Real Time Math Simulation of Contact Interaction during Spacecraft Docking and Berthing

Contact reactions of guide surfaces of assembly interfaces lead to the decreasing of theirs lateral and angular misalignments. The focus of this paper is the development of algorithms for computation of guide surfaces contact forces with acceptable engineering accuracy for real time simulation of assembly operations. Therefore, each complex guide surface is described as a set of contacting elements. Each contacting element for one＇s part can be represented by a finite set of geometric primitives which geometry is described by low order algebraic equations. So contact conditions and geometric parameters for all pairs of primitives are determined by analytical expressions. Math models are developed for two classes of contact interaction. The first class includes all cases when each contacting surface has several degrees of freedom of motion. Therefore, contact reactions introduced into differential equations of motion are calculated by using contacting elements penetrations, stiffness and damping parameters. The second class corresponds to all cases when one of contacting surfaces has insignificant inertia and only one degree of freedom of relative displacement counteracted by a spring. Here contact reactions are calculated from spring tension with any practical accuracy. This is very useful in some practical applications. Presented algorithms provide real time simulation together with some approaches for reduction of redundant comnutations.

Implementation of Distributed Control System for Rice Mill Using C#

The paper presents the distributed control system for rice mill using C#language.The real-time manufacturing system can be implemented by utilizing the signal from the real time control units that is more operative than other old-fashioned control systems in the extent of modern industrial days.The software-based Distributed Control System(DCS)is novel fashionable than any other conventional control systems in the state-ofthe-art manufacturing developments.This research study emphasizes on the implementation of the DCS-based rice mill using visual C#.net.The Industrial Ethernet(IE)is realized between the top level controller for the operator and the controlled station for the remote devices.The model of client-server approach is more appropriate for the automation and manufacturing research purposes.In this study,the computer graphical simulation of the complete control development is depicted in real-time status quo by visual C#language under Visual Studio 2008 software.The parallel ports in the computers of remote terminal level and the master terminal level controllers have been interconnected with port interface coding by visual C#program.

Modeling methodology and fault simulation of distribution networks integrated with inverter-based DG

The increasing penetration of inverter-based distributed generations(DGs)significantly affects the fault characteristics of distribution networks.Fault analysis is a keystone for suitable protection scheme design.This paper presents the modelling methodology for distribution networks with inverter-based DGs and performs fault simulation based on the model.Firstly,a single inverter-based DG model based on the cascaded control structure is developed.Secondly,a simulation model of distribution network with two inverter-based DGs is established.Then,different fault simulations are performed based on the Real Time Digital Simulator(RTDS).Theoretical analyses are conducted to justify the simulation results,including the equivalent circuit of distribution networks with inverter-based DGs and the solution method for loop currents.

A novel hybrid cybersecurity scheme against false data injection attacks in automated power systems

The conventional power systems are evolving as smart grids.In recent times cyberattacks on smart grids have been increasing.Among different attacks,False Data Injection(FDI)is considered as an emerging threat that has significant impact.By exploiting the vulnerabilities of IEC 61850 Generic Object-Oriented Substation Events(GOOSE)and Sam-pled Values(SV)attackers can launch different FDI attacks.In this paper,a real-time set up capable of simulating FDI on GOOSE and SV protocols is developed to evaluate the impact of such attacks on power grid.IEC 62351 stipulates cybersecurity guidelines for GOOSE and SV,but only at communication or Information Technology(IT)level.Hence there is a need to develop a holistic security both at IT and Operation Technology(OT)level.In this regard,a novel sequence content resolver-based hybrid security scheme suitable to tackle FDI attacks on GOOSE and SV is proposed.Furthermore,the computational performance of the proposed hybrid security scheme is presented to demonstrate its applicability to the time critical GOOSE and SV protocols.

Analysis of reaction torque-based control of a redundant free-floating space robot

Owing to the dynamics coupling between a free-floating base and a manipulator, the non-stationary base of a space robot will face the issue of base disturbance due to a manipulator＇s motion. The reaction torque acted on the satellite base＇s centroid is an important index to measure the satellite base＇s disturbance. In this paper, a comprehensive analysis of the reaction torque is made, and a novel way to derive the analytical form of the reaction torque is proposed. In addition,the reaction torque null-space is derived, in which the manipulator＇s joint motion is dynamically decoupled from the motion of the satellite base, and its novel expression demonstrates the equivalence between the reaction torque null-space and the reaction null-space. Furthermore, the reaction torque acted as an optimization index can be utilized to achieve satellite base disturbance minimization in the generalized Jacobian-based end-effector Cartesian path tracking task. Besides, supposing that the redundant degrees of freedom are abundant to achieve reaction torque-based active control, the reaction torque can be used to realize satellite base attitude control, that is, base attitude adjustment or maintenance. Moreover, because reaction torque-based control is a second-order control scheme, joint torque minimization can be regarded as the optimization task in reaction torque-based active or in-active control. A real-time simulation system of a 7-DOF space robot under Linux/RTAI is developed to verify and test the feasibility and reliability of the proposed ideas. Our extensive empirical results demonstrate that the corresponding analysis about the reaction torque is correct and the proposed methods are feasible.

An Intelligent Coordinated Protection and Control Strategy for Distribution Network with Wind Generation Integration

Integration of distributed generation(DG)can change the fault current level and direction in the distribution system,which affects the related protection system.In order to limit the negative impact of DG integration and upgrade the protection system performance,an intelligent coordinated protection and control strategy is proposed.A cost based optimization method is adopted to minimize the operation costs of possible solutions.Its aim is to define the optimal relay settings for the present operation condition,and the most suitable control mode of converter based wind turbine DG.Case studies on a hardware in the loop real time simulation platform demonstrate the proposed protection strategy.