Working and Limitations of Cable Stiffening in Flexible Link Manipulators

Rahul Dixit,R Prasanth Kumar

doi:10.1155/2016/4503696

Abstract

Rigid link manipulators (RLMs) are used in industry to move and manipulate objects in their workspaces. Flexible link manipulators (FLMs), which are much lighter and hence highly flexible compared to RLMs, have been proposed in the past as means to reduce energy consumption and increase the speed of operation. Unlike RLM, an FLM has infinite degrees of freedom actuated by finite number of actuators. Due to high flexibility affecting the precision of operation, special control algorithms are required to make them usable. Recently, a method to stiffen FLMs using cables, without adding significant inertia or adversely affecting the advantages of FLMs, has been proposed as a possible solution in a preliminary work by the authors. An FLM stiffened using cables can use existing control algorithms designed for RLMs. In this paper we discuss in detail the working principle and limitations of cable stiffening for flexible link manipulators through simulations and experiments. A systematic way of deciding the location of cable attachments to the FLM is also presented. The main result of this paper is to show the advantage of adding a second pair of cables in reducing overall link deflections.

Highlights

Robot manipulators used in industry spend much of their energies in moving their end effectors from one point to another
Moving a payload at the end effector of flexible link manipulators (FLMs) to desired location at the specified time requires special control algorithms designed taking into account the underactuated nature of FLMs
The flexible link manipulator studied in the paper is modeled using finite segment method

Summary

Introduction

Robot manipulators used in industry spend much of their energies in moving their end effectors from one point to another. Their links are designed to have very low deflection which makes them bulky. Moving a payload at the end effector of FLM to desired location at the specified time requires special control algorithms designed taking into account the underactuated nature of FLMs. In order to minimize the tip vibration of FLMs, several researchers have analyzed the problem in different ways. Kiran et al [11] presented bond graph technique for modeling a single link flexible space manipulator. Baroudi et al [19] presented their study on control of flexible manipulator using LQR technique. Several authors have used closed loop control methodologies by modeling flexible

Mathematical Model and Simulation

Deflection Analysis and Cable Attachment Location

Experimental Setup and Validation

Findings

Conclusions