Effective feedback control requires all state variable information of the system. However, in the translational flexible-link manipulator (TFM) system, it is unrealistic to measure the vibration signals and their time derivative of any points of the TFM by infinite sensors. With the rigid-flexible coupling between the global motion of the rigid base and the elastic vibration of the flexible-link manipulator considered, a two-time scale virtual sensor, which includes the speed observer and the vibration observer, is designed to achieve the estimation for the vibration signals and their time derivative of the TFM, as well as the speed observer and the vibration observer are separately designed for the slow and fast subsystems, which are decomposed from the dynamic model of the TFM by the singular perturbation. Additionally, based on the linear-quadratic differential games, the observer gains of the two-time scale virtual sensor are optimized, which aims to minimize the estimation error while keeping the observer stable. Finally, the numerical calculation and experiment verify the efficiency of the designed two-time scale virtual sensor.

The hazard of stray current attracts more and more attention due to the potential infrastructure failure caused by the electrochemical corrosion. In view of the poor insulation performance and lack of stray current collection system in the metro depot, stray current leakage becomes particularly evident in this area. In order to evaluate the corrosion risk of buried metal pipeline surrounding metro depot, an assessment model for interference scope induced by stray current is proposed in this paper. The distribution of stray current is calculated based on the resistive network by considering different boundary conditions in different areas of metro depot, and the interference scope is assessed by surface potential gradient for corrosion risk of corroded pipeline. Moreover, the characteristics of surface potential gradient distribution in different areas of metro depot and the influence of electrical parameters are analyzed. Finally, the proposed model is verified through CDEGS-based simulation and experimental results.

With the increase in operation time of DC traction systems due to the environment of tunnel and stress rupture, the insulation between the rail and ground inevitably decreases, causing increased stray current leakage. In view of this, we present an analytical and electrochemical study of stray current behavior and its corrosion impact arising from local rail-to-ground insulation damage in DC urban rail systems. A two-layer rail–earth continuous model of stray current distribution is developed (unilateral and bilateral supply cases) using Kirchhoff network formulations with insulation damage boundary conditions. Numerical simulations quantify the effects of damage location and grounding resistance on rail potential shifts, abrupt changes in rail and stray currents, and total leakage. To assess electrochemical consequences for nearby buried pipelines, the electrical model is proposed in this work with an impedance-informed corrosion model and Monte Carlo sampling of operational and electrical uncertainties to estimate dynamic corrosion rates and pitting evolution. The results show that single–point insulation faults shift the rail zero potential toward the fault, leading to instantaneous jumps in leakage and rail currents whose magnitude grows as damaged-point resistance decreases, markedly increasing pipeline corrosion risk. The integrated electrical-electrochemical framework provides a tool for detection, risk assessment, and mitigation planning for stray current-induced pipeline corrosion.

Stray currents pose a significant threat to the structural health and resilience of subway shield tunnels through the destructive effects of electrochemical corrosion, which is broadly recognized as one of the main obstacles to ensuring the sustainability of urban rail transit systems. Environmental humidity can lead to variations in the pore water saturation of concrete structures. In the coupled environment of stray currents and pore water saturation, this condition exacerbates the corrosion of reinforced concrete, shortening its service life and jeopardizing the normal operation of subway systems. Given this, a combined study is carried out to explore the effect of pore water saturation on stray current corrosion of reinforced concrete through FEM-based simulation and experiment tests. The effect of pore water saturation on stray current corrosion is studied by varying applied potential and porosity. The study validates the influence of concrete porosity and voltage on the control ranges of pore water saturation corresponding to the various stages of stray current corrosion in reinforced concrete. Based on the simulation and experimental results, it is concluded that, under the same voltage conditions, an increase in the porosity of the reinforced concrete correlates with a greater severity of corrosion as pore water saturation increases. As the applied voltage increased from 2 V to 10 V, the pore water saturation range for iron oxidation shrank from 0–0.6 to 0–0.4, while the hydrogen evolution range expanded from 0.7–1 to 0.5–1. Pore water saturation influences the control mechanisms of electrochemical corrosion at various stages in reinforced concrete. Moreover, under each control mechanism, the control ranges of pore water saturation corresponding to the corrosion stages demonstrate sequential trends of contraction, movement towards lower saturation regions, and expansion as the applied voltage increases. The findings of the study contribute to the understanding of the intrinsic mechanisms underlying the service life extension of buried foundation structures.