Dynamic Modeling and Anti-Disturbing Control of an Electromagnetic MEMS Torsional Micromirror Considering External Vibrations in Vehicular LiDAR

Micromirrors based on micro-electro-mechanical systems (MEMS) technology are widely employed in different areas, such as optical switching and medical scan imaging. As the key component of MEMS LiDAR, electromagnetic MEMS torsional micromirrors have the advantages of small size, a simple structure, and low energy consumption. However, MEMS micromirrors face severe disturbances due to vehicular vibrations in realistic use situations. The paper deals with the precise motion control of MEMS micromirrors, considering external vibration. A dynamic model of MEMS micromirrors, considering the coupling between vibration and torsion, is proposed. The coefficients in the dynamic model were identified using the experimental method. A feedforward sliding mode control method (FSMC) is proposed in this paper. By establishing the dynamic coupling model of electromagnetic MEMS torsional micromirrors, the proposed FSMC is evaluated considering external vibrations, and compared with conventional proportion-integral-derivative (PID) controls in terms of robustness and accuracy. The simulation experiment results indicate that the FSMC controller has certain advantages over a PID controller. This paper revealed the coupling dynamic of MEMS micromirrors, which could be used for a dynamic analysis and a control algorithm design for MEMS micromirrors.

Research on the Vibration Characteristics of a Track’s Structure Considering the Viscoelastic Properties of Recycled Composite Sleepers

In order to investigate the vibration characteristics of a composite sleeper-ballasted track and provide a basis for further popularization, a vehicle–track dynamic coupling model is established and the viscoelastic properties of the composite sleeper are considered. The power flow method is employed to reveal the power flow distribution characteristics of the composite sleeper. The results show that the viscoelastic properties of the composite sleeper have little influence on the rail power and have a greater influence on the power flow of the sleeper and ballast bed in some frequency ranges. The viscoelastic properties of the composite sleeper can effectively improve the calculation accuracy of the track structure’s power flow. Compared with the type-III pre-stressed concrete sleepers widely used in China, composite sleepers consume more energy in the vibration process due to their own physical characteristics, which reduces the power flow transmitted downward and relieves vibration on the ballast bed, especially in the ranges of 80–125 Hz and 250–400 Hz. The temperature change mainly affects the power flow of the composite sleeper in the frequency range above 50 Hz. As the temperature increases, the modulus of the composite sleeper decreases and the vibration reduction effect of the ballast bed is improved.

Dynamic Analysis of Metro Train-Monolithic Bed Track System under Tunnel Differential Settlement

The metro tunnel lines built in a soft soil area may suffer from tunnel differential settlement due to the high compressibility of soft soil, the engineering constructions nearby tunnel lines, and the cyclic load of metro trains. In this paper, a dynamic coupling model for a metro train-monolithic bed track system under tunnel differential settlement is established. A cosine function is introduced to simulate a real settlement curve measured from a metro tunnel in southern China, and the vibration performance of the train-track system under tunnel settlements is investigated in both the time domain and frequency domain. Based on the standards for the train safety and passengers’ comfort, the speed limit for the metro train traveling on a monolithic bed track with different settlement distributions are concluded. The present research could be useful for the operation and maintenance of metro tunnels in soft soil areas.

Dynamic optimization of the rail-crown geometry in the rigid frog area by controlling the position of the wheel-load transition

To improve the stability of a train and reduce its influence on the nose rail when passing a rigid frog, the optimization of the rail-crown geometry in the rigid frog area is proposed in this study by controlling the transition range of the wheel load on the nose-rail head and evaluating it by a wheel–rail dynamic coupling model. The method was verified by studying a Chinese CN60-350-1:12 turnout. Results show that if the wing-rail heightening and nose-rail reduction are small, then the transition section of the wheel load on the nose rail may be close to or smaller than the minimum load-bearing cross section, which will cause damage to the weaker section of the front of the nose rail due to excessive load. If the wing-rail heightening and nose-rail reduction are large, the wheel-load transition section of the nose rail may exceed the extreme transition cross section, which will cause the wheel to hit the nose-rail head or make it difficult to climb the wing rail when the wheel passes through the rigid frog. During the optimization process of the rail-crown geometry in the rigid frog, the reasonable transition range of the nose-rail head can be determined by adjusting the wing-rail heightening and nose-rail reduction, and combined with the wheel–rail dynamics evaluation method, the optimal scheme can be selected to protect the nose rail and improve the running stability of the train.

Dynamic Modeling and Simulation of the Basic Shaft Bearingless Motors

A dynamic coupling model of the bearingless motor is established. This test does some simulations of motor displacement, no load speed and tracking accuracy under certain performance indicators. Analysis and simulation results show that the system has a control strategy of high precision as well as good dynamic and static performance.

Study of Dynamic Analysis Model on Subway Vehicle-Tunnel Vertical Coupled System

In this paper, vehicle systems and track-tunnel system are regarded as an interactional, mutual coupling overall system and the interaction between wheel and rail is regarded as the “ligament” of these two subsystems. The vehicle vibration model and vibration equation are established by considering the body vertical vibration, a suspension of vertical vibration and wheelset vertical vibration. By the displacement compatibility condition of the vehicle and track, integrating the vehicle equations and discretized track-tunnel vibration equation, the dynamic coupling model and the equations that reflect the vehicle-track systematicness is constituted. It provides a reference for the further research of the dynamic analysis of vehicle-tunnel coupled system.