Elmomc SimplIQ Digital Servo Drives-Bell Getting Started Instrukcja Użytkownika Pobierz pdf (Strona 86)

The SimplIQ for Steppers Getting Started & Tuning and Commissioning Guide

MAN-BELGS (Ver. 1.1)

Ls−

B−

⋅

Figure 78: Block diagram of the simplified DC motor model

The transfer function from voltage input,

, to motor shaft angle,

, is

()

;

sss

mem

=τ=τ

ττ+τ+

(8)

Usually,

is much smaller then

. The electrical time constant

is normally

in the order of magnitude of 1 msec, whereas in low friction systems

may be

in the order of 1 sec. If

ττ <<

, we can replace

sτ

in the denominator of (8)

()

s τ+τ

to get the approximation

()()

sss

ττ

(9)

Equation (9) is a common expression found in the literature and suits feedback

design where resonance effects can be neglected. We will now describe and

analyze motors with resonance.

B.3.2 Model with Flexible Transmission (resonance)

Figure 79 is a schematic representation of a ‘constant field’ motor with the load

connected to the motor shaft by a flexible axis.

Motor Load

Figure 79: Schematic connection of load via flexible coupling

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Elmomc SimplIQ Digital Servo Drives-Bell Getting Started Instrukcja Użytkownika Strona 86