Rotational transducer using hall effect devices

Claim 2

A rotary transducer in which the nth harmonic is reduced to a specified fraction of its nominal value, said transducer comprising rotor and stator means, said rotor means including diametrically magnetized circular shaft means rotatable about a longitudinal axis, said stator means including a plurality of m closed loop magnetic core means magnetically coupled to said shaft means, each of said core means including a pair of magnetic pole pieces arranged diametrically across said shaft means and connected by a single return path so that substantially all of the flux entering one pole piece in a given pair flows through the same return path and the other pole piece in that pair, each of said pole pieces further having arcuate surfaces forming substantially uniform air gaps with respect to said shaft means whereby a magnetic flux is established in each core means as a function of the instantaneous rotary position of the magnetic field in said shaft means, individual ones of said core means being respectively oriented so that the phase of the varying magnetic flux in one core means is displaced 180/m degrees with respect to the phase of the flux in an adjacent core means as the shaft means is rotated, each of said magnetic pole pieces extending through a pole arc such that the integral over the pole arc of the flux corresponding to the nth harmonic is numerically equal to the specified fraction of the nominal value of said nth harmonic, Hall effect sensing means mounted in each of said core means so as to respond to the instantaneous magnitude of the flux in the respective core means, means to supply control currents to said sensing means, and means to connect output signals from said sensing means to exterior utilization apparatus.

Claim 3

The transducer of claim 1 wherein said stator means includes two magnetic core means respectively oriented so that the flux in one core means varies in phase quadrature with respect to the flux in the other core means.

Claim 4

The transducer of claim 1 wherein each of the pole pieces extends through a pole arc of 120*.

Claim 5

The transducer of claim 1 wherein each of the pole pieces extends through a pole arc of 72*.

Claim 6

Rotary transducing apparatus for providing output signals substantially free of an nth harmonic component, said transducers comprising a rotor and a stator, said rotor including a diametrically magnetized elongated circular shaft rotatable about its longitudinal axis in response to externally applied torques, said stator including a plurality of m closed loop magnetic core elements, each of said core elements consisting of a single flux path magnetically coupled to said shaft through a pair of diametrically opposed arcuate pole pieces whereby magnetic flux is established in said core elements as a function of the angular displacement of the permanent magnetic field in said shaft, said arcuate pole pieces being shaped to provide substantially uniform air gaps with respect to the surface of said shaft and extending through a pole arc equal to the pole pitch of said nth harmonic component, said core elements being oriented so that adjacent pole pieces are spaced at equiangular intervals around said shaft, each of said core elements including additional air gap means remote from said shaft and arranged so that substantially all of the flux coupled into said core element from said shaft traverses said additional air gap means, each of said core elements further including a Hall effect sensing means supportEd in said remote air gap means so as to respond to the instantaneous value of the magnetic flux flowing in the respective core element, means to apply a control current to said sensing means, and means to couple output signals from said sensing means to external utilization apparatus.

Claim 7

Rotary transducing apparatus for providing output signals substantially free of an nth harmonic component, said transducers comprising a rotor and a stator, said rotor including a diametrically magnetized elongated circular shaft rotatable about its longitudinal axis in response to externally applied torques, said stator including a plurality of m closed loop magnetic core elements, each of said core elements consisting of a single flux path magnetically coupled to said shaft through a pair of diametrically opposed arcuate pole pieces whereby magnetic flux is established in said core elements as a function of the angular displacement of the permanent magnetic field in said shaft, said arcuate pole pieces being shaped to provide substantially uniform air gaps with respect to the surface of said shaft and extending through a pole arc equal to the pole pitch of said nth harmonic component, said core elements being oriented so that adjacent pole pieces are spaced at equiangular intervals around said shaft, each of said core elements including additional air gap means remote from said shaft and arranged so that substantially all of the flux coupled into said core element from said shaft traverses said additional air gap means, each of said core elements further including a Hall effect sensing means supportEd in said remote air gap means so as to respond to the instantaneous value of the magnetic flux flowing in the respective core element, means to apply a control current to said sensing means, and means to couple output signals from said sensing means to external utilization apparatus.

Claim 8

The transducing apparatus of claim 5 wherein said stator includes two closed loop magnetic core elements oriented in space quadrature with respect to each other.

Claim 9

The apparatus of claim 5 in which the externally applied torque provides continuous rotation of said shaft and said external utilization apparatus is adapted to indicate the speed of said continuous rotation, and in which said means to apply a control current to said sensing means is an m-phase generator actuated in response to the diametrical magnetization of said shaft, each phase of said generator being coupled to the sensing means in different core elements, said transducer being further characterized in that the output signals from the sensing means in the two core elements are applied in series aiding relationship to said external utilization means.

Claim 10

The apparatus of claim 5 in which said means to apply a control current to said sensing means is a source of direct current and in which the means to provide output signals includes means to provide individual output signals from the sensing means in each of said core elements.

Claim 11

A tachometer for providing an output voltage substantially free from an nth harmonic component, said tachometer comprising an elongated circular shaft rotatable about a longitudinal axis in response to an externally applied torque, said circular shaft being permanently magnetized so as to provide a north-south magnetic axis along one diameter of said shaft, a plurality of m closed loop magnetic core elements, each of said core elements consisting of a single flux path magnetically coupled to said shaft through a pair of diametrically opposed pole pieces whereby magnetic flux is established in each of said core elements as a function of the angular displacement of said north-south magnetic axis, said pole pieces including arcuate surfaces adjacent the shaft, said arcuate surfaces having a radius centered on said longitudinal axis and a pole arc equal to the pole pitch of said nth harmonic component, said core elements being oriented so that adjacent pole pieces are spaced at equiangular intervals around said shaft, each of said core elements including an air gap remote from said pole pieces and arranged so that substantially all of the flux coupled into said core element from said shaft traverses said remote air gap, individual Hall effect sensing means inserted in each of said air gaps so as to respond to the magnetic flux in the respective core elements, each of said Hall effect sensing means including control current input terminals and a pair of output terminals, m-phase generating means magnetically coupled to said shaft for supplying polyphase sinusoidal voltages in synchronism with the rotation of said shaft, means for applying different ones of said sinusoidal voltages to the control current terminals of the Hall effect sensing means in each of the core elements, means to connect the output terminals of the sensing means in the individual core elements in series aiding relationship so as to provide a combined output voltage equal to the sum of the voltages developed across the individual sensing means.

Claim 12

A tachometer for providing an output voltage substantially free from an nth harmonic component, said tachometer comprising an elongated circular shaft rotatable about a longitudinal axis in response to an externally applied torque, said circular shaft being permanently magnetized so as to provide a north-south magnetic axis along one diameter of said shaft, a plurality of m closed loop magnetic core elements, each of said core elements consisting of a single flux path magnetically coupled to said shaft through a pair of diametrically opposed pole pieces whereby magnetic flux is established in each of said core elements as a function of the angular displacement of said north-south magnetic axis, said pole pieces including arcuate surfaces adjacent the shaft, said arcuate surfaces having a radius centered on said longitudinal axis and a pole arc equal to the pole pitch of said nth harmonic component, said core elements being oriented so that adjacent pole pieces are spaced at equiangular intervals around said shaft, each of said core elements including an air gap remote from said pole pieces and arranged so that substantially all of the flux coupled into said core element from said shaft traverses said remote air gap, individual Hall effect sensing means inserted in each of said air gaps so as to respond to the magnetic flux in the respective core elements, each of said Hall effect sensing means including control current input terminals and a pair of output terminals, m-phase generating means magnetically coupled to said shaft for supplying polyphase sinusoidal voltages in synchronism with the rotation of said shaft, means for applying different ones of said sinusoidal voltages to the control current terminals of the Hall effect sensing means in each of the core elements, means to connect the output terminals of the sensing means in the individual core elements in series aiding relationship so as to provide a combined output voltage equal to the sum of the voltages developed across the individual sensing means.

Claim 13

A resolver for providing sinusoidal output voltages substantially free from an nth harmonic component, said resolver comprising an elongated circular shaft rotatable about a longitudinal axis in response to an externally applied torque, said circular shaft being permanently magnetized so as to provide a north-south magnetic axis along one diameter of said shaft, first and second closed loop magnetic core elements, each of said magnetic core elements consisting of a single flux path magnetically coupled to said shaft through diametrically opposed pole pieces whereby magnetic flux is established in each of said core elements as a function of the angular displacement of said north-south magnetic axis, said pole pieces including arcuate surfaces adjacent the shaft, said arcuate surfaces having a radius centered on said longitudinal axis and a pole arc equal to the pole pitch of said nth harmonic component, said first and second core elements being oriented in space quadrature with respect to each other, each of said core elements including an air gap remote from said pole pieces and arranged so that substantially all of the flux coupled into said core element from said shaft traverses said remote air gap, individual Hall effect sensing means inserted in each of said air gaps so as to respond to the magnetic flux in the respective core elements, each of said Hall effect sensing means including control current input terminals and a pair of output terminals, a source of direct current coupled to the input terminals of each of said sensing means, and means for connecting the output terminals of the sensing means in each core element to individual indicating means.

Claim 14

A resolver for providing sinusoidal output voltages substantially free from an nth harmonic component, said resolver comprising an elongated circular shaft rotatable about a longitudinal axis in response to an externally applied torque, said circular shaft being permanently magnetized so as to provide a north-south magnetic axis along one diameter of said shaft, first and second closed loop magnetic core elements, each of said magnetic core elements consisting of a single flux path magnetically coupled to said shaft through diametrically opposed pole pieces whereby magnetic flux is established in each of said core elements as a function of the angular displacement of said north-south magnetic axis, said pole pieces including arcuate surfaces adjacent the shaft, said arcuate surfaces having a radius centered on said longitudinal axis and a pole arc equal to the pole pitch of said nth harmonic component, said first and second core elements being oriented in space quadrature with respect to each other, each of said core elements including an air gap remote from said pole pieces and arranged so that substantially all of the flux coupled into said core element from said shaft traverses said remote air gap, individual Hall effect sensing means inserted in each of said air gaps so as to respond to the magnetic flux in the respective core elements, each of said Hall effect sensing means including control current input terminals and a pair of output terminals, a source of direct current coupled to the input terminals of each of said sensing means, and means for connecting the output terminals of the sensing means in each core element to individual indicating means.