CN114290083B - Air static pressure spindle based on double-wedge-shaped motor and control method thereof - Google Patents
Air static pressure spindle based on double-wedge-shaped motor and control method thereof Download PDFInfo
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- CN114290083B CN114290083B CN202111501740.XA CN202111501740A CN114290083B CN 114290083 B CN114290083 B CN 114290083B CN 202111501740 A CN202111501740 A CN 202111501740A CN 114290083 B CN114290083 B CN 114290083B
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Abstract
The application belongs to the technical field of machine tools, and particularly relates to an air static pressure spindle based on a double-wedge-shaped motor and a control method thereof. Wherein the air static pressure main shaft includes: the spindle comprises a machine shell, a cooling assembly arranged on the inner wall of the machine shell, a spindle body arranged in the machine shell, a radial air bearing assembly and a radial-axial composite air bearing assembly which are sleeved at the upper end and the lower end of the spindle body, and a double-wedge permanent magnet motor which is arranged in the middle of the spindle body and is coaxial with the spindle body, wherein the spindle body can rotate under the drive of the double-wedge permanent magnet motor, the double-wedge permanent magnet motor is symmetrical about the radial section of the spindle body, and each wedge permanent magnet motor comprises a rotor provided with a wedge permanent magnet magnetic pole and a stator core which is wedge-shaped. The electric spindle can dynamically adjust the output power of the electric spindle and simultaneously can control the axial magnetic tension in a follow-up manner, and is used for offsetting the axial impact load of the electric spindle, so that the axial bearing capacity of the air static pressure electric spindle is effectively improved, and the safety is high.
Description
Technical Field
The application belongs to the technical field of machine tools, and particularly relates to an air static pressure spindle based on a double-wedge-shaped motor and a control method thereof.
Background
The working performance of an industrial machine tool mainly depends on an electric spindle, a feeding system, a control system and the like, wherein the electric spindle is a core component of the machine tool, and the quality of the performance of the electric spindle determines the machining precision and the production efficiency of the machine tool. The air static pressure spindle adopts an air floatation support mode, has the advantages of small friction, low bearing heating, stable motion, high precision, long service life, small vibration and the like, and is widely applied to ultra-precise manufacturing equipment in the fields of aviation, aerospace, medical treatment, 3C and the like. However, the air bearing has small bearing capacity and low rigidity, and is easy to generate phenomena such as air hammer vibration, whirling and the like, so that the air static pressure electric spindle has the defects of poor anti-interference and impact resistance and the like; especially, in the case of a surface grinding machine or a rotary hole, axial movement of the electric spindle is caused due to all uncertain factors, and mutual friction of the moving stator and the stator of the thrust bearing, even locking and burning of the electric spindle, may be caused.
Therefore, the improvement of the axial bearing force and the rigidity of the aerostatic bearing is valued. At present, the most direct method for improving the rigidity of the air film is to improve the air pressure of the external air supply, but the method easily causes the leakage of an air pump, and the safety is greatly reduced. In addition, the gas film rigidity can be indirectly improved by other means, for example, the gas film pressure distribution is optimized by optimizing core parameters such as the diameter of a throttling hole, the number of throttling holes, the configuration of the gas film, the thickness of the gas film and the like, but the optimization effect is limited.
Disclosure of Invention
Technical problem to be solved
In view of the above disadvantages and shortcomings of the prior art, the present application provides an air static pressure spindle based on a double wedge motor and a control method thereof.
(II) technical scheme
In order to achieve the purpose, the following technical scheme is adopted in the application:
in a first aspect, an embodiment of the present application provides an aerostatic motorized spindle based on a double-wedge motor, including:
a machine shell, a first cover plate and a second cover plate,
a cooling assembly disposed on an inner wall of the housing,
a main shaft body arranged in the machine shell,
a radial air bearing assembly and a radial-axial composite air bearing assembly sleeved at the upper end and the lower end of the main shaft body,
the double-wedge permanent magnet motor is arranged in the middle of the main shaft body and coaxial with the main shaft body, the main shaft body can rotate under the driving of the double-wedge permanent magnet motor, the double-wedge permanent magnet motor is symmetrical about the radial section of the main shaft body, and each wedge permanent magnet motor comprises a rotor provided with a wedge permanent magnet magnetic pole and a stator, wherein a stator core of the rotor is wedge-shaped.
Optionally, the main shaft body is composed of a mandrel and a thrust plate, the mandrel is made of a titanium alloy material, and the surface of the bearing position of the mandrel is hardened by carburizing and gas multi-component co-infiltrating.
Optionally, the axial length of the wedge-shaped stator core of the stator is greater than the axial length of the rotor core of the rotor, and the difference between the axial length and the axial length is 1-3mm.
Optionally, a ratio ζ of an inner diameter to an outer diameter of the wedge-shaped stator core varies linearly along the axial direction, and a value of ζ ranges from 0.5 to 0.7.
Optionally, the tail end of the casing is fixedly provided with a base, and the front end of the casing is fixedly provided with a sealing end cover.
Optionally, a displacement sensor for monitoring axial displacement of the main shaft is arranged at the sealing end cover.
In a second aspect, an embodiment of the present application provides a method for controlling an aerostatic spindle, where the method is applied to a controller of an aerostatic spindle based on dual wedge motors according to any one of the above first aspects, where each wedge permanent magnet motor is a permanent magnet synchronous motor and is powered by an inverter respectively, and the method includes:
s10, acquiring an axial displacement signal of the electric spindle in real time through an axial displacement sensor, and obtaining an axial displacement deviation value based on the axial displacement signal;
s20, for each wedge-shaped permanent magnet motor, obtaining a quadrature axis current set value and a direct axis current set value by inquiring a pre-established torque-quadrature direct axis two-dimensional ammeter and an axial magnetic pull-quadrature direct axis two-dimensional ammeter based on the current target axial magnetic pull, a target torque and a rotor position angle obtained through real-time detection of a position sensor;
s30, calculating to obtain external output torque based on quadrature axis current signals acquired in real time respectively for each wedge-shaped permanent magnet motor, calculating a difference value between the target torque and the external output torque, and then obtaining quadrature axis current disturbance quantity through a proportional integral algorithm; calculating a difference value between a preset zero axial displacement deviation amount and the axial displacement deviation amount, and then obtaining a direct-axis current disturbance amount through a proportional-integral algorithm;
s40, aiming at each wedge-shaped permanent magnet motor, taking the sum of half of the quadrature axis current set value and half of the quadrature axis current disturbance amount as a quadrature axis current actual set value, taking the sum of the direct axis current set value and half of the direct axis current disturbance amount as a direct axis current actual set value, and obtaining a vector control signal of the inverter by a double closed-loop vector control method;
and S50, controlling the inverter to output three-phase current to the corresponding wedge-shaped permanent magnet motor based on the vector control signal.
Optionally, the torque-quadrature-direct axis two-dimensional ammeter and the axial magnetic tension-quadrature-direct axis two-dimensional ammeter are obtained by establishing a finite element model of the wedge-shaped permanent magnet motor for simulation, or are obtained by taking the wedge-shaped permanent magnet motor as an experimental object, obtaining experimental data through a motor calibration test, and then calculating.
Optionally, the method for calculating the external output torque includes:
wherein n is p Is the pole pair number psi of a wedge-shaped permanent magnet motor f The rotor flux linkage of the wedge-shaped permanent magnet motor is shown, and Iq is quadrature axis current.
Optionally, each wedge-shaped permanent magnet motor generates an axial magnetic pulling force Fa, the axial magnetic pulling force direction is from a large wedge-shaped taper surface to a small wedge-shaped taper surface, and the magnitude of the axial magnetic pulling force is as follows:
wherein D is av The average diameter of the wedge-shaped permanent magnet motor rotor is alpha is a wedge-shaped permanent magnetAngle of magnetic pole of magnet with respect to axial direction, L efi The effective length of the wedge-shaped permanent magnet after the magnetic pole is axially divided into n equal parts, B δi The magnetic pole of the wedge-shaped permanent magnet is axially divided into n equal parts, and the air gap flux density is beta, wherein beta is an air gap wave form coefficient.
(III) advantageous effects
The beneficial effect of this application is: the application provides an air static pressure electricity main shaft based on two wedge motors includes: the cooling assembly is arranged on the inner wall of the machine shell, the main shaft body is arranged in the machine shell, the radial air bearing assembly and the radial-axial composite air bearing assembly are sleeved at the upper end and the lower end of the main shaft body, the two wedge-shaped permanent magnet motors are arranged in the middle of the main shaft body and coaxial with the main shaft body, the main shaft body can be driven by the wedge-shaped permanent magnet motors to rotate, the two wedge-shaped permanent magnet motors are symmetrical about the radial cross section of the main shaft body, and the wedge-shaped permanent magnet motors comprise rotors and stator cores which are provided with wedge-shaped permanent magnet magnetic poles, and the rotors and the stator cores are wedge-shaped stators. The electric spindle can also control axial magnetic tension in a follow-up manner while dynamically adjusting the output power of the electric spindle, and is used for offsetting axial impact load of the electric spindle, so that the axial bearing capacity of the air static pressure electric spindle is effectively improved, and the safety is high.
Furthermore, the titanium alloy is adopted as the material of the mandrel, so that the centrifugal force of high-speed rotation can be reduced, the rigidity of the main shaft can be improved, and the surface hardening treatment of the bearing position of the titanium alloy mandrel can be realized by the carburization and gas multi-component co-carburization method, so that the wear resistance of the contact surface can be improved.
In a second aspect, the application further provides a control method of the aerostatic motorized spindle, which is applied to the controller of the aerostatic motorized spindle based on the double-wedge motor, and the axial impact load of the motorized spindle is offset through an off-line table look-up control method of the motorized spindle adjusted by axial magnetic tension, so that the axial bearing capacity of the aerostatic motorized spindle is effectively improved.
Drawings
The application is described with the aid of the following figures:
FIG. 1 is a schematic structural diagram of an air static pressure spindle based on a double wedge motor according to an embodiment of the present application;
FIG. 2 is an enlarged view of a portion of the first wedge-shaped permanent magnet machine of FIG. 1;
FIG. 3 is a schematic diagram of a first wedge-shaped permanent magnet machine according to an embodiment of the present application;
FIG. 4 is a schematic view of the position of the mandrel surface in contact with a bearing in an embodiment of the present application;
FIG. 5 is a flow chart of a method for controlling an air static pressure spindle according to another embodiment of the present disclosure;
FIG. 6 is a schematic view of an electric spindle axial runout displacement in another embodiment of the present application;
fig. 7 is a schematic block diagram of a control system for an aerostatic motorized spindle according to another embodiment of the present application.
Description of the reference numerals:
1-shell, 2-cooling component, 21-cooling water channel liner, 22-cooling water channel, 3-main shaft body, 31-thrust plate, 311-thrust plate left end face, 312-thrust plate right end face, 32-mandrel, 4-radial air bearing assembly, 41-radial air bearing liner, 42-radial air bearing jacket, 5-radial-axial composite air bearing assembly, 51-radial-axial composite air bearing liner, 52-radial-axial composite air bearing jacket, 6-double wedge permanent magnet motor, 61-first wedge permanent magnet motor, 62-second wedge permanent magnet motor, 611-first wedge permanent magnet motor rotor, 6111-rotor core, 6112-wedge magnetic steel, 6113-magnetic steel jacket, 612-first wedge permanent magnet motor stator, 6121-wedge stator core, 6122-stator winding, 613-first wedge permanent magnet motor axial limit sleeve, 7-base, 8-sealed end cover, 81-gasket, and 9-displacement sensor.
Detailed Description
For a better understanding of the present invention, reference will now be made in detail to the present embodiments of the invention, which are illustrated in the accompanying drawings. It is to be understood that the specific examples described below are intended to be illustrative of the invention only and are not intended to be limiting. In addition, it should be noted that, in the case of no conflict, the embodiments and features in the embodiments in the present application may be combined with each other; for convenience of description, only portions related to the invention are shown in the drawings.
Fig. 1 is a structural schematic diagram of an air static pressure spindle based on a double wedge motor in an embodiment of the present application. As shown in fig. 1, the air static pressure spindle based on the double wedge motor of the present embodiment includes:
the machine shell 1 is provided with a plurality of air holes,
a cooling module 2 disposed on an inner wall of the cabinet 1,
a main shaft body 3 disposed in the housing 1,
a radial air bearing assembly 4 and a radial-axial composite air bearing assembly 5 which are sleeved at the upper end and the lower end of the main shaft body 3,
set up in main shaft body 3 middle part and with main shaft body 3 coaxial double wedge permanent-magnet machine 6, main shaft body 3 can rotate under double wedge permanent-magnet machine 6's drive, double wedge permanent-magnet machine 6 is symmetrical about main shaft body 3's radial cross-section, and every wedge permanent-magnet machine is wedge stator including installing rotor and the stator core of wedge permanent-magnet magnetic pole.
The electric spindle of the embodiment can offset the axial load and the axial impact load borne by the electric spindle by controlling the double-wedge permanent magnet motor while dynamically adjusting the output power of the electric spindle, greatly improves the bearing capacity and the axial impact resistance of the aerostatic thrust bearing under the condition of not changing the air supply pressure of the aerostatic bearing, and has higher safety.
For a better understanding of the present invention, the components of the electric spindle in the present embodiment will be described below.
In this embodiment, the cooling assembly 2 includes a cooling water flow passage 22 and a cooling water passage liner 21, the radial air bearing assembly 4 includes a radial air bearing liner 41 and a radial air bearing outer sleeve 42, and the radial-axial composite air bearing assembly 5 includes a radial-axial composite air bearing liner 51 and a radial-axial composite air bearing outer sleeve 52.
In this embodiment, the double-wedge permanent magnet motor 6 includes two identical wedge permanent magnet motors, namely a first wedge permanent magnet motor 61 and a second wedge permanent magnet motor 62, and each wedge permanent magnet motor is provided with a wedge-shaped stator and an axial limit sleeve, which are a rotor and a stator core of a wedge-shaped permanent magnet pole. Fig. 2 is a partial enlarged view of the first wedge-shaped permanent magnet motor in fig. 1, as shown in fig. 2, the first wedge-shaped permanent magnet motor rotor 611 includes a rotor core 6111, wedge-shaped magnetic steel 6112, and a magnetic steel sheath 6113, and the first wedge-shaped permanent magnet motor stator 612 includes a wedge-shaped stator core 6121 and a stator winding 6122. Since the two wedge-shaped permanent magnet motors have the same structure, the specific structure of the second wedge-shaped permanent magnet motor 62 in this embodiment is not described again; and the following description of the first wedge-shaped permanent magnet motor 61 also applies to the second wedge-shaped permanent magnet motor 62, which will not be described one by one.
The first wedge-shaped permanent magnet motor 61 and the second wedge-shaped permanent magnet motor 62 share the same spindle 32 and are connected in a mirror symmetry manner. The following describes the mounting method and specific structure of the stator and rotor by taking the first wedge-shaped permanent magnet motor 61 as an example.
The three-phase or multi-phase stator winding 6122 of the first wedge-shaped permanent magnet motor 61 is embedded in the wedge-shaped stator core 6121 with an open slot in a fractional slot concentrated or distributed short-distance mode, the whole three-phase or multi-phase stator winding 6122 is fixed with the wedge-shaped stator core 6121 in a glue pouring mode, the whole formed by the wedge-shaped stator core 6121 and the stator winding 6122 is installed on the inner ring of the electric spindle cooling water channel inner container 21 in an interference fit mode, and the axial installation position is fixed in a welding mode. The rotor core 6111 is mounted on the core shaft 32 in an interference fit manner, and similarly, the wedge-shaped magnetic steel 6112 and the magnetic steel sheath 6113 are sequentially mounted on the rotor core 6111 and the wedge-shaped magnetic steel 6112 in an interference fit manner, and the mounting positions of the rotor core 6111, the wedge-shaped magnetic steel 6112 and the magnetic steel sheath 6113 in the axial direction of the core shaft 32 are fixed by the axial limiting sleeve 613.
By respectively controlling each wedge-shaped permanent magnet motor in the double wedge-shaped permanent magnet motors 6, the output power of the electric spindle can be dynamically adjusted, and meanwhile, the axial magnetic pull force can be adjusted in a follow-up mode to offset the axial impact load of the electric spindle.
FIG. 3 shows a first embodiment of the present applicationIn fig. 3, di is the inner diameter of the wedge-shaped stator core, do is the outer diameter, ls is the axial length of the wedge-shaped stator core, lr is the axial length of the rotor core, α is the included angle of the wedge-shaped magnetic steel relative to the axial direction, and D is the included angle of the wedge-shaped magnetic steel relative to the axial direction av Is the average diameter of the rotor of the single wedge motor.
Referring to fig. 3, in this embodiment, the axial length of the wedge-shaped stator core of the stator 612 is greater than the axial length of the rotor core of the rotor 611, and the difference value between the two is 1-3mm, so that it can be ensured that the air gap magnetic density B δ i at the two axial ends of the wedge-shaped magnetic steel 612 does not change suddenly when the mandrel generates axial play.
For example, the axial length Ls of the wedge-shaped stator core is greater than the axial length Lr of the rotor core by a length Δ L, and the value of Δ L is 2.5mm. The expression of Δ L is:
ΔL＝Ls-Lr
referring to fig. 4, in this embodiment, a ratio ζ of an inner diameter to an outer diameter of the wedge-shaped stator core 6121 is linearly changed along the axial direction, and a value range of ζ is 0.5 to 0.7, so that the wedge-shaped permanent magnet motor can obtain better output performance.
For example, the size of the outer diameter Do of the wedge-shaped stator core 6121 does not change, while the size of the inner diameter Di of the wedge-shaped stator core 6121 changes linearly and the ratio ζ of the inner diameter Di to the outer diameter Do of the wedge-shaped stator core 6121 changes linearly along the axial direction, ζ can be referred to the following formula:
ζ＝Di/Do
wherein: di is the inner diameter of the wedge stator core at different axial positions.
In order to obtain better output performance of the wedge-shaped permanent magnet motor, the value of zeta is 0.55.
In this embodiment, the main shaft body 3 is composed of a thrust disk 31 and a mandrel 32, the mandrel is made of a titanium alloy material, and the surface of the bearing position of the mandrel is hardened by carburizing and gas multicomponent co-infiltrating. Fig. 4 is a schematic view of the position of the surface of the mandrel in contact with the bearing according to an embodiment of the present application, please refer to fig. 4, in which the dashed line portion is the mandrel, the mandrel is made of titanium alloy, and the position indicated by the thick solid line is the position of the surface of the mandrel in contact with the bearing.
The titanium alloy is adopted as the material of the mandrel 32, so that the centrifugal force and the inertia force of the high-speed rotation of the spindle part can be greatly reduced, the rigidity and the rotation precision of the spindle unit are improved, and the wear resistance of the rotor bearing position of the titanium alloy mandrel can be improved by carrying out surface hardening treatment on the bearing position by a carburizing and gas multicomponent co-infiltrating method.
In this embodiment, the base 7 is fixedly installed at the tail end of the casing 1, the end cover 8 is fixedly installed at the front end of the casing 1, and the gasket 81 is installed between the end cover 8 and the radial-axial composite air bearing assembly 5.
In this embodiment, a displacement sensor 9 for monitoring the axial displacement of the spindle is provided at the seal end cover 8. In particular, the displacement sensor 9 may be an axial capacitive displacement sensor, which may be mounted at the end closure 8 by a fixed bracket.
It should be noted that the displacement sensor 9 described above is merely an exemplary illustration, and does not constitute a specific limitation to the displacement sensor 9.
A second aspect of the present application provides a control method for an aerostatic spindle, which is applied to any one of the controllers for an aerostatic spindle based on dual wedge motors in the first aspect, where each wedge permanent magnet motor is a permanent magnet synchronous motor and is powered by an inverter respectively. FIG. 5 is a schematic flow chart of a control method for an air static pressure spindle according to another embodiment of the present application; as shown in fig. 5, the method includes:
s10, acquiring an axial displacement signal of the electric spindle through a displacement sensor, and obtaining an axial displacement deviation value based on the axial displacement signal;
s20, for each wedge-shaped permanent magnet motor, obtaining a quadrature-axis current set value and a direct-axis current set value by inquiring a pre-established torque-quadrature-direct-axis two-dimensional ammeter and an axial magnetic pull-quadrature-direct-axis two-dimensional ammeter based on the current target axial magnetic pull, target torque and a rotor position angle obtained by real-time detection of a position sensor;
s30, calculating to obtain an external output torque based on a quadrature axis current signal acquired in real time for each wedge-shaped permanent magnet motor, calculating a difference value between a target torque and the external output torque, and obtaining a quadrature axis current disturbance amount through a proportional-integral algorithm; calculating a difference value between a preset zero axial displacement deviation amount and an axial displacement deviation amount, and then obtaining a direct-axis current disturbance amount through a proportional-integral algorithm;
s40, aiming at each wedge-shaped permanent magnet motor, taking the sum of half of a quadrature axis current set value and a quadrature axis current disturbance amount as a quadrature axis current actual set value, taking the sum of a direct axis current set value and half of a direct axis current disturbance amount as a direct axis current actual set value, and obtaining a vector control signal of the inverter through a double closed loop vector control method;
and S50, controlling the inverter to output three-phase current to the corresponding wedge-shaped permanent magnet motor based on the vector control signal.
According to the control method of the air static pressure spindle, the axial load and the axial impact load borne by the spindle of the spindle are offset by means of the axial magnetic pull force generated when the air static pressure high-speed spindle works, the output power of the spindle can be dynamically adjusted, the axial impact load caused by sudden change of the operation condition of the spindle can be adjusted in a follow-up manner, and the axial bearing capacity and the axial impact resistance capacity of the air static pressure thrust bearing are greatly improved under the condition that the air supply pressure of the air static bearing is not changed; by adopting two wedge motors, the axial shock resistance and the stability of the motor can be stronger than those of a single motor.
In order to better understand the present invention, the steps in the present embodiment are explained below.
Fig. 6 is a schematic diagram of the axial runout displacement of the electric spindle according to another embodiment of the present application, as shown in fig. 6, Z1 is the axial gap between the left end face 311 of the thrust plate and the radial-axial compound air bearing, and Z2 is the axial gap between the right end face 312 of the thrust plate and the radial-axial compound air bearing. And calibrating the initial 0 position of the axial capacitance displacement sensor, namely the position of the axial center line of the thrust disc 31, wherein Z1= Z2=0. If axial runout occurs in the operation process of the electric spindle, the axial runout displacement delta Z is obtained through the measurement of the calibrated axial capacitance displacement sensor, and the calculation formula of the delta Z is as follows.
ΔZ＝Z1-Z2
In this embodiment S10, an axial displacement signal of the electric spindle is acquired by an axial capacitive displacement sensor with respect to the axial runout displacement.
In this embodiment S20, the torque-quadrature-direct axis two-dimensional ammeter and the axial magnetic pull-quadrature-direct axis two-dimensional ammeter are obtained by establishing a finite element model of each wedge-shaped permanent magnet motor for simulation, or are obtained by taking each wedge-shaped permanent magnet motor as an experimental object, obtaining experimental data through a motor calibration test, and then calculating.
In this embodiment S30, when three-phase or multi-phase current is applied to the three-phase or multi-phase stator winding for excitation, the wedge-shaped permanent magnet motor outputs torque T to the outside, and an axial magnetic pulling force Fa is generated. The method for calculating the external output torque T comprises the following steps:
wherein n is p Is the pole pair number psi of a wedge-shaped permanent magnet motor f The rotor flux linkage of the wedge-shaped permanent magnet motor is shown, and Iq is quadrature axis current.
Because two wedge permanent-magnet machine units have the same direction of rotation, the output is connected in series coaxially simultaneously, namely whole because the size of the electric main shaft output torque of two wedge permanent-magnet machine is 2T.
Each wedge-shaped permanent magnet motor generates axial magnetic pull force Fa, the axial magnetic pull force direction is that the large wedge-shaped cone surface points to the small wedge-shaped cone surface, and the size of the axial magnetic pull force Fa is as follows:
wherein D is av Is the average diameter of the wedge-shaped permanent magnet motor rotor, alpha is the included angle of the magnetic pole of the wedge-shaped permanent magnet relative to the axial direction, L efi The effective length of the wedge-shaped permanent magnet after the magnetic pole is axially divided into n equal parts, B δi The magnetic pole of the wedge-shaped permanent magnet is divided into n equal parts in the axial direction to form an air gap flux density, beta is an air gap wave form coefficient, and the value range of beta is 1.1-1.3.
Here, the wedge-shaped permanent magnet poles are the wedge-shaped magnetic steels in the present embodiment.
Because the two wedge-shaped permanent magnet motor units are symmetrically connected in a coaxial mirror manner, when the same current is introduced into each wedge-shaped permanent magnet motor unit for excitation, the double wedge-shaped permanent magnet motor consisting of the two wedge-shaped permanent magnet motor units can generate a pair of axial forces with equal magnitude and opposite directions, and the axial resultant force of the double wedge-shaped permanent magnet motor is 0; the output direction and the output magnitude of the axial force of the double-wedge permanent magnet motor can be dynamically adjusted by respectively controlling the current excitation of each wedge permanent magnet motor unit.
In this embodiment S40, the sum of the quadrature axis current set value and the quadrature axis current disturbance is used as the quadrature axis current actual set value, the sum of the direct axis current set value and the direct axis current disturbance is used as the direct axis current actual set value, and the SVPWM position control vector is output through the current loop and torque loop double closed loop control.
The method of the present embodiment is further described with reference to fig. 7.
It should be noted that the array table in fig. 7 includes a two-dimensional data table constructed according to finite element analysis results of the wedge-shaped permanent magnet motor or motor calibration test results, between the torque T and the quadrature-axis (q-axis) current Iq and between the torque T and the direct-axis (d-axis) current Id; and constructing a two-dimensional data table between the magnetic pulling force Fa and the d-q axis currents Id and Iq according to finite element analysis results or test results of the wedge-shaped permanent magnet motor. The three-dimensional graph in fig. 7 is generated by using Matlab software based on the output torque and Id, iq array table, and the axial magnetic pull force and Id, iq array table respectively under the corresponding coordinate systems.
Fig. 7 is a schematic block diagram of a control system of an aerostatic motorized spindle according to another embodiment of the present application, and as shown in fig. 7, when the motorized spindle operates normally, an axial displacement deviation Δ Z of the motorized spindle is obtained by an axial capacitance displacement sensor. The following description will be made for each direction in which the aerostatic motorized spindle receives a load.
When the air static pressure spindle is subjected to load in the axial negative direction: when the main shaft of the first wedge-shaped permanent magnet motor runs normally, the required motor passes
Obtaining d-axis and q-axis current given values respectively by off-line table look-up of three parameters of a position angle theta e obtained by the axial capacitance displacement sensor
Output q-axis current disturbance amount from torque disturbance controller 1
As a total q-axis current setpoint
Namely, it is
And d-axis and q-axis currents are subjected to double closed loop and Space Vector Pulse Width Modulation (SVPWM) and then output control signals of the inverter 1.
When the main shaft of the second wedge-shaped permanent magnet motor runs normally, the required motor passes
Obtaining d-axis and q-axis current given values respectively by off-line table look-up of three parameters of a position angle theta e obtained by the axial capacitance displacement sensor
Amount of disturbance of q-axis current with output of torque disturbance controller 2
As the sum of the total q-axis current setpoint
Namely, it is
The d-axis and q-axis currents are subjected to double closed loop vector control (SVPWM) and then output inverter 2 control signals.
When the air static pressure spindle is subjected to loads in the positive and negative directions of the spindle: when the main shaft of the first wedge-shaped permanent magnet motor runs normally, the required main shaft is passed
Obtaining d-axis and q-axis current set values respectively by off-line table look-up of three parameters of a position angle theta e obtained by the position sensor
Amount of disturbance of q-axis current with output of torque disturbance controller 1
As a total q-axis current setpoint
Namely, it is
And d-axis and q-axis currents are subjected to double closed loop vector control (SVPWM) and then output control signals of the inverter 1.
When the main shaft of the second wedge-shaped permanent magnet motor runs normally, the required motor passes
Obtaining d-axis and q-axis current given values respectively by off-line table look-up of three parameters of a position angle theta e obtained by the axial capacitance displacement sensor
Amount of disturbance of q-axis current with output of torque disturbance controller 2
As a total q-axis current setpoint
Namely that
The d-axis and q-axis currents are subjected to double closed loop vector control (SVPWM) and then output inverter 2 control signals. Finally, the output torque and the axial magnetic pull force of the electric spindle are dynamically adjusted.
It should be noted that in the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps not listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention can be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. The use of the terms first, second, third, etc. are used for convenience only and do not denote any order. These words are to be understood as part of the name of the component.
Furthermore, it should be noted that in the description of the present specification, the description of the term "one embodiment", "some embodiments", "examples", "specific examples" or "some examples", etc., means that a specific feature, structure, material or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, the claims should be construed to include preferred embodiments and all such variations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention should also include such modifications and variations.
Claims (9)
1. The control method of the air static pressure electric spindle is characterized in that the control method is applied to a controller of the air static pressure electric spindle based on double wedge-shaped motors, each wedge-shaped permanent magnet motor is a permanent magnet synchronous motor and is respectively powered by an inverter, and the air static pressure electric spindle comprises the following steps:
a machine shell, a first cover plate and a second cover plate,
a cooling assembly disposed on an inner wall of the housing,
a main shaft body arranged in the machine shell,
a radial air bearing assembly and a radial-axial composite air bearing assembly sleeved at the upper end and the lower end of the main shaft body,
the double-wedge permanent magnet motor is arranged in the middle of the main shaft body and is coaxial with the main shaft body, the main shaft body can rotate under the driving of the double-wedge permanent magnet motor, the double-wedge permanent magnet motor is symmetrical about the radial section of the main shaft body, and each wedge permanent magnet motor comprises a rotor provided with a wedge permanent magnet magnetic pole and a stator with a wedge-shaped stator iron core;
the method comprises the following steps:
s10, acquiring an axial displacement signal of the electric spindle in real time through an axial displacement sensor, and obtaining an axial displacement deviation value based on the axial displacement signal;
s20, for each wedge-shaped permanent magnet motor, obtaining a quadrature-axis current set value and a direct-axis current set value by inquiring a pre-established torque-quadrature-direct-axis two-dimensional ammeter and an axial magnetic pull-quadrature-direct-axis two-dimensional ammeter based on the current target axial magnetic pull, target torque and a rotor position angle obtained by real-time detection of a position sensor;
s30, calculating to obtain an external output torque based on quadrature axis current signals collected in real time for each wedge-shaped permanent magnet motor, calculating a difference value between the target torque and the external output torque, and obtaining a quadrature axis current disturbance amount through a proportional-integral algorithm; calculating a difference value between a preset zero axial displacement deviation amount and the axial displacement deviation amount, and then obtaining a direct-axis current disturbance amount through a proportional-integral algorithm;
s40, aiming at each wedge-shaped permanent magnet motor, taking the sum of half of the quadrature axis current set value and half of the quadrature axis current disturbance amount as a quadrature axis current actual set value, taking the sum of the direct axis current set value and half of the direct axis current disturbance amount as a direct axis current actual set value, and obtaining a vector control signal of the inverter by a double closed-loop vector control method;
and S50, controlling the inverter to output three-phase current to the corresponding wedge-shaped permanent magnet motor based on the vector control signal.
2. The method for controlling the aerostatic piezoelectric spindle according to claim 1, wherein the torque-quadrature-direct axis two-dimensional ammeter and the axial magnetic tension-quadrature-direct axis two-dimensional ammeter are obtained by establishing a finite element model of the wedge-shaped permanent magnet motor for simulation, or are obtained by taking the wedge-shaped permanent magnet motor as an experimental object, obtaining experimental data through a motor calibration test, and then calculating.
3. The control method of the air static electric spindle according to claim 1, wherein the method of calculating the external output torque is:
wherein n is p Is the pole pair number psi of a wedge-shaped permanent magnet motor f The rotor flux linkage of the wedge-shaped permanent magnet motor is adopted, and Iq is quadrature axis current.
4. The method for controlling the aerostatic piezoelectric spindle according to claim 1, wherein each wedge-shaped permanent magnet motor generates an axial magnetic pulling force Fa in a direction from a large wedge-shaped cone surface to a small wedge-shaped cone surface, and the magnitude of the axial magnetic pulling force is as follows:
wherein D is av The average diameter of the wedge-shaped permanent magnet motor rotor is defined as alpha, L, the included angle of the magnetic pole of the wedge-shaped permanent magnet relative to the axial direction efi The effective length of the wedge-shaped permanent magnet after the magnetic pole is divided into n equal parts in the axial direction, B δi The magnetic pole of the wedge-shaped permanent magnet is axially divided into n equal parts, and the air gap flux density is beta, wherein beta is an air gap wave form coefficient.
5. The method of claim 1, wherein the spindle body comprises a mandrel and a thrust disk, the mandrel is made of titanium alloy material, and the surface of the bearing seat of the mandrel is hardened by carburizing and gas multi-component co-infiltrating.
6. The method for controlling the air static electric spindle according to claim 1, wherein the axial length of the wedge-shaped stator core of the stator is greater than the axial length of the rotor core of the rotor, and the difference value between the axial length and the axial length is 1-3mm.
7. The method according to claim 1, wherein a ratio ζ of an inner diameter to an outer diameter of the wedge-shaped stator core linearly changes along an axial direction, and a value of ζ ranges from 0.5 to 0.7.
8. The method for controlling the air static electric spindle according to claim 1, wherein a base is fixedly installed at the tail end of the casing, and a sealing end cover is fixedly installed at the front end of the casing.
9. A method of controlling an aerostatic spindle according to claim 8, wherein a displacement sensor is provided at the end cap for monitoring axial displacement of the spindle.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104368829A (en) * | 2013-08-14 | 2015-02-25 | 东莞市科隆电机有限公司 | Motorized spindle of aerostatic bearing |
| CN105827155A (en) * | 2016-05-09 | 2016-08-03 | 江苏大学 | Magnetic suspension flywheel energy storage motor for electric car |
| CN205414429U (en) * | 2016-03-16 | 2016-08-03 | 沈阳工业大学 | Permanent magnetism synchronization electric main shaft structure of wedge air gap |
| CN214380578U (en) * | 2020-12-24 | 2021-10-08 | 潍柴动力股份有限公司 | Combined motor and wheel-side driving system |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104368829A (en) * | 2013-08-14 | 2015-02-25 | 东莞市科隆电机有限公司 | Motorized spindle of aerostatic bearing |
| CN205414429U (en) * | 2016-03-16 | 2016-08-03 | 沈阳工业大学 | Permanent magnetism synchronization electric main shaft structure of wedge air gap |
| CN105827155A (en) * | 2016-05-09 | 2016-08-03 | 江苏大学 | Magnetic suspension flywheel energy storage motor for electric car |
| CN214380578U (en) * | 2020-12-24 | 2021-10-08 | 潍柴动力股份有限公司 | Combined motor and wheel-side driving system |
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