Electric linear motor

Abstract

The invention refers to an electric linear motor comprising a longitudinal stator beam; at least one mover adapted to move along the stator beam; which stator beam comprises at least two side faces located at opposite sides of the stator beam, each of the side faces carrying ferromagnetic poles spaced apart by a pitch, and which mover comprises at least two counter-faces facing the respective side faces of the stator beam, wherein the at least two side faces, as well as the at least two counter-faces facing the respective side faces, are inclined or offset with respect to each other.

1 . An electric linear motor, comprising
 a longitudinal stator beam;   at least one mover adapted to move along the stator beam;   which stator beam comprises at least two side faces located at opposite sides of the stator beam, each of the side faces carrying ferromagnetic poles spaced apart by a pitch,   and which mover comprises at least two counter-faces facing the respective side faces of the stator beam,   wherein the at least two side faces, as well as the at least two counter-faces facing the respective side faces, are inclined or offset with respect to each other.   
     
     
         2 . The electric linear motor according to  claim 1 , wherein the mover has in at least one of said counter-faces at least one rotor unit having at least one winding and at least one permanent magnet, which are arranged to co-act with the ferromagnetic poles of the respective side face of the stator beam. 
     
     
         3 . The electric linear motor according to  claim 1 , wherein the mover has in each of said counter-faces at least one rotor unit having at least one winding and at least one permanent magnet, which are arranged to co-act with the ferromagnetic poles of the respective side face of the stator beam. 
     
     
         4 . The electric linear motor according to  claim 1 , wherein the stator beam comprises at least four side faces located two by two at opposite sides of the stator beam, such that the four side faces substantially cover circumference of the stator beam, and wherein the mover comprises at least four counter-faces facing the respective side faces of the stator beam,
 and wherein the side faces located at opposite sides of the stator beam, as well as the counter-faces facing said side faces, are inclined or offset with respect to each other.   
     
     
         5 . The electric linear motor according to  claim 4 , wherein each of the side faces carries ferromagnetic poles spaced apart by a pitch, and wherein the mover has in each of said counter-faces at least one rotor unit having at least one winding and at least one permanent magnet, which are arranged to co-act with the ferromagnetic poles of the respective side face of the stator beam. 
     
     
         6 . The electric linear motor according to  claim 1 , wherein the ferromagnetic poles are teeth provided on a side face of a ferromagnetic stator rod, which teeth which are spaced apart by teeth gaps. 
     
     
         7 . The electric linear motor according to  claim 1 , wherein the side-faces carrying ferromagnetic poles of the stator beam do not have any permanent magnets as well as no windings either. 
     
     
         8 . The electric linear motor according to  claim 1 , wherein each of said rotor units comprises permanent magnets as well as motor winding, preferably three-phase motor winding. 
     
     
         9 . The electric linear motor according to  claim 1 , wherein the mover has in each of said counter-faces at least two rotor units arranged consecutively in the travelling direction, each of said rotor units having at least one winding and at least one permanent magnet, which are arranged to co-act with the ferromagnetic poles of the respective side face of the stator beam. 
     
     
         10 . The electric linear motor according to  claim 1 , wherein each of said rotor units contains at least two rotors having windings connected in series or in parallel. 
     
     
         11 . A control apparatus of an electric linear motor according to  claim 1 , wherein the control apparatus comprises at least one drive unit configured to supply electrical power to the respective at least one rotor unit of the mover. 
     
     
         12 . The control apparatus of  claim 11 , wherein the control apparatus comprises drive units configured to supply electrical power separately to the respective rotor units of the mover such that each rotor unit is supplied by a separate drive unit. 
     
     
         13 . A transport system comprising an electric linear motor and a control apparatus according to  claim 11 , the transport system further comprising:
 a mobile load-receiving part coupled to the mover and arranged to travel along a trajectory defined by the stator beam by means of the propulsion force of the mover.   
     
     
         14 . A method of controlling the electric linear motor with a control apparatus according to  claim 11 , the method comprising
 obtaining position information of the mutual position of the ferromagnetic poles and the at least one rotor unit facing said ferromagnetic poles, the position information being obtained in the travelling direction of the rotor unit   representing d, q-coordinate system of said at least one rotor unit by means of the position information such that the d-axis of said rotor unit is in the direction of the ferromagnetic poles facing the rotor unit and the q-axis is orthogonal to the d-axis   obtaining information of length of air gap between the ferromagnetic poles and the at least one rotor unit facing said ferromagnetic poles   supplying, by means of the at least one drive unit a d-axis current component to the at least one winding of the at least one rotor unit to adjust the length of air gap towards given reference value wherein the d-axis current component is established based on the difference between air gap reference value and obtained air gap length information.   
     
     
         15 . The method according to  claim 14 , comprising:
 obtaining position information of mutual position of ferromagnetic poles located at opposite sides of the stator beam and the rotor units facing said ferromagnetic poles, the position information being obtained in the travelling direction of the rotor unit   representing d, q-coordinate systems of said rotor units by means of the position information such that the d-axis of each said rotor unit is in the direction of the ferromagnetic poles facing the rotor unit and the q-axis is orthogonal to the d-axis   obtaining information of length of air gap between the ferromagnetic poles and the rotor units facing said ferromagnetic poles   supplying, by means of the drive units separate d-axis current components to the windings of the rotor units at opposite sides of the stator beam to adjust the length of air gaps towards given reference values, wherein the separate d-axis current components are established based on the difference between air gap reference value and obtained air gap length information.   
     
     
         16 . The method according to  claim 14 , wherein the mover has in at least one of said counter-faces at least two rotor units arranged consecutively in the travelling direction, each of said rotor units having at least one winding and at least one permanent magnet, which are arranged to co-act with the ferromagnetic poles of the respective side face of the stator beam,
 and wherein the control apparatus comprises drive units configured to supply electrical power separately to the respective rotor units of the same counter-face, the method comprising:   supplying by means of the drive units separate d-axis current components to the windings of rotor units of the same counter-face to straighten tilt of the air gap, the separate d-axis current components being established based on difference between air gap reference value and air gap length information.   
     
     
         17 . The method according to  claim 14 , comprising:
 obtaining travel position information and/or travel speed information of the mover   feeding with the at least one drive unit to the at least one winding of the at least one rotor unit a q-axis current component based on the difference between travel position reference and obtained travel position information and/or travel speed reference and obtained travel speed information to adjust the travel position and/or speed towards said position and/or speed reference.   
     
     
         18 . The method according to  claim 17 , comprising:
 feeding with the drive units to the windings of rotor units separate q-axis current components based on the difference between travel position reference and obtained travel position information and/or travel speed reference and obtained travel speed information to adjust the travel position and/or speed towards said position and/or speed reference.   
     
     
         19 . The method according to  claim 14 , comprising:
 changing at least one of d-axis current component and q-axis current component of a rotor unit responsive to change of at least one of travel position information, travel speed information and air gap length information   when changing the at least one of d-axis current component and q-axis current component, providing at the same time a correction term to the other of the d-axis current component and the q-axis current component to compensate the effect of change to the attraction force and/or propulsion force of the mover.   
     
     
         20 . The method according to  claim 14 , comprising:
 calculating a propulsion force reference value based on difference between travel position reference and obtained travel position information and/or between travel speed reference and obtained travel speed information of the mover   calculating an attraction force reference value based at least on difference between air gap reference value and air gap length information   changing at least one of d-axis current component and q-axis current component of a rotor unit responsive to change in at least one of propulsion force reference value, attraction force reference value and air gap length information of the rotor unit.