User manual

Chapter 1 Introduction
6 ADVANCED MICRO CONTROLS INC.
Overview (continued)
The module has Setup Parameters that allow you to scale and adjust the position and
tachometer data. Additional parameters allow you to define the type of attached transducer and
the digital format of the position data. To maintain compatibility with past versions of the
module, some of these parameters can be set with jumpers. Most of the parameters can be
programmed over the backplane using block transfers. Using single transfers, a limited number
of parameters can be programmed over the backplane.
Since revision H of the PC board, the1761H module directly supports Autotech transducers.
The module does this by automatically adjusting the reference voltage to the Autotech level
when the Resolver Type parameter is changed from the backplane.
Brushless Resolver Description
The brushless resolver is unsurpassed by any other type of rotary position transducer in its
ability to withstand the harsh industrial environment. An analog sensor that is absolute over a
single turn, the resolver was originally developed for military applications and has benefited
from more than 50 years of continuous use and development.
The resolver is essentially a rotary transformer with one important distinction. The energy
coupled through a rotary transformer is not affected by shaft position whereas the magnitude of
energy coupled through a resolver varies sinusoidally as the shaft rotates. A resolver has one
primary winding, the Reference Winding, and two secondary windings, the SIN and COS
Windings (See figure 1.2, Resolver Cut Away View). The Reference Winding is located in the
rotor of the resolver, the SIN and COS Windings in the stator. The SIN and COS Windings are
mechanically displaced 90 degrees from each other. In a brushless resolver, energy is supplied
from the Reference Winding to the rotor by a rotary transformer. This eliminates brushes and
slip rings in the resolver and the reliability problems associated with them.
In general, the Reference Winding is excited by an AC voltage called the Reference Voltage
(V
R
). (See figure 1.3, Resolver Schematic). The induced voltages in the SIN and COS Windings
are equal to the value of the Reference Voltage multiplied by the SIN or COS of the angle of the
input shaft from a fixed zero point. Thus, the resolver provides two voltages whose ratio
represents the absolute position of the input shaft (SIN θ / COS θ = TAN θ, where θ = shaft
angle). Because the ratio of the SIN and COS voltages is considered, any changes in the
resolvers’ characteristics, such as those caused by aging or a change in temperature are ignored.
θ
V
R
R1 (Red/Wht)*
R2 (Blk/Wht)
COS
Winding
S4 (Blu)
S2 (Yel)
S3 (Blk)
S1 (Red)
SIN
Winding
V
C
= V
R
COS
θ
Rotary
Transformer
V
S
= V
R
SIN
θ
*(Wire Color)
Reference Winding
SIN and COS Windings
Rotary
Transformer
Figure 1.3 Resolver SchematicFigure 1.2 Resolver Cut away View