Metamorphic Hand Research Articles

Minimum Friction Coefficient-Based Precision Manipulation Workspace Analysis of the Three-Fingered Metamorphic Hand

Abstract Reconfigurable robotic hands can constitute one of the future trends of dexterous manipulator design, as they can strike a balance between precision, force exertion, flexibility, and adaptability. However, the feasible manipulation workspace of a reconfigurable robotic hand, the metamorphic hand, is complex as the finger operation planes alter with the reconfigurable palm’s motions. Different useful workspace approaches and grasp quality metrics have been introduced, but a precision manipulation workspace (PMW) approach for reconfigurable robotic hands has yet to be presented. This paper presents a hand workspace taxonomy based on previous studies, and a new approach to obtaining a PMW of a robotic hand which satisfies three properties: force closure, singularity avoidance, and interference avoidance. A grasp quality metric, termed the minimum friction coefficient (MFC), is introduced to indicate the force-closure conditions of a robotic hand’s configurations. Unlike the previous grasp quality metrics targeting online grasp-planning tasks, this MFC-based measure focuses on the offline design of robotic hands. This method is essential for conducting grasp planning, design optimization, and actuation reduction for reconfigurable robotic hands. Further, the approach is applied to a three-fingered metamorphic hand, and the results are studied thoroughly.

Design, Analysis, and Experiment of a Scissor-Shaped Deployable Metamorphic Hand

Abstract It is necessary to innovatively design the dexterity and applicability of end-effector to solve the last centimeter problem of automated production. This paper presents a scissor-shaped deployable metamorphic hand (SDMH). First, a scissor-shaped sub-mechanism module mechanism was designed with three metamorphic configurations. A novel connection mechanism was introduced. It can realize the passively adaptive grasping motion and avoid the bifurcation position problem in the clamping process. Subsequently, the three configurations of SDMH were analyzed by the sub-constraint function. Then, the conversion relationship between the various configurations was established through the adjacency matrix, which fundamentally explains the metamorphic mechanism of SDMH. Furthermore, the kinematics analysis of the SDMH was described by the D–H method. Kinematic equations of the single finger can be established in the different three grasping configurations using the matrix transformation method. The working space of SDMH can be obtained by numerical simulation. Finally, the physical prototype of SDMH was manufactured to verify the deployable and grasping performance of SDMH.

Geometric Design-based Dimensional Synthesis of a Novel Metamorphic Multi-fingered Hand with Maximal Workspace

Current research on robotic dexterous hands mainly focuses on designing new finger and palm structures, as well as developing smarter control algorithms. Although the dimensional synthesis of dexterous hands with traditional rigid palms has been carried out, research on the dimensional synthesis of dexterous hands with metamorphic palms remains insufficient. This study investigated the dimensional synthesis of a palm of a novel metamorphic multi-fingered hand, and explored the geometric design for maximizing the precision manipulation workspace. Different indexes were used to value the workspace of the metamorphic hand, and the best proportions between the five links of the palm to obtain the optimal workspace of the metamorphic hand were explored. Based on the fixed total length of the palm member, four nondimensional design parameters that determine the size of the palm were introduced; through the discretization method, the influence of the four design parameters on the workspace of the metamorphic hand with full-actuated fingers and under-actuated fingers was analyzed. Based on the analysis of the metamorphic multi-fingered hand, the symmetrical structure of the palm was designed, resulting in the largest workspace of the multi-fingered hand, and proved that the metamorphic palm has a massive upgrade for the workspace of underactuated fingers. This research contributed to the dimensional synthesis of metamorphic dexterous hands, with practical significance for the design and optimization of novel metamorphic hands.

Innovative design method of the metamorphic hand

In order to solve the last centimeter problem of automated production, it is necessary to innovative design of flexible fixture. This article presents a metamorphic hand design method through the principle of metamorphic mechanism. Firstly, kinematic chain satisfying the requirements is obtained by number synthesis and structural synthesis. Then, the kinematic chain becomes a mechanism that meets the requirements using regeneration design rules. And the holographic matrix description method is used to describe the configuration transformation of the metamorphic mechanism. Furthermore, through the combination method of kinematic chain, the metamorphic clamp increases the two joint fingers into a metamorphic hand. Finally, the validity of the theoretical method is verified by physical experiments.

Fuzzy Model Based Stability Analysis of the Metamorphic Robotic Palm

The metamorphic hand can flexibly relocate fingers by a reconfigurable palm. A precondition for the successful hand operation would be a stable palm control system. Following this concern, this paper presents the stability analysis of the reconfigurable palm control system based on the Takagi-Sugeno (T-S) fuzzy model. The dynamic model of the metamorphic palm is developed by using the Euler Lagrangian theory and the closed-chain kinematic constraints. To further reduce the conservativeness in stability analysis and ensure a wider range of stable dynamic performance, a membership-dependent fuzzy modeling approach is also applied. Simulation is provided to demonstrate the achieved improvement of analysis results.

Inverse kinematics and workspace analysis of the metamorphic hand

This paper investigates for the first time inverse kinematics of a four-fingered metamorphic hand. Compared with the current existing robotic hands, the most significant feature of the metamorphic hand is the introduction of a foldable and reconfigurable palm and its function of metamorphism, which greatly improves the ability of posture adjustment and inter-coordination between fingers. Geometric constraints of the palm are analyzed by using geometric method and constraint equation method, on the basis of which, kinematics of the metamorphic hand are transformed from a hybrid mechanism into serial mechanisms and forward kinematics can be obtained directly. To avoid the complexity of inverse kinematics of the thumb, a method taking advantage of geometric constraints of the palm is introduced to simplify the inverse kinematics of the metamorphic hand and analytical solutions are obtained in a concise form. The workspace of the metamorphic hand is decomposed into palm workspace and finger workspace. A triangle determined by the mounting points is introduced to measure the palm workspace and the simulation of the finger workspace augmented by the palm reveals that the reconfigurable palm contributes tremendously to the flexibility and versatility of the metamorphic hand.

KINEMATIC ANALYSIS AND PROTOTYPE OF A METAMORPHIC ANTHROPOMORPHIC HAND WITH A RECONFIGURABLE PALM

A novel metamorphic anthropomorphic hand is for the first time introduced in this paper. This robotic hand has a reconfigurable palm that generates changeable topology and augments dexterity and versatility of the hand. Structure design of the robotic hand is presented and based on mechanism decomposition kinematics of the metamorphic anthropomorphic hand is characterized with closed-form solutions leading to the workspace investigation of the robotic hand. With characteristic matrix equation, twisting motion of the metamorphic robotic hand is investigated to reveal both dexterity and manipulability of the metamorphic hand. Through a prototype, grasping and prehension of the robotic hand are tested to illustrate characteristics of the new metamorphic anthropomorphic hand.

Structural Synthesis of Compliant Metamorphic Mechanisms Based on Adjacency Matrix Operations

A compliant metamorphic mechanism attributes to a new type of metamorphic mechanisms evolved from rigid metamorphic mechanisms. The structural characteristics and representations of a compliant metamorphic mechanism are different from its rigid counterparts, so does the structural synthesis method. In order to carry out its structural synthesis, a constraint graph representation for topological structure of compliant metamorphic mechanisms is introduced, which can not only represent the structure of a compliant metamorphic mechanism, but also describe the characteristics of its links and kinematic pairs. An adjacency matrix representation of the link relationships in a compliant metamorphic mechanism is presented according to the constraint graph. Then, a method for structural synthesis of compliant metamorphic mechanisms is proposed based on the adjacency matrix operations. The operation rules and the operation procedures of adjacency matrices are described through synthesis of the initial configurations composed of s+1 links from an s-link mechanism (the final configuration). The method is demonstrated by synthesizing all the possible four-link compliant metamorphic mechanisms that can transform into a three-link mechanism through combining two of its links. Sixty-five adjacency matrices are obtained in the synthesis, each of which corresponds to a compliant metamorphic mechanism having four links. Therefore, the effectiveness of the method is validated by a specific compliant metamorphic mechanism corresponding to one of the sixty-five adjacency matrices. The structural synthesis method is put into practice as a fully compliant metamorphic hand is presented based on the synthesis results. The synthesis method has the advantages of simple operation rules, clear geometric meanings, ease of programming with matrix operation, and provides an effective method for structural synthesis of compliant metamorphic mechanisms and can be used in the design of new compliant metamorphic mechanisms.

D-13 A Metamorphic Instrumental Hand for Robot Assisted Minimally Invasive Surgery

It is expected to enhance manipulation in robot-assisted MIS. Inspired from metamorphic mechanism theory, structure of the instrumental hand is designed to be variable. It can pass patient's abdomen skin in a straight cylinder shape through an incision of 24 mm in diameter. A three-fingered hand shape surgical device is rebuilt from this straight cylinder inside abdomen. The metamorphic instrumental hand is controlled with an isomorphic master glove. Master-slave mapping method is analyzed in system setup. Mapping errors are measured and compensated for the instrumental hand control. Eight preliminary manipulation experiments have been carried out on phantom tissue to validate mUlti-manipulati on concept of this metamorphic instrumental hand.