Backlash Compensation By Sampled Dual-Loop - Galil Motion Control CDS-3310 User Manual

START PULSE I1
MOTOR VELOCITY
OUTPUT PULSE
TIME INTERVALS
Figure 7.1 - Motor Velocity and the Associated Input/Output signals

Backlash Compensation by Sampled Dual-Loop

The continuous dual loop, enabled by the DV1 function is an effective way to compensate for
backlash. In some cases, however, when the backlash magnitude is large, it may be difficult to
stabilize the system. In those cases, it may be easier to use the sampled dual loop method described
below.
This design example addresses the basic problems of backlash in motion control systems. The
objective is to control the position of a linear slide precisely. The slide is to be controlled by a rotary
motor, which is coupled to the slide by a leadscrew. Such a leadscrew has a backlash of 4 micron, and
the required position accuracy is for 0.5 micron.
56 • Chapter 7 Application Programming
Instruction Interpretation
#A Label
AI1 Wait for input 1
PR 6370 Distance
SP 3185 Speed
BGA Start Motion
AMA After motion is complete
SB1 Set output bit 1
WT 20 Wait 20 ms
CB1 Clear output bit 1
WT 80 Wait 80 ms
JP #A Repeat the process
move
output
wait ready move
CDS-3310