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The flow field distribution in the star herringbone gearbox lubricated by oil injection is very complex, and there are many difficulties in the flow simulation analysis. Based on the smooth particle hydrodynamics (SPH) method, the particle simulation model of the flow field in the star herringbone gearbox with oil injection lubrication is established, and the oil-gas two-phase distribution characteristics at different cross-section positions in the gearbox are obtained. The oil-liquid distribution and velocity distribution of flow field under different gear speeds and oil injection speeds are compared and analyzed. The results show that the oil flow field distribution is obviously different at different cross-section positions in the gear shaft direction, the oil flow in the middle cross-section position of the gearbox is the largest, and the local eddy current phenomenon occurs in the area between the solar wheel, planetary wheel and oil injection port. The gear speed and oil injection speed have great influence on the oil distribution in the gearbox.

The three degrees of freedom parallel robot with is simple to control, convenient for design and research and has compact structure. In order to study the influence of parallel robots' joint configuration on the size of workspace, two Tau variant parallel robots, 3-RSS and 3-RUU, are taken as the research objects. Then, the spherical hinge and the Hooke hinge are respectively used for analyzing and solving the workspace of the 3-RSS and 3-RUU coaxial drive layout parallel robots. Firstly, a simplified model of the robot is established, and its forward kinematics is solved. Then, the motion range of spherical hinge and Hooke hinge are analyzed as the constraints of the joint so that the three-dimensional workspace of 3-RSS and 3-RUU coaxial drive layout parallel robots is analyzed so as to obtain the workspace boundary. The analysis results show that the 3-RUU coaxial drive layout parallel robot of the same size has a larger workspace than the 3-RSS coaxial drive layout parallel robot. It provides theoretical and technical support for subsequent research on joint selection and workspace of different parallel robots.

Controllable variable stiffness compliant actuator mechanism has the characteristics of high compliance, high environmental adaptability and good man-machine interaction. The variable stiffness compliant actuator mechanism is based on the transmission principle of a four-bar linkage with a zero-length rack. The variable stiffness control can be realized by changing the properties and the winding mode of the elastomer, or the configuration scheme. Through configuration analysis and structure design, the stiffness and torque models of the compliant actuator mechanism are established to reveal its stiffness behavior. The Lagrangian method is used to establish the dynamic model of the compliant actuator mechanism, and the frequency theoretical results are obtained by solving the average stiffness. The virtual prototype is established to motion simulation, which reveals its performance characteristics and verifies the correctness of theoretical analysis. Compared with other similar designs, the compliant actuator mechanism proposed has the characteristics of miniaturization and lightweight with strong applicability. It can be used as a single module and integrated into the exoskeleton system.

Based on the physiological characteristics of crab,a bionic crab- like robot composed of eight legs and two pincers is designed by using bionics principle. The cross direction moving and turning of the bionic crab- like robot are realized by controlling the walk stepping motor to drive gear crank connecting rod mechanism,the lifting and falling of pincers is realized by controlling the lifting stepping motor to drive gear and rack mechanism,the left and right swing of pincers is realized by controlling the swing steering engine,the snatching of pincers is realized by controlling the snatching steering engine drive intermittent gear and double- rocker linkage mechanism. The bionic crab robot has three good merits such as agile transmission,high driving efficiency,convenient maintaining,which is seasoned with different road surface. The robot has a good application potential under complex road conditions to search and detection. The design method is helpful for transmission design of multi- legged bionic robot in execrable environment.

The effect of vibration on the micro-forming ability of Zr55Cu30Al10Ni5 bulk metallic glass in its supercooled liquid region was studied. The experiment of micro-extrusion was carried out under different amplitude (38 ∼ 760 N) and different frequency (0.1 ∼ 2.0 Hz) at a fixed temperature of 723 K. The extrusion length was taken as a measure to characterize the micro-forming ability. Results reveal that the extrusion length of bulk metallic glass is effectively improved under vibration loading, and increases with increasing loading frequency and amplitude, whereas the frequency dependence is stronger. The viscosity of bulk metallic glass declines under vibration loading because of a larger free volume concentration and surface effect caused by vibration. This research indicates that the vibration forming is an effective method to enhance the micro-forming ability of bulk metallic glasses.

The dimensional accuracy and microstructure affect the service performance of parts fabricated by wire arc additive manufacturing (WAAM). Regulating the geometry and microstructure of such parts presents a challenge. The coupling method of an artificial neural network and finite element (FE) is proposed in this research for this purpose. Back-propagating neural networks (BPNN) based on optimization algorithms were established to predict the bead width (BW) and height (BH) of the deposited layers. Then, the bead geometry was modeled based on the predicted dimension, and 3D FE heat transfer simulation was performed to investigate the evolution of temperature and microstructure. The results showed that the errors in BW and BH were less than 6%, and the beetle antenna search BPNN model had the highest prediction accuracy compared to the other models. The simulated melt pool error was less than 5% with the experimental results. The decrease in the ratio of the temperature gradient and solidification rate induced the transition of solidified grains from cellular crystals to columnar dendrites and then to equiaxed dendrites. Accelerating the cooling rate increased the primary dendrite arm spacing and δ-ferrite content. These results indicate that the coupling model provides a pathway for regulating the dimensions and microstructures of manufactured parts. [ABSTRACT FROM AUTHOR]