Recent Patents on Mechanical Engineering - Volume 13, Issue 2, 2020

Background: China's thin and extremely thin coal seam resources are widely distributed and rich in reserves. These coal seams account for 20% of the recoverable reserves, with 9.83 billion tons of industrial reserves and 6.15 billion tons of recoverable reserves. Objective: Due to the complex geological conditions of the thin coal seam, the plow mining method cannot be effectively popularized, and the drum mining method is difficult to be popularized and applied in small and medium-sized coal mines, so it is necessary to find other more advantageous alternative mining methods. Methods: The equipment integrates mining operations, conveying operations, and supporting operations, and is suitable for mining short and extremely thin coal seam with a height of 0.35m-0.8m and width of 2m-20m. It has the advantages of the low body of the shearer, no additional support on the working face, and small underground space. The mining efficiency of thin coal seam and very thin coal seam can be improved and the mining cost can be reduced. Results: Thin coal seam shear mining combines mining, conveying, and supporting processes together and has the advantages of a low fuselage, no extra support required for the working face, and feasibility in a small underground space. Conclusion: The summarized mining method can improve the mining efficiency of thin and extremely thin coal seams, reduce mining costs, and incorporate green mining practices, which take both mining economy and safety into account.

Background: The legs are important base mechanism and have a key effect on the stability and security of movable offshore platform. In the application field, the work of defects detection is operated in a manual way for offshore platform leg. The main disadvantages of manual inspection can be summarized as follows: high detection cost and risk, low detection coverage and efficiency, etc. Objective: To develop a robot with an inspecting system that can crawl on the inner wall surface of the offshore platform leg, and inspect the surface defects through the inspecting system. Methods: Based on our patented technologies and the application requirements, the telescopic mechanisms, constituted by motor-screw-nut mechanism, are applied to design the body and legs mechanism of the robot. The vacuum sucker groups are applied to design the adsorption mechanism of the robot. The PLC is applied to design the measurement and movement control system. The laser ranging sensors are applied to realize the function of obstacle detection, robot location and pose analysis. The camera and its driving system are applied to design the image acquisition system. The wireless bridge is applied to design the message remote transmission system. Results: Based on the structure characteristic and the defect inspecting requirement of offshore platform leg, the wall crawling robot and its inspecting system are designed in this study. Conclusion: A series of experiments show that the robot and its inspecting system meet the demand of field applications.

Background: Fluid flow in microchannels is restricted to low Reynolds number regimes and hence inducing chaotic mixing in such devices is a major challenge. Over the years, the Immersed Boundary Method (IBM) has proved its ability in handling complex fluid-structure interaction problems. Objectives: Inspired by recent patents in microchannel mixing devices, we study passive mixing effects by performing two-dimensional numerical simulations of wavy wall in channel flow using IBM. Methods: The continuity and Navier-Stokes equations governing the flow are solved by fractional step based finite volume method on a staggered Cartesian grid system. Fluid variables are described by Eulerian coordinates and solid boundary by Lagrangian coordinates. A four-point Dirac delta function is used to couple both the coordinate variables. A momentum forcing term is added to the governing equation in order to impose the no-slip boundary condition between the wavy wall and fluid interface. Results: Parametric study is carried out to analyze the fluid flow characteristics by varying amplitude and wavelength of wavy wall configurations for different Reynolds number. Conclusion: Configurations of wavy wall microchannels having a higher amplitude and lower wavelengths show optimum results for mixing applications.

Background: The power performance of an electric vehicle is the basic parameter. Traditional test equipment, such as the expensive chassis dynamometer, not only increases the cost of testing but also makes it impossible to measure all the performance parameters of an electric vehicle. Objective: A set of convenient, efficient and sensitive power measurement system for electric vehicles is developed to obtain the real-time power changes of hub-motor vehicles under various operating conditions, and the dynamic performance parameters of hub-motor vehicles are obtained through the system. Methods: Firstly, a set of on-board power test system is developed by using virtual instrument (Lab- VIEW). This test system can obtain the power changes of hub-motor vehicles under various operating conditions in real-time and save data in real-time. Then, the driving resistance of hub-motor vehicles is analyzed, and the power performance of hub-motor vehicles is studied in depth. The power testing system is proposed to test the input power of both ends of the driving motor, and the chassis dynamometer is combined to test so that the output efficiency of the driving motor can be easily obtained without disassembly. Finally, this method is used to carry out the road test and obtain the vehicle dynamic performance parameters. Results: The real-time current, voltage and power, maximum power, acceleration time and maximum speed of the vehicle can be obtained accurately by using the power test system in the real road experiment. Conclusion: The maximum power required by the two motors reaches about 9KW, and it takes about 20 seconds to reach the maximum speed. The total power required to maintain the maximum speed is about 7.8kw, and the maximum speed is 62km/h. In this article, various patents have been discussed.

Background: Nutation transmission with conical movable teeth is a patent about a new type of spacial movable tooth drive that was developed based on the bevel planetary gear drive with a difference in the number of small teeth. Objective: The aim of this study was to establish the fractal contact model and calculate the contact strength of the center gear in the nutation transmission with conical movable teeth based on the M-B fractal contact theory and also to demonstrate the validity of the present solution by comparing it with the FEM results and the Hertz contact results. Methods: Based on the fractal theory, the relationship between the loads and the area for the tapered roller teeth in contact with the center disk was obtained, and the four basic parameters were simulated to analyze the effect of the fractal contact model in MATLAB. Results: The accuracy of the fractal contact model was verified using numerical simulation and analysis of the relationship diagram for the real contact area and load and the contact area ratio chart with different parameters. Conclusion: Based on the FEM theory, the Hertz elastic contact theory, and the fractal theory, the tooth surface contact strength of the center disk was compared and analyzed, which enabled us to demonstrate the validity of the present solution, and measures were taken to optimize and improve the followup design of the nutation drive.

Background: The parallel mechanism is widely used in motion simulators, parallel machine tools, medical equipment and other fields. It has advantages of high rigidity, stable structure and high carrying capacity. However, the control strategy and control method are difficult to study because of the complexity of the parallel mechanism system. Objective: The purpose of this paper was to verify the dynamic model of a hydraulic driven 3-DOF parallel mechanism and propose a compound control strategy to broaden the bandwidth of the control system. Methods: The single rigid body dynamic model of the parallel mechanism was established by the Newton Euler method. The feed forward control strategy based on joint space control with inverse kinematic was designed to improve the bandwidth and control precision. The co-simulation method based on MATLAB / SIMULINK and ADAMS was adopted to verify the dynamics and control strategy. Results: The bandwidth of each degree of freedom in the 3-DOF parallel mechanism was used to expand about 10Hz and the amplitude error was controlled below 5%. Conclusion: Based on the designed dynamic model and composite control strategy, the controlled accuracy of the parallel mechanism is improved and the bandwidth of the control system is broadened. Furthermore, the improvements can be made in aspects of control accuracy and real-time performance to compose more patents on parallel mechanisms.

Background: Electric Submersible Pumps (ESPs) are widely used in agricultural fields, petroleum, and various other industries. These pumps are mostly driven at a constant speed since an A.C. motor is normally used as the drive. However, ESPs can also be operated at various speeds by employing a Variable Frequency Drive (VFD). Several patents have been published in ESP. Normally these pumps are started with the discharge valve at its closed position in order to control the starting current. When the ESP runs at its shut-off position, it will develop a higher head and an increase in fluctuating pressure. In order to evaluate the effects of pressure fluctuation, its characteristics must be investigated. Objective: Experimentally investigate the characteristics of pressure pulsation which are generated at each stage of a multistage ESP during shut-off condition at various speeds. Methods: An ESP with five stages was selected for conducting experiments. A VFD was used for operating the ESP at five speed settings from 80 to 120 % of its rated speed. Piezoresistive transducer was placed at the delivery side of the pump to acquire the signals of unsteady pressure. The pump was operated at closed valve condition at each speed, and unsteady pressure signals due to pressure pulsation were captured. Results: Obtained results have indicated the presence of fundamental frequency pertaining to vane passing frequency and harmonics of higher frequencies. Conclusion: Study of pressure fluctuations at shut-off will help to analyze the failures of ESP due to vibration which occur when the pump runs at closed valve position for a prolonged length of time and stability of these pumps at lower flow rates.