Adaptive Output Feedback Control of Flexible Systems

Actuator nonlinearity;Output feedback;Adaptive control;Neural networks;Flexible systems

Yang, Bong-Jun ; Aerospace Engineering

University:Georgia Institute of Technology

Department:Aerospace Engineering

关键词: Actuator nonlinearity;    Output feedback;    Adaptive control;    Neural networks;    Flexible systems;   

Others  :  https://smartech.gatech.edu/bitstream/1853/5248/1/yang_bong-jun_200404_phd.pdf

美国|英语

来源: SMARTech Repository

【 摘 要 】

Neural network-based adaptive output feedback approaches that augment a linear control design are described in this thesis, and emphasis is placed on their real-time implementation with flexible systems. Two different control architectures that are robust to parametric uncertainties and unmodelled dynamics are presented. The unmodelled effects can consist of minimum phase internal dynamics of the system together with external disturbance process.Within this context, adaptive compensation for external disturbances is addressed.In the first approach, internal model-following control, adaptive elements are designed using feedback inversion. The effect of an actuator limit is treated using control hedging, and the effect of other actuation nonlinearities, such as dead zone and backlash, is mitigated by a disturbance observer-based control design. Theeffectiveness of the approach is illustrated through simulation and experimental testing with a three-disk torsional system, which is subjected to control voltage limit and stiction.While the internal model-following control is limited to minimum phase systems, the second approach, external model-following control, does not involve feedback linearization and can beapplied to non-minimum phase systems. The unstable zero dynamics are assumed to have been modelled in the design of the existing linear controller. The laboratory tests for this methodinclude a three-disk torsional pendulum, an inverted pendulum, and a flexible-base robot manipulator.The external model-following control architecture is further extended in three ways. The first extension is an approach for control of multivariable nonlinear systems. The second extension is a decentralized adaptive control approach for large-scale interconnected systems. The third extension is to make use of anadaptive observer to augment a linear observer-based controller. In this extension, augmenting terms for the adaptive observer can be used to achieve adaptation in both the observer and thecontroller. Simulations to illustrate these approaches include an inverted pendulum with its cart serially attached to two carts(one unmodelled), three spring-coupled inverted pendulums, and an inverted pendulum with its initial condition in a range in which a linear controller is destabilizing.