The present paper describes step-climbing tactics using a wheeled robot and a hand cart that has a hand brake. The robot has two arms that are used to hold or push the handle of the cart and a lower extendable wheel mechanism that can push against the bottom of the cart. Some of the manipulator joints are controlled passively when moving over the step. To lift the front wheels of the cart, the robot holds the handle steady and pushes against the bottom of the cart using the extendable wheel mechanism. This action is similar to that performed by a human. The robot then pushes the entire cart forward so that the front wheels of the cart are above the step. When the rear wheels of the cart have climbed the step, the upper-arm links of the manipulators are pressed against the robot chest to allow the robot to push the cart. When the cart has fully climbed the step, the robot then uses the cart to climb the step. The present paper describes the details of the robot system, and theoretical analyses were performed to determine the requirement of masses and the centers of gravity of both vehicles to lift the cart. Experiments were also carried out in which the robot was controlled using an intranet connection, and the results demonstrated the effectiveness of the proposed method. 2114 68 position, and this mechanism is used by the robot to climb steps (Figure 2, see Section 3). The hand 69 cart and robot are deployed in a forward-and-aft configuration (Figure 3). The specifications of the 70 robot and the hand cart are shown in Tables 1 and 2 (Appendix). 71 Figure 4 shows the process in which a human moves a hand cart over a step. Most people push 72 the rear bottom of the cart with their foot when lifting the front wheels of the hand cart during step 73climbing. When some people push and lift the rear wheels of a heavy cart, they limit the passive 74 rotation about the shoulder joints as the upper arms are pushed into their chest. In the present paper, 75 this motion is performed using the front-wheel mechanism of the robot (Figures 5 and 6) and the 76 robot stopper (Figure 7). 77 The robot has manipulators attached to the left and right sides of its upper half. In addition to 78 the five degrees of freedom (DOFs) of the arm, the hand has one DOF, for a total of six DOFs (Figure 79 7). The manipulator joint angles are -90 [deg] ≤ φ 2 ≤ +90 [deg] and 0 [deg] ≤ φ 4 ≤ +100 [deg]. 80The robot has a stopper mounted on the front of its body (Figure 7). First, the upper links of the 81 manipulators are located behind the stopper when the front wheels of the cart are lifted (Figure 8). 82 131 mechanism (Figure 6). The front wheels of the cart start to be lifted. (3) The robot continues to push 132 the rear bottom part of the cart, and the cart tilt increases. The action for lifting the front wheels of 133 the cart exerts forces on the manipulators, causing passive rotation about Joint 2. However, the upper 134 arm link of the manipulator comes into contact with the robot stopper, limiting the extent of rotation 135 (Figure 9). ...