Investigation and Preliminary Development of a Modified Pseudo Control Hedging for Missile Performance Enhancement

The effects of actuator saturation for both conventional and adaptive controllers have been well documented. Pseudo Control Hedging (PCH) is one of the more recent methods introduced to address this issue. PCH requires the system be controlled to track a reference model. A software based actuator model, which predicts both position and rate saturations in real-time, is used to estimate the error between the commanded actuator position and the modeled actuator position. This error signal represents the “over-demanded” control actuation based on the expected system capability. From this error signal, a PCH signal can be generated which is used to adjust the reference model response, with the ideal result being the system will no longer operate at saturation. However, with the current configuration, this is not achievable. Instead, PCH is used to reduce the level and duration of actuator saturation. It can not eliminate it. Also, PCH designs in the literature do not address the problems encountered when implementing PCH on a two loop control architecture, particularly those of translating an inner loop PCH signal to an outer loop reference model. This paper presents the limitations of current PCH designs and presents a modified PCH design (MPCH) for a dynamic inversion missile autopilot that is an incomplete, yet improved, PCH design for two loop architectures.

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