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In order to study the instability mechanism of hydraulic support in downdip and updip coal face, taking the four-leg support type hydraulic support as an example, a stability plane mechanical model of “hydraulic support-shifting ram” in both unloaded and loaded states was established. The discriminant of shifting ram's participation in the mechanical balance of the supportand the stability judgment criteria for the standard form of the critical load of the support were obtained. Theoretical analysis and numerical calculations show that the participation of the shifting ram in the mechanical balance of downdip and updip coal face greatly improves the stability of the support. The force on the shifting ram in the updip face is greater than that in the downdip face, resulting in the phenomenon of the shifting ram force reaching the rated value. The hydraulic support of the downdip coal face has an unstable interval. Building a model based on the support and the shifting ram provides a more comprehensive analytical method for the instability research of high-incline hydraulic supports. The research results can provide theoretical guidance for the stability design of hydraulic supports in inclined and inclined coal mining faces.

Facing the demand of autonomous path correction of the road-header working underground, a control law was designed and simplified based on the position and orientation deviation model of the road-header against its aimed walking trajectory.Reasonable Lyapunov function is constructed to prove the convergence of the position and orientation deviation that resulted from the designed control law.Based on a certain real time position and orientation detection strategy for the road-header, the possible errors exist during posture adjustments are summarized and classified into two parts: one is the main execution error of the road-header and it is presented by the slip rate of tracks; the other is the main observation error and it is identified as the position and orientation measurement errors.This paper proposed to take advantages of the statistical characteristics of these errors, which is obtained by a certain number of experiments or deductions instead of rigorous theoretical analysis.The SVD-unscented Kalman Filtering is used to modify the commands that are given originally by the controller so as to deduce and reduce the influence of process error and observation error in the process of position and orientation adjusting.The simulation results show that the proposed path tracking control strategy can effectively realize the transition of the road-header to the target roadway in limited adjustment period, and the corresponding recommended speeds of the driving wheels vary continuously and stably in the whole process.The negative influence of process error and observation error is effectively weakened by commands modification based on SVD-unscented Kalman Filtering.The obtained moving trajectory of the road-header coincides with the planned path very well during the adjustment, which is of great repeatability.This proves that the proposed strategy is of great potential to be applied experimentally in underground real road heading scenario.

According to the working characteristics of the underground road-header, path planning and movements scheduling for path correction of the road-header is formulated.The position and orientation errors of the road-header during working are also presented based on its kinematic model.Taking the working speed and turning angular speed as control inputs, the control law is designed and simplified to ensure the convergence of position and orientation errors based on the theory of sliding mode control.The stability of the proposed control system is proved by using the principle of Lyapunov.The corresponding simulations show that the designed tracking control enables the road-header to come back to the aimed path within limited adjusting steps, The whole scheduling scheme introduced for path correction is reasonable and feasible, and can provide a positive foundation for further study of automatic mining in the coal industry.

In order to optimize the energy efficiency of a fixed-wing unmanned aerial vehicle(UAV) mobile relaying system, this paper proposes an energy-efficient flight scheme, where a straight trajectory is used, and the decode-andforward(DF) strategy and the time-division duplex(TDD) mode are employed. With the data received and forwarded at the relay sideseparately, the energy efficient optimization problem is transformed into two sub-problems. An iteration algorithm using the Dinkelbach method optimizes the UAV relay acceleration and figures out the optimal solution of the energy efficiency problem. The effectiveness of the algorithm is verified through numerical simulations.Simulation results show that compared with the traditional UAV relay flight scheme, the proposed scheme can significantly improve the energy efficiency performance. As the distance between the source and destination nodes increases,the performance advantage becomes more evident.

At present, detection error of pitch angle of roadheader is mainly compensated by manually controlling front blade and rear support of roadheader, the compensation range is very limited, and the efficiency, control precision and automation degree are low. In view of the above problem, mathematical model of pitch angle and actuator of boom roadheader were established, and the method was determined that adjusting position and posture of boom roadheader by using PID controller to control displacement of front shovel and rear support of the roadheader. AMESim was used to establish complete hydraulic model of actuator of the roadheader. The AMESim simulation shows that response time of the system is less than 3 s and the control error of hydraulic cylinder displacement is less than 2 mm, so the basic performance of the pitch angle control system is verified. The Simulink simulation results verify that the pitch angle control system has short response time, small tracking error, and good dynamic tracking performance.

In view of problem that it is difficult to extract vibration signal and carry out fault diagnosis of coal mine electromechanical equipment, intrinsically safe mine-used portable vibration recorder was applied to collect vibration signal of shearer cutting unit, and spectrum analysis and Hilbert demodulation technique were used to demodulate fault characteristic frequency of the vibration signal, so as to determine fault location, which provides reliable basis for fault diagnosis and maintenance of shearer.

Vibration monitoring test of underground belt conveyor gear reducer was conducted by use of vibration recorder. Analysis of changing trend and power spectrum of time-domain characteristic index of on-site vibration data indicates that input shaft of the gear reduer has severe wear and gear tooth breakage.Overhaul results verify correctness of the above analysis and validity of the data sampled by the recorder.

In view of problem that vibration signal of underground large equipments is difficult to be collected, a mine-used signal conditioning device of vibration acceleration sensor was designed. It introduced selection design of vibration acceleration sensor, design of power module, exciting circuit and filtering circuit of conditioning board of vibration signal and protection design of the device. The test result validates reliability and practicality of the device.