Modelling and Simulation of a Manipulator with Stable Viscoelastic Grasping Incorporating Friction

Design, dynamics and control of a humanoid robotic hand based on anthropological dimensions, with joint friction, is modelled, simulated and analysed in this paper by using computer aided design and multibody dynamic simulation. Combined joint friction model is incorporated in the joints. Experimental values of coefficient of friction of grease lubricated sliding contacts representative of manipulator joints are presented. Human fingers deform to the shape of the grasped object (enveloping grasp) at the area of interaction. A mass-spring-damper model of the grasp is developed. The interaction of the viscoelastic gripper of the arm with objects is analysed by using Bond Graph modelling method. Simulations were conducted for several material parameters. These results of the simulation are then used to develop a prototype of the proposed gripper. Bond graph model is experimentally validated by using the prototype. The gripper is used to successfully transport soft and fragile objects. This paper provides information on optimisation of friction and its inclusion in both dynamic modelling and simulation to enhance mechanical efficiency

Two-fingered Hand with Gear-type Synchronization Mechanism with Magnet for Improved Small and Offset Objects Grasping: F2 Hand

A problem that plagues robotic grasping is the misalignment of the object and gripper due to difficulties in precise localization, actuation, etc. Under-actuated robotic hands with compliant mechanisms are used to adapt and compensate for these inaccuracies. However, these mechanisms come at the cost of controllability and coordination. For instance, adaptive functions that let the fingers of a two-fingered gripper adapt independently may affect the coordination necessary for grasping small objects. In this work, we develop a two-fingered robotic hand capable of grasping objects that are offset from the gripper's center, while still having the requisite coordination for grasping small objects via a novel gear-type synchronization mechanism with a magnet. This gear synchronization mechanism allows the adaptive finger's tips to be aligned enabling it to grasp objects as small as toothpicks and washers. The magnetic component allows this coordination to automatically turn off when needed, allowing for the grasping of objects that are offset/misaligned from the gripper. This equips the hand with the capability of grasping light, fragile objects (strawberries, creampuffs, etc) to heavy frying pan lids, all while maintaining their position and posture which is vital in numerous applications that require precise positioning or careful manipulation.Comment: 8 pages. Accepted at IEEE IROS 2023. An accompanying video is available at https://www.youtube.com/watch?v=RAO7Qb2ZGN

A Grasping-centered Analysis for Cloth Manipulation

Compliant and soft hands have gained a lot of attention in the past decade because of their ability to adapt to the shape of the objects, increasing their effectiveness for grasping. However, when it comes to grasping highly flexible objects such as textiles, we face the dual problem: it is the object that will adapt to the shape of the hand or gripper. In this context, the classic grasp analysis or grasping taxonomies are not suitable for describing textile objects grasps. This work proposes a novel definition of textile object grasps that abstracts from the robotic embodiment or hand shape and recovers concepts from the early neuroscience literature on hand prehension skills. This framework enables us to identify what grasps have been used in literature until now to perform robotic cloth manipulation, and allows for a precise definition of all the tasks that have been tackled in terms of manipulation primitives based on regrasps. In addition, we also review what grippers have been used. Our analysis shows how the vast majority of cloth manipulations have relied only on one type of grasp, and at the same time we identify several tasks that need more variety of grasp types to be executed successfully. Our framework is generic, provides a classification of cloth manipulation primitives and can inspire gripper design and benchmark construction for cloth manipulation.Comment: 13 pages, 4 figures, 4 tables. Accepted for publication at IEEE Transactions on Robotic

Design and control of a robotic thumb using piezoelectric actuators

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.Cataloged from PDF version of thesis.Includes bibliographical references (p. 38).Although much more complex and maneuverable than their predecessors, today's anthropomorphic robotic hands still cannot match the dexterity of human hands. While most of these limitations are caused by inadequate sensor and control systems, the use of large, heavy, and stiff actuators can also contribute to dexterity problems. If we expect robotic hands to interact with humans and human objects, joint actuators must allow a compromise of strength and compliance. Piezoelectric (PZT) actuators exhibit a high back driveability which could facilitate this compromise. Although they have low displacement and force output, they are useful in fine control applications. When combined with a DC motor, PZT actuators can produce precise, delicate movements in robotic hands. To develop the novel DC-PZT hybrid system, the force and displacement capabilities of PZT actuators were first characterized with a simple one degree of freedom system. The data from this characterization was analyzed and used to develop a one degree of freedom thumb using a hybrid DC motor/PZT actuator system. To study system performance, a simple position control scheme was implemented for the DC motor and PZT actuators. The experimental results suggest that current PZT actuators, even when combined with a DC motor, cannot produce enough thumb tip force to mirror the functionality of the human hand. That said, improvements to the actuator could make PZT-actuated hands a future possibility.by Jacob A. Levinson.S.B

Pengembangan Desain, Simulasi Dan Pengujian Robot Tangan Menggunakan Flex Sensor Terintegrasi Dengan 3d Animation Simmechanics

Teknologi robotika merupakan salah satu teknologi yang penting dalam menentukan kemajuan peradaban di dunia. Teknologi robotika dapat meningkatkan produktivitas suatu pekerjaan. Dengan adanya robotika, pekerjaan yang sebelumnya sulit dan berbahaya untuk dikerjakan sekarang sudah dapat dikerjakan lebih mudah dan aman Dengan input dari sinyal flex sensor dapat menggerakkan tangan robot dan dengan 3D Animation SimMechanics operator dapat memantau apakah input masukan dari flex sensor tepat menggerakkan tangan robot tersebut. Selain kedua hal tersebut pada artikel ini juga akan membahas mengenai pengujian sudut motor servo saat digerakkan dibandingkan dengan sudut tiap join tangan robot yang menghadirkan tabel sudut pergerakan antara servo motor dan tiap join tangan robotnya. Dari pengujian tersebut dapat dilihat ksimpulan hubungan antara gerakan servo motor dengan tali elastis yang digunakan untuk menghasilkan gerakan Balik setelah tangan robot ditarik oleh aktuator. Untuk kinematik tangan robot, artikel ini akan membahas pemosisian inisial tangan robot dan forward kinematics pada tangan robot dengan menggunakan metode Denavit-Hartenberg. Invers kinematics juga akan menjadi bahasan dalam tugas akhir ini. Software yang digunakan pada penelitian ini adalah MATLAB SimMechanics sebagai media kontrol dari virtual reality dan juga digunakan SolidWorks sebagai media desain awal tangan robot Telah berhasil diintegrasikan kontrol dari input sinyal flex sensor dan pergerakan tangan robot serta 3D Animation SimMechanics. Pada perhitungan forward kinematics menghasilkan koordinat posisi tiap ujung jari tangan robot dengan input sudut theta yang disesuaikan dengan sudut gerakan pada tangan manusia sesungguhnya. Lalu untuk inverse kinematics menghasilkan sudut dari tiap jari tangan setelah diberikan koordinat posisi dari ujung jari tangan robotny