Advanced Acuation Systems Development
Report Number: WRDC-TR-89-3076 Volume I Author(s): Jenney, Gavin D., Harry W. Schreadley, John A. Anderson, William G. Talley and Carl A. Allbright Corporate Author: Dynamic Controls, Inc. Laboratory: Flight Dynamics Laboratory Contract: F33615-S3-C-3600 Project: 2403 Task: 240302 AD Number: ADA213334
Abstract: This report describes six different research and development activities in flight control actuation. The activities are: (1) the development and test of a unique linear actuator sealing system for high-pressure systems, (2) the development and test of a digital servovalve using piezo-controlled high-speed solenoid valves, (3) the performance evaluation of an F-15 rudder actuator under applied loads, (4) the performance evaluation of a Mission Adaptive Wing section under different load conditions, (5) the evaluation of output impedance modification of an electrohydraulic actuator for flutter suppression, and (6) the development and test of a direct drive valve and electronics (analog and digital) for an F-16 Horizontal Tail/Flaperon actuator. This volume presents activities 1, 2, and 3. Volume II presents activities 4, 5, and 6. The sealing system was based upon using two-stage sealing for the piston rod seals and a pressure-activated backup ring configuration for the piston seals. The system eliminated the use of elastomeric dynamic seals. The piston rod first-stage seal was a laminar pressure-drop design which also served as a rod-support bearing. The piston rod seal used commercial no-elastomeric seals. The design was tested in actuators with thin wall cylinders at 8000 psi. Both MIL-H-83282 and CTFE hydraulic fluid systems were used for the testing. The system was tested with 500,000 impulse-loading cycles without any seal degradation. The digital servovalve was constructed with discrete high-speed solenoid valves to control the flow to a control actuator. The solenoid valves were a poppet design using a piezoelectric stack and a hydraulic motion amplifier. The valves activated in less than one millisecond. A microprocessor was used to control the valve and close the control loop. The servovalve worked successfully. Since the output flow of the solenoid valves is low, the approach is suitable primarily for small actuators. The performance of an F-15 rudder actuator was evaluated in a loading test stand. The evaluation was limited to the electrical command mode with the manual input grounded. The input/output performance characteristics in both unloaded and loaded operation were documented and analyzed. The actuator is a rotary vane actuator. The performance characteristics were similar to those of a linear actuator with the exception of characteristics directly affected by the vane sealing method.The Mission Adaptive Wing evaluation was a measurement of the loaded and unloaded performance characteristics of a test specimen produced by General Dynamics Corporation as a feasibility model. The actuation system for changing the camber of the test specimen is unique and was evaluated with a series of input/output measurements. The testing verified the general concept and revealed two design areas requiring additional development effort before flight test evaluation. The impedance modification investigation used electronic load pressure sensing to change the output impedance of an actuator over a selected frequency band. Changing the output impedance of an actuator potentially can be used to suppress classical slab-surface flutter. A demonstration actuator was sized to evaluate the impedance change capability. The test results indicated that the output impedance of an electrohydraulic actuator can be modified over a useful but limited frequency range using electronic pressure sensing and the control servovalve for the actuator. The limitation in the range of the impedance modification is primarily determined by the frequency response characteristics of the servovalve used to control the actuator. The F-16 Direct Drive Actuator development effort produced a direct drive control valve package which replaces the normal control valve and secondary actuator mounted on the actuator body of an F-16 Horizontal Tail/Flaperon ISA. The design maintains the failure-mode characteristics of the formal F-16 ISA including the centering mode as the final failure mode. The measured performance was equivalent to or better than that of the normal F-16 ISA. As part of the evaluation, a microprocessor-controlled initial checkout, failure monitor, and failure switching unit was evaluated with the test actuator.
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