DESIGN OF REDUCED-ORDER p-CONTROLLER FOR FLEXIBLE STRUCTURES

2002

In this paper, a high-order sliding manifold control approach is adopted as a technique to effectively reduce the vibrations of a metal rectangular panel. A novel theoretical result for an output feedback control law is presented to show how the singular perturbation theory can be used to tackle the problem of active vibration control. Simulation results are provided to show the effectiveness of the proposed control strategy.

Design of a robust controller for multi input-multi output (MIMO) nonlinear uncertain dynamical system can be a challenging work. This paper focuses on the design and analysis of a high performance adaptive baseline sliding mode control for second order nonlinear uncertain system, in presence of uncertainties to reduce the vibration. In this research, sliding mode controller is a robust and stable nonlinear controller which selected to control of robot manipulator. The proposed approach effectively combines of design methods from switching sliding mode controller, adaptive model-free baseline controller and linear Proportional-Derivative (PD) control to improve the performance, stability and robustness of the sliding mode controller. Sliding mode controller has two important subparts, switching and equivalent. Switching part (discontinuous part) is very important in uncertain condition but it causes chattering phenomenon. To solve the chattering, the most common method used is linear boundary layer saturation method, but this method lost the stability. To reduce the chattering with respect to stability and robustness; linear controller is added to the switching part of the sliding mode controller. The linear controller is to reduce the role of sliding surface slope and switching (sign) function. The nonlinearity term of the sliding mode controller is used to eliminate the decoupling and nonlinear term of link’s dynamic parameters. However nonlinearity term of sliding mode controller is very essential to reliability but in uncertain condition or highly nonlinear dynamic systems it can cause some problems. To solve this challenge the baseline controller is used as online tune or adaptive controller. This controller improves the stability and robustness, reduces the chattering as well and reduces the level of energy due to the torque performance as well.

IFAC-PapersOnLine, 2020

The interaction between the flight control system and its structural modes becomes stronger if the frequency separation between rigid body mode and flexible modes of flexible aircraft are closer, and it introduces higher flexibility effects on aircraft dynamics. In such a case, the design of a flight control law is not valid based on the assumption that aircraft dynamics are rigid body models. Moreover, an integrated aircraft model having a rigid body and elastic body modes contain a large number of states. Therefore, we have designed an optimal flight control law from a reduced-order model and realized with a flexible aircraft represented by a full order model. For this, the simplified model of the flexible aircraft is derived using the Chidambara technique, and Luenberger observer is applied to estimating the elastic states of a simplified model from the aircraft measurements.

IFAC Proceedings Volumes, 1987

For a flexible structure to meet its mission objectives successfully, a close inter3ction between structural analysis and control group is needed at both the mo~elling and control design phases. For such an inter3ction to be beneficial, an integr3tion of suitable methods from both the groups is essential. The finite element-transfer matrix (FETM) approach and the method of decentralized control using optimal control theory are ideally suite~ for this integration: the FETM mehto~ has been developed by structural analysts to overcome the 'dimension-problem', which problem is also encountered by control engineers; the decentralized control strategy is being adopted by control engineers to control large flexible structures. This paper presents the development of this method and demonstrates its applicability to the control of distributed parameter systems. $pecifically, as an illustration, the control of a simply-supported beam is investigated.

Science in China Series F: Information Sciences, 2001

Appropriate modeling for a controlled plant has been a remarkable problem in the control field. A new modeling theory, i.e. characteristic modeling, is roundly demonstrated. It is deduced in detail that a general linear constant high-order system can be equivalently described with a two-order time-varying difference equation. The application of the characteristic modeling method to the control of flexible structure is also introduced. Especially, as an example, the Hubble Space Telescope is used to illustrate the application of the characteristic modeling and adaptive control method proposed in this paper.

Shock and Vibration, 2007

We propose a two-step strategy for the design of passive controllers for the simultaneous confinement and suppression of vibrations (SCSV) in mechanical structures. Once the sensitive and insensitive elements of these structures are identified, the first design step synthesizes an active control law, which is referred to as the reference control law (RCL), for the SCSV. We show that the problem of SCSV can be formulated as an LQR-optimal control problem through which the maximum amplitudes, associated with the control input and the displacements of the sensitive and insensitive parts, can be regulated. In the second design step, a transformation technique that yields an equivalent passive controller is used. Such a technique uses the square root of sum of squares method to approximate an equivalent passive controller while maximizing the effects of springs and dampers characterizing passive elements that are added to the original structure. The viability of the proposed control design is illustrated using a three-DOF mechanical system subject to an excitation. It is assumed that all of the masses are sensitive to the excitation, and thus the vibratory energy must be confined in the added passive elements (insensitive parts). We show that the vibration amplitudes associated with the sensitive masses are attenuated at fast rate at the expense of slowing down the convergence of the passive elements to their steady states. It is also demonstrated that a combination of the RCL and the equivalent passive control strategy leads to similar structural performance.

Procedia Engineering, 2012

This work addresses the solution to the problem of active vibration suppression of a cantilever beam using piezoelectric actuation. For this purpose, we are taking advantage of the effectiveness of the positive position feedback control strategy (PPF) in order to control first mode vibrations of the analyzed beam. This control technique is well-known in the literature as a modal control method for vibration attenuation. The PPF controller accomplishes its best performance if tuned properly to the characteristics of the structure to be controlled. According to this we are going to realize the modal analysis of the cantilever beam utilizing the finite element method in Ansys to determine the structural frequency corresponding to the first mode, which is used as PPF controller frequency. On the other hand, we shall obtain the state-space representation of the cantilever beam using the subspace identification method in frequency domain applying the fast fourier transformation (FFT). Furthermore, we will simulate the discrete-time PPF controller using Matlab/Simulink. Lastly, the simulink designed discrete-time PPF controller will be tested using an xPC Target real-time system.

2002

For spacecraft with large flexible antennas, andor flexible support structures, suppressing vibrations caused by on-orbit operational disturbances (e.g., antenna slew maneuvers and thruster firings) is a challenging problem. In the past several years, advances in smart structure technologies have made their use in real-time dynamic control cif a structure possible. This paper discusses analytical investigations that are focused on the development of improved vibration suppression techniques for flexible spacecraft structures using smart structure actuators and sensors. In general, active control of large flexible structures can be used to improve performance, e.g., shape fidelity, line-ofsight pointing accuracy, and vibration and disturbance suppression. Large-scale models of such structures (e.g., finite element models) are appropriate for dynamic simulation but cannot be used as a basis for control algorithms, whch must be implemented via computer in real-time. Therefore, control algorithms are often based on Reduced-Order Models (ROM) of the structure dynamics. Whenever such a controller operates in closed-loop with the actual structure, unwanted Controller-Structure Interaction (CSI) occurs due tci un-modeled dynamics. CSI can cause performance degradation and even instability. These instabilities can easily be relieved by the use of low-order Residual Mode Fih'ers (RMF). These filters can be added on after the original ROM controller has been designed, and they produce very little degradation of designed performance while yielding an acceptable stability margin for closed-loop operation. The research presented in this paper integrates smart structure control technologies with the ROM-RMF control technique for aciive vibration control of a flexible spacecraft structure. This smart structure control technique is applied to a model of the U.S. Naval Postgraduate School's Flexible Spacecraft Simulator (FSS). The FSS simulates motion about the pitch axis of a spacecraft, and is comprised of a rigid central body and a reflector supported by a two-link flexible antenna support structure. The flexible arm representing the antenna support structure has two sets of piezoclxamic sensors and actuators, which are used for active vibration control. The ROM-RMF control technique, used in conjunction with optimal control laws, is

2010

Abstract The problem of active reduction of the structural vibrations induced by the sloshing of large masses of fuel inside partly full tank is considered. The proposed study focuses on an experimental device mimicking an aircraft wing made of an aluminum rectangular plate equipped with piezoelectric patches at the clamped end and with a cylindrical tip-tank, more or less filled with liquid.

A mechanical system containing compliant element is investigated. Such an element can be, for example, a compliant platform where the operated object (plant) is installed or an elastic gear that connects a motor with this movable object. The control parameter (force or torque) is bounded in magnitude. Only the first (lowest) resonance frequency is taken into account. Thus the system under consideration has two degrees of freedom and one control input. A double zero eigenvalue and two complex eigenvalues are in the linear mathematical model of this system. Control laws to steer the plant from the given initial state to the given final state in finite time are designed. These controls are divided into intervals on which it varies linearly depending on time or is constant. The time intervals where the control varies are equal to the period of the natural vibrations of the system. If there is no damping, this makes it possible to completely avoid vibrations on the time intervals where the control is constant including the time when the control signal becomes zero (identically). Another way to avoid the vibrations is to put the total time of the transient process equal to a multiple of the doubled period of the natural vibrations.