Estimation of Transmission Force in Assistive Devices using Conductive Liquid Metal based Sensorized Pneumatic Artificial Muscle

The article presents a technique to estimate the force transmitted in pneumatic artificial muscle based assistive devices by sensorizing the actuator. For this purpose, the development of a conductive liquid metal based elastomeric strain sensor has been discussed with the required characterization of its performance. A comparative analysis is shown between the modes of attachment of the developed sensor on the actuator so as to obtain a proper range of response from the sensor. A two-step algorithm has been implemented to estimate the force transmitted in series from an actuator used to assist the human knee and ankle during walking. The estimation results are validated against the readings from an actual inline loadcell, showing good agreement with one another.