Dale Word

California State University, Chico, Chico, California, United States

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Publications (14)0.69 Total impact

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    ABSTRACT: Modern power-electronic systems need real-time simulations with short frame times to minimize switch-timing errors. At ESTS'09 we reported using FPGAs to achieve frame times as low as 400nS. We also described a non-real-time implementation of a multi-rate benchmark of an unmanned underwater vehicle. Recent research has resulted in a real-time implementation of the UUV benchmark with hardware in the loop and is now focused on the design of a more general low-cost, high-speed, real-time, multi-rate simulator that combines FPGAs with a conventional PC.
    Electric Ship Technologies Symposium (ESTS), 2011 IEEE; 01/2011
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    ABSTRACT: Recent research has focused on developing techniques that use field-programmable gate arrays (FPGAs) to support real-time simulation with frame times of a few microseconds or less. These techniques can be used to simulate, for example, modern power electronic systems in real time. It is now feasible to consider the use of FPGAs as part of a high-speed, real-time, distributed, multi-rate (HRDM) simulator. Different configurations are possible in which the FPGAs are combined with, for example, real-time Linux and Windows systems. An important goal is to develop a lowest-cost HRDM simulator that is affordable by educational institutions and small companies. By exploiting the full potential of FPGAs to host multi-rate simulations it is possible to design an effective low-cost HRDM system using only FPGAs and a Windows PC. Progress towards achieving this goal is the main subject of the paper.
    Proceedings of the 2010 Conference on Grand Challenges in Modeling & Simulation; 07/2010
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    ABSTRACT: Commercially available real-time simulation systems, usually based on a real-time version of Linux, can support real-time simulations with frame times as low as 10 to 20 microseconds. There is, however, a growing class of problems for which shorter frame times are essential. This is true for example of hardware-in-the-loop simulations of many power electronic and automobile engine simulations. The problem can be addressed by the use of an attached processor that executes the time-critical parts of the simulation without the danger of operating system interrupts during a real-time frame. Both digital signal processors and field-programmable gate arrays have been used for this purpose. Examples based on power electronic systems are presented. The design of a low-cost system capable of achieving frame times as low as 500 nanoseconds is described.
    Advances in System Simulation, International Conference on. 01/2010;
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    ABSTRACT: Frame times as low as 1-2 microseconds are needed for high-speed real-time (HSRT) simulations of power-electronic systems. To achieve such short frame times it is necessary to use special processing platforms and both digital signal processors (DSPs) and field-programmable gate arrays (FPGAs) have been used for this purpose. Programming these special platforms presents the simulation developer with significant problems since the currently available simulation software tools that support them are very limited. As a result early efforts to develop HSRT simulations have proved very labor intensive. Tools are now under development aimed at minimizing these problems. Mathematica and Matlab routines have been developed to convert differential-equation based math models first into the corresponding difference equations incorporating the selected integration algorithm and then into C-code. Methods of extracting the difference equations from graphical representations of circuit diagrams have also been investigated.
    Proceedings of the 2009 Grand Challenges in Modeling & Simulation Conference; 07/2009
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    ABSTRACT: Recent research has focused on developing techniques that use digital signal processors (DSPs) and field-programmable gate arrays (FPGAs) to support real-time simulation with frame times of a few microseconds or less. These techniques can be used to simulate, for example, modern power electronic systems in real time. Using these techniques as part of a larger system simulation with a wide dynamic bandwidth presents a number of challenges. Multirate solutions are often required, in which different frame times are used for different parts of the system. It is not normally a feasible option to implement the entire multi-rate simulation on a DSP-based or FPGA-based processor. Consequently the high-speed simulation must be integrated into a more conventional real-time simulation system, which is typically a real-time Linux-based system. The paper discusses some of the challenges involved in implementing an integrated high-speed, real-time, multi-rate simulation system.
    Proceedings of the 2009 Grand Challenges in Modeling & Simulation Conference; 07/2009
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    ABSTRACT: Real-time simulations of modern power electronic systems require very short frame times of the order of a few microseconds or less. Recent research has developed techniques using digital signal processors or field-programmable gate arrays to meet this need. Integrating these high-speed simulations in a complete power system simulation often requires multi-rate simulation techniques and integration of the high-speed platforms with conventional platforms based on a real-time operating system such as a real-time version of Linux.
    Electric Ship Technologies Symposium, 2009. ESTS 2009. IEEE; 05/2009
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    ABSTRACT: Multi-rate simulation techniques offer advantages to the computer simulation of large scale dynamic systems. Each part of the system is solved using the most appropriate time step and numerical integration method. The approach can be particularly advantageous in real-time applications, where it is essential to complete each set of calculations in the allotted real-time interval. The ESL Simulation language has parallel segment features which makes it particularly suited to the realization of multi-rate simulations. Experiences of using ESL and the Virtual Test Bed (VTB) to realize a multi-rate simulation of an underwater unmanned vehicle (UUV) are described. A non-real-time version of the simulation with 5 different frame rates has achieved speed increases of the order of 500 times with no significant loss of accuracy, making a real-time implementation feasible.This research has included analysis of the stability of multi-rate methods and these are summarized in the paper.
    Proceedings of the UKSim'11, International Conference on Computer Modelling and Simulation, Cambridge University, Emmanuel College, Cambridge, UK, 25-27 March 2009; 01/2009
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    ABSTRACT: Real-time simulators have been used as an aid to power system design for many years. Over time, scaled-down physical models and analog computer-based simulators have given way to real-time simulators based on digital technology. Another trend has been the need for shorter and shorter frame times for these digital real-time simulators. Modern power electronic systems use highfrequency Pulse-Width Modulated (PWM) controllers. Indications are that frame times of 2 μS are needed for PWM switching frequencies of 10 KHz. As frequencies increase further it is possible that frame times of less than 1 μS may be required.
    SIMULATION: Transactions of The Society for Modeling and Simulation International 01/2008; 84:441-456. · 0.69 Impact Factor
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    ABSTRACT: The power and propulsion system for an electric ship is a complex combination of electrical, mechanical, thermal and fluid dynamic components. Effective analysis of its behavior requires detailed computer simulations. Simulations of the complete system can be computationally very demanding, and execution times can be particularly problematical when multi-run optimization studies or real-time simulations are required. One approach to reducing the computational load in these simulations is to partition the system into a number of subsystems with different dynamic ranges. This allows different parts of the system to be solved with different time steps, thus avoiding the use of a small time step that is dictated by the fastest components, to simulate slow components that could be solved satisfactorily with longer time steps. The result is a simulation with many fewer individual calculations and therefore faster execution. This approach is referred to as multi-rate simulation. Although it offers more efficient execution, it also raises additional questions regarding the accuracy and stability of the simulation. Multi-rate simulation has been investigated using the example of an unmanned underwater vehicle (UUV) in a joint study by California State University, Chico, the University of South Carolina, and the University of Glasgow. The simulation language ESL promises to be a valuable aid in evaluating multi-rate techniques.
    Electric Ship Technologies Symposium, 2007. ESTS '07. IEEE; 06/2007
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    ABSTRACT: A research team at the McLeod Institute of Simulation Sciences (MISS) at California State University, Chico (CSUC) has been developing high-speed, real-time simulations of power electronic systems since 1999. At that time, real-time simulators were available mainly for large-scale power utility applications and offered minimum frame times in the region of 50 microS These simulators were customized to specific applications and were expensive (typically from hundreds of thousands to millions of dollars). With the rapid growth of power electronic applications along with the increasing use of higher-frequency, pulse-width modulation (PWM) controllers a need arose for higher-speed, but lower cost, real-time simulators. This was the motivation for the original research effort at Chico. The principal factors offering the potential for success were the availability of alternative computing architectures capable of achieving fast real-time operation, and the recognition that the algorithms commonly used for power system simulation, including those used in real-time simulation, had changed very little over almost four decades. It was felt that a fresh approach to the choice of numerical techniques offered the potential for significant improvement. Real-time simulation, in which simulated time is exactly equal to real time, is required whenever there is a need to interface the simulation to real hardware, to embedded software running at normal speed, or to a human operator. Hardware-in-the-loop (HIL) simulation, which is interpreted here to include embedded controllers in the loop, provides a convenient, safe and economical test environment for hardware components and subsystems. In the power electronics field, real controllers may be interfaced to a real-time simulator of the actual power system for test and evaluation. The controller will normally incorporate one or more embedded processors that execute the control algorithm. A real-time simulator might also be connected.
    05/2007;
  • Proceedings of the 2007 Summer Computer Simulation Conference, SCSC 2007, San Diego, California, USA, July 16-19, 2007; 01/2007
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    ABSTRACT: The problem of developing real-time simulations that include both high-speed (<10 μS frame time) and slower components can be alleviated using multi-rate simulation. Collaboration between California State University, Chico; the University of South Carolina; and the University of Glasgow, aims to develop a multi-rate demonstration example that includes a power electronic subsystem requiring high-speed simulation. The selected application is an unmanned underwater vehicle (UUV) that uses a battery as its energy source feeding an a.c. motor drive through a d.c. to a.c. converter. The drive powers the vessel which is modeled as a 6-degree of freedom platform with control surfaces. The model separates the system into subsystems that are simulated with different frame rates: the converter (fast), its controller (fast medium) the motor drive (slow medium), and the vessel and the battery (slow). The initial effort aims to combine the subsystems within a VTB environment using a new VTB multi-rate solver. Three different programming approaches have been used for the subsystems. The converter and controller are programmed using C++ code developed for high-speed real-time simulation at Chico. The electric drive uses native VTB models and the model for the vessel is written in Matlab.
    Proceedings of the 2007 Summer Computer Simulation Conference, SCSC 2007, San Diego, California, USA, July 16-19, 2007; 01/2007
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    ABSTRACT: Real-time simulation is a familiar technique for testing hardware and software in the loop and for operator training. An important parameter of these simulations is the frame-time necessary to capture the dynamics of the system being simulated. Modern power electronic systems, using higher frequency pulse-width modulation (PWM) converter control demand frame times that are significantly shorter than those found in most real-time simulators. The paper describes an approach to real-time simulation that is capable of achieving the frame times of 10 μS and less required for this application. It is a scalable technique that uses arrays of digital signal processors on commercially available boards plugged into a conventional desktop computer. Analog and digital interfaces provide for the connection of real hardware to the simulation. Although the technique has so far been applied only to power electronic systems, it is capable of being used in a wide range of applications in which frame times of less than 10 μS are required.
    Parallel and Distributed Simulation, 2004. PADS 2004. 18th Workshop on; 06/2004