Galil DMC-4040, User Manual

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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
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.
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 DMC-40x0 controller and the following parameters:
Kt = 0.1 Nm/A Torque constant
J = 2.10-4 kg.m2 System moment of inertia
R = 2
Ω
Motor resistance
Ka = 4 Amp/Volt Current amplifier gain
KP = 12.5 Digital filter gain
KD = 245 Digital filter zero
KI = 0 No integrator
N = 500 Counts/rev Encoder line density
T = 1 ms Sample period
The transfer function of the system elements are:
Motor
M(s) = P/I = Kt/Js2 = 500/s2 [rad/A]
Amp
Ka = 4 [Amp/V]
DAC
Kd = 0.0003 [V/count]
Encoder
Kf = 4N/2
π
= 318 [count/rad]
ZOH
2000/(s+2000)
Digital Filter
KP = 12.5, KD = 245, T = 0.001
Therefore,
D(z) = 1030 (z-0.95)/Z
Chapter 10 Theory of Operation
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191 DMC-40x0 User Manual