Design of a controller for the pneumatic flow control valve and pressure regulation for application related to pneumatically powered orthosis

Abstract

An assistive limb or powered orthosis helps to overcome the physical disability of the differently able. Though conventional orthosis are designed using electrical actuators, a pneumatic actuator proves itself more suitable and preferable with its low cost and clean driving source (i.e. air). A portion of the pneumatically powered orthosis design is addressed in this work. Here an attempt has been made to overcome the issues namely valve damage and pressure drop in air tank. Also a special emphasis is given on controlling the flow-control valve which plays a crucial role in setting the angular velocity of the hip-joint and regulating the input pressure to the pneumatic actuator. For this a PID controller is designed and programmed into a ATmega328 micro-controller. The PID controller response was satisfactory and a desired pressure (1 to 2 bar) corresponding to desired angular velocity (0 to 10 rad/s) was achieved. The powered orthosis is a mobile system and therefore a wireless data acquisition system is designed to retrieve the hip joint angle as primary feedback.