I²。+J²。=R²加工点M相对圆弧有三种情况
) d1 Y6 v& N( X1 w8 p. ?在圆弧外:Ii²+Ji²-R²>0
( p6 n$ N" H9 K' V在圆弧上:Ii²+Ji²-R²=0 图5.3
, M5 }$ x. v" ?+ X在圆弧内:Ii²+Ji²-R²<0
, o1 k/ S: I; I7 o+ H1 \% r: G程序框图 (数控指令G00/G01 X— Y—) + n/ d( a6 U6 H7 e- p
取Fi=Ii²+Ji²-R² (偏差判别函数)
) U3 Z% [6 g5 D/ r+ {规定I象限时内:+Y方向走一步
. O5 C, d" `9 J8 M0 w" M 外、上:-X方向 走一步
2 [* p1 } g0 `0 K( }7 }-X走一步后:Ii+1=Ii-1 ,Ji+1=Ji
7 B4 j5 J1 A: P c& \7 k/ DFi+1=Ii+1²+Ji+1²-R²=Fi-2Ii+1 ?0 u: A# b6 Z4 ~/ b/ R
+Y走一步后:Ii+1=Ii ,Ji+1=Ji+1
/ O: S) e! J7 t$ {, k Fi+1=Fi+2Ji+1 + N% b% \$ I: o' V( O, a
我们可推导第一象限的顺圆。, e9 C0 Q8 x0 H% }2 e" h% [
+X走一步后:Ii+1=Ii+1 ,Ji+1=Ji
/ A! q8 ~( A9 Z6 I/ Y9 _% _Fi+1=Fi+2Ii+1 (5-7) ?$ E6 e2 O% r3 y
-Y走一步后:Ii+1=Ii ,Ji+1=Ji-1 2 u6 X3 S0 A" ]2 ^$ Y7 u
Fi+1=Fi-2Ji+1 (5-8
" t4 J% P2 g! K# Z/ o- V3 H- U |