Pre-Charged Pneumatic Soft Gripper With Closed-Loop Control

Pneumatic soft grippers have nonlinear continuum deformation enabling them to adapt to irregular object shapes. Most of the existing pneumatic soft grippers use only open-loop control. Attempts for closed-loop control of soft grippers are all based on air pressure regulation, which is inaccurate and cumbersome due to nonlinear performance of the soft actuator and the compressible nature of air. In this letter, we present a controllable soft gripper based on pre-charged pneumatic soft actuators. The soft actuators, with the same design as a normal bending pneumatic soft actuator, are pre-charged with air to a preset pressure through a one-way check valve. The bending angle and bending speed of soft actuators are controlled by servomotors through tendons based on feedback data from force and proximity sensors. Kinematic models of the soft actuators are developed. Dynamic properties are experimentally studied. A prototype gripper with closed-loop control is developed for controllable grasping demonstration.