【摘要】：近地小行星撞擊地球雖是小概率事件,但其可能性不容忽視。為防御小行星,科學(xué)家們已提出多種緩解小行星威脅的方案。本文介紹了一種利用太陽(yáng)帆—小行星繩系系統(tǒng)在不破壞小行星結(jié)構(gòu)和成分的條件下改變小行星軌道的方法。文中首先在繩系質(zhì)量塊系統(tǒng)模型的基礎(chǔ)上,加入太陽(yáng)帆受到的太陽(yáng)光壓力,建立了太陽(yáng)帆—小行星繩系系統(tǒng)的動(dòng)力學(xué)模型。然后提出了以偏移距離最大為目標(biāo)的連續(xù)時(shí)間最優(yōu)控制問(wèn)題,使用勒讓德偽譜法將連續(xù)最優(yōu)控制問(wèn)題轉(zhuǎn)化為非線性規(guī)劃問(wèn)題,并使用序列二次規(guī)劃方法進(jìn)行求解。仿真結(jié)果表明,利用太陽(yáng)帆—小行星繩系系統(tǒng)能夠有效地對(duì)小行星的軌道產(chǎn)生影響,使其偏離原始軌道,且能避免因太陽(yáng)帆與小行星的相對(duì)運(yùn)動(dòng)引起的系繩纏繞問(wèn)題;太陽(yáng)帆的面積是影響太陽(yáng)帆—小行星繩系系統(tǒng)改變小行星軌道能力的一個(gè)主要因素。為了解決小行星的自轉(zhuǎn)給小行星探測(cè)、小行星防御等造成的困難,本文提出了使用繩系太陽(yáng)帆減緩小行星自轉(zhuǎn)的方案。首先對(duì)普通航天器在小行星旋轉(zhuǎn)引力場(chǎng)中的運(yùn)動(dòng)學(xué)方程進(jìn)行改進(jìn),得到了繩系太陽(yáng)帆在小行星固連坐標(biāo)系中的動(dòng)力學(xué)模型。在利用繩系太陽(yáng)帆減緩小行星的自轉(zhuǎn)時(shí),需要將太陽(yáng)帆穩(wěn)定在小行星的初始平衡點(diǎn)處以便于控制,于是使用PD控制方法求解使太陽(yáng)帆穩(wěn)定在小行星初始平衡點(diǎn)的控制律,并使用最優(yōu)控制方法對(duì)控制變量進(jìn)行了優(yōu)化。仿真結(jié)果表明,使用繩系太陽(yáng)帆能夠有效地減緩甚至消除小行星的自轉(zhuǎn),同時(shí),太陽(yáng)帆的面積也是影響繩系太陽(yáng)帆改變小行星自轉(zhuǎn)角速度能力的一個(gè)主要因素。
[Abstract]:Although the impact of near-Earth asteroids on the earth is a small probability event, its possibility can not be ignored. To defend against asteroids, scientists have come up with a variety of plans to mitigate the asteroid threat. In this paper, a method of changing asteroid orbit by using solar sail-asteroid rope system without destroying the structure and composition of asteroid is introduced. In this paper, the dynamic model of the solar sail-asteroid rope system is established by adding the solar pressure of the solar sail on the basis of the mass block system model of the rope system. Then, a continuous time optimal control problem with the goal of maximum offset distance is proposed. The continuous optimal control problem is transformed into a nonlinear programming problem by Legendre pseudo-spectral method, and the sequential quadratic programming method is used to solve the problem. The simulation results show that the solar sail-asteroid rope system can effectively affect the orbit of asteroids, make them deviate from the original orbit, and avoid the problem of rope entanglement caused by the relative motion of solar sails and asteroids. The area of solar sails is a major factor affecting the ability of solar sail-asteroid rope system to change asteroid orbit. In order to solve the difficulty caused by asteroid rotation to asteroid exploration and asteroid defense, a scheme of using tethered solar sail to slow asteroid rotation is proposed in this paper. Firstly, the kinematics equation of the ordinary spacecraft in the asteroid rotating gravitational field is improved, and the dynamic model of the tethered solar sail in the asteroid fixed coordinate system is obtained. When using rope solar sails to slow down the rotation of asteroids, it is necessary to stabilize the solar sails at the initial equilibrium point of asteroids for easy control, so the PD control method is used to solve the control law to stabilize the solar sails at the initial equilibrium points of asteroids. The optimal control method is used to optimize the control variables. The simulation results show that the use of rope solar sails can effectively slow down or even eliminate the rotation of asteroids. At the same time, the area of solar sails is also a major factor affecting the ability of rope solar sails to change the rotation velocity of asteroids.
【學(xué)位授予單位】：南京航空航天大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2016
【分類(lèi)號(hào)】：P185.7
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本文編號(hào)：2475376