WOODWARD 8440-1409 Servo Driver / Actuator Control Module

Description

1. Core Overview & Positioning

2. Key Features & Functions

• Closed-Loop Position Control:​ Implements a fast digital control algorithm (typically PID-based) to maintain precise actuator position by comparing the command signal with real-time feedback from a Linear Variable Differential Transformer (LVDT)​ or Rotary Variable Differential Transformer (RVDT).
• Dual Input Processing:
  • Command Input:​ Accepts an analog position setpoint (typically ±10V DC or 4-20mA) from the primary speed/load controller.
  • Feedback Input:​ Interfaces with an AC-excited LVDT/RVDT attached to the actuator to measure actual position.
• High-Current Output Drive:​ Provides a modulated current output (typically in the range of ±40 mA to ±200 mA) capable of driving the inductive coil of a proportional or servo-proportional hydraulic valve.
• Integrated Diagnostics & Protection:
  • Continuous monitoring of LVDT/RVDT health (signal level, frequency, phase).
  • Coil and driver stage fault detection (open circuit, short circuit, over-current).
  • Detection of excessive position error (deviation between command and feedback).
• Field-Configurable Parameters:​ Allows tuning of servo loop gains (Proportional, Integral, Derivative), current limits, LVDT excitation, and response characteristics via configuration software (Woodward Toolkit) to match the specific actuator dynamics.
• Communication Interface:​ Typically includes a Woodward proprietary communication port​ (e.g., for Gov. Bus/NetBus) for integration with the primary controller, configuration, and diagnostics.

3. Common Technical Specifications

• Part Number Context:​ The -1409suffix specifies this exact variant’s hardware configuration, input/output ranges, and firmware features.
• Command Input:​ Configurable analog input, typically ±10V DC or 4-20mA.
• Feedback Input:​ Designed for industry-standard AC LVDT/RVDTs (common excitation: 3 Vrms @ 2.5 kHz or 5 Vrms @ 5 kHz).
• Output Drive:​ Current output suitable for driving standard servo valve coils.
• Power Supply:​ Requires external DC power, commonly ±15V DC for control circuitry and a separate +24V to +80V DC for the power output stage.
• Physical Form:​ A printed circuit board (PCB) assembly designed for mounting in a Woodward control cabinet or a dedicated drive chassis.
• Status Indicators:​ LEDs for power, status, and fault conditions.

4. System Integration & Configuration

• Role in Control Hierarchy:​ Acts as a slave drive unit​ to a primary Woodward Digital Governor. It executes precise position commands but relies on the master for the overall control strategy.
• Configuration Software:​ Entirely configured and tuned using Woodward Toolkit​ PC software. The process involves:
  1. Hardware Setup:​ Defining I/O signal types and scaling.
  2. LVDT Calibration:​ Mapping the LVDT’s electrical output to the actuator’s physical stroke (min/max travel).
  3. Servo Tuning:​ Adjusting PID and dynamic compensation parameters to achieve optimal step response—fast and stable without oscillation—specific to the connected actuator.
• Integration:​ Installed in a slot within a Woodward control rack​ or enclosure. It interfaces with the actuator’s LVDT and servo valve, and communicates with the primary controller over a dedicated bus.

5. Typical Applications

• Gas Turbine Control:​ Driving fuel metering valves, gas control valves, and inlet guide vanes (IGVs).
• Steam Turbine Governing:​ Positioning governor valves and intercept valves.
• Diesel Engine Control:​ Governing actuators for fuel injection systems.
• Compressor Control:​ Driving anti-surge control valves.