STEP: A New Mobile Platform With 2-DOF Transformable Wheels for Service Robots

This article presents a new mobile platform with two-degree-of-freedom (2-DOF) transformable wheels for service robots, which can overcome steps and stairs of various sizes encountered in indoor environments. The concept of the 2-DOF transformable wheel is introduced and the required transformation ranges are examined. In this article, a five-bar PRRRP mechanism is adopted as the base mechanism for 2-DOF transformation. Also, to separate the wheel rotation from the wheel transformation effectively, a four-bar RRPP mechanism is incorporated into the base mechanism. The design variables for the new wheel are determined not only to satisfy the kinematic constraints but also to provide the torque required for the mobile platform called STEP with the new wheels to overcome steps. The experiments using the STEP are performed for different steps and combined steps to prove the good obstacle-overcoming ability of the STEP with the new transformable wheels.