This study presents the design of an underactuated, two-finger, motor-driven compliant gripper for grasping size-varied unknown objects. The gripper module consists of one main frame structure and two identical compliant fingers. The compliant finger is a monolithic compliant mechanism synthesized using a topology optimization method, and then prototyped by 3D printing using flexible filament. The input port for each finger is mounted on a moving platform driven by a gear motor, whereas the fixed port of the finger is mounted on a fixed platform. Each compliant finger can be actuated through the linear motion of the moving platform, and can deform elastically to generate the grasping motion. To demonstrate the effectiveness of the proposed design, the gripper module is mounted on a six-axis robotic arm to pick and place a variety of objects. The results show that objects with the sizes between 42 and 141 mm can be grasped by the developed soft robotic gripper. The maximum payload for the gripper is 2.1 kg. The proposed compliant gripper is a low-cost design that can be used in grasping of size-varied vulnerable objects.

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SummaryThis study presents an optimal design procedure including topology optimization and size–shape optimization methods to maximize mechanical advantage (which is defined as the ratio of output force to input force) of the synthesized compliant mechanism. The formulation of the topology optimization method to design compliant mechanisms with multiple output ports is presented. The topology-optimized result is used as the initial design domain for subsequent size–shape optimization process. The proposed optimal design procedure is used to synthesize an adaptive compliant gripper with high mechanical advantage. The proposed gripper is a monolithic two-finger design and is prototyped using silicon rubber. Experimental studies including mechanical advantage test, object grasping test, and payload test are carried out to evaluate the design. The results show that the proposed adaptive complaint gripper assembly can effectively grasp irregular objects up to 2.7 kg.

This study presents a topology optimization method to synthesize an innovative compliant finger for grasping objects with size and shape variations. The design domain of the compliant finger is a trapezoidal area with one input and two output ports. The topology optimized finger design is prototyped by three-dimensional (3D) printing using flexible filament, and be used in the developed gripper module, which consists of one actuator and two identical compliant fingers. Both fingers are actuated by one displacement input, and can grip objects through elastic deformation. The gripper module is mounted on an industrial robot to pick and place a variety of objects to demonstrate the effectiveness of the proposed design. The results show that the developed compliant finger can be used to handle vulnerable objects without causing damage to the surface of grasped items. The proposed compliant finger is a monolithic and low-cost design, which can be used to resolve the challenge issue for robotic automation of irregular and vulnerable objects.