Actively coordinated wheeled vehicle systems

This research effort is directed towards actively coordinated wheeled vehicle systems, a class of advanced mobility systems that are suited for operation on unstructured terrain. Actively coordinated vehicles refer to vehicles that possess the ability to influence the contact forces at the vehicle-terrain contact locations, and the ability to vary their configuration to accommodate to terrain obstacles. Unlike legged locomotion systems, wheeled systems do not possess omni-directional motion capability. This leads to nonholonomic kinematic constraints that cause unique complications in wheeled systems.; This dissertation addresses the issues of force planning, motion planning, dynamic simulation, and autonomous navigation of actively coordinated wheeled systems operating on uneven terrain. The work also includes design, fabrication, and preliminary experimental testing of the {dollar}rm{lcub}underline W{rcub}{dollar}heeled {dollar}rm{lcub}underline A{rcub}{dollar}ctively {dollar}rm{lcub}underline A{rcub}{dollar}rticulated {dollar}rm{lcub}underline V{rcub}{dollar}ehicle (WAAV) in a laboratory environment. Even though this research effort is primarily directed towards actively coordinated wheeled vehicles, some results obtained during the course of this work are also applicable to other actively coordinated mechanisms.; Inertial sensing is used in robotic systems to obtain orientation and the angular rates of the vehicle body for control purposes, and to obtain absolute vehicle position on the terrain for the purpose of guidance. In the absence of accurate maps of the environment, inertial sensing systems can possess significant drift errors. In this work, a drift-free star sensor based navigation scheme is investigated, and its relative advantages and disadvantages as compared to existing systems are studied.; The redundancy in the force allocation problem of actively coordinated legged and wheeled systems has been studied using geometric reasoning. The nature of the nonlinear optimal force distribution problem has been examined. The optimization schemes developed include globally optimal algorithms that utilize advanced polynomial continuation techniques. On uneven terrain, the configuration of the wheeled vehicle is greatly affected by the local terrain geometry. The kinematic mobility of this configuration on uneven terrain, and the position kinematics of the resulting hybrid series-parallel chain have been studied. These position kinematic solutions have been used as the basis for developing motion planning algorithms.; A dynamic simulator capable of handling the motion of articulated wheeled vehicles on uneven terrain has been developed. A contact model that incorporates a three-dimensional spring/damper system at the wheel-terrain contact locations has been used to simulate the phenomena of rolling and slipping of the wheels.; Preliminary experiments with the {dollar}rm{lcub}underline W{rcub}{dollar}heeled {dollar}rm{lcub}underline A{rcub}{dollar}ctively {dollar}rm{lcub}underline A{rcub}{dollar}rticulated {dollar}rm{lcub}underline V{rcub}{dollar}ehicle (WAAV) have been performed. In this work, the mechanical and electrical hardware has been tested, the WAAV has been interfaced to a personal computer, and basic testing of simple mobility maneuvers in a laboratory setting has been attempted.