This paper proposes a novel robotic hand design for assembly tasks. The idea is to combine two simple grippers -- an inner gripper which is used for precise alignment, and an outer gripper which is used for stable holding. Conventional robotic hands require complicated compliant mechanisms or complicated control strategy and force sensing to conduct assemble tasks, which makes them costly and difficult to pick and arrange small objects like screws or washers. Compared to the conventional hands, the proposed design provides a low-cost solution for aligning, picking up, and arranging various objects by taking advantages of the geometric constraints of the positioning fingers and gravity. It is able to deal with small screws and washers, and eliminate the position errors of cylindrical objects or objects with cylindrical holes. In the experiments, both real-world tasks and quantitative analysis are performed to validate the aligning, picking, and arrangements abilities of the design.
There are also designs that use sensors and feedback control to implement the desired functions. For example, @cite_19 designed a parallel gripper with embedded vision and force feedback to adjust poses and perform insertion tasks. @cite_2 developed a swivel mechanism to sense and position the surface of target objects. It is also an example of positioning using sensors.
@cite_19 @cite_2
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In electronic manufacturing system, the design of the robotic gripper is important for the successful accomplishment of the assembly task. Due to the restriction of the architecture of traditional robotic hands, the status of assembly parts during the assembly process cannot be effectively detected. In this research, an intelligent robotic gripper - i-Hand equipped with multiple small sensors is designed and built for this purpose, getting the essential parameters for some specific mathematical model. Mating connectors by robot, as an experimental case in this paper, is studied to evaluate the performance of i-Hand. A simple new model is proposed to describe the process of mating connectors, within which the distance between the connector and deformable Printed Circuit Board (PCB) is detected by i-Hand. An online Fault Detection and Diagnosis (FDD) algorithm is proposed. Various possible situations during assembly are considered and handled according to an event driven work flow. The effectiveness of proposed model and algorithm is proved by the experiments. Tactile sensors are numerous and varied, and the data they provide has proven advantages in industrial and consumer products. Despite this fact, these sensors are not used to their full potential. This illustrates the need for low-cost, versatile tactile sensors. In this paper we introduce novel robotic fingertips that use low-cost components coupled with mechanical ingenuity in order to attain important and high-quality tactile data. Our robotic fingertips contain a rolling mechanism, and can sense the force applied to an object, the normal direction of the contact point, as well as parallel movement along the object's surface. We show three main uses for this fingertip. Firstly, we demonstrate how the fingertips can be used for the detection of soft or lightweight objects by applying extremely small forces to them. Secondly, we present a method of full-perimeter definition (location and normal direction) of rigid objects by tracing. Lastly, we explain how our sensors can be used to detect stiffness and stiffness anomalies in soft objects, such as organic tissue.