Steffen Ochs

Design of Control Concepts for a Smart Beam Structure with Sensitivity Analysis of the System

A smart structure is a structure that can reduce a structural vibration by means of the integration of one or more sensor, actuator, and controller. A sensor detects a vibration in the structure and transfers a signal to a controller. The controller, designed to compensate the structural vibration, then computes the desired control signal and sends it to an actuator. A piezoelectric ceramic patch is often used, as in the present study, as a sensor or an actuator in a smart structure. A smart structure with a properly designed controller can reduce the structural vibration without changing the structure’s physical dimensions. Since a smart structure contains more uncertainty factors, not least due to the additional interfaces in comparison to a passive structure, the smart structure should be well analyzed to ensure its reliability and robustness. This paper focuses on how to set up a numerical model for a smart beam structure, how to design its control concept, and how to investigate the controller’s robustness by means of the Design of Experiments (DoE) method (In this paper experiment refers to numerical simulation.). A full factorial design is used, in which the parameters of the smart structure are either varied in their distributed range or held constant, so that several structures are designed with slight variations. This study aims at determining, which controller is the most robust by comparing the performance for different structural variations of the smart structure. Only if a smart structure is connected to a robust controller, its reliability can be analyzed, which is the aim of further research.

EFFICIENT EXPERIMENTAL VALIDATION OF STOCHASTIC SENSITIVITY ANALYSES OF SMART SYSTEMS

A method for the efficient experimental validation of stochastic sensitivity analyses is proposed and tested using a smart system for vibration reduction. Stochastic analyses are needed to assess the reliability and robustness of smart systems. A model-based design of experiments combines an experimental design with the results of a previous numerical sensitivity analysis. To test this method, a system of structural dynamics is used. Active suppression of disturbing vibrations of a cantilever beam by means of active piezoelectric elements is considered. The observed target variables are the level of vibration reduction at the beam’s end and the fundamental frequency considering five uncertain system variables. Based on a numerical model of the piezoelectric beam, a variance-based sensitivity analysis is performed to determine each design variable’s impact on the target variables. According to these numerical results, a model-based experimental design is established and the experiments are conducted. In comparison to a fully five-factor factorial experimental design, the model-based approach reduced the experimental effort by 50%, without great loss of information.