Electric and Smart Material Self-Contained Actuators for LCAC Rudder Control

Hydraulic actuators, with the associated hydraulic reservoir and high-pressure lines, perform the rudder-control actuation on the LCAC vehicle. Frequent maintenance and related costs are the primary driver in seeking an alternative self-contained electricactuator to take advantage of recent developments in electric actuator technology. The anticipated benefits to the Navy are reduced maintenance, better reliability, reduced total system cost, and reduced actuator weight and size.We propose to investigate the feasibility and outline the advantages of replacing the conventional hydraulic rudder actuator with a self-contained electric actuator. We will consider several embodiments encompassing the state-of-the-art in electricactuator technology. First is an electro-mechanical actuator similar to the EMA developed under the EPAD program and demonstrated in aileron actuation on the F-18. Second is an Electro-Hydrostatic Actuator (EHA). Third is a linear screw-type hybridactuator, with several smart materials evaluated as the primary driving element (PMN-PT single crystal, MSM, Terfenol, SMA).In Phase I, we will analyze and outline the potential benefit of replacing the LCAC rudder actuators with self-contained electric actuators. In Phase II, we will develop and demonstrate a full-scale rudder actuator prototype for the LCAC.Implementation of a fully electric self-contained rudder actuator would benefit the LCAC in several important aspects. First, the electric actuator requires no hydraulic lines or hydraulic fluid supply. The only connection is an electric cable to thefully self-contained rudder actuator. This will significantly reduce the maintenance requirements. Second, the vehicle reliability will be increased by a self-contained electric actuator. With a hydraulic actuator, loss of a single actuator or hydraulicpiping can lead to a total loss of many hydraulic systems. A self-contained electric actuator would be much more failsafe, and an actuator loss would be isolated to only one component. Moreover, the self-contained electric actuator may be less vulnerableto damage and therefore less prone to failure. Third, electric actuators can represent a significant reduction of the total system weight, increasing the vehicle payload capacity. Fourth, electric actuators can achieve a total actuation system and lifecycle cost reduction, particularly when the cost of the hydraulic systems and related piping are considered.These factors make a strong case to the Navy to evaluate an upgrade to self-contained electric actuators for LCAC rudder control. The future of high-performance aircraft and air-cushion vehicles lies in self-contained fly-by-wire actuators. Futurevehicles will be more responsive, less complicated, more reliable and require almost no maintenance. The LCAC rudder is a technically feasible application to provide a successful and high-profile demonstration. The initial cost of performing an actuatorupgrade will be more than offset by decreased maintenance and total life cycle cost.