Investigating The Efficiency Of The VPR And COFFE Area Models In Predicting The Layout Area Of FPGA Lookup Tables

A single tile in a mesh-based FPGA includes both the routing block and the logic block. The area estimate of a tile in an FPGA is used to determine the physical length of an FPGA’s routing segments. An estimate of the physical length of the routing segments is needed in order to accurately assess the performance of a proposed FPGA architecture. The VPR (Versatile Place and Route) and the COFFE (Circuit Optimization for FPGA Exploration) tools are widely used meshbased FPGA exploration environments. These tools map, place, and route benchmark circuits on FPGA architectures. Subsequently, based on area and delay measurements, the best architectural parameters of an FPGA are decided. The area models of the VPR and COFEE tools take only transistor size as input to estimate the area of a circuit. Realistically, the layout area of a circuit depends on both the transistor size and the number of metal layers that are available to route the circuit. This work measures the effect of the number of metal layers that are available for routing on FPGA layout area through a series of carefully laid out 4-LUTs (4-input Lookup Tables). Based on measured results, a correction factor for the COFFE area equation is determined. The correction factor is a function of both the transistor drive strength and the number of metal layers that are available for routing. Consequently, a new area estimation equation, that is based on the COFFE area model, is determined. The proposed area equation takes into consideration the effect of both the transistor drive strength and the number of metal layers that are available for routing on layout area. The area prediction error of the proposed area equation is significantly less than the area prediction errors of the VPR and COFFE area models.

Investigating The Efficiency Of The VPR And COFFE Area Models In Predicting The Layout Area Of FPGA Lookup Tables

A single tile in a mesh-based FPGA includes both the routing block and the logic block. The area estimate of a tile in an FPGA is used to determine the physical length of an FPGA’s routing segments. An estimate of the physical length of the routing segments is needed in order to accurately assess the performance of a proposed FPGA architecture. The VPR (Versatile Place and Route) and the COFFE (Circuit Optimization for FPGA Exploration) tools are widely used meshbased FPGA exploration environments. These tools map, place, and route benchmark circuits on FPGA architectures. Subsequently, based on area and delay measurements, the best architectural parameters of an FPGA are decided. The area models of the VPR and COFEE tools take only transistor size as input to estimate the area of a circuit. Realistically, the layout area of a circuit depends on both the transistor size and the number of metal layers that are available to route the circuit. This work measures the effect of the number of metal layers that are available for routing on FPGA layout area through a series of carefully laid out 4-LUTs (4-input Lookup Tables). Based on measured results, a correction factor for the COFFE area equation is determined. The correction factor is a function of both the transistor drive strength and the number of metal layers that are available for routing. Consequently, a new area estimation equation, that is based on the COFFE area model, is determined. The proposed area equation takes into consideration the effect of both the transistor drive strength and the number of metal layers that are available for routing on layout area. The area prediction error of the proposed area equation is significantly less than the area prediction errors of the VPR and COFFE area models.

SRM simulation with reduced amount of initial information taking into account saturation of magnetic circuit

The article describes the currently used approaches to mathematical modeling of switched reluctance electric machines. It is shown that the traditional approach uses a large amount of initial information on the dependence of the flux on the current and the angular position of the rotor in the form of lookup tables. It is proposed to use the description of the flux using the hyperbolic arcsine function. This approach will reduce the amount of preliminary information and thus simplify the procedures for configuring control systems.

Lookup Tables for Power Generation Performance of Photovoltaic Systems Covering 40 Geographic Locations (Wilayats) in the Sultanate of Oman, with and without Solar Tracking, and General Perspectives about Solar Irradiation

An energy modeler for solar photovoltaic (PV) systems may be limited to climatic data of certain major cities, not covering the one for which the PV system is intended. Additionally, a person not skilled in solar PV modeling may still desire a quick estimate of PV system electricity generation to help decide the level of investment in PV systems. This work addresses these points by establishing lookup tables to summarize predicted electricity generation, solar irradiation, and optimum orientation at various locations in the Sultanate of Oman. The results are produced by processing simulation data using the online open-access tool PVGIS (Photovoltaic Geographical Information System) of the European Commission’s Joint Research Centre (EC-JRC). The tables cover 40 out of the country’s 61 s-level administrative divisions (wilayats) and cover fixed and movable PV panels. The results show that the yearly electricity generation can change up to 11.86% due to the change of location. Two-axis PV tracking offers a small improvement (about 4% on average) over single-vertical-axis tracking but offers noticeable improvement (about 34% on average) over optimally oriented fixed PV panels. Monthly profiles of expected PV electricity generation, as well as the generation drop due to changing the PV mounting from free standing to building integrated, were examined for three locations. As general perspectives that may be of interest to global readers, this work provides quantitative evidence of the overall accuracy of the PVGIS-SARAH database through comparison with ground-measured global horizontal irradiation (GHI). In addition, a full example is presented considering 12 different countries in the northern and southern hemispheres that brings the attention of solar energy modelers to the level of errors they may encounter when the impact of longitude (thus, the exact location) is ignored for simplicity, while focus is given to the latitude.

Validation of Aero-Load Estimator for Convair 880 Aircraft Flight Simulator Benchmark with Electro-Hydrostatic Actuators

Simulating an aircraft model using of high fidelity models of subsystems for its primary and secondary flight control actuators requires measuring or estimating aero-load data acting on flight control surfaces. One solution would be to incorporate the data recorded from flight tests, which is a time-consuming and costly process. This paper proposes another solution based on the validation of an aero-loads estimator or on the hinge moments predictor for fully electrical aircraft simulator benchmark. This estimator is based on an aerodynamic coefficient calculation methodology, inspired by Roskam’s method that uses the geometrical data of the wing and control surfaces airfoils. The hinge moment values are found from two-dimensional lookup tables where the deflections of the control surfaces, aircraft altitude, and aircraft angles of attack are the input vectors of the tables; and the resulting hinge moment coefficients are the output vectors. The resulting hinge moment coefficients of the Convair 880 primary flight control surfaces are compared to those of its recorded flight test data; the results from the new software solution were found to be very accurate. Hinge moment lookup tables are integrated in the Convair 880 high fidelity flight simulation benchmark using mathematical models of energy-efficient Electro-Hydrostatic Actuators (EHA). Autopilot controls are designed for the roll, pitch, attitude and yaw damper motions using Proportional Integral (PI) controller scheduled for different flight conditions. Several different aircraft simulation scenarios are evaluated to demonstrate the efficacy and accuracy of the predicted hinge moment results.

Development of a quasi-linear parameter varying model for a tiltrotor aircraft

The research presented in this paper focuses on the development of a quasi-Linear Parameter Varying (qLPV) model for the XV-15 tiltrotor aircraft. The specific category of qLPV modeling technique, known as the model stitching technique, is employed to model the time-varying dynamics of XV-15 tiltrotor aircraft over the entire flight envelope. In this modeling approach, discrete linear state-space models are interpolated through lookup tables as function of scheduling parameters with the implementation of nonlinear equations of motion. The XV-15 qLPV model is configured with four scheduling parameters: altitude, nacelle incidence angle, wing flap angle and velocity. Additionally, a computational complexity analysis is presented. In particular, computational sensitivity of qLPV models configured with lookup tables to number of states and number of scheduling parameters is demonstrated. This is done to show the feasibility of real-time implementation of qLPV models with increasing fidelity (number of states) and expanding dynamic flight envelope (number of scheduling parameters).

Scalable Balanced Pipelined IPv6 Lookup Algorithm

One of the most critical router’s functions is the IP lookup. For each incoming IP packet, IP lookup determines the output port to which the packet should be forwarded. IPv6 addresses are envisioned to replace IPv4 addresses because the IPv4 address space is exhausted. Therefore, modern IP routers need to support IPv6 lookup. Most of the existing IP lookup algorithms are adjusted for the IPv4 lookup, but not for the IPv6 lookup. Scalability represents the main problem in the existing IP lookup algorithms because the IPv6 address space is much larger than the IPv4 address space due to longer IPv6 addresses. In this paper, we propose a novel IPv6 lookup algorithm that supports very large IPv6 lookup tables and achieves high IP lookup throughput.

Climate-controlled root zone parameters show potential to improve water flux simulations by land surface models

The root zone storage capacity (Sr) is the maximum volume of water in the subsurface that can potentially be accessed by vegetation for transpiration. It influences the seasonality of transpiration as well as fast and slow runoff processes. Many studies have shown that Sr is heterogeneous as controlled by local climate conditions, which affect vegetation strategies in sizing their root system able to support plant growth and to prevent water shortages. Root zone parameterization in most land surface models does not account for this climate control on root development and is based on lookup tables that prescribe the same root zone parameters worldwide for each vegetation class. These lookup tables are obtained from measurements of rooting structure that are scarce and hardly representative of the ecosystem scale. The objective of this research is to quantify and evaluate the effects of a climate-controlled representation of Sr on the water fluxes modeled by the Hydrology Tiled ECMWF Scheme for Surface Exchanges over Land (HTESSEL) land surface model. Climate-controlled Sr is estimated here with the “memory method” (MM) in which Sr is derived from the vegetation's memory of past root zone water storage deficits. Sr,MM is estimated for 15 river catchments over Australia across three contrasting climate regions: tropical, temperate and Mediterranean. Suitable representations of Sr,MM are implemented in an improved version of HTESSEL (Moisture Depth – MD) by accordingly modifying the soil depths to obtain a model Sr,MD that matches Sr,MM in the 15 catchments. In the control version of HTESSEL (CTR), Sr,CTR is larger than Sr,MM in 14 out of 15 catchments. Furthermore, the variability among the individual catchments of Sr,MM (117–722 mm) is considerably larger than of Sr,CTR (491–725 mm). The climate-controlled representation of Sr in the MD version results in a significant and consistent improvement of the modeled monthly seasonal climatology (1975–2010) and interannual anomalies of river discharge compared with observations. However, the effects on biases in long-term annual mean river discharge are small and mixed. The modeled monthly seasonal climatology of the catchment discharge improved in MD compared to CTR: the correlation with observations increased significantly from 0.84 to 0.90 in tropical catchments, from 0.74 to 0.86 in temperate catchments and from 0.86 to 0.96 in Mediterranean catchments. Correspondingly, the correlations of the interannual discharge anomalies improve significantly in MD from 0.74 to 0.78 in tropical catchments, from 0.80 to 0.85 in temperate catchments and from 0.71 to 0.79 in Mediterranean catchments. The results indicate that the use of climate-controlled Sr,MM can significantly improve the timing of modeled discharge and, by extension, also evaporation fluxes in land surface models. On the other hand, the method has not been shown to significantly reduce long-term climatological model biases over the catchments considered for this study.

Measurements of Rainfall Rate, Drop Size Distribution, and Variability at Middle and Higher Latitudes: Application to the Combined DPR-GMI Algorithm

The Global Precipitation Measurement mission is a major U.S.–Japan joint mission to understand the physics of the Earth’s global precipitation as a key component of its weather, climate, and hydrological systems. The core satellite carries a dual-precipitation radar and an advanced microwave imager which provide measurements to retrieve the drop size distribution (DSD) and rain rates using a Combined Radar-Radiometer Algorithm (CORRA). Our objective is to validate key assumptions and parameterizations in CORRA and enable improved estimation of precipitation products, especially in the middle-to-higher latitudes in both hemispheres. The DSD parameters and statistical relationships between DSD parameters and radar measurements are a central part of the rainfall retrieval algorithm, which is complicated by regimes where DSD measurements are abysmally sparse (over the open ocean). In view of this, we have assembled optical disdrometer datasets gathered by research vessels, ground stations, and aircrafts to simulate radar observables and validate the scattering lookup tables used in CORRA. The joint use of all DSD datasets spans a large range of drop concentrations and characteristic drop diameters. The scaling normalization of DSDs defines an intercept parameter NW, which normalizes the concentrations, and a scaling diameter Dm, which compresses or stretches the diameter coordinate axis. A major finding of this study is that a single relationship between NW and Dm, on average, unifies all datasets included, from stratocumulus to heavier rainfall regimes. A comparison with the NW–Dm relation used as a constraint in versions 6 and 7 of CORRA highlights the scope for improvement of rainfall retrievals for small drops (Dm < 1 mm) and large drops (Dm > 2 mm). The normalized specific attenuation–reflectivity relationships used in the combined algorithm are also found to match well the equivalent relationships derived using DSDs from the three datasets, suggesting that the currently assumed lookup tables are not a major source of uncertainty in the combined algorithm rainfall estimates.