Galil DMC-1700 Motor-Amplifier, Voltage Drive, PV = KV Kt SSTm + 1STe +, = Rj, = L R, where

Motor-Amplifier

The motor amplifier may be configured in three modes:

1.Voltage Drive

2.Current Drive

3.Velocity Loop

The operation and modeling in the three modes is as follows:

Voltage Drive

The amplifier is a voltage source with a gain of Kv [V/V]. The transfer function relating the input voltage, V, to the motor position, P, is

PV = KV [Kt S(STm + 1)(STe + 1)]

where		K 2
T	= RJ		[s]
m		t
and
Te	= L R		[s]

and the motor parameters and units are

Kt

R

J

L

Torque constant [Nm/A]

Armature Resistance Ω

Combined inertia of motor and load [kg.m2] Armature Inductance [H]

When the motor parameters are given in English units, it is necessary to convert the quantities to MKS units. For example, consider a motor with the parameters:

Kt = 14.16 oz - in/A = 0.1 Nm/A

R = 2 Ω

J = 0.0283 oz-in-s2= 2.10-4kg . m2

L = 0.004H

Then the corresponding time constants are

Tm = 0.04 sec

and

Te = 0.002 sec

Assuming that the amplifier gain is Kv = 4, the resulting transfer function is

P/V = 40/[s(0.04s+1)(0.002s+1)]

Current Drive

The current drive generates a current I, which is proportional to the input voltage, V, with a gain of Ka. The resulting transfer function in this case is

P/V = Ka Kt / Js2

where Kt and J are as defined previously. For example, a current amplifier with Ka = 2 A/V with the motor described by the previous example will have the transfer function:

DMC-1700/1800 Chapter 10 Theory of Operation • 189