Method for in-situ balancing of rotatives by use of an on-the-fly pulsating material removal process

Abstract

Balancing rotating systems is a challenging task, which requires (dis)assembly of the system to enable mass adjustments; thus the development of a method to balance rotatives in-situ (i.e. without disassembly) using pulsed laser ablation (PLA) is a key technology enabler. PLA for in-situ balancing offers inherent advantages of an adjustable frequency (to match that of the rotating part) and variable pulse energy (to control the mass removal). This thesis presents a novel methodology for balancing components in-situ using PLA in a controlled and automated manner. The method utilises a sensor to measure the acceleration of the rigid rotor-bearing system. After signal conditioning using an adaptive peak filter (i.e. an inverted notch filter), a developed peak detection algorithm determines the maxima of the signal to find the angular imbalance position. If corrective action is necessary, PLA occurs. The method accounts for the time delays in the laser system and electronic circuit. Validation on a rotating part showed a PLA targeting accuracy of < 50μm and a precision of < 30μm; the feasibility of the method was confirmed using a simulation and by balancing a rotor with an arbitrary added imbalance. A concept, which was devised to optimise the PLA strategy for removing imbalances, bases on a novel combination of an analytical and machine learning approach. It determines the optimum process parameters of an ablated feature with a specified shape and volume. Additionally, an error budget for the method has been developed. The concept has been validated and shown to be accurate to < 4mg. The error budget could account for variations. It has been shown long features in the circumferential direction of the part increase the material removal rate with only minor increases in the error magnitude. To conclude, a concept for the integration of the two developed models is presented