The vision analysis of a McKibben pneumatic artificial muscle

Abstract

The McKibben pneumatic artificial muscles are biomimetic actuators, which contract and generate force when inflated. They are lightweight, robust and have very high generated force to weight ratio. Because of these features they are widely used in robotics, orthotics and prosthetics. However, generated force has nonlinear character and is dependent on both pressure inside of a muscle and its contraction. It behaves somewhat like a spring. As a result, the generated force of pneumatic artificial muscle is hard to control. This study presents an algorithm for vision measurement of an operating pneumatic artificial muscle. The diameter and contraction of an artificial muscle is measured under different operating pressures. The purpose of this study is the analysis of a vision system as an alternative tool for measuring characteristics of pneumatic artificial muscles in real applications. One of the advantages of a vision system is a fact, that single camera sensor is able to measure more than one artificial muscle. Control algorithms of pneumatic muscles use PWM method to control pressure. To achieve PWM method very fast 2/2 pneumatic valves are used to control input and output flow. In this study a pneumatic muscle is used to control slider position. A vision analysis of a such system is presented. To capture images of fast changing process a high-speed camera is used.