Siemens SIMATIC FM 453 Manual page 156

Starting up the FM 453
7.3.2 Evaluating the Characteristics of the Stepper Motor
Overview
Basically, the stepper motor is a highly dynamic drive motor which is capa-
ble of following setpoint assignments more or less free of following error. It
is also capable of handling the transition between idle time and movement
(and back) by way of the start/stop frequency at a high rate of acceleration.
This presupposes however, that the available motor torque at any given
movement status, matches as a minimum, the torque necessary for executing
the movement. In the following discussion, it is assumed that you are familiar
with the necessary torque values for your particular application from the hav-
ing conducted configuration of the drive. If necessary, refer to the formula or
tabular material (e.g. Positec/Berger Lahr: [title translated: "Formulas +
Computations for optimal stepper motor adjustment" [TN: available in Eng-
lish? If so, what is exact English title?] provided by the step drive manufac-
turers.
You can obtain optimal configuration of the speed profile for traversing
movement when the speed-timing diagram, as shown in Figure 9-8, is well-
defined.
You can determine the parameters for the speed profile, as shown in the fol-
lowing parameterization example, from the operating characteristic curves of
the stepper motor you have in use. Always be sure to allow a torque reserve
of approx. 20%.
Procedure Determining the available or necessary torque:
Determining the present moments of inertia:
Assumed values from the parametering example:
Evaluation for open-loop controlled operation (MD61 = 7):
Proceed in accordance with the following instructions!
Evaluation for closed-loop controlled operation (MD61 = 1):
Proceed in accordance with the following instructions and
7-14
M = M + M
Motor Load Accelerations
J = J + J
Load external_rotational external_translational
J = J + J
total Motor Load
M = 5 Nm
Motor
2
J = 4 kg cm
Motor
f = 10 kHz
max
Deceleration values are as acceleration values
In the evaluation algorithm (Figure 7-6), select the path "Parameterization
of the velocity profile via simple ramp"
Convert the accelerations computed for MD57 and MD59 as follows to
MD40, MD41 and MD45:
Always MD40 = MD57 (MD11 + MD12 2
When MD59 = 0 MD41 = MD40
When MD59 0 MD41 = MD59 (MD11 + MD12 2
When MD40 MD41 MD45 = MD57
When MD40 > MD41 MD45 = MD59
M = 0.6 Nm (non-speed-dependent)
Load
2
J = 3 kg cm
Load
MD13 = 500 increments per revolution
-32
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FM 453 Servo Drive / Step Drive Positioning Module
C79000-G7076-C453-01
)/(1000 MD52)
)/(1000 MD52)