Jose Mireles

Intelligent material handling: development and implementation of a matrix-based discrete-event controller

A supervisory controller for discrete-event (DE) systems is presented that uses a novel matrix formulation. This matrix formulation makes it possible to directly write down the DE controller from standard manufacturing tools such as the bill of materials or the assembly tree. The matrices also make it straightforward to actually implement the DE controller on a manufacturing workcell for sequencing the jobs and assigning the resources. It is shown that the DE controller equations plus the Petri net marking transition equation together provide a complete dynamical description of a DE system. This means that a computer simulation can be performed to check the DE performance of the controller before it is implemented. In this paper, the authors implement the DE controller on an actual three-robot intelligent material handling cell at the Automation and Robotics Research Institute, University of Texas at Arlington, USA. Then, they show that the actual implementation and the simulated system give commensurate results. The versatility of the system developed with this DE controller permits implementing different methodologies for conflict resolution, as well as optimization of the resource assignment and part throughput. Technical information given includes the development of the controller in LabVIEW and its simulation using MATLAB.

Micromachined sensor design for optical‐fiber flow measurement

Purpose – Owing to the technology growth, especially in Microsystems technology and Nanotechnology, new products will provide new ways to sense variables that are crucial for product improvement and system reliability. A big concern of the scientific community is the measurement of low level flow measurements, especially for the biomedical and/or systems on a chip approaches.Design/methodology/approach – A new flow meter concept design consists of a surface micromachined sensor having an optical high reflective mirror made of gold, which is attached to unique cantilever designs that bend due to the drag force of mass flow. The bending of the cantilevers produces the mirror to approach/depart from an optical fiber end‐tip. The reflective light to fiber is modulated using a Fabry‐Perot interferometry technique to determine the mirror separation to the fiber, which corresponds to the mass flow.Findings – The new concept design shows a big potential approach to measure low flow measurements for air, gas and l...

Coordination control policy for mobile sensor networks with shared heterogeneous resources

This paper considers centralized coordination of cooperating heterogeneous wireless sensors with multiple shared resources. A discrete event controller (DEC) is used to sequence the most suitable tasks for stationary and mobile sensors according to the current perception of the environment, efficiently handling simultaneous missions of different priority. Its matrix formulation, apart from making the assignment of the mission planning straightforward and easily adaptable if agents or applications change, provides a powerful tool to analyze deadlock situations and implement efficient deadlock avoidance policies. It also represents a complete dynamical description of the system which allows computer simulation analysis. The matrix formulation also allows fast implementation of DEC for actual WSNs.

Deadlock avoidance for manufacturing multipart re-entrant flow lines using a matrix-based discrete event controller

A deadlock avoidance supervisory controller for Discrete Event (DE) Systems is implemented. The DE controller uses a novel rule-based matrix dispatching formulation (US patent received). This matrix formulation makes it easy to write down the DE controller from standard manufacturing tools such as the bill of materials or the assembly tree. It is shown that the DE controllers matrix form equations plus the Petri Net (PN) marking transition equation provide a complete dynamical description of DE systems. We provide circular wait analysis (CW) for deadlock-free dispatching rules for Multipart Re-entrant Flow line (MRF) regular systems, and provide a regularity test for these systems in PN and matrix notations. We analyse the so-called critical siphons, and certain critical subsystems to develop a DE controller that guaranties deadlock-free dispatching by limiting the work-in-progress in the critical subsystems associated with each CW. This least-restrictive dispatching policy avoids deadlock. The deadlockfree dispatching rules are implemented by the DE controller on a three-robot, two-machine re-entrant flow line, the Intelligent Material Handling cell at the Automation and Robotics Research Institute of UTA. Technical information given includes the development of the deadlock-free controller in LabVIEW.

Implementation of a Deadlock Avoidance Policy for Multipart Reentrant Flow Lines Using a Matrix-Based Discrete Event Controller

A deadlock avoidance supervisory controller for Discrete Event (DE) Systems is implemented. The DE controller uses a novel rule-based matrix dispatching formulation (US patent received). This matrix formulation makes it direct to write down the DE controller from standard manufacturing tools such as the bill of materials or the assembly tree. It is shown that the DE controller’s matrix form equations plus the Petri Net marking transition equation together provide a complete dynamical description of DE systems. Deadlock-free dispatching rules are derived by performing circular wait analysis (CW) for possible deadlock situations. We analyze the so-called critical siphons, certain critical subsystems and resources to develop a DE controller that guaranties deadlock-free dispatching by limiting the work-in-progress in the critical subsystems associated with each CW. This is the least-restrictive dispatching policy that avoids deadlock. The deadlock-free dispatching rules are implemented by the DE controller on a three-robot, two machine reentrant flow line, the Intelligent Material Handling cell at the Automation and Robotics Research Institute of UTA. Technical information given includes the development of the deadlock-free controller in LabVIEW® .Copyright

Study of Piezoelectric Energy Harvesting System Based on PZT

Harvesting energy from ambient vibrations to convert it into electrical energy is possible using piezoelectric elements; the energy can be stored and used to bias low power electronic devices. A lead zirconium titanate cantilever is studied as a power generator to an energy harvesting system. The optimal performance is determined in terms of power output; two different configurations of the piezoelectric element were studied: series and parallel. The maximum output power produced by the piezoelectric system was 120 mW at the operating frequency of 40 Hz across a resistive load of 70 kΩ. The useful power was capable to bias some electronic devices.

Blocking Phenomena Analysis for Discrete Event Systems with Failures and/or Preventive Maintenance Schedules

We present an analysis of possible blocking phenomena, deadlock, in Discrete Event Systems (DES) having corrective and/or Preventive Maintenance Schedules (PMS). Although deadlock avoidance analysis for several classes of DES systems has been widely published, and although different approaches for PMS exist, it is not obvious how to mix deadlock avoidance and maintenance theories to improve throughput. In this paper we show that for some DES structures having reentrant flow lines, it is not necessary to stop activities in the DES, for the case one or more machines in production lines are in PMS. However, PMS may cause deadlock to occur if activities continue in some machines. We propose deadlock-free dispatching rules derived by performing circular wait analysis for possible deadlock situations in systems with PMS. This is accomplished by integrating the PMS structure and failure dynamics into a separate DES system that acts as a disturbance in the primary Reentrant Flowline DES system. We propose a matrix formulation and a Finite State Machine to synchronize both subsystems.

MEMS Closed-Loop Control Incorporating a Memristor as Feedback Sensing Element

In this brief, the integration of a memristor with a microelectromechanical systems (MEMS) parallel plate capacitor coupled by an amplification stage is simulated. It is shown that the MEMS upper plate position can be controlled up to 95% of the total gap. Due to its common operation principle, the change in the MEMS plate position can be interpreted by the change in the memristor resistance or memristance. A memristance modulation of ~1 kΩ was observed. A polynomial expression representing the MEMS upper plate displacement as a function of the memristance is presented. Thereafter, a simple design for a voltage closed-loop control is presented, showing that the MEMS upper plate can be stabilized up to 95% of the total gap by using the memristor as a feedback sensing element. The memristor can play important dual roles in overcoming the limited operation range of MEMS parallel plate capacitors and in simplifying read-out circuits of those devices by representing the motion of the upper plate in the form of resistance change instead of capacitance change.

SnO 2 -based memristors and the potential synergies of integrating memristors with MEMS

Memristors, usually in the form metal/metal-oxide/metal, have attracted much attention due to their potential application for non-volatile memory. Their simple structure and ease of fabrication make them good candidates for dense memory with projections of 22 terabytes per wafer. Excellent switching times of ~10 ns, memory endurance of >109 cycles, and extrapolated retention times of >10 yrs have been reported. Interestingly, memristors use the migration of ions to change their resistance in response to charge flow, and can therefore measure and remember the amount of current that has flowed. This is similar to many MEMS devices in which the motion of mass is an operating principle of the device. Memristors are also similar to MEMS in the sense that they can both be resistant to radiation effects. Memristors are radiation tolerant since information is stored as a structural change and not as electronic charge. Functionally, a MEMS devices sensitivity to radiation is concomitant to the role that the dielectric layers play in the function of the device. This is due to radiation-induced trapped charge in the dielectrics which can alter device performance and in extreme cases cause failure. Although different material systems have been investigated for memristors, SnO2 has received little attention even though it demonstrates excellent electronic properties and a high resistance to displacement damage from radiation due to a large Frenkel defect energy (7 eV) compared its bandgap (3.6 eV). This talk discusses recent research on SnO2-based memristors and the potential synergies of integrating memristors with MEMS.

Optical fiber packaging for MEMS interfacing

An investigation study concerning positioning, alignment, bonding and packaging of optical fibers for interfacing with optical MEMS devices is being reviewed in this paper. The study includes a review of techniques and critical issues for optical fiber positioning, alignment, bonding, optical improvements, and coupling and interfacing through micro-lenses and waveguides. Also, we present a packaging design structure for hermetic sealing of optical MEMS devices requiring interfacing through optical fibers which considers aspects such as processes, assemble schemes and bonding techniques for Optical Fibers, which are briefly reviewed in this work. This packaging design considers the following conditions: hermeticity of the MEMS devices, optical fiber and MEMS die alignment and positioning, assembly process, and Simachined fixturing design for final assembly and positioning.