A compact payload stopper includes: an interface assembly that serves as a main structural member of the payload stopper, the payload stopper configured to stop the payload from moving off a mobile robot; a stopper blade assembly connected to the interface assembly so as to allow the stopper blade assembly to pivot about an axis of the interface assembly, the stopper blade assembly configured to have a disengaged position that allows for a payload to be moved onto or off the robot, the stopper blade assembly further configured to have an engaged position that stops the payload from moving off the robot; and a motor assembly comprising a motor, the motor assembly connected to the interface assembly, the motor assembly configured to apply a force to the stopper blade assembly, causing the stopper blade assembly to rotate into a desired position of the engaged position and the disengaged position.