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James D. Van De Ven – One of the best experts on this subject based on the ideXlab platform.

  • constant pressure hydraulic energy storage through a variable area piston hydraulic Accumulator
    Applied Energy, 2013
    Co-Authors: James D. Van De Ven

    Abstract:

    Hydraulic Accumulators are used in a variety of applications to minimize the pressure variation in hydraulic circuits and to store energy. Conventional hydraulic Accumulators suffer from two major limitations, the hydraulic system pressure varies with the quantity of energy stored and the energy density is significantly lower than other energy domains. In this paper, a novel hydraulic Accumulator is presented that uses a piston with an area that varies with stroke to maintain a constant hydraulic system pressure while the gas pressure changes. The variable area piston is sealed with a fabric reinforced rolling diaphragm. In this work, the piston radius profile is developed as a function of the piston displacement and then transformed into a function of the axial contact location between the piston and the diaphragm. The piston profile was solved numerically for a variety of conditions using both transformation methods to illustrate the geometric design trade-offs. Using a variable area gas piston with a fixed cylinder area, the maximum gas volume ratio was 1.8:1. An analysis of the energy density revealed that the constant pressure Accumulator provides a 16% improvement in energy density over a conventional Accumulator at a volume ratio of 2.71:1 and also exceeds the maximum energy density of a conventional Accumulator at the lower volume ratio of 1.8:1. This new promising technology maintains a constant hydraulic system pressure independent of the quantity of energy stored, easing system control and allowing other circuit components to be downsized to meet the same power requirements, while also increases the energy storage density.

  • Increasing hydraulic energy storage capacity: Flywheel-Accumulator
    International Journal of Fluid Power, 2009
    Co-Authors: James D. Van De Ven

    Abstract:

    AbstractThe energy storage density of hydraulic Accumulators is significantly lower than energy storage devices in other energy domains. As a novel solution to improve the energy density of hydraulic systems, a flywheel-Accumulator is presented. Energy is stored in the flywheel-Accumulator by compressing a gas, increasing the moment of inertia of the flywheel by adding hydraulic fluid, and by increasing the angular velocity of the flywheel. Through a numerical model of the energy flows in the system, the energy storage of the flywheel-Accumulator was demonstrated to be approximately 10 times greater than a conventional Accumulator. Furthermore, the flywheel-Accumulator allows the hydraulic system pressure to be independent of the quantity of energy stored. The integral flywheel-Accumulator presents numerous future research challenges, yet offers the potential to transform and enable numerous applications including plug-in hydraulic hybrid vehicles.

Stepan Lapshev – One of the best experts on this subject based on the ideXlab platform.

  • Using multiple-Accumulator CMACs to improve efficiency of the X part of an input-buffered FX correlator
    Experimental Astronomy, 2017
    Co-Authors: Stepan Lapshev, S. M. Rezaul Hasan

    Abstract:

    This paper presents the approach of using complex multiplier-Accumulators (CMACs) with multiple Accumulators to reduce the total number of memory operations in an input-buffered architecture for the X part of an FX correlator. A processing unit of this architecture uses an array of CMACs that are reused for different groups of baselines. The disadvantage of processing correlations in this way is that each input data sample has to be read multiple times from the memory because each input signal is used in many of these baseline groups. While a one-Accumulator CMAC cannot switch to a different baseline until it is finished integrating the current one, a multiple-Accumulator CMAC can. Thus, the array of multiple-Accumulator CMACs can switch between processing different baselines that share some input signals at any moment to reuse the current data in the processing buffers. In this way significant reductions in the number of memory read operations are achieved with only a few Accumulators per CMAC. For example, for a large number of input signals three-Accumulator CMACs reduce the total number of memory operations by more than a third. Simulated energy measurements of four VLSI designs in a high-performance 28 nm CMOS technology are presented in this paper to demonstrate that using multiple Accumulators can also lead to reduced power dissipation of the processing array. Using three Accumulators as opposed to one has been found to reduce the overall energy of 8-bit CMACs by 1.4% through the reduction of the switching activity within their circuits, which is in addition to a more than 30% reduction in the memory.

  • On the architecture for the X part of a very large FX correlator using two-Accumulator CMACs
    Experimental Astronomy, 2016
    Co-Authors: Stepan Lapshev, S. M. Rezaul Hasan

    Abstract:

    This paper presents an improved input-buffer architecture for the X part of a very large FX correlator that optimizes memory use to both increase performance and reduce the overall power consumption. The architecture uses an array of two-Accumulator CMACs that are reused for different pairs of correlated signals. Using two Accumulators in every CMAC allows the processing array to alternately correlate two sets of signal pairs selected in such a way so that they share some or all of the processed data samples. This leads to increased processing bandwidth and a significant reduction of the memory read rate due to not having to update some or all of the processing buffers in every second processing cycle. The overall memory access rate is at most 75 % of that of the single-Accumulator CMAC array. This architecture is intended for correlators of very large multi-element radio telescopes such as the Square Kilometre Array (SKA), and is suitable for an ASIC implementation.

S. M. Rezaul Hasan – One of the best experts on this subject based on the ideXlab platform.

  • On the architecture for the X part of a very large FX correlator using two-Accumulator CMACs
    Experimental Astronomy, 2016
    Co-Authors: Stepan Lapshev, S. M. Rezaul Hasan

    Abstract:

    This paper presents an improved input-buffer architecture for the X part of a very large FX correlator that optimizes memory use to both increase performance and reduce the overall power consumption. The architecture uses an array of two-Accumulator CMACs that are reused for different pairs of correlated signals. Using two Accumulators in every CMAC allows the processing array to alternately correlate two sets of signal pairs selected in such a way so that they share some or all of the processed data samples. This leads to increased processing bandwidth and a significant reduction of the memory read rate due to not having to update some or all of the processing buffers in every second processing cycle. The overall memory access rate is at most 75 % of that of the single-Accumulator CMAC array. This architecture is intended for correlators of very large multi-element radio telescopes such as the Square Kilometre Array (SKA), and is suitable for an ASIC implementation.