Chapter 3. Description Of Operation; Introduction; Speed Control - Woodward 723PLUS Technical Manual

Manual 26482
The three primary functions of this 723PLUS control are speed control, fuel
limiting, and torque sharing. These functions will be broken down in this chapter
as follows:

Speed Control

Speed Input
Speed Reference
Dynamics
Actuator Output
The primary job of this 723PLUS control is to control the engine speed. The
control compares the engine speed to the speed reference and then adjusts the
actuator output to maintain a zero error between engine speed and the speed
reference. This is done with a PID controller. Several tunable variables
(dynamics) allow the 723PLUS control to be tuned for optimal performance over
a wide range of engine operating conditions.
Speed Input
One or two speed sensors provide the feedback for the speed control PID. These
allow the application to sense engine speed in two ways: single speed sensing
input, or redundant speed sensing. For redundant speed sensing, the speed
control selects MPU #1 for use when both speed inputs are valid. Otherwise the
valid input with the higher frequency is used. The method used to detect speed is
hard configured for digital type detection. The digital detection method senses
and responds to speed changes very quickly.
An adjustable low-pass speed sensor filter is provided, which is adjusted in
Service mode, under the header E**DYNAMICS DE-CLUTCHED**, at prompt 09
SPEED FILTER 1 HZ. The filter is used to attenuate engine firing frequencies.
This filter is active on both speed signal inputs regardless of the speed sensing
mode. The proper roll-off frequency setting can be found using the following
formula:
camshaft frequency = (engine rpm)/60 [for 2-cycle engines]
firing frequency = (camshaft frequency) x (number of cylinders)
Initially set the filter frequency to the firing frequency or 15.9 Hz, whichever
is lower. A lower setting increases filtering but slows response. Settings
below 10 Hz are not recommended.
Woodward
Chapter 3.
Description of Operation

Introduction

Fuel Limiting
Torque Sensor
Start Fuel Limiting
Maximum Fuel Limiting
Speed Control
= (engine rpm)/120 [for 4-cycle engines]
723PLUS Digital Marine Control
Torque Sharing
Torque Sharing Lines
Torque Input
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