MOOG Servo Electronics Products

Exciter/Demodulator: The core interface required for sensors such as Linear Variable Differential Transformer (LVDT) or RVDT (Rotary Transformer). NF123-204A1 provides adjustable excitation frequency (100-2500Hz) and amplitude (2-11Vp-p), and demodulates the AC modulation signal of LVDT into a DC voltage signal proportional to the displacement of the iron core, which is the key to forming a high-precision position closed loop.

Signal Conditioner: Used to process weak millivolt level differential signals generated from strain gauges, pressure sensors, load units, etc. Like NF123-211A1, gain range adjustment for jumper selection, signal summation amplification, and stable DC power supply can be provided to the sensor.

Ramp Generator: Convert step input commands into ramp outputs with adjustable slopes, used to control the acceleration and deceleration of the system, achieve smooth start stop, and avoid impact. This function is often integrated into the main servo amplifier card.

I/V converter, F/V converter: realize interface conversion of different signal formats. For example, converting the 4-20mA current command output by the PLC into a ± 10V voltage command (I/V), or converting the frequency signal of the pulse encoder into a DC voltage (F/V) proportional to the speed.

DC level detector/comparator: used as a window comparator, it triggers a relay or logic output when the input voltage reaches a preset level. Commonly used for speed arrival indication, zero point detection, or "Bang Bang" control.

Power module: Provides stable and pure ± 15Vdc, ± 24Vdc, and+5Vdc (for logic circuits) power to the entire electronic system. High end models have functions such as low ripple, low noise, overload protection, and power failure alarm output.

From Theory to Practice: Construction and Debugging of Typical Closed loop Control Systems

The document spends a lot of space, vividly demonstrating how to use Moog electronic modules to build a classic control system through detailed system diagrams, wiring diagrams, and step-by-step setup processes. This is not only a product description, but also a valuable engineering application guide.

Closed loop position control: This is the most fundamental and common application. The system consists of servo amplifiers, servo valves, hydraulic cylinders, and position sensors (such as DCDT or magnetostrictive displacement sensors). The core principle is that the servo amplifier compares the command input with the sensor feedback, generates an error signal to drive the servo valve, and moves the hydraulic cylinder until the feedback is consistent with the command and the error is zero. The document provides detailed construction and debugging steps from open-loop manual control to closed-loop PID control, emphasizing the sequence and importance of bias and gain adjustment.

Closed loop control of three-stage servo valve: For high flow applications, a three-stage servo valve is required. The Moog scheme cleverly utilizes exciter/demodulator cards to close the inner loop of the valve core position. LVDT detects the actual position of the three-stage valve core, and the demodulated DC voltage is sent to the servo amplifier together with the feedback signal from the external position sensor to form the outer loop. This independently adjustable structure of the inner and outer rings can ensure high-precision and fast positioning of the valve core, as well as precise control of the final load.

Closed loop force control: The system consists of servo valves, actuators, pressure sensors or load units, and servo amplifiers. The key lies in the application of signal conditioners, which amplify and condition the weak differential signal of strain gauge pressure sensors into a standard force feedback signal (force=area x pressure). The servo amplifier compares the force command with the force feedback, controls the opening of the valve to adjust the pressure in both chambers of the actuator until the output force matches the command. The document provides detailed instructions on how to use a regulator for zero (ZERO) and span (SPAN) calibration to achieve accurate force conversion in non equal area cylinders.

Closed loop speed control (with acceleration limitation): Typically, servo motors are used, and speed feedback is provided by a DC tachometer (Tachometer). The system forms a speed loop through a servo amplifier (often set as integral I control to achieve zero static error tracking). The ramp generator (or built-in amplifier function) is used to limit acceleration. The document specifically introduces how to interface with a PLC that outputs 4-20mA analog signals, requiring the use of an I/V conversion card.

Example of a complex multi axis PLC servo system: The document presents a highly representative dual axis (X-Y) PLC control system. Among them, the Y-axis (linear) uses I/V conversion card, ramp generator card, servo amplifier card, and position feedback conditioning card to achieve position closed-loop with acceleration and deceleration control. The X-axis (rotation) uses I/V conversion card, servo amplifier card, and introduces F/V conversion card to convert incremental encoder pulses into speed feedback, and then provides the "speed arrival" signal to the PLC through the DC level detector card. This example perfectly illustrates how to combine Moog's modular electronic products with an economical PLC with only discrete I/O points to build a fully functional complex motion control system.