Deployment Dynamics And Control Of Solar Arrays

With the development of space science and technology, space activities and on-orbit missions of the spacecraft have been drastically diversified, and components of the spacecraft are also becoming more and more complex. Meanwhile, for the factors of vehicle weight, loading capability, the cost of emission and etc, more and more light and flexible accessories have been employed in the spacecraft engineering nowadays, which makes the influence of spacecraft’s flexibility become an inevitable problem to be considered. On the other hand, with highly demanding accuracy of the spatial tasks, such as spatial positioning, mechanical arm to capture objects, and considering the highly complex and non-smooth mechanical phenomenon in the hinges of the solar arrays, the study on the precise modeling of spacecraft’s dynamics considering joint friction and other no-linear factors has been advanced on agenda and become a both hot and challenging issue in the field of the current science of spacecraft and mechanics.Solar array is a vital component of the spacecraft, which provides necessary power for the whole system. The growing complexity and diversification of spacecraft’s space tasks give rise to the phenomenon that the solar arrays are becoming more flexible, lighter and larger. As a result, the influence of the flexibility becomes a highlighting and prominent issue in dynamics modeling of the spacecraft with large flexible solar arrays. Moreover, considering the limitation of loading space and being subjected to high dynamic load during the launch process, the solar arrays are folded during spacecraft launch and ascent. After the spacecraft and the launch vehicle are separated and spacecraft is turned into the free orbit, the solar arrays will be freed from their fixation position and deployed by driving torsion spring. There is a complex dynamic coupling phenomenon between the solar arrays and the spacecraft that the attitude adjustment of the spacecraft may cause the continuous vibration problem of the solar arrays for a long time, and meanwhile the continuous vibration of the solar arrays may affect the attitude of the spacecraft. Therefore, studies on the development dynamics and control of the solar arrays are theoretically meaningful and engineeringly significant.This dissertation is funded by the Key Project [grant number 11132001] and the General Project [grant number 11272202] of Natural Science Foundation of China, and the Aviation Science Foundation of China [grant number 20120157002] and the Key Project of Shanghai Scientific Research [14ZZ021], and presents theoretical and simulation studies of the deployment dynamics and control of the solar arrays. The main research and achievements are as follows:(1) This dissertation starts theoretical and numerical studies of the multi-rigid-body system dynamics and control of the solar arrays. First of all, the structures of the rigid solar arrays are presented and their counterpart equivalent physical and mathematical models are established. Using the independent generalized coordinates( joint coordinate) to describe the multi-rigid-body system of the solar arrays, the dynamics equation of the system is then derived in detail. Afterwards, the verification and correctness of the theory proposed in this dissertation are accomplished through the numerical simulation of deployment dynamics of the rigid solar arrays. Finally, studies on methods of the conventional PD and fuzzy adaptive PD for control of spacecraft’s attitude are explored. The numerical results of the deployment dynamics and active control of the rigid solar arrays show that the model of the multi-rigid-body system built by this dissertation can effectively describe dynamic characteristics of the rigid solar arrays, and the fuzzy adaptive PD control has better control effect than conventional PD control.(2) This dissertation secondly presents theoretical and numerical studies of the multi-flexible-body system dynamics and control of the solar arrays. First of all, the equivalent calculation method of the solar arrays is presented and their counterpart finite model is established by using the finite element. Then the independent generalized coordinates(combinations between joint coordinates and modal coordinates) are employed to describe the multi-flexible-body system of the solar arrays, and the dynamics equation of the system is derived. Afterwards, the verification and correctness of the theory proposed in this dissertation are accomplished through the numerical simulation of deployment dynamics of the flexible solar arrays. Finally, studies on of the conventional PD and the fuzzy adaptive PD for control of spacecraft attitude are explored. The numerical results show that the model of multi-flexible-body system built in this dissertation can effectively describe the attitude response of the spacecraft and the time history of the flexible solar arrays, the flexibility of the solar arrays has certain influence on the deployment dynamics of the solar arrays and the fuzzy adaptive PD control has better control effect than the conventional PD control.(3) This dissertation presents a theoretical and simulation study of dynamics issue of the joint friction for the solar arrays. Firstly, the friction models generally used in engineering and their counterpart properties are given. Then, based on the virtual power principle the contribution of the joint friction to the multibody system dynamics and the closed system dynamic equation for both the LuGre model and 3D bristle model are established by utilizing two different methods of the Lagrange method and the Newton-Euler single direction recursive method, respectively. Finally, the effect of joint friction on the characteristic of the multibody systems of solar arrays is explored using the numerical simulation. The numerical results show that joint friction plays an inevitable role in the deployment dynamics and the attitude response of the spacecraft.