Method of sensing position of movable body and apparatus therefor

An apparatus for sensing a position of a movable body for use in a machine tool comprising:

• a slide base fixedly provided;
• a slide table movable on said slide table in the forward and backward directions;
• a DC motor for moving the slide table forward or backward by rotating a feed shaft threadably coupled to a feed nut solidly secured to the slide table;
• a DC motor driving circuit for controlling the rotational direction and rotational speed of said DC motor;
• a speed change setting circuit for supplying a proper approach speed setting value in accordance with the forwarded position of the slide table to the DC motor driving circuit;
• a mechanical sequence circuit for controlling the DC motor driving circuit;
• a dead stopper solidly secured to the inner wall surface of said slide base;
• a rotary encoder for detecting a rotation of the feed shaft corresponding to a movement of the slide table;
• and
• a limit detecting circuit for sensing an approach position of the slide table in accordance with an output from the rotary encoder and supplying a signal of the approach position to a mechanical sequence circuit.

A method of sensing a position of a movable body comprising the steps of:

• defining a reference position at which said movable body abuts against a stopper which stops said movable body even if said movable body continues to be driven;
• generating digital pulse signals related to incremental movements of said movable body, said digital pulse signals not being produced when said movable body abuts against said stop;
• counting said digital pulse signals to produce an indication of the position of said movable body;
• resetting said count when said movable body abuts against said stopper irrespective of the actual value of said count;
• and
• sensing the coincidence of said count with a predetermined pulse number corresponding to a predetermined position so as to sense the fact that said movable body has reached said predetermined position.

An apparatus for sensing a position of a movable body on a base, comprising:

• a motor for moving said movable body;
• a stopper for receiving and stopping said movable body at a reference position;
• pulse generating means for generating pulse signals in proportion to a distance of movement of said movable body;
• counting means for counting said pulse signals;
• reference position detecting means for detecting that said pulse signals cease from being generated for a predetermined period of time due to stopping of said movable body by said stopper and resetting said counting means in response thereto;
• predetermined position presetting means for presetting a number of said pulse signals corresponding to a predetermined position of said movable body;
• and
• comparing means for detecting that said movable body reaches said predetermined position when a value of said counting means coincides with said number preset by said predetermined position presetting means.

An apparatus for sensing a position of a movable body on a base, comprising:

• a motor for moving said movable body;
• pulse generating means for generating pulse signals in proportion to a distance of movement of said movable body;
• counting means for counting said pulse signals;
• predetermined positions presetting means for presetting a plurality of numbers of said pulse signals corresponding to a plurality of predetermined positions of said movable body;
• predetermined ranges presetting means for presetting a plurality of numbers of said pulse signals corresponding to predetermined ranges from said predetermined positions preset by said predetermined positions presetting means;
• and
• comparing means for detecting that said movable body reaches each of said predetermined positions of said predetermined position presetting means when values of said counting means coincide with said numbers preset by said predetermined position presetting means and for detecting that said movable body is in said ranges preset by said predetermined ranges presetting means until values of said counting means coincide with said numbers preset by said predetermined ranges presetting means.