Study On Joint Maneuver And Fuel Optimization In Approach Phase For Space Rendezvous

In the second phase of China's manned space program, rendezvous and docking technology is a key technology to grasp, in which orbital transfer in approach phase plays an important part. This dissertation bases on orbital maneuver in approach phase. It studies optimal control problem on joint maneuver, analyzes the main errors'influence on the terminal position and velocity accuracy, and also presents a parameter-design measure to decrease the error of C-W equation. These studies provide important reference to orbital design and control problem in approach phase for engineering application. The main results are summarized as follows.Optimal control problem on joint maneuver in approach phase is studied. (1) According to optimal control law on finite thrust, specific maneuver strategies on joint maneuver are established, including coasting-propulsion mode and coasting-propulsion-coasting-propulsion mode. For coasting-propulsion mode, fuel optimal solution can be directly obtained by numerical computation and results comparison; for coasting-propulsion-coasting-propulsion mode, optimization method must be used, including creating optimization model and adopting PSODE optimization algorithm. (2) Comparing fuel consumption and others of four different maneuver strategies - two-impulse, low-thrust, coasting-propulsion mode and coasting-propulsion-coasting-propulsion mode, low-thrust maneuver consumes least fuel, but gets largest horizon angle; the horizon angle of coasting-propulsion-coasting-propulsion mode is the smallest. The impact of specific impulse ratio on fuel consumption is also studied. The results show the higher the ratio of specific impulse, the more obvious continuous thrust's advantage of low fuel consumption.The main errors'influence on the terminal position and velocity accuracy is studied. (1) The navigation error, control error and trajectory error model are established. Besides, Monte-Carlo simulation method is used to analyze the precision. Simulation results show the state in Y direction is more sensitive to errors; the impact of velocity navigation error is greater on the state in plane; the impact of continuous thrust control error is greater on the velocity in plane. (2) Comparing terminal position and velocity under four different orbital model- C-W, Two-body, J2, HPOP, the state in Y direction is more sensitive to orbital model; J2 perturbations have a bigger impact on transfer orbit; the nonlinear error, non-zero eccentricity error and perturbation error of C-W model cancel out each other a lot and the error of the model is reduced. (3) A modified C-W equation is established, introducing J2 perturbation first-order item and gravitational second-order item. A parameter-design measure is studied to decrease the error of C-W equation in a short time and the measure is proved to be effective by examples.