1989-07-01

Embedded Digital Control for Aircraft Environment Control Systems: A Practical vehicle Management System Approach 891438

Second-generation digital controls for advanced commercial and military environmental control systems (ECS's) offer significant advantages in control operation, fault tolerance, and fault isolation/built-in test (BIT). “Embedding” the control functions in an integrated digital ECS architecture interfacing with aircraft centralized supervisory functions offers a practical vehicle management system (VMS) which yields significant benefits in system performance, hardware and software support-ability, and program cost and schedule management tasks. This paper presents basic control operational concepts now associated with second-generation digital ECS control and quantitative tradeoff study results showing how these concepts benefit from an integrated, “embedded” controls design approach.FIRST-GENERATION DIGITAL CONTROLS for ECS's have been utilized in several production aircraft programs. Second-generation integrated digital controls for advanced commercial and military ECS's now under development offer significant improvements in control law algorithms, fault tolerance methods, and fault isolation/built-in test (BIT) effectiveness. However, the method of implementation - whether incorporated in some form of centralized VMS computer or in subsystem-dedicated computers - has been the subject of much debate.The purpose of this paper is to present tradeoff studies that show the benefits of integrating the ECS controls into “embedded” digital ECS architecture interfacing with supervisory computers. This approach will be shown to be the most practical approach for integrating the ECS controls into the overall VMS design. An opening discussion of first- and second-generation ECS digital controls is presented to provide the necessary baseline configuration factors for the tradeoff studies.

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