In this paper,the mechanical properties of a certain type of CNC lathe spindle box are analyzed by the finite element software HyperWorks. On this basis, the topology optimization of the CNC lathe spindle box is done by the variable density method. where the spindle box relative density is taken as the design variable and the minimum volume of the spindle box as the objective function, its static deformation and the low modes as constraints．That is to find the optimal layout of the structure,and then the size optimization of the spindle box is done to make further amendments of the topology optimization results. This design method achieves the lightweight design of the spindle box, reduces manufacturing costs,and provides a theoretical basis for enterprises to improve the structure of CNC lathe spindle box.

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The speed increasing gearbox is the key part of the wind turbine, and it requires higher reliability and service life than general mechanical system. The single-stage planetary gears train(PGT) are commonly used in the semi-direct drive wind turbines, which sustain low speed, heavy load, varying speed and varying load. The dynamic characteristics are very complex, due to the frequent disturbance under the random wind and have a greater impact on reliability and stability of wind turbines. In this paper, the torsional dynamic model for PGT of semi-direct drive wind turbine was developed by lumped parameter method. According to the configuration and design parameters of the planetary gears, the natural frequencies are calculated, and the vibration modes are also analyzed. The actual wind speed is simulated by the weight sparse least squares support vector machines (WSLS- SVM), and the input torque load is also obtained. Considering the varying wind load and parameter excitations of system, the dynamic response of the PGT is calculated by numerical method.

In order to understand the operation of the water turbine generating by gravity .With the method of Linearization, equivalent and torque balance, this paper analysed, drove and calculated the water turbine’s rotational torque and speed theoretically ,and calculated by using examples according the motion characteristics of the turbine. By calculating, the factors of the water turbine’s capacity, the expression of the rotational torque and the turbine’s speed were obtained.

The paper uses modern control theory and mechanical and structural vibration theory to study a mass-spring system of three degrees. Using Newton's first law analyzing the force of the object, drawn the simulation diagram from the control perspective. Reflecting all changes of the independent variables and their relationships. And revealing the characteristics of the system. We also analyzed the system can not only be controlled but also can be observed, understanding the inherent nature of the system further. About the dynamic characteristics of the system, we use the main formation method to calculate the natural frequency, the main formation and displacement response of the system[1].