The objective of this work is to control a delivery robot equipped with a passive bogie that can successfully climb up steps of various sizes and move on uneven terrain in outdoor environments. The kinematic model of a six-wheel mobile robot is described in detail. Jacobian matrices and inverse kinematics are obtained to get the velocity of each wheel based on the desired velocity of the robot center of mass in conjunction with the terrain information obtained by the onboard sensors according to the contact angle estimation between the wheel and ground. A slip control is implemented based on slip ratio to adjust the wheel velocity when the slip is detected. Simulation and experimental results verify the effectiveness of the approach that enables the robot autonomously climbing up on different steps and uneven terrain.