Algorithm 3 Pitch–Pitch only step climbing

Require: robot is set longitudinally perpendicular to the stair; Ensure: the step’s height has been acquired;  Calculate L modules to rise;  for $i=N$; $i\le L$; $i--$do             ▹ Pushing modules up      Raise ith module;      Approach;  end for  do                       ▹ Pulling modules up      Approach;      Place nth module on top of the step;      $n\leftarrow n-1$;  while  $n>1$ Ensure: the robot is correctly positioned;