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Calibration, Characterization, and Linear Quadratic Gaussian Estimation of Sensor Feedback Signals for a Novel Ocean Wave Energy Linear Test Bed. M.S. Thesis Defense for Christopher A. Haller Electrical Engineering and Computer Science Major Advisor: Dr. Ted Brekken Oregon State University.
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Calibration, Characterization, and Linear Quadratic Gaussian Estimation of Sensor Feedback Signals for a Novel Ocean Wave Energy Linear Test Bed M.S. Thesis Defense for Christopher A. Haller Electrical Engineering and Computer Science Major Advisor: Dr. Ted Brekken Oregon State University. 2010 June10th
C.C.L.Q.G.E.S.F.S.N.O.W.E.L.T.B. - Agenda • Background • Load Cell Calibration • Kalman Filtration [7] [8]
Background • Load Cell Calibration • Kalman Filtration [7] [8]
Ocean Testing [1]
OSU Wave Energy Linear Test Bed • Tests ocean wave energy generators by creating relative linear motion between the center spar and surrounding float. • Specifications[1]: • 10kW with a 50% efficient device, and up to 19kW @ 95% efficiency • 1m/sec @ 20,000 N Thrust (4500 lbf) • 2m/sec @ 10,000 N Thrust (2250 lbf) • Modes: Point-Point (fixed or captured position//wave profile vs. time)& Force (load cell feedback) • 2m relative motion/stroke (6.5 feet) • Upper & Lower Gimbal mounting • (for alignment variation) • 16.5ft tall x 10.5ft wide x 8.5ft deep [7]
Force Control Scheme • Analog position command signal sent to Linear Test Bed. • Analog feedback signals may be used to control force applied by LTB. Position Command Position Feedback Velocity Feedback Acceleration Feedback Force Feedback [9],[10],[11] External Control Computer [7] Linear Test Bed (LTB)
Research Focus To Advance the LTB Toward Closed-Loop Force Control • Construct L.Q.G. Estimator (Kalman Filter) to solve feedback noise issues • Develop LTB Calibration Procedure and Assess Force Sensor Accuracy (Load Cells) [8]
Background • Load Cell Calibration • Kalman Filtration [7] [8]
Least Squares Best Fit Lines Left Load Cell Right Load Cell R2 = 0.9999 R2 = 0.9999
Background • Load Cell Calibration • Kalman Filtration [7] [8]
[5],[6][16] The Discrete Kalman Estimator from LTB Transfer Functions A, B, C Find: LTB Noise Analysis R and Q
The Discrete Kalman Estimator [5],[6][16] Correction Prediction Increment Time Start Observer Gain Prior State Estimate State Estimate Prior Error Covariance Error Covariance
Step #1 for Construction of Kalman Estimator for LTB Find: A, B, C from LTB Transfer Functions
Step #2 for Construction of Kalman Estimator for LTB Find: R from LTB Noise Analysis
System Noise Analysis Covariance[4]:
Position Results Simulated Wave Data File [14]
Position Results – Close Up Simulated Wave Data File [14]
Velocity Results – Close Up Simulated Wave Data File [14]
Force and Acceleration Simulated Wave Data File [14]
References [8] [1] “Wave Energy Opportunities and Developments,” [Online]. Available: http://eecs.oregonstate.edu/wesrf/projects/images/Wave%20Energy_Final.ppt. [Accessed: April 19, 2010]. [2] M. H. Patel and J. A. Witz, Compliant Offshore Structures. London: Butterworth-Heinemann Ltd., 1991. [3] M. S. Grewal and A. P. Andrews, Kalman Filtering: Theory and Practice. United States: Prentice-Hall, Inc., 1993. [4] D. C. Montgomery and G. C. Runger, Applied Statistics and Probability for Engineers. United States: John Wiley & Sons, Inc., 1999. [5] Stefani, Savant, Shahian, and Hostetter, Design of Feedback Control Systems. United States: Saunders College Publishing, 1994. [6] “Kalman” [Online]. Available: http://www.mathworks.com/access/helpdesk/help/toolbox/control/ref/kalman.html. [Accessed: April 20, 2010]. [7] “Linear Test Bed Pictures” [Image] provided by Ean Amon. May 2010. [8] Interface-Force Inc. Load Cell [Online Image]. Available: http://www.interfaceforce.com/includes/thumb.php?resize=275&img=images%2Floadcells%2FLOW_PROFa_000.jpg. [Accessed: April 20, 2010]. [9] Dell Monitor[Online Image]. Available: http://www.theinquirer.net/img/1177/dell_monitor.jpg. [Accessed: April 23, 2010]. [10] Industrial Computer [Online Image]. Available: http://img.diytrade.com/cdimg/960066/9655368/0/1247037540/Rack_Mount_Chassis_industrial_Computer_Case_4u450AT.jpg. [Accessed: April 23, 2010]. [11] Ocean Wave [Online Image]. Available: http://megroberts.files.wordpress.com/2008/12/ocean-wave-jj-001.jpg. [Accessed: April 23, 2010]. [12] Strain Gauge States [Online Image]. Available: http://http://en.wikipedia.org/wiki/Strain_gauge. [Accessed: June 3, 2010]. [13] WESRF Lab [Image]. WESRF Share Drive [Accessed: June 7, 2010]. [14] D. Elwood, \Simulated Ocean Wave Data Files," 2010, Oregon State University. [15] P. Hogan, Thesis. 2007, Oregon State University. [16] Kalman Filter [Website]. Available :http://bilgin.esme.org/BitsBytes/KalmanFilterforDummies. [Accessed: June 9, 2010].
Load Cell Composition [8] [12] • Two load cells directly coupled to buoy. • Each load cell is rated for 5000 lb-f in tension or compression. [12] [12]
Typical Calibration Test [8] • Measure zero point (no weight). • Measure five tension points to capacity. • Measure one return point (25% of capacity). • Measure zero point (no weight). • Measure five compression points to capacity. • Measure one return point (25% of capacity). • Measure zero point (no weight).
Tuning the Kalman Filter ωP = 0.8 ωV = 200π ωA = 400π QN = 5000 ωP = 5.35 ωV = 10π ωA = 5π QN = 10 Starting Values Final Values
Mean Squared Error Analysis
Acceleration Results – Close Up Simulated Wave Data File [14]