Abstract:
A method for operation of a magnetic levitation railway which contains vehicles with a plurality of supporting magnets ( 20   a . . .    20   j ) and supporting runners ( 26 ) associated with them. In the event of a malfunction, the braking of the vehicle with the drive and braking systems switched off is brought about or assisted until a preselected destination stopping point is reached solely in that, even before the destination stopping point is reached, at least one of the supporting magnets (for example  20   f,    20   g ) is switched off, and the magnetic levitation vehicle is placed on the track path ( 3 ) by means of the associated supporting runner ( 26 ), and is brought to rest at the destination stopping point by making use of the friction forces that occur as a result. A magnetic levitation vehicle is provided and operated in this way.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a United States National Phase application of International Application PCT/DE2007/002123 and claims the benefit of priority under 35 U.S.C. §119 of German Patent Application DE 10 2007 003 118.3 filed Jan. 15, 2007, the entire contents of which are incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The invention relates to a method for operation of a magnetic levitation railway, comprised of a track path and a magnetic levitation vehicle with a plurality of supporting magnets and supporting runners allocated to these, with the magnetic levitation vehicle being maintained by means of supporting magnets in a levitated status during its travel along a track path and to a magnetic levitation railway. 
     BACKGROUND OF THE INVENTION 
     There are numerous proposals known and already implemented into practice for the operation of magnetic levitation railways of this kind. All these methods throughout are based on the principle of propelling and braking the magnetic levitation vehicles in normal operation with a driving and braking system, which for example comprises a long stator linear motor as well as control and regulating devices destined for its operation (DE 38 07 919 C2, DE 10 2004 018 311 A1). A long stator linear motor of this kind comprises a long stator installed in a track path and comprised of grooves and alternating current windings laid in them by means of which advancing migration waves are generated along the track path. The exciter field of the long stator linear motor is generated by supporting magnets arranged in the vehicles which moreover also fulfil the function of carrying which is required to obtain levitation. The frequency of the migration waves determines the velocity of vehicles. 
     To enable the vehicles to come to a controlled standstill in case of a failure of the driving and braking system regardless of where they are currently located and regardless of the velocity at which they are currently running, these vehicles are provided with an additional brake in form of a clasp brake (DE 30 04 705 A1), an eddy-current brake (DE 10 2004 013 994 A1) or the like. Additional brakes of this kind are also used in the event of other disturbances, for example in case of loss of localization. In all these cases, the additional brake ensures that the vehicles can safely be brought to a standstill at any of the destination stopping points existing along a track path, which may also be usual railway stations. 
     In practical applications of magnetic levitation railways, eddy-current brakes are preferably used as additional brakes. These are allocated to guide rails installed at the track path and they generate eddy-currents braking in them. However, eddy-current brakes have a disadvantage in that the comparably high current rates needed for their operation can be generated in the magnetic levitation vehicles themselves only at velocities above approximately 100 km/h, e.g. by the aid of so-called linear generators. At lower speeds, on the contrary, these currents must be supplied by batteries accommodated in the vehicles. Consequently and despite the fact that eddy-current brakes usually are activated only in case of disturbance, a plurality of batteries is needed which is undesirable due to additional weight and major space requirements involved thereby. In other words, magnetic levitation vehicles must always be operated in such a manner and destination stopping points arranged along the track path must always be chosen in such a manner that the batteries provided in the vehicles are always and safely available for an emergency braking. Conversely, the electrical energy needed in cases of emergency for the function of “carrying” is comparably insignificant. 
     SUMMARY OF THE INVENTION 
     Now, therefore, the underlying technical problem to be solved by the present invention is to configure the magnetic levitation railway of the afore-mentioned species and the relevant method for its operation in such a manner that batteries of the kind described hereinabove can largely be dispensed with while safe braking is nevertheless ensured. 
     According to the invention a method is provided for operation of a magnetic levitation railway, comprised of a track path and a magnetic levitation vehicle with a plurality of supporting magnets and supporting runners allocated to these. The magnetic levitation vehicle is maintained by means of supporting magnets in a levitated status during its travel along a track path. The vehicle is settled on the track path by means of supporting runners at destination stopping points by switching-off the supporting magnets and being gradually slowed down before it reaches a destination stopping point. The braking is solely induced or supported by switching-off at least one of the supporting magnets already before the destination stopping point is reached and by settling the magnetic levitation vehicle by means of the supporting runner allocated to this supporting magnet onto the track path, such that the vehicle is brought to a standstill at the destination stopping point by exploiting the frictional forces thus generated. 
     According to a further aspect of the invention, a magnetic levitation railway is provided comprised of a track path, at least one magnetic levitation vehicle movable along a track path and having a plurality of supporting magnets as well as supporting runners allocated to these. The magnetic levitation vehicle is maintained in a levitated status during the travel by means of supporting magnets and is settled with the supporting runners on the track path at destination stopping points by switching-off the supporting magnets. The magnetic levitation railway also includes a propellant and braking system for the magnetic levitation vehicle and an additional brake for gradual braking of the magnetic levitation vehicle in the event of a disturbance occurring before a destination stopping point is reached. The additional brake just contains the supporting runners as active braking elements and is provided with means to switch-off selected supporting magnets in order to settle down the vehicle onto the track path in the event of a disturbance already before the destination stopping point is reached by means of the supporting runners allocated to the switched-off supporting magnets. 
     The present invention bears the advantage in that frictional forces which result on depositing the vehicles between the supporting runners and the track path are utilized for the braking process. For this purpose, depending on the momentary situation, only one, a plurality of or all the existing supporting runners can be utilized for the braking process. Wear or tear of supporting runners or of the gliding rails of the track path interacting with them are largely harmless, because this type of braking is only applied in case of disturbance and therefore almost never or at least extremely rarely, as has been outlined hereinabove. Furthermore it is of advantage that the supporting runners are in any way already provided on the vehicles and so the otherwise usually applied sophisticated additional brakes in form of eddy-current brakes or the like may be entirely dispensed with. Besides, batteries—if at all required—with a low accumulator capacity are needed to be able to sustain the carrying function of supporting magnets for as long as this is required. 
     The braking effect caused by depositing magnetic levitation vehicles onto their supporting runners is in principle known (DE 10 2004 018 311 A1). In the case known, the braking effect, however, is the consequence of a simultaneous shutoff of all exciter fields and/or supporting magnets which is caused for other reasons and initiated by the vehicles, with the aim to instantly prevent any disturbance of the driving and braking system in the area of destination stopping points, for example an erroneous acceleration or an acceleration effected in the wrong direction instead of a braking. Conversely, according to the present invention, the frictional forces between supporting runners and track path are utilized in a controlled and well-aimed manner to render additional brakes unnecessary, with it being possible to control the braking force without any difficulty even from a central log computer arranged outside the magnetic levitation vehicles. 
     The present invention is elucidated in greater detail as set forth below by way of the attached drawings, taking an embodiment as an example. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  is a schematic partial cross-section through a conventional vehicle of a magnetic levitation railway; 
         FIG. 2  is details of part of the vehicle as per  FIG. 1  in a simplified schematic side view; 
         FIG. 3  is an enhanced detail X of the vehicle as per  FIG. 2  with further components; 
         FIG. 4  is a schematic block circuit diagram to control the inventive braking function with a vehicle according to  FIG. 2  and  FIG. 3 ; 
         FIG. 5  is a graph of potential braking curves for a vehicle according to  FIG. 2  and  FIG. 3 ; 
         FIG. 6  is a graph of potential braking curves for a vehicle according to  FIG. 2  and  FIG. 3 ; 
         FIG. 7  is a graph of induced braking curves for a vehicle as per  FIG. 2  and  FIG. 3 ; and 
         FIG. 8  is a schematic flow diagram for executing an inventive braking process. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings in particular,  FIG. 1  schematically shows a cross-section trough a magnetic levitation vehicle  1  which is mounted in a usual manner to be operable on a track path that comprises beams  2  made of steel and/or concrete as well as gliding rails  3  mounted on them. Vehicle  1  is driven by means of a long stator linear motor which comprises stator packets arranged in successive order in longitudinal direction and fixed underneath the gliding rails  3 . Stator packets  4  have teeth and grooves succeeding in alternation and not shown here which are fed with a three-phase current of a variable amplitude and frequency. The actual exciter field of the long stator linear motor is generated by at least one supporting magnet arrangement  5  which is fastened by at least one lateral rack stirrup  1  to vehicle  1  and which comprises magnet poles facing the stator packets  4 . The supporting magnet arrangement  5  not only provides the exciter field but also fulfils the function of carrying and levitating by maintaining a defined gap  7  of 10 mm, for example, between itself and the stator packets  4  during operation of vehicle  1 . 
     For track gauging of vehicle  1 , the beams  2  are comprised of laterally arranged reaction and/or lateral guiding rails  8  faced by guiding magnet arrangements  9  mounted on rack stirrups  6  which serve to maintain a gap  7   a  corresponding to gap  7  between itself and the reaction rail  8  during operation. The supporting magnet arrangement  5  shown in  FIG. 1  and the guiding magnet arrangement  9  each form a magnet system fastened to rack stirrups  6  for the functions of “carrying” and “guiding”, respectively. But it is obvious that a plurality of such magnet systems can be mounted at vehicle  1  side by side or one behind the other in the direction of travel, said magnet systems being connected by means of rack stirrup  6  to a non-bending bogie and/or levitation rack  10  comprised of longitudinal and transversal trusses and supporting a car box  11  of the vehicle  1  ( FIG. 1 ) which is provided with a passenger cell. 
     According to  FIG. 2 , there are several pneumatic springs  12  mounted at the underside of car box  11  and spaced in the direction of a vehicle longitudinal axis  14  and a traveling direction running in parallel thereto (arrow v). The pneumatic springs  12  take effect on front and rear ends of levitation bogy sections  15  which on the whole form the levitation bogie  10  ( FIG. 1 ). In the practical example, each levitation bogie section  15  comprises two supporting elements  16   a ,  16   b  arranged one behind the other the direction of longitudinal axis  14  in form of framed parts or the like and longitudinal girders  17  connecting these firmly to each other, with the supporting element  16   a  each being located at the front viewed in the direction of travel. 
     According to  FIG. 2 , the vehicle  1  furthermore comprises a multitude of supporting magnet arrangements  5   a  . . .  5   h  arranged one behind the other viewed in the direction of travel. Each supporting magnet arrangement  5   a  . . .  5   h  is subdivided by an imaginary center plane indicatively shown by a dotted line  19  into two electrically separate though mechanically coherent halves. Each half contains a certain number of six magnet poles, for example, the windings of which form a group, each of which can be supplied with electric current independently of all other groups. Each supporting magnet arrangement  5   a  . . .  5   h  therefore is comprised of a constructively coherent component comprising twelve magnet poles, for example, but electrically it is comprised of two parts separated from each other which for simplicity&#39;s sake are designated as supporting magnets  20   a ,  20   b , and/or  20   c ,  20   d , etc. and/or  20  I,  20   j  as set forth below in  FIG. 2 . 
     From  FIGS. 2 and 3 , it furthermore becomes evident that each supporting element  16   a ,  16   b  is connected with two each of the supporting magnets  20   a  . . .  20   j . For example, the front-end supporting element  16   a  of one of the levitation bogie sections  15  at its front side is connected with the rear supporting magnet  20   d  of a supporting magnet arrangement  5   b  running ahead of it and connected at its rear side with the front side supporting magnet  20   e  of a supporting magnet arrangement  5   c  running behind, while the rear side supporting element  16   b  of the same levitation bogie section  15  is accordingly connected with the rear side supporting magnet  20   f  of the supporting magnet arrangement  5   c  and the front side supporting magnet  20   g  of the supporting magnet arrangement  5   d  etc. running behind. 
     In accordance with  FIG. 3 , the connection of the supporting elements  16   a ,  16   b  and/or of the associated rack stirrups  6  not shown in  FIG. 3  with the supporting magnets  20   a  . . .  20   j  is effected through additional springs  24 . Besides, it is obvious that the levitation bogie sections  15  and the supporting magnet arrangements  5   a  . . .  5   h  are so articulated with each other that the required relative movements towards each other can be executed both during curve rides of vehicles  1  and during rides uphill and downhill. 
     Finally, in a schematic representation, too, though slightly different to the one shown in  FIG. 1 ,  FIG. 3  shows one of the gliding rails  3  and a supporting runner  26  allocated to it and fastened to the underside of the levitation bogie section  15 . By means of these supporting runners  26 , the vehicle  1  is settled onto the track path and/or its gliding rails  3 , if the supporting magnets ( 20   a  . . .  20   j ) are de-energized. According to  FIG. 3 , such a supporting runner  26  is preferably allocated to each supporting element  16   a ,  16   b  of the levitation bogie  10 , said supporting runner being settled on the associated gliding rail  3  when two allocated supporting magnets, e.g.  20   f ,  20   g  in  FIG. 3 , are de-energized. 
     Besides it is clear that the configurations described hereinabove, more particularly the supporting magnet arrangements  5   a  . . .  5  and the supporting runners  26  are preferably provided both on the right and on the left side of the vehicle in identical form. 
     The supply of electrical current to the supporting magnet arrangements  5   a  . . .  5   h  and/or supporting magnets  20   a  . . .  20   j  is performed by the aid of control circuits (e.g.  27   a  and  27   b  in  FIG. 3 ) which for example are accommodated in a car box  17  and which in their levitated status serve to sustain the air gap  7  ( FIG. 1 ) between the supporting magnet arrangements  5   a  . . .  5   h  and stator packets  4 . In this case, there is a corresponding gap  28  ( FIG. 3 ) between the supporting runners  26  and the gliding rails  3 . 
     The control circuits  27   a ,  27   b , . . .  27   n  connected to various supporting magnets  20   a  . . .  20   j  are schematically shown in  FIG. 4 , wherein n is equivalent to  2   k  in the practical example, if k is the number of existing supporting magnet arrangements  5   a  . . .  5 . In this case, as described hereinabove, it is assumed that the windings of each supporting magnet  20   a  . . .  20   j  can be supplied with electric current by the aid of a separate control circuit  27   a  . . .  27   n  (e.g. DE 10 2004 012 748 A1). Each control circuit  27   a  . . .  27   n  moreover comprises at least one gap sensor  29  according to  FIG. 4 , which measures the actual value of gap  7 , as well as a control element  30  connected to sensor  29  which compares the actual value with a defined design value and which generates a differential and/or actuator signal, and it comprises an electric current actuator  31  which is fed with this actuating signal and by means of which the electric current is controlled through the windings of the supporting magnet  20   a  . . .  20   j  connected to it in such a manner that the carrier gap  7  mainly remains constant as long as it is desired to keep vehicle  1  in the levitated status. Expediently, all control circuits  27   a  . . .  27   n  are of an identical set-up and structure. 
     Magnetic levitation railways of the kind described are generally known, for example, from documents DE 38 07 919 C2, DE 10 2004 012 748 A1, DE 10 2004 013 690 A1 and DE 10 2004 018 311 A1, which therefore, to avoid further explanations, herewith become the object of the present disclosure by taking reference to them. Corresponding United States patent publications U.S. Pat. No. 4,988,061; US2008252405, Canadian patent publication CN1842455 and United States patent publication US2008277534 are equivalent English language documents incorporated herein by reference. 
     While usual magnetic levitation railways comprise an additional brake configured as a clasp brake, eddy-current brake or the like apart from the propellant and braking system described as an example, an additional brake is provided in accordance with the present invention which merely comprises the supporting runners  26  ( FIG. 3 ) as active braking elements. In particular, the present invention assumes that the frictional forces between supporting runners  26  and gliding rails  3  are sufficiently high to be able to safely induce the necessary retardation of vehicle  1  in case of emergency. Moreover, the present invention takes benefit of the fact that the gaps  7 ,  28  existing between vehicle  1  and track path  2 ,  3  are so small that the supporting runners  26  can be settled independently of each other onto the track path and/or onto the relevant gliding rails  3  by reason of the fact that the relevant supporting magnets  20   a  . . .  20   j  are switched off. This is indicated in  FIG. 3  schematically and in exaggerated size by way of dashed lines, according to which the supporting runner  26  shown there can be settled on gliding rail  3  independently of all the other existing supporting runners  26  by reason of the fact that the electric currents flowing through the windings of the allocated supporting magnets  20   f  and  20   g  are switched-off by means of the control circuits  27   a  and  27   b , so that these supporting magnets  20   f  and  20  lose their function of carrying.  FIG. 3  shows that the two supporting magnets  20   f  and  20  as compared with the not shown stator packets  4  are lowered which is feasible due to their articulated connections with the associated levitation bogie sections  15 , even though the other supporting magnets  20   a  . . .  20   g  and/or supporting magnet halves are continually supplied with electric current. 
     The limits of braking enabled in this manner are shown and represented in  FIG. 5 . 
     Proceeding from a location  33  plotted alongside of an abscissa, a vehicle moving at a velocity plotted alongside of the ordinate and to be slowed down while the propellant and braking system has been shut-off for whatever reason can maximally reach a location  34 , if all supporting runners  26  at location  33  are simultaneously settled onto the gliding rails  3 . Conversely, if merely the propellant and braking system is switched-off while the vehicle is continually kept in levitated status, the vehicle would reach a location  35 . The position of both locations  34 ,  35  on the one hand depends in particular on the velocity which the vehicle had attained at location  33 . On the other hand, the crucial factors for the position of location  34  above all are the friction conditions between supporting runners  26  and gliding rails  3  as gliding partners, depending on current weather (e.g. dry, wet, etc.), while wind conditions (headwind, tailwind, etc) are of some significance for reaching a location  35 . In both cases, the distance profile (e.g. planar, rising or falling distance) is noticeable. Braking curves  36 ,  37  leading to locations  34  and  35  are shown in hatched lines in  FIG. 5 . Moreover, the length of each braking distance is shown by arrows  38 ,  39  underneath the abscissa. 
     If the positions of selected destination stopping points  40  ( FIG. 5  and  FIG. 6 ) are usually so chosen that the vehicle being in levitated status can still safely reach the stoppage area following next in the direction of travel when the propellant and braking system fails to work (e.g. DE 38 07 919 C2 corresponding to U.S. Pat. No. 4,988,061), then the next destination stopping point approachable in case of a disturbance and designated with reference number  40  in  FIG. 5  will in any case lie upstream of location  35  in the direction of travel v. Conversely, with regard to location  34  lying upstream to the destination stopping point  40 , it is assumed that in the event of a failure the vehicle still is that far away from the destination stopping point  40  that it can be timely slowed down at least by settling all supporting runners  26 . If this were not the case, the vehicle would have to remain in levitated status for as long as required to be able to reach the stopping area following next to location  35  along the travel distance. Since by considering various possible friction conditions, wind velocities, etc. proceeding from any location  33  along the travel distance a most favorable and a least favorable (worst case) braking curve  36  and/or  37  will result, the assumption constantly taken for the purpose of the present invention and for the following description expediently is that the braking curves  36 ,  37  in  FIG. 5  each represent the least favorable case. 
     The possibilities resulting hereof are indicated in  FIG. 6 . It is again assumed that the nearest stopping area following in the direction of travel is defined by the destination stopping point  40 . At this destination stopping point  40 , a braking curve  41  terminates which represents the case that all supporting runners have been settled. A safe hold at the destination stopping point  40  therefore is just possible by a simultaneous settling of all supporting runners  26 , if braking is initiated latest at a point  42 . Conversely, in case the vehicle is still far enough away from location  33 , the destination stopping point  40  could also be reached in levitated status along a braking curve  43 . 
     Finally  FIG. 6  shows that depending on where braking of the vehicle is initiated, a hatched area section is obtained which represents an operation area  44  applicable in the worst case. This operation area  44  is confined by braking curve  41  at the top and by braking curve  43  at the bottom, and it indicates that within the hatched area it is possible to perform different and possibly combinable braking maneuvers by depositing some, all, or no supporting runners  26  at all in order to ultimately safely reach the destination stopping point  40 . In this regard,  FIG. 7  represents an example according to which the destination stopping point  40  is reached because the number of supporting runners  26  which the vehicle glides on is varied, thus leading within operation area  44  according to  FIG. 6 , for example, to a braking curve  45  comprised of three sections  45   a ,  45   b , and  45   c . Section  45   a  results by the fact that initially just a few supporting runners  26  are settled in order to support the braking also initiated in levitated status after the shutoff of the propellant and braking system, which, however, would not be sufficient to reach destination stopping point  40 . Therefore, in section  45   b , further or all supporting runners  26  are settled. As this would cause a standstill of the vehicle before destination stopping point  40  is reached, some supporting runners  26  are finally lifted again in section  45   c  in order to avoid that the vehicle comes to a premature standstill. The braking distance after the beginning of the braking process (location  33  is identified by an arrow  46  in  FIG. 7 . 
     The braking curve  45  in  FIG. 7  thus shows that the friction forces required to reach the destination stopping points are generated by the number of supporting runners  26  on which the magnetic levitation vehicle is settled and by the points of time at which this occurs. Moreover, the required friction forces are of course permanently calculated and corrected, if required, depending on the current velocity of the vehicle and on its distance to destination stopping point  40 . 
     An example for the practical application of the inventive method becomes evident from  FIGS. 4 and 8 .  FIG. 4  shows a computer  47  which is comprised of ports  47   a  to  47   n  that are linked to control elements  30  of control circuits  27   a  . . .  27   n . Via ports  47   a  . . .  47   n , the control elements  30  linked to them are so controlled that selected supporting magnets  20   a  . . .  20   j  are switched-off, i.e. de-energized. For example, if it is intended to lower supporting runner  26  shown in  FIG. 3 , the position of which in vehicle  1  becomes evident from  FIG. 2 , then the two supporting magnets  20   f ,  20   g  are switched-off via computer  47 . If it is intended to lift supporting runner  26  again later on (e.g. section  45   c  in  FIG. 7 ), the mentioned supporting magnets  20   f ,  20   g  are switched-on again by means of computer  47 . Switching the supporting magnets  20   a  . . .  20   j  and/or supporting magnet halves on an off can be effected, for example, by presetting an infinitely high design value for carrier gap  7  to the control elements  30 . 
       FIG. 8  schematically shows how to compute the braking curve (e.g.  45  in  FIG. 7 ) in an individual case. According to  FIG. 4 , computer  47  is permanently fed with signals in a well known manner (e.g. DE 38 07 919 C2), which indicate the current vehicle position (line  48 ) and the current vehicle velocity (line  49 ). In the event of a disturbance which entails a shutoff of the propellant and braking system, then based on these values and based on the values saved in a computer  47  concerning the friction and wind conditions or the like to be considered in the worst case as well as based on a fixed program, the computer  47  can initially determine the nearest destination stopping point  40  eligible in the sense of the description given hereinabove (box  50  in  FIG. 8 ). Subsequently computer  47  will compute which supporting runners  26  are to be settled in an individual case and when this is to occur, i.e. the number of supporting runners  26  to be applied and the points of time at which these are to be settled will be computed (box  51  in  FIG. 8 ). It is self-evident that the computed points of time always mean that the vehicle has reached a certain location along the travel distance. 
     As a result of these computations, the control elements  30  of various control circuits  27   a  . . .  27   n  are subsequently instructed to switch the associated supporting magnets  20   a  . . .  20   j  and/or supporting magnet halves either on or off (block  52  in  FIG. 8 ). Finally, a block  53  in  FIG. 8  is to indicate that based on the relevant actual position and actual velocities of the vehicle it is constantly and newly calculated whether the braking maneuver initiated by computer  47  leads to the target and whether the vehicle is in fact so slowed down that it safely reaches the destination stopping point  40  ( FIG. 7 ) and comes to a standstill there. If required, the selected deposition procedures are frequently repeated, corrected and adapted to varying environmental conditions. 
     The described manner of braking entails various advantages. Above all it is of some advantage that the number and capacities of the required batteries can be much less than hitherto, because no electrical energy is needed for the actual braking procedure. Furthermore, owing to the plurality of existing supporting runners  26  it yields high redundancy, a reduction in production and maintenance cost because of the omission of additional braking facilities, and a uniform load distribution during the braking procedure on condition of a correct selection of settled supporting runners. The latter is preferably determined in the program of computer  47  in that it is always demanded that those carrying runners  26  on which the vehicle  1  is settled will lead to the most uniform possible load distribution (e.g. at right, left, front, rear, etc). 
     The present invention is confined to the described practical example which can be diversified in great variety. More particularly, the number of existing supporting runners  26  and their arrangement alongside of the vehicle are largely free to choose. Furthermore, it is possible to choose the relative positions of supporting magnet arrangements  5   a  . . .  5   h , supporting magnets  20   a  . . .  20   j  and supporting runners  26  in a different manner than the one shown in  FIG. 3 . Moreover, the supporting magnet arrangements  5   a  . . .  5   h  can be provided with more than two individually controllable parts and/or groups of magnet poles. It would also be possible to allocate a single supporting magnet  20   a  . . .  20   j  to each supporting runner  26 . Besides, the way of determining the braking curves and the choice of the number of settled supporting runners resulting thereof as well as of the point of time at which these are settled can largely be made dependent on the individual case and be varied. Finally, it is self-evident that the various features can also be applied in combinations other than those described and illustrated hereinabove. 
     While specific embodiments of the invention have been described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.