Curvature Based Point Stabilization and Path following for Compliant Framed Wheeled Modular Mobile Robots

The compliant framed modular mobile robot is a new type of wheeled mobile robot for which the motion control problems of posture stabilization, path following, and trajectory tracking are studied. This robot has the advantages of a simple modular design that provides full suspension and steering capability without any additional components. Due to the flexible nature of the robot, the kinematics are much more complicated than typical mobile robot designs. It is shown that an equivalent curvature based model that improves mobility and reduces required traction forces can describe the kinematics. A time invariant control law is developed for the posture stabilization problem and extended to compensate for nonideal initial conditions and system drift. It is shown through Lyapunov stability analysis that provided a special choice is made for the robot velocity and curvature, the system will stabilize to the origin. The trajectories generated are smooth and meet the desired requirements of the equivalent curvature based model. A similar control law is developed for the path following problem, and it is shown that this control law may also be utilized in the posture stabilization case. Hence, a single control law may be used for both the path following and posture stabilization problems. The control laws developed are tested in simulation, and experimentally on the Partially Compliant Test Robot at the University of Utah. The results are presented and show the proposed control laws perform as expected in the point stabilization, path following, and trajectory tracking cases.