System Identification and Robust Controller Design Using Genetic Algorithms for Flexible Space Structures

Abstract

This paper is concerned with the problem of identifying and controlling flexible structures. The structures used exhibit some of the characteristics found in large flexible space structures (LFSSs). Identifying LFSS are problematic in the sense that the modes are of low frequency, lightly damped, and often closely spaced. The proposed identification algorithm utilizes modal contribution coefficients to monitor the data collection. The algorithm is composed of a two-step process, where the input signal for the second step is recomputed based on knowledge gained about the system to be identified. In addition, two different intelligent robust controllers are proposed. In the first controller, optimization is concerned with performance criteria such as rise time, overshoot, control energy, and a robustness measure among others. Optimization is achieved by using an elitism based genetic algorithm (GA). The second controller uses a nested GA resulting in an intelligent linear quadratic regulator/linear quadratic Gaussian (LQR/LQG) controller design. The GAs in this controller are used to find the minimum distance to uncontrollability of a given system and to maximize that minimum distance by finding the optimal coefficients in the weighting matrices of the LQR/LQG controller. The proposed algorithms and controllers are tested numerically and experimentally on a model structure. The results show the effectiveness of the proposed two-step identification algorithm as well as the utilization of GAs applied to the problem of designing optimal robust controllers.

Active vibration control using genetic algorithm-based system identification and positive position feedback

“…Genetic algorithms can also be applied to the controller design problem. In [19] a GA was applied to the problem of designing a pole placement controller, and in [20] to finding the optimal coefficients in the weighting matrix of a linear quadratic regulator/linear quadratic Gaussian controller. Also, in [21] a fuzzy logic integrated GA was used for vibration control of a cylindrical shell.…”

Novel Distributed PZT Active Vibration Control Based on Characteristic Model for the Space Frame Structure

“…According to the expression in (3) and (6)- (7), the th characteristic model is Similarly, one has the characters of characteristic parameters in th output loop as…”

“…Hazra et al proposed a method which integrates the blind identification with timefrequency decomposition of signals for flexible structures [6]. Schoen et al presented an identification algorithm which utilizes modal contribution coefficients to monitor the data collection for large flexible space structures [7]. Although some aforementioned methods have been extensively used in space structure identification, there still exist several disadvantages.…”

Flexible Multibody System Linear Modeling for Control Using Component Modes Synthesis and Double-Port Approach

“…The modeling of flexible structures has been a major concern in control applications for the last 30 years due to the development of larger and lighter structures [1]. Large size and reduced mass imply a reduction of the rigidity of the structure, lowering the associated natural frequencies [2]. Low natural frequencies may interfere with the controller's bandwidth, affecting the dynamic behavior of the system.…”