skip to main content

This content will become publicly available on June 5, 2024

Title: Control Co-Design of Mechanical Power Takeoff for a Dual-flap Surge Wave Energy Converter
Abstract—This paper presents a control co-design method for designing the mechanical power takeoff (PTO) system of a dual- flap oscillating surge wave energy converter. Unlike most existing work’s simplified representation of harvested power, this paper derives a more realistic electrical power representation based on a concise PTO modelling. This electrical power is used as the objective for PTO design optimization with energy maxi- mization control also taken into consideration to enable a more comprehensive design evaluation. A simple PI control structure speeds up the simultaneous co-optimization of control and PTO parameters, and an equivalent circuit model of the WEC not only streamlines power representation but also facilitates more insightful evaluation of the optimization results. The optimized PTO shows a large improvement in terms of power potential and actual power performance. It’s found the generator’s  more » « less
Award ID(s):
Author(s) / Creator(s):
; ; ; ; ;
Date Published:
Journal Name:
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Wave energy converters (WECs) are a promising candidate for meeting the increasing energy demands of today’s society. It is known that the sizing and power take-off (PTO) control of WEC devices have a major impact on their performance. In addition, to improve power generation, WECs must be optimally deployed within a farm. While such individual aspects have been investigated for various WECs, potential improvements may be attained by leveraging an integrated, system-level design approach that considers all of these aspects. However, the computational complexity of estimating the hydrodynamic interaction effects significantly increases for large numbers of WECs. In this article, we undertake this challenge by developing data-driven surrogate models using artificial neural networks and the principles of many-body expansion. The effectiveness of this approach is demonstrated by solving a concurrent plant (i.e., sizing), control (i.e., PTO parameters), and layout optimization of heaving cylinder WEC devices. WEC dynamics were modeled in the frequency domain, subject to probabilistic incident waves with farms of 3, 5, 7, and 10 WECs. The results indicate promising directions toward a practical framework for array design investigations with more tractable computational demands. 
    more » « less
  2. The tidal waves of modern electronic/electrical devices have led to increasing demands for ubiquitous application-specific power converters. A conventional manual design procedure of such power converters is computation- and labor-intensive, which involves selecting and connecting component devices, tuning component-wise parameters and control schemes, and iteratively evaluating and optimizing the design. To automate and speed up this design process, we propose an automatic framework that designs custom power converters from design specifications using Monte Carlo Tree Search. Specifically, the framework embraces the upper-confidence-bound-tree (UCT), a variant of Monte Carlo Tree Search, to automate topology space exploration with circuit design specification-encoded reward signals. Moreover, our UCT-based approach can exploit small offline data via the specially designed default policy and can run in parallel to accelerate topology space exploration. Further, it utilizes a hybrid circuit evaluation strategy to substantially reduce design evaluation costs. Empirically, we demonstrated that our framework could generate energy-efficient circuit topologies for various target voltage conversion ratios. Compared to existing automatic topology optimization strategies, the proposed method is much more computationally efficient—the sequential version can generate topologies with the same quality while being up to 67% faster. The parallelization schemes can further achieve high speedups compared to the sequential version. 
    more » « less
  3. Ocean wave energy has the potential to play a crucial role in the shift to renewable energy. In order to improve wave energy conversion techniques, it is necessary to recognize the sub-optimal nature of traditional sequential design processes due to the interconnectedness of subsystems. A codesign optimization in this paper seeks to include effects of all subsystems within one optimization loop in order to reach a fully optimal design. A width and height sweep serves as a brute force geometry optimization while optimizing the power take-off components and controls using a pseudospectral method for each geometry. An investigation of electrical power and mechanical power maximization also outlines the contrasting nature of the two objectives to illustrate electrical power maximization’s importance for identifying optimality. The codesign optimization leads to an optimal design with a width of 12 m and a height of 10 m. Ultimately, the codesign optimization leads to a 62% increase in the objective function over the optimal design from a sequential design process while also requiring only about half the power take-off torque. 
    more » « less
  4. This paper concerns modeling, simulations and control design of turbo-electric distributed propulsion (TeDP) systems needed to power future hybrid aircraft systems. The approach taken is the one of control co-design by which the sizing and hardware selection of components and the TeDP architecture design are pursued so that potential e ects of control and automation are accounted for from the very beginning. Unique to this approach is a multi-layered modular modeling and control approach in which technology-specific modules comprising the complex dynamical system are characterized using unified interaction variables at their interfaces with the rest of the system. The dynamical performance of the interconnected system is assessed using these technology-agnostic interface variable specifications and, as such, can be applied to any candidate architecture of interest. Importantly, even the inputs to the TeDP system coming from pilot commands are modeled using such interface variables. This new multi-layered modeling captures the dynamics of energy and power as interactions. It also has a rather straightforward physical interpretation. The paper builds on our earlier results introduced for terrestrial power systems, including small micro-grids. We show how system feasibility and stability can be checked in real-time operations by modules exchanging the information about their interaction variables and adjusting in a near-autonomous manner so that, as system conditions vary, the interconnected system still functions. No such systematic control co-design exists to the best of our knowledge, but it is needed as both new technologies and more complex, often conflicting performance objectives emerge. We illustrate the approach on a representative TeDP architecture and compare it to today’s state-of-the-art. We close with a discussion on the generalization of the method for any given candidate architecture. Having such an approach dramatically reduces the R&D&D of novel candidate architectures. 
    more » « less
  5. Performance in hardware has typically played a major role in differentiating among leading candidates in cryptographic standardization efforts. Winners of two past NIST cryptographic contests (Rijndael in case of AES and Keccak in case of SHA-3) were ranked consistently among the two fastest candidates when implemented using FPGAs and ASICs. Hardware implementations of cryptographic operations may quite easily outperform software implementations for at least a subset of major performance metrics, such as speed, power consumption, and energy usage, as well as in terms of security against physical attacks, including side-channel analysis. Using hardware also permits much higher flexibility in trading one subset of these properties for another. A large number of candidates at the early stages of the standardization process makes the accurate and fair comparison very challenging. Nevertheless, in all major past cryptographic standardization efforts, future winners were identified quite early in the evaluation process and held their lead until the standard was selected. Additionally, identifying some candidates as either inherently slow or costly in hardware helped to eliminate a subset of candidates, saving countless hours of cryptanalysis. Finally, early implementations provided a baseline for future design space explorations, paving a way to more comprehensive and fairer benchmarking at the later stages of a given cryptographic competition. In this paper, we first summarize, compare, and analyze results reported by other groups until mid-May 2020, i.e., until the end of Round 2 of the NIST PQC process. We then outline our own methodology for implementing and benchmarking PQC candidates using both hardware and software/hardware co-design approaches. We apply our hardware approach to 6 lattice-based CCA-secure Key Encapsulation Mechanisms (KEMs), representing 4 NIST PQC submissions. We then apply a software-hardware co-design approach to 12 lattice-based CCA-secure KEMs, representing 8 Round 2 submissions. We hope that, combined with results reported by other groups, our study will provide NIST with helpful information regarding the relative performance of a significant subset of Round 2 PQC candidates, assuming that at least their major operations, and possibly the entire algorithms, are off-loaded to hardware. 
    more » « less