Fault tolerant N-DOF Gough-Stewart platforms: Kinematics, dynamics, and design

N-DOF Gough-Stewart platforms (GSPs) can make mountings more flexible as well as more tolerance of failures which cannot be tolerated by traditional six degree-of-freedom (DOF) manipulators. This dissertation extends the fundamental technology underlying the hexapod to N-DOF. There are four major contributions to the research of flexure jointed GSPs. First, the kinematic analysis of general constrained parallel manipulators is extended to the over-constrained case. The results show that the redundant constraints lead to constrained active joints and redundant internal force. For the special case of a GSP, the relationships between the forward Jacobian and the inverse Jacobian are also found. Second, the effects of various failures and the corresponding fault tolerance strategies are discussed. It is found that position failures result in an over-constrained mechanism, while torque failures and hard failures can be tolerated by designing the nominal manipulator to be over-constrained. New, efficient ways to calculate the post-failure kinematics are also introduced. Third, the kinematics, dynamics and control of six-DOF GSPs are extended to a more general N-DOF case. The dynamic implementation of optimization for prioritized mechanisms and fault tolerance strategies are also discussed. Finally, a geometric approach to generate a class of orthogonal GSPs is developed. Fault tolerant measures are proposed and are used to optimize a nine-strut manipulator to achieve best tolerance of torque failures or hard failures.