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The Challenge:
Generation and Monitoring of Electro Mechanical actuation for Servo Hydraulics for fatigue test of aircraft shafts.
The Solution:
Developing a PC Based System using Data Acquisition boards controlled by LabVIEW for Generation of varying signals to a Servo Hydraulic system and Acquisition of feedback Signals in four Channels to ensure that the applied signals are translated into varying loads on the Shafts being fatigue tested.
Introduction:
The Shaft Fatigue Test System is a computer-based signal Generation and Acquisition System that is based on LabVIEW to Test the Durability and Strength of the Shafts in Aircrafts. It excites the Servo Hydraulic System by various types of Signals and Acquires Data from the pressure transducers to provide a close loop control. A High Speed Analog output card generates Waveforms and sends it to the Servo Hydraulic Actuators for Compression, Tension or Shear testing of Shafts. Feed Back from the shaft under test is sent back to the computer through signal conditioning modules (SC series) for a closed loop PID control.
Block Cycle Generators
A Block Cycle Generator developed using LabVIEW generates motion control waveforms to LabVIEW P.I.D Controller. Which in turn performs the Controlling and sends it to the Servo Hydraulic Actuators for Compression, Tension or Shear testing of Shafts. It generates block cycle profiles using sine, ramp, triangular, Saw tooth or square waveforms and joins together blocks of different amplitudes and frequencies. It generates a waveform using any combination of blocks and individual segments as well as creates a phase shift between two or more waveforms of the same constant frequency. This testing is performed to prove the Structural Durability and Strength of shafts in Aircraft Engines as a step in the Development Process.
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System Requirements and design challenges
The Block cycle generator has four output channels to control the Servo actuators simultaneously. Some of the main requirements are:
- An editor to enter all the Channel & Waveform parameters for each chosen channel. The system then drives the PID controller, which in turn drives the Servo actuators after signal Conditioning.
- The amplitude, duration, frequency for Sine, Square, Triangle, Saw tooth and Ramp waveforms should be specified relative to each Channel.
- The system should be able to view the profile for each channel for one nested Cycle.
- Display a Graph of Generated signal (command Channel) and acquired Signal (Control Channel) superimposed and another graph showing the Another Acquired signal (Monitor Channel) only.
- Status of the Generated Signal (Command Channel) such as Display the Block No., Number of Nested cycles, Duration time, Peak and Valley value of the Acquired signal (Control Channel).
- To store the data, timed acquisition for a given sample rate and duration or Continuous Acquisition for a period of 10 minutes.
When building the System we used a standard PC running Windows Me as the Platform. The PC contained National Instruments E Series MIO Data Acquisition Board PCI-6023E connected to SC-2345 Connector block with SCC-SG04 module used as Input and a PCI-6711 Analog Output Module card used as Output Module. BNC 2110 Connector Block for Connecting Cables to the Analog Servo Controllers.
Software Implementation
The block cycle generator creates waveforms, applies to the Actuators and monitors the System response. We use LABVEIW on a Windows PC to generate waveforms for each channel and then sent it to the Servo system. The feedback is then acquired and closed loop controlled for each channel respectively. The software development effort for this Project included the following tasks:
- Create Panels for the user to enter the Channel Parameters such as the Parameter Name, Channel Identifier, Full Scale Values and Selection of Metric and English units for Command, Control and Monitor channel
- Create additional Panel for the user to enter the Waveform Generation Parameter such as Waveform selection such as Level 1,Level 2,Frequency and Duration and see the Preview of entered data.
- Create additional VIs to display a Graph of Generated signal (command Channel) and acquired Signal (Control Channel) superimposed and another graph showing the Another Acquired signal (Monitor Channel) only. Status of the Generated Signal (Command Channel) such as Display the block No. Of Nested cycles, duration. Peak Value and Valley value of the Acquired signal (control Channel).
- Create VIs to store the data, timed acquisition for a given sample rate and time. Continuous Acquisition for a period of 10 minutes.
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