Because of the potential technical advantages, the contra-rotation technology has become a renewed interest in aviation and other applications. Contra-rotation increases efficiency in comparison with the single-rotor design, but this advantage is not fully harnessed. The axial spacing of two-stage contra-rotating blade rows has a significant impact on a contra-rotating fan/compressor. The results show that with a contra-rotation pattern, the strong unsteadiness of two-stage rotors is caused by the rotor-rotor interaction. The unsteadiness of rotor 1 is caused by the potential disturbance, and the upstream wake leads to the strong unsteadiness of rotor 2. With the increase of axial spacing, the rotor-rotor interaction is weakened, while unsteady features of two-stage rotor blades tend to be consistent. The acoustic and vibration effects of axial spacing are studied. It is found that the axial spacing has great influence of aerodynamic noise. The mean value of sound pressure level decreases by 17.2 dB in total when the axial spacing increased to 1.1 chord from 0.3 chord. For the accuracy of calculation, the scattering effect of the casing wall should be considered in the prediction of the noise. The axial spacing does not have obvious effects on the natural frequencies of the two-stage rotor blades but has certain effect on blade deformation.

Aiming at solving the problems such as long calibration time, low precision, and complex operation in hand-eye calibration of welding robot, an automatic hand-eye calibration algorithm based on linear structured light was proposed to solve the calibration matrix X by using AX=ZB calibration equation. Firstly, a square calibration plate is customized to effectively constrain the structured light. The α-shape algorithm was adopted to extract the contour of the 3D point cloud model of the calibration plate. Secondly, an improved random sampling consistency algorithm which could determine the optimal iterative number was proposed to fit the contour point cloud, the contour point cloud model fitted was obtained. Finally, the 3D coordinates of the target points were determined with the linear structured light to complete the hand-eye calibration. In order to prevent the calibration plate from deviating from the acquisition range of the vision sensor during the calibration process, the distance between the linear structural light and the inner circle in the calibration plate was set to limit the motion range of the robot. In order to eliminate the error transfer of the robot body, an optimal solution of the rotation matrix R and the translation vector t of the calibration data was calculated with the singular value decomposition (SVD) and the least square rigid transpose method. The experimental results show that the calibration accuracy reaches 0.3 mm without compensating the robot body error, and the calibration speed is improved by 36% than the existing automatic calibration method. Therefore, the algorithm proposed can automatically complete the calibration only by establishing the user coordinates in advance, which improves the working accuracy and efficiency of the welding robots greatly.

In order to investigate the essence of sticking for drill rod served in underground coal mine, a comprehensive solution combing finite element analysis with fuzzy proportion–integration–differentiation on the drilling rig is proposed. First, the structure and working mechanism of the drilling rig are studied; then, the static and modal analyses on the drill rod with finite element analysis are performed according to the actual working conditions of the drilling rig. Furthermore, a load-sensing hydraulic power system of the drilling rig is built, and the co-simulation with AMESim and Simulink is performed on the response, overshoot, and vibration, when the hydraulic power is controlled with the conventional control method, proportion–integration–differentiation control method, and fuzzy proportion–integration–differentiation method, respectively. The simulation results show that the strength, stiffness, and vibration frequency of the drilling rig model meet the working requirements, and no resonance occurs; furthermore, the load-sensing hydraulic power system with fuzzy proportion–integration–differentiation method is preferable than the other two control methods.

Drilling rig sticking, which poses great danger for operators in coal mine production, occurs frequently owing to various factors during the process of drilling in underground coal mines. To solve the sticking problem, the hydraulic power of the drilling rig, which has a significant influence on sticking, is studied. The relation between the torque provided by the hydraulic power unit and the torque required is determined. A model of the hydraulic system based on the multi-way valve applied in a typical drilling rig is built using the hydraulic component design of AMESim; then, the hydraulic system model is simulated under similar working condition with actual condition. Subsequently, a theoretical expression is deduced according to hydraulic and mechanical theorems, and a control method based on dynamic performance curves and relation expression (MDPRE) combining system simulation with theoretical expression is proposed. Finally, experiments are conducted 10 times/shifts to validate the MDPRE. The ultimate results show that the solution is viable and effective.

Purpose: This paper aims to propose a conceptual scale model of mobile drilling robot according to the actual drilling rig and working conditions to improve the safety and automation of drilling in tunnel construction and coal mining applications. Design/methodology/approach: A couple of pinion and rack serves as the support mechanism driven by a motor with low rotation speed at high power, and these components are assembled in the center of the robot to tightly fasten the whole body together. The drilling rod and the sleeve are connected through a hole with screw thread so that the rod feeds and rotates simultaneously along with the sleeve. The robot model is automatically controlled by a single-chip microcomputer, and the anti-disturbance circuit is designed as well. A five-step rule obstacle avoidance method is proposed to ensure safe and reliable movement. Findings: The results of simulation experiments on drilling operation do indicate that the mechanism and control method are feasible and effective. Research limitations/implications: The robot is nearly complete but indeed remains only an experimental machine. Originality/value: The design of the mechanism structure for the conceptual robot is novelty. The method of five-step rule obstacle avoidance can improve reliability of obstacle avoidance according to the experimental results, which can meet the requirements of complex working conditions underground coal mine.