中国铁道科学研究院集团有限公司

In the point cloud coordinate conversion algorithm, the trajectory and attitude are interpolated, and the coordinates are converted according to the joint calibration parameters. In terms of 3D point cloObjective With the expansion of railway operation scale and the increase in service time, the demand for the efficiency of track condition inspection and maintenance has risen remarkably. The traditional manual track inspection or hand-pushed equipment can hardly meet the requirements of modern railways for inspection efficiency and accuracy. Non-contact methods based on on-board dynamic inspection, such as the combination of optical and inertial sensors, can efficiently complete the measurement of track geometric parameters, profiles, and other key indicators. However, the measurement of single sensors (for example, line-structured optical sensors) under dynamic conditions has problems like trajectory distortion, especially the limited accuracy in the direction of rail extension, which becomes a key factor restricting the accuracy of track 3D point cloud construction. Compensating the platform vibration in a high dynamic environment with the position and attitude changes measured by inertia and constructing a real 3D point cloud can enhance the dimension of detection information and have a wide application prospect. Currently, there are no related mature methods and applications for high-precision line structured light 3D point cloud construction. In our study, an inertial trajectory measurement method with the fusion of odometry and IMU is proposed, which has a high short-term accuracy retention ability and improves the accuracy of the 3D point cloud. The point cloud data is applied to the field of track geometric parameter measurement. Based on the point cloud data, the vertical and horizontal 10 m chord measurements, and the level are calculated to realize the application value of the data. Methods To address the above issues, we propose a real-time construction method of track 3D point clouds based on multi-sensor fusion. The multi-sensor fusion point cloud calculation method is shown in Fig. 3. Firstly, we improve the short-term holding accuracy of inertial navigation by optimizing the initial alignment algorithm of the inertial measurement system and the inertial attitude solving algorithm within the framework of extended Kalman filtering. Then, we design the coordinate conversion method of point cloud construction, which converts the point cloud data measured by the line-structured optical sensors to the geographic coordinate system. Finally, the geometric parameters of the track are projected according to the 3D point cloud to achieve the application of the point cloud data. The train cannot start and stop randomly in the actual detection task, so it is necessary to achieve the dynamic and rapid alignment of the attitude. We construct and solve the Wahba equation and optimize the alignment algorithm based on the inertial system. In terms of inertial trajectory solution, the measurement equation is derived based on the specific force equation, which directly observes the misalignment angle and the zero deviation of the plus meter. The measurement equation is derived based on the trajectory recursive equation, which directly observes the misalignment angle, the position error, and the scale coefficient of the odometer. Based on the extended Kalman filter framework, the fusion filtering of the odometer and IMU data is realized. ud data application, a typical application scheme of the track point cloud is introduced, which is the non-contact rapid measurement of track geometric parameters. Results and Discussions The feasibility and accuracy advantages of the method are verified through the special train experiments of the Beijing Circular Railway Test. 1) The heading angle error varies greatly in the initial 500 s, and then gradually stabilizes within 1 degrees . The horizontal attitude angle error is rapidly reduced to below 0.1 degrees within 20 s. The alignment angle error is close to the theoretical one, and the alignment accuracy is close to the theoretical value and can be applied to the actual working conditions of train detection. 2) As shown in Fig. 7, based on the method proposed in our study, the measurement error of the roll angle is within -0.025 degrees - 0.010 degrees , and the measurement error of pitch angle is within +/- 0.01 degrees, which shows high accuracy. As shown in Fig. 8, after accurate calibration, the mounting declination in the pitch direction is -0.05 degrees . After considering the installation deviation angle, the accuracy of elevation measurement is obviously improved, and the elevation drift is only 3.92 m when the train travels for 50 km. The elevation error increases the fastest in the section from 439860 to 439944 sin the figure, the cumulative mileage is about 1.6 km, and the elevation error has increased by 1.3 m, which shows that the elevation error is within 0.81% of the cumulative mileage. As shown in Fig. 9, the train travels about 91.7 km cumulatively, the maximum deviation of plane is 290.84 m, and the plane deviation is about 3.17% of the mileage. Based on the comprehensive above data, the accuracy maintenance ability of the inertial measurement method proposed in our study can be illustrated. 3) The measurement repeatability of the vertical 10 m chord measurements is used as an evaluation index, and the repeatability of the method in our study is 0.71 mm. The measured and reference values for vertical and horizontal 10 m chord and level are compared in Fig. 12, and the trend of the waveforms of the two detections is more consistent. The peak values of the measured values and reference values at 11 preset working conditions are shown in Table 1. The maximum error value of the horizontal 10 m chord and level is 0.41 mm, and the maximum error value of the vertical 10 m chord is 1.07 mm. The rail direction and horizontal value better represent the measurement accuracy of the system, and the measurement deviation in the actual unevenness parameter accounts for a maximum of 4.8%, which can satisfy the accuracy requirement of practical application. Conclusions The method proposed in our study does not require static initial alignment and can dynamically complete the attitude initialization and detection tasks with the start and stop of the train, which solves the influence of train scheduling constraints on the detection accuracy. The multi-sensor fusion significantly improves the short-time accuracy retention ability and ensures the stability of local accuracy by reducing the correction frequency. This method has a wide application prospect in the field of railway condition monitoring, which can provide strong technical support for track disease identification and real-time maintenance and provide a guarantee for improving the safety and efficiency of railway operation.

In view of the pollution caused by the large storage of coal gangue and the shortage of natural aggregate in concrete, using coal gangue as coarse aggregate is a reasonable way to solve the above problems. In order to reveal the mechanical properties of coal gangue concrete and promote the application of coal gangue concrete in the field of civil engineering, the mechanical response of coal gangue concrete under multiaxial stress state is studied. Three kinds of concrete mix ratios with coal gangue volume substitution rates of 0, 30% and 50% were designed. 225 specimens were prepared for true triaxial compression test of coal gangue concrete. A total of 20 true triaxial compressive stress ratios, including four minimum principal stress ratios (σ1/σ3 = 0.05, 0.08, 0.13, and 0.16) and five Lode angles (θ = 0°, 15°, 30°, 45°, and 60°) were designed in the experiments. The failure modes, strength characteristics and triaxial compression strength improvement of concrete with different coal gangue replacement rates under different stress ratios were compared and analyzed, based on the triaxial compression test results of coal gangue concrete, a multi-axial strength failure criterion considering the replacement rate of coal gangue was established. The results show that the multiaxial failure modes present four types (Cylindrical failure mode, Slice shape failure mode, Oblique shear failure mode, Extrusion fluid failure mode) with the change of stress ratio, and have little correlation with the replacement rate of coal gangue. With the increase of σ2/σ3, the compressive strength increases first and then decreases, and the maximum value is at θ = 30°. When σ1/σ3 is small, the effect of σ2/σ3 on the triaxial compressive strength is not obvious. The larger the σ1/σ3 is, the more significant the effect of σ2/σ3 on the triaxial compressive strength is. The higher the replacement rate of coal gangue, the lower the triaxial compressive strength, and the greater the σ1/σ3, the more obvious the strength decrease, when σ1/σ3 is small, there is little difference in the improvement degree of triaxial compressive strength between coal gangue concrete and ordinary concrete. When σ1/σ3 is large, the improvement degree of strength of coal gangue concrete is significantly lower than that of ordinary concrete. The established failure criterion considering the replacement rate of coal gangue is well fitted with the triaxial compression test results of concrete. It can correctly reflect the influence of coal gangue coarse aggregate on the multiaxial mechanical properties of concrete, and can be used to predict the multiaxial strength of coal gangue concrete with different coal gangue replacement rates and different stress ratios. The research results can provide data reference for the practical engineering application of coal gangue concrete, in order to realize the solid waste utilization of coal gangue.

[Objective]The architecture of traditional urban rail transit train control system faces challenges such as com-plex train network topology and wiring,increased delays in subsystem interactions,and poor coordination in complex con-trol processes.To improve the response speed of traction and braking and achieve integration of control functions,it is urgent to conduct a research on the integrated control architecture and scheme for key train systems.[Method]Based on the prob-lems existing in the traditional train control system architecture,a function-oriented scheme for train integration control system scheme is designed,and the system architecture is optimized;in line with the real-time characteristics of TSN(time-sensitive network),the TCMS(train control and management system)network topology is designed,and the important role of TSN in the integration of key system control is explained;by integra-ting the control functions of key subsystems such as train trac-tion,braking,and network through the integration control unit to,a high degree integration of key system control functions is achieved,thereby simplifying the interaction process;execu-tion-oriented control units with specific functions are designed based on the simplified improvement of the existing traction and braking control units;combined with theoretical analysis,real-vehicle verification is conducted on the train integrated control system.[Result&Conclusion]The integration of key train system control functions can simplify the interaction be-tween subsystems,shorten the control response time,reduce the hard-wired connection of subsystems,and reduce system complexity;the train subsystem controller is only designed for execution and more universal.The train integration control sys-tem improves the coordination of key systems,achieving a fast response control effect.

[Objective]The complexity and variability of friction in urban rail transit train disc brakes make it challeng-ing for traditional static friction models to reveal the dynamic characteristics of the braking system.It is necessary to estab-lish a dynamic friction model to analyze the dynamic character-istics of the disc brake system.[Method]Using the LuGre dynamic friction model,a two-degree-of-freedom dynamic equation for the disc brake system is established and solved by numerical analysis.The vibration response of the brake pad un-der different conditions is obtained,and the influence of the angular velocity,brake pressure and friction factor difference on the brake system stability is analyzed.[Result & Conclu-sion]With the increase of braking angular velocity,the brake system gradually changes from stick-slip vibration to stable vibration.When the angular velocity is higher than the critical angular velocity,the brake system amplitude increases,and the time required for the brake system to enter into the stable state also increases;as the braking pressure increases,the brake pad transitions from stable motion to stick-slip motion,and the vibration becomes complex and irregular.With the increase of braking pressure,the amplitude of the brake pad gradually in-creases,and the vibration intensity gets greater and greater;the amplitude increases with an increase in the friction coefficient difference.Upon comprehensive analysis,the brake system achieves optimal stability state at a friction coefficient differ-ence of 0.2.

[Objective] In light of the "Four-network Integration" （mainline railway， intercity railway， city railway and urban rail transit） development trend， the interoperation technology of CTCS-2 （China train control system level 2） and CBTC （communication-based train control） is of great significance for promoting regional rail transit integration. Therefore， it is necessary to conduct in-depth research on dual-system on-board technical solutions. [Method] An overall on-board system architecture is proposed based on the principle of "independent core safety devices， shared auxiliary equipment". The on-board ATP （automatic train protection） host devices for CTCS-2 and CBTC are set up independently to ensure safety， while ATO （automatic train operation）， DMI （driver-machine interface）， BTM （balise transmission module）， wireless communication units， and sensors are shared to enhance equipment reuse rate and reduce procurement cost. An innovative on-board ATP output switching unit is designed， employing two main control relays to effectively avoid time gaps in the switching process， and enabling seamless system transitions during train operation while ensuring the safety of ATP output commands. A detailed switching scheme for on-board equipment is developed， defining the switching procedures under different systems and the coordination mechanisms among various devices. A full-scale verification of the switching functionality is conducted in laboratory simulation environment. [Result & Conclusion] The designed on-board equipment architecture， output switching unit， and system switching scheme are rational and effective. During system switching， the train operation remains stable， and the speed curve is smooth and continuous， successfully achieving the design objectives and laying a solid technical foundation for subsequent engineering applications.