Intelligent Truss Structures Research Articles

Integral terminal sliding-mode robust vibration control of large space intelligent truss structures using a disturbance observer

This study aims to develop an advanced integral terminal sliding-mode robust control method using a disturbance observer (DO) to suppress the forced vibration of a large space intelligent truss structure (LSITS). First, the dynamics of the electromechanical coupling of the piezoelectric stack actuator and the LSITS, based on finite element and Lagrangian methods, are established. Subsequently, to constrict the vibration of the structure, a novel integral terminal sliding-mode control (ITSMC) law for the DO is used to estimate the parameter perturbation of the LSITS based on a continuous external disturbance. Simulation results show that, under a forced vibration and compared with the ITSMC system without a DO, the displacement amplitude of the ITSMC system with the DO is effectively reduced. In the case where the model parameters of the LSITS deviate by ±50%, and an unknown continuous external disturbance exists, the control system with the DO can adequately attenuate the structural vibration and realize robust control. Concurrently, the voltage of the employed piezoelectric stack actuator is reduced, and voltage jitter is alleviated.

Optimal Placement of Controls for Truss Structures in Space

The authors propose a genetic algorithm-based approach to finding the optimal placement of actuators and sensors, which is critical for controlling intelligent truss structures in space.

Placement optimization of actuator and sensor and decentralized adaptive fuzzy vibration control for large space intelligent truss structure

Large space truss structure is widely used in spacecrafts. The vibration of this kind of structure will cause some serious problems. For instance, it will disturb the work of the payloads which are supported on the truss, even worse, it will deactivate the spacecrafts. Therefore, it is highly in need of executing vibration control for large space truss structure. Large space intelligent truss system (LSITS) is not a normal truss structure but a complex truss system consisting of common rods and active rods, and there are at least one actuator and one sensor in each active rod. One of the key points in the vibration control for LSITS is the location assignment of actuators and sensors. The positions of actuators and sensors will directly determine the properties of the control system, such as stability, controllability, observability, etc. In this paper, placement optimization of actuators and sensors (POAS) and decentralized adaptive fuzzy control methods are presented to solve the vibration control problem. The electro-mechanical coupled equations of the active rod are established, and the optimization criterion which does not depend upon control methods is proposed. The optimal positions of actuators and sensors in LSITS are obtained by using genetic algorithm (GA). Furthermore, the decentralized adaptive fuzzy vibration controller is designed to control LSITS. The LSITS dynamic equations with considering those remaining modes are derived. The adaptive fuzzy control scheme is improved via sliding control method. One T-typed truss structure is taken as an example and a demonstration experiment is carried out. The experimental results show that the GA is reliable and valid for placement optimization of actuators and sensors, and the adaptive fuzzy controller can effectively suppress the vibration of LSITS without control spillovers and observation spillovers.

Active Disturbances Rejection Vibration Controller Using Extended State Observer and Nonlinear State Error Feedback

Intelligent truss structures, as a new kind of integrated control-structures, have the adaptive geometry and physics characteristics, but these structures also have the complex dynamic characteristics, such as large flexibility, small structure damping, closely low order modes, high degree of mode coupling, uncertainties, and coupling, which brings a great challenge to active vibration control of intelligent truss structures. Therefore, it is studied how to design the model-independent active disturbances rejection vibration controller (ADRVC), based on the extended state observer (ESO) and the nonlinear state error feedback control law (NLSEF). The real-time dynamic linearization of the uncertain nonlinear system is implemented by disturbance estimation via ESO and disturbance compensation via the control law. A NLSEF is designed to control the linear integrator-cascaded type plant. The ADRVC is used for the vibration control of an 83-bar space intelligent truss structure with uncertain-but-bounded parameters. The simulation results demonstrate the ADRVC has good adaptability and robustness to external disturbance and unknown variation in plant parameters.

Stepwise Optimal Design of Active Disturbances Rejection Vibration Controller for Intelligent Truss Structure Based on Adaptive Genetic Algorithm

Stepwise Optimal Design of Active Disturbances Rejection Vibration Controller for Intelligent Truss Structure Based on Adaptive Genetic Algorithm

Control–structural design optimization for vibration of piezoelectric intelligent truss structures

Based on the design sensitivity analysis for structural dynamics in time domain, an integrated control–structural design optimization method is proposed to the vibration control of piezoelectric intelligent truss structure. In this investigation, the objective function and constraint functions include not only the conventional design indexes of structure but also the vibration control indexes and the feedback control variables. The structural design variables are optimized simultaneously with the vibration control system. The sensitivity relations for the control–structure optimization model are derived by using a new method, and the sequential linear programming algorithm is used to solve this kind of optimization problem. The numerical examples given in the paper demonstrate the effectiveness of methods and the program.

Immune genetic algorithm used to integrated optimal design of active vibration control system for piezoelectric intelligent truss structures

The integrated optimization design of active vibration control system for intelligent truss structures, including the feedback gains and the positions of active/passive members, is formulated. A performance function is initially developed, based on the maxi-mization of energy dissipation due to active vibration control action. A novel constrained algorithm is presented to solve the kind of optimization problem with the discrete and continuous design variables. Then, according to the characteristics of the optimal problem, a new problem-specific encoding scheme, some special immune genetic operators and a novel antibody similarity computation method are proposed and discussed. A numerical example of a 16-bar planar intelligent truss structure is presented to demonstrate the rationality and validity of this methodology, and some useful conclusions are obtained.

An Interval Parameter Perturbation Method for Predicting the Natural Frequency Bounds of Intelligent Truss Structures with Uncertain-But-Bounded Parameters

The upper and lower bound estimation of natural frequencies for intelligent truss structure with uncertain-but-bounded parameters is studied in this paper. Firstly, following the finite element method, the expressions of the interval stiffness and interval mass matrix of piezoelectric intelligent truss structures are derived directly from the interval parameters. Then, based on the matrix perturbation and interval extension theory, an interval parameter perturbation method is proposed for solving the upper and lower bound of natural frequencies. Finally, a 16-bar planar intelligent truss structure is used as an example to illustrate the applicability and validity of the presented method, and some useful conclusions are obtained.

Integrated Optimization Design of Active Vibration Control System for Piezoelectric Intelligent Truss Structures Using Immune Algorithm

Article Integrated Optimization Design of Active Vibration Control System for Piezoelectric Intelligent Truss Structures Using Immune Algorithm was published on December 1, 2007 in the journal International Journal of Nonlinear Sciences and Numerical Simulation (volume 8, issue 4).

Design optimization and sensitivity analysis on buckling stability of piezoelectric truss structures

The design optimization of buckling behavior is studied for piezoelectric intelligent truss structures. First, on the basis of mechanical–electric coupling equation and considering electric load and mechanical loads together, the finite element model of piezoelectric trusses has been built up. Then, the computational formula has been derived for the design sensitivities of critical buckling load factor of the structure with respect to size and shape design variables. The electric voltage is taken as a new kind of design variable and the calculation method of critical load buckling factor with respect to the electric voltage variables is proposed. Particularly, the variations of the loads and pre-buckling inner forces with design variables have been accounted for. Finally, the sequential linear programming algorithm is employed to solve the optimization problem, and a new method of controlling structural buckling stability by optimizing the voltages of piezoelectric active bars is proposed. Numerical examples given in the paper have demonstrated the effectiveness of the methods presented.

Stochastically optimal active control of a smart truss structure under stationary random excitation

Optimization of the placement and feedback gains of an active bar in a closed-loop control system for random intelligent truss structures under stationary random excitation are studied in this paper. Based on maximization of dissipation energy due to the control action, a mathematical model with reliability constraints on the mean square value of the structural dynamic displacement and stress response is developed. The randomness of the physical parameters corresponding to the structural materials, geometric dimensions and structural damping are included in the analysis, and the applied forces are considered as stationary random excitation. The numerical characteristic of the stationary random responses of a stochastic smart structure is developed. Numerical examples of stochastic truss structures are presented to demonstrate the rationality and validity of the active control model, and some useful conclusions are obtained.

Optimization of active vibration control for random intelligent truss structures under non-stationary random excitation

The optimization of active bars` placement and feedback gains of closed loop control system for random intelligent truss structures under non-stationary random excitation is presented. Firstly, the optimal mathematical model with the reliability constraints on the mean square value of structural dynamic displacement and stress response are built based on the maximization of dissipation energy due to control action. In which not only the randomness of the physics parameters of structural materials, geometric dimensions and structural damping are considered simultaneously, but also the applied force are considered as non-stationary random excitation. Then, the numerical characteristics of the stationary random responses of random intelligent structure are developed. Finally, the rationality and validity of the presented model are demonstrated by an engineering example and some useful conclusions are obtained.

Dynamic response analysis of closed-loop control system for random intelligent truss structure under random forces

Considering the randomness of structural damping, physical parameters of structural materials, geometric dimensions of active bars and passive bars, applied loads and control forces simultaneously, the problems of dynamic response analysis of closed-loop control system based on probability for the random intelligent truss structures are studied in this paper. The computational expressions of numerical characteristics of structural dynamic response of closed-loop control system are derived by means of the mode superposition method. Through the engineering examples, the influences of the randomness of them on structural dynamic response are inspected and some significant conclusions are obtained.

Dynamic response analysis of closed loop control system for intelligent truss structures based on probability

The dynamic response analysis of closed loop control system based on probability for the intelligent truss structures with random parameters is presented. The expressions of numerical characteristics of structural dynamic response of closed loop control system are derived by means of the mode superposition method, in which the randomness of physical parameters of structural materials, geometric dimensions of active bars and passive bars, applied loads and control forces are considered simultaneously. The influences of the randomness of them on structural dynamic response are inspected by several engineering examples and some significant conclusions are obtained.

Optimal placement of active bars in active vibration control for piezoelectric intelligent truss structures with random parameters

Considering the randomness of physical parameters of structural material, geometric dimensions of active bars and passive bars, applied loads and control forces simultaneously, the optimization of active bar’s placement and feedback gains for the vibration control of intelligent truss structures are studied in this paper. Firstly, the performance function is developed based on the maximization of dissipation energy due to control action. Then, the optimal mathematical model with the reliability constraints on dynamic stress and displacement response is built. The numerical feature of dynamic response based on probability of intelligent structure is developed. Finally, a planar intelligent truss structure is used as an example to demonstrate the rationality and validity of the presented model and approach in structural active vibration control.

Control of Intelligent Adaptive Structures. 2nd Report. Hardware Experiments of Optimal Trajectory Control.

This paper is concerned with an experimental study on optimal trajectory control of a variable geometry truss, which is one of the intelligent truss structures composed of a truss-type mechanism. The intelligent structure considered here is assumed to have many sensors and actuators. Thus, the intelligent structure utilized as a manipulator arm has high redundancy. In the first report, two efficient methods were proposed for manipulation trajectory control under the relaxed conditions of optimality, and the validity of the proposed methods is demonstrated through numerical simulations. In this study, the proposed methods are applied to a hardware experiment. The experimental results confirm the validity of the proposed control methods. Also, it is shown that an optical sensor feedback is effective for the precise control of the position and orientation of the end tip of the trus along the trajectory, even when these controllers have some modeling errors.

The Optimum Adaptive Geometries of Intelligent Truss Structures for Dynamic Loading Conditions.

This paper is concerned with the optimal adaptive geometries of intelligent truss structures under dynamical loadings. The optimal geometry is attained by changing the lengths of some active members installed in the structure to obtain the maximum structural strength. Dynamical analysis by Newmark β method is introduced into the geometry optimization problem. The intelligent truss structure is assumed to be either fixed at the base or in a floating state. From the numerical examples, the following conclusions are drawn : (1) For an impact load, the largest stress exists in the place which is directly subjected to the impact and the geometry of the structure cannot improve the structural strength, (2) For a load acting for a long time, there exists an optimal geometry which provides a much higher structural strength than other geometries of the structure.

Control of Intelligent Adaptive Structures. 1st Report: Optimal Trajectory Control.

This paper is concerned with the optimal trajectory control of an intelligent truss structure composed of a truss-type mechanism. The intelligent adaptive structure can change its geometric configuration as well as physical properties in order to meet mission requirements. Many variable-length members are incorporated in the intelligent adaptive structure, resulting in a highly redundant system. Thus, the intelligent structure which is used as a manipulator arm can utilize the redundancy for the optimization of trajectory control. Efficient control methods are proposed for the trajectory control optimizing a performance index by using the redundancy. The validity of the proposed methods is demonstrated through numerical simulations. An adequate performance index enables the intelligent adaptive structure to be an appropriate configuration.

Optimum Adaptation of Intelligent Truss Structures

Intelligent structures that can actively change their geometric configura tions, as well as their mechanical properties, are developed to meet various space mission requirements. In this paper, optimal shapes of an intelligent truss structure under a variety of external loading conditions are investigated. The intelligent truss to be considered is a type of statically determinate truss structure that changes its configuration by lengthening or shortening some active member's lengths. For this intelligent truss structure, an op timization problem is defined: when the load is applied in a specified direction, an attempt is made to find an optimal shape of adaptation to attain its maximum structural strength. With the geometric design variables corresponding to the lengths of the active members adopted, the optimization is carried out by using a Multiplier Method. The numerical results indicate that the intelligent truss structure can provide much higher structural strength than a fixed truss structure by taking the optimal adaptive shape.

Optimal adaptive geometry of intelligent truss structures.

An intelligent structure concept which can freely change its geometric configuration as well as its physical properties is developed to meet various space mission requirements. In this paper, the optimal geometry of an intelligent truss structure with some of its member's lengths actively controlled is investigated. Structural analysis is performed by means of a matrix method and the optimization of the truss geometry is carried out by using the multiplier method. It is shown that for a load applied from a given direction, the optimal truss geometry obtained by adjusting the lengths of the active members provides a higher structural strength than a fixed truss structure.