Positioning systems including reliable track crossing detection for high speed relative motions

In a machine-effected method of relatively moving first and second members, one of the members having closely spaced-apart, position-indicating, machine-sensible indicia and another of said members having means for sensing said indicia and producing indicia signals, motive means coupled to said members for relatively moving same;

• the improvement including the machine-executed steps of:
• during said relative movement, analyzing the indicia signals for electrically indicating the relative speed of movement as a sensed relative speed;
• slaving a timed circuit to said indicia signals for generating timed signals;
• establishing a reference speed indication;
• comparing said sensed relative speed with a reference speed indication and indicating a first portion of said relative movement when the sensed relative speed is less than said reference speed and indicating a second portion of said relative movement when the indicated relative speed is greater than said indicated reference speed;
• and
• supplying said indicia signals to said motive means only during said first portion and said timed signals to said motive means only during said second portion for actuating said motive means to control relative motion of said members during said relative movement.

In a positioning system having first and second relatively moveable members, said first member being a record member having elongated tracks respectively identified by a plurality of substantially-parallel spaced-apart grooves in the record member, an optical transducer on the second member in optical communication with the record member and its grooves, said members being mounted on a frame for first and second relative movements in first and second directions respectively along and transverse to said tracks, tracking circuit means operatively coupled to the transducer for receiving an indicia signal indicative of the current relative position of the transducer to one of said grooves along said second direction, motive means coupled to said members for relatively moving same along said second direction for moving said transducer from one record track on the record member to a second record track in the record member displaced from the one record track along said second direction;

• the improvement including, in combination:
• a timed electrical circuit electrically connected to said transducer means for receiving said indicia signals and being slaved to said indicia signals for generating timed signals;
• selection means for indicating first and second predetermined portions of said relative movements in said second direction;
• coupling means connected to said motive means, said timed electrical circuit, said transducer and said selection means for responding to said indications of the first and second portions to respectively supply said indicia signals and said timed signals to said motive means only during said respective first and second portions.