Attitude Control of Flexible System by Shaping Constant-Amplitude Input

Attitude manoeuvres of satellites in space are generally performed by using thrusters. Thrusts
resulted usually can not be variable, they are constant in amplitudes. When a satellite has
flexibility in its structural members or in its member’s joints, under constant-amplitude thrust,
large structural vibration and attitude angle oscillation may occur during and after the
manoeuvre. This attitude oscillation of course will disturb its pointing to earth. So, this
oscillation should be removed or should be reduced to the small value under the maximum
permissible pointing errors. To reduce residual attitude angle oscillations, input shaping method
is used in this paper. This method determines number and time locations of input pulses to be
used to the satellite regarding to the system’s flexibility. As the result, the input consists of a
sequence of constant pulses in the suitable directions and time switching locations. The satellite
studied in this paper consists of a main body and two solar panels. The main body is a cubic
rigid box, while the solar panels are large in size and they are supposed to be flexible. Finite
element method is used to discrete the solar panel’s motion. The solar panels are modelled as a
collection of rectangular bending plate elements. Then, attitude manoeuvres of the satellite are
simulated numerically. By shaping the inputs, the residual oscillation of attitude angles of the
satellite can be suppressed successfully into an expected level.