Automatic control system and valve actuator

An automatic control system for a motor having at least one stator winding and a rotor, comprising:

• a commutating disk attached to the rotor for rotation therewith;
• a plurality of commutating channels equal in number to the number of stator windings;
• each of said commutating channels responsive to the movement of said commutating disk to generate one component of a voltage representing a first part of a plural part control signal;
• input circuit means responsive to an input rotor position control signal and a rotor position feedback signal for generating a second part of the plural part control signal;
• decoder means incuding means for selecting one of the plurality of stator windings and responsive to the first and second parts of the plural part control signal for generating a time varying voltage for each winding of the stator;
• each time varying voltage having a time displacement with respect to the voltage of each of the other stator windings of said motor;
• a power stage responsive to the time varying voltage for each winding to generate a motor winding voltage to be applied thereto;
• said power stage including first and second amplifier channels, said first amplifier channel connecting a winding to a power supply, said second amplifier channel connecting said winding to ground;
• means for interconnecting said amplifier channels to alternately prevent one or the other of said amplifier channels from operating in a conduction mode;
• said means for interconnecting including means connected from a last stage of said first amplifier channel to a first stage of said second amplifier channel for blocking the operation of said second amplifier channel during the operation of said first amplifier channel;
• and
• said means for interconnecting also including means connected from a last stage of said second amplifier channel to a first stage of said first amplifier channel for blocking the operation of said first amplifier channel during the operation of said second amplifier channel.

An actuator for providing a mechanical output motion to positioning apparatus, said output motion related to an input control signal, comprising:

• a housing having an internal bearing support with a center opening and extending into said housing from one end thereof;
• a cylindrical motor stator mounted concentric with the bearing support in said housing and including at least one stator winding;
• a permanent magnet rotor having a cylindrical, cup-shaped configuration positioned concentric with said motor stator and the internal bearing support of said housing;
• an output shaft fastened to said rotor and passing through the opening of the internal bearing support and extending from said housing to be coupled to the positioning apparatus;
• rotor bearings mounted to said output shaft and mounted in the opening of the internal bearing support;
• means for commutating the rotational motion of the rotor into a commutating signal;
• a source capable of providing an input control signal;
• circuit means mounted within said housing and responsive to the input control signal and the commutating signal to generate a motor winding voltage for each winding of said stator;
• a rotational to linear motion converter comprising a ballscrew, said ballscrew coupled to said output shaft for providing a linear motion thereof related to said input control signal;
• and
• means for biasing said ballscrew to extend said output shaft during a power failure condition.