A novel robotic gripper with soft surfaces and underactuated joints was proposed. The soft surface was fabricated from a deformable rubber bag filled with incompressible fluid and a microgripper inside the fluid. A ratchet was installed at the underactuated joint so that the joint's rotation caused by contact with an environment, such as a supporting surface, can be preserved, and the actions of scooping and enveloping an object are realized. With one actuator, the gripper realized three modes, i.e., parallel gripper, pinching, and enveloping. The range of graspable objects was wide and included soft, rigid, deformable, fragile, small (boundary length less than 30 mm), large (more than 80 mm long), thin (less than 0.5 mm), and heavy (more than 3 kg) objects.

In this paper, we investigate optimal grasp points on an arbitrary-shaped grasped object using a required external force set. The required external force set is given based on a task, and consists of the external forces and moments, which must be balanced by virtue of contact forces applied by a robotic hand. When the origin is in the interior of the set, a force-closure grasp is required. When the dimension of the set is one, an equilibrium grasp is required. Therefore, we can investigate whatever the desired grasp is, such as when the desired grasp is a force closure and equilibrium grasps. Also, we only have to consider the forces contained in a given required external force set, not the whole set of possible resulting forces. Furthermore, we can avoid the frame-invariant problem (the criterion value changes with the change of the task (object) coordinate frame). We consider an optimization problem from the viewpoint of decreasing the magnitudes of the contact forces needed to balance any external force and moment contained in a given required external force set. In order to solve the problem, we present an algorithm based on a branch-and-bound method. We also present some numerical examples to show the validity of our approach. Note to Practitioners-This paper is concerned with grasping an object by a robotic hand. This article address how to grasp the object, namely, how to position every finger on the object. Recently, robots are desired to be used in housekeeping and in caring for elderly people. For this purpose, robot (multifingered) hands are equipped with the robots as general-purpose end effectors. The robot hands are required to automatically move to accomplish such tasks. In this case, the most fundamental issue for robot hands is to grasp the object. At home, there are many various-shaped objects. Consider the case where the robot (hand) is commanded to perform a certain task, such as putting the object into a box. In this case, the robot (hand) must grasp such an object (of any arbitrary shape) with appropriate grasp positions for completing the task. Therefore, the appropriate grasp positions must be calculated automatically. This article addresses a method to solve this problem. But to complete the grasping task, the following problems remain: calculation and control of the appropriate grasping forces

Aiming at accelerating the creation of new techniques on dexterous robotic manipulations, this paper surveyed the recent results on object recognition, soft robotic hands, and benchmarks and challenge/competition programs. The former two topics construct the elemental components of the new technologies on robotic manipulations, while the last one is a key for proceeding the creation and realization of the actual robotic manipulations with the new techniques. With these surveys, we will reveal the solved and unsolved issues for the next step to realize robotic dexterous manipulation systems comparable to human being.

This study presents a novel four-fingered robotic hand to attain a soft contact and high stability under disturbances while holding an object. Each finger is constructed using a tendon-driven skeleton, granular materials corresponding to finger pulp, and a deformable rubber skin. This structure provides soft contact with an object, as well as high adaptation to its shape. Even if the object is deformable and fragile, a grasping posture can be formed without deforming the object. If the air around the granular materials in the rubber skin and jamming transition is vacuumed, the grasping posture can be fixed and the object can be grasped firmly and stably. A high grasping stability under disturbances can be attained. Additionally, the fingertips can work as a small jamming gripper to grasp an object smaller than a fingertip. An experimental investigation indicated that the proposed structure provides a high grasping force with a jamming transition with high adaptability to the object's shape.

This paper presents a gripper with fingertips constructed from incompressible fluid covered by rubber with the aim of grasping very fragile objects. Owing to the incompressibility, simply closing the gripper allows the fingertips to approach the target object with low stiffness; after contact, the contact stiffness increases with increasing fingertip deformation, and grasping with high stiffness can be realized. The adaptation of the fingertips to the object shape and a uniform contact pressure are further benefits of the proposed system. Fragile and brittle objects can be grasped by controlling the contact pressure so that it does not exceed the fracture stress/pressure. We found that the initial sign of fracture appears before total fracture when soft and ductile objects are grasped. Based on this phenomenon, we developed a strategy for grasping ductile objects without any advance knowledge of fracture. The proposed fingertips have a rigid layer inside the fluid to grasp objects with normal rigidity. The effectiveness of the fingertips was confirmed experimentally.

This paper presents a novel versatile parallel gripper equipped with a sheet-embedded belt that enables passive pull-in operations. The belt is wrapped around each fingertip of the gripper, and it passively moves with the opening and closing motions of the gripper. The fingertip is made of plastic, and it is deflected when a grasping force is applied to the fingertip. This deflection enables the belt to roll up with the closing motion of the gripper, thereby passively pulling the grasped workpiece towards the gripper. This pull-in mechanism is effective in performing bin-picking tasks as well as in picking up thin, flexible objects one at a time. The softness of the sheet-embedded belt surface provides high adaptability to the shape of the object; therefore, many kinds of workpieces can be picked up. The effectiveness of the proposed gripper is experimentally demonstrated in this study.