Different Kinds Of Actuators Research Articles

Reliability-Oriented Configuration Optimization of More Electrical Control Systems

More electrical vehicles adopt dissimilar redundant control systems with dissimilar power supplies and dissimilar actuators to achieve high reliability and safety, but this introduces more intricacy into the configuration design. Currently, it is difficult to identify the optimum configuration via the conventional trial-and-error approach within an acceptable timeframe. Hence, it is imperative to discover novel methods for the configuration design of more electrical vehicles. This paper introduced the design specification of more electric vehicles and investigated the contribution of different kinds of actuators, presenting a new multi-objective configuration optimization approach on the foundation of system reliability, weight, power, and cost. By adopting the non-dominated sorting genetic algorithm-II (NSGA-II), the Pareto optimization design set was obtained. Then, the analytic hierarchy process (AHP) was introduced to make a comprehensive decision on the schemes in the Pareto set and determine the optimal system configuration. Eventually, numerical results indicated that the reliability of our designed configuration increased by 5.89% and 55.34%, respectively, compared with dual redundancies and single redundancy configurations, which verified the effectiveness and practicability of the proposed method.

Hybrid multi-objective control allocation strategy for reusable launch vehicle in re-entry phase

The reentry of the reusable launch vehicle (RLV) normally requires redundant and heterogeneous actuators to assist attitude control, so the control allocation (CA) technology for the over-actuated system is a key research nowadays. This paper not only discusses how to allocate the control command between two different kinds of actuators, the reaction control system (RCS) and control surfaces, but also presents a hybrid multi-objective control allocation strategy based on the analytic hierarchy process (AHP) method to achieve the pareto solutions to RLV's allocation problems. Firstly, both actuators' dynamic models with corresponding constraints, and RLV's nonlinear model are built as the basis. Secondly, this paper considers a series of optimization functions, such as the minimum of control allocation error, the minimum of the fuel consumption, the maximum of actuators' control efficiency, which makes RLV's allocation problem multi-objective and multi-constraint. Meanwhile, to achieve the pareto solution or the integrated optimal one from all the feasible solutions, a weighted combination approach is introduced in. Then, this multi-objective allocation problem is transformed into a more easily solved, single-objective one, in which each optimization function is multiplied with its corresponding dynamic weight value based on the preference matrix of AHP. Finally, this designed strategy is demonstrated in RLV's re-entry phase, which not only verifies its effectiveness and fault-tolerant capability, but also shows its advantages of achieving better comprehensive allocation performance by comparisons with the single-objective control or the other two traditional daisy-chaining and proportional allocation methods.

Approach to Reconfiguration of a Motion Control System for an Autonomous Underwater Vehicle

Reconfiguration of a motion control system (MCS) for an autonomous underwater vehicle (AUV) in case of failure of some of the controls or actuators that provide the vehicle propulsion and maneuvering is discussed. The features of actuators operating on different physical principles are analyzed. A nonlinear mathematical model of the vehicle motion is formed taking into account the features of the seawater medium due to higher viscosity. Nonlinearity does not allow traditional approaches to reconfiguration of aircraft motion control system to be used for the purposes described in this paper. The approach proposed for reconfiguration of the AUV MCS consists in the preliminary analysis of the conditions for using different kinds of actuators depending on the vehicle speed and maneuver. The choice of alternative efficient actuators is dictated by the need to compensate for the forces and moments generated by the failed equipment or the actuator to the maximum extent possible. The results of the AUV MCS reconfiguration are obtained for a failure of a bow rudders gear during the diving maneuver on the acceleration section of the path. Vertical thrusters are taken as backups capable of compensating for the forces and moments of the jammed bow rudders gear. The comparative quantitative estimates of the AUV MCS reconfiguration were obtained by mathematical simulation of the AUV diving maneuver. Further research is needed to extend the proposed approach to other AUV systems.

GMR effect in nonhomogeneous magnetic field

Magnetic field sensors, based on giant magnetoresistance (GMR) effect, have a wide range of practical implementations. One of them is the use as a positioning device in different kind of actuators. Here we report on modelling of magnetoresistivity response of spin-valve (SV) based GMR structure in a various geometry of SV positioning with respect to a magnetic reference label. The model includes the magnetic label of a certain shape producing a nonhomogeneous magnetic field in 3D space and moving along a straight line in front of SV device. Different mutual label-SV positioning is considered. The reaction of micromagnetic configuration in the ferromagnetic layers and corresponding magnetoresistive effect of the SV is calculated and analyzed.

Contribution of Plasma Control Technology for Aerodynamic Applications

AbstractSummary: During these past ten years, plasma actuators have been envisaged to control air flows. Usually, two main kinds of plasma actuators are available: the DC discharge actuator and the dielectric barrier discharge (DBD) actuator, but also some combinations of both systems are now being studied. In this paper we present the results obtained with these different kinds of actuators. The control parameters, the electrical behaviors, and the mechanical efficiencies of the actuators are given. Aerodynamic experiments have been made in several wind tunnels using Particle Image Velocimetry (P.I.V.), visualization, Laser Dopler Velocimetry and special “Pitot” tube techniques. Advantages and disadvantages of each actuator are discussed, and finally some aerodynamic applications are shown.Effect of a discharge on the airflow around a NACA body.imageEffect of a discharge on the airflow around a NACA body.

Micro-electro-mechanical systems fast fabrication by selective thick polysilicon growth in epitaxial reactor

A thick layer selective polysilicon growth technique has been developed for micro-electro-mechanical systems (MEMS) fabrication. It allows fast MEMS fabrication without using silicon on insulator wafers or deep ICPRIE etching. The fabrication technique is based on two main steps: a first seed layer of polysilicon is deposited and patterned; the second step consists in the selective growth of this layer in an epitaxial reactor. The first part of this work is devoted to the optimisation of growth parameters. Afterwards, this technique is applied for fabrication of different kinds of actuators, involving films several microns thick with good mechanical properties such as a low mechanical stress and a low roughness of the polysilicon film surface. Furthermore, thermal actuator prototypes were fabricated by using this technique;showing good mechanical properties and high reliability.

Influence of Composition and Dopant on Photostriction in Lanthanum-Modified Lead Zirconate Titanate Ceramics

The anomalous photovoltaic effect, i.e., substantial voltage generation exceeding band gap energies, by homogeneous illumination in the non-centrosymmetric materials is a wellknown phenomenon. This mechanism is fundamentally different from those observed in heterojunctions/homojunctions (i.e., solar cells) based on semiconductor materials with a symmetric crystal structure. Recently, light induced strain termed as Photostriction, has been demonstrated in noncentrosymmetric perovskite ferroelectrics as lanthanum-modified lead zirconate titanate (PLZT) ceramics. PLZT ceramics have gained considerable attention due to their large photostrictive responses. When a light is illuminated on a polarized photostrictive bimorph, a large photovoltage of the order of kV/mm is generated across its length in the spontaneous polarization direction which results in strain generation by converse-piezoelectric effect and caused the bimorph to deflect in the direction away from the illumination. The photoactuation has been demonstrated in PLZT ceramic wafers as two different kinds of actuators, (i) photo-driven relay and (ii) photo-driven micro walking machine. These materials are also promising for the photo-acoustic device (e.g., Photophone) of the optical communication system. However, photostriction being a recently observed phenomenon, is far from optimum condition. It is expected that the optimization with respect to materials and microstructural characteristics will lead to a substantial enhancement in the photoactuation efficiency. Increasing the photoactuation efficiency will eliminate the need for electrical energy, and will open up numerous possibilities of contactless actuators. In this paper the influence of composition dependence and impurity doping effects on microstructure and photostrictive responses of PLZT ceramics have been investigated.

Special Issue on Force and Compliance Control

When robots perform tasks in which constraint forces are applied to the end effector from the environment, the interactive forces must be controlled. Considering this problem, in robotics, force control has been recognized as one of the most important research topics since the beginning of robotics research. In order to control forces dexterously, several studies have been conducted concerning sensors, actuators, and control algorithms. Currently, compliance and impedance control is a newly identified topic in force control. In the biological analysis of human behavior, it is well known that man adjusts the impedance of skeletal muscles according to the kind of task and can perform them dexterously. A compliance/impedance control technique has been proposed in order to realize such a function in robot motion. The feature of compliance/impedance control is control of the interacting forces not directly but through adjustment of compliance/impedance parameters of the system. This control structure provides several benefits to enable robots perform to complex tasks dexterously; however, there are still a lot of problems to be solved before it can be put to practical use. This Special Issue provides an overview of recent research activities concerning force control technology in robotics with an emphasis on compliance and impedance control. The papers compiled in this issue include various topics of force control, such as compliant motion control, biological aspects of compliance control and this force control using different kinds of actuators. I believe that the contents of this issue contains useful information for researchers and engineers with interests in this area. Finally, I would like to express my appreciation to the authors for their efforts and contributions to this issue and also to the members of the editorial staff for their skillful assistance.