Decomposed dynamic control for a flexible robotic arm in consideration of nonlinearity and the effect of gravity

Haibin Yin,Junfeng Li,Yongguang Li

doi:10.1177/1687814017694104

Abstract

This article presents a nonlinear dynamic model of a flexible robotic arm considering nonlinearity from elastic deformation and the effect of gravity. The dynamic model can be decomposed into separate flexible and rigid subsystems. A decomposed dynamic control, including flexible and rigid dynamic controls, is proposed for the controller of the flexible robotic arm. Optimization is used in this flexible dynamic control to obtain the desired trajectory and can deal offline with strong nonlinearity, but it is excessively dependent on the accuracy of the model, so it is not robust enough and has poor disturbance-rejection capabilities. The rigid dynamic control, by contrast, is expected to be sufficiently robust to compensate for uncertain factors. Therefore, a hybrid sliding mode control is proposed to track the desired trajectory and further suppress residual vibration. Additionally, the actual flexible modes are estimated to accurately calculate the component of the proposed controller. This study addresses the theoretical derivation and experimental verification of the proposed controller.

Highlights

Flexible robotic arms have the potential advantages of higher payload-to-weight ratio, faster motion, and lower energy consumption
According to studies on flexible robotic arms, the reported approaches that describe elastic deformation can be classified into three groups: The most widely used method is the linear description of deformation;[2,3] over the past few decades, several publications have discussed the quadratic deformation approach;[4,5] Lee[6] proposed a new description of elastic deformation that synthetically considers the transverse deflection and axial shortening as a vector representing flexible displacement to derive the dynamic model of a one-link flexible beam
This study adopted a new description of elastic deformation on the flexible beam and considered the effect of gravity to formulate a dynamic equation for a flexible robotic arm

Summary

Introduction

Flexible robotic arms have the potential advantages of higher payload-to-weight ratio, faster motion, and lower energy consumption. The model consists of a rigid link and a flexible beam which is mounted on the second rotational joint with a hub. The nonlinear dynamic equations of the flexible robotic arm are obtained as the following compact form u€ + q€

Results

Conclusion