Mohsen A. Jafari

Processing of advanced electroceramic components by fused deposition technique

Abstract A variety of advanced ceramic components were fabricated using the fused deposition of ceramics (FDC) process. In FDC, ceramic loaded polymer filaments are used to build parts in a layer-by-layer fashion. A process map, based on the compressive strength and modulus of the FDC feedstock, was developed to predict the feasibility of deposition with a variety of FDC filaments. Alumina structures with photonic bandgap properties were deposited for high frequency (GHz) applications. Net shape bismuth titanate components with oriented grains were fabricated by pre-alignment of small volume of seeds in green FDC parts, followed by grain growth treatment. Piezoelectric actuators with novel structures such as spiral and bellows were manufactured and studied.

Protecting Smart Grid Automation Systems Against Cyberattacks

The smart grid moves new power grid automation systems from being proprietary and closed to the current state of information technology (IT) which is highly interconnected and open. But open and interconnected automation platforms bring about major security challenges. The power grid automation network has inherent security risks due to the fact that the systems and applications for the power grid were originally designed without much consideration of cybersecurity. This paper first introduces scope and functionalities of power grid, its automation and control system, and communications. Potential cyberattacks and their adverse impacts on power grid operation are discussed, a general SCADA cyberattack process is presented. This paper discusses the major challenges and strategies to protect smart grid against cyberattacks and finally proposes a conceptual layered framework for protecting power grid automation systems against cyberattacks without compromising timely availability of control and signal data. The proposed “bump-in-the-wire” approach also provides security protection for legacy systems which do not have enough computational power or memory space to perform security functionalities. The on-site system test of the developed prototype security system is briefly presented as well.

Determination of Optimal Buffer Storage Capacities and Optimal Allocation in Multistage Automatic Transfer Lines

Abstract One way to improve the efficiency of automatic transfer lines is to provide intermediate storage buffers. These buffers divide the transfer line into stages, each with one or more machines. The machines in a stage are completely integrated, whereas, the stages are partially decoupled. Here, we study a problem related to buffer storage allocation. The objective is to find optimal distribution of a total storage space among the intermediate buffers. This is formulated as a dynamic programming problem and a heuristic solution is presented.

A novel system for fused deposition of advanced multiple ceramics

In this article we present the system that we have developed at Rutgers University for the solid freeform fabrication of multiple ceramic actuators and sensors. With solid free form fabrication, a part is built layer by layer, with each layer composed of roads of material forming the boundary and the interior of the layer. With our system, up to four different types of materials can be deposited in a given layer with any geometry. This system is intended for fabrication of functional parts; therefore the accuracy and precision of the fabrication process are of extreme importance.

An integrated security system of protecting Smart Grid against cyber attacks

Like any other industry sector, the electrical power industry is facing challenges involved with the increasing demand for interconnected system operations and control under the restructured electrical industry due to deregulation of the electrical market and the trend of the Smart Grid . This moves automation networks from outdated, proprietary, closed networks to the more current arena of Information Technology (IT). However, while gaining all of the cost and performance benefits of IT, existing IT security challenges are acquired as well. The power grid automation network has inherent security risks due to the fact that the systems and applications in the network were not originally designed for the general IT environment. In this paper, we propose a conceptual layered framework for protecting power grid automation systems against cyber attacks. The following factors are taken into account: 1) integration with existing, legacy systems in a non-intrusive fashion; 2) desirable performance in terms of modularity, scalability, extendibility, and manageability; 3) alignment to the “Roadmap to Secure Control Systems in the Energy Sector” [12] and the future intelligent power delivery systems [2,3,11]. The on-site test result of the system prototype is briefly presented as well.

Fault detection/monitoring using time Petri nets

While controlling manufacturing systems, real time data is collected through sensory devices or some other means and fed back to the controller for the purpose of monitoring that system. Monitoring refers to the analysis of data collected from the system. It involves fault detection and diagnostics. Here, we shall emphasize the fault detection aspects of monitoring. Modeling the control system by a time Petri net permits us to develop an analytical procedure for fault detection. By backfiring transitions in the time Petri net, we are able to determine if a given state is invalid. The back-firing approach also provides us with state space representation of time Petri nets and the maximum token holding times in different places of time Petri nets. >

The optimum target value for single filling operations with quality sampling plans

We address the problem of choosing the most cost efficient set point for an automatic filling operation on a production line. Several researchers have examined this problem for the case where the filling operation is followed by 100% inspection. However..

Vision-Based Online Process Control in Manufacturing Applications

Applications such as layered manufacturing, or in general, solid free-form fabrication, pose a major challenge on online process control. For these parts to be functional, it is imperative that their mechanical and structural properties are strictly kept within respective tolerances. To that end, no internal or external defects, especially voids, can be tolerated. Since these parts are made layer by layer, it is necessary to inspect top surface and boundary of each layer before the next layer is deposited. Two issues are of major concern here: 1) inspection must be nondestructive, that is, layer surface and boundary must not be touched by the inspecting instruments and 2) the time window for inspection and any corrective measures should not exceed the maximum time limits necessary for two adjacent layers to properly bind together. Here, we present a closed-loop online process control model, where the process feedbacks are obtained from a 3-D imaging system, and where the process dynamics model takes into account the correlation and dependency between adjacent layers. To ensure that the feedback is performed within the tolerable time windows, our 3-D image processing parametric model takes advantage of physical characteristic of layer surface, and uses Gaussian function as a shape descriptor of image units. We obtain 2-D profiles from representative signature(s), and then sweep along road path defined in the CAD model. The idea of reconstructing representative signature comprises some accuracy, but compared with classical shape-from-shading method, the proposed approach is computationally more efficient. The 3-D quality measures (such as volume or depth of voids) are then fed to process dynamics model, which computes the necessary compensation on the deposition flow rate for the next layer. We examine three process dynamics models to And out that a fuzzy model which takes into account correlation between adjacent layers and includes locally linear submodels for underfills and overfills is the most appropriate.

A rule-based system for generating a ladder logic control program from a high-level systems model

In this article an interface between a high-level specification of a system and a logic controller of that system is developed. The interface is based on a number of rules to transform an IDEF0 specification into an intermediate-level Petri-net-based controller and to transform the intermediate specification into a ladder logic program which can be run on a PLC. These rules could be used as a basis for developing an expert system to handle the interface. Such an expert system provides an environment for rapid prototyping and analysis of controllers.

Tool Path-Based Deposition Planning in Fused Deposition Processes

The fabrication of a functional part requires very high layer quality in the Fused Deposition (FD) processes. The constant deposition flow rate currently used in FD technology cannot meet this requirement, due to the varying geometries of the layers. To achieve a high quality functional part, an overfill and underfill analysis is conducted. A deposition planning approach is proposed, which is based on a grouping and mapping algorithm. Two piezoelectric test parts have been built to demonstrate the effectiveness and feasibility of the proposed approach.