Light actuated brushless dc motor

Claim 2

An improved light-actuated brushless DC motor of the type which includes a permanently magnetized rotor, a plurality of stator coils, each energizable to attract the same magnetic pole of said rotor, a cylindrical coMmutating member rotatable with said rotor for modulating a light beam, sensing means responsive to modulations of said light beam, and a sequence generator for sequentially energizing said stator coils in response to successive pulses of light reaching said sensing means; the improvement comprising a plurality of light attenuating stripes on said commutating means, said stripes providing a level of attenuation different from that provided by the surface of said cylindrical commutating member, said stripes being disposed so that a stripe traverses the light beam each time that the North pole of the magnetized rotor approaches the axis of a stator coil, said plurality of stripes further including one stripe constructed so that it produces a coded pulse of light at a predetermined rotor position during each revolution, said sequence generator including means responsive to said coded pulse for clamping the sequence generator to a predetermined state regardless of the previous condition of the sequence generator.

Claim 3

The apparatus of claim 1 in which said attenuating stripes are light reflecting members having a degree of reflectivity different from that of the surface of said cylindrical commutating member.

Claim 4

The apparatus of claim 1 in which said one stripe has a high degree of reflectivity, in which the remainder of said plurality of stripes has an intermediate degree of reflectivity, and in which the surface of said cylindrical commutating member has a low degree of reflectivity.

Claim 5

The apparatus of claim 1 in which the sequence generator is a recirculating shift register having a number of stages equal to the number of stator coils, said shift register being connected so that each stage energizes the corresponding stator coil only when that stage is in the binary ONE state.

Claim 6

The apparatus of claim 3 in which said clamping means includes a threshold circuit connected to said sensing means for producing a synchronizing pulse only in response to a light pulse produced when said one stripe traverses the light beam, said clamping means further including means to set each stage of the sequence generator to a predetermined value.

Claim 7

The apparatus of claim 1 in which the sequence generator is a circulating shift register containing a clock input terminal for shifting the stable state from one value to the next in a predetermined sequence, and a synchronization input terminal for clamping the register to a predetermined binary state.

Claim 8

The apparatus of claim 5 in which the reflecting stripes all have the same high degree of reflectivity, and in which the commutating member includes first and second cylindrical sections, said first section containing only said one stripe, said second section containing the remaining stripes of said plurality, said apparatus further being characterized in that said sensing means includes first and second sensors arranged to receive pulses of light from said first and second sections respectively, said first sensor being coupled to said synchronization input terminal and said second sensor being coupled to said clock input terminal.

Claim 9

A brushless DC motor comprising a permanent magnet rotor rotatable about an axis, said rotor containing a pair of magnetic poles, a plurality of stator coils spaced at equiangular intervals around said axis, each of said coils being energizable to attract the same specified magnetic pole of said rotor, a source of radiant energy, sensing means responsive to energy from said source, cylindrical commutating means rotatable with said rotor, said cylindrical commutating means being mounted coaxially on said rotor and positioned so that some portion of its cylindrical surface is in the path of energy propagating between said source and said sensor, attenuating means distributed on the surface of said cylindrical commutating means, said attenuating means providing a level of attenuation to said radiant energy different from the attenuation provided by said cylindrical surface, said attenuating means beinG arranged on said cylindrical surface so as to traverse the beam of energy from said source as the rotor rotates whereby pulses of energy are supplied to said sensing means, said sensing means being constructed to produce electrical pulses representative of received radiant energy pulses, said attenuating means being further positioned to provide a pulse of radiant energy to said sensing means whenever said specified magnetic pole approaches the axis of a stator coil, means for providing excitation current to selected individual stator windings, sequence generating means for switching said excitation current from one stator winding to another in a predetermined cyclical sequence in response to successive pulses from said sensing means, means in said attenuating means for providing a coded pulse of radiant energy at one specific point during each revolution of the rotor and means in said sequence generating means for assuring that excitation current is applied to a specific stator coil in response to a coded pulse.

Claim 10

A brushless DC motor comprising a permanent magnet rotor rotatable about an axis, said rotor containing a pair of magnetic poles, a plurality of stator coils spaced at equiangular intervals around said axis, each of said coils being energizable to attract the same specified magnetic pole of said rotor, a source of radiant energy, sensing means responsive to energy from said source, cylindrical commutating means rotatable with said rotor, said cylindrical commutating means being mounted coaxially on said rotor and positioned so that some portion of its cylindrical surface is in the path of energy propagating between said source and said sensor, attenuating means distributed on the surface of said cylindrical commutating means, said attenuating means providing a level of attenuation to said radiant energy different from the attenuation provided by said cylindrical surface, said attenuating means beinG arranged on said cylindrical surface so as to traverse the beam of energy from said source as the rotor rotates whereby pulses of energy are supplied to said sensing means, said sensing means being constructed to produce electrical pulses representative of received radiant energy pulses, said attenuating means being further positioned to provide a pulse of radiant energy to said sensing means whenever said specified magnetic pole approaches the axis of a stator coil, means for providing excitation current to selected individual stator windings, sequence generating means for switching said excitation current from one stator winding to another in a predetermined cyclical sequence in response to successive pulses from said sensing means, means in said attenuating means for providing a coded pulse of radiant energy at one specific point during each revolution of the rotor and means in said sequence generating means for assuring that excitation current is applied to a specific stator coil in response to a coded pulse.