User`s manual

Introduction to Local Logic Programming
GFK-1742A Chapter 10 Introduction to Local Logic Programming 10-45
10
CTL01 transition. The motion program will therefore make the motor shaft act like the second
hand on a quartz clock. Not an elegant application, but it does demonstrate several concepts.
Before we write the Motion Program, we will need to determine axis scaling. The first variable we
need to determine is the user units to counts ratio. The User Units to Counts ratio sets the number
of programming units for each position feedback count. This allows the user to program the
DSM314 in application-specific units. The User Units and Counts values must be within the range
of 1 to 65,535. The User Units to Counts ratio must be within the range of 8:1 to 1:32. For
example, if there is 1.000 inch of travel for 8192 feedback counts, a 1000:8192 User Units:Counts
ratio sets 1 User Unit equal to 0.001 inch.
To set the User Units to Counts ratio the first piece of information required is the number of counts
per revolution of the feedback device. In our example, we will be using a Beta 0.5 motor. The
Beta 0.5 has a feedback resolution of 8192 counts per revolution. We now perform the calculation
to determine the ratio. The basic equation we need to satisfy is:
RotationMotor Per CountsEncoder
1
Resolution Desired
RotationMotor Per Movement Load
Counts
User Units
⋅






=
For our example we have
8192
60
Counts
User Units
8192
1
60
1
1
Counts
User Units
=
⋅












=
This ratio is a problem since it violates the rule that the minimum User Units to Counts Ratio is
32
1
. The problem is easy to fix. We will change our programming units from 60
th
of a revolution
to a 600
th
of a revolution. This will make 1 programming unit equal to revolution
600
1
⋅
. We
repeat the above calculation.
8192
600
Counts
User Units
8192
1
600
1
1
Counts
User Units
=
⋅












=
Thus, to have our motor travel
60
1
of a revolution, we enter 10 units in our motion program.
Additional information on setting the User Units to Counts ratio is contained in Chapter 4.
The next item we need to determine is the motor top speed. This is a relatively simple calculation.