Specifications

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3401 Manual
Point I/O Stepper Module
Revision 2.0
Chapter 2: Calculating Move Profiles
Before starting a move operation, the 3401 module completely calculates each portion of the move
profile. That is, it calculates how many steps of the move profile will be required for acceleration and
how many steps will be required for deceleration. Depending on the data used to define the move profile,
this can result in two types of velocity profiles, either a Trapezoidal Profile or a Triangular Profile.
A Trapezoidal Profile jumps from rest to the Starting Speed, accelerates to the Programmed Velocity at
the commanded acceleration rate, continues at the Programmed Velocity to a predetermined point, and
then decelerates to the target position at the commanded deceleration rate to the starting speed and stops.
However, if the length of a commanded move is not long enough to attain the programmed velocity
before the deceleration point is reached, a Triangular Velocity profile will be generated.
Regardless of the type of Velocity Profile that is being run, the following equations can be used to
determine both the time to accelerate and the number of steps needed to accelerate. These formulas can
also be used to calculate the time and distance to decelerate.
Ta = (Vs – Vo)/a
Da = Ta * (Vo + Vs)/2
Vo = Starting Speed (steps/second)
Vs = Programmed Speed (steps/second)
Ta = Time to accelerate (seconds)
Da = Distance to accelerate (steps)
a = Acceleration rate (steps/second/second)
If using Triangular S Curve Acceleration, Ta = 2 * Ta calculated above
If using Trapezoidal S Curve Acceleration, Ta = (4/3) * Ta calculated above
The acceleration rate entered in these equations must have units of steps/second/second, not the
steps/ms/second used by the 3401 module. See the Calculation Notes below for a complete explanation.
Velocity
Starting
Speed
Time
Trapezoidal Profile
Velocity
Starting
Speed
Time
Triangular Profile
Velocity
Time
Vo
Vs