2011 Volume 42 Issue 1 Pages 1-6
The applications of pneumatic artificial muscles (PARM) are increasing in the power assist and manipulator systems, since they have advantages such as high power weigh ratio and flexibility. Usually, we have to measure the contract ratio of PARM using a displacement sensor installed near the actuator, which is not preferable from the aspect of preventing dust and water. In this paper, we propose a method of estimating contraction force from the volume change of the PARM, which makes it possible to have a sensor-less actuator. The air charged to and discharged from the PARM is measured by a quick response laminar flow meter. The volume of the PARM is estimated from the flow rate and the pressure measured by a pressure sensor. In order to estimate the contraction force accurately, thin copper wires are stuffed in to the PARM to realize an almost isothermal condition during charge and discharge. The effectiveness of the proposed method is confirmed experimentally.
