Simultaneous structure/control design synthesis for aero-servo-elastic system

It is generally accepted that active control systems provide better structural performance when compared to their passive counterparts. On the other hand, the design of active control systems based on linear control theory is highly dependent on the structural properties. For this reason, their performance is expected to be affected more severely by variations in structural properties compared to those of passive systems. These variations can occur due to nonlinear structural behavior, or even before that due to uncertainties in the estimation of these properties and in numerical modeling. The present work is an investigation of the dependency of various control systems used for supplemental energy dissipation to the changes in structural properties. For this purpose, the performance degradations of most common control systems are studied for structures entering their nonlinear response range. The considered control systems include active control using linear quadratic regulator algorithm and passive control using viscous fluid dampers and yielding devices. These control systems are optimized separately for linear and nonlinear structures by minimizing performance indices based on inter-story drift and absolute acceleration response. It is shown that among these control systems, viscous dampers are affected the least by the alteration of structural properties, which may further support their utilization contrary to the more costly active control systems. It is also shown that the amount of performance degradation depends on the selected structural performance index, and more importantly, the severity of the earthquake excitation.

Macro fiber composite (MFC) has been widely investigated in the active vibration control. Yet, the actuation performance of MFC is a function of temperature. For the active vibration control system using MFC based on the linear piezoelectric equation, if the actuation parameters of MFC are variable, it is easy to cause insufficient control force or control spillover, which degrades the performance of control system. Therefore, an adaptive gain adjustment approach for the active vibration control system is developed, which ensures that the active control system can maintain the expected performance of vibration suppression under the time-varying ambient temperatures. The variation of actuation performance of MFC with temperature is measured by the experiment. The polynomial fitting method is utilized to obtain the functional relationship between the regulator parameters and ambient temperature. The performance of the proposed adaptive gain regulator is verified by the experiment in the temperature environment chamber. In the experiment, a scaled vertical tail model attaching the MFC actuator is as an example, and the fractional order positive position feedback control system is as a representative of the control system without temperature adaptability. When the temperature is −60°C, compared with the control system without regulator, the reduction ratio of response RMS of the control system with adaptive gain regulator is increased by 17.26%.The results indicate that the proposed adaptive gain regulator can avoid the adverse influence of the time.varying ambient temperature on the performance of the control system.

There have been many reports on the design of active vibration control systems. Most of them have optimized control systems based on the LQ optimal regulator or H∞ control theory. However, there are no answers to the problem whether given passive parameters of plants (e. g., spring constant on damping coefficient) are 'suitable' for the designed controller. In this paper, we consider structure and control simultaneous optimization for an active vibration control system. To provide solutions, several methods have been proposed which are based on tuning the design paramethers existing in the structure and controller. Most of the control laws are those of standard LQ optimal requlators which require full states measurements and estimate performance of a closed-loop control systems in the time domain. From the viewpoint of active vibration control, it is natural to discuss the performance of the control system in the frequency domain. Therefore, we adopt the frequency shaped LQG control law in simultaneous optimization design, which enables output feedback control and frequency shaping.

Digital control of a continuoiis-time system implies discretization in time of the system. The discretization is likely to bring about changes in the dynamic characteristics of the continuous-time system. Two approaches to the design of a digital control system can be considered: 1) discretization of a previously designed continuoustime control system and 2) direct design in the discrete-time domain. The difference between these two approaches and their effects on a closed-loop control system employing a Luenberger-type observer is demonstrated. The first approach consists of simulating a continuous-tim e control system on a digital computer. Because the possibility exists that a given set of parameters of the continuous-time system, such as gains and observer poles, will produce a change in the dynamic characteristics of the system during digital simulation, the question is how large the sampling time can be without affecting adversely the discrete simulation. An example of an unstable digital simulation of a closed-loop control system employing a deterministic observer that is stable in continuous-ti me is presented. The second approach inherently guards against changes in the dynamic characteristics that may be caused by discretization. The two approaches are compared by using a second-order dynamic system.

We formulate a simultaneous optimal design problem of structural and control systems including discrete design variables. The problem generally becomes nonlinear and/or nondifferentiable optimization problem whose design variables are continuous or discrete. Since the nondifferentiability of the problem, we can not apply standard descent-based nonlinear optimization techniques such as steepest descent method, Quasi-Newton method etc.. Even if a subproblem, which is generated by fixing discrete design variables of the original problem, is corresponding to BMI(Bilinear Matrix Inequality), it is difficult to obtain the(global)optimal solution efficiently because of NP hardness nature of BMI. In this paper, we apply SA(Simulated Annealing)which is known as the one of the probabilistic optimization method. We present a new controller parametrization of the controller based on Youla parametrization. This parametrization does not need numerical computational procedure, such as solving Riccati equation or LMI to obtain stabilizing controller. Moreover, the class of the controller is at least larger than that of DVFB control(which is also a stabilizing control law without numerical computational procedure). We give a design example and show the effectiveness of the proposed design method.

An investigation is made of the possible application of an active mass damper control system to tall buildings excited by strong wind turbulence. The effectiveness of active control system, as measured by the reduction of the coupled lateral‐torsional motions of tall buildings is studied. The wind turbulence is modeled as a stochastic process that is stationary in time but non‐homogeneous in space. The problem is formulated using the transfer matrices approach, and a closed‐loop control law. The random vibration analysis is carried out to determine the statistics of the building responses, the required active control forces, and mass damper displacements. The method of Monte‐Carlo simulation is also employed to demonstrate the building response behavior with or without an active control system. A numerical example of a forty‐story building under strong wind excitations is given to illustrate the significant reduction of the building acceleration response by use of an active mass damper control system.

The design of space systems is a complex and multidisciplinary process with multiple conflicting objectives, large number of design variables, and constraints that limits application of the existing multidisciplinary design optimization architectures to this class of design problems. This paper presents an enhanced multidisciplinary design optimization architecture to concurrent holistic design optimization of a satellite system. The proposed multidisciplinary design optimization architecture extends concepts of multidiscipline feasible and bi-level integrated system synthesis into a unified architecture using metamodels. The proposed architecture was evaluated and compared with the existing multidisciplinary design optimization architectures that include all-at-once, bi-level integrated system synthesis, and multidisciplinary design optimization using a remote sensing small satellite in low earth orbit. The satellite design optimization problem deals with the minimization of the total mass of the satellite, involving disciplines of mission analysis, payload, structures, attitude determination and control, communication, command and data handling, power and thermal. The computational performance and accuracy of the proposed architecture were compared with multidisciplinary design optimization benchmark problems. Then the proposed architecture is successfully applied to the satellite system design problem. The results obtained show that metamodel-based bi-level integrated system synthesis-multidisciplinary design optimization architecture presented in this paper provides an effective way of solving large-scale design problems.

: A general longitudinal feedback control system containing pitch, pitch rate, depth, and depth rate feedback is described. The Laplace domain transfer functions for each feedback loop are developed. A computer analysis program using the root locus technique is developed for aiding in the design of the control system. An illustrative example design problem is included.

This work describes a range of issues relating to the implementation of active control for noise and vibration problems. It is important in the commercialization of this technology to consider these and many other factors relating to design of these systems. Many of the concepts required for efficient implementation have not been considered and it is important to begin giving design consideration to these aspects. A design technique based upon the eigenbehavior of feedforward controlled systems is developed and applied to control radiation from structures. Integration of the control system with the physical system dynamics allows the eigenproperties to be defined to meet a prescribed design criteria. Here the technique is demonstrated to implement a structural system that inefficiently couples vibration energy to acoustic energy. In addition, an approach to integrate “knowledge” about actuator configurations into an active control system that reduces spillover effects into structural vibrations is demonstrated. This approach has the advantages that no additional hardware is required while also reducing the order of the control system in terms of degrees of freedom. Finally, some design trade-offs between the passive material properties of an active trim panel and control system performance are examined. Improved performance can be attained but at the cost of additional weight.

In this paper, the characteristics of forces in active control systems connected to adjacent levels of a building are analyzed. The following characteristics are observed: (1) active control can provide significantly superior supplemental damping to a building, but causes a small frequency shift; (2) the linear quadratic regulator (LQR)-based control force is composed of an elastic restoring force component and a damping force component, where the damping force is almost identical to the total control force, however, the elastic restoring force is very small; and (3) the active control forces prevent motion most of the time during the entire control process. These three characteristics imply that active control systems connected to adjacent levels of a building behave like passive damping devices with adjustable parameters, namely damping characteristics in an active control, which is the mechanism used by semi-active control devices to reach similar performance as active control systems. Two indices are defined to quantify the damping characteristics of control forces in active control systems. These two indices can also be used to quantify the capacity of semi-active control to achieve the performance of active control. Based on the above observations, two principles are founded for optimization of parameters of semi-active control devices and passive dampers. The first is that the maximum output force of a semi-active or passive device to be designed is identical to an active device, called “design principle”. The other is the response equivalent principle, which states that the response of a building with semi-active or passive devices is the same as with active devices when the same maximum output force is applied. The design procedure for semi-active control devices and passive dampers is described in detail. Finally, numerical simulations of two benchmark problems is conducted to demonstrate the damping characteristics of active control and investigate the capacity of semi-active control to achieve the same performance as active control.

Shutting the window is usually the last resort in mitigating environmental noise, at the expense of natural ventilation. We describe an active sound control system fitted onto the opening of the domestic window that attenuates the incident sound, achieving a global reduction in the room interior while maintaining natural ventilation. The incident sound is actively attenuated by an array of control modules (a small loudspeaker) distributed optimally across the aperture. A single reference microphone provides advance information for the controller to compute the anti-noise signal input to the loudspeakers in real-time. A numerical analysis revealed that the maximum active attenuation potential outperforms the perfect acoustic insulation provided by a fully shut single-glazed window in ideal conditions. To determine the real-world performance of such an active control system, an experimental system is realized in the aperture of a full-sized window installed on a mockup room. Up to 10-dB reduction in energy-averaged sound pressure level was achieved by the active control system in the presence of a recorded real-world broadband noise. However, attenuation in the low-frequency range and its maximum power output is limited by the size of the loudspeakers.

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Context. The question of increasing the productivity of technological processes of extraction, processing and preparation of raw materials, improving product quality, reducing energy consumption, as well as creating safe working conditions during technological processes and preventing accidents is always quite relevant and requires the implementation of modern control and management systems. For the effective operation of such systems, it is important to pre-process and filter the data received from the sensors for monitoring the grinding processes and the explosive status of objects. One of the possible ways to increase the informativeness of data is the use of singular spectral analysis.Objective. Increasing the efficiency of technological process control systems and the reliability of explosive control systems of coal mines and oil and fuel complex facilities by processing and pre-filtering data received from sensors for monitoring grinding processes and the state of facilities.Method. To analyze the output signals of sensors used in control and management systems, the method of singular spectral analysis is used, which allows revealing hidden structures and regularities in time series by pre-filtering and data processing of acoustic, thermocatalytic, and semiconductor sensors.Results. A new approach to the management of technological processes of grinding raw materials in jet mills and control of the explosiveness of coal mines and objects of the oil and fuel complex is proposed, based on methods that allow to speed up the processing speed of sensor output data and improve the quality of information. It is shown that one of the promising methods that can be used for the pre-processing of time series of output data of sensors in control and control systems is the method of singular spectral analysis, the use of which allows filtering data, revealing hidden structures and regularities, and forecasting changes based on the analysis of previous information , identify anomalies and unusual situations, make more informed decisions and improve the processes of managing technological processes.Conclusions. The conducted experiments have confirmed the proposed software operability and allow recommending it for use in advancing both theoretical and practical aspects of process control systems through an enhanced singular spectral analysis (SSA) method for time series processing. This improved approach has been successfully demonstrated in real-world applications, including grinding processes in jet mills and explosion monitoring in coal mines and oil and fuel facilities. The implementation demonstrates a significant increase in data processing speed and information quality, which makes it particularly valuable for use in safety-critical industrial facilities.

Multichannel active noise control (ANC) systems have been investigated to reduce outdoor low-frequency noise, such as power transformer noise and traffic noise. However, in outdoor environments, wind noise is inevitable and significantly degrades the noise reduction performance of active control systems. Despite broad adoption in windy environments, porous microphone windscreens cannot eliminate low-frequency wind noise in microphones, especially when the wind speed is high. Assuming wind noise is additive and uncorrelated with the primary noise to be controlled, this paper analyses how the wind noise detected by the reference microphone impacts the control filters and the residual noise of a multichannel ANC system based on the multichannel filtered-reference least mean squares algorithm (MFxLMS). By extending our recent research on wind noise suppression in single-channel active noise control systems [Y. Chu, et al., J. Acoust. Soc. Am. 152(6), 3340–3345 (2022)], a modified MFxLMS algorithm based on a new cost function is proposed. Simulations with real-recorded wind noise are performed to verify the theoretical analysis.

In a central receiver solar power plant, heliostats are arranged with respect to the central receiver so as to reflect the rays from the sun onto the power tower with high precision by tracking the sun in both the azimuth and elevation directions. The master control system of a solar power plant consists of different levels. The first level is local control; it takes care of the positioning of the heliostats when the aiming point and the time are given to the system, and informs upper level about the status of the heliostats field. The second logic level makes some important dispatch calculations of heliostats field. The most popular linear two-axis local driving system of heliostat consists of two linear driving actuators, the driving mechanism with rotary joints, and the controller. Traditional methods for heliostat design are often based on a sequential approach in which the mechanical structure is designed first and then the control system is advised. In order to reach the optimal design of heliostats, an integrated design approach that concurrently considers the interactions between the mechanical and control subsystems is necessary. In this article, an integrated design methodology of heliostat drive system is presented. The methodology is based on modeling and simulation. The dynamic models that describe the behavior of the mechanical and control components are presented. These models involve mechanical and control design variables such as the motor parameters, power screw (including back lash), heliostat mass, load forces, and wind forces. Matlab, Solidwork, and Simulink are chosen to apply PID tracking control to heliostats, due to the ability to arbitrarily model complex mechanical systems, directly import properly constructed, third-party 3D CAD models, simulate integrated control, handle a variety of robotics nomenclature, and other features. The present methodology is employed for integrated design of a single facet small size heliostat with mirror area of 3 m2.The methods described in this article also show a way to rapidly simulate novel and complex heliostat geometries. Analysis of the heliostat drive system performance and dynamic characteristics according to mechanical and control design variables is conducted for the purpose of control system design and performance optimization. The drive system performance is evaluated in terms of positioning tracking errors, system response, and control system behavior. It is shown that the mechanical characteristics of the ball power screw actuator such as ball-screw diameter, lead, overall flexibility, stiffness, backlash, and inertia significantly influence the performance of drive system.