Resonant mode controllers for launch vehicle applications

Electromechanical actuator (EMA) systems are currently being investigated for the National Launch System as a replacement for hydraulic actuators due to the large amount of manpower and support hardware required to maintain the hydraulic systems. EMA systems in weight-sensitive applications, such as launch vehicles, have been limited to around 5 HP due to system size, controller efficiency, thermal management, and battery size. The authors present design and test data for an EMA system that competed favorably in weight and is superior in maintainability to the hydraulic system. The EMA system uses DC power provided by a high-energy-density bipolar lithium thionyl chloride battery, with power conversion performed by low-loss resonant topologies, and a high-efficiency induction motor controlled with a high-performance field-oriented controller to drive a linear actuator.< >