A mobile robot comprising: a robot chassis having a forward end, a rearward end and a center of gravity; a driven support surface moveably connected to the chassis and configured to propel the robot chassis forward and rearward; a first articulated arm rotatable about an axis located rearward of the center of gravity of the robot chassis , wherein the arm is configured to trail the robot , to rotate in a first direction to raise the rearward end of the robot chassis while the driven support surface propels the chassis forward in surmounting an obstacle, and to rotate in a second opposite direction to extend forward beyond the center of gravity of the robot chassis to raise the forward end of the robot chassis and invert the robot endwise; and a controller configured to operate the mobile robot in an obstacle surmounting maneuver comprising: driving the support surface to propel the robot to contact a riser of a first obstacle with the forward end of the robot , driving the support surface to cause the forward end of the robot to ascend the riser of the first obstacle; pivoting the first arm to raise the rearward end of the robot as the forward end of the robot ascends the riser of the first obstacle; driving the support surface to advance the forward end of the robot over the top of the obstacle riser; and pivoting the arm to further raise the rearward end of the robot such that the forward end of the robot tips downward beyond the top of the riser of the first obstacle. a robot chassis having a forward end, a rearward end and a center of gravity; a driven support surface moveably connected to the chassis and configured to propel the robot chassis forward and rearward; a first articulated arm rotatable about an axis located rearward of the center of gravity of the robot chassis , wherein the arm is configured to trail the robot , to rotate in a first direction to raise the rearward end of the robot chassis while the driven support surface propels the chassis forward in surmounting an obstacle, and to rotate in a second opposite direction to extend forward beyond the center of gravity of the robot chassis to raise the forward end of the robot chassis and invert the robot endwise; and a controller configured to operate the mobile robot in an obstacle surmounting maneuver comprising: driving the support surface to propel the robot to contact a riser of a first obstacle with the forward end of the robot , driving the support surface to cause the forward end of the robot to ascend the riser of the first obstacle; pivoting the first arm to raise the rearward end of the robot as the forward end of the robot ascends the riser of the first obstacle; driving the support surface to advance the forward end of the robot over the top of the obstacle riser; and pivoting the arm to further raise the rearward end of the robot such that the forward end of the robot tips downward beyond the top of the riser of the first obstacle. driving the support surface to propel the robot to contact a riser of a first obstacle with the forward end of the robot , driving the support surface to cause the forward end of the robot to ascend the riser of the first obstacle; pivoting the first arm to raise the rearward end of the robot as the forward end of the robot ascends the riser of the first obstacle; driving the support surface to advance the forward end of the robot over the top of the obstacle riser; and pivoting the arm to further raise the rearward end of the robot such that the forward end of the robot tips downward beyond the top of the riser of the first obstacle. <EOS>