  We develop in this paper a method ensuring robustness properties to bang-bang
strategies , for general nonlinear control systems. Our main idea is to add
bang arcs in the form of needle-like variations of the control. With such
bang-bang controls having additional degrees of freedom, steering the control
system to some given target amounts to solving an overdeter-mined nonlinear
shooting problem, what we do by developing a least-square approach. In turn, we
design a criterion to measure the quality of robustness of the bang-bang
strategy, based on the singular values of the end-point mapping, and which we
optimize. Our approach thus shows that redundancy implies robustness, and we
show how to achieve some compromises in practice, by applying it to the
attitude control of a 3d rigid body.
