The analytical formulations of the velocity and the acceleration of a 2-DOF spherical parallel mechanism are derived by the screw theory. Based on building its dynamics model by the principle of virtual work and recip...The analytical formulations of the velocity and the acceleration of a 2-DOF spherical parallel mechanism are derived by the screw theory. Based on building its dynamics model by the principle of virtual work and reciprocal product of the screw, the equation of the motor moment is obtained. Through the transformation of dynamics model, the configuration space method of the dynamics equation and the corresponding coefficients are presented. Finally, the result of an example shows that the inertia moment and the gravity play a more important role than the coriolis and centrifugal moment, and the former is ten times of the latter in the magnitude. So, the latter can be neglected only when the velocity of mechanism is very slow.展开更多
Based on the hopping principle, a miniature gas fuel-powered hopper is designed and manufactured. According to thermodynamic analysis, the pressure-displacement curve in the combustion chamber after ignition is obtain...Based on the hopping principle, a miniature gas fuel-powered hopper is designed and manufactured. According to thermodynamic analysis, the pressure-displacement curve in the combustion chamber after ignition is obtained through iterative calculation, then the work on the cylinder done by high-pressure gas is calculated and the initial hopping velocity of the hopper is obtained. The wireless control system is developed to realize the tele-control of the hopper, including fuel injection and ignition. Experimental results agree well with analytical results. The hopper has a jumping ability of height 2.2 m and distance 3.5 m, and it is more than 14 times its dimension.展开更多
开发了一种基于B样条的高阶面元法用来求解浅水船舶兴波问题。船体表面和自由面上分别布置Rankine源,同时利用镜像原理来计及水底的影响。物体几何用 B 样条曲面精确表示。在求得边界面上的源强密度分布后,物面上的速度势用B样条来表示...开发了一种基于B样条的高阶面元法用来求解浅水船舶兴波问题。船体表面和自由面上分别布置Rankine源,同时利用镜像原理来计及水底的影响。物体几何用 B 样条曲面精确表示。在求得边界面上的源强密度分布后,物面上的速度势用B样条来表示。数值计算中采用配置方法,并且用高斯—勒让德公式来计算方程中的积分。为了验证文中方法的有效性,用本方法计算了Wigley船在深水和浅水中的兴波水动力和波形,所得数值结果与试验结果和其它数值结果进行了比较,吻合程度令人满意,表明本方法被用来求解浅水船舶兴波问题是有效的。展开更多
基金Supported by the National Natural Science Foundation of China (50375071)the Jiangsu Province Key Lab on Digital Manufacture Project (HGDML-0604)~~
文摘The analytical formulations of the velocity and the acceleration of a 2-DOF spherical parallel mechanism are derived by the screw theory. Based on building its dynamics model by the principle of virtual work and reciprocal product of the screw, the equation of the motor moment is obtained. Through the transformation of dynamics model, the configuration space method of the dynamics equation and the corresponding coefficients are presented. Finally, the result of an example shows that the inertia moment and the gravity play a more important role than the coriolis and centrifugal moment, and the former is ten times of the latter in the magnitude. So, the latter can be neglected only when the velocity of mechanism is very slow.
基金Supported by the National Natural Science Foundation of China(50605031)~~
文摘Based on the hopping principle, a miniature gas fuel-powered hopper is designed and manufactured. According to thermodynamic analysis, the pressure-displacement curve in the combustion chamber after ignition is obtained through iterative calculation, then the work on the cylinder done by high-pressure gas is calculated and the initial hopping velocity of the hopper is obtained. The wireless control system is developed to realize the tele-control of the hopper, including fuel injection and ignition. Experimental results agree well with analytical results. The hopper has a jumping ability of height 2.2 m and distance 3.5 m, and it is more than 14 times its dimension.
基金Supported by the National Natural Science Foundation of China (Grant No: 10572094)the Natural Science Foundation of Shanghai (Grant No: 06ZR14050)
文摘开发了一种基于B样条的高阶面元法用来求解浅水船舶兴波问题。船体表面和自由面上分别布置Rankine源,同时利用镜像原理来计及水底的影响。物体几何用 B 样条曲面精确表示。在求得边界面上的源强密度分布后,物面上的速度势用B样条来表示。数值计算中采用配置方法,并且用高斯—勒让德公式来计算方程中的积分。为了验证文中方法的有效性,用本方法计算了Wigley船在深水和浅水中的兴波水动力和波形,所得数值结果与试验结果和其它数值结果进行了比较,吻合程度令人满意,表明本方法被用来求解浅水船舶兴波问题是有效的。
