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Your search keyword '"Yang, Bong-Jun"' showing total 37 results
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37 results on '"Yang, Bong-Jun"'

1. Adaptive control of a class of nonaffine systems using neural networks

Author

Yang, Bong-Jun and Calise, Anthony J.

Subjects
Neural networks -- Analysis, Liapunov functions -- Usage, Neural network, Business, Computers, Electronics, Electronics and electrical industries
Abstract

A neural control synthesis method is considered for a class of nonaffine uncertain single-input--single-output (SISO) systems. The method eliminates a fixed-point assumption and does not assume boundedness on the time derivative of a control effectiveness term. One or the other of these assumptions exist in earlier papers on this subject. Using Lyapunov's direct method, it is shown that all the signals of the closed-loop system are uniformly ultimately bounded, and that the tracking error converges to an adjustable neighborhood of the origin. Simulation with a Van Der Pol equation with nonaffine control terms illustrates the approach. Index Terms--Feedback linearization, neurocontrollers, nonaffine systems.

Published
2007

2. Coordinated decentralized adaptive output feedback control of interconnected systems

Author

Hovakimyan, Naira, Lavretsky, Eugene, Yang, Bong-Jun, and Calise, Anthony J.

Subjects
Neural networks -- Research, Control systems -- Research, Neural network, Business, Computers, Electronics, Electronics and electrical industries
Abstract

A decentralized adaptive output feedback control design is proposed for large-scale interconnected systems. It is assumed that all the controllers share prior information about the system reference models. Based on that information, a linearly parameterized neural network is introduced for each subsystem to partially cancel the effect of the interconnections on tracking performance. Boundedness of error signals is shown through Lyapunov's direct method. Index Terms--Adaptive output feedback, coordinated decentralized control, interconnected systems.

Published
2005

4. Adaptive Control of Truss Structures for Gossamer Spacecraft

Author

Yang, Bong-Jun, Calise, Anthony J, Craig, James I, and Whorton, Mark S

Subjects
Spacecraft Propulsion And Power
Abstract

Neural network-based adaptive control is considered for active control of a highly flexible truss structure which may be used to support solar sail membranes. The objective is to suppress unwanted vibrations in SAFE (Solar Array Flight Experiment) boom, a test-bed located at NASA. Compared to previous tests that restrained truss structures in planar motion, full three dimensional motions are tested. Experimental results illustrate the potential of adaptive control in compensating for nonlinear actuation and modeling error, and in rejecting external disturbances.

Published
2007

5. Adaptive Control of Truss Structures for Gossamer Spacecraft

Author

Yang Bong-Jun, Calise, anthony J, Craig, James I, and Whorton, Mark S

Subjects
Spacecraft Design, Testing And Performance
Abstract

Neural network-based adaptive control is considered for active control of a highly flexible truss structure which may be used to support solar sail membranes. The objective is to suppress unwanted vibrations in SAFE (Solar Array Flight Experiment) boom, a test-bed located at NASA. Compared to previous tests that restrained truss structures in planar motion, full three dimensional motions are tested. Experimental results illustrate the potential of adaptive control in compensating for nonlinear actuation and modeling error, and in rejecting external disturbances.

Published
2007

6. Adaptive Control for Microgravity Vibration Isolation System

Author

Yang, Bong-Jun, Calise, Anthony J, Craig, James I, and Whorton, Mark S

Subjects
Space Sciences (General)
Abstract

Most active vibration isolation systems that try to a provide quiescent acceleration environment for space science experiments have utilized linear design methods. In this paper, we address adaptive control augmentation of an existing classical controller that employs a high-gain acceleration feedback together with a low-gain position feedback to center the isolated platform. The control design feature includes parametric and dynamic uncertainties because the hardware of the isolation system is built as a payload-level isolator, and the acceleration Sensor exhibits a significant bias. A neural network is incorporated to adaptively compensate for the system uncertainties, and a high-pass filter is introduced to mitigate the effect of the measurement bias. Simulations show that the adaptive control improves the performance of the existing acceleration controller and keep the level of the isolated platform deviation to that of the existing control system.

Published
2005

15. On-Line Trajectory Optimization for Autonomous Air Vehicles

Author

GUIDED SYSTEMS TECHNOLOGIES MCDONOUGH GA, Corban, J. E., Twigg, Shannon, Ries, Tobias, Yang, Bong-Jun, Johnson, Eric, Calise, Anthony, GUIDED SYSTEMS TECHNOLOGIES MCDONOUGH GA, Corban, J. E., Twigg, Shannon, Ries, Tobias, Yang, Bong-Jun, Johnson, Eric, and Calise, Anthony

Abstract

Successful operation of next-generation unmanned air vehicles will demand a high level of autonomy. Autonomous low-level operation in a complex environment dictates a need for onboard, robust, reliable and efficient trajectory optimization. In this report, we develop and demonstrate an innovative combination of traditional analytical and numerical solution procedures to produce efficient, robust and reliable means for nonlinear flight path optimization in the presence of time-varying obstacles and threats. The trajectory generation problem is first formulated as an optimization problem using reduced-order dynamics that result from the natural time-scale separation that exists in the aircraft dynamics. Terrain information is incorporated directly into the formulation of the reduced-order dynamics, which significantly reduces the computational load and leads to a path planning solution that can be implemented in real-time. Various cases of terrain, pop-up obstacles/threats, and targets are simulated. A representative optimal trajectory is generated with in a high fidelity full-order nonlinear aircraft dynamics and compared with a solution obtained from a reduced-order optimization. The developed algorithm is flight demonstrated with a fixed-wing unmanned aircraft test-bed in which a neural network-based adaptive autopilot is integrated with the on-line trajectory optimization algorithm., Prepared in cooperation with with the Georgia Institute of Technology and the University of Stuttgart. The original document contains color images.

Published
2007

37. [A case of spontaneous biloma complicated with choledocholithiasis and chronic cholecystitis].

Author

Ahn YH, Kim TH, Yang BJ, Oh HJ, Cho EY, Sim MR, Kim YS, Sohn YW, Choi CS, Choi SC, Nah YH, Kim HW, and Kim SW

Subjects
Aged, Cholecystitis diagnosis, Choledocholithiasis diagnosis, Humans, Male, Bile, Cholecystitis complications, Choledocholithiasis complications
Abstract

A biloma is an encapsulated bile collection outside the biliary tree. Most cases of biloma are caused by iatrogenic injury or trauma. Intrahepatic rupture of the biliary tree due to nontraumatic cause is a rare event. A 68- year-old man was admitted because of abdominal pain and fever. He had no past history of abdominal surgery, instrumentation or trauma. Computed tomography (CT) scan and magnetic resonance cholangiopancreatography (MRCP) demonstrated a large subcapsular fluid collection in the right liver associated with choledocholithiasis and cholecystitis. Biloma was confirmed by sono-guided percutaneous needle aspiration and was drained through a pigtail catheter. After the successful treatment by percutaneous drainage and endoscopic sphincterotomy, the patient recovered. Here, we report an uncommon case of spontaneous biloma formation in association with choledocholithiasis with a review of literatures.

Published
2005

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