Application of Stable Inversion to Flexible Manipulators Modeled by the ANCF

TL;DR

This paper presents a simplified stable inversion method for controlling flexible manipulators modeled by ANCF, enabling better performance by addressing internal dynamics without complex derivations.

Contribution

It introduces an approximation of stable inversion that simplifies control design for complex flexible robots with many unactuated degrees of freedom.

Findings

Improved control performance for flexible manipulators.

Applicable to systems with many unactuated degrees of freedom.

Simplifies the stable inversion process.

Abstract

Compared to conventional robots, flexible manipulators offer many advantages, such as faster end-effector velocities and less energy consumption. However, their flexible structure can lead to undesired oscillations. Therefore, the applied control strategy should account for these elasticities. A feedforward controller based on an inverse model of the system is an efficient way to improve the performance. However, unstable internal dynamics arise for many common flexible robots and stable inversion must be applied. In this contribution, an approximation of the original stable inversion approach is proposed. The approximation simplifies the problem setup, since the internal dynamics do not need to be derived explicitly for the definition of the boundary conditions. From a practical point of view, this makes the method applicable to more complex systems with many unactuated degrees of freedom. Flexible manipulators modeled by the absolute nodal coordinate formulation (ANCF) are considered as an application example.