Development of a Smart Actuator for Turbine Engine Applications

The application of distributed control systems to turbine engine controls offers the potential for major reductions in development time and costs for the engine control and the engine. Once the data bus and power bus are standardized for elements of a distributed control system, the industry will have a group of sensors, actuators, and controllers that could be interchangeable between applications. Software and hardware will still require modification to fit the specific application, however, great strides will have been made toward a “plug and play” capability between sensors, actuators, and controllers all tied together on the same data bus. The main controller in a distributed control system, except for software, would be interchangeable from engine to engine. This paper describes the design and development of the electronics for a smart actuator and discusses the design considerations which were used to guide the requirements. Requirements unique to turbine engine applications include temperature environments to 30° C, a severe vibration environment, minimum size and weight, and very high reliability. The electronics developed for the smart actuator were packaged on credit card sized printed wiring board modules. Two of these modules were packaged in a housing approximately 23×3.4×1.1 inches. The electronics operate from 28 volt DC power and communicate with the rest of the control system via the MEL-STD-1553B data bus. Although a hydraulic actuator was chosen as the demonstration vehicle, the electronic module is adaptable to any servo application and can be expanded to read any of the common engine sensors and operate solenoids. The chosen actuator was intended as a development tool to expose the design problems of distributed systems. Therefore, this first demonstration unit was designed using electronic components rated for 125° C operation. AlliedSignal is currently a member of a consortium of companies under DARPA sponsorship developing a family of SOI (silicon-on-insulator) integrated circuits rated for 200° C operation. Our current 125° C design is compatible with the new devices being developed. A 200° C unit is planned for 1998. Further improvements in the metalization used in the SOI devices will allow reliable long term operation to about 300° C. Devices for this higher temperature range are expected to be available in 1999.