Description
MOOG G771K202A — Technical Overview
Product: G771K202A, Servo Control Module / Electronic Drive Unit
Manufacturer: Moog Inc.
Primary Application: A high-performance servo controller/amplifier module designed for precise closed-loop control of electro-hydraulic servo valves (EHSV), electro-mechanical actuators (EMA), or other proportional devices in demanding motion control applications within aerospace, defense, and industrial automation.
1. Core Overview & Positioning
The Moog G771K202A is a specialized electronic control module from Moog’s G771 series of servo controllers. It functions as the intelligent power and control interface between a motion controller (host computer/PLC) and a high-performance servo actuator. Its primary role is to execute precise closed-loop control algorithms, driving an actuator to accurately follow a position, velocity, or force command.
Key Philosophy: It provides the necessary signal conditioning, power amplification, and high-speed control logic to transform a low-level command signal into a precise, high-power output capable of driving demanding servo loads with exceptional dynamic response and stability.
2. Key Features & Functions
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Closed-Loop Servo Control: Implements advanced control algorithms (typically PID with velocity/acceleration feedforward, notch filters, and advanced compensation) to minimize the error between the command signal and the actual feedback from a position/velocity transducer (e.g., LVDT, RVDT, resolver).
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High-Current Output Stage: Contains a power amplifier designed to deliver the specific current (often in the range of ±100mA to ±2A) required to drive the inductive coil of a high-performance Moog servo valve or the windings of a torque motor.
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Flexible Input Configuration:
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Command Input: Accepts an analog command signal (typically ±10V DC differential).
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Feedback Input: Primarily designed for AC-excited LVDT (Linear Variable Differential Transformer) or RVDT (Rotary Variable Differential Transformer) feedback, providing the excitation signal and measuring the return amplitude/phase to determine actuator position.
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Comprehensive Diagnostics & Protection:
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Continuous monitoring for coil faults (open circuit, short circuit).
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Feedback sensor health monitoring (signal level, frequency).
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Overtemperature protection for the output stage.
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Command-Feedback discrepancy (excessive following error) detection.
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Field Configurable: Control loop parameters (Proportional, Integral, Derivative gains, feedforward gains, filter frequencies, current limits) are adjustable, typically via Moog configuration software or a programming pendant, allowing the drive to be tuned for the specific actuator and load dynamics.
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Robust Design: Engineered for reliable operation in harsh environments, with protection against vibration, shock, and wide temperature ranges. The PCB is often conformally coated.
3. Model Number Analysis & Specifications
Inferred Technical Specifications (Must be verified with official datasheet):
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Output Drive: Current output, likely in the range suitable for Moog G631, G761 series servo valves.
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Command Input: ±10V DC differential, high impedance.
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Feedback: AC LVDT/RVDT input with programmable excitation.
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Power Supply: Requires external DC power supplies, typically ±15V DC for control logic and a higher voltage (e.g., +24V to +80V DC) for the output stage.
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Communication: May include a service port (RS-232/422/485) for configuration and monitoring via Moog software tools.
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Form Factor: Typically a printed circuit board (PCB) assembly designed for chassis or enclosure mounting.
4. System Integration & Application
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Role in Control Chain: It acts as the dedicated servo drive in a hierarchical system:
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Host Motion Controller calculates trajectory → sends Analog Command to G771K202A.
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G771K202A processes command and LVDT feedback → outputs Drive Current to Servo Valve.
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Servo Valve controls hydraulic flow → moves Actuator/Piston.
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LVDT on actuator provides Position Feedback to G771K202A, closing the loop.
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Configuration & Tuning: Essential for performance. Using Moog software (e.g., Moog Servo Driver Suite or a dedicated programmer), an engineer must:
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Set LVDT excitation parameters.
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Perform LVDT null/span calibration.
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Tune the PID and feedforward gains to achieve the desired step response (fast, stable, without overshoot).
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Integration: Mounted in a system control cabinet, interfacing with a higher-level multi-axis controller (like a Moog MCU-2000) or a custom automation system.
5. Typical Applications
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Industrial Automation & Test:
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Servohydraulic Test Systems: Driving actuators in materials testing machines (fatigue, structural testing).
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Simulator Motion Bases: Controlling hydraulic actuators for flight, driving, or marine simulators.
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Precision Industrial Machinery: For controlling rollers, knives, or presses requiring ultra-precise, high-force motion.
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Aerospace & Defense:
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Flight Control Actuation: Research and development test rigs for control surfaces.
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Fuel Control Systems: For gas turbine engine test stands.
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Specialized Vehicle Control: Turret stabilization, weapon pointing systems.
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