End effectors or grippers are an essential tool integrated with robotic arms for achieving grasping and manipulating functions in a variety of tasks, ranging from picking up and holding objects, to digging and sorting, to locomotion and scratching. Soft end effectors capable of grasping objects dexterously and efficiently have attracted increasing attention in a broad range of applications involving robot-human and robot-environment interactions. A variety of proprioceptive sensors are integrated with the grippers, examples of which include tendon tension sensors, torque sensors, encoders, and Hall-effect sensors, to determine the position and velocity of the gripper components, while different kinds of exteroceptive sensors like pressure sensors, electromagnetic sensors and resistive and capacitive sensors are deployed to gather sensory information about the physical properties of the objects. In this study, we present a new smart soft gripper capable of fast-speed responding, pressure sensing and self-powering by combing the cable-driven mechanism with integrated soft sensor and triboelectric nanogenerator (TENG) design. The fingers of the smart organism-like adaptive gripper can move, sense and respond like human hands and simultaneously harvest energy from the contact touches to drive the pressure sensors in operation. Based on the modular design approach, the soft finger is made of silicone rubber and actuated by miniature DC motors. A 3-finger configuration is utilized for the integration of the soft gripper, and each soft finger is designed with three phalanx structures separated by triangular cuts with an angle of 45°. When actuated, the soft finger can bend to form a stable enveloping grasp profile to perform grasp actions. A cavity chamber penetrating through the finger’s length is designed to facilitate its bending and to accommodate a curvature sensor. In addition, a soft silicone-based TENG is attached onto the surfaces of the phalanxes as robotic skins for detecting contact pressures. To improve the sensitivity of the tribo-skin, we have patterned triangular microprisms on top of the skin. The tribo-skins possess good compatibility with the soft finger to actively detect proximity, contact and pressure to external stimuli via self-generated electricity. Another flexible TENG consisting of a PTFE film and copper electrodes is also added into the cavity chamber of the finger to measure its bending curvature. Results demonstrate that these two kinds of TENGs have good structural stability and high space utilization, while being able to harvest mechanical energy to light up several light-emitting diodes, charge various capacitors and drive miniature electronic products. Based on the modular design approach, a gripper with three fingers is fabricated and tested for its grasping, sensing and energy harvesting performance. This gripper is capable of picking up different kinds of objects, providing sensory feedback, and generating energy, which shows great potential for use in robot-human and robot-environment interaction applications.


Smart Soft Actuators and Grippers Enabled by Self-Powered Tribo-Skins

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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