Electrical apparatus for angularly positioning a shaft in dependence upon input digital signals

Claim 1

ELECTRICAL APPARATUS FOR ANGULARLY POSITIONING A SHAFT IN DEPENDENCE UPON INPUT DIGITAL SIGNALS, COMPRISING AN ELECTRIC MOTOR FOR ROTATING TO SHAFT, MEANS FOR SUPPLYING TWO SIGNALS THAT ARE TOGETHER REPRESENTATIVE OF A SHAFT POSITION VECTOR AS DEMANDED BY THE DIGITAL VALUES OF A FIRST GROUP OF SAID INPUT SIGNALS, AN ELECTRIC RESOLVER WHICH HAS A ROTOR COUPLED TO THE SHAFT TO ROTATE THEREWITH, AND WHICH IS RESPONSIVE TO SAID TWO SIGNALS TO SUPPLY TWO ELECTRIC SIGNALS THE AMPLITUDES OF WHICH ARE REPRESENTATIVE OF THE COMPONENTS OF SAID VECTOR ALONG RESPECTIVE AXES DEFINED IN THE ROTOR, AND MEANS FOR SUPPLYING TO THE MOTOR FOR CONTROLLING ROTATION OF THE SHAFT BY THE MOTOR AN ELECTRIC SIGNAL THAT IS DEPENDENT IN AMPLITUDE SELECTIVELY UPON ONE OR BOTH OF THE SIGNAL SUPPLIED BY THE RESOLVER IN DEPENDENCE UPON THE DIGITAL VALUES OF A SECOND GROUP OF SAID INPUT SIGNALS, THE ARRANGEMENT BEING SUCH THAT THE AMPLITUDE OF THE CONTROLLING SIGNAL IS DEPENDENT ON THE ONE BAND UPON THE ANGULAR POSITION OF THE SHAFT AND ON THE OTHER HAND UPON THE DIGITAL VALUES OF THE INPUT SIGNALS, AND THE MOTOR ROTATES THE SHAFT SO AS TO TEND TO REDUCE THE AMPLITUDE OF THE CONTROLLING SIGNAL TO ZERO AND THEREBY ANGULARLY POSITION THE SHAFT IN ACCORDANCE WITH THE DIGITAL VALUES.