  We demonstrate the first successful non-invasive stabilisation of nonlinear
travelling waves in a straight circular pipe using time-delayed feedback
control (TDF). The main novelty in this work is in the application of a
"multiple time-delayed feedback" (MTDF) approach, where several control terms
are required to attenuate a broad range of unstable eigenfrequencies. We
implement a gradient descent method to dynamically adjust the gain functions,
$G_i(t),$ in order to reduce the need for tuning a high dimensional parameter
space. We consider the effect of the control terms via an approximate linear
analysis and a frequency-domain analysis, which justifies the choice of MTDF
parameters. By using an adaptive approach to setting the control gains, we
advocate for a broad range of MTDF terms which are then free to find their own
stabilising amplitudes for a given target solution, thereby removing trial and
error when the instability of the target solution is unknown a'priori. This
also enables travelling waves to be stabilised from generic turbulent states
and with speculative starting parameters.
