Method and control apparatus for controlling an AC-machine

A method and apparatus for the control of an AC-machine is set forth with a special winding for the combined generation of a torque and of a transverse force in the machine. In this arrangement, the magnitude and direction of a transverse force acting on the rotor of an AC-machine is controlled via the current of a control winding of the machine. For this purpose, the magnitude and direction of a flux of the machine generated by a drive winding and also the torque-forming component of the drive current is detected. From these parameters, the desired value of the control current vector can be precisely calculated via a decoupling equation in a coordinate system which is rotating with the machine flux. Through vector rotation, through the flux angle and a constant angle, which takes into account of the position of the winding axes of the drive and control windings, the desired value of the control current vector can be transformed into the stator coordinate system of the control winding. The desired currents for the individual winding trains are determined as a result of this control current vector. These currents are impressed into the winding by a current feed apparatus.

BACKGROUND OF THE INVENTION 
1. Technical Field 
The invention relates to the field of drive and regulation technology. 
2. Description of the Prior Art 
The preconditions under which one-sided magnetic trains arise in electrical 
machines were already being investigated at the start of this century. 
There are for example described in the three-volume fundamental work by H. 
Sequenz "The Windings of Electrical Machines", Springer-Verlag Wien, 1950 
and also in the textbook by Th. Bodefeld and H. Sequenz, sixth edition, 
Springer-Verlag Wien, 1962. In accordance with Sequenz, one-sided magnetic 
tension forces only then arise when the resulting magnetic flux polygon is 
centrally asymmetric and is first closed after running around the entire 
armature circumference. The radial Maxwell forces distributed around the 
entire circumference do not cancel when the vector sum is taken so that a 
tensile force results. Two cases are described in the fundamental work by 
H. Sequenz which bring about a central asymmetry of the magnetic flux 
polygon: 
when the rotary fields of the stator or rotor contain harmonics whose pole 
pair differences relative to one another or relative to the fundamental 
wave are equal to one, 
when, in pole-reversible rotary field machines, two windings are operated 
whose pole pair difference is equal to one. 
For a long time one-sided magnetic trains were exclusively considered by 
electrical engineers as undesired disturbing forces and were counteracted 
by suitable measures. P. K. Hermann attempted for the first time to 
exploit one-sided magnetic trains acting in an electrical machine. In the 
German patent applications 
DE 24 57 084.1-32 Laying open print, 1974 
DE 24 06 790.1-32 Laying open print, 1975 
he describes a radial active magnetic bearing based on one-sided magnetic 
tensile forces. He proposes a control method in which two stator windings 
of an induction machine with a pole pair number difference of one is fed 
with three phase currents of the same frequency, with the feed current for 
the one winding, which is referred to in the following as the control 
winding, being derived by amplitude modulation from the feed current for 
the other winding, referred to in the following as the drive winding. The 
phase position between the currents of the two windings, referred to in 
the following as the control current and drive current, is matched by 
means of a phase adjusting device. 
A disadvantage of this control lies in the fact that the direction and the 
magnitude of the magnetic tensile force controlled via the control 
current, referred to in the following as the Maxwell transverse force, 
depends on the load state and on the speed of rotation of the machine. 
Furthermore, with the described control, the transverse Lorentz forces 
which likewise occur with the combination of two winding systems with a 
pole pair number difference of one are not taken into account. These can 
therefore make themselves felt as disturbing forces. 
A proposal to exploit these Lorentz transverse forces which occur with the 
combination of two winding systems with a pole pair number difference of 
one originates from J. Bichsel. In his dissertation "Contributions to the 
bearingless electric motor", ETH Zurich, 1990 and in the Swiss patent 
applications 
No. 04 049/90-2 patent application, 1990 
No. 04 050/90-2 patent application, 1990 
No. 04 051/90-0 patent application, 1990 
No. 04 052/90-2 patent application, 1990 
he describes magnetic bearing arrangements based on the action of the 
Lorentz transverse forces. He also describes a control method based on the 
principle of flux orientation for a synchronous machine, which makes it 
possible to adjust the magnitude and direction of a Lorentz transverse 
force independently of the operating point of the machine. A disadvantage 
of the control process lies in the fact that it does not take account of 
the Maxwell transverse forces. Moreover, the method cannot be transferred 
to an induction machine, since there no exploitable Lorentz transverse 
force can be generated. 
For the realization of the control method of the invention, the magnitude 
of the drive flux, the angle of the drive flux and the torque-forming 
stator drive current in the induction machine need to be known. Methods 
for the determination of these parameters are described extensively in the 
literature under the heading "Field Orientated Regulation or Control of 
the Synchronous Machine and the Asynchronous Machine". The fundamental 
principles of the field orientated control go back to F. Blaschke (The 
Method of Field Orientation for the Regulation of the Asynchronous 
Machine, Siemens Research and Development Report No. 1/72, Siemens AG, 
Erlangen, 1972 and The Method of the Field Orientation for the Regulation 
of the Induction Machine, Dissertation TU Braunschweig, 1974). A good 
overview of the various methods for the field oriented regulation of the 
asynchronous machine is offered by the dissertation by W. Zagelin (Speed 
Regulation of the Asynchronous Motor Using an Observer with Low Parameter 
Sensitivity, Dissertation, University of Erlangen, 1984). Examples for 
field orientated regulation systems of synchronous machines are to be 
found in Orik, B.: Regelung einer permanentmagneterregten Synchronmaschine 
mit einem Mikrorechner (Regulation of a Permanent Magnet Excited 
Synchronous Machine with a Microcomputer) in the journal 
Automatisierungstechnik at., year 33, issue 3/85; also in Schwarz, B.: 
Beitrage zu reaktionsschnellen und hochgenauen 
Drehstrompositioniersystemen (Contributions to Fast Reaction and Highly 
Precise Three-phase Current Position Systems), Dissertation, University of 
Stuttgart, 1986; and in Lobe, W.: Digitale Drehzahl- und Lageregelung 
eines Synchron-Servoantriebs mit selbsteinstellender Zustandsregelung 
(Digital Speed of Rotation and Position Regulation of a Synchronous 
Servo-Drive with Self-adjusting Status Regulation) etzArchiv, volume 11, 
issue 4/89. 
SUMMARY OF THE INVENTION 
The object of the present invention is to set forth a control method and a 
control means for an induction machine with a p.sub.1 pole-paired and a 
(p.sub.2 =p.sub.1 .+-.1) pole-paired winding for the formation of a 
transverse force vector acting on the rotor of the machine, wherein the 
above-named disadvantages of the prior art are avoided. In particular, the 
control process should take account of both of the transverse forces 
arising in the machine; the Maxwell transverse force and the Lorentz 
transverse force. The control process should moreover permit the exact 
control of the transverse force vector for each operating state of the 
machine. 
The method is based on the analysis of both of the magnetic transverse 
forces: the Maxwell transverse force and the Lorentz transverse force, 
acting in an electrical induction machine. 
Maxwell forces are forces which arise in a magnetic circuit at the boundary 
surfaces between materials of different permeabilities. In a machine with 
a ferro-magnetic rotor, the Maxwell forces act perpendicularly to the 
rotor. Since the sum of these forces cancel with a precisely centered 
arrangement of the rotor and with a sinusoidal distribution of the 
induction, no attention is normally paid to them at all. It is only when a 
displacement of the rotor away from the center or an asymmetrical 
induction distribution arises that a Maxwell transverse force results. A 
symmetry of the induction distribution of this kind can be achieved when a 
(p.sub.2 =p.sub.1 .+-.1) pole-paired likewise sinusoidally distributed 
magnetic control field is superimposed on the p.sub.1 pole-paired 
sinusoidally distributed magnetic drive field (see FIG. 1). The two 
magnetic fields can be described by flux vectors. .PHI..sub.1 points in 
direction of the maximum induction of the magnetic drive field and 
.PHI..sub.2 points in the direction of the maximum induction of the 
magnetic control field. The magnitude of the Maxwell transverse force is 
proportional to the product of the flux sizes. If the vectors are 
considered in their electrical planes (.PHI..sub.1 in the p.sub.1 
pole-paired system and .PHI..sub.2 in the p.sub.2 pole-paired system), 
then the direction of the Maxwell transverse force is only dependent on 
the relative position of the two flux vectors to one another. For the case 
of p.sub.2 =p.sub.1 .+-.1, the Maxwell transverse force vector points in 
the direction of the control flux vector .PHI..sub.2 relative to the drive 
flux vector .PHI..sub.1 (see FIG. 3). For the case p.sub.2 =p.sub.1 -1 the 
Maxwell transverse force vector must additionally be reflected at the 1- 
axis.(see FIG. 2). 
The control flux is proportional to the magnetization current in the 
control winding (magnetization current contribution of the control 
current). If it can be assumed that no p.sub.2 -pole-paired rotor current 
is flowing, then this is practically identical with the control current. 
Thus the transverse force can be directly set via the control current 
vector i.sub.S2.sup.(S,p2). The Maxwell transverse force can thus be 
described as a vector equation of i.sub.S2.sup.(S,p2) and .PHI..sub.1. In 
the practical handling of the equation it is simpler if the flux vector 
.psi..sub.1q.sup.(p1) which is linked with the p.sub.1 pole-paired drive 
winding is used in place of the drive flux vector .PHI..sub.1. 
The Maxwell transverse force is thus illustrated in vector components by 
the following equation. 
##EQU1## 
The selected vector component representation is based on the known and 
widely used vector illustration of the electrical machine (two-axes 
representation, dq-representation). With this type of representation, an 
m-phased machine with the pole pair number p is shown for the sake of 
simpler description by means of planar vectors on a two-phased substitute 
machine with the pole pair number 1. Since however two windings with a 
pole pair difference of 1 are necessary for the transverse force formation 
in an induction machine, and the geometrical current and flux 
distributions in the machine are of interest in contrast to the 
description of the torque formation, it is of importance for the 
description of the transverse force formation that the information 
concerning the geometrical winding distribution which is lost when 
representing the real machine on the substitute machine is replaced by a 
characterization of the plane of the representation and the definition of 
the position of the winding axes. Accordingly, the plane of the 
illustration is set out for all vector parameters (upper indices in 
brackets) in the following equations. The geometrical position of the 
windings is so defined that their d-axes coincide with the geometrical 
x-axis. The characterization of the phase numbers of the windings is not 
necessary because these do not have any influence on the geometrical 
current and flux distribution in the machine. 
Now it is known from the prior art that Lorentz transverse forces can 
likewise be generated in an induction machine. Lorentz forces are forces 
which act on a conductor through which current is flowing in a magnetic 
field. With a sinusoidal current and sinusoidal induction distribution in 
the machine, these forces act radially on the rotor and bring about a 
torque. Through a combination of a p.sub.1 pole-paired induction 
distribution and a (p.sub.2 =p.sub.1 .+-.1) pole-paired current 
distribution, it is now possible to generate a Lorentz transverse force 
(see FIG. 4). Analogously to the Maxwell transverse force, the Lorentz 
transverse force can be described by vectors. These are the current vector 
I and the flux vector .PHI.. The magnitude of the Lorentz transverse force 
is proportional to the product of the current and flux magnitudes. If the 
vectors are considered in their electrical planes, then the direction of 
the Lorentz transverse force is likewise dependent only on the relative 
position of the two vectors to one another. For the case p.sub.2 =p.sub.1 
+1, the Lorentz transverse force vector points directly in the direction 
of the current vector relative to the flux vector (see FIG. 6). For the 
case p.sub.2 =p.sub.1 -1, the Lorentz transverse force vector must 
additionally be reflected at the 2-axis (see FIG. 5). 
Analogously to the Maxwell transverse force, a Lorentz transverse force can 
thus be generated in the induction machine and depends on a drive flux and 
the control current. This is designated in the following as the useful 
Lorentz force and is defined by the following vector component equation: 
##EQU2## 
The prior art proposals of Bichsel for the generation of transverse force 
in the electrical machine are based on the exploitation of this useful 
Lorentz force. As, however, the control current in the control winding 
always also causes a control flux, the useful Lorentz force is always 
accompanied by a Lorentz transverse force which results from the control 
flux and the drive current. It is called a disturbing Lorentz force in the 
following because it weakens the desired useful Lorentz force depending on 
the type of construction of the machine and likewise contains 
uncontrollable components which are dependent on the torque-forming drive 
current. The disturbing Lorentz force is determined in accordance with the 
equation 
##EQU3## 
The above equations apply to any desired machine coordinate system. If now 
the above transverse force equations are represented in a coordinate 
system (F) which rotates with the argument of the drive flux vector 
.psi..sub.1.sup.(p1) measured in the p.sub.1 plane, then the transverse 
components of the drive flux .psi..sub.1q.sup.(p1) and thus the second 
term in the useful force equations disappears. In the case of the 
asynchronous machine, the first term of the Lorentz useful force equation 
and of the Lorentz disturbing force equation moreover cancel. In the case 
of the self-guided synchronous machine, the d-component of the stator 
current is i.sub.S1d disappears. The transverse force equation thus reads 
in the coordinate system (F): 
EQU F.sub.x =K.sub.Fx .multidot.i.sub.S2d.sup.(F,p2) .multidot..psi..sub.1 
--K.sub.Sx L.sub.2 .multidot.i.sub.S2q.sup.F,p2) 
.multidot.i.sub.S1q.sup.(Fp1) 
EQU F.sub.y =K.sub.Fy .multidot.i.sub.S2q.sup.(F,p2) .multidot..psi..sub.1 
--K.sub.Sy L.sub.2 .multidot.i.sub.S2d.sup.(F,p2) 
.multidot.i.sub.S1q.sup.(Fp1) 
or 
##EQU4## 
The useful force constants K.sub.Fx, K.sub.F y and the disturbing force 
constants K.sub.Sx, K.sub.Sy are differently defined depending on the 
winding combination (p.sub.2 =p.sub.1 +1 or p.sub.2 =p.sub.1 -1) and the 
machine type (synchronous machine or asynchronous machine). With the 
Maxwell force constant 
##EQU5## 
the Lorentz disturbing force constant 
##EQU6## 
and the Lorentz useful force constant K.sub.L becoming 
##EQU7## 
for the synchronous machine and K.sub.L =0 for the asynchronous machine, 
there applies for the case p.sub.2 =p.sub.1 +1: 
EQU K.sub.Fx =K.sub.Fy =K.sub.m +K.sub.L and K.sub.Sx =K.sub.Sy =K.sub.S 
and for the case p.sub.2 =p.sub.1 -1: 
EQU K.sub.Fx =K.sub.M -K.sub.L, K.sub.Fx =-K.sub.M +K.sub.l and K.sub.Sx 
=-K.sub.S, K.sub.Sy =K.sub.S. 
As the above vector equations show, the representation of the transverse 
forces which act in the machine as a whole in coordinate system (F) is 
very simple. 
The core of the controlled method of the invention is thus that the 
determination of the control current vector in just this coordinate system 
(F) takes place in the p.sub.2 -plane and is subsequently transformed into 
the stator coordinate system by a coordinate transformation. 
A mutual rotation of the two winding systems relative to one another 
through the angle .alpha..sub.1,2 and relative to the geometrical x-axis 
by the angle .alpha..sub.0 can be taken into account by an additional 
rotation of the control current vector through the angle 
##EQU8## 
The determination of the control current vector in the p.sub.2 plane then 
takes place in a coordinate system (T) which rotates with the angle 
.rho..sup.(p2) =.rho..sub.0.sup.(p2) +.gamma..sub.S.sup.(p1). 
If the drive flux is kept constant in the above equation, then the useful 
component of the transverse force is directed proportional to the control 
current. Since the disturbing force is generally small, and if no torque 
is built up in the machine, the desired current control vector can be 
determined in this case by a simple multiplication of the desired force 
vector with a constant. A change of the flux magnitude can be taken into 
account by parameter adaption. 
The idea of determining the desired control current vector via a decoupling 
equation also corresponds to a further concept of the invention. 
Resolved in accordance with the control current the force component 
equations read: 
##EQU9## 
(The desired values are marked in the equations with an *. As a result of 
the desired force vector 
##EQU10## 
and by means of knowledge of the machine parameters i.sub.S1q.sup.(F,p1) 
and .psi..sub.1 considered in the p.sub.1 plane in flux coordinates of the 
drive flux .psi..sub.1.sup.(p1), the desired control current vector 
i.sub.S2.sup.*(F,p2) can be continuously computed in the flux coordinates 
of the p.sub.2 -plane. A mutual rotation of the two winding systems to one 
another by the angle .alpha..sub.1,2 and relative to the geometrical 
x-axis by the angle .alpha..sub.0 can, as said, be taken into account by 
an additional rotation of the control current vector through the angle 
##EQU11## 
The current relation of the desired control current vector in the p.sub.2 
plane then takes place in a coordinate system (T) rotating with the angle 
.rho..sup.(p2) =.rho..sub.0.sup.(p2) +.gamma..sub.0.sup.(p1) in accordance 
with the following decoupling equation: 
##EQU12## 
The desired control current vector computed in the coordinate system (T) 
can be transformed by rotation through .rho..sup.(p2) into the stator 
coordinate system of the p.sub.2 pole-paired winding: 
EQU i.sub.S2.sup.*(S,p2) =D(.rho.).multidot.i.sub.S2.sup.*(T,p2) 
The so-obtained desired control current vector i.sub.S2.sup.*(S,p2) used as 
the desired value vector of a current feeding apparatus which feeds the 
control winding with the control current i.sub.S2.sup.(S,p2). 
A preferred embodiment is characterized in that the speed of rotation and 
of the torque of the machine is controlled or regulated, as in a 
conventional induction machine, via the drive winding by means of a 
generally known desired control regulating process such as for example a 
characteristic control or a field orientated control. The machine 
parameters i.sub.S1q.sup.(F,p1) and .psi..sub.1 and also the argument of 
the drive flux vector .psi..sub.1.sup.(p1), .gamma..sub.0.sup.(p1) 
resulting from this control of the drive winding are continuously 
determined by direct measurement, by computation from simply measurable 
machine parameters such as for example the stator voltages, stator 
currents, speed of rotation of the rotor, angle of rotation of the rotor 
via the machine equations or by means of a state observer and also by 
computation of measurement parameters and desired drive values. With the 
aid of these, as a result of the desired values of the transverse force, 
the computation of the control current vector i.sub.S2.sup.*(T,p2) takes 
place via the above defined decoupling equations in a coordinate system 
(T) rotating with the angle .gamma..sub.S.sup.(p1) and turned through the 
constant angle .rho..sub.0.sup.(p2). This control current vector 
i.sub.S2.sup.*(T,p2) is continuously transformed by a rotary 
transformation through the angle .rho..sup.(p2) =.rho..sub.0.sup.(p2) 
+.gamma..sub.S.sup.(p1) in stator coordinates and the so resulting control 
current vector i.sub.S2.sup.*(S,p2) is used as the desired current value 
for a current feed apparatus which feeds the control winding with the 
control current i.sub.S2.sup.(S,p2). 
The core of the control apparatus of the invention is to be seen in the 
fact that in the control apparatus, first means are present which 
determine the magnitude and phase of the drive flux and also the 
torque-forming component of the drive winding current from measurement 
parameters and/or desired values of the drive, and in that second means 
determine a desired value of the control current vector 
i.sub.S2.sup.*(S,p2) on the basis of these parameters and a desired 
transverse force vector by means of the control method of the invention. 
Fourth means are provided in order to calculate from the desired value of 
the control current vector i.sub.S2.sup.*(S,p2) the desired values of the 
m.sub.2 phase currents of the control winding by 2 to m.sub.2 phase 
transformation. Fifth means are provided which, as a result of the desired 
phase current values, feed the m.sub.2 trains of the control winding with 
currents. Moreover, third means are provided which feed the drive winding 
in accordance with any desired control or regulating method and ensure 
that a minimum drive flux is present in all operating states in which a 
transverse force is to act on the rotor. 
The advantage of the method or control apparatus of the invention lies as a 
whole in the fact that the transverse force acting on the rotor of the 
induction machine can be set more accurately than in the prior art and in 
any drive-side operating state of the machine, in particular also when the 
rotor is stationary and in the weak-field region, since the drive-side 
operating state of the machine is detected and both the Lorentz transverse 
forces and also the Maxwell transverse forces acting in the machine are 
taken into account by the control method.

DETAILED DESCRIPTION OF THE PREFERRED EXEMPLARY EMBODIMENTS 
It has been known for a long time (for example from H. Sequenz "The 
Windings of Electrical Machines" Springer Verlag Wien, 1950) that 
transverse forces acting on the rotor can be generated in an induction 
machine by two combined windings with the pole pair numbers p and p.+-.1. 
An AC-machine, such as an induction machine, of this kind can be 
illustrated by the symbol in FIG. 7. The drive winding (4) with the pole 
pair number p.sub.1, the control winding (5) with the pole pair number 
p.sub.2 =p.sub.1 .+-.1, and the rotor (6) of the induction machine (3) are 
symbolized by concentric circles. The signal flux plan of such an 
induction machine with drive and control winding is illustrated for the 
case of the asynchronous machine in FIG. 9 and for the case of the 
synchronous machine in FIG. 10. The block which is of interest here 
responsible for the transverse force formation is the same for both 
machine types. 
A control method in accordance with a first reference (Hermann) is based on 
a machine model which takes account only of the Maxwell forces and 
considers the induction machine only in steady-state operation. The drive 
winding is connected to a rigid three-phase current supply. For the 
control of the transverse force vector, the phase currents (i.sub.S2) of 
the control winding are derived from the drive currents (i.sub.S1) by 
Hermann by means of amplitude modulation. Via a phase adjustment, the 
phase between the drive currents and the control currents is fixedly set 
for a fixed working point. With this fixed working point, the contribution 
of the machine flux .psi..sub.1 is constant and the flux angle 
.gamma..sup.S(p1) rigidly associated with the phase of the drive currents. 
The cross coupling taken into account in FIGS. 9 and 10 between the 
control current components (i.sub.S2d.sup.(T,p2), i.sub.S1q.sup.(F,p1) and 
the transverse force components (F.sub.x, F.sub.y) which arises as a 
result of the Lorentz forces, is proportional to the torque-forming drive 
current component i.sub.S1q.sup.(F,p1) and relatively weak. For a fixed 
working point, the transverse force acting on the rotor is controllable in 
accordance with a control process as in Hermann. A control of the 
transverse forces is however not possible with this process with a dynamic 
operation of the rotary field machine (load change, change in the speed of 
rotation). 
The control method in accordance with the second reference (Bichsel) is 
based on a machine model which only takes account of the Lorentz forces. A 
precise control of the transverse force is not possible with this method, 
since in general the Maxwell transverse forces which are not taken into 
account are much larger than the Lorentz transverse forces. 
In accordance with the invention a control method is now proposed which is 
based on the model of the transverse force formation (18) shown in FIGS. 9 
and 10, which takes account of both the Maxwell transverse forces and also 
the Lorentz transverse forces, as well as any desired operating states of 
the machine (not in the steady-state operating case). The core of this 
control method is illustrated in FIG. 8. In a first step, the control 
current necessary for a desired force action and which is illustrated in 
the figure by the vector components i.sub.S2d.sup.*(T,p2) and 
i.sub.S2q.sup.*(T,p2) is determined in a coordinate system (T) which 
rotates with the flux vector and which has additionally been rotated by a 
fixed angle. In the second step the so-calculated desired control current 
vector is transformed by rotation through the angle .rho..sup.(p2) into 
the stator coordinate system (17). The transformation angle .rho..sup.(p2) 
=.rho..sub.0.sup.(p2) +.gamma..sub.S.sup.(p1) is continuously formed from 
the argument of the flux vector .gamma..sub.S.sup.(p1) measured in the 
p.sub.1 -plane in the stator coordinate system and a fixed angle of 
rotation .rho..sub.0.sup.(p2) which takes account of the mutual rotation 
of the two winding systems relative to one another and relative to the 
geometrical x-axis. The constant component of the angle of rotation 
.rho..sub.0.sup.(p2) is defined by the relationship 
##EQU13## 
with .alpha..sub.0 corresponding to any mutual rotation, that may be 
present, of the d-axis of the drive winding relative to the x-axis of the 
geometrical coordinate system, and with .alpha..sub.1,2 corresponding to 
any mutual rotation of the d-axes of the drive and control windings 
relative to one another. 
The determination of the control current in the coordinate system (T) as a 
result of the desired transverse force can be conceived in many different 
manners. In the simplest case, when the Lorentz disturbing forces are 
small and when the flux magnitude is kept constant, the control current is 
directly proportional to the desired transverse force and can thus be 
obtained from this by multiplication with a constant value. This simplest 
case is also shown in FIG. 8. For a winding with p.sub.2 =p.sub.1 +1 the 
two constants F.sub.x and F.sub.y have a positive sign and the same value. 
For p.sub.2 =p.sub.1 -1, F.sub.x has a positive sign and F.sub.y a 
negative sign. A change of the flux can be taken into account by adaption 
of the constants. 
The precise calculation of the control current in a coordinate system (T) 
by means of knowledge of the parameters .psi..sub.1 and 
i.sub.S1q.sup.(F,p1) responsible for the coupling between the torque 
formation and the induction machine (lower block in FIGS. 9 and 10) and 
the transverse force formation (18) corresponds to a further concept of 
the invention. A possibility for determination of the control current in 
vectorial form is shown in FIG. 12. The calculation of the desired control 
current vector i.sub.S2.sup.*(S,p2) (represented by the vector components 
i.sub.S2d.sup.*(S,p2).sub., i.sub.S2q.sup.*(S,p2)) takes place here 
component-wise by means of a decoupling equation (16a): 
##EQU14## 
based on the desired force vector 
##EQU15## 
with the aid of the torque-forming drive current component 
i.sub.S1q.sup.(F,p1) considered in flux coordinates in the p.sub.1 -plane, 
and further based on the drive flux magnitude .psi..sub.1, and from the 
machine parameters L.sub.2, K.sub.Fx, K.sub.Fy, K.sub.Sx, and K.sub.Sy. 
These are defined for the case p.sub.2 =p.sub.1 +1 by the relationships 
K.sub.Fx =K.sub.Fy =K.sub.M +K.sub.L and K.sub.Sx =K.sub.Sy =K.sub.S and 
for the case p.sub.2 =p.sub.1 -1 by the relationships K.sub.Fx =K.sub.M 
-K.sub.L, K.sub.Fx =-K.sub.M +K.sub.L and K.sub.Sx =-K.sub.S, K.sub.Sy 
=K.sub.S. 
The influence of the disturbing Lorentz force (the component in (18) 
proportional to i.sub.S1q.sup.(F,p1) is generally small compared with the 
maximum Maxwell transverse force. It can therefore be ignored in many 
applications (for example in the case of a transverse force regulation 
superimposed on the transverse force control). The first step in the 
calculation (16a) can then be substantially simplified since the cross 
coupling brought about by the disturbing Lorentz force need no longer be 
compensated. The signal flux plan of such a method simplified in this 
manner is shown in FIG. 13 (10b). Whereas the coordinate transformation 
(17) remains the same, the decoupling (16b) is reduced to a component-wise 
division by the flux magnitude. It reads: 
##EQU16## 
The desired value of the control current vector calculated in accordance 
with the above methods is supplied to a current feed apparatus (for 
example converter) which feeds the m.sub.2 -phase control winding of the 
induction machine with the m.sub.2 -phase control current i.sub.S2 (FIGS. 
9 and 10) (the number of lines can be selected as desired). The drive 
winding can be fed with three-phase currents of any desired frequency 
(also the frequency 0). That is to say, the drive winding can be operated 
both with a rigid three-phase network and also from a three-phase current 
source with variable frequency and amplitude. Of particular interest is 
naturally the operation at a frequency converter. The control method 
selected for the drive of the machine can be of any desired type 
(characteristic control, field orientated control or regulation, etc.) The 
sole condition for the method is that it must ensure that a minimum 
machine flux is present in those operating cases in which transverse 
forces are to be generated. 
The realization of the control method with technical apparatus can be 
conceived with a control apparatus which is schematically illustrated in 
FIG. 11. The control apparatus (9) comprises a signal processing module 
(15), an m.sub.2 -phase current feed module (11) for feeding the control 
winding, and an m.sub.1 -phase regulating and feed module (12) for feeding 
the drive winding. The current feed module (11) has the task of so feeding 
the control winding with m.sub.2 -phase currents that the actual value of 
the stator current vector corresponds as closely as possible to the 
desired value preset by the signal processing module. This object can be 
satisfied for example with an m.sub.2 -phase current impressing frequency 
converter (intermediate circuit voltage frequency converter with a current 
regulator or intermediate circuit current frequency converter) over an 
m.sub.2 -channel linear current amplifier. An m.sub.1 -phase frequency 
converter or an m.sub.1 -phase linear amplifier which is combined with a 
drive regulator operating in accordance with any desired method can 
likewise be used as the regulator and feed module for the feed of the 
drive winding (12). The signal processing module (15) is most simply 
realized with a digital computer, for example with a signal processor 
system. It consists of two-part modules: In block (10) the signal run plan 
(10a) in FIG. 12 or (10b) in FIG. 13 is realised. In block (13) the 
parameters .psi..sub.1, .gamma..sub.S.sup.(p1) and i.sub.S1q.sup.(F,p1) 
are determined with the aid of machine equations from measured and/or 
desired values (designated with *). The blocks (10) and (13) can be 
implemented as part programs on the same microcomputer, they can run as 
programs on different processors, or they can be realized wholly or partly 
by specialized digital or analog signal processing hardware. 
Although any desired control method is possible for the control of the 
drive winding, it is sensible to control or to regulate the drive in a 
field orientated manner. Since the size and phase of the flux vector must 
in any case be known for the method of the invention for the control of 
the transverse force, the additional effort for a field orientated drive 
regulation is only small. The FIGS. 14 to 21 show different examples for 
an asynchronous machine and also for a synchronous machine. 
FIG. 14 shows the example of a combination of a field orientated torque 
regulation of an asynchronous machine (13a) with the transverse force 
control of the invention with complete decoupling which takes account of 
the Lorentz disturbing force (16a). The magnetization components of the 
drive current i.sub.S1d and its torque-forming component i.sub.S1q are 
regulated here in the p.sub.1 -plane in a coordinate system (F) which 
rotates with .gamma..sub.S.sup.(p1) and is orientated to the flux pointer. 
Thus, a decoupling of the torque formation and the flux formation is 
ensured, whereby a very dynamic torque-setting is achieved by i.sub.S1q. 
The drive current is subsequently transformed into the stator coordinate 
system via a coordinate rotation through .gamma..sub.S.sup.(p1). The 
parameters .psi..sub.1, .gamma..sub.S.sup.(p1) and i.sub.S1q.sup.(F,p1) 
are jointly used here for field orientated torque regulation and also for 
the transverse force control method. The advantage of this combination for 
the transverse force control lies in the precise regulation of the flux 
magnitude to a predetermined value. The field orientated drive regulation 
can naturally also be combined with the simplified transverse force 
control of the invention with only partial decoupling which does not take 
account of the disturbing Lorentz force (16b). This example is shown in 
FIG. 15 In distinction to FIG. 14, i.sub.S1q.sup.(F,p1) is not required 
here for the transverse force control. In other respects, the same applies 
here as also said in FIG. 14. 
A simplification relative to the control method in FIGS. 14 and 15 results 
from the fact that the drive flux is not regulated, but rather only 
controlled in field orientated manner. FIG. 16 shows the example of the 
combination of a possible field orientated torque control of the 
asynchronous machine (13b) with the transverse force control in accordance 
with the invention with complete decoupling which takes account of the 
disturbing Lorentz force (16a). In contrast, for a field orientated 
regulation the magnetization components of the drive current i.sub.S1d and 
of its torque-forming component i.sub.S1q in the drive flux orientated, 
rotating coordinate system (F) are here not regulated, but rather 
controlled. The most important simplification results from the fact that 
the flux vector does not have to be determined from the point of view of 
size and direction. Only a model value of the flux angle 
.gamma..sub.S.sup.*(p1) is used for the transformation of the control 
current from the rotating coordinate system (F) into the stator coordinate 
system. The model value .gamma..sub.S.sup.*(p1) can be determined on the 
basis of desired values (for example Mi.sub.soll, .psi..sub.1soll) and 
from eventually simply detectable measurement parameters (for example 
.omega..sub.m, .gamma..sub.m) from the machine model. 
.gamma..sub.S.sup.*(p1) is also used for the coordinate transformation in 
the transverse force control method. The control parameters 
.psi..sub.1.sup.*, i.sub.S1q.sup.*(F,p1) are used in place of the 
parameters .psi..sub.1, i.sub.S1q.sup.(F,p1). The field orientated drive 
control can naturally also be combined with the simplified transverse 
force control of the invention with only partial decoupling which does not 
take account of the disturbing Lorentz force (16b). This example is shown 
in FIG. 17. In distinction to FIG. 16, i.sub.S1q.sup.*(F,p1) is not 
required here for the transverse force control. In other respects the same 
applies as also said in connection with FIG. 16. 
In distinction to asynchronous motors, synchronous motors are normally 
controlled in field orientated manner. Since the flux in the synchronous 
machine is fixedly coupled to the rotor, the flux angle 
.gamma..sub.S.sup.(p1) can be quite simply determined from the mechanical 
rotor angle .gamma..sub.m, by multiplication with p.sub.1. FIG. 18 shows 
the example of the combination of a field orientated torque regulation of 
a synchronous machine (13c) with the transverse force control of the 
invention with complete decoupling which takes account of the disturbing 
Lorentz force (16a). In the synchronous machine the drive flux is 
generated via a DC current in the rotor winding or with permanent magnets 
on the rotor. .psi..sub.1 is thus supplied as a machine parameter to the 
transverse force control. The drive current has in the synchronous machine 
only a torque-forming component and corresponds thus directly to 
i.sub.S1q. This can be measured and transformed into the flux coordinate 
system (F). The transformation in accordance with (F) is the same value as 
the formation of the magnitude The drive current i.sub.S1q.sup.(F,p1) is 
then used both for the torque regulation and also for the transverse force 
control. The drive flux angle is here, as said, determined via the 
mechanical rotor angle. The field orientated drive regulation of the 
synchronous machine can naturally also be combined with the simplified 
transverse force control of the invention with only partial decoupling 
which does not take account of the disturbing Lorentz force (16b). This 
example is shown in FIG. 19. In distinction to FIG. 18 
i.sub.S1q.sup.(F,p1) is required here for the transverse force control. In 
other respects, the same applies as was said in connection with FIG. 18. 
The field orientated torque control of the synchronous machine is more 
frequent than the field orientated torque regulation since in practice a 
speed of rotation regulation circuit is mainly superimposed from the 
torque regulation circuit. FIG. 20 shows the example of a combination of a 
field orientated torque regulation of a synchronous machine (13c) with the 
transverse force control of the invention with complete decoupling which 
takes account of the disturbing Lorentz force (16a). The drive current is 
now controlled directly proportional to the torque and reversely 
proportional to the drive flux. This control value is likewise used by 
transverse force control methods. As a measurement parameter only the 
mechanical rotor angle .gamma..sub.m is required. From this, 
.gamma..sub.S.sup.(p1) is derived and is fed both to the torque control 
and also to the transverse force control. The field orientated drive 
control of the synchronous machine can naturally also be combined with the 
simplified transverse force control of the invention with only partial 
decoupling which does not take account of the disturbing Lorentz force 
(16b). This example is shown in FIG. 21. In distinction to FIG. 20, the 
drive current is not required here for the transverse force control. In 
other respects, the same applies as was said in connection with FIG. 20. 
If a very accurate adjustment of the transverse force acting on the rotor 
is required, then it can be sensible to not control this but rather to 
regulate it. For this purpose, the transverse force is measured in one or 
in two directions by means of force sensors (for example with strain 
gauges mounted on a bending beam or a load cell with piezoelectric 
sensors). If the transverse force is only to be regulated in one 
direction, then this is most simply measured in the same direction in 
which it is regulated. The measured value is subtracted from the desired 
value and the so-formed control deviation is fed to a single parameter 
regulator. The regulator output is split up into an x-component and a 
y-component (if the direction of the desired force corresponds with the x- 
or y-axis then a splitting up into components can be avoided) and is fed 
to the transverse force control in accordance with claim 1 and claim 2 
(F.sub.x.sup.* and F.sub.y.sup.*). If the force is measured in two 
directions (preferably perpendicular to one another), then the planar 
actual force vector can be determined. The two vector components F.sub.x 
and F.sub.y are substracted from the desired values and the controlled 
deviations are fed to two independent regulators. The regulator outputs 
are connected to the inputs (F.sub.x.sup.* and F.sub.y.sup.*) of the 
transverse force control. FIG. 22 shows a schematic block diagram of the 
transverse force regulation. 
If the rotor is displaceable in one or more directions (the transverse 
section plane), then its position can also be influenced with the aid of 
transverse forces. If the rotor position is determined by means of 
sensors, or via an observer, then this can be regulated. FIG. 23 shows the 
schematic block diagram of a possible transverse thrust regulation for two 
axes. The rotor position (x, y) is determined by position sensors or via 
an observer. In the illustration of FIG. 23 the origin of the coordinates 
lies at the center of the machine. The actual position is subtracted from 
the desired position (x.sub.soll, y.sub.soll) and the control difference 
is supplied to a regulator. The regulation takes place most simply 
component-wise as illustrated in FIG. 23. As a regulator one can consider 
a proportional plus derivative action controller, a proportional, integral 
plus derivative action controller, or a status regulator with a status 
observer. The regulator output is connected to the input (F.sub.x.sup.* 
and F.sub.y.sup.*) of the transverse force control (10). The current 
control apparatus (11) then controls in known manner the induction machine 
with a special winding (3) in accordance with FIG. 9 or 10. The 
association which is not shown in (3) between the transverse force and the 
rotor position (double integrator) and the magnetic pull (positive return) 
acting as a result of the displacement of the rotor from the center have 
been externally supplemented in FIG. 23. With the described transverse 
thrust regulation, two degrees of freedom of the rotor can be regulated. 
As an application, the realization of a radial magnetic bearing in an 
induction machine is conceivable. Two such induction machines with 
transverse thrust regulation can be combined into a bearingless machine, 
that is to say to one machine in which a torque is generated via the drive 
windings and magnetic radial bearing forces are generated via the two 
control windings. The axial position of the rotor can be stabilized by an 
additional axial magnetic bearing or by a conical shape of the rotor. The 
principal build-up of such a "bearingless" rotary field machine is shown 
in FIG. 24. If the two part machines are equipped as shown in FIG. 25 with 
conical rotors, then the axial position can likewise be determined via the 
drive flux distribution between the two part machines. As a result of the 
same bearing force action, a bearingless motor of this kind also 
principally has the same characteristics as the conventional active 
magnetically journalled drive. These result from the freedom of contact of 
the support and the possibility of setting adjustments via the regulation. 
Thus the magnetic support is free of wear, servicing and lubricants. The 
maximum permissible speed of rotation is restricted only by the 
centrifugal loading of the rotor. The bearing characteristic, that is to 
say the stiffness and the damping, can be set during operation via the 
regulation and can be adapted to changing conditions. A compensation of 
imbalance forces is conceivable in just the same way as the active damping 
of bending oscillations of the rotor. With an integral component of the 
regulator, an infinitely large stiffness can be achieved in the stationary 
operating state. Within the limits of the air gap, the position and also 
the angle of inclination of the rotor can be set and changed during 
operation. 
The bearingless machine, however, opens up further advantages. As the 
magnetic transverse forces act distributed over the whole rotor and not 
only at the two ends, as with conventional journalling, an efficient means 
is available for influencing the dynamics of the rotor. Moreover, the 
achievable bearing forces are very large since the total surface of the 
machine rotor is available for the force formation. Quite new perspectives 
are opened up in combination with conventionally journalled machines (ball 
bearings, air bearings, magnetic bearings, hydrostatic and hydrodynamic 
bearings) with a bearingless motor. A machine of this kind is 
schematically illustrated in FIG. 26. Through the possibility of being 
able to dynamically set the transverse forces acting on the rotor with any 
desired direction of amplitude, new principles of solution result for the 
damping of rotor oscillations, for influencing the bearing 
characteristics, for leaving the conventional rotor, or for influencing 
the through-bending of the rotor. The latter application is schematically 
illustrated in FIG. 27. 
Reference numeral list 
1 drive winding parameter (indices) 
2 control winding parameter (indices) 
3 induction machine with a p.sub.1 -pole-paired drive winding and a 
(p.sub.2 =p.sub.1 .+-.1)-pole-paired control winding 
3a a asynchronous machine with transverse force formation and torque 
formation 
3b synchronous machine with transverse force and torque formation 
4 control winding 
5 drive winding 
6 rotor 
7 flux measurement probes 
9 control apparatus 
10 control current calculation 
10a a control current calculation with complete decoupling 
10b control current calculation with partial decoupling 
11 current feed apparatus for control winding 
12 second means 
13 flux calculation and transformation 
14 drive parameters 
15 first means 
16a a complete decoupling 
16b partial decoupling 
17 coordinate transformation (T-&gt;S) 
d direct component (dq representation) 
F transverse force vector 
F.sub.x x component of the transverse force vector 
F.sub.y y component of the transverse force vector 
(F) drive flux orientated coordinate system example: i.sub.S1q.sup.(F,p1) 
designates the transverse components of the drive current vector in drive 
flux coordinates illustrated in the p.sub.1 plane 
K.sub.L Lorentz useful force constant: for synchronous machine 
##EQU17## 
for an asynchronous machine: K.sub.L =0 
K.sub.M Maxwell force constant: 
##EQU18## 
K.sub.S Lorentz disturbing force constant 
##EQU19## 
K.sub.Fx force constant in the x direction 
K.sub.Fy force constant in the y direction 
K.sub.Sx disturbing force constant in the x direction 
K.sub.Sy disturbing force constant in the y direction 
i.sub.S1.sup.(p1) represents the drive current vector in the p.sub.1 plane 
i.sub.S1d.sup.(p1) represents the direct component of the drive current 
vector in the p.sub.1 plane 
i.sub.S1q.sup.(p1) represents the transverse component of the drive current 
vector in the p.sub.1 plane 
i.sub.S2.sup.(p2) represents the control current vector in the p.sub.2 
plane 
i.sub.S2d.sup.(p2) represents the direct component of the control current 
vector in the p.sub.2 plane 
i.sub.S2q.sup.(p2) represents the transverse component of the control 
current vector in the p.sub.2 plane 
l length of the rotor 
L.sub.1 main inductance of the drive winding 
L.sub.2 main inductance of the control winding 
m phase number, string number 
m.sub.g mass of the rotor 
M torque 
M.sub.i internal machine torque 
M.sub.L load torque 
p pole pair number 
p.sub.1 pole pair number of the drive winding 
p.sub.2 pole pair number of the control winding 
(p.sub.1) plane of illustration with the pole pair number p.sub.1 
(p.sub.2) plane of illustration with the pole pole pair number p.sub.2 
q transverse component (dq representation) 
R rotor 
r radius of rotor 
S stator 
(S) stator orientated coordinate system for example: i.sub.S2.sup.(S,p2) 
designates the control current vector in stator coordinates illustrated in 
the p.sub.1 plane 
(T) coordinate system rotating with the angle .rho. for example: 
i.sub.S2.sup.(T,p2) designates the control current vector in a coordinate 
system rotating with the angle .rho..sup.(p2) illustrated in the p.sub.1 
plane 
w.sub.1 winding number of the drive winding 
w.sub.2 winding number of the control winding 
X,Y axes of the geometrical coordinate system (indices) 
x,y deflection of the rotor in the x,y direction 
* desired values, control values example: i.sub.S2.sup.*(S,p2) designates 
the desired value of the control current vector in stator coordinates 
illustrated in the p.sub.1 plane 
.alpha..sub.0 mutual rotation of the d axis of the drive winding relative 
to the x-axis of the geometrical coordinate system 
.alpha..sub.1,2 mutual rotation of the d axes of the drive and control 
windings 
.gamma..sub.m mechanical rotor angle 
.gamma..sub.S.sup.(p1) argument of the drive flux vector illustrated in the 
p.sub.1 plane 
.mu..sub.o magnetic field constant in vacuum 
.pi. circuit constant 
.psi..sub.1 drive flux value 
.psi..sub.1.sup.(p1) drive flux vector illustrated in the p.sub.1 plane 
.rho..sup.(p2) mutual rotation of the coordinate system (T) used to 
calculate the desired control current vector relative to the stator 
coordinate system measured in the p.sub.2 plane 
.rho..sub.0.sup.(p2) time invariable component of .rho..sup.(p2) 
.omega..sub.m mechanical frequency of rotation 
.omega..sub.R rotor frequency of rotation (slip frequency).