The multi-segment controller of a flexible arm

Abstract:
The aim of this paper is to present an active and effective method for shaping the local three-dimensional deformation. It is based on a proposed device called a “segment controller” and it can reduce vibrations of flexible structures like for example, a lightweight robot arm. One possible solution is an appropriate local controller that uses the principle of energy flow, measured at arm nodes. The designed controller consists of a chain of active piezoelectric segments. The control force is determined on the basis of the local stress measurement of the current segment and its neighbours. The segment controller uses the RST (Reference Signal Tracking) structure, so tracking and regulation can be tuned independently. Its coefficients were determined from symbolic manipulations of Diophantine equation. In order to examine the capabilities of the method the linearized robot arm model is considered. The transfer functions of the system in question were derived using the FEM method with 5- order Hermite polynomials as base functions. Model is tuned with the innovative templates method, which allows getting the best match for the assumed criteria. The results of simulation tests show that the proposed „segment controller‟ reduces vibration of a flexible light arm effectively, changes the arm deflection, and is resistant to damage to some chain segments. It has been shown that the robustness of the device strongly depends on the location of segment actuators along the flexible arm, and is high for distribution in accordance with the principle of the „golden section‟.