A 3 DOFs Mini Variable Stiffness Soft Pneumatic Actuator

Abstract

Surgical robots for minimal access surgery are used to enhance surgeons' performance by motion scaling and reduction of physiological tremor. The advantages of rigid robots include high precision and fast movements. However, an active control is needed for safe interaction with organs and tissues. By contrast, soft robots are intrinsically safe; however, they have limited precision movements because of their low stiffness. In the present study we describe a mini soft pneumatic cylindrical actuator that can change its stiffness by means of antagonistic tendons. The actuator has 3 degrees of freedom (DOFs), an external diameter of 12 mm, length of 15 mm, weight of 1.5 g, and a maximal activation air pressure below 60 kPa (0.60 atm). We report the design of the i) soft actuator, ii) range of motion data, iii) output force and torque, and iv) its variable stiffness under external load.