Galil Motion Control note 3312 Page 1
Application Note 3312: Smoothing Velocity Profiling
Moving a motor from one position to another involves accelerating the motor to a
certain speed, traveling at that speed for a time, and then decelerating to a stop at a
desired position. The DMC-1500 controller controls the motion of a motor, and for
simplicity uses a trapezoidal velocity profile. This means that as the velocity changes
from one value to another the acceleration and deceleration are linear.
A trapezoidal velocity profile is fine for most systems, but the sudden transition from
zero to full acceleration can cause an unacceptable jerk in some mechanical systems.
For these systems, the DMC-1500 has the ability to smooth the velocity profile into an S
shape. This S shaped smoothing of the motion profile is set with the IT command for
independent motion commands, such as PR and PA moves. Coordinated motion uses the
VT command to smooth the vector acceleration and deceleration.
Consider this simple motion program that commands a jog move on the X axis:
Let us assume that the motor is at rest, the program above is downloaded into the
program RAM of the DMC-1500 controller, and then the program is run by sending the
XQ command to the DMC-1500. The motor will begin to accelerate from rest to the
commanded jog speed of 100,000 counts per second. After that speed is reached, the
acceleration stops and then the motor will run then continuously at 100,000 counts per
second. If we graph the velocity of the motor versus time: