Zoh; System Analysis - Galil Motion Control CDS-3310 User Manual

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 NB and the real part
of the zeros is set by NZ.
The most simple procedure for setting the notch filter, identify the resonance frequency and set NF to
the same value. Set NB to about one half of NF and set NZ to a low value between zero and 5.

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
If the sampling period is T = 0.001, for example, H(s) becomes:
However, in most applications, H(s) may be approximated as one.
This completes the modeling of the system elements. Next, we discuss the system analysis.

System Analysis

To analyze the system, we 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 CDS-3310 controller and the following parameters:
K t = 0.1
J = 2.10 -4
R = 2
K a = 4
KP = 12.5
KD = 245
KI = 0
N = 500
T = 1
The transfer function of the system elements are:
Motor
Amp
DAC
Encoder
ZOH
72 • Chapter 10 Theory of Operation
H(s) = 1/(1+sT/2)
H(s) = 2000/(s+2000)
Nm/A
kg.m 2
Ω
Amp/Volt
Counts/rev
ms
M(s) = P/I = Kt/Js2 = 500/s 2 [rad/A]
K a = 4 [Amp/V]
K d = 0.0003 [V/count]
K f = 4N/2π = 318 [count/rad]
2000/(s+2000)
Torque constant
System moment of inertia
Motor resistance
Current amplifier gain
Digital filter gain
Digital filter zero
No integrator
Encoder line density
Sample period
CDS-3310