On Integrating Object Detection Capability into a Coastal Energy Conversion System

U.S. Department of Defense, Office of Naval Research

Project Summary
Near-shore wave energy converter arrays may be designed to provide uninterrupted power to a number of coastal sensing applications, including sensors monitoring meteorological conditions, sea-water chemical/physical properties, tsunamis and storm surges, fish and other marine life, coastal and sea-floor conditions, etc. Active control seeking near-optimum hydrodynamic operation has been shown to enable a dramatic reduction in device size for required amounts of power. Certain features of the control strategies developed make them particularly amenable to incorporation of additional sensing capability based on the wave patterns generated by intruding submerged objects (at distances on the order of 1000 m), in particular, the phase changes to the approaching wave field that occur in the presence of an object.

This project investigates schemes for actively controlled wave energy converter arrays in coastal waters which enable detection of intruding marine vessels by monitoring the spatial and temporal energy conversion rates over the arrays. The proposed approach mainly utilizes a linear-theory based understanding of wave propagation, body hydrodynamics, and controller design, but also incorporates nonlinear extensions based on Volterra series modeling. Of particular interest, is using small device sizes, for which response nonlinearities can be significant. Therefore, it is proposed to exploit the nonlinearities to enhance energy generation. Furthermore, also investigate ways to utilize features of the nonlinear response that enable preferential coupling to certain phase signatures, so that energy conversion by certain array elements would imply the presence of an object. Analysis and simulation results on arrays of moored devices will be extended to free-floating arrays.

The first objective of the overall effort is to evaluate the proposed techniques through analysis and simulation. For near-shore sea areas to be identified, two categories or types of array designs with their own particular control strategies will be investigated, using Hydrodynamics and Controls based analytical techniques and detailed simulations (linear and nonlinear). Necessary in this process is the characterization of the phase-change signatures of various submerged objects when stationary and when in translation. This knowledge will provide the test parameters for the designs to be investigated. The first two years of the overall, 4-year long, effort are expected to provide the groundwork for the development of a prototype system. Prior to ‘at-sea’ prototype testing, first test the prototype in a wave-basin environment. To provide reliable designs for the testing in the wave basin, wave tank testing under simplified conditions is also proposed. The overall testing sequence from wave tank tests through wave-basin tests to ‘at sea’ tests is expected to occur over years 3 and 4.

Investigators: Umesh Korde, Rush Robinett, Ossama Abdelkhalik

Meta-Stability of Pulsed Load Microgrids

Sandia National Labs

Statement of Work
NAVSEA/ Military microgrids
Using the HSSPFC (Hamiltonian Surface Shaping and Power Flow Control) derived MATLAB/Simulink
tools develop a Reduced Order Model (ROM) to support control designs for pulse load applications for i)
up to (3) key ship modes of a ship power system operation and ii) a stable and unstable modes of
switching operations as a part of a survivability scenario.
Deliverables Tasks:
1. Provide ROM of meta-stable ship system.
2. Analyses and control design (feedforward and feedback) of meta-stable system.
3. Analyses and control design for multi-pulse load systems.
4. Analyses of the effects and potential benefits of non-linear magnetics in meta-stable system.
5. Develop and perform hardware testing on metastable laboratory benchtop system.
6. Develop networked Microgrid model for KIER/LUXCO scenario

Investigator: Wayne Weaver

Collaborative Research: On Making Wave Energy an Economical and Reliable Power Source for Ocean Measurement Applications

National Science Foundation

Work Plan:
Task 1: Wave-by-wave control and Multi-resonant control
(a-i) Wave-by-Wave Control: Generalize to conversion from relative oscillation in surge, heave, and pitch modes. This step places high expectations on geometry design, because the chosen geometry needs to maximize wave radiation (radiation damping) by relative oscillation in all three modes. Typically, for small axi-symmetric buoys, radiation damping in surge and pitch modes is considerably smaller than that in heave mode. Therefore, greater oscillation excursions are typically required for optimal conversion in these modes. In addition, the power requirements of the wave measurement hardware also need to be included in the daily/annual powver calculations. For the X-band Radar hardware applicable to the up-wave distances of interest to us (on the order of 1000 m), the power consumption is expected to be less than 300 W (average). This could pose a challenge in some wave conditions, but it is likely that the use of multiple modes and optimized geometries will help to provide sufficient usable power for the iFCB application we are pursuing in this work. We plan to extend the current simulations to address these needs.
(a-ii) Geometry Design: New geometry design/utilization approaches to maximize the radiation damping for the 3 relative oscillation modes are being considered. These will be evaluated through detailed simulations in the forthcoming period.
(b) Multi-resonant Control: Current implementations need to be extended to incorporate realistic oscillation constraints. Further extensions to 2-body systems with power capture from relative oscillation are also required, and are planned for the forthcoming period. Finally, the procedure also needs to be extended to investigate multiple-mode conversion (i.e. relative heave, pitch, and surge oscillations).
Task 2: Actuator Design and Energy Storage
Work is planned for the forthcoming period where propose to examine favorably interacting buoy-instrument cage geometries that will minimize the need for large amounts of reactive power to flow through the system. Particular attention will be given to hydrodynamic and mechanical coupling effects and ways to provide negative stiffness through geometry design.
In addition, non-polluting high-lubricity hydraulic fluids will be evaluated through actuator dynamic models over the frequency range of interest.
Task 3: Simulation of Complete System and Wave Tank Testing
This is an important part of the project. The complete system will be simulated following inclusion of multiple-mode relative oscillation conversion and more detailed actuator design. Besides the power requirements of the wave measurement system, all other non-function-critical power needs embedded within the overall system (on-board electronics, etc.) will be included in this simulation.
Wave tank tests are planned as part of this project. Preparations are currently underway to install a wave tank (with flap type absorbing wave makers) capable of providing accurate and repeatable sea states for this project. 1/2 or 1/5 scale models are planned.

Investigator: Umesh Korde

Hydrodynamic Control Using X-Band Radar for Wave Energy Converter Technology

U.S. Dept of Defense, Naval Facilities Engineering Command

The current approach for designing wave energy converters is to use a floating-body tuned to the wave climate, which results in a very large device that is expensive to build, service and deploy. Additionally, because the device is designed to be tuned to a specific climate, it will not work effectively in a different location ·with a different climate. Therefore, the current approach for designing wave energy converters is not conducive to long-term economic application.

Economically significant size reduction and year-round power increases are only possible through operation near theoretical efficiency limits in constantly changing wave conditions, which requires active hydrodynamic control. However, the wave-by-wave control necessary for best conversion is not possible without wave-elevation information up to some duration into the future (this in large part is because of the force due to the waves generated by body oscillation in response to the incident wave field). By incorporating wave-elevation prediction based on a deterministic propagation model that accounts for a realistic range of wave-group velocities in conjunction with wave measurements in the up-wave directions, we have been able to confirm, through simulations, a 10-fold increase in power conversion under a swept-volume oscillation constraint for an omni-directional heaving buoy type device.
Availability of instantaneous wave profile (“wave surface elevation” or “wave elevation”) measurements and wave surface elevation predictions is important to the success of the control approach being pursued in this work. Equally important is the near-optimal wave-by-wave control approach itself.

Proposed research:
1. A method for obtaining instantaneous wave surface elevation information on a wave-by wave basis using a low-cost X-band Radar (the state of the art, as represented by the commercially available WaMOS system is optimized to provide spectral information.
2. A method for providing constrained near-optimal wave-by-wave control for maximizing the energy conversion by small wave energy converters.
3. Although the focus of the proposed research is wave energy converter technology, the results of this work are expected to find application in other forthcoming Navy developments. Wave-by-wave surface elevation prediction and near-optimal power absorption techniques demonstrated in this effort can be extended to facilitate critical mid-sea shipboard operations such as helicopter/ aircraft landing, cargo handling, etc. The techniques demonstrated as part of this research will also provide technology to enhance and optimize seakeeping characteristics of Navy ocean platforms.

Investigator: Umesh Korde

Wave Energy Conversion (WECs)

WECS are devices with moving elements that are directly activated by the cyclic oscillation of the waves for Ocean wave energy utilization and energy harvesting. Power is extracted by converting the kinetic energy of these displacing parts into electric current; dynamics, control, and hydrodynamics of oscillating bodies and pressure distributions performing as the primary working element of a wave energy converter. Specific recent research has been on small devices capable of integration into measurement and sensing systems in the ocean, as well as shore and ocean based microgrids serving a variety of applications. A focal area of this current research has been new techniques for modeling and control, including novel ways to utilize existing approaches.

Modeling and Control Technologies for Near-Term and Long-Term Networked Microgrids

Argonne National Laboratory

Microgrids offer attractive options for enhancing energy surety and increasing renewable energy penetration. Within a single microgrid energy generation, storage and utilization is localized. Greater enhancements to energy surety can be accomplished by networking multiple microgrids into a collective which can lead to almost unlimited use of renewable sources, reduction of fossil fuels and self-healing and adaptive systems. However, one pitfall to avoid is losing the surety within the individual microgrids. This produces design and control challenges that are currently unsolved in networked microgrids. To help solve this dilemma, development of analysis methods for design and control of networked microgrids is the general focus of this activity.

Specific tasks include:
1. Collaborate and form a coalition with national labs and other microgrid stakeholders to identify key R&D topics in networked microgrids.
2. Look at near term solutions that can quickly and easily be integrated into existing microgrids,
3. Determine best practices and optimized control strategies for the ground-up design of future networked microgrids.
4. Work within the DOE and national lab partnerships to produce the FOA whitepaper on single microgrid systems.
Tasks 1 through 3 will include microgrid modeling, control and optimizations of single and networked microgrids with focus on achieving DOE 2020 microgrid targets. Specifically, targets include developing commercial scale microgrid systems that reduce outage time, improve reliability and reduce emissions.

TASK 1: Collaborate and form a coalition with national labs and other microgrid stakeholders to identify key R&D topics in networked microgrids.

TASK 2: Look at near term solutions that can quickly and easily be integrated into existing microgrids Model development is one of the first steps in the microgrid control design process and incurs trade-offs between fidelity and computational expense. Models used for modelbased control implementation must be real-time while having sufficient accuracy so that feed-forward information can be maximized to achieve specified requirements. The expected outcomes of this study are (1) determination of appropriate time scales for networked microgrid modeling (2) a MATLAB/ Simulink reduced order model library of networked microgrid components and (3) lab scale hardware validation of networked microgrid models. These model libraries will then be used to construct models and develop control and optimization algorithms of current microgrid systems and equipment.

Task 3: Determine best practices and optimized control strategies for the ground-up design of future networked microgrids. Demonstrating robust networked microgrids will require system-level optimization. This includes both its physical and control system designs. This task will build upon the models and optimizations achieved in task 2 applied to the design of future networked microgrids. The expected outcomes of this study are (1) energy-optimal design methods suitable for networked microgrid design and control of future long-term application architectures and (2) integration of these strategies with the microgrid model environment and bench scale hardware described in task 2.

Investigators: Wayne Weaver, Gordon Parker

Agent Based Control with Application to Microgrids with High Penetration Renewables

Sandia National Laboratory

Prior Work is leveraged; MTU has developed and demonstrated through simulation a prototype multiagent system that coordinates the life cycle operations of a microgrid collective composed of independent electric power sources, loads, and storage. MTU has performed simulations of DC micro grids of varying compositions and characteristics. MTU has analyzed simulation results, and developed candidate architectures and protocols for agent-based microgrid controls.

Execution of this project will further technical innovations associated with multi-agent software controlling microgrid collectives. The microgrid control algorithms for microgrid collectives will be developed and refined using Michigan Tech microgrid models and simulations validated against the MTU test bench. The algorithms will then be applied to SNL hardware models in simulation and finally against the SNL hardware test bed.

Agent-based control systems will be further developed by MTU in Matlab/Simulink blocks, tested, and refined through simulations. Once control performance objectives have been achieved, the systems will be ported to the MTU situated multi-agent system (MAS) and supporting servo loop controllers on the MTU test bench for evaluation. New Matlab simulations will be tailored and tuned to control the SNL test bed models and verified in simulation. SNL will re-apply the MTU MAS to the physical SNL test bed. SNL will collaborate with MTU on implementation and validation. Collaborative efforts will ensure that SNL attains the technology necessary to achieve the final project objectives for the SNL test bed

Required Research Innovations:
1. Identify control system performance issues between agent informatics and DC nonlinear controls. Since global computations require input from various points, processor speed and network bandwidth may dominate the performance of collaborative protocols that rely on nonlinear control approaches. Research must identify the computational and communication limits for porting nonlinear controls to agent control layers.
2. Investigate scaling properties for controls applied to increasing the number of interconnected DC microgrids. Trading power between microgrids may not be feasible due to geographical distances or communication time latencies. There may also be thresholds identified for collaboration considerations, such as partnering with 10 microgrids or less, due to the global computation requirements. Control scaling results should describe the appropriate considerations at various time scales (seconds, minutes, hours, and days). Additional considerations for scalability may include increasing the number of components within a single microgrid and increasing the variety of components within the microgrid.

Investigators: Gordon Parker, Wayne Weaver, Steven Goldsmith

Nina Mahmoudian

Nina Mahmoudian_Fall2013-1Dr. Mahmoudian’s general research interests lie in the area of dynamics, stability, and control of nonlinear systems. Specifically, she is interested in dynamic modeling, motion planning, and developing cooperative control algorithms to autonomous vehicles. Design and control of autonomous vehicles based on the principles used by nature is another area of interest.  She works on developing analytical and computational tools for the cooperative control of a network of autonomous vehicles in complex environment using nonlinear control and stochastic analysis. The application will be for air, ground, and sea autonomous vehicles.

Areas of Expertise

  • Nonlinear Control and Dynamics
  • Cooperative Control of Multi Agent Systems
  • Autonomous Vehicles with Special Interest in Underwater Gliders

Prepositioned Power Research


Prepositioned Power RobotsResearch is focused on developing technology to create systems that can autonomously create a microgrid, for situations that require the ability to preposition a basic level of energy infrastructure such as areas damaged by natural or man-made disasters, and autonomously deploying forward operating bases. Modeling and control of robotics and power conversion systems provides the ability to create such prepositioned electric power networks.

Active Projects


Autonomous Robots can carry a variety of power equipment:

  • Intelligent power electronics for energy conversion
  • Power connection hardware
  • Generation sources, both traditional and renewable
  • Energy storage


Prepositioned Power

Prepositioned Power

Four autonomous microgrid robots, each with different power network functionality. Two have renewable energy generation and storage capability, another has a conventional diesel genset, and the third contains intelligent power electronics for conversion and hard-line interconnection, and switchgear. After assessing the power requirements and available resources they would physically organize and electrically interconnect to form a micro-grid.