Grasping model and experiment of a soft robot gripper with variable stiffness

This research presents a soft robot gripper, which possesses variable stiffness resulting from shape memory alloy (SMA)-1 fiber and actuated by SMA-2 wires. To investigate the grasping capacity of the soft robot gripper, both the theoretical models of the variable stiffness of SMA fiber and grasping force of a soft robot finger are introduced. Based on the theoretical analysis, the grasping force of the soft finger doesn't produce before the finger contacts with the object under the work of the SMA-2 wires, moreover can be affected from the rigidity of SMA-1 fiber. To verify the analytical results, the soft robot finger with variable stiffness is designed and an experimental setup is built to measure the grasping force. The experimental and simulation results are compared. To check the grasping ability of the soft robot gripper, a two-finger grasping experiment is conducted. The experimental results of the soft robot gripper with variable stiffness indicate that the grasping force of the soft robot gripper has increased with the growth of its stiffness, and the grasping ability of the soft robot gripper grows at least 40%.