Incipient faults are difficult to detect in plant-wide processes compared to conventional faults due to the lack of distinctive features.An incipient fault detection method based on multiple subspace weighted moving window principal component analysis(PCA)was proposed by shifting the detection perspective from the global to the local to improve the detection rate and sensitivity of incipient faults in plant-wide processes.Process variables were partitioned into different subspaces using a two-layer subspace partitioning method that combines process knowledge and data-driven approaches.A weighted moving window was used to increase the offset of incipient faults,while a local outlier factor(LOF)algorithm was introduced into PCA to further focus on the local features of the data to model fault detection in each subspace.The monitoring results in each subspace were fused with information by the Bayesian inference fusion method to obtain distributed monitoring results.The proposed method was validated by industrial examples,and the results showed that the method effectively improved the accuracy and detection speed of incipient fault detection in plant-wide processes.
This paper addresses the robust control scheme for electrohydraulic servo systems (EHSS) with system uncertainties by utilizing a novel extended sliding mode observer (ESMO). The state-space model of the EHSS is derived by considering system uncertainties. The ESMO with only the displacement feedback signal is employed to estimate both the system full-state and the unmodelled system uncertainties. What’s more, with estimation values from the ESMO, a robust control scheme (RCS) is addressed in detail for the EHSS by employing the multiple-surface sliding control (MSSC) architecture. In addition, three proper boundary layers are properly employed to suppress the chattering phenomenon in the control input so that the controller can achieve a smooth sliding manifold. Subsequently, a proper Lyapunov function is defined to prove the stability of the closed-loop. Comparative simulation and experimental results prove the efficiency of the proposed control methodology.
The influence of fine (ϕ0.11 mm) metallic Z-pin volume fraction and arrangement on the mechanical performance and failure behavior of the open-hole laminates compression was analyzed through open-hole compression test and parametric multi-scale finite element model. Discrete solid element was employed to represent Z-pins, and the 3D Hashin failure criterion was utilized to assess the initial in-plane damage. Then the unstable propagation of kink band was effectively simulated during structural failure. Results showed that the compressive strength of all Z-pinned open-hole laminates was lower than that of specimens without Z-pins. The bridging effect between Z-pins and laminates was enhanced with an increase in Z-pin volume fraction, resulting in increased compressive strength of Z-pinned open-hole laminates. The delaminated area around the hole was suppressed, leading to a maximum reduction of 67% in the damaged area. The variation of Z-pin arrangement did not significantly affect the compression strength of open-hole laminates under the same volume fraction. The maximum relative error between the finite element model simulated results of Z-pinned open-hole laminates and experimental results was 8.6%.
The optimization problem of multi-stage disaster response capacity of road transportation network was analyzed in order to reduce the cost of disaster response for road network and ensure the rapid connectivity of road network. A three-layer planning model for the selection of comprehensive pre-disaster emergency workstations and post-disaster road network recovery decisions was established. The differences in exhaustibility, transportation mode and recovery effect of emergency rescue equipments and logistics support resources were specially considered, and the interdependent relationship between the two was quantitatively modeled. An approximate optimal solution for the model was obtained by combining the bi-level genetic algorithm and the Frank-Wolfe algorithm. The research results show that the optimal decisions can respectively reduce the transportation cost of logistics support resources by 10.96% and the weighted recovery cost by 11.51% compared with the pre-disaster deployment decisions not considering the post-disaster recovery process and the decisions not considering the pre-disaster layout decision of logistics support resources. The quantity of logistics support resources and emergency rescue equipments layout jointly affect the recovery effect of the road network. The impact of increasing the quantity of emergency rescue equipments on the recovery effect will be overestimated if the interdependent relationship between the two is neglected.
Numerical simulation and on-site testing methods were used to analyze the diffusion law of dust and CO during the ventilation process of high-altitude tunnel construction by relying on the Mangkang Mountain Tunnel Project of the Sichuan Tibet Railway in order to analyze the diffusion law of pollutants during the ventilation process of high-altitude tunnel construction. Results show that dust mainly diffuses towards the outside of the tunnel in the form of wall-adhering flow, and it accumulates into ‘dust clusters’ during this process. Dust diffusion is mainly influenced by gravity and causes sedimentation. Excessive wind speed in the tunnel is not conducive to reducing dust mass concentration. CO migrates in the form of ‘air masses’ from the vicinity of the palm face to the entrance of the cave. The volume of CO air masses gradually expands during the migration process, and the mass concentration peak continuously decreases, gradually forming a ‘U-shaped’ distribution trend. The on-site test results of CO mass concentration basically accorded with the numerical simulation results. The CO mass concentration in the tunnel will increase as the altitude increases, and the time it takes for the CO mass concentration at the same location in the tunnel to meet the standard requirements will increase. A formula for calculating the correction coefficient of CO mass concentration during tunnel ventilation was derived based on altitude, which is a good supplement to the altitude correction coefficient of CO in the current specifications.
