Rotating systems equipped with oil-film bearings are critical and common in many industrial machines. There are various non-random uncertainties in such fluid-lubricated dynamic systems. It is important to quantify the effects of uncertainties without adequate statistical information on the dynamics of rotor-bearing systems. In this paper, a rotor system with oil-film bearings at both ends is investigated considering many interval uncertainties. The rotating system is modeled in a deterministic sense. The Chebyshev interval method is used to track the propagation of different uncertainties. Deviations in the steady state responses, time history, and shaft orbits are calculated and comparatively discussed. Influence patterns of different interval parameters and dispersions in various dynamics are presented in detail. It is found that there can be global and local impacts as well as cumulative effects caused by multi-source uncertainties. The findings of the present study could be helpful for a more insightful dynamic analysis of rotor-bearing systems as well as their optimal design and maintenance.

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The Effects of Interval Uncertainties on Dynamic Characteristics of a Rotor System Supported by Oil-Film Bearings

A new multirotor aerial vehicle with two rotor arms formed in a V-shape configuration is introduced in this paper. To figure out the aerodynamic interference effects between rotors as an implication of the control method, this paper discusses the aerodynamic performance of the V8 Octorotor MAV with different rotor spacing using both experiments and simulations. A hovering experiment platform is applied to obtain the thrust, power consumption and rotational speed. PL (power loading) is promoted to characterize the aerodynamic performance of the V8 Octorotor MAV. The velocity vector, streamline and turbulent vortices’ distribution of the V8 Octorotor MAV are presented as the simulation results, which indicates that turbulence intensity generated by the MAV dissipates faster in a large rotor spacing. Therefore, rotor vibration is reduced with an increased hovering stability, and the power loading is much improved at G3 (1.2D–1.4D–1.6D–1.8D) with a better aerodynamic performance both with a thrust increment and power decrement. 

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Aerodynamic Performance of V8 Octorotor MAV with Different Rotor Configurations in Hover

The traditional dynamic characteristic analysis of the multi-stage centrifugal pump rotor system is developed assuming the bearing structural parameters with constant values. However, the manufacturing errors will cause the structural parameters to vary around their nominal values and then affect the dynamic characteristics of the bearing-rotor system. Thus, this paper proposes a method for analyzing the dynamic characteristics of the bearing-rotor system with uncertain bearing structural parameters. First, dynamic characteristic coefficients of the sliding bearing are identified to establish the dynamic model of the rotor system, and its dynamic characteristics are analyzed through finite element simulations. Next, the sliding bearing structural parameters are taken as the variables to establish an optimization model, which is solved by the improved particle swarming optimization algorithm to obtain the extreme critical speed of the rotor system. A case study was carried out on a multi-stage centrifugal pump. The obtained extreme values of the critical speeds were close to those calculated using the multiple samples generated by the Monte Carlo method, indicating that the proposed method can provide accurate variation ranges of critical speeds efficiently and lay a theoretical basis for selecting robust operational speeds and designing the rotor system of the multi-stage centrifugal pump.

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Dynamic Characteristic Analysis of the Multi-Stage Centrifugal Pump Rotor System with Uncertain Sliding Bearing Structural Parameters

This paper investigates the stabilization problem of a class of fractional order chaotic systems with unknown modeling uncertainties and external perturbations. A fractional nonlinear sliding surface is proposed, and a reaching control law is obtained to guarantee the stability of the fractional chaotic system in finite time with just a single control input. And the simulation results are given to demonstrate the efficacy of the proposed nonlinear sliding mode control method.

Stabilization of a class of fractional order chaotic systems by nonlinear sliding mode

Improved milling stability analysis for chatter-free machining parameters planning using a multi-fidelity surrogate model and transfer learning with limited experimental data

Lijun Lin

Papers

Dynamic Characteristic Analysis of the Multi-Stage Centrifugal Pump Rotor System with Uncertain Sliding Bearing Structural Parameters

Stabilization of a class of fractional order chaotic systems by nonlinear sliding mode

Improved milling stability analysis for chatter-free machining parameters planning using a multi-fidelity surrogate model and transfer learning with limited experimental data