The occurrence of coal burst in underground coal mines is complex, abrupt, and diverse, and the evaluation and prediction of coal burst hazard is the premise of effective prevention and control of coal burst. In this study, a coal burst carrier system model under the synergistic action of roof, coal seams, and floor was established, and the evolution of coal burst in underground coal mines was discussed based on the stress-vibration-energy coupling principle. On this basis, an integration method of bursting strain energy and seismic velocity tomography for coal burst assessment was proposed. With the deep and complex panel in a mine as the research object, the coal burst risk of the panel during excavation was evaluated in time and space domains, respectively. Results showed that the bursting strain energy and the active seismic velocity tomography technology can accurately identify both the positive anomalies and the negative anomalies of stress field and energy field in the mining period. Moreover, the method can not only evaluate the coal burst risk of the panel in the temporal domain but also predict the area with potential strong seismic events in the spatial domain. The research conclusions can accurately illustrate the whole complex evolution process of coal burst in underground coal mines.

A true triaxial loading and unloading experiment entailing “y‐direction stress loading, z‐direction stress unloading, and x‐direction displacement fixing” of coal samples was conducted. Through analysis of the stress characteristics, fracture characteristics, and energy evolution in coal samples, the mechanical and coal burst breeding mechanisms of coal samples under true triaxial loading and unloading were revealed. The experiment found that the yield stress and peak stress of coal samples were not only affected by the initial loading and unloading of lateral stress but also had a negative exponential relationship with the ratio of the unloading rate and the loading rate (RURLR), thereby establishing the stress equation of coal samples under a true triaxial loading and unloading. There was a yield turning point in the stress‐time curve of coal samples, and the difference in triaxial stress and acoustic emission before, and after, yield was significant. It was found that a high unloading rate and high initial stress are precursors to coal sample bursting. During loading and unloading, the high‐energy area expanded, but its location was always fixed to within a certain area. The energy in this area was rapidly released to form a burst source when the sample was subjected to high‐speed unloading. The nonbursting coal samples and the burst coal samples showed characteristic slabbing and bursting behaviours, respectively: the former corresponding to the acoustic emission energy value being two orders of magnitude lower than the latter. The research results can provide a reference for the study of mechanical behaviours and coal burst criteria in the rock surrounding a coal roadway excavation.

To study fracture evolution and peak stress in burst risk coal samples (BRCSs) under true triaxial loading and unloading conditions, experimental and numerical research was applied to BRCSs under true triaxial stress paths entailing “x‐direction displacement fixed, y‐direction loading, z‐direction unloading.” Both the experimental and the numerical results demonstrated that the peak stress borne by the BRCSs was not only affected by the initial stress but also had a negative exponential relationship with the ratio of the unloading rate and the loading rate (RURLR); therefore, peak stress equations of BRCSs under true triaxial loading and unloading conditions were established. The triaxial stress‐time curves obtained by experiments and simulations exhibited an “elasticity‐yield‐destruction” phase, and the characteristics of the yield phase were determined by the RURLR. A typical BRCS was selected for velocity tomographic imaging to analyze the fracture evolution characteristics under true triaxial loading and unloading. The results showed that when the BRCS was subjected to a triaxial state of stress, the high‐ and low‐velocity regions existed alternately due to the presence of the crack; during the elastic phase, the crack closed during loading in the previous phase was reopened upon unloading, so that the velocity of the sample decreased and a wide range of low‐velocity regions could be formed; when entering the yield phase, the original crack continued to expand into a hole‐through crack, leading to wider extreme values and ranges of these low‐ and high‐velocity regions; at the breaking phase, multiple microcracks were generated around the hole‐through cracks, decreasing the overall velocity, and showing point distributions characteristics of high‐ and low‐velocity regions. Overall, many low‐velocity regions with similar normal directions to the unloading direction were formed; these correlated well with macrofractures (postfailure).

Aiming at the test safety problems in the early stage of self-driving cars development, firstly the virtual vehicle on-board CAN data acquisition module of the present project was designed based on virtual LabVIEW. Then a wireless remote control system for the self-driving car was constructed, which integrated the built virtual vehicle on-board CAN data acquisition system, the remote real-time image monitoring module and the remote upper computer control module based on ZigBee wireless transmission. It can execute the environmental awareness training and continuous and complex motion manipulation testing of the vehicle without relying on the driver, which can solve the safety problems in the tests of initial development of self-driving cars. Finally, the four-wheel independent steering electric vehicle was used as the self-driving test vehicle, and the wireless remote control system was tested on the double lane change type path and S-type path. During the testing, the self-driving car performed better actions and followed the desired path, which verified the consistency of the test behaviors and the remote control operation instructions.

In this paper, a new method based on the investigation of pole ratio (PR) and rotor poles is proposed for pole-slot combination design of an outer-rotor flux-modulated permanent magnet (OR-FMPM) motor to improve output torque and reduce permanent magnet (PM) eddy current loss. Firstly, through the analytical method, the relationships of the PR and the rotor poles with output torque and PM eddy current loss, respectively, are derived. Then, the performances of topologies with different PRs and rotor poles, respectively, are compared and investigated by finite element analysis (FEA). The result reveals that the PR and the rotor poles significantly influence the performance. Subsequently, the optimal pole-slot is selected for the OR-FMPM motor, and other basic performances are evaluated, including the flux distribution and flux density distribution, no-load back electromotive force (EMF), etc. Finally, the theoretical analysis and the simulation results verify the rationality and effectiveness of the method.