Guidance and control of tethered satellite systems using pseudospectral methods

This paper presents 2 strategies for implementing a guidance and control system for tethered satellite systems. The strategies are based on a 2 degree of freedom approach. In the first strategy an outer loop, designed using a quadrature discretization method and quasilinearization, is combined with a neighboring optimal feedback controller. In the second strategy, an outer loop, designed using a quadrature discretization method, is combined with a nonlinear receding horizon tracking controller. The outer loop is updated regularly based on the measured system state and implemented in the system with the feedback controllers. The computational delay in solving the outer loop problem is taken into consideration. Numerical results are presented for three scenarios involving tethered satellites where it is demonstrated that terminal guidance can be achieved. Comparisons with the case where no outer loop is used show considerable improvement in achieving the terminal state.