Torque Reconstruction for Maritime Powertrains Using Trend Filtering

This paper presents a convex optimization approach for the simultaneous reconstruction of unknown input torque and torsional response in the driveline of an azimuth thruster. Accurate estimates of the shaft torque responses are necessary for condition monitoring purposes. Estimating torque responses also enables flexibility in the choice of sensor location, with subsequent potential savings in installation and maintenance costs. It is shown that the unknown inputs and states can be reconstructed using batch torque measurements from a single location in the propulsion line. The estimation problem is formulated as a trend-filtering problem, enforcing the smoothness of input estimates. The performance of the proposed method is evaluated by means of simulations and experiments on a small-scale testbench of a maritime azimuthing thruster. The results show that the torsional response of the propeller shaft can be accurately reconstructed using torque measurements from sensors installed near the driving motor at the opposite end of the driveline.