A New Approach to Dynamic Modeling of Continuum Robots

ABSTRACT In this thesis, a new approach for developing practically realizable dynamic models for continuum robots is proposed. Based on the new dynamic models developed, a novel technique for analyzing the capabilities of continuum manipulators to be employed in various real world applications has also been proposed and developed. A section of a continuum arm is modeled using lumped model elements (masses, springs and dampers). It is shown that this model, although an approximation to a continuum structure, can be used to conveniently analyze the dynamics of the arm with suitable tradeoff in accuracy of modeling. This relatively simple model is more plausible to implement in an actual real-time controller when compared to other techniques of modeling continuum arms. Principles of Lagrangian dynamics are used to derive the expressions for the generalized forces in the system. The force exerted by McKibben actuators at different pressure level - length pairs is characterized and is incorporated into this dynamic model. The constraints introduced in the analytical model conform to the physical and operational limitations of the Octarm VI continuum robot manipulator. The model is validated by comparing the results of numerical simulation with the physical measurements of a continuum arm prototype built using McKibben actuators. Based on the new lumped parameter dynamic model developed for continuum robots, a technique for deducing measures of manipulability, forces and impacts that can be sustained or imparted by the tip of a continuum robot has been developed. These measures are represented in the form of ellipsoids whose volume and orientation gives information about the various functional capabilities (end effector velocities, forces and impacts) of the arm at a particular configuration. The above mentioned ellipsoids are exemplified for different configurations of the continuum section arm and their physical significances are analyzed. The new techniques proposed and methodologies adopted in this thesis supported by experimental results represent a significant contribution to the field of continuum robots