Human-Inspired Representation of Object-Specific Grasps for Anthropomorphic Hands

In this study, a Crossed Flexural Hinge (CFH) structure was used for the design of a humanoid robot hand that can absorb any abrupt external force and that has a large payload, giving it the advantages of both rigid and compliant robots. Structural problems were identified through a 6 × 6 stiffness matrix to analyze whether CFH is suitable for use as an anthropomorphic robot hand. To reinforce the weak stiffness, a paired CFH (p-CFH) structure was proposed for the robot hand joints. In addition, it was verified through theoretical and experimental methods that p-CFH has superior stiffness characteristics compared to conventional CFH. When designing the anthropomorphic robot hand, p-CFH was appropriately deformed and applied. Using an underactuated wire mechanism suitable for the structure of the robot hand, it was possible to grasp objects of various shapes in a shape-adaptive manner. It was confirmed that the final anthropomorphic robot hand was able to stably hold an object of an unspecified shape without precisely controlling the motor. And the robot hand can also hold a heavy object due to the increased rigidity of the p-CFH. In addition, by conducting the qualitative impact test in which the robot was subjected to an impact in an arbitrary direction, it was confirmed that the robot, due to compliance of the joints, can absorb impact without incurring damage. Finally, a quantitative impact test was conducted in all directions, and the shock absorbing capability of anthropomorphic robot hand was verified through numerical comparison with the control model.

The paper presented here approaches to solve the complexity of an anthropomorphic robotic hand. Robotics is now the most advancing field and there has always been an intention of mimicking human-like actuation and behavior. An anthropomorphic hand is one of the approaches to imitate human-like operations. In this paper, the idea of developing an anthropomorphic hand with 15 degrees of freedom and 5 actuators has been elaborated as well as the mechanical design, control system, composition, and peculiarities of the robotic hand have been discussed. The hand has an anthropomorphic appearance and also can perform human-like functionalities, for example, gripping and hand gestures representation. The results reveal that the hand is designed as one part and does not need any kind of assembly and it exhibits an excellent weight lifting capacity, since it is made of flexible thermoplastic polyurethane (TPU) material, and its elasticity also ensures that the hand is safe for interacting with humans as well. This hand may be used in a humanoid robot as well as a prosthetic hand. The limited number of actuators makes the control simpler and the hand lighter.

The human palm is a remarkable and highly functional part of the hand that significantly contributes to dexterity, grasp versatility, and overall manipulation capability. The metacarpophalangeal joints (MCP) of the palm facilitate movement of the fingers for flexion, extension, abduction, adduction, and limited circumduction, which can be a challenge to replicate the same function in robotic hands by simple design. In this paper, we proposed a single actuated folding mechanism as the metacarpals and passive rotating MCP joints to perform abduction, adduction, and circumduction of the human hand. The proposed anthropomorphic hand called <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Folding Hand</b> which has a reconfigurable palm and five underactuated tendon-driven fingers. The design of the hand is compact and the price is low, with all six actuators and five sensors on the hand costing less than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\$}$</tex-math></inline-formula>180. Additionally, a methodology has been developed to comprehensively analyze the grasping capacity by combining the grasping quality and the grasping workspace. The experimental results show that the folding palm mechanism and the compliant rotating finger base can replicate human hand capabilities and performance precision and in-hand manipulation tasks.

Anthropomorphic robotic hands have been widely investigated to dexterously manipulate objects because of their anatomical similarity to the human hand. However, the large dimension of configuration space challenges the real-time performance of existing grasp planning methods and drastically limits the application of anthropomorphic hands. In this letter, we propose a fast force-closure grasp synthesis (FFCGS) method for the anthropomorphic hand to efficiently grasp unknown objects. The FFCGS is implemented by using a signed distance field (SDF) as input. Firstly, a network that samples feasible 6D wrist poses is trained in an end-to-end fashion to reduce the dimension of search space. Furthermore, a fast optimization algorithm is presented to find finger configurations for force-closure precision grasp based on the differentiable Q-distance metric. We validate our method in both a simulated and a real-world environment. Experiment results show that the proposed FFCGS achieves a significantly improved performance in terms of time efficiency (5 times faster), grasp quality metrics, and success rate (5%-10% improvement) over benchmark methods. The outcomes of this study have great significance in promoting the motion planning of robot hand-arm systems and upper-limb prostheses.

This paper introduces an anthropomorphic robot hand that has variable grasping stiffness to unknown objects without damage. The robot hand has four fingers, 13 DoFs (Degrees of Freedom) with three SEA (Series Elastic Actuator) modules in the index, middle, and ring finger. The performance for broader grasping stiffness using variable impedance control based on the parameter update block and the procedure of grasping capability evaluations of the robot hand are explained. The robot finger modules are constructed with a thumb, index, middle, and ring finger to complete the anthropomorphic type robot hand. The robot finger module has three DoFs and functions as one actuator based on an under-actuated mechanism. Additionally, external force measurement is possible in the fingertip force sensor and SEA (Series Elastic Actuator) module. For the variable impedance control implementation, a parameter update block is added to adjust the desired impedance parameter. To implement the parameter update block, we define and evaluate the correlation equation between the fingertip force, shore hardness, and damping ratio.

Postural synergies of the UB Hand IV for human-like grasping

The paper describes work in progress at the University of Bologna concerning the design of a new anthropomorphic robot hand. The hand is based on the modular assembly of articulated fingers that adopt an original configuration of their structure, made with rigid links connected by elastic hinges that are coaxially crossed by flexible tendons. This innovative design is suitable to host distributed sensory equipment and continuous compliant cover, allowing a high level of anthropomorphism together with great structural simplification, reliability enhancement and cost reduction. Furthermore, the proposed solution is very flexible, as it can be adapted to many different hand configurations and is not dependent on a particular type of actuation, being compatible with future availability of any kind of artificial muscles.

After introductory considerations on the main functional and design differences between anthropomorphic hands conceived as robotic end effectors or as prostheses, this chapter presents two topics related to advances in robotic hand design that seem transferable to prosthetic hands, in order to increase their functional capability yet coping with specific constraints like simplicity, lightweight, cost effectiveness, robustness, etc. The development of a bio-inspired robotic hand, called UB Hand IV, based on an endoskeletal articulated structure, actuated by tendons and covered by a soft dermal-epidermal layer is briefly illustrated, in order to show the potential of its design solutions to be transferred into prosthetic hands. The first part of the chapter presents alternative design approaches for articulated joints and finger structures based on purposely designed compliant hinges. The basic problem of compliant hinges adoption in robotic structures, that is the limitation of secondary compliance effects, is analyzed and considerations about comparative metrics are proposed. Two hinge morphologies which show promising features are critically compared and pros and cons the production of fully integral fingers with compliant joints are discussed. The second part reports on the development of thin soft covers for robotic (and prosthetic) hands capable of strictly mimicking the actual compliance of human finger pulps. A design method, called by the authors Differentiated Layer Design (DLD), is reviewed and its potential for application on both robotic and prosthetic devices is underlined. Conclusions summarize the main aspects that encourage the transfer of the described results from the world of robots to that of human portable devices.

Many people are expecting for robots to support home work. However, in order to actually do such work, it is necessary for the robot to acquire the complex functions of human hands. Therefore, we developed a humanoid type hand that can be used for humanoid robot and prosthetic hand, and verified various actions of daily life to prove its function. As a result, this robot hand could grab eggs and vegetables, pour water into the cup, grasp the plastic wrap and cover the dishes.

With demographic change driving the demand for robotic assistance in complex grasping tasks, robot hands are emerging as a promising solution. However, the growing interest in anthropomorphic robot hands is difficult to address: The complex and multifaceted mechanical design creates high entry hurdles for new designers. This slows the growth in the number of experts and complicates finding relevant information, even for experienced designers. This is particularly evident in the conceptual design phase, when determining joint configuration, their coordination, and relative allocation. Guidance in the form of a knowledge-based design assistance system could address these problems by automating the decision-making parts of the design process, presenting solutions with reference to literature and offering recommendations for the conceptual design. This dissertation addresses the question of how such a guidance can be developed. A hypotheses is formulated and three objectives are pursued to test it: (1) develop a literature-linked knowledge base on joint configuration and coordination of tendon-driven rigid-sequential anthropomorphic robot hands to systematically generate conceptual designs, (2) develop a method to identify optimal designs based on user requirements, and (3) develop an automated evaluation method to select the most suitable design from the generated options. For the first objective, a knowledge base is developed, organizing relevant information into a non-redundant list of 23 fields of interest and 30 principal solutions, each linked to its original references. Arranged in morphological boxes, the knowledge base is applied to a methodically derived joint configuration of the human hand to generate approximately 8.5 billion conceptual designs. For the second, a heuristic is developed to identify Pareto-optimal designs based on desired grasp types (performance) and a choice between dexterity and design simplicity (preference). Suitable joint configurations and coordination strategies, drawn from literature, are ranked according to the user’s preference. For the third, the developed control system evaluates designs using a utility analysis of the principal solutions, with scores adjusted by preference and relevance weights to align with the heuristic. The resulting guidance is implemented as a graphical user interface and verified to replicate the intended recommendations. An example application of the guidance presents, to the best of the author’s knowledge, the first task-based design of an anthropomorphic robot hand with references to original sources. By lowering entry barriers in early-stage anthropomorphic robot hand design, this dissertation lays a foundation for accelerating mechanical and control development, with potential to meet growing demand and reduce costs. It also presents the first framework for task-based robot hand design with meaningful results, despite gaps in the state of the art limiting a full analysis.

We have presented the newly developed anthropomorphic robot hand named the KH Hand type S and its master slave system using the bilateral controller. The use of an elastic body has improved the robot hand in terms of weight, the backlash of the transmission, and friction between the gears. We have demonstrated the expression of the Japanese finger alphabet. We have also shown an experiment of a peg-in-hole task controlled by the bilateral controller. These results indicate that the KH Hand type S has a higher potential than previous robot hands in performing not only hand shape display tasks but also in grasping and manipulating objects in a manner like that of the human hand. In our future work, we are planning to study dexterous grasping and manipulation by the robot.

In this paper a very lightweight artificial hand is presented that approximates the manipulation abilities of a human hand very well. A large variety of different objects can be grasped reliably and the movements of the hand appear to be very natural. This five finger hand has 13 independent degrees of freedom driven by a new type of powerful small size flexible fluidic actuator. The actuators are completely integrated in the fingers which made possible the design of a very compact and lightweight hand that can either be used as a prosthetic hand or as a humanoid robot hand. A mathematical model for the expansion of a flexible fluidic actuator is given and the mechanical construction and features of the new anthropomorphic hand are illustrated.

Dexterous anthropomorphic robotic hand has very important applications in service robot for cooperating with people in the daily living environment and using the tools specifically designed for people. In this paper, we designed a dexterous anthropomorphic robotic hand mimicking the muscle-tendon-ligament structure of the human hand. The robotic hand possesses the similar Degrees of Freedom (DOF) configuration of the human hand. Each DOF is driven with a pair of antagonistic pneumatic artificial muscles, and Bowden wires are carefully laid for mimicking the tendons of the human hand to facilitate the motion control of the robotic hand. Rubber bladders with force sensors are also employed as the skin of the palm and the finger pad to enable the force control and compliant manipulation of the robotic hand. As a result, the robotic hand can reproduce the manipulations of the human hand, and thus can be deployed on a robot to cooperate with people or on a homogeneous slave robot to improve its tele-operation performance.

Force and touch telepresence has an important effect on robot hand controlling. When controlling humanoid robotic hand has data glove, the movement of robot hand appeared to be rigid because of the lack of touch telepresence. The movement of humanoid robot hand would be more flexible if tactile equipment was installed on data glove. There are two important requirements in tactile equipment of data glove, that is to say the structure of equipment must be compact. Too much complexity would lower the reliability of data glove, on the other hand, and the equipment must simulate the touch telepresence as actual as possible, which would influence the realness of the operation directly. In order to balance the structure of the data glove and the realness of tactile simulation, a new system that could build tactile telepresence between robot hand and human hand has been designed and manufactured, including a data glove and a humanoid robot hand. The data glove has 12 attitude transducers on the back and 14 groups of silica gel electrodes to irritate human hand by electrical pulses and simulate the touch telepresence. The humanoid robot hand use cord to transmit the motion which has 13 servo to control the movement of each joint accurately and 14 accurate pressure sensor to assess the grab situation.

We describe the design of the multi-finger anthropomorphic robotic hand for small-scale industrial applications, called AISRA (Anthropomorphic Interface for Stimulus Robust Applications), which can feel and sense the object that it is holding. The robotic hand was printed using the 3D printer and includes the servo bed for finger movement. The data for object recognition was collected using Leap Motion controller, and Naive Bayes classifier was used for training and classification. We have trained the robotic hand on several monotonous objects used in daily life using supervised machine learning techniques and the gesture data obtained from the Leap Motion controller. The mean accuracy of object recognition achieved is 92.1%. The Naive Bayes algorithm is suitable for using with the robotic hand to predict the shape objects in its hands based on the angular position of its figures. Leap Motion controller provides accurate results and helps to create a dataset of object examples in various forms for the AISRA robotic hand, and can be used to help developing and training 3D-printed anthropomorphic robotic hands. The experiments in object grasping experiments demonstrated that the AISRA robotic hand can grasp objects with different size and shape, and verified the feasibility of robot hand design using low-cost 3D printing technology. The implementation can be used for small-scale industrial applications.