Electricity: motive power systems – Positional servo systems – Program- or pattern-controlled systems
Patent
1984-07-18
1986-04-22
Dobeck, B.
Electricity: motive power systems
Positional servo systems
Program- or pattern-controlled systems
318573, 364474, G05B 1924
Patent
active
045845093
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Technical Field
This invention relates to a method of discriminating the present position region of a machine.
2. Description of the Related Art
Conventionally a numerically controlled (hereafter referred to as "NC") machine tool has a dog provided on a movable portion of the machine tool and a limit switch provided at a prescribed position on a stationary portion of the machine tool. When the dog trips the limit switch, a signal is generated that the movable portion of the machine has reached the prescribed position, whereupon a predetermined operation is executed. By way of example, in an operation for returning a movable portion such as a table to a reference point, the dog trips a deceleration limit switch in the vicinity of the reference point, whereupon an NC unit controlling the machine tool takes this as an indication that the table has reached the vicinity of the reference point and responds by providing a command for reducing the travelling velocity. Further, in a tool change operation, a tool rest is moved toward a tool change position. At the tool change position, a dog provided on the tool rest trips the limit switch, whereby the machine tool halts the tool rest at a stopping position and thereafter performs the tool change.
Thus, in the prior art, a dog and a limit switch are provided at appropriate locations and, when a prescribed limit switch is actuated, a predetermined operation is performed by the NC apparatus or the machine tool. This means that a dog and limit switch are essential, thereby increasing the number of component parts. Another disadvantage is that mounting and adjusting the dog and limit switch are troublesome operations.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a novel method of discriminating the present position region of a machine, whereby a region at which a movable position resides can be discriminated without mounting a dog or limit switch.
A machine present position control region discrimination method according to the present invention, utilized by a numerical control system which performs numerical control of a movable portion of a machine tool, comprises the following steps: dividing a stroke along a controlled coordinate axis into n equal parts to partition the stroke into n regions, each having an interval length; assigning a region number to each region incrementing or decrementing a present position region number in dependence upon a travelling directon when an accumulated travelling distance of the movable portion of the machine exceeds a range bounded by zero and the interval length and delivering a present position region signal, which is indicative of the present position region number, from the NC control system to the machine.
According to the present invention, it is not necessary to provide a dog or limit switch as in the prior art, thereby providing an advantage in terms of cost. Moreover, complicated tasks such as mounting and positional adjustments are no longer required.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an illustrative view depicting movement regions;
FIG. 2 is a block diagram of an NC apparatus capable of utilizing a method according to the present invention; and
FIG. 3 is a flowchart of a method according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
An embodiment of the present invention will now be described in detail with reference to the drawings.
FIG. 1 is an illustrative view of the range of movement of a machine tool having a full stroke of 1270 mm along a certain coordinate axis, e.g., the X axis the stroke being equally divided into 127 movement regions. The stroke in the negative direction from a reference point Pr is 50 mm, and the stroke in the positive direction in 1220 mm. Regions are defined with an interval length of 10 mm intervals. The region in the -50.about.-40 mm interval is defined as a first region, that in the -40.about.-30 mm interval a second region, and so on through the region in the 1210.about.1220 mm interval, wh
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patent: 4164693 (1979-08-01), Leenhouts
patent: 4507738 (1985-03-01), Nozawa et al.
Dobeck B.
Fanuc Ltd.
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