In the minimally invasive surgical robot system, there is a kinematic coupling between the yaw joint and the rotating joint of the gripper for the traditional cable-driven surgical instrument, which has an adverse effect on the kinematic accuracy of the surgical instrument. For this reason, a new four-degree-of-freedom cable-driven surgical instrument was proposed. The yaw joint adopted a planetary gear structure, which could achieve kinematic decoupling between the yaw joint and the gripper. Firstly, the kinematic coupling problem of joints in the traditional cable-driven surgical instrument was analyzed. Then, a jaw joint of planetary gear rotation was designed, and the geometric analysis proved that it had very low joint coupling and the forced deformation of the steel cable was very small during the motion. At the same time, the forward kinematics model of the new surgical instrument was constructed by using the standard D-H parameter method, and the closed-form solution of its inverse kinematics was obtained by the analytical method. Finally, the accuracy of the forward and inverse kinematics models was verified by using the Robotics Toolbox and the simulation model built in the Simulink environment of MATLAB software, and the workspace of the surgical instrument was analyzed by using the Monte Carlo method. The simulation results showed that the structure design of the proposed surgical instrument was reliable, the kinematic coupling between the joints was low, and its workspace could meet the requirements of minimally invasive surgery. The research results can provide reference for the structural design and kinematics analysis of flexible cable-driven surgical instruments.

Aiming at the problems of the frequent idler failure of long-haul large belt conveyor, idler replacement work leading to shutdown, and the low efficiency and single equipment of traditional manual idler replacement, a robot that can realize non-stop idler replacement is proposed to improve the idler replacement efficiency by taking the belt conveyor in the main adit of Wangjialing Coal Mine as the research object. The belt lifting mechanism is an important part of idler replacement robot. Based on the functional requirements of the robot and the characteristics of narrow space and large belt load of belt conveyors, a scissor-fork belt lifting mechanism was designed. Firstly, the three-dimensional model of the scissor-fork belt lifting mechanism was constructed by SolidWorks software. After the working load of belt lifting was calculated according to the parameters of the belt conveyor, the force analysis for belt lifting mechanism was carried out. Then, the kinematics simulation analysis for belt lifting mechanism was conducted by SolidWorks Motion module and the statics simulation analysis was carried out by ANSYS Workbench finite element software. Finally, the ground test and underground test were carried out to verify the feasibility of the designed belt lifting mechanism. The ground test results showed that under the load of 20?60 kN, the matching accuracy between the measured and simulated vertical displacement of the belt lifting mechanism was 6%?15%, which verified that the bearing capacity of its main structure met the design requirements. The underground test results proved the rationality and reliability of the belt lifting mechanism design. The bearing capacity and lifting height of the scissor-fork belt lifting mechanism meet the functional requirements of the idler replacement robot, which is a key technical breakthrough to realize the non-stop replacement of idlers for belt conveyors.

Aiming at the problems of inaccurate positioning, low mapping accuracy and error accumulation of robots in complex terrain environments, an autonomous navigation system based on optimized Hector-SLAM (simultaneous localization and mapping) algorithm is designed, which ensures that the robot reaches the target point accurately while avoiding obstacles promptly. Firstly, the bicubic interpolation method was used to replace the original interpolation method to solve the problem of map blurring when the Hector-SLAM algorithm was used to build maps with low-precision lidar data, so as to improve the accuracy of scan matching. Secondly, the extended Kalman filter algorithm was used to fuse the data of odometer and inertial measurement unit, which could improve the positioning accuracy. Thirdly, in view of the problem of motion distortion caused by the inability to obtain instantaneous laser point data and the continuous movement of robot, the odometer auxiliary method and PL-ICP (point to line iterative closest points) registration method were combined to realize the correction of motion distortion. At the same time, the tilt angle threshold was set to eliminate the map ghosting, and the optimal path was planned by using A* algorithm and dynamic window approach. Finally, taking AGV (automated guided vehicle) as an example, the mapping experiments and autonomous navigation experiments were carried out in actual scenarios. The results showed that the average mapping relative error of the optimized autonomous navigation system was about 0.44%, and the minimum mapping error was 0.236 m, which was 0.041 m less than that before optimization. It effectively solved the problem of unclear mapping caused by error accumulation and motion distortion, and enhanced the adaptability of AGV in complex terrain environment, so as to achieve high-precision positioning. The research results have certain theoretical and engineering significance for improving the autonomous navigation ability of mobile robots in indoor multi-obstacle environment.

In response to the issue of target disappearing when a mobile robot is following a target, a robot target following system based on visual tracking and autonomous navigation is proposed. The robot following problem was divided into two cases: regular following when the target was within the robot's field of view, and autonomous navigation after the target disappeared. For the former case, the target's motion state was predicted using a Kalman filter, appearance features were extracted using a pedestrian re-identification network, and target tracking was performed by fusing motion information and appearance features using data association fusion. Servo control was then applied for following the target. For the latter case, an autonomous navigation algorithm was adopted based on the relative position between the historical target and the robot. The robot moved to the history position of the target and searched the target, aiming to increase the success rate of the target following. Evaluations were conducted on the OTB100 benchmark dataset and a target following test dataset which was in robot application scenarios. Experiments were performed on a mobile robot platform. The results showed that the robot could follow the target in the environment with different lighting conditions and more background pedestrians, which verified the robustness and effectiveness of the proposed algorithm, and it could meet the real-time requirement. The research results can provide reference for research on the problem of robot refollowing after the target disappears.

The adaptive crossover operators and mutation operators were introduced to integrate the improved jump point search (JPS) algorithm with the adaptive genetic algorithm, solving the problems of multiple inflection points, susceptibility to getting stuck in local optima, large number of iterations, and long optimization time in the optimal path analysis of genetic algorithm. The jump point search-genetic (JPSG) algorithm was obtained. JPSG algorithm used the efficient local search ability of JPS algorithm to improve the overall search ability and accelerate the overall convergence trend of the algorithm. The global search capability of improved genetic algorithm was used to change the state that JPS algorithm could not resolve the optimal path under complex obstacles, and improved the adaptability of the algorithm to dynamic environment. The path planning simulation in the grid matrix shows that compared with improved genetic algorithm and traditional genetic algorithm, JPSG algorithm can effectively shorten the optimization execution time, improve the optimization accuracy and reduce the operation execution times, and has obvious advantages in stability, accuracy and rapidity.

Aiming at the problems of rapidly-exploring random tree (RRT) algorithm in obstacle avoidance path planning, such as weak adaptability to maps, poor sampling quality, many invalid nodes, long planning time and poor path quality, an improved RRT algorithm was proposed. Firstly, on the basis of the traditional RRT algorithm, the map complexity evaluation strategy was used to calculate the appropriate step size and bias probability, so as to realize the self-adaptation to different maps. Then, through the dynamic update strategy of sampling area, the random tree was sampled in the effective area to ensure the positive growth. After the sampling area was determined, the sampling point optimization strategy was adopted to improve the effectiveness of sampling points and make the random tree grow near the target points. Finally, the node reconnection strategy was used to optimize the planned initial obstacle avoidance path, and an obstacle avoidance path with fewer bending times was obtained. The feasibility of the improved RRT algorithm was verified in Python and MATLAB environments. The results showed that the improved RRT algorithm could quickly plan a collision-free high-quality path for maps with different complexity and when applied to robotic arms. The research results can provide reference for improving efficiency of robot obstacle avoidance path planning.

Aiming at the problems of slow response speed of negative flow excavator actuator and low energy utilization rate of control by different working conditions, a phased control strategy for electrically controlled positive flow excavator was proposed. The working cycle of excavator was divided into four stages: excavation stage, full load return stage, unloading stage and no-load return stage. The co-simulation model of electrically controlled positive flow excavator was built based on AMESim and Simulink software. Its hydraulic system adopted hierarchical control method. Among them, the upper-layer controller calculated the flow demand of the excavator actuator according to the electric handle signal, and judged the working stage of the excavator by judging the state of the actuator, so that the base speed of engine was determined. The lower-layer controller received the base speed of engine from the upper-layer controller, and collected the main oil feed pump pressure signal of the excavator. The fuzzy control algorithm was used to correct the engine speed, and the expected engine speed was obtained. At the same time, the sliding mode PID (proportional-integral-derivative) control was used to stabilize the engine speed. Finally, the effectiveness of the proposed control strategy was verified through co-simulation and real vehicle experiments. The simulation results showed that in one working cycle of the positive flow excavator, the engine speed could be stable near the expected speed, and its fuel consumption was 192-220 g/(kW·h). The experiment results showed that compared with the control by different working conditions, the phased control in each stage of a working cycle of the excavator could ensure that the engine worked in the economic fuel consumption zone. The proposed method provides a new direction and reference for the control research of electronically controlled positive flow excavators.

In view of the problems of parts damage and stability reduction caused by a large amount of vibration during roadheader cutting, the vibration characteristics of the new vertical-axis roadheader was analyzed and predicted based on the longitudinal cutting condition. Firstly, the force on the cutting head of the roadheader was analyzed, and the force on the track was analyzed by Bekker subsidence theory. Then, taking the contact force between track and bottom plate and the cutting load as external excitation, the longitudinal nonlinear dynamics model of roadheader was established by using Lagrange equation. Next, based on the Runge-Kutta variable step size algorithm, the dynamics model of roadheader was solved using MATLAB software, and the solution results were compared with experimental results to verify the correctness of the dynamics model. Finally, the dynamics model was used to predict the vibration displacement of key parts of the roadheader under different stabilizing mechanism stiffness. The results showed that the vibration of the whole roadheader was in a chaotic state under the combined influence of multiple external excitation. The roll vibration displacement was small, and the pitch vibration was dominant. With the increasing of the stabilizing mechanism stiffness, the vibration displacement of key parts of the roadheader showed a significant decreasing trend. When the stiffness of the stabilizing mechanism increased to 3 times of the initial stiffness, the vibration displacement of the roadheader body decreased by 29%, the vibration displacement of the cutting arm decreased by 22%, and the vibration displacement of the cutting head decreased by 20%. The research results prove that the vibration response of roadheader can be reduced effectively by increasing the stiffness of stabilizing mechanism, which provides theoretical basis for the stability improvement and structural optimization of roadheader.

Clearance is one of the key factors in evaluating the accuracy and quality of rolling bearings. Scientific and reasonable selection of clearance is conducive to increasing bearing life, while traditional methods for determining clearance based on engineering experience often lack theoretical basis and reliability. Therefore, a reliability design method for radial clearance of rolling bearing based on stress-strength interference model was proposed. Firstly, the original radial clearance and failed radial clearance of the bearing were regarded as random variables, and a two-dimensional random interference model of the bearing was constructed; secondly, according to the original radial clearance and failed radial clearance of bearing with normal, lognormal, exponential and Weibull distributions commonly used in engineering, the analytical formula for solving the reliability of rolling bearing and the confidence interval of bearing radial clearance under given reliability were derived; finally, the obtained confidence interval of 16004 deep groove ball bearing radial clearance was compared with that of the current national standard, and the effectiveness and applicability of the proposed method were verified. The results showed that the confidence interval of radial clearance of rolling bearing designed by the proposed method met the national standard and was more reasonable and reliable. The confidence interval of radial clearance under any reliability could be designed, which provided theoretical support for the design and optimization of rolling bearings.

Hammer wear failure is a common failure mode of hammer rotors. A coupling method of CFD (computational fluid dynamics), DEM (discrete element method ) and Archard wear model was used to numerically analyze the hammer wear process to explore the hammer wear law and analyze the reliability of hammer wear failure.The hammer cumulative wear curve of was fitted and the mathematical model of the hammer cumulative wear was established by using the partial least squares method. The dynamic reliability during the hammer wear process was calculated and analyzed based on the stress-strength interference model and the Monte Carlo method. The results showed that the hammer cumulative wear increased linearly with time. The hammer cumulative wear was calculated to be 16.09 mm by using the mathematical model, and the relative error between the calculated value and the measured value was 8.76%, which showed that the established model for predicting the hammer cumulative wear was basically accurate. After the working time exceeded 110 h, the wear failure reliability gradually decreased, and when the working time reached the limit of 120 h, the wear failure reliability was 0.94. The research results can provide a reference for the study of hammer wear law and dynamic reliability optimization.

A high-speed train dynamics model was established to study the effect of wheel rail excitation on the temperature distribution of brake discs and the surface wear of brake pads. The vertical and lateral vibration amplitudes of the brake disc under emergency braking conditions were obtained through dynamic simulation. The amplitudes were introduced into the finite element model of the brake disc thermal-mechanical coupling established by the direct coupling method as input condition. The temperature variation law of each node in the radial, axial and circumferential of the brake disc was compared and analyzed under the condition of with or without wheel-rail excitation. The ALE (arbitrary Lagrangian-Eulerian) mesh adaptive processing was performed on the surface of the brake pad based on the finite element model of brake disc thermal-mechanical coupling, combined with Umeshmotion wear subroutine, the calculation of the surface wear depth of the brake pad was realized. The influence of with or without wheel-rail excitation on the wear depth of the surface of the brake pad was compared and analyzed. The simulation results show that compared with no wheel-rail excitation, the temperature of radial, axial and circumferential nodes of brake disc decreases under wheel-rail excitation, and the circumferential nodes reach the highest temperature at the same time, and the time for radial and axial nodes to reach the highest temperature is shortened. Under the wheel-rail excitation, the wear depth of each node in the radial and circumferential of the surface of the brake pad increases, which increases the wear of the brake pad surface and reduces the brake pad service life. The results of the research can provide some reference for more accurate prediction of the service life of the brake pad.

In order to improve the efficiency and accuracy of the design of parallel mechanisms with few degrees of freedom, the theoretical analysis and experimental research were conducted on a self-designed 3-PUU parallel mechanism. Firstly, the degree of freedom of the parallel mechanism was analyzed by using the screw theory and the modified Kutzbach-Grubler formula. At the same time, the forward and inverse kinematics solutions and Jacobian matrix of the parallel mechanism were solved, and its constraint singularity and kinematic singularity were analyzed based on the Jacobian matrix. Then, the workspace of the parallel mechanism was analyzed by using the limit boundary search method, and the global dexterity was constructed by taking the reciprocal of Jacobian matrix condition number as the local dexterity, so as to analyze the kinematic performance of the parallel mechanism. Next, an ADAMS/Simulink co-simulation model of the parallel mechanism was built. Based on the given motion equation of the moving platform, the simulation curves and error curves of the moving platform position were obtained through simulation. Finally, the experimental platform was built by using the parallel mechanism prototype, PC (personal computer), STM32 microcontroller, servo motor and laser tracker, and the position curves of the moving platform were measured. The results showed that the parallel mechanism had a large reachable workspace and good kinematic performance. By comparing theoretical results with simulation results, it could be concluded that the constructed kinematics model of the parallel mechanism was correct. There were some errors between the measured and theoretical values of the moving platform position, mainly due to the mechanical errors of the parallel mechanism and the insufficient precision of the control system. However, the variation trends of the measured curve and the theoretical curve were basically consistent, which further verified the correctness of the kinematics model of the parallel mechanism. The research results can provide reference for the design of parallel mechanisms with few degrees of freedom.

At present, the vibration research for reciprocating pumps mainly focuses on the crankshaft and the crank connecting rod mechanism at the power end, with a lack of research on fluid-induced vibration at the hydraulic end. However, the fluid-induced vibration under ultra-high pressure load will affect the reliability of reciprocating pumps. Therefore, based on UDF (user define function) and Scheme scripting language, a reciprocating pump single-cylinder simulation model that could completely simulate the suction and discharge strokes was established, and the correctness of the simulation model was verified by the theoretical curves of flow and valve disc displacement. At the same time, the changes in fluid excitation force, chamber pressure and valve disc movement over time for a single cylinder of the reciprocating pump under different spring preload force, spring stiffness, limiter height, crank speed and discharge pressure were studied. The results showed that the fluid excitation force at the hydraulic end of reciprocating pump was caused by the instantaneous release of pressure overshoot in the plunger chamber; the maximum fluid excitation force occurred after the suction valve was opened rather than after the discharge valve was opened, and the maximum pressure overshoot and fluid excitation force at the hydraulic end were 6.75 MPa and 15.3 kN, respectively. The analysis method based on reciprocating pump single-cylinder simulation model can predict the fluid excitation force, valve disc movement and working performance of reciprocating pumps, which can effectively reduce the development cycle and test cost of ultra-high pressure reciprocating pumps.

Torque test of the drive shaft is the main means to disassemble the resistance of the vehicle chassis (including tires) and analyze the energy flow. Aiming at the demand of quick test of vehicle drive shaft torque, a test system which could be applied to different vehicle types was developed. Firstly, the overall architecture of the drive shaft torque test system was designed, which included sensing assembly, wireless acquisition assembly and calibration bench, and key hardware was selected; secondly, a sensing component that could achieve wide temperature compensation and axial moment decoupling was designed using biaxial patch bridge technology, and a rechargeable shaft sleeve that could adapt to narrow spaces was developed, which was made by 3D printing technology, and could support testing endurance requirements of over 20 hours and meet the layout, power supply, and thermal radiation resistance requirements of sensing components; then, a fast calibration test bench suitable for large axial angle deformation of the driving shaft after loading was designed; finally, the developed torque test system was calibrated, and road test and drum test were conducted. The results showed that the linearity of the drive shaft torque calibration reached 99.811%, and the test system had good performance and high test accuracy. The designed vehicle drive shaft torque test system has the advantages of fast calibration and test, portability and reusability of key sensing modules, and has high practical application value.