consider a r-integrator chain
\dot z_1 = z_2
...
\dot z_r = \phi + \gamma u.
where \gamma is bounded positive (to ensure the controlability), and the TIME DERIVATIVE of \phi and \gamma are also bounded. contrary to problem formulation of HOSM where \phi is assumed to be bounded, not its time derivative.
I'm looking for a controller u which ensure r+1 sliding mode and can be called r-order supertwisting.
Does aneyone have a bibliography of such controller u, where u is continuous or quasicontinuous?