Measuring apparatus for driving a synchronous motor in response to the movement of acyclic wave pattern

Claim 1

MEASURING APPARATUS FOR DETERMINING THE EXTENT AND SENSE OF THE RELATIVE MOVEMENT OF A FIRST OBJECT IN ONE OR OTHER OF TWO OPPOSITE DIRECTIONS WITH RESPECT TO A SECOND OBJECT INCLUDING MEANS FOR SETTING UP A CYCLIC WAVE PATTERN HAVING A SPATIAL WAVELENGTH BETWEEN MAXIMUM INTENSITIES ADAPTED TO MOVE WITH RESPECT TO THE SECOND OBJECT IN DEPENDENCE ON THE SAID RELATIVE MOVEMENT OF THE FIRST OBJECT AND WHEREIN THE CONDITIONS OF THE PATTERN AT THREE POSITIONS ALONG SAID WAVELENGTH FIXED WITH RESPECT TO SAID SECOND OBJECT ARE 120 DEGREES OUT OF PHASE WITH ONE ANOTHER, THREE DETECTING MEANS OPERATIVE TO PRODUCE ELECTRICAL OUTPUT SIGNALS RESPONSIVE TO AND INDICATIVE OF THE CONDITIONS OF THE PATTERN, ONE DETECTING MEANS BEING POSITIONED AT EACH OF SAID THREE POSITIONS, A STABILISING MEANS FOR STABILISING THE ELECTRICAL OUTPUT SIGNALS FROM SAID DETECTING DEVICES AGAINST IN-PHASE CHANGES OF THOSE SIGNALS, A THREE-PHASE SUNCHRONOUS MOTOR HAVING A PERMANENT MAGNET ROTOR AND A PLURALITY OF STATOR WINDINGS AND BEING OF THE TYPE IN WHICH THE ANGULAR POSITION OF THE ROTOR IS DETERMINED BY THE RELATIVE CONDITIONS OF ENERGISATION OF SAID STATOR WINDINGS AND CAPABLE OF WORKING DOWN TO ZERO FREQUENCY, MEANS FOR ENERGISING SAID THREE STATOR WINDINGS FROM THE ELECTRICAL OUTPUT SIGNALS OF THE THREE DETECTING MEANS RESPECTIVELY BY WAY OF THE STABILISING MEANS SUCH THAT THE ANGULAR POSITION OF THE ROTOR REPRESENTS BY THE EXTENT AND DIRECTION OF ITS DISPLACEMENT FROM A DATUM ANGULAR POSITION THE EXTENT AND DIRECTION OF THE SAID RELATIVE MOVEMENT OF THE FIRST OBJECT, AND INDICATOR MEANS COUPLED TO THE ROTOR FOR INDICATING SUCH MOVEMENT.