Apparatus measuring relative velocity of movable members including means to detect velocity from the position encoder

Abstract

A transducer coupled to a motor shaft provides both position and velocity information for use in a closed loop control system. The transducer includes a disk with deposited metallic parallel conductors each conductor carrying current in a direction opposite to the adjacent conductor. Relative movement of one disk with respect to another produces a position signal in a manner well known in the art. However, multiple windings are used to provide multiple position signals displaced in space phase which are then processed by differentiation and commutation to provide a velocity signal used as a control voltage in the control loop. A reference signal is also derived by commutation from the position signal.

I claim: .[.1. Apparatus for the measurement of relative velocity between two relatively movable members comprising: a winding coupled to one of said members including a plurality of substantially parallel conductors each series connected to its next adjacent conductor whereby adjacent conductors of the winding carry currents in opposite directions; a winding coupled to the other of said members including a plurality of substantially parallel conductors each series connected to its adjacent conductor; means for applying an electric signal to one of said windings; and means for juxtaposing said windings in an inductive relationship for producing an electric alternating position signal from said other winding in response to relative movement between the winding said electric signal of said one winding inducing said position signal in said other winding, said position signal having periods inversely proportional to the relative velocity between said members, the peak amplitude of said position signal being substantially constant with changes in velocity and the slope of said position signal at its zero crossing being proportional to instantaneous relative velocity; means for deriving from said slope information of said position signal a velocity signal whose magnitude is related to velocity, means for deriving a reference signal from said position signal said reference signal having periods proportional to said periods of said position signal, and means for comparing said reference signal with said velocity signal to provide an error signal..]. .[.2. Apparatus as in claim 1 where said deriving means for said velocity signal includes means for differentiating said position signal with respect to time to provide a velocity signal whose maximum instantaneous magnitudes are proportional to instantaneous velocity..]. .[.3. Apparatus as in claim 1 together with servomotor means responsive to said error signal and coupled to a load to which one of said relatively movable members is mechanically connected..]. .[.4. Apparatus as in claim 1 in which said relatively movable members move in rotation and said windings comprise circular arrays of substantially parallel conductors, said circular arrays being concentric with the axis of said rotation..]. .[.5. Apparatus as in claim 1 together with at least one additional winding on said other member in predetermined space phase to provide an additional position signal..]. .[.6. Apparatus as in claim 5 where said winding on said other member and said additional winding are interleaved in substantially a common plane, such windings also being electrically independent of each other..]. .[.7. Apparatus as in claim 6 where each of said windings include four segments in space phase opposition but include electrical interconnection means to produce aiding signals said interconnection means providing gaps between segments for the interleaving of the other of said windings said interconnection means providing a single conductor in proximity to said segments which conducts current in a direction opposite to said segment, said single conductor also being located on alternate sides of successive segments of a winding said interconnection means also bridging said gaps 
     
        by a pair of conductors having opposed currents..]. 8. Apparatus for the measurement of relative velocity between two relatively movable members comprising.[.;.]..Iadd.: .Iaddend.a first winding coupled to one of said members including a plurality of substantially parallel conductors each series connected to its next adjacent conductor whereby adjacent conductors of the winding carry currents in opposite direction; means for applying an electric signal to said first winding; a plurality of windings coupled to said other of said members said windings being arranged in a predetermined space phase with respect to each other; means for juxtaposing said windings in an inductive relationship for respectively producing electric alternating position signals from said plurality of windings in response to relative movement between the windings, said electric signal of said .[.one.]. .Iadd.first .Iaddend.winding inducing said position .[.signal.]. .Iadd.signals .Iaddend.in said other windings, said position signals having periods inversely proportional to the relative velocity between said members the peak amplitude of said position signals being substantially constant with changes in velocity and the slope of said position signals at their zero crossing being proportional to instantaneous relative velocity; means for deriving a velocity signal from said slope information of said position signals including means for differentiating said position signals with respect to time to provide a plurality of velocity signals in said predetermined space phase whose .[.maximum.]. instantaneous magnitudes are proportional to instantaneous velocity.[.;.]..Iadd., and .Iaddend.means for commutating said velocity signals around their maximum amplitudes to provide a unidirectional velocity ripple signal; means for deriving a reference signal from said position signals including means for sampling the peak amplitudes of said position .[.signal.]. .Iadd.signals .Iaddend.to provide a unidirectional reference ripple signal .[.similar to said velocity ripple signal.]. and means for comparing said velocity ripple signal with said reference ripple 
     
     
        signal to provide an error signal. 9. Apparatus as in claim 8 where said plurality of windings consists of second and third windings which are in 
     
     
        space quadrature. 10. Apparatus as in claim 8 together with means for inverting at least a portion of said velocity signals and commutating such signal along with the non-inverted velocity signals. .[.11. Apparatus for the control of relative position and relative velocity between two relatively movable members comprising: transducer means coupled to said movable members producing an electric alternating position signal having periods inversely proportional to the velocity between said members, the peak amplitudes of said position signal being substantially constant with changes in velocity and the slope of said position signal at its zero crossing being proportional to instantaneous relative velocity, means for deriving from said slope information of said position signal a velocity signal said deriving means including means for differentiating said position signal with respect to time to provide said velocity signal whose maximum instantaneous magnitudes are proportional to instantaneous velocity and which provides a continuous indication of velocity, means for deriving a reference signal from said position signal said reference signal having periods proportional to said periods of said position signal and an amplitude proportional to the amplitude of said position signal, means for comparing said reference signal with said velocity signal to provide an error signal, and motor means for providing said relative velocity between said two movable members said motor means being responsive to said error signal to vary said relative velocity in a manner to minimize said error signal said continuous indication of velocity maintaining, in cooperation with said reference signal, said relative 
     
     
        velocity at a desired level..]. 12. Apparatus as in claim 11 including means for adjusting said reference signal for controlling said relative velocity and together with homing switch means for coupling said position signal to said comparing means for causing said relative velocity to be reduced to zero. .[.13. Apparatus as in claim 11 including commutating means for commutating said peak amplitudes of said position signal to provide said reference signal and for commutating the peak amplitudes of the differentiated position signal for providing said velocity signal..]. 
     
     
         4. Apparatus as in claim .[.11.]. .Iadd.21 .Iaddend.where said position .[.signals are.]. .Iadd.signal is .Iaddend.in the form of .[.mudulated.]. .Iadd.a modulated .Iaddend.carrier together with means for demodulating 
     
     
        .[.such signals.]. .Iadd.said position signal.Iaddend. . 15. Apparatus as in claim .[.11.]. .Iadd.21 .Iaddend.where said .[.velocity signal deriving means includes commutating.]. .Iadd.first .Iaddend.means .Iadd.for commutating is .Iaddend.driven by said position signal for selecting segments of said differentiated position signal around the maximum amplitudes of .[.such.]. .Iadd.said .Iaddend.differentiated .Iadd.position .Iaddend.signal said .Iadd.first .Iaddend.commutating means combining such segments in a piecewise continuous velocity signal of constant polarity for each direction of velocity, and .[.together with commutating.]. .Iadd.where said second .Iaddend.means .[.included in said means for deriving said reference signal.]. .Iadd.for commutating includes means .Iaddend.for selecting segments around the maximum amplitude of said position signal to form a piecewise continuous reference signal. .[.16. Apparatus as in claim 2 where said deriving means includes commutating means for selecting segments of said differentiated position signal around the maximum amplitudes of such differentiated signal said commutating means combining such segments in a piecewise continuous velocity signal of constant polarity for a single direction of velocity..]. .[.17. Apparatus for the control of relative position and relative velocity between two relatively movable members comprising: transducer means coupled to said movable members producing an electric alternating position signal in response to said relative movement, said position signal having periods inversely proportional to the velocity between said members, the peak amplitude of said position signal being substantially constant with changes in velocity and the slope of said position signal at its zero crossing being proportional to instantaneous relative velocity, means for deriving from said slope information of said position signal a velocity signal whose maximum instantaneous magnitude are proportional to instantaneous velocity and which provides a continuous indication of velocity, means for deriving a reference signal from said position signal said reference signal having periods proportional to said periods of said position signal and an amplitude proportional to the amplitude of said position signal, and means for comparing said reference signal with said velocity signal to provide an error signal said continuous indication of velocity maintaining, in cooperation with said reference signal, said relative velocity at a desired level..]. .[.18. Apparatus as in claim 17 where said deriving means includes means for differentiating said position signal with respect to time and commutating means for selecting segments of said differentiated position signal around the maximum amplitudes of such differentiated signal said commutating means combining such segments in a piecewise continuous velocity signal of constant polarity for a single direction of velocity..]. .[.19. Apparatus as in claim 17 where said means for deriving said reference signal includes commutating means for selecting segments around the maximum amplitudes of said position signal to form a piecewise continuous reference signal..]. .[.20. Apparatus as in claim 17 where said transducer means produces at least two position signals in space phase and said velocity and reference signals are derived from such position signals..]. .Iadd. 21. Apparatus for the control of relative position and relative velocity between two relatively movable members, comprising: transducer means coupled to said movable members for producing an electric alternating position signal having periods inversely proportional to the velocity between said members, the peak amplitudes of said positional signal being substantially constant with changes in velocity and the slope of said position signal at its zero crossing being proportional to instantaneous relative velocity;   means for deriving from said slope information of said position signal a velocity signal, said deriving means including means for differentiating said position signal with respect to time and first means for commutating the peak amplitudes of said differentiated position signal to provide said velocity signal whose instantaneous magnitudes are proportional to instantaneous velocity and which provides a continuous indication of velocity;   means for deriving a reference signal from said position signal, said means for deriving including second means for commutating the peak amplitudes of said position signal to provide said reference signal whose periods are proportional to the periods of said position signal and whose amplitude is proportional to the amplitude of said position signal;   means for comparing said reference signal with said velocity signal to provide an error signal; and   motor means for providing said relative velocity between said two movable members, said motor means being responsive to said error signal to vary said relative velocity in a manner to minimize said error signal.   
     
     
        .Iaddend. .Iadd. 22.  Apparatus for the measurement of relative velocity between two relatively movable members, comprising: transducer means coupled to said relatively movable members for producing a plurality of mutually phase-displaced electrical alternating position signals, said position signals being of substantially identical peak amplitude and frequency, said frequency being proportional to the relative velocity between said members and said peak amplitude being substantially constant with changes in velocity, the slope of each position signal at its zero-crossing being proportional to instantaneous relative velocity;   means for deriving from the slope information of said position signals a velocity signal that provides a continuous indication of the relative velocity between said members, said means for deriving comprising means for differentiating said position signals with respect to time to provide a plurality of phase-displaced rate signals whose instantaneous magnitudes are proportional to instantaneous velocity, and means for commutating said rate signals around their maximum amplitudes to provide said velocity signal;   means for deriving a reference signal from said position signals by commutating said position signals around the maximum amplitudes; and   means for comparing said velocity signal with said reference signal to provide an error signal representative of the difference between the actual relative velocity between said members and a desired relative velocity. .Iaddend.