanced. This lead angle can just be used to offset the air-gap flux chain phase shift caused by the parameter change, so that the air-gap magnetic field can be re-accurately oriented. 2 Values ​​and phase effects A similar approach can be used to correct the amplitude and phase of the airgap flux chains that affect ferromagnetic saturation. An optimized air gap field oriented control system for an induction bearingless motor that considers changes in rotor parameters and accounts for saturation effects is shown in 3. In the figure, the amplitude and phase corrections and the selection of the parameters of the universal field-oriented controller are achieved by using the air-gap flux linkage value and the measured values ​​obtained by the air gap flux observer. 3 Optimized Air Gap Field Oriented Control System Block Diagram According to the optimized magnetic field orientation control model of 3, the steady-state and dynamic simulation of the bearingless motor under overload conditions was carried out. Taking the rotor parameter change as an example, when the rotor resistance is increased by 1.5 times and the leakage inductance is reduced by 20%, the air gap flux linkage I// is relative to the flux linkage I//:. It will lag 5.16° (1). In order to correct this phase shift deviation, the universal magnetic field controller selects “=1.05. Since this change makes the air gap flux increase by 1.28 times, the air gap flux linkage is corrected when the amplitude is corrected. Will be reduced to the original 1/1.28. After this automatic correction simulation results as shown in 4. 4 Rotor time constant reduction, sudden increase in load when the magnetic field directional control simulation results of the gas barrier When the load from zero suddenly overloaded to lON.m, the saturation phenomenon is obvious, the optimized air gap magnetic field orientation control method after the correction of the rotor suspension performance, such as 5 shows. Because of the optimized air gap field oriented control, the dynamic correction of the air gap flux vector for orientation is realized, effectively eliminating the influence of actual parameters such as rotor parameter changes and ferromagnetic non-linear saturation on the suspension performance of the motor, realizing large dynamics, Dynamic decoupling of suspension force under overload. (5) The simulation results of optimized air gap field oriented control when ferromagnetic saturation is considered. 5 Conclusion The effects of magnetic saturation and saturation of the rotor parameters in the actual operation of the bearingless motor make the magnetic levitation force not completely relieved. The reason is that the air gap flux is used for orientation. The vector has the deviation of amplitude and phase. This article has carried on the thorough research and analysis to this phenomenon through the simulation, revealed the law inside. At the same time, based on the concept of general-purpose field-oriented controller in AC speed regulation technology, an optimized air-gap magnetic field oriented control strategy and its control system are proposed. Through the real-time correction of air-gap magnetic field amplitude and phase for orientation, inductive type is realized. The dynamic full decoupling control of the bearingless motor under dynamic and overload conditions enables the bearingless motor to obtain the ideal decoupling control of the suspension force and the stable rotor suspension operation under the actual operating conditions, providing an implementation approach for the actual system operation control. . Hebei Haiao Wire Mesh Products Co., Ltd. , https://www.haiaowiremeshfencing.com