Galil DMC-2X00 Position Control by Joystick, Backlash Compensation by Sampled Dual-Loop

Speed = 20000 x vin

The corresponding velocity for the motor is assigned to the VEL variable.

Instruction

#A

JG0

BGA #B vin=@AN[1] vel=vin*20000 JG vel

JP #B

EN

Position Control by Joystick

This system requires the position of the motor to be proportional to the joystick angle. Furthermore, the ratio between the two positions must be programmable. For example, if the control ratio is 5:1, it implies that when the joystick voltage is 5 volts, corresponding to 1024 counts, the required motor position must be 5120 counts. The variable V3 changes the position ratio.

Instruction	Interpretation
#A	Label
v3=1024	Initial position ratio
DP0	Define the starting position
JG0	Set motor in jog mode as zero
BGA	Start
#B
v1=@AN[1]	Read analog input
v2=v1*v3	Compute the desired position
v4=v2-_TPA-_TEA	Find the following error
v5=v4*20	Compute a proportional speed
JG v5	Change the speed
JP #B	Repeat the process
EN	End

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 lead screw. Such a lead screw has a backlash of 4 micron, and the required position accuracy is for 0.5 micron.

DMC-2X00 Chapter 7 Application Programming y 123