AMCI ANS1 ANYNET-I/O, User Manual

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17
CHAPTER 2
L
IMIT
S
WITCH
F
UNCTIONALITY
Global Machine Position
The Global Machine Position is the position value that all limit switches are based on. Limit switch positions
can be offset from the Global Machine Position, but all position values increase and decrease in step with this
position. The ANS1 uses one of two types of sensors to determine the Global Machine Position.

Resolver:
An absolute position sensor that is designed for harsh industrial environments. The resolver
is also an absolute sensor and will retain machine position through power cycles. The ANS1 decodes
the resolver position to 4,096 counts per turn.

Quadrature Encoder:
An incremental position sensor. The ANS1 is compatible with all encoders that
have industry standard A-quad-B outputs. This includes the incremental DuraCoders that are available
from AMCI. The advantage of the incremental encoder is the fact that it is easy to change the length of
a machine cycle by reprogramming the ANS1. The ANS1 always uses 4X decoding when using a
quadrature encoder, so the counts per turn is equal to the number of lines of the encoder.
Three programmable parameters are used when calculating the Global Machine Position.

Counts per Cycle:
[Range of 2 to 4,096, Default of 4,096] Sets the number of counts the position sen-
sor generates for a single cycle of the machine. Most applications have a one to one ratio of sensor
turns to machine cycles. In these applications, this parameter should be set to 4,096 when using a
resolver or four times the number of encoder lines when using a quadrature encoder. (The ANS1 always
uses 4X decoding when using an encoder. This limits the resolution of the encoder to 1,024 lines.)
If your application does not have a one to one ratio of sensor turns to machine cycles, see the
Advanced Parameter Use section below.

Full Scale Count: [Range of 1 to (Counts per Cycle), Default of 360] Used to scale the Counts per
Cycle value to engineering units. The scaled value is reported as the Global Machine Position and is
used while programming limits. If a resolver is used and the Counts per Cycle and Full Scale Count
parameters are left at their default values, the ANS1 will report 360 counts per sensor rotation.

Scaled Machine Offset: [Range of -( Full Scale Count -1) to +( Full Scale Count -1)] Used to offset the
Global Machine Position without physically rotating the shaft of the position sensor. The Scaled
Machine Offset is applied after the position is scaled using the Full Scale Count parameter. This offset
is a circular offset. It offsets the position without changing its range of values. For example, with a Full
Scale Count of 360 and a position value of 10, programming a Scaled Machine Offset of -20 will result
in a Global machine Position of 350.
One additional parameter is available to simplify setting the machine position. This value allows you to pre-
set the Global Machine Position.

Machine Preset Value: [Range of 0 to ( Full Scale Count -1), Default of 0] This parameter defines the
value that you want the Global Machine Position to become when you issue a preset command. The
ANS1 presets the Global Machine Position by recalculating the value of the Scaled Machine Offset.
The ANS1 can be preset through a bit on the network output data. The module also give you the ability to
program one of the sixteen inputs as a Machine Preset Input. Once programmed, an inactive-to-active transi-
tion on the input will preset the Global Machine Position to the programmed Machine Preset Value.
This chapter covers the ANS1 functionality and parameters needed to have the
ANS1 act as a programmable limit switch. Parameter that affect position and
velocity feedback are covered, as well as the parameters that set limit switch set-
points and advances. Finally, this chapter also covers limit switch ANDing func-
tionality.