No abstract

Valveless servo system is a new technology which is widely used in recent years. Compared to the traditional hydraulic system, valveless servo system has a lot of advantages such as high efficiency, less pollution and saving energy, which will be the main research direction of the hydraulic control in the future. Roll bending machine is a large industrial machine, but the efficiency of existing hydraulic system of roll bending machine is low and the cost of maintenance management is high. Applying valveless system on roll bending machine can overcome these defects. This paper made a study of the control strategies which were about valveless servo system on roll bending machine. And software MATLAB was used to do simulation experiment on valveless servo system. This paper summarized the steady-state error and dynamic characteristics according to output signals in different input signals.

Wind power is a clean and renewable energy, and more and more countries in the world attach great importance to it and promote the development of the wind power industry. The current situation of wind turbines at home and abroad, the development, types, and characteristics were analyzed. The structural design of vertical axis wind turbine (VAWT) and aerodynamic theory of rotor blade were briefly introduced, the characteristic parameters in VAWT design were presented in this paper. Using finite element analysis method, the spindle which is the crucial component of VAWT under the extreme wind load was analyzed, and the corresponding results were obtained. Finally the wall thickness and the structure of spindle were improved and optimized to satisfy the engineering requirements of spindle.

With the rapid growth of China's economy, industrialization and urbanization process accelerate, energy has become a bottleneck for economic development, more and more people take energy trade and energy security into concern. Based on the status analysis of energy trade in China, according to the existing problems in the energy trade we put forward the corresponding countermeasures.