Degrees Of Freedom Control System Research Articles

Pseudo‐dynamic hybrid simulations of steel eccentrically braced frames equipped with cast steel replaceable modular yielding links

AbstractPrevious studies have underlined the importance of establishing a database of high‐fidelity benchmark experimental test results under random loading histories such as earthquake excitations for both existing structural systems as well as newly proposed ones. Such experimental results are useful for understanding the limitations of previously developed numerical models, proposing new numerical models for more recently developed structural systems, better assessing the ultra‐low cycle fatigue (ULCF) life of energy dissipative components, and improving the loading protocols used for element assessments or developments of numerical model. This paper presents experimental results from pseudo‐dynamic hybrid simulations on steel eccentrically braced frames (EBF) equipped with novel cast steel replaceable modular yielding links. The first set of experiments are carried out on a four‐story EBF, with the first‐floor yielding link physically tested in the laboratory. The second set of experiments are performed on a two‐story EBF where the second‐floor link is physically tested in the laboratory, while considering axial loads due to the imbalanced distribution of the seismic weight in the building. Each building structure is subjected to three Maximum Credible Event (MCE) level earthquakes. A framework for performing hybrid simulations on EBFs is proposed where the response of the yielding link is physically captured in a single degree of freedom control system, with or without axial loads. A substructuring strategy is proposed in conjunction with a modeling approach in the integration module. The results confirm the effectiveness of the hybrid simulation framework, which can be adopted in similar studies. Two numerical models are proposed for capturing the response of cast steel links using a simplified and a more advanced approach. The models are first calibrated using incremental reversed‐cyclic experimental test results, and then refined using the hybrid simulation test results. The effects of this calibration improvement are quantified through critically comparing the response prediction for different response parameters before and after improving the calibration with the experimental results. The numerical model which captures the physical mechanism of the cast steel links provides a more accurate response prediction compared to the simplified numerical model using a phenomenological truss with calibrated force‐deformation. The remaining ULCF life of the tested yielding links is experimentally investigated after having sustained three MCE level earthquakes, which indicates a large reserve ductility capacity which is more than twice the required plastic rotation capacity for cast steel links after seismic events.

Basic study on two degrees of freedom control system for in-car crib with joint application of regular and inverted pendulum mechanisms

Basic study on two degrees of freedom control system for in-car crib with joint application of regular and inverted pendulum mechanisms

Self-tuning cross-coupled two degree-of-freedom PID control for position synchronization of dual linear motors

• Operational principleand dynamic analysisof two kinds of dual linear motors driven stages are discussed. • Aself-tuning cross-coupled two-DOF PIDcontrollerisproposed with synchronous performance and self-tuning mechanism. • An improved artificial bee colonyalgorithm is proposed to tune the control parameters online. • Simulationsand experimentationsof five differentcontrollers are examined and compared. The objective of this study is to propose a self-tuning cross-coupled two degree-of-freedom (DOF) proportional-integral-derivative (PID) control strategy for position synchronization of a dual linear motors (DLMs) driven stage. First, independent one DOF PID (I1PID) control and cross-coupled 1PID (C1PID) control are designed to control the DLMs. Subsequently, independent two DOF PID (I2PID) control and cross-coupled 2PID control (C2PID) are built to further examine the enhanced control performances of the two DOF control systems; the structure of the C2PID control provides improvement over the C1PID in control performance. Nevertheless, it is arduous to tune three main parameters including the proportional gain, the integral time, and the derivative time as well as two compensation parameters including the proportional and the derivative constants. In this regard, a self-tuning C2PID (SC2PID) control is developed in which all the control parameters are dynamically and concurrently optimized through an improved artificial bee colony algorithm. Numerical simulations and experimental results indicate that the proposed SC2PID control exhibits optimal tracking performance with lowest synchronous error when compared with other control schemes.

Design of a Data-Oriented PID controller for a Two Degree of Freedom Control System

Virtual Reference Feedback Tuning (VRFT) and Fictitious Reference Iterative Tuning (FRIT) are the data-oriented tuning schemes for directly designing feedback controllers. In these schemes, controller parameters are tuned to achieve the desired response without any system identifications. Furthermore, these schemes have been extended to the two-degree of freedom (2DOF) control systems in recent years. The conventional design schemes of 2DOF controllers are a two-step tuning method. The first step is to design a feedback controller to satisfy the desired disturbance response. The second step is to tune the feed-forward controller parameters to achieve the desired reference response. Consider these methods are complicated, this paper provides a one-step tuning scheme for a 2DOF control system based on data-oriented method. According to the proposed scheme, the reference of the complementary sensitivity function is introduced, and the least squares method can be applied to calculate the optimal controller parameters. Finally, the effectiveness of the proposed scheme is verified by using a numerical example.

Spiral Servo Writing in Hard Disk Drives Using Iterative Learning Based Tracking Control

AbstractThe servo control in a hard disk drive (HDD) system relies heavily on the position information obtained from the servo sectors. As the tracks-per-inch (TPI) gets higher and higher in HDDs, writing of servo sectors takes a longer and longer time. One way to solve this problem is to use servo track writers to write spiral servo patterns on the disks and then perform self servo writing (SSW) within each HDD unit. The quality of the spirals is the key to achieve high TPI in SSW. This paper discusses high precision tracking control algorithms for the writing of spiral servo patterns. An iterative learning scheme is introduced, which combines a disturbance observer with the zero phase error tracking algorithm, and develops a new way of designing asymptotically optimal feedforward inputs for a general two degree of freedom control systems. In learning control schemes, non-repetitive disturbances have an adverse influence on the tracking performance. The paper analyzes this situation, and develops a robust learning scheme to deal with the problem.

B35 2自由度制御系に基づく旋回クレーンのロバスト制御(ロバスト制御)

This report deals with a vibration control method of rotary cranes with rotating and boom-hoisting. In the control of the rotary crane, it is important to consider the trade-off between the settle time and the vibration of the load. In this report, we discuss the design problem of 2 degree of freedom control system which is robust for the change of the rope length. Although dynamics of the rotary crane are described by a double-input quadruple-output nonlinear system, the derived linear dynamics are two single-input double-output systems. And we find out the effectiveness of the proposal method by the experiment.

Two-Step IMC−PID Method for Multiloop Control System Design

Proportional−integral−derivative (PID) controller tuning method based on the internal model control is one of the simplest tuning rules and provides excellent performances for various processes. It has one design parameter which determines the speed of closed-loop response. As the design parameter changes, the controller gain changes while integral and derivative times usually remain constant. Hence, the method can be extended easily to the design of multiloop control systems because there are simple methods to find stable multiloop proportional controller gains. However, integral and derivative times independent of the design parameter can cause poor closed-loop responses for some processes such as those with small dead times. For such processes, 2 degree of freedom control systems are usually required, and a two-step method where a proportional controller is designed first and then a PID controller is designed for the compensated system can be used to design the 2 degree of freedom control systems. This...

Anti-Windup Strategy for Two Degree of Freedom Control System Based on Left Coprime Factorization

In this paper, the anti-windup strategy for two degree of freedom (TDOF) control system is proposed. In TDOF control system, the input saturation can be avoided by designing the suitable command response property for nominal model. In real controlled systems, however, the input saturation may occur because of unknown disturbance or plant variation. The proposed method can suppress the windup phenomena by modelling the limiter into TDOF controller and adjusting the limitation between feedback and feedforward control. The proposed anti-windup controller (AWC) has the form of left coprime factorization of feedback and feedforward controllers. The proposed method is evaluated by simulation and experiment of position control system of DC servo motor.

Tuning and design of single-input, single-output control systems for parametric uncertainty

Frequency domain methods, which are for the design and tuning of control systems for processes with uncertain parameters, and are easy to use and interpret, are proposed. The advantages of the proposed methods over other H∞ methods are mainly that they require substantially less expertise on the part of the designer, and that they result in control system performance that closely approximates that which was desired. Several examples illustrate the proposed methods. A stable second-order lag and dead time process, with gain and dead time uncertainties, provides the vehicle for studying controller designs for single and two degree of freedom control systems. Application of Mp tuning to an uncertain, unstable, first-order lag, plus dead time process, shows that there can be a significant performance penalty associated with using a simple feedback control system rather than an internally stable model-based control system. The performance of a controller for an integrating, oscillatory process obtained by Mp synthesis also compares favorably with that of a controller obtained by other investigators using loop shaping.

Model reference control in two degree of freedom control systems: Adaptive min–max approach

The design of a control system, that provides a model reference performance specification for the command response and, at the same time, achieves some prespecified feedback properties, is discussed. The use of a particular configuration of a two degree-of freedom controller allows the feedback and performance specifications to be tackled independently through the design of a feedback controller for the nominal plant and the model reference part by means of model matching in a min-max sense. A closed-form solution is provided for the optimal min-max controller. This closed-form solution will be very useful when using this controller in an adaptive way. The resulting adaptive controller consists of a fixed feedback part and an adaptive open-loop part. Only one degree-of-freedom is adapted. An example shows that it is possible to match the model reference performance specification, even near the stability limit.

Control Performance of a Turret-Moored Vessel Assisted by Dynamic Positioning System

This paper presents a nonlinear motion simulation and a controller design for a turret-moored vessel assisted by dynamic positioning system. For the simulation, the hydrodynamic forces are calculated by applying Green function method. A dynamic positioning controller, robust to uncertainties brought about by time-varying environmental loads, has been designed applying H∞ control synthesis. A two degree of freedom control system is adopted for tracking mode. Numerical simulations show that the controller works satisfactorily.

能動空気軸受 浮上方向の位置と振動の超精密制御

This paper introduces an active air bearing. In the conventional passive type, for example, in an air slide, a table is supported by the pressurized air film which can be considered as a spring and damper system. Thus, disturbances, i. e. various kinds of external force cause the table vibration as well as the change of the air film thickness and that of the table floating position. Moreover, motion accuracy of the table depends on accuracy of guideways. These suggest necessity of a mechanism capable of floating position and vibration control of an object. In the active air bearing, a PZT actuator is used for controlling floating characteristics ; floating position and vibration of the object. The actuator is arranged in series to the air film not to damage its property ; free of mechanical contact. Two degrees of freedom control system (PID-PD or PID-PDD2) is adopted for obtaining desired characteristics of floating position control and active damping of vibration. In experiments, a 9 kg mass object is floated under control with 20 nm vibration amplitude, and is positioned with 20 nm positioning accuracy, 500 Hz bandwidth and no-overshoot.

Deep Submergence Navigation

To meet the challenging requirements of new undersea vehicles the Navy has under development a new breed of systems for navigation and control. These represent a significant size and weight reduction over the large navigation systems developed for submarines and incorporates the use of a variety of navigation sensors such as underwater transponders, a doppler sonar, an altitude/depth sonar and a miniature precision inertial platform. These systems form an integrated navigation suit which is adaptable for use as an accurate dead-reckoning system, and for precise sea-floor referenced navigation from acoustic transponders. The development also encompasses a six degree of freedom control system for both manual and automatic positioning of a submersible to an accuracy of a few inches. This will be required for mating with submarines or other underwater work tasks in the presence of ocean currents during rescue, search and recovery missions. Preliminary navigation tests using the ALUMINAUT, equipped for both doppler and transponder navigation, are quite promising.