Abstract: The kinematic modeling method for a wheeled mobile robot is studied. A modeling method called wheel-center modeling (WCM) for kinematics of a wheeled mobile robot that moves on uneven terrain is presented. The vector expression of the wheel center velocity is derived on the basis of analysis of the velocity characteristic of a multi-rigid-body chain structure movement and the roating angular velocity characteristic of wheeled locomotion mechanism moving on uneven terrain. The method of WCM is introduced as a result. A six-wheeled mobile robot, lunar rover, with the rocker-bogie suspension is modeled by using WCM. The presentation of the angular velocity of the rotary joints in the rover centre frame is analyzed and the projection of vector cross product is expressed as different forms according to whether the direction of the angular velocity relatively to rover centre frame changes or not. The wheel centre velocity is projected to the rover body centre coordinate frame with the use of the elements of the homogeneous transformations from the wheel centre frame and the wheel-terrain contact frame to the rover center frame. Thus, the kinematics of the rover is modelled. The procedure of kinematic modeling using WCM is introduced and the characters of WCM is analyzed. The validity of the modeling method is verified by experiment and simulation.

Key words: Kinematics modeling, Lunar roaming rover, Wheel-center modeling, Wheeled mobile robot