Well the very first attempt this guys made (https://arxiv.org/pdf/1804.10332.pdf#subsection.6.1) was let the model learn from scratch (open loop, large bounds feedback). An agile galloping gait emerged automatically also in my simulation (https://github.com/nicrusso7/rex-gym#galloping-gait---from-s...), even if the gait was 'noisy'