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In order to ensure the smooth processing of endformation,
it is necessary to make the surface of the
surface roughness values of less than or equal to a set
value, which must ensure that the workpiece with the
wheel contact point at the speed of a constant speed. As
the grinding face, we should constantly be feeding action
so that grinding diameter gradually reduced. Therefore,
the NC device control software must be designed to
complete the corresponding spindle speed adjustment.
II. SOFTWARE DESIGN
Software architecture with front and back structural
model.Foreground program is an interrupt service routine,
it is almost assumed, the entire real-time functions
(interpolation, position control, etc.), while the scheduling
management, and human-computer interaction in the
background process to complete[6]. Background process
is a loop run the program, in its operation process, the
prospects continue to insert real-time interrupt program
worked together to accomplish the task CNC machining.
Their operational tasks, including system management
and system control two parts. System Management
include communications, display, syntax checking,
parameter setting, fault diagnosis, procedures, coding and
other tasks, such procedures are less demanding real-time;
system control is mainly motion control, including, tool
compensation, speed control, trajectory interpolation ,
position control, limit and emergency stop and other tasks,
such procedures are completed very strong real-time
control tasks. The overall structure of the software system
as shown in Figure 7.
position. Therefore, in order to achieve the process in
motion trajectory control must be calculated in real-time
linear and the feed rate to meet the requirements of a
number of intermediate points (between the start and end).
This is the CNC interpolation techniques (Inierpolation)
concept. Accordingly, interpolation is defined as follows:
The so-called interpolation is based on a given feed rate
and a given linear outline the requirements of the outline
between the known points to determine the number of
mid-point method, this method is called interpolation fill
methods or interpolation theory. For each method
(principles) can be used on a different calculation method
to achieve such a specific method of calculation is called
interpolation algorithm.
Interpolation algorithm can be divided into pulse
incremental interpolation algorithms and data sampling
interpolation algorithm for two. Pulse incremental method
is generally used with stepper motor-driven devices, the
open-loop numerical control system, it is common pulse
incremental method with point by point comparison
method and the digital integration method. Data sampling
method has been applied relatively high speed and
accuracy requirements of NC system, the common data
sampling time-division method to expand DDA method
and so on[8].
The system uses digital integration method of circular
interpolation algorithm interpolation method.
digital integration method for the basic principles
From the geometric point of view, is to find the
function of integral operator Y = f (t) curve and the
horizontal axis of the enclosed area. As shown in Figure 8.
Figure7. BEFORE AND AFTER THE TAIWAN-BASED SYSTEM
SOFTWARE ARCHITECTURE
III. INTERPOLATION ALGORITHM
Parts of the contour shape is from a variety of shapes
(such as linear, circular, spiral lines, parabola, the free
curve, etc.) of different circles. Foremost among these is
a straight line and arc. Users in parts processing, in
general, provides only necessary to describe the linear
parameters, such as a straight line, to provide its starting
point and end point; pairs of arcs, and to provide a starting
point and end point, clockwise or counter-clockwise
circular arc and the center of a circle relative at the start
Figure8. GEOMETRIC DESCRIPTION OF THE FUNCTION POINTS
We can see from Figure 8, from the time t0 to tn the
function Y = f (t) the integral value is expressed as:
t
S = ∫ Ydt =
t0
∫
n t n
t
0
f ( t)
dt
In geometry is to use a series of small rectangular area,
and to approximate that of the function f (t) the following
integral area. 5 for further processing of the formula, take
Δ t as the basic unit of one, then the formula is converted
to digital integrator formula:
(5)
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