System Analysis - Galil Motion Control DMC-21 5 Series User Manual

K = 160
A = 0.9
C = 2
a = 250 rad/s
and the equivalent continuous filter, G(s), is
G(s) = [16 + 0.144s + 2000/s] · 250/ (s+250)
The notch filter has two complex zeros, z and
The effect of the notch filter is to cancel the resonance affect by placing the complex zeros on top of the resonance
poles. The notch poles, P and p, are programmable and are selected to have sufficient damping. It is best to select
the notch parameters by the frequency terms. The poles and zeros have a frequency in Hz, selected by the
command NF. The real part of the poles is set by
The most simple procedure for setting the notch filter, identify the resonance frequency and set
value. Set to about one half of
NB
ZOH
The ZOH, or zero-order-hold, represents the effect of the sampling process, where the motor command is updated
once per sampling period. The effect of the ZOH can be modeled by the transfer function
H(s) = 1/(1+sT/2)
If the sampling period is T = 0.001, for example, H(s) becomes:
H(s) = 2000/(s+2000)
However, in most applications, H(s) may be approximated as one.

System Analysis

To analyze the system, start with a block diagram model of the system elements. The analysis procedure is
illustrated in terms of the following example.
Consider a position control system with the DMC-21x5 controller and the following parameters:
K = 0.1
t
J = 2 * 10
R = 2
K = 4
a
KP = 12.5
KD = 245
KI = 0
N = 500
T = 1
The transfer function of the system elements are:
Motor
M(s) = P/I = K
Amp
K = 4 [Amp/V]
a
DAC
K = 0.0003 [V/count]
d
Chapter 10 Theory of Operation ▫ 130
z
and set
NF NZ
Nm/A
-4 2
kg.m
Ω
Amp/Volt
Counts/rev
ms
2 2
/Js = 500/s [rad/A]
t
, and two complex poles, p and p .
and the real part of the zeros is set by NZ.
NB
to a low value between zero and 5.
to the same
NF
Torque constant
System moment of inertia
Motor resistance
Current amplifier gain
Digital filter gain
Digital filter zero
No integrator
Encoder line density
Sample period
DMC-21x5 User Manual 1.0a1