Controlling bending deformation of a shape memory alloy-based soft planar gripper to grip deformable objects. (1st March 2021)

• Record Type: Journal Article
• Authors: Wang, Wei; Tang, Yunxi; Li, Cong
• Is Part Of: International journal of mechanical sciences. Volume 193(2021)
• Publication Date: 2021-03-01
• Subjects: Soft grippers -- soft robots -- smart materials -- deformation control; Mechanical engineering -- Periodicals; Génie mécanique -- Périodiques; Mechanical engineering; Maschinenbau; Mechanik; Zeitschrift; Periodicals; 621.05
• DOI: 10.1016/j.ijmecsci.2020.106181
• Languages: English
• ISSNs: 0020-7403

Abstract

Highlights: First attempts to automatically control the deformation of SMA-based soft gripper. Establishing a closed-loop PID control system with a camera as a vision sensor to detect and control the bending deformation of the soft finger in real-time. Utilizing a SMA-based soft planar gripper with the desired deformation to successfully grip deformable objects. Abstract: Integrating flexible sensors into a soft finger is a common approach to control the deformation of the finger. However, adding sensors, especially sensors with a degree of stiffness, sacrifices the overall compliance of the finger structure and increases the complexity of fabrication and control. This study provides an alternative approach, without the need for integrated sensors, to control the deformation of a shape memory alloy (SMA)-based soft planar gripper for grasping deformable objects. The gripper consists of one soft finger which is an SMA-based hinge actuator capable of producing hinge-like bending deformation. The soft finger can automatically achieve the desired deformation by introducing a closed-loop PID control system. A camera as a vision sensor, instead of integrated flexible sensors, was used to detect the bending deformation of the soft finger in real-time. With the feedback from the camera, the PID controller was implemented in a microcontroller with designed external circuits, to enable the soft finger to reach any targeted bending angle within its deformation range, according to the size of the manipulated object. As a demonstration, the soft planar grippers with the desired deformation were eventually used to grip deformable objects, including flowers and a panicle. Without the need for material characterization and analytical models, the proposed method can also be extended to other soft planar grippers based on different actuation techniques. Graphical abstract: Successful manipulation is demonstrated using the SMA-based soft planar grippers with the desired deformation to grip the delicate and deformable objects, including flowers and a panicle. Image, graphical abstract