  The extreme velocities and high ionization states of ultra-fast outflows
(UFOs) make them a promising candidate for AGN feedback on the evolution of the
host galaxy. However, their exact underlying driving mechanism is not yet fully
understood. Given that the variability of UFOs may be used to distinguish among
different launching mechanisms, we aim to search for and characterize the
responses of the UFO properties to the variable irradiating luminosity. We
performed a high-resolution spectroscopy of archival XMM-Newton observations on
six highly-accreting NLS1 galaxies. The state-of-the-art methods of the blind
Gaussian line scan and photoionization model scan are used to identify UFO
solutions. We search for ionized winds and investigate the structure of ionized
winds and their responses to the luminosity variations. The powerful
photoionization model scan reveals three previously unreported UFOs in RE
J1034+396, PG 1244+026 and I ZW 1, and two new WAs in RE J1034+396. The
entrained UFOs are discovered in 4 (66%) AGN, supporting the shocked outflow
interpretation for AGN ionized winds. 2 out of 7 (28%) UFOs seem to respond to
the continuum and 3 (43%) UFOs hint at a radiatively accelerated nature.
Combined with published works, we do not find any correlations between UFO
responses and AGN properties except for a tentative ($\sim1.8\sigma$)
anti-correlation between the UFO acceleration and the Eddington ratio, to be
confirmed by further observations and an enlarged sample. The kinetic energy of
UFOs, mostly detected in soft X-rays, is found to have a large uncertainty. We,
therefore, cannot conclude whether soft X-ray UFOs have sufficient energy to
drive the AGN feedback, although they are very promising based on some
reasonable assumptions.
