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Soft-in-plane rotor systems are susceptible to a self-induced vibration phenomenon called ground resonance. This dynamic instability results from lag motions of the rotor blades coupling with airframe degrees of freedom, while the helicopter is in ground contact. As an addition to slope landing studies in the past and investigations of non-linear l...
Citations
... PCM has been applied in many contact-critical MBS applications, for example, in the biomedical field [34], aerospace engineering [35][36][37], aeronautical applications [38] and transportation systems [39]. In the previous applications, the relative velocity between contacting bodies has been low compared to bearings with typical rotational speeds. ...
Rolling bearings are a leading cause of equipment breakdowns in electrical machines, underscoring the significance of predictive maintenance strategies. However, the given methods require high-quality big data, which is challenging to acquire, especially for faulty cases. Simulation models offer an alternative by generating large data sets to complement experimental data. However, bearings involve complex contact-related phenomena, such as slipping and clearance. Therefore, generating realistic data comparable to the real-world necessitates accuracy. Our study presents a multibody simulation system of a motor bearing, incorporating a geometry-based polygonal contact method (PCM), which accurately captures nonlinear bearing dynamics and allows for the simulation of various contact geometries. We introduce a systematic approach to adjust the PCM contact properties for rolling bearings, referencing the well-established Hertzian theory. Both healthy and faulty bearings with a local outer ring fault were simulated. The simulated output was a relative shaft displacement, experimentally validated using a capacitive sensor. Our model successfully demonstrates the potential to employ geometry-based contacts for generating realistic data on faulty bearings with the aim of predictive maintenance.
... PCM has been applied in many contact-critical MBS applications, for example, in the biomedical field [33], aerospace engineering [34,35,36], aeronautical applications [37] and transportation systems [38]. Nonetheless, in the previous applications, the relative velocity between contacting bodies is low compared to bearings with high rotational speeds. ...
... 2), (Ref. 3). In such landings only partial skid contact can occur and influences the dynamic stability of the helicopter. ...
... Based on the work in (Ref. 3) these counteracting effects have to be studied in greater detail. If ground resonance occurs, a pilot is advised to perform immediate take-off and abort the landing, which can be unacceptable in certain mission profiles like rescue operations. ...
... Dedicated models for the investigation of the influence of contact area and different contact models were elaborated in a previous CEAS publication by the authors (Ref. 3). These models allow the detailed simulation of time-variant contact conditions, including damping and friction effects. ...
Soft-in-plane rotor systems are susceptible to a self-induced vibration phenomenon called ground resonance. This dynamic instability results from lag motions of the rotor blades coupling with airframe degrees of freedom while the helicopter is in ground contact. As an addition to previous studies of nonlinear landing gear effects, this work presents the Matrix Pencil Method as a useful additional tool for signal analysis of perturbed nonlinear systems. Contrary to simple logarithmic decrements of decaying time-series, the Matrix Pencil Method allows additional insight into the underlying structure. This makes the method interesting for ground resonance. Additionally, the Lyapunov Exponent Method is introduced to highlight and analyze nonlinear effects in helicopter substitute models.
Landing skids are an important component of uncrewed helicopters. The landing skid acts as a support when the helicopter lands or is parked. This paper examines the effect of landing speed and material selection on the safety factor of uncrewed helicopter landing skids using Ansys Workbench. The uncrewed helicopter weighs 100 kg and an impact time of 0.5 seconds. Landing speed variations are 2 m/s, 3 m/s, and 4 m/s. The materials used in the simulation are plastic types, namely ABS, HDPE, Polyamide (PA6), and Polycarbonate (PC). The simulation results show that the ABS and HDPE materials can only withstand impact loads up to a landing speed of 3 m/s because they have a safety factor of 3.57 and 3.69, respectively. Meanwhile, Polyamide (PA6) and Polycarbonate (PC) can withstand impact loads up to a landing speed of 4 m/s because they have a safety factor of 4.19 and 6.03, respectively.
