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MESA LAB
Indirect Approach for Closed-loop System
Identification with Fractional Models
Tiebiao ZhaoMESA (Mechatronics, Embedded Systems and Automation)LAB
School of Engineering,University of California, Merced
E: [email protected] Phone: 209-2015212
June 30, 2014. Monday 4:00-6:00 PMApplied Fractional Calculus Workshop Series @ MESA Lab @ UCMerced
MESA LAB
Limitations of Open-loop System Identification
• Unstable open-loop system• Subject to significant drift in open-loop operation• The production recommendation do not allow the
regulators to be removed
06/16/2014 AFC Workshop Series @ MESALAB @ UCMerced
MESA LAB
Identifying a closed-loop SISO
• Indirect approach• Direct approach• Joint input/output approach
06/16/2014 AFC Workshop Series @ MESALAB @ UCMerced
MESA LAB
Assumption
• All differentiation orders are supposed known a priori.
• Only the coefficients of the closed-loop fractional transfer function are estimated.
06/16/2014 AFC Workshop Series @ MESALAB @ UCMerced
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MESA LAB
Proposed Method
• Indirect approach
• A linear transformation is applied to the input and output signals to avoid the noise amplification.
06/16/2014 AFC Workshop Series @ MESALAB @ UCMerced
MESA LAB
Closed-loop parameter estimation
• Discretization and linearization• Parameter estimation using ordinary least squares
algorithm (OLS)• Parameter estimation using recursive least squares
algorithm (RLS)• The Iterative Least Squares (IOLS and IRLS)
06/16/2014 AFC Workshop Series @ MESALAB @ UCMerced
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MESA LAB
06/16/2014 AFC Workshop Series @ MESALAB @ UCMerced
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MESA LAB
06/16/2014 AFC Workshop Series @ MESALAB @ UCMerced
MESA LAB
Open-loop Parameter Calculation
06/16/2014 AFC Workshop Series @ MESALAB @ UCMerced
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MESA LAB
Results
• Pseudo random binary sequence (PRBS) applied to the closed-loop system
• Output corrupted by an additive gaussien white noise
06/16/2014 AFC Workshop Series @ MESALAB @ UCMerced
MESA LAB
Remarks
• The results are biased at high levels of SNR. Future method like instrumental variable method.
• How to identify fractional orders in closed-loop systems?
• Is it possible to apply this method to obtain the parameters for online-tuning of the controllers?
06/16/2014 AFC Workshop Series @ MESALAB @ UCMerced
MESA LAB
Combined Fractional Feedback-Feedforward
Controller Design for Electrical Drives
Tiebiao ZhaoMESA (Mechatronics, Embedded Systems and Automation)LAB
School of Engineering,University of California, Merced
E: [email protected] Phone: 209-2015212
June 30, 2014. Monday 4:00-6:00 PMApplied Fractional Calculus Workshop Series @ MESA Lab @ UCMerced
MESA LAB
Scheme of the Speed Control System
06/16/2014 AFC Workshop Series @ MESALAB @ UCMerced
Set-point filter
Fractional PI
Decoupling network
MESA LAB
Position and speed control of DC-motor
06/16/2014 AFC Workshop Series @ MESALAB @ UCMerced
Speed
Position
MESA LAB
06/16/2014 AFC Workshop Series @ MESALAB @ UCMerced
Unfiltered responseResponse with integer filtersFractional filters
MESA LAB
Remarks
• Apply this method in UAV including fractional PID and fractional feed-forward set-point filter
06/16/2014 AFC Workshop Series @ MESALAB @ UCMerced
