Parameter Estimation and Analysis of Actuators for the Bact Wind-tunnel Model

This paper describes the development of transfer function models for the trailing edge and upperand lower-spoiler actuators of the Benchmark Active Control Technology (BACT) wind-tunnel model for application to control system analysis and design. A simple nonlinear least squares parameter estimation approach is applied to determine transfer function parameters from frequency response data. Unconstrained quasi-Newton minimization of weighted frequency response error was employed to estimate the transfer function parameters. An analysis of the behavior of the actuators over time to assess the effects of wear and aerodynamic load using the transfer function models is also presented. The frequency responses indicate consistent actuator behavior throughout the wind-tunnel test and only slight degradation in effectiveness due to aerodynamic hinge loading. The resulting actuator models have been used in design, analysis, and simulation of controllers for the BACT. The resulting controllers have successfully suppressed flutter over a wide range of conditions.