Rockwell Automation 1771-QB Linear Pos. - Manual (Page 27)

Positioning with the Linear Positioning
Module
Chapter 3
3Ć3
Figure 3.2
Trapezoidal Axis Movement
50002
Velocity
Time
Final
Velocity
Start 0 Finish
Constant
Velocity
Acceleration
Deceleration
The actuator may not reach the final velocity during a short move which may
only consist of acceleration and deceleration phases without a constant velocity
phase. This produces a ramp movement. (See Figure 3.3.)
Figure 3.3
Ramp Movement
50003
Velocity
Time
Peak
Velocity
Start 0 Finish
Acceleration
Deceleration
The module employs a technique called velocity curve smoothing to shape the
velocity curve into an “S curve”. To achieve this smoothing, acceleration and
deceleration rates are changed to provide more gradual application and removal
of force, thus reducing mechanical wear. The velocity smoothing constant that
you set in the parameter block determines how quickly acceleration and
deceleration change. The lower the value of the velocity smoothing constant,
the more slowly acceleration and deceleration change, producing a smoother
transition. Figure 3.4 shows the effect of velocity curve smoothing on the axis
movement.