scholarly journals Can open-loop control algorithms solve the data center switching problem?

2019 ◽  
Author(s):  
Corey Pollock ◽  
Matthias Imboden ◽  
Flavio Pardo ◽  
David J. Bishop
Keyword(s):  
Data Centers ◽  
Beam Steering ◽  
Open Loop ◽  
Control Algorithms ◽  
Loop Control ◽  
All Optical ◽  
Different Types ◽  
Order Of Magnitude ◽  
Path Dependent ◽  
Insertion Losses

There is a world-wide push to create the next generation all-optical transmission and switching technologies for exascale data centers. In this paper we focus on the switching fabrics. Many different types of 2D architectures are being explored including MEMS/waveguides and semiconductor optical amplifiers. However, these tend to suffer from high, path dependent losses and crosstalk issues. The technologies with the best optical properties demonstrated to date in large fabrics (>100 ports) are 3D MEMS beam steering approaches. These have low average insertion losses, and equally important, a narrow loss distribution. However, 3D MEMS fabrics are generally dismissed from serious consideration for this application because of their slow switching speeds (~few milliseconds) and costs ($100/port). In this paper we show how novel feedforward open loop controls can solve both problems by improving switching speeds by two orders of magnitude and costs by one order of magnitude. With these improvements in hand, we believe 3D MEMS fabrics can become the technology of choice for data centers.

Hybrid buffer‐based optical packet switch with negative acknowledgment for multilevel data centers

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Sumit Chandra ◽  
Shahnaz Fatima ◽  
Raghuraj Singh Suryavanshi
Keyword(s):  
Data Centers ◽  
Web Applications ◽  
Optical Switch ◽  
Contention Resolution ◽  
Multilevel Data ◽  
All Optical ◽  
Optical Buffering ◽  
Different Types ◽  
Packet Switch ◽  
Novel Design

AbstractIn the present scenario, data centers serve many functionalities like storage, transfer of data, supporting web applications, etc. In data centers, various levels of hierarchy different types of switches are required; therefore, multifunctional data centers are desired. This paper discusses a novel design for optical switch which can be placed at various levels of hierarchy. In the proposed design, multifunctionality contention resolution schemes which consider electronic and optical buffering and all-optical negative acknowledgment (AO-NACK) are considered. In buffering technologies, contending packets are stored in either in electronic RAM or in fiber delay lines. In case of the AO-NACK scheme, contending packets are blocked, and a negative acknowledgment is sent back to the transmitting node and blocked packets are retransmitted. For various considered schemes, Monte Carlo simulation have been performed, results in terms of packet loss probability are presented, and it has been found that the performance of optical buffering is much superior to electronic buffering and AO-NACK schemes. It is found that, in the AO-NACK scheme, the numbers of retransmitted packets due to contention blocking are 33,304 which can be reduced to 7, by using a small amount of buffer at each node.

Yield Improvement via minimization of step height non-uniformity in Chemical Mechanical Planarization (CMP)

2005 ◽  
Vol 867 ◽  
Author(s):  
Muthukkumar Kadavasal ◽  
Sutee Eamkajornsiri ◽  
Abhijit Chandra ◽  
Ashraf F. Bastawros
Keyword(s):  
Chemical Mechanical Planarization ◽  
Open Loop ◽  
Step Height ◽  
Control Algorithms ◽  
Open Loop Control ◽  
Time Step ◽  
Surface Evolution ◽  
Loop Control ◽  
Final Surface ◽  
Pattern Density

AbstractObtaining local and global planarity is one of the prime criteria in dielectric and metal planarizations. Although Chemical Mechanical Planarization (CMP) helps us achieve this criterion in constant pattern density surfaces, the same is not true for variable pattern density surfaces this results in formation of global step heights across the die. This paper provides a pressure open loop control algorithms for obtaining planarity across a die containing variations in pattern densities. Based on the variation of pattern density and surface heights across the die, the surfaces are separated into zones and the pressure is varied spatially and/or temporally to obtain uniform surface heights, with enhanced step height uniformity. One of the algorithms looks ahead and recalculates/modifies the pressure values by identifying the step heights that could be formed after a specified time step. The final surface predictions have improved uniformity on the upper surface as well as on the step heights across the entire die. The simulation would help us track the polishing process for each time step and guide us with the optimized pressure values that can be applied in order to an uniform final surface evolution.

Four-Fin Bio-Inspired UUV: Modeling and Control Solutions

2011 ◽  
Author(s):  
Jason D. Geder ◽  
Ravi Ramamurti ◽  
John Palmisano ◽  
Marius Pruessner ◽  
Banahalli Ratna ◽  
...  
Keyword(s):  
Stream Flow ◽  
Free Stream ◽  
Open Loop ◽  
Control Algorithms ◽  
Loop Control ◽  
Modeling And Control ◽  
Pectoral Fins ◽  
Flow Speeds ◽  
Computational Fluid Dynamics Cfd ◽  
And Control

This paper describes the modeling and control development of a bio-inspired unmanned underwater vehicle (UUV) propelled by four pectoral fins. Based on both computational fluid dynamics (CFD) and experimental fin data, we develop a UUV model that focuses on an accurate representation of the fin-generated forces. Models of these forces span a range of controllable fin parameters, as well as take into account leading-trailing fin interactions and free stream flow speeds. The vehicle model is validated by comparing open-loop simulated responses with experimentally measured responses to identical fin inputs. Closed-loop control algorithms, which command changes in fin kinematics, are tested on the vehicle. Comparison of experimental and simulation results for various maneuvers validates the fin and vehicle models, and demonstrates the precise maneuvering capabilities enabled by the actively controlled curvature pectoral fins.

scholarly journals Modal Engineering for MEMS Devices: Application to Galvos and Scanners

2020 ◽  
Author(s):  
Lawrence Barrett ◽  
Matthias Imboden ◽  
Josh Javor ◽  
David K. Campbell ◽  
David J. Bishop
Keyword(s):  
High Speed ◽  
Open Loop ◽  
Optical Systems ◽  
Control Algorithms ◽  
Mems Devices ◽  
Open Loop Control ◽  
Optical Elements ◽  
Loop Control ◽  
High Q ◽  
Change Position

Optical systems typically use galvanometers (aka galvos) and scanners. Galvos move optical elements such as mirrors, quasi-statically, from one static position to another, and an important figure of merit is their step-settle relaxation time. Scanners move in an oscillatory fashion, typically at the device resonant frequency. MEMS devices, which have many advantages and are often used in such optical systems, are typically high Q devices. Moving from one position to another for a galvo or one frequency/amplitude to another for scanners, can take many periods to settle following the ring down. During these transitions, the optical system is inactive and the time is not being efficiently used. In this article we show how a novel class of open loop control algorithms can be used to rapidly change position, frequency and amplitude, typically in well under the period of the device. We show how the MEMS designer can excite, with complete, high-speed control, a vibrational mode of the system. We call this modal engineering, the ability to control the modes of the system in a practical, fast way. This control of the modes is accomplished with open loop control algorithms.

A Sub 0.8 Degree per Hour Mode-Matching MEMS Vibratory Gyroscope with Closed Loop Control for the Sense Mode

2013 ◽  
Vol 562-565 ◽  
pp. 260-264
Author(s):  
Chun Hua He ◽  
Qian Cheng Zhao ◽  
Da Chuan Liu ◽  
Zhen Chuan Yang ◽  
Gui Zhen Yan
Keyword(s):  
Closed Loop ◽  
Open Loop ◽  
Closed Loop Control ◽  
Mode Matching ◽  
Sense Mode ◽  
Loop Control ◽  
Vibratory Gyroscope ◽  
Closed Loop Control System ◽  
Loop Control System ◽  
Order Of Magnitude

A detailed analysis about the nonlinearity of a mode-matching MEMS vibratory gyroscope is presented in this paper, then closed loop control for the sense mode is adopted to improved the performances. Experimental results figure out that the mode-matching gyroscope with closed loop controlled sense mode achieves a scale factor of 65mV/deg/s with nonlinearity of 0.05% and asymmetry of 0.1%, and a bias instability of 0.77deg/h, while they are 60mV/deg/s, 1%, 4.6% and 9.8deg/h in the open loop controlled sense mode system, respectively. These performances can be improved by more than one order of magnitude in the closed loop control system.

scholarly journals Modal Engineering of Inductive Circuits to Achieve Rapid Settling Times

2021 ◽  
Author(s):  
Josh Javor ◽  
Lawrence Barrett ◽  
Matthias Imboden ◽  
Russ Giannetta ◽  
David K. Campbell ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Open Loop ◽  
Hall Sensor ◽  
Control Algorithms ◽  
Rf Coils ◽  
Design Element ◽  
Open Loop Control ◽  
Modeling Tools ◽  
Loop Control ◽  
Important Design

Inductive circuits and devices are a ubiquitous and important design element in many applications such as magnetic drives, galvanometers, magnetic scanners, applying DC magnetic fields to systems, RF coils in NMR systems and vast array of other applications. They are widely used to generate both DC and AC magnetic fields. Many of these applications require a rapid step and settling time, turning the DC or AC magnetic field on and off quickly. The inductive response normally makes this a challenging thing to do. In this article we discuss open loop control algorithms for achieving rapid step and settling times in four general categories of applications: DC and AC systems where the system is either under or over damped. Each of these four categories requires a different algorithm which we describe here. We show the operation of these drive methods using Simulink and Simscape modeling tools, analytical solutions to the underlying differential equations and in experimental results using an inductive magnetic coil and a Hall sensor. Finally, we demonstrate application of these techniques to significantly reduce ringing in a standard NMR circuit. We intend this article to be practical with useful, easy to apply algorithms and helpful tuning tricks.

Optimal Control of Nonlinear Structures

1988 ◽  
Vol 55 (4) ◽  
pp. 931-938 ◽  
Author(s):  
J. N. Yang ◽  
F. X. Long ◽  
D. Wong
Keyword(s):  
Optimal Control ◽  
Control Systems ◽  
Active Control ◽  
Control Algorithm ◽  
Open Loop ◽  
Control Algorithms ◽  
Nonlinear Structures ◽  
Open Loop Control ◽  
Loop Control ◽  
Optimal Control Algorithms

Three optimal control algorithms are proposed for reducing oscillations of flexible nonlinear structures subjected to general stochastic dynamic loads, such as earthquakes, waves, winds, etc. The optimal control forces are determined analytically by minimizing a time-dependent quadratic performance index, and nonlinear equations of motion are solved using the Wilson-θ numerical procedures. The optimal control algorithms developed for applications to nonlinear structures are referred to as the instantaneous optimal control algorithms, including the instantaneous optimal open-loop control algorithm, instantaneous optimal closed-loop control algorithm, and instantaneous optimal closed-open-loop control algorithm. These optimal algorithms are computationally efficient and suitable for on-line implementation of active control systems to realistic nonlinear structures. Numerical examples are worked out to demonstrate the applications of these optimal control algorithms to nonlinear structures. In particular, control of structures undergoing inelastic deformations under strong earthquake excitations are illustrated. The advantage of using combined passive/active control systems is also demonstrated.

Open-loop control of compensation for optical propagation through a turbulent shear flow

1998 ◽  
Author(s):  
C. Truman ◽  
Lenore McMackin ◽  
Robert Pierson ◽  
Kenneth Bishop ◽  
Ellen Chen
Keyword(s):  
Shear Flow ◽  
Open Loop ◽  
Turbulent Shear ◽  
Turbulent Shear Flow ◽  
Open Loop Control ◽  
Loop Control ◽  
Optical Propagation

scholarly journals Sensuator: A Hybrid Sensor–Actuator Approach to Soft Robotic Proprioception Using Recurrent Neural Networks

Actuators ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 30
Author(s):  
Pornthep Preechayasomboon ◽  
Eric Rombokas
Keyword(s):  
Neural Networks ◽  
Recurrent Neural Networks ◽  
Linear Models ◽  
Open Loop ◽  
Proof Of Concept ◽  
State Estimator ◽  
Loop Control ◽  
Practical Applications ◽  
Soft Actuator ◽  
The Cost

Soft robotic actuators are now being used in practical applications; however, they are often limited to open-loop control that relies on the inherent compliance of the actuator. Achieving human-like manipulation and grasping with soft robotic actuators requires at least some form of sensing, which often comes at the cost of complex fabrication and purposefully built sensor structures. In this paper, we utilize the actuating fluid itself as a sensing medium to achieve high-fidelity proprioception in a soft actuator. As our sensors are somewhat unstructured, their readings are difficult to interpret using linear models. We therefore present a proof of concept of a method for deriving the pose of the soft actuator using recurrent neural networks. We present the experimental setup and our learned state estimator to show that our method is viable for achieving proprioception and is also robust to common sensor failures.

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