Servomotor control systems - Patent Review 4661756

Claims

We claim:

1. A control system for a variable reluctance electrical machine having driving member pole windings, comprising power supply means including voltage source means connectible across said driving member pole windings of said machine in a predetermined sequence and for a predetermined increment of displacement of a driven member of the machine and means for regulating the instantaneous magnitude of the current in one of said driving member pole windings when connected to said voltage source means, the control system also comprising driven member position-sensing means for generating at least one signal, the instantaneous value of which is dependent on the position of the driven member, for providing driven member position information at a succession of intervals within each said predetermined increment of driven member displacement during which one of said driving member pole windings is connectible to said voltage source means, said current-regulating means including means for generating relative current magnitudes for each of a plurality of positions of the driven member in accordance with the instantaneous value of said at least one signal of the driven member position-sensing means and means for forcing the instantaneous magnitude of the current in one of said driving member pole windings when connected to said voltage source means to track said relative current magnitudes so that the instantaneous value of said current set by said regulating means at any position of the driven member within said increment of driven member displacement during which the winding is connectible to said voltage source means relative to its value at any other said position is substantially determined by the instantaneous position of the driven member within said increment of driven member displacement, and the system further including means for providing a speed signal, the magnitude of which is indicative of the speed of driven member displacement and the polarity of which is indicative of the direction of driven member displacement, the power supply means including means for combining said speed signal with a speed demand signal to produce a speed error signal of variable magnitude and polarity, said speed error signal defining a direction input of variable polarity which is applied to said relative current magnitude generating means and said generating means being responsive to the polarity of said direction input for selection of current magnitudes appropriate to the direction of driven member displacement as indicated by the polarity of said speed error signal.

2. A control system according to claim 1, wherein said relative current magnitude generating means includes memory means for storing digitized relative current magnitudes for each of a plurality of positions of the driven member and for recall in appropriate sequence in accordance with the instantaneous value of said at least one signal of the driven member position-sensing means and said direction input is applied to said memory means, said memory means being responsive to the polarity of said direction input for recall of digitized current magnitudes appropriate to the direction of driven member displacement as indicated by the polarity of said speed error signal.

3. A control system for a variable reluctance electrical machine having a rotor and a plurality of stator pole windings, said system comprising power supply means including voltage source means connectible across said stator pole windings of said machine in a predetermined sequence and for a predetermined angular increment of rotation of the rotor of the machine and means for regulating the instantaneous magnitude of the current in one of said stator pole windings when connected to said voltage source means, the control system also comprising rotor position-sensing means for generating at least one signal, the instantaneous value of which is dependent on the position of the rotor, and for providing rotor position information at a succession of intervals within each said angular increment of rotor rotation during which one of said stator pole windings is connectible to said voltage source means, said current-regulating means including means for generating relative current magnitudes for each of a plurality of positions of the rotor in accordance with the instantaneous value of said at least one signal of the rotor position-sensing means and means for forcing the instantaneous magnitude of the current in a stator pole winding when connected to said voltage source means to track said relative current magnitudes so that the instantaneous value of said current set by said regulating means at any position of the rotor within said angular increment of rotor rotation during which the winding is connectible to said voltage source means relative to its value at any other said position is substantially determined by the instantaneous position of the rotor within said angular increment of rotor rotation, and the system further including means for providing a speed signal, the magnitude of which is indicative of the speed of rotor rotation and the polarity of which is indicative of the direction of rotor rotation, the power supply means including means for combining said speed signal with a speed demand signal to produce a speed error signal of variable magnitude and polarity, said speed error signal defining a direction input of variable polarity which is applied to said relative current magnitude generating means and said generating means being responsive to the polarity of said direction input for selection of current magnitudes appropriate to the direction of rotor rotation as indicated by the polarity of said speed error signal.

4. A control system according to claim 3, wherein said relative current magnitude generating means includes memory means for storing digitized relative current magnitudes for each of a plurality of positions of the rotor and for recall in appropriate sequence in accordance with the instantaneous value of said at least one signal of the rotor position-sensing means and said direction input is applied to said memory means, said memory means being responsive to the polarity of said direction input for recall of digitized current magnitudes appropriate to the direction of rotor rotation as indicated by the polarity of said speed error signal.

5. A control system according to claim 3, including means for modulating said speed error signal within a predetermined range of magnitudes of said signal so that said direction input is modulated and said relative current magnitude generating means is responsive to said modulated direction input for alternating selection of relative current magnitudes for rotor rotation in opposite directions when said speed error signal is within said predetermined range of magnitudes.

6. A control system according to claim 3, wherein said speed error signal also defines a torque demand signal and said current-magnitude-forcing means is responsive to the magnitude of said torque demand signal to regulate said stator winding current so that the absolute magnitude of said current at every angular position of the rotor within said angular increment of rotor rotation during which the winding is connectible to said voltage source means is substantially determined by the magnitude of said torque demand signal.

7. A control system according to claim 3, wherein the power supply means includes means for combining said speed error signal with a bias signal to define a torque demand signal, and said current-magnitude-forcing means is responsive to the magnitude of said torque demand signal to regulate said stator winding current so that the absolute magnitude of said current at every angular position of the rotor within said angular increment of rotor rotation during which the winding is connectible to said voltage source means is substantially determined by the magnitude of said torque demand signal.

8. A control system according to claim 7, including means for modulating said speed error signal within a predetermined range of magnitudes of said signal so that said direction input is modulated and said relative current magnitude generating means is responsive to said modulated direction input for alternating selection of relative current magnitudes for rotor rotation in opposite directions when said speed error signal is within said predetermined range of magnitudes.

9. A control system according to claim 8, wherein said predetermined range of magnitudes of said speed error signal extends about a zero value of said signal.

10. A drive system comprising a saturable variable reluctance electrical machine, said electrical machine comprising a stationary or driving member having a plurality of salient driving poles, a magnetizing winding for each driving pole, a movable or driven member having a plurality of salient driven poles, the number of driven poles being less than the number of driving poles, and a plurality of airgaps, the airgap between each driving pole and a driven pole positioned in alignment therewith being small relative to the dimensions of the poles transverse to said airgap and at least the driven poles being formed so that in operation of the machine magnetic saturation occurs substantially in a region of the mechanically variable interface or overlap between the driving and driven poles, and the extents and dispositions of the driven poles being related to those of the driving poles so that in operation of the machine, a force-producing increment of driven member displacement resulting from the mechanical interface or overlap of each driven pole with a driving pole overlaps a force-producing increment of driven member displacement resulting from the overlap of another driven pole with a further driving pole, and the system also comprising driven member positioning-sensing means for generating at least one signal, the instantaneous value of which is dependent on the position of the driven member, and for providing driven member position information at a succession of intervals within a predetermined increment of driven member displacement during which a driving pole winding is connectible to a voltage source means, and power supply means including said voltage source means connectible across the driving pole windings, said windings being connectible across said voltage source means in a predetermined sequence during driven member displacement and each driving pole winding being thus connectible for a predetermined increment of driven member displacement, the power supply means including means for regulating the instantaneous magnitude of the current in one of said driving member windings when connected to said voltage source means, said current-regulating means including means for generating relative current magnitudes for each of a plurality of positions of the driven member in accordance with the instantaneous value of said at least one signal of the driven member position-sensing means and means for forcing the instantaneous magnitude of the current in one of said driving pole windings when connected to said voltage source means to track said relative current magnitudes so that the instantaneous value of said current set by said regulating means at any position of the driven member within said increment of driven member displacement during which the winding is connectible to said voltage source means relative to its value at any other said position is substantially determined by the instantaneous position of the driven member within said increment of driven member displacement, and the system further including means for providing a speed signal, the magnitude of which is indicative of the speed of driven member displacement and the polarity of which is indicative of the direction of driven member displacement, the power supply means including means for combining said speed signal with a speed demand signal to produce a speed error signal of variable magnitude and polarity, said speed error signal defining a direction input of variable polarity which is applied to said relative current magnitude generating means and said generating means being responsive to the polarity of said direction input for selection of current magnitudes appropriate to the direction of driven member displacement as indicated by the polarity of said speed error signal.

11. A drive system comprising a saturable variable reluctance electrical machine, said electrical machine comprising a stator having a plurality of salient stator poles, a magnetizing winding for each stator pole, a rotor having a plurality of salient rotor poles, the number of rotor poles being less than the number of stator poles, a radial airgap between each stator pole and a rotor pole positioned in alignment therewith being small relative to the dimensions of the poles transverse to said airgap and at least the rotor poles being formed so that in operation of the machine magnetic saturation occurs substantially in a region of the mechanically variable interface or overlap between the stator and the rotor poles, and the arcuate extents and dispositions of the rotor poles being related to those of the stator poles so that in operation of the machine, a torque-producing angular increment of rotor rotation resulting from the mechanical interface or overlap of each rotor pole with a stator pole overlaps a torque-producing angular increment of rotor rotation resulting from the overlap of another rotor pole with a further stator pole, and the system also comprising rotor position-sensing means for generating at least one signal, the instantaneous value of which is dependent on the position of the rotor, and for providing rotor position information at a succession of intervals within a predetermined angular increment of rotor rotation during which a stator pole winding is connectible to a voltage source means, and power supply means including said voltage source means connectible across the stator pole windings, said windings being connectible across said voltage source means in a predetermined sequence during rotor rotation and each stator pole winding being thus connectible for said predetermined angular increment of rotor rotation, the power supply means including means for regulating the instantaneous magnitude of the current in a stator pole winding when connected to said voltage source means, said current-regulating means including means for generating relative current magnitudes for each of a plurality of positions of the rotor in accordance with the instantaneous value of said at least one signal of the rotor position-sensing means and means for forcing the instantaneous magnitude of the current in one of said stator pole windings when connected to said voltage source means to track said relative current magnitudes so that the instantaneous value of said current set by said regulating means at any position of the rotor within said angular increment of rotor rotation during which the winding is connectible to said voltage source means relative to its value at any other said position is substantially determined by the instantaneous position of the rotor within said angular increment of rotor rotation, and the system further including means for providing a speed signal, the magnitude of which is indicative of the speed of rotor rotation and the polarity of which is indicative of the direction of rotor rotation, the power supply means including means for combining said speed signal with a speed demand signal to produce a speed error signal of variable magnitude and polarity, said speed error signal defining a direction input of variable polarity which is applied to said relative current magnitude generating means and said generating means being responsive to the polarity of said direction input for recall of relative current magnitudes appropriate to the direction of rotor rotation as indicated by the polarity of said speed error signal.

12. A drive system according to claim 11, wherein said relative current magnitude generating means includes memory means for storing digitized relative current magnitudes for each of a plurality of positions of the rotor and for recall in appropriate sequence in accordance with the instantaneous value of said at least one signal of the rotor position-sensing means and said direction input is applied to said memory means, said memory means being responsive to the polarity of said direction input for recall of digitized current magnitudes appropriate to the direction of rotor rotation as indicated by the polarity of said speed error signal.

13. A drive system according to claim 11, including means for modulating said speed error signal within a predetermined range of magnitudes of said signal so that said direction input is modulated and said relative current magnitude generating means is responsive to said modulated direction input for alternating selection of relative current magnitudes for rotor rotation in opposite directions when said error signal is within said predetermined range of magnitudes.

14. A control system according to claim 13, wherein said predetermined range of magnitudes of said speed error signal extends about a zero value of said signal.

15. A drive system according to claim 13, wherein said predetermined range of magnitudes of said speed error signal extends about a zero value of said signal.

16. A drive system according to claim 11, wherein said speed error signal also defines a torque demand signal and said current-magnitude-forcing means is responsive to the magnitude of said torque demand signal to regulate said stator winding current so that the absolute magnitude of said current at every angular position of the rotor within said angular increment of rotor rotation during which the winding is connectible to said voltage source means is substantially determined by the magnitude of said torgue demand signal.

17. A drive system according to claim 11, wherein the power supply means includes means for combining said speed error signal with a bias signal to define a torque demand signal and said current-magnitude-forcing means is responsive to the magnitude of said torque demand signal to regulate said stator winding current so that the absolute magnitude of said current at every angular position of the rotor within said angular increment of rotor rotation during which the winding is connectible to said voltage source means is substantially determined by the magnitude of said torque demand signal.

18. A drive system according to claim 17, including means for modulating said speed error signal within a predetermined range of magnitudes of said signal so that said direction input is modulated and said relative current magnitude generating means is responsive to said modulated direction input for alternating selection of relative current magnitudes for rotor rotation in opposite directions when said speed error signal is within said predetermined range of magnitudes.

19. A drive system according to claim 18, wherein said predetermined range of magnitudes of said speed error signal extends about a zero value of said signal.

20. A drive system comprising a saturable variable reluctance electrical machine, said electrical machine comprising a stationary or driving member having a plurality of salient driving poles, a magnetizing winding for each driving pole, a movable or driven member having a plurality of salient driven poles, the number of driven poles being less than the number of driving poles, and a plurality of airgaps, the airgap between each driving pole and a driven pole positioned in alignment therewith being small relative to the dimensions of the poles transverse to said airgap and at least the driven poles being formed so that in operation of the machine, magnetic saturation occurs substantially in a region of the mechanically variable interface or overlap between the driving and driven poles, and the extents and dispositions of the driven poles being related to those of the driving poles so that in operation of the machine, a force-producing increment of driven member displacement resulting from the mechanical interface or overlap of each driven pole with a driving pole overlaps a force-producing increment of driven member displacement resulting from the overlap of another driven pole with a further driving pole, and the system also comprising power supply means including voltage source means connectible across the driving pole windings, said windings being connectible across said voltage source means in a predetermined sequence during driven member displacement and each driving pole winding being thus connectible for a predetermined increment of driven member displacement, and driven member positioning-sensing means for generating at least one signal, the instantaneous value of which is dependent on the position of the driven member, for providing driven member position information at a succession of intervals within each said predetermined increment of driven member displacement during which a driving pole winding is connectible to said voltage source means, the power supply means also including means for regulating the instantaneous magnitude of the current in a driving member winding when connected to said voltage source means, said current-regulating means including memory means for storing digitized relative current magnitudes for each of a plurality of positions of the driven member and for recall in appropriate sequence in accordance with the instantaneous value of said at least one signal of the driven member position-sensing means and means for forcing the instantaneous magnitude of the current in a driving pole winding when connected to said voltage source means to track said relative current magnitudes so that the instantaneous value of said current set by said regulating means at any position of the driven member within said increment of driven member displacement during which the winding is connectible to said voltage source means relative to its value at any other said position is substantially determined by the instantaneous position of the driven member within said increment of driven member displacement.

21. A drive system comprising a saturable variable reluctance electrical machine, said electrical machine comprising a stator having a plurality of salient stator poles, a magnetizing winding for each stator pole, a rotor having a plurality of salient rotor poles, the number of rotor poles being less than the number of stator poles, a radial airgap between each stator pole and a rotor pole positioned in alignment therewith being small relative to the dimensions of the poles transverse to said airgap and at least the rotor poles being formed so that in operation of the machine magnetic saturation occurs substantially in a region of the mechanically variable interface or overlap between the stator and rotor poles, and the arcuate extents and dispositions of the rotor poles being related to those of the stator poles so that in operation of the machine, a torque-producing angular increment of rotor rotation resulting from the mechanical interface or overlap of each rotor pole with a stator pole overlaps a torque-producing angular increment of rotor rotation resulting from the overlap of another rotor pole with a further stator pole, and the system also comprising power supply means including voltage source means connectible across the stator pole windings, said windings being connectible across said vol