Method and apparatus for normalizing servo-positioning signals

Claim 1

In a method of positioning wherein actual position is monitored in relation to desired position and electrical signals representative of differences between such actual and desired positions are used as a basis for making position corrections, the improved method of producing normalized positioning signals from first and second analog electrical signals which are representative of an actual position in relation to a desired position, said improved method comprising the steps of: using an analog-to-digital converter to convert each of said first and second analog electrical signals to first and second digital electrical signals whose values are modified and normalized representations of said actual position in relation to said desired position; said converter being so used by summing said first and second analog signals and applying a representation of their summation to a reference input of said converter while also applying said analog signals individually to said converter as conversion signal inputs for conversion to digital form; and operating said converter to make the digital conversion of said individual conversion input signals as a function of the applied reference input comprising said summation of signals, such that the converter outputs a first digital signal representative of the quotient of the value of the first said analog signal value and the sum of the first and second said analog signal values and a second digital signal representative of the quotient of the second said analog signal value and the sum of the first and second analog signal values; and digitally processing said first and second digital signals by subtracting one from the other thereof to thereby produce a resultant digital electrical signal representative of the quotient whose numerator comprises the difference between the first representative-value digital signal and the second such digital signal, and whose denominator comprises the sum of the same two digital signals; said method of positioning further comprising the steps of using said resultant digital signal as the basis for making positioning corrections by moving from said actual position toward the desired position as a function of the value of said resultant signal.