This paper summarizes work done to experimentally characterize the combined actuator/structure/se... more This paper summarizes work done to experimentally characterize the combined actuator/structure/sensor system, and the control system hardware, of the ACES facility at the NASA Marshall Space Flight Center. The input-output frequency response functions of the actuator/structure/sensor system were measured for all analog actuator inputs and sensor outputs. System nonlinearity and time variance, measurements delays, and control hardware sampling delays and alias protection were investigated. Modal models of the system were generated from frequency response function data. State space models are formed from these modal parameters, for use in controller design.
Proceedings of SPIE - The International Society for Optical Engineering
Implementation of Adaptive Modal Space Control (AMSC) is examined. The technique is implemented f... more Implementation of Adaptive Modal Space Control (AMSC) is examined. The technique is implemented for several test cases. First, modal space control is achieved for a dominant mode of a cantilever beam. Second, the effect of actuator location on control performance is studied. Finally, the parameter histories of the adaptive plant model and regulator are examined. The modes of the beam are reasonably well separated with the exception of a pair of modes which approximate the flutter condition of an aircraft wing. This structure has modes of concern from 0-150 Hz, requiring a relatively high-bandwidth (fast) controller. The structure also requires a high channel count sensor array to prevent spatial aliasing of the filtered response and control spillover. The controller demonstrates high bandwidth and good decoupling in the presence of a time varying system. Implementation issues regarding solution of system identification and recursive control law development are examined.
Proceedings of SPIE - The International Society for Optical Engineering
In the production of rolled steel sheet the cold roll mill imparts the final thickness, surface f... more In the production of rolled steel sheet the cold roll mill imparts the final thickness, surface finish and mechanical properties to the product by passing it through a series of highly loaded rollers (roll stands). At the exit to the cold mill the steel sheet is rolled into a coil on a cantilevered takeup roll assembly called the tension reel. As the name implies the tension reel is designed to maintain the sheet under the correct tension as it is being rolled. Tension that is too low or too high can cause surface defects on the steel. A major U.S. steel manufacturer was experiencing large sheet tension variations at the tension reel and high tension reel vibration which was cracking support steel. SDL worked with the steel producer to develop a computer model of the tension reel dynamics to understand the problem. The computer model accurately matched measured data and revealed a surprising cause of the tension variation and vibration.
46th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2010
Defect severity estimation often shows promise in the laboratory; however, due to multiple factor... more Defect severity estimation often shows promise in the laboratory; however, due to multiple factors which affect defect force, masking vibration, and transfer path dynamics, defect severity estimation in deployed systems can be very fragile. Current defect severity estimation techniques rely on defect feature amplitude, which is often more dependent on factors other than the actual defect size. The authors have developed a mechanical waveguide which provides a stable vibration transfer path and avoids masking vibration noise. This enables direct defect force measurement by deconvolution of the transfer path dynamics, providing a “digital” defect size measurement.
Vibration signatures sensed from distant vehicles using laser vibrometry systems provide valuable... more Vibration signatures sensed from distant vehicles using laser vibrometry systems provide valuable information that may be used to help identify key vehicle features such as engine type, engine speed, and number of cylinders. While developing algorithms to blindly extract the aforementioned features from a vehicle's vibration signature, it was shown that detection of engine speed and number of cylinders was more successful when utilizing a priori knowledge of the engine type (gas or diesel piston) and optimizing algorithms for each engine type. In practice, implementing different algorithms based on engine type first requires an algorithm to determine whether a vibration signature was produced by a gas piston or diesel piston engine. This paper provides a general overview of the observed differences between datasets from gas and diesel piston engines, and proceeds to detail the current method of differentiating between the two. To date, research has shown that basic signal processing techniques can be used to distinguish between gas and diesel vibration datasets with reasonable accuracy for piston engines of different configurations running at various speeds.
This paper summarizes work done to experimentally characterize the combined actuator/structure/se... more This paper summarizes work done to experimentally characterize the combined actuator/structure/sensor system, and the control system hardware, of the ACES facility at the NASA Marshall Space Flight Center. The input-output frequency response functions of the actuator/structure/sensor system were measured for all analog actuator inputs and sensor outputs. System nonlinearity and time variance, measurements delays, and control hardware sampling delays and alias protection were investigated. Modal models of the system were generated from frequency response function data. State space models are formed from these modal parameters, for use in controller design.
Proceedings of SPIE - The International Society for Optical Engineering
Implementation of Adaptive Modal Space Control (AMSC) is examined. The technique is implemented f... more Implementation of Adaptive Modal Space Control (AMSC) is examined. The technique is implemented for several test cases. First, modal space control is achieved for a dominant mode of a cantilever beam. Second, the effect of actuator location on control performance is studied. Finally, the parameter histories of the adaptive plant model and regulator are examined. The modes of the beam are reasonably well separated with the exception of a pair of modes which approximate the flutter condition of an aircraft wing. This structure has modes of concern from 0-150 Hz, requiring a relatively high-bandwidth (fast) controller. The structure also requires a high channel count sensor array to prevent spatial aliasing of the filtered response and control spillover. The controller demonstrates high bandwidth and good decoupling in the presence of a time varying system. Implementation issues regarding solution of system identification and recursive control law development are examined.
Proceedings of SPIE - The International Society for Optical Engineering
In the production of rolled steel sheet the cold roll mill imparts the final thickness, surface f... more In the production of rolled steel sheet the cold roll mill imparts the final thickness, surface finish and mechanical properties to the product by passing it through a series of highly loaded rollers (roll stands). At the exit to the cold mill the steel sheet is rolled into a coil on a cantilevered takeup roll assembly called the tension reel. As the name implies the tension reel is designed to maintain the sheet under the correct tension as it is being rolled. Tension that is too low or too high can cause surface defects on the steel. A major U.S. steel manufacturer was experiencing large sheet tension variations at the tension reel and high tension reel vibration which was cracking support steel. SDL worked with the steel producer to develop a computer model of the tension reel dynamics to understand the problem. The computer model accurately matched measured data and revealed a surprising cause of the tension variation and vibration.
46th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2010
Defect severity estimation often shows promise in the laboratory; however, due to multiple factor... more Defect severity estimation often shows promise in the laboratory; however, due to multiple factors which affect defect force, masking vibration, and transfer path dynamics, defect severity estimation in deployed systems can be very fragile. Current defect severity estimation techniques rely on defect feature amplitude, which is often more dependent on factors other than the actual defect size. The authors have developed a mechanical waveguide which provides a stable vibration transfer path and avoids masking vibration noise. This enables direct defect force measurement by deconvolution of the transfer path dynamics, providing a “digital” defect size measurement.
Vibration signatures sensed from distant vehicles using laser vibrometry systems provide valuable... more Vibration signatures sensed from distant vehicles using laser vibrometry systems provide valuable information that may be used to help identify key vehicle features such as engine type, engine speed, and number of cylinders. While developing algorithms to blindly extract the aforementioned features from a vehicle's vibration signature, it was shown that detection of engine speed and number of cylinders was more successful when utilizing a priori knowledge of the engine type (gas or diesel piston) and optimizing algorithms for each engine type. In practice, implementing different algorithms based on engine type first requires an algorithm to determine whether a vibration signature was produced by a gas piston or diesel piston engine. This paper provides a general overview of the observed differences between datasets from gas and diesel piston engines, and proceeds to detail the current method of differentiating between the two. To date, research has shown that basic signal processing techniques can be used to distinguish between gas and diesel vibration datasets with reasonable accuracy for piston engines of different configurations running at various speeds.
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Papers by Stuart Shelley