Advance Modeling of a Skid-Steering Mobile Robot for Remote ...

6.1 Simulink Model 796.1 Simulink ModelThe overall block scheme developed in Simulink for the simulation of three-dimensionalSSMR motion is depicted in Figure 6.1. The block scheme can be divided in three mainparts: the left hand side part represents the high level velocity controller, the central partrepresents the tire reaction force dynamics, and the right hand side part represents the threedimensionalrigid-body motion dynamics. In our case, as the robot is not equipped with anysensor measuring its velocity or the position, the controller provides the left and right-sideangular velocities as feed-forward control input to each wheel, given the desired robot linearand angular velocity as reference signals, by inverting the kinematic relation in (2.11) andwithout considering the wheel slip. The reason why we do not consider the wheel slip isbecause we can not have any information on the wheel center velocities, due to the absenceof velocity sensors.Figure 6.1: Block scheme of the Simulink model.The block for the three-dimensional rigid-body motion dynamics simply implements thegeneralized dynamic model in (2.65) and provides the robot position q, velocity V and acceleration˙V given the resultant force and torque vector F, as depicted in Figure 6.2(a). Asthe simulation is mainly performed for the robot swiveling in place, i.e. v x = 0, ω z 0, theproduct between the linear and angular velocities of the robot is relatively low with respectto its linear and angular accelerations, so that the Coriolis term M ˆVV is negligible. Thereby,in order to simplify the model and reduce the computational time, the Coriolis term was notincluded in the Simulink block.