Mechatronic design of flexible manipulators

Abstract

The construction of lightweight manipulators with a larger speed range is one of the major goals in the design of well-behaving industrial robotic arms. Their use will lead to higher productivity and less energy consumption than is common with heavier, rigid arms. However, due to the flexibility involved with link deformation and the complexity of distributed parameter systems, modeling and control of flexible manipulators still remain a major challenge to robotic research. A compromise between modeling costs and control efficiency for real-time implementation is inevitable. The interdependency of subsystems results in a local optimal performance in the traditional design scheme. An important research topic in flexible manipulator design is the pursuit of better system performance while avoiding model-intensive or control-intensive work. This problem can be solved using the proposed mechatronic design approach. It treats the mechanical, electrical and control components of a flexible manipulator concurrently. The result is an improved design with an explicit link shape and controller parameters which result in the control problem and modeling accuracy no longer being critical for obtaining desired performance. Dynamics of flexible manipulators with rotatory inertia are derived, and state-space equations with the integration of DC motor dynamics are developed as a theoretical base for mechatronic designs. Two case studies based on LQR formula and Hinfinity control are considered. The beam shape and controller parameters are obtained using an adaptive iterative algorithm with the accommodation of various geometrical constraints. Also, different output feedback strategies are investigated to evaluate the impacts of various controller structures. Finally, a sensitivity analysis in terms of parameter variations and model uncertainties is conducted to reveal the robustness of this mechatronic design.