Electricity: motive power systems – Positional servo systems – Program- or pattern-controlled systems
Patent
1988-08-11
1990-08-14
Shoop, Jr., William M.
Electricity: motive power systems
Positional servo systems
Program- or pattern-controlled systems
318567, 3185681, 364513, H02P 500
Patent
active
049490257
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a numerical control method capable of performing various controls at high speeds, with a desired positioning accuracy.
2. Description of the Related Art
In positioning control effected by a numerical control apparatus, a control object is controlled so that a deviation between a target position and an actual position falls within a predetermined range. In machining a workpiece, for instance, the numerical control apparatus reads, block by block, an NC program in which machining conditions such as a tool locus are stated, and executes respective blocks of the program in sequence. In the case of the thus read block containing a moving command, the numerical control apparatus determines completion of positioning control for a block when the absolute of a stored value of an error register, housed in a servo circuit which forms part of a tool driving system, reaches a value below a preset in-position value during the execution of the same block. The numerical control apparatus then starts the execution of the next block, the stored value representing a deviation or error between a target moving amount of a tool, specified by the moving command, and an actual moving amount of the tool detected by a position detector.
In a positioning control of this kind, the positioning accuracy is improved but a period of time required for positioning is lengthened as the in-position value is set to a smaller one.
According to the conventional method, the in-position value is fixedly set, and hence it is difficult to simultaneously obtain an improved positioning accuracy and a shortened execution time period for desired positioning.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a numerical control method which is capable of executing various controls at high speeds, with a desired positioning accuracy maintained, by variably setting the positioning accuracy.
In order to achieve the above-mentioned object, a numerical control method according to the present invention comprises the steps of (a) presetting values of a parameter, each of the parameter values representing positioning accuracy for an associated one combination of kinds of moving commands, and (b) reading and executing a numerical control program block by block. The step (b) includes the steps of (b1) determining a combination of kinds of moving commands which are respectively stated in a plurality of blocks including a block to be executed at present time, (b2) selecting a corresponding one of the parameter values set by the step (a) in accordance with the result of the determination of the step (b1), and starting execution of the present block, and (b3) starting execution of the next block when it is determined, on the basis of the parameter value selected in the step (b2), that positioning associated with the moving command for the present block is completed.
As mentioned above, according to the present invention, since the positioning accuracy is variably set during the execution of control in accordance with a combination of moving commands which are sequentially read from an NC program, it is possible to carry out various controls at high speeds with desired accuracy.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram showing a numerical control apparatus and peripheral elements for embodying a numerical control method according to an embodiment of the present invention;
FIG. 2 is a flowchart of a preparatory process for execution of positioning control effected by the apparatus of FIG. 1; and
FIG. 3 is a flowchart showing a process for execution of the positioning control.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In FIG. 1, a numerical control apparatus (hereinafter referred to as NC apparatus) 1 is connected through buses 16 to a central processing unit (hereinafter referred to as CPU) 10, a ROM 11 storing a management program for generally controlling the NC apparatus 1, for instance, a RAM 12 for temporal storage of data, a n
REFERENCES:
patent: 4475160 (1984-10-01), Inaba
patent: 4785221 (1988-11-01), Neko
Iwagaya Takashi
Nakazato Tomomi
Fanuc Ltd.
Ip Paul
Shoop Jr. William M.
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