Self-balancing servo system with super-imposed alternating current for reducing static friction

Claim 1

AN ELECTRICAL CONTROL AND RECORDING SYSTEM COMPRISING A COMPARISON CIRCUIT, MEANS FOR FEEDING A FIRST VOLTAGETO BE RECORDED AND A SECOND VOLTAGE CORRESPONDING TO A RECORDED VALUE IN SERIES OPPOSITION TO THE COMPARISON CIRCUIT, ANY DIFFERENCE BETWEEN SID TWO VOLTAGES APPEARING IN SAID COMPARISON CIRCUIT AS AN ERROR VOLTAGE, MEANS FOR INTRODUCING AN ALTERNATING VOLTAGE INTO SAID COMPARISON CIRCUIT IN SERIES WITH SAID ERROR VOLTAGE, AN ELECTRICALLY OPERATED INTERRUPTER DEVICE CONNECTED IN SAID COMPARISON CIRCUIT AND ACTUATED IN DEPENDENCE UPON THE SUM OF SAID ALTERNATING VOLTAGE AND SAID ERROR VOLTAGE, A CONTROL MOTOR FOR REDUCING TO ZERO ANY ERROR VOLTAGE AND HAVING TWO SEPARATE EXCITATION WINDINGS, A POWER SUPPLY FOR SAID EXCITATION WINDINGS, A RELAY WHOSE ENERGIZATION IS CONTROLLED BY THE INTERRUPTER DEVICE, A FIRST CHANGEOVER SWITCH HAVING A MOVABLE CONTACT AND TWO FIXED CONTACTS, SAID TWO FIXED CONTACTS BEING CONNECTED RESPECTIVELY TO ONE END OF EACH OF THE TWO EXCITATION WINDINGS, MEAND FOR CONTROLLING THE MOVABLE CONTACT OF SAID CHANGEOVER SWITCH BY THE ENERGISATION OF SAID RELAY, A SECOND CHANGEOVER SWITCH HAVING A MOVABLE CONTACT AND TWO FIXED CONTACTS, SAID TWO FIXED CONTACTS BEING CONNECTED RESPECTIVELY TO THE OTHER END OF EACH OF SAID EXCITATION WINDINGS, A CAM DEVICE FOR CONTROLLING THE MOVABLE CONTACT OF SAID SECOND CHANGEOVER SWITCH, A MOTOR OPERATING IN SYNCHRONISM WITH THE ALTERNATING VOLTAGE AND DRIVING SAME CAM DEVICE TO OPERATE SAID SECOND CHANGEOVER SWITCH SO AS TO CLOSE THE FIXED CONTACTS OF SAID SECOND CHANGEOVER SWTICH ALTERNATING IN ACCORDANCE WITH EACH HALF PERIOD OF THE ALTERNATING VOLTAGE; SO THAT IN THE ABSENCE OF AN ERROR VOLTAGE THE FIRST AND SECOND CHANGEOVER SWITCHES ARE OPERATED DURING ANY ONE PERIOD OF SAID ALTERNATING VOLTAGE IN OPPOSITE DIRECTIONS SO AS TO PREVENT THE ENERGIZATION OF EITHER OF THE TWO EXCITATION WINDINGS OF THE CONTROL MOTOR, AND SO THAT WHEN AN ERROR VOLTAGE IS PRESENT SAID FIRST AND SECOND CHANGEOVER SWITCHES OPERATE TO ALLOW THE ENERGIZATION OF EITHER OF SAID EXCITATION WINDINGS ONLY WHEN SAID CONTROL MOTOR WILL OPERATE TO EFFECT A REDUCTION OF SAID ERROR VOLTAGE.