Micro-positioning platform plays an important role in the field of precision positioning such as microelectronics, robotics and biomedicine. This paper proposes an equal-stiffness and equal-stroke 2D micro-positioning platform, which is driven by piezoelectric actuators. The overall structure of the 2D micro-positioning platform adopts a nested structure and the displacement magnification mechanism adopts two hourglass displacement magnification mechanisms. The displacement magnification ratio of the hourglass displacement magnification mechanism was studied, and its structural parameters were optimized. Static stiffness analysis and simulation analysis of the micro-positioning platform were carried out. The simulation stiffness of the micro-positioning platform in the XY direction is 46873 N/m and 46832 N/m respectively. The experimental prototype of the micro-positioning platform was built. Through the measurement experiment with the prototype, the maximum stroke of the micro-positioning platform in the XY direction is 489 μm and 493 μm respectively; the maximum coupling ratio in the XY direction is 2.38% and 2.70% respectively. The research indicates that the micro-positioning platform had the characteristics of small size, equal long stroke, equal stiffness and low coupling ratio in the XY direction.

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Internal ballistic equations of artillery shrapnel are established on the basis of theoretical analysis, and equivalent method used for dealing with semi-combustible cartridge case, calculation program selects the Matlab software. The simulation results are accord with the experimental data, it shows design of equations and calculation program is reasonable and credible. IntroductionsWith the requirements of development of artillery's technology, the emergence semi combustible cartridge case is a perfect combination of all advantages of combustible cartridge case and metal cartridge case. In this paper, we studied internal ballistic of lower chamber pressure artillery firing with semi-combustible cartridge case.According to the tactical technical requirements, in order to increase the damage effect of projectiles, launch projectiles need larger firing range and enough large falling angle when hit the ground target, so it must obtain different firing velocity. It is obviously that only one kind of charge cannot meet the requirements, and it must be spited into several small parts of propellant charge with different mass and shapes. But the propellant charge is incomplete combustion under low pressure when the charge is reduced to a certain amount, then the velocity distribution increased and the less quality of charge, the more obviously phenomenon. In order to address this issue the method of mixed charge is adopted that is combination of thin and thick powder charging gunpowder. In the small charging it mainly is thin charging gunpowder which can maintain constant pressure for complete combustion and fuse can remove insurance.

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