  This paper discusses translation and attitude control in spacecraft
rendezvous and soft docking. The target spacecraft orbit can be either circular
or elliptic. The high fidelity model for this problem is intrinsically a
nonlinear system but can be viewed as a linear time varying system (LTV).
Therefore, a model predictive control (MPC) based design is proposed to deal
with the time-varying feature of the problem. A robust pole assignment method
is used in the MPC-based design because of the following merits and/or
considerations: (a) no overshoot of the relative position and attitude between
the target and the chaser to achieve soft docking by placing all closed-loop
poles in the negative real axis of the complex plan, which avoids oscillation
of the relative position and attitude, in particular, in the final stage, (b)
fast on-line computation, (c) modeling error tolerance, and (d) disturbance
rejection. We will discuss these considerations and merits, and use a design
simulation to demonstrate that the desired performance is indeed achieved.
