Position control including first digital motor control to set position and second control to followup

Claim 1

A POSITION CONTROL ARRANGEMENT COMPRISING A MOVABLE MEMBER WHICH IS TO BE POSITIONED RELATIVE TO AN ARBITRARY ZERO POSITION, MEANS TO SUPPLY A FIRST GROUP OF ELECTRIC SIGNALS WHICH REPRESENT INPUT DATA IN THE FORM OF A FIRST MULTI-DIGIT NUMBER CHARACTERISTIC OF THE DESIRED POSITION OF SAID MOVABLE MEMBER, MEANS TO SUPPLU A SECOND GROUP OF ELECTRIC SIGNALS WHICH REPRESENT INFORMATION IN THE FORM OF A SECOND MULTI-DIGIT NUMBER CHARACTERISTIC OF THE ACTUAL POSITION OF SAID MOVABLE MEMBER, MEANS RESPONSIVE TO THE FIRST AND SECOND GROUPS OF SIGNALS TO COMPARE SAID FIRST AND SECOND NUMBERS, MEANS TO MOVE SAID MEMBER IN DEPENDENCE UPON THE COMPARISON OF SAID NUMBERS TO REDUCE THE DIFFERENCE BETWEEN SAID NUMBERS TO A PREDETERMINED VALUE DURING A POSITIONING OPERATION, ZERO-CHANGING MEANS TO CHANGE ONE OF SAID GROUPS OF SIGNALS WHEREBY SAID ZERO POSITION MAY BE MOVED PRIOR TO A POSITIONING OPERATION, AND MEANS AUTOMATICALLY TO OPERATE SAID ZERO-CHANGING MEANS DURING A ZERO SETTING OPERATION IN DEPENDENCE UPON THE COMPARISON EFFECTED BY SAID MEANS RESPONSIVE TO THE FIRST AND SECOND GROUPS OF SIGNALS SO THAT, SUBSEQUENT TO SUCH OPERATION OF THE ZERO-CHANGING MEANS, THE ZERO POSITION IS DETERMINED BY THE INPUT DATA AND THE POSITION OF THE MOVABLE MEMBER DURING THE ZERO SETTING OPERATION.