Estimate a Flexible Link’s Shape by the Use of Strain Gauge Sensors

This paper presents a method for estimating the flexible link’s shape by finite number of sensors. The position and orientation of flexible link are expressed as a function of curvature of the link. An interpolation technique gives this continuous curvature function from a finite set of the Wheatstone bridge made with strain gauges. For interpolation we can use different functions to find better way for estimation of link’s shape. Comparison between different types of function can show us best corresponding with nature of the link. Our case study is a single flexible link robot. A high-precision data logger is used as data acquisition instrument. 1. Introduction Research into flexible manipulator fields has become more important for more than a decade on account of new robotic applications in different areas such as industrial tasks in which the trend is to use lightweight materials (e.g., carbon fiber and composites) in the structures of manipulators in order to improve the performance of the industrial robots which are large and heavy. In aerospace applications the lightness of the materials is also an important requirement; the control of large structures, such as boom cranes and fire rescue turntable ladders, which are treated as flexible link robots is discussed by [1, 2]; minimally invasive surgery is performed with thin flexible instruments in which precise automatic manipulators are necessary [3]. These flexible manipulators exhibit important advantages in comparison to rigid ones, such as reduce energy consumption, smaller actuators, safety for humans, and more agility. Moreover, the effects of the collision with obstacles or humans are decreased because of the flexibility of the links. In spite of these advantages, the control problem of the flexible link manipulators becomes more complicated because the structural flexibility has to be controlled in such a way that the vibrations are cancelled if a good tip position and/or force control is to be gained. Most of the work in the field of elastic robotic manipulator is confined to theoretical investigations. For validation the theoretical results by experimental testbed, it can be pointed out to the works of Cannon and Schmitz [4] as a pioneer in experimental study of single-link elastic robotic manipulator. Naganathan and Soni [5] also prepared an experimental setup composed of a single-link mounted on a stepper motor to verify their FEM results. Bellezza et al. [6] conducted experiments to study quasi-clamped and quasi-pinned end conditioned in slewing links. Luo [7] used a strain gauge sensor