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Inverter Positioning Section 5-3
5-3 Inverter Positioning
5-3-1 Features
Simple, accurate high-speed positioning can be achieved using an inverter.
This enables a far more economical positioning system than with a servomo-
tor.
Feedback Control
with Error Counter
A position error counter built into the CP1L CPU Unit enables high-precision
positioning with an Inverter using feedback control. The PULSE OUTPUT
instruction is used in the ladder program in the CP1L CPU Unit to output inter-
nal pulses to a built-in error counter.
The error counter calculates the position error from the number of input inter-
nal pulses and the number of feedback pulses from the rotary encoder, and
sends speed commands to the inverter so that the position error goes to zero.
Reducing Positioning
Time
With traditional inverter positioning, positioning patterns are created in which
set positions are detected to trigger changes in the speed. Pulses are read
from the encoder and compared to set values during positioning to enable
determining when a position requiring a speed change has been reached.
This results in positioning errors at speed-change points when stopping at
high speed, reducing stopping precision. To ensure high-precision positioning,
sufficient deceleration was required before stopping, but this increases the
positioning time.
With the CP1L’s inverter positioning function, feedback pulses are used so
that the prevent position is always known, increasing positioning accuracy.
And because preset positioning patterns are used for deceleration and stop-
ping, positioning time is reduced.
SYSMAC
CP1L
L1 L2/N
COM010305070911010305070911
00 02 04 06 08 10 00 02 04 06 08
10
00 01 02 03 04 06 00 01 03 04 06
COM COM COM COM 05 07 COM 02 COM 05
07
IN
OUT
CP1L CPU Unit
Feedback pulses
Ladder program
Inverter
PLS2 instruction
Speed command
RS-485 or analog output
Encoder
Motor
Error
counter
Positioning
instruction
Frequency
command
Internal pulses
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