REAL TIME FRF ESTIMATION BASED ON ACCELERATION RESPONSE MODEL

Date

2026-9-04

Author

Kaçan, Samet Can

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This paper presents real-time methodology for FRF estimation during milling operations. Unlike conventional offline Experimental Modal Analysis (EMA) and Operational Modal Analysis (OMA) methods, the proposed approach enables online tracking of time-varying modal parameters without requiring external excitation and forcemeasurement. It is proposed to utilize the acceleration measurements occurring between two consecutive tooth-workpiece engagements, for that purpose an EKF, based on the free vibration response model is constructed. Then, the stiffness values are found from estimated modal amplitudes with the known analytical acceleration response derived with Laplace transform from unique convolution based force model. The complete framework consists of four stages: (i) recursive estimation of dominant modal parameters—natural frequency, damping ratio, and modal amplitudes using the EKF; (ii) adaptive engagement detection through thresholding; (iii) post-smoothing of the estimated modal parameters via moving median and Kalman filtering to suppress Bernoulli and Gaussian noise; and (iv) stiffness estimation with Kalman Filter, based on decaying function envelopes. Estimating modal constants of each mode, total FRF estimation is completed. The proposed method is experimentally validated on a thin wall cantilever workpiece during end-milling where results are compared with conventional hammer-test EMA results. The identified modal parameters closely match the EMA results demonstrating the method’s potential in monitoring machining processes.

Subject Keywords

Real-Time, Kalman Filtering, Milling Dynamics, FRF, Online Modal Identification

URI

https://hdl.handle.net/11511/120721

Collections

Graduate School of Natural and Applied Sciences, Thesis