上海维宏电子科技股份有限公司
Weihong Electronic Technology Co., Ltd.
- 60 - Specialized, Concentrated, Focused
1 Ideal move (without pitch error)
S (Nominal value)
2
Actual move (with pitch error)
L (Actual value)
Fig. 3-34 Picture of moving curve
Compensation Method
In pitch compensation, generally pitch error value isn‘t related to feed direction. That is, when pitch
is too small in positive feed, additional feed pulse is needed, and when negative feed passes the same
position, the same amount of feed pulse should be added. But if the pitch is large, deduction of feed
pulse is needed, and neither is the reducing amount related to feed direction. In software compensation,
correction of each point on error curve should be tabulated and saved to system memory. Then auto
compensation for coordinate of each point is available in running, improving machine precision.
Backlash Compensation
Hysteresis feature is caused by forward and reverse clearance. Assumed that CW rotation of driving
shaft is negative motion, leading the driven shaft to counter motion, servo motor will be idling without
moving worktable because of mechanical driving chain backlash when the driving shaft suddenly begins
CCW rotation (positive motion). After staying at a certain position for some time, worktable will move
along the negative direction with the driving shaft; when the direction of the driving shaft changes again,
the situation is the same, which is called Hysteresis. If there were no pitch error under ideal condition,
the moving curve of worktable is shown in Fig. 3-35, and the curve of horizontal area is during the idling
of servo motor without worktable movement. The actual moving curve of worktable is shown in Fig. 3-36.
L (Actual value)
S (Nominal value)
Fig. 3-35 Hysteresis feature
L (Actual value)
S (Nominal value)
Fig. 3-36 Actual moving curve
