Modeling and Analysis of a Novel Passively Steered 4WD Mobile Platform Concept

Applications in the field of mobile robotics have high demands on flexibility and maneuverability of mobile platforms. Especially in logistics, vehicles have limited space for the movement. This paper presents the analysis and control of a mobile platform which uses a novel steering principle. The considered vehicle is able to perform a steered forward movement, lateral motion or pure rotation without the need of steering motors. The kinematics is analyzed and a kinematic model is derived. For simulation a dynamic model formulated in terms of redundant coordinates is used. A control scenario where reference values are commanded by a joystick is presented. For feedforward control design, a reduced dynamic model based on minimal velocities and the kinematic model are used. For feedback control, a cascaded structure with an inner velocity loop for the wheels and a superimposed steering control is used. The efficiency of the presented control approach is demonstrated by simulation results.