Engineers at the Airbus High Lift Test Centre in Bremen, Germany needed a system to test the landing flap systems for the new Airbus A350. This had two landing flaps at each wing that were stressed by high aerodynamic forces. These forces needed to be simulated during the test.
The motion control system for testing the landing flaps was mounted in a metal framework. The load frames were connected to six hydraulically operated servo cylinders and followed the flap motion. Pneumatically operated plunger cylinders mounted on metal frames simulated the load. The six hydraulic cylinders were located so that the range of motion and load forces were spread as equally as possible and each had closed-loop position control.
A standard industrial PC with a sampling rate of 1000 Hz, employed an EtherCAT fieldbus to control these 12 axes (six for each flap) as well as the other actuators. Since both the absolute value and the direction of the aerodynamic forces changed during the test, the metal framework with the pneumatic cylinders had to follow predefined spatial motion. The force and motion profiles were described by coordinates of the plane. From these coordinates the PLC calculated in real-time the required cylinder strokes during the motion.
In addition to spatial motion of the metal frame there was another force applied to the system to simulate the load torque to a drive shaft system. The motion for this subsystem required a highly specialised closed loop proportional valve. The testing of the motion of landing flaps was controlled by a combination of rotary drive, drive shafts and gears. The test system had an additional rotary drive to apply load torque to the rotary drive of the plane.
The request
Moog was selected to design and build highly specialised servo valves to fulfil these unique requirements. From the beginning it was clear that the application called for Moog’s digital valve technology and special interfaces would be needed.
In addition to the high performance hydraulic functionality, the required valves needed specific features and characteristics:
* EtherCAT fieldbus interface.
* Analog inputs for pressure transducers.
* An interface for an incremental position encoder.
* A new analog input for force control by a strain gauge.
* Special wiring for the 11-pole + PE connector.
The solution
The Moog Digital Servo Valve Series D671 with integrated I/O interfaces was determined to be the right solution to provide the closed loop axis control in the flap test system. This valve, equipped with an EtherCat fieldbus interface, controlled the axis positions via the central PLC.
Tge RESULT
The combination of a fast fieldbus system, a servo valve with integrated I/Os and a hydraulic servo cylinder resulted in a high performance automation solution with many benefits:
* Components were easy to change because the intelligence of the system was not programmed in the firmware of the components, but in the industrial PLC system.
* The coincidental use of a hydraulic servo valve as I/O component for typical actuating elements and sensors on hydraulic cylinders without using these signals for itself, was highly beneficial for open automation solutions.
* Minimal cabling reduced expense, complexity and space requirements.
* Local parameterisation offered users greater flexibility compared with previous local axis controller solutions.
To find out how Moog achieved this, read the full story online at http://motioncontrol.co.za/+moog1
For more information contact Willie Steyn, Moog, +27 (0)12 653 6768, [email protected], www.moog.com
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