This paper addresses tracking-control of hysteretic systems using a gain-scheduled (GS) controller. Hysteretic
system with variable stiffness and damping is represented as a quasi linear parameter varying (LPV) system.
Designed controller is scheduled on the measured/estimated stiffness and damping in real-time. GS controller
is constructed from the parameter dependent Lyapunov matrices, which are obtained as optimal solutions of
linear matrix inequalities (LMIs) that ensures the feasibility solution for closed loop system performance. The
proposed method is worked on semiactive independently variable stiffness (SAIVS) device. It is shown that the
gain-scheduled controller developed for the quasi-LPV system results in excellent tracking performance even in
the cases where robust-H∞ controller failed to function.
In this work, we propose an Adaptive Neuro Fuzzy Inference System (ANFIS) based hysteresis modeling and
control strategy for a thin Shape Memory Alloy (SMA) wire. Controlling the SMA wire is a challenging problem
because of its dynamic hysteretic behavior. By using a hybrid learning procedure ANFIS architectures are
powerful tools for many applications, such as identifying nonlinear parameters in a controlled system, predicting
chaotic time series and modeling nonlinear functions. We tested our ANFIS model by making it predict major
and minor hysteresis loops in different driving frequencies and compared them with the experimental data. To
compensate the hysteretic effect, we used an inverse ANFIS model and used it directly as a controller. After
dramatically reducing the hysteretic effect, we implemented a PI control to fine tune the response.
KEYWORDS: Actuators, Ferroelectric materials, System identification, Control systems, Sensors, Linear filtering, Control systems design, Filtering (signal processing), Matrices, Electronic filtering
This paper presents the development and application of an H∞ fault detection and isolation (FDI) filter and
fault tolerant controller (FTC) for smart structures. A linear matrix inequality (LMI) formulation is obtained
to design the full order robust H∞ filter to estimate the faulty input signals. A fault tolerant H∞ controller
is designed for the combined system of plant and filter which minimizes the control objective selected in the
presence of disturbances and faults. A cantilevered flexible beam bonded with piezoceramic smart materials,
in particular the PZT (Lead Zirconate Titanate), in the form of a patch is used in the validation of the FDI
filter and FTC controller design. These PZT patches are surface-bonded on the beam and perform as actuators
and sensors. A real-time data acquisition and control system is used to record the experimental data and
to implement the designed FDI filter and FTC. To assist the control system design, system identification is
conducted for the first mode of the smart structural system. The state space model from system identification
is used for the H∞ FDI filter design. The controller was designed based on minimization of the control effort
and displacement of the beam. The residuals obtained from the filter through experiments clearly identify the
fault signals. The experimental results of the proposed FTC controller show its e effectiveness for the vibration
suppression of the beam for the faulty system when the piezoceramic actuator has a partial failure.
This paper presents an explicit expression for an upper bound on H2 norm for structural systems with collocated
sensors and actuators. Using a linear matrix inequality (LMI)-based representation of the H2 norm of a collocated
structural system, we determine an explicit upper bound on H2 norm of such a system. The present paper also
addresses the problem of output H2 feedback controller design for collocated systems. Employing some simple
algebraic tools, we derive an explicit parametrization of H2 feedback controller gain which guarantees a prescribed
level of H2 performance for the closed-loop system. Numerical examples will be finally provided to validate the
efficiency and benefits of the proposed method.
In this work, we revisit the problem of actuator placement within the context of spatial robustness. When one
optimizes location-parameterized H2 or H∞ closed loop measures, arrives at actuator locations that provide
performance optimality. However, these measures assume an a priori given distribution of disturbances. When
the above measures include an additional optimization stage whereby one searches for the worst distribution of
disturbances, then the resulting actuator location will result in both an improved performance and enhanced
spatial robustness. Using an analytical bound approach that provides an explicit expression for an upper bound
on the H∞ norm of the system transfer function, the worst distribution of disturbances can be found that
maximizes the open loop H bound. Subsequently, an optimal actuator location is found that minimizes the
H∞ bound of the closed loop transfer function. This method minimizes the optimization complexity and provides
great computational advantages in large scale flexible systems where the solution to H∞ optimization problems
using standard tools becomes computationally prohibitive.
KEYWORDS: Computing systems, Control systems, Feedback control, Optimization (mathematics), Digital signal processing, Mechanical engineering, Finite element methods, Linear filtering, Systems modeling, Ferroelectric materials
The objective of this paper is to provide an experimental verification of a new H-infinity control scheme on a flexible beam which uses a collocated PZT actuator/sensor pair. We use an analytical bound approach that provides an explicit expression of an upper bound on the H-infinity norm of the closed-loop system and an explicit parametrization of the corresponding output feedback control gains. The method has great computational advantages for large scale structural systems where the solution of H-infinity optimization problems using standard tools could be computationally prohibitive. Both experimental and numerical results are presented that provide a comparison of the performance and the computational requirements on the controller design using the standard H-infinity formulation and the proposed analytical bound approach.
Iterative redesign techniques are proposed to integrate the design of the structural parameters and the active control parameters for vector second-order lumped-parameter structural systems. The objective is to minimize the required active control effort to satisfy given output variance constraints and robust performance constraints. The problem is formulated as an iterative sequential control design followed by control/structure redesign. Each step of the iterative algorithm is formulated as a Linear Matrix Inequality (LMI) optimization problem that can be solved effectively using available LMI solvers. Convergence of the proposed algorithm to a solution that provides improved control effort and robust stability compared to the single- step structural design followed by control design is guaranteed. Both static state-feedback and dynamic output feedback problems are considered. Numerical examples demonstrate the use of the proposed iterative algorithms.
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