This study focuses on implementing robotic peg-in-hole in a more human-like approach, namely using dual-arms and dexterous robotic hands. The peg-in-hole strategy in this study mainly consists of two parts: grasping strategy (hand part) and assembly strategy (arm part). The grasping strategy explains the fundamental grasping method called “advanced blind grasping” and the in-hand manipulation method that is required for the reorientation of the workpiece. A feed-forward task space force control scheme is proposed for the actual implementation. The assembly strategy presents fundamental unit motions called “perturbation pattern” and proposes four assembly stages that are constructed by a combination of the unit motions. A force-position hybrid control for the implementation of the assembly strategy was also addressed. For evaluation, a peg-in-hole assembly demonstration with a keyhole-like shape was conducted using a human-sized 50-DOF upper-body robot.

This study proposes a new way of estimating the hole direction to reduce the search time deviation in peg-in-hole assembly. To perform a peg-in-hole assembly, the hole position has to be found. In our previous studies, we found the hole using a blind search method. The blind search method moves the peg in a predefined path until it finds the hole. However, using blind search, it is difficult to predict the peg-in-hole assembly completion time because hole position search time is different each time. This is because the peg moves along the same predefined path without considering the hole direction. Furthermore, if the direction of the hole is known, the hole search time deviation can be reduced compared to when the direction of the hole is not known at all. Therefore, we propose a new way of finding the hole direction using in-hand manipulation based on `kinesthetic sensing'. Additionally, we introduce the concept of `Free-Finger' for in-hand manipulation. The proposed method uses fingers to find the hole direction and perform the peg-in-hole assembly. Hence, we can implement peg-in-hole assembly regardless of the performance of the manipulator. The feasibility of the proposed method was verified through experiments using a three-fingered gripper.

Conventional assembly methods using robots need to change end-effectors or operate two robot arms for assembly. In this study, we propose a screwdriving gripper that can perform the tasks required for the assembly using a single robot arm. The proposed screwdriving gripper mimics a human-two-handed operation and has three features: (1) it performs pick-and-place, peg-in-hole, and screwdriving tasks required for assembly with a single gripper; (2) it uses a flexible link that complies with the contact force in the environment; and (3) it employs the same joints as the pronation and supination of the wrist, which help the manipulator to create a path. We propose a new gripper with 3 fingers and 12 degrees of freedom to implement these features; this gripper is composed of grasping and screwdriving parts. The grasping part has two fingers with a roll-yaw-pitch-pitch joint configuration. Its pitch joint implements wrist pronation and supination. The screwdriving part includes one finger with a roll-pitch-pitch joint configuration and a flexible link that can comply with the environment; this facilitates compliance based on the direction of the external force. The end of the screwdriving finger has a motor with a hex key attached, and an insert tip is attached to the back of the motor. A prototype of the proposed screwdriving gripper is manufactured, and a strategy for assembly using a prototype is proposed. The features of the proposed gripper are verified through screwdriving task experiments using a cooperative robotic arm. The experiments showed that the screwdriving gripper can perform tasks required for the assembly such as pick and place, peg-in-hole, and screwdriving.

Soft grippers enable to securely grasp objects of various shapes without complex control algorithms. However, the nature of the soft material presents a challenge regarding the attachment of sensors to the fingers, hindering the ability to obtain feedback data on their current state. This study introduces a novel sensor concept designed to be affixed to the fingers of a soft gripper, enabling the measurement of both bending angles and contact forces. The proposed sensor utilizes photo‐reflectors to simultaneously measure bending angles and contact forces at multiple points, with the capability to easily expand the number of measurable cells. To enhance durability, a flexible printed circuit board with proven durability, along with a slip mechanism structure, is incorporated. Through the experiments, the feasibility of the proposed sensor is validated. Also, the durability and long‐term repeatability of the sensor was verified through 100,000 repeated operations.