Pasternak Y. Synthesis of antenna control systems based on a parallel kinematic guidance mechanism with statically indeterminate connections

The dissertation is devoted to the solution of the scientific problem which consists in increase tracking accuracy of spacecraft of remote sensing of the Earth in antennas guidance systems on the basis of parallel kinematic mechanism. The current state and trends in the development of antenna systems and their control systems for remote sensing of the Earth are analyzed. The use of the Stewart platform as a pivoting guidance mechanism has been proposed. This simplifies the mechanical design of the antenna system compared to conventional rotating devices, the main disadvantage of which is the high requirements for the accuracy of manufacturing large-diameter rotating mechanisms, which leads to bulkiness, large weight, complexity of manufacturing and assembling devices and, in general, increasing cost of antenna systems. The proposed support-rotary device based on a parallel structure is relatively simple and has high technical characteristics, but requires more complex algorithms to control its operation. The review of approaches to control of antenna complexes on the basis of parallel kinematic mechanism is carried out. Conclusions are made about the parameters that affect the accuracy of the system. The advantages and disadvantages of design and control systems are described. Factors that complicate the control process of the parallel structure mechanism are identified, in particular, the solution of the control problem is significantly complicated when it is necessary to calculate the position in real time. The dynamics of the task is much more complicated, because in order to reach any position it is necessary to build a common trajectory to it and the trajectory for each of the actuators. Calculate the speeds and accelerations at each point of the trajectory and force all six electric drives to work out their trajectory synchronously and in concert with the lowest errors of speed and acceleration, while adhering to the conditions of their coordinated movement. An algorithm for calculating the elongation of actuators is proposed, and the method of controlling the guidance of the antenna based on a parallel kinematic mechanism is improved. The use of the model of kinematics of spacecraft tracking is offered, which allows to determine the characteristics of control actions of the antenna control system. The proposed three-dimensional mathematical model of the rotary support device is successfully used in the creation of a control system and a prototype of the antenna system. A dynamic model of the system is proposed, which allows to determine the influence of geometrical parameters of the proposed parallel kinematic mechanism on the main technical characteristics of the system. Based on the obtained results of the research, the support-rotary device of the antenna system on the basis of the parallel kinematic guidance mechanism, hardware and software for its control are developed. It is experimentally proved that the proposed model adequately describes the operation of the proposed parallel kinematic mechanism.