CN102412763A - Permanent magnet bearing-free auto-suspension three-degree-of-freedom spherical motor and control method thereof - Google Patents

Abstract

The invention belongs to the technical field of design and control of motors and relates to a permanent magnet bearing-free auto-suspension three-degree-of-freedom spherical motor. The permanent magnet bearing-free auto-suspension three-degree-of-freedom spherical motor comprises a base, a spherical stator wall, stator coils and a rotor, wherein the rotor is positioned in the stator wall; the output shaft of the rotor extends out of an opening above the stator wall; the spherical motor is characterized in that: the stator coils have columnar ironless structures; three layers of stator coils are uniformly distributed along the equator of the spherical stator wall and wefts parallel to the equator and radially fixed on the spherical stator wall; permanent magnet poles are embedded on the surface of the rotor and divided into two layers, namely an upper layer and a lower layer, along the equator; the poles N and the poles S on each layer are staggered; and each stator coil is independently controlled by a driving circuit. The invention also provides a control method for the motor. By the motor and the control method thereof, controllability of a magnetic suspension force and bearing-free running of the motor are realized; furthermore, the movement characteristic of the motor and the flexibility of design of a motor control system are improved.

Description

Permanent magnetism does not have bearing from suspending three degree of freedom spherical motor and control method thereof

Technical field

The invention belongs to design of electrical motor and control technology field, relate to a kind of multi-degree of freedom spherical motor.

Background technology

Along with the progress of science and technology, the range of application of movement mechanism with multiple degrees of freedom is more and more wider.Traditional movement mechanism with multiple degrees of freedom is united realization by many single-degree-of-freedom motors, and mechanism is huge, transmission accuracy is low, control is difficult.Globular motor can be realized the rotor three degrees of freedom of movement, in high-precision control systems such as robot, nanometer workbench, be with a wide range of applications, and the permanent magnetism spherical motor also has that volume is less, torque density is than characteristics such as height.

Because particular structural and motion mode, the bracing or strutting arrangement of globular motor rotor also is different from common electric machine.In the organization plan of research, the supporting way of rotor mainly adopts following mode before: directly contact, multi-directional ball bearing, oscillating bearing, air bearing etc.All there are some problems in these ways of contact; In the direct way of contact; Rotor directly is placed on stator inner wall or the slip ring; Though adopt the coating of low-friction coefficient to reduce sliding friction, friction torque still can exert an influence to the motion of rotor, as involved in the patent 200810053083.5; The multi-directional ball bearing utilizes rolling friction to replace sliding friction, though reduced friction torque, because bearing and rotor are to contact, pressure is bigger, might damage rotor surface; Oscillating bearing can be realized the three-degree-of-freedom motion of rotor preferably, but this bearing relatively is fit to the low-speed motion of motor; Air bearing can realize noncontact between the rotor, has reduced frictional force greatly, but needs extra air pressurization device.

Summary of the invention

The objective of the invention is to overcome the defective of existing globular motor rotor supports mode, propose a kind of three degree of freedom spherical motor that can prevent to produce between rotor and the stator frictional force.Technical scheme of the present invention is following:

A kind of permanent magnetism does not have bearing from suspending three degree of freedom spherical motor, comprises base, spherical stator wall, stator coil and rotor; Rotor is positioned at stator wall; Its output shaft stretches out from the opening part of stator wall top, it is characterized in that stator coil is that cylindricality does not have core construction; Equator along spherical stator wall reaches even the distribution 3 layers on the parallel parallel with the equator, is radial and is fixed on the spherical stator wall; Rotor surface is embedded with permanent magnet pole, and the magnetic pole edge is two-layer about being divided into the equator, and every layer the N utmost point and the S utmost point alternately distribute; Each stator coil is independently controlled by a drive circuit.

The control method that the present invention provides a kind of above-mentioned motor to adopt simultaneously comprises the following steps:

(1) utilizes displacement transducer and angular transducer detection rotor position, obtain stator coordinate system lower rotor part side-play amount and the Eulerian angles that turn over;

(2) utilize principle of coordinate transformation, the position coordinates of each stator coil is transformed under the rotor spherical coordinate system, and calculates the gas length between each stator coil and the rotor;

(3) calculate the electromagnetic force that produces when each stator coil leads to unitary current, and result of calculation is transformed into the stator rectangular coordinate system, and calculate the electromagnetic torque of electromagnetic force correspondence under rectangular coordinate system;

The driving torque of required magnetic suspension force and output when (4) moving according to motor calculates the size and Orientation of each coil current;

(5) electric current of obtaining according to the last step is controlled the size and Orientation of the electric current of each coil in real time, makes rotor be suspended in settling position and exports required torque.

The present invention proposes be a kind of no bearing from suspending three degree of freedom spherical motor and control method thereof, utilize radial electromagnetic force to produce support force, realized that the no bearing of controlled and the motor of magnetic suspension force moves; The electromagnetic torque that utilizes the tangential electromagnetic force to produce drives rotor, realizes three-degree-of-freedom motion, has improved the kinetic characteristic of motor, has improved the flexibility of electric machine control system design.Particularly, beneficial effect is following:

1, but permanent magnetism does not have the multifreedom motion of bearing on the three degree of freedom spherical motor implementation space that suspends, and is applied to fields such as robot, precision instrument, can simplify the design of mechanical system greatly.

2, permanent magnetism do not have bearing from the globular motor that suspends realize rotor from Suspension Control, noncontact between the rotor has overcome the adverse effect of friction torque to motion control.

3, permanent magnetism does not have bearing utilizes the electromagnetic force of stator coil generation from the globular motor that suspends the synthetic magnetic suspension force of radial component, need not to add in addition servicing unit, has simplified electric machine structure.

4, because stator coil adopts no core construction, do not have coupling effect between the stator coil, each coil is independently controlled by a drive circuit, has simplified control system.

5, the stator winding coil press etc. longitude and etc. latitude evenly distribute, through direction and the size that the position and the number of control coil electric current and hot-wire coil can be regulated total electromagnetic torque, can obtain different torque-characteristics, satisfy the Different control requirement.

Description of drawings

Fig. 1 permanent magnetism does not have bearing from suspending the three degree of freedom spherical motor structure chart.

The label title is among the figure: 1 stator wall; 2 stator coils; 3 coil bolts; 4 ball rotors; 5 output shafts; 6 bases.

Fig. 2 rotor sphere structure figure.

The label title is among the figure: 41 permanent magnet poles

Fig. 3 control flow chart.

Fig. 4 rotor centre of sphere skew sketch map.

Electromagnetic force during Fig. 5 δ=1.5mm under the spherical spinner coordinate system

.(a) f _rComponent Component (c) f _θComponent.

Embodiment

Permanent magnetism does not have bearing and comprises support section, stator and spherical spinner transducer four parts from the three degree of freedom spherical motor that suspends, and wherein, support section comprises stator wall 1, and base 6, stator comprise air core coil 2, coil bolt (3), fixing output shaft 5 on the spherical spinner 4.Motor basic structure is as shown in Figure 1.Rotor surface is pasted permanent magnet pole 41, and magnetic pole is divided into two-layer up and down along the equator, every layer 6 utmost point, and each layer magnetic pole N, the S utmost point replace, and upper and lower two-layer magnetic pole N, the S utmost point are alternately.As shown in Figure 2.

Behind stator winding electrifying, the electromagnetic force that winding receives will comprise radial component and tangential component.The radial component of electromagnetic force does not produce electromagnetic torque, but it can make rotor produce offset, before the motor operation; Rotor is supported on the support on the base, and after the energising, displacement transducer can detect rotor-position; Controller is regulated the electric current of each coil; The rotor of making a concerted effort to hold up of the electromagnetic force that each coil produces, to the overlap position of the rotor centre of sphere with the stator centre of sphere, the position when this position is the motor stabilizing operation.During the motor operation, in case rotor-position skew stable operation position, displacement transducer feeds back to control system with side-play amount, angular transducer with the Eulerian angles that rotor turns over, and controller is made corresponding adjustment, makes rotor be returned to settling position.On the other hand, the tangential component of electromagnetic force produces electromagnetic torque and drives the rotor rotation, and controller is regulated the torque component of each coil current, produces needed electromagnetic torque driving rotor and goes off course, tilts and rotatablely move.Because it is unsaturated that permanent magnetism does not have bearing magnetic circuit in the globular motor that suspends, the electromagnetic force component and the torque component of electric current can independently be controlled.Control flow chart is as shown in Figure 3.Concrete control method is:

1. before the motor operation, stator coil contacts with rotor, and provides support power.When motor normally moved, rotor overlapped with the stator centre of sphere, and this position is the settling position of spherical spinner.In case squint in the running, as shown in Figure 5, rotor centre of sphere initial point is O, becomes O after squinting ₁, side-play amount is OO ₁R representes with the vector Δ, and the sensor rotor-position obtains Eulerian angles α, β and γ that rotor displacement amount Δ r and rotor turn over.

2. utilize principle of coordinate transformation, the position coordinates of each coil of stator is transformed under the rotor spherical coordinate system.The position coordinates of each stator coil under the stator coordinate system is known, is confirmed by electric machine structure.If i stator coil is (X at the coordinate of stator coordinate system _i, Y _i, Z _i), the coordinate (x under the rotor rectangular coordinate system _i, y _i, z _i), then

(x _i，y _i，z _i)＝(X _i，Y _i，Z _i)*R(α，β，λ)*L ^-1 i＝1...24 (1)

Wherein R (α, beta, gamma) is an Eulerian angles rotation transformation matrix, and L is the translation matrix about Δ r, and subscript-1 is a matrix inversion operation, and subscript i representes the stator coil label.

Consider that permanent magnetism spherical magnetic field and torque analyze under spherical coordinate system usually, the position of this coil under the rotor spherical coordinate system can be expressed as

$\left(2\right)$

${\mathrm{\θ}}_i=2\mathrm{\π}-\arccos \frac{x_i}{\sqrt{x_i^2+y_i^2}}$

Distance between this coil and the rotor centre of sphere

$R_i=\sqrt{{(X_i-\mathrm{\Δx})}^2+{(Y_i-\mathrm{\Δy})}^2+{(Z_i-\mathrm{\Δz})}^2}---\left(3\right)$

Wherein [Δ x Δ y Δ z] is the component of Δ r under the stator rectangular coordinate system, obtained by displacement transducer.

Then gas length does between these coil stator and rotor

δ _i＝R _i-R _in (4)

R wherein _InBe rotor radius.

3. because stator winding is an air core coil; Air-gap field is mainly set up by rotor magnetic pole; Known each stator gas length between position under the rotor spherical coordinate system and rotor; According to the electromagnetic force model (obtaining through Finite Element Method or analytic method) of motor, can obtain stator coil is the rotor spherical coordinate system at electromagnetic force

reference coordinate that this position produces.Fig. 5 has provided under a rotor magnetic pole, and the rotor air gap is 1.5mm, when the stator coil electric current is 1A, several F of electromagnetic force under the rotor spherical coordinate system _rComponent,

Component and F _θRelation between component and the coil position.

4. utilize coordinate transform, can obtain the component of electromagnetic force under the rotor rectangular coordinate system

Wherein subscript T is the matrix transpose computing, and transformation matrix T does

Therefore, the torque that this stator coil produces under the rotor rectangular coordinate system can be expressed as

M _i(x，y，z)＝[x _i，y _i，z _i]×[F _i，x，F _i，y，F _i，z](6)

5. consider that permanent magnetism does not have bearing in the globular motor that suspends, magnetic suspension force is represented more convenient under the stator rectangular coordinate system, and the electromagnetic force that therefore coil is produced is transformed under the stator rectangular coordinate system, is expressed as

6. repeating step 1-5, in the time of can obtaining all 24 coils through unitary current, the electromagnetic force of generation and electromagnetic torque.

7. in the permanent magnetism spherical motor, stator magnetic circuit is unsaturated, and the electromagnetic force that stator coil produces is linear with the electric current that passes through.Electromagnetic force that 24 coils are produced during through unitary current and electromagnetic torque are formed moment battle array F and torque matrix M (being the matrix of 3*24); And 24 coil currents are formed current vector I, can capable matrix F, torque matrix M current vector I and need the suspending power vector [F that produces _XF _YF _Z], electromagnetic torque [M _xM _yM _z] between satisfy relation

[F _X，F _Y，F _Z] ^T＝F(X，Y，Z)·I _F

[M _x，M _y，M _z] ^T＝M(X，Y，Z)·I _M (8)

I wherein _FBe control suspension component of force in the coil current, I _MComponent for controlling torque.

8. can draw I by formula (8) _FAnd I _M

I _F＝F ^-1(X，Y，Z)·[F _X，F _Y，F _Z] ^T

I _M＝M ^-1(X，Y，Z)·[M _x，M _y，M _z] ^T (9)

F wherein ^-1And M ^-1Generalized inverse matrix for F and M.Therefore, the coil current vector does

I＝I _F+I _M (10)

9. there is not bearing in the globular motor that suspends at permanent magnetism; Each stator coil all connects independently H bridge type main circuit; The control strategy ring control that adopt to stagnate, the coil current I that will be obtained by formula (10) electric current as a reference is input in the hysteresis comparator, the opening and turn-offing of the switching signal control main circuit power tube that draws; Make the given reference current of current tracking of stator coil, finally realize motor from suspending stabilized operation.

Claims (2)

1. a permanent magnetism does not have bearing from suspending three degree of freedom spherical motor, comprises base, spherical stator wall, stator coil and rotor; Rotor is positioned at stator wall; Its output shaft stretches out from the opening part of stator wall top, it is characterized in that stator coil is that cylindricality does not have core construction; Equator along spherical stator wall reaches even the distribution 3 layers on the parallel parallel with the equator, is radial and is fixed on the spherical stator wall; Rotor surface is embedded with permanent magnet pole, and the magnetic pole edge is two-layer about being divided into the equator, and every layer the N utmost point and the S utmost point alternately distribute; Each stator coil is independently controlled by a drive circuit.

2. the control method that the described motor of claim 1 adopts is characterized in that, comprises the following steps:

(1) utilizes displacement transducer and angular transducer detection rotor position, obtain stator coordinate system lower rotor part side-play amount and the Eulerian angles that turn over;

(2) utilize principle of coordinate transformation, the position coordinates of each stator coil is transformed under the rotor spherical coordinate system, and calculates the gas length between each stator coil and the rotor;

(3) calculate the electromagnetic force that produces when each stator coil leads to unitary current, and result of calculation is transformed into the stator rectangular coordinate system, and calculate the electromagnetic torque of electromagnetic force correspondence under rectangular coordinate system;

The driving torque of required magnetic suspension force and output when (4) moving according to motor calculates the size and Orientation of each coil current;

(5) electric current of obtaining according to the last step is controlled the size and Orientation of the electric current of each coil in real time, makes rotor be suspended in settling position and exports required torque.

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