非線形弾性要素による内部力補償に基づく無段階変位–力変換機構の創生 ― 微小操作力で強大な磁気力・把持力・制動力・張力を制御可能とするロボット要素 ―

Tohoku University博士（情報科学）thesi

Design and analysis of a variable-stiffness robotic gripper

This paper presents the design and analysis of a novel variable-stiffness robotic gripper, the RobInLab VS gripper. The purpose is to have a gripper that is strong and reliable as rigid grippers but adaptable as soft grippers. This is achieved by designing modular fingers that combine a jamming material core with an external structure, made with rigid and flexible materials. This allows the finger to softly adapt to object shapes when the capsule is not active, but becomes rigid when air suction is applied. A three-finger gripper prototype was built using this approach. Its validity and performance are evaluated using five experimental benchmark tests implemented exclusively to measure variable-stiffness grippers. To complete the analysis, our gripper is compared with an alternative gripper built by following a relevant state-of-the-art design. Our results suggest that our solution significantly outperforms previous approaches using similar variable stiffness designs, with a significantly higher grasping force, combining a good shape adaptability with a simpler and more robust design.This paper describes research conducted at UJI Robotic Intelligence Laboratory. Support for this laboratory is provided in part by Ministerio de Ciencia e Innnovación (DPI2015-69041-R and DPI2017-89910-R), by Universitat Jaume I (UJI-B2018-74), and by Generalitat Valenciana (PROMETEO/2020/034)

Design, sensing, and control of soft multi-axis fluidic actuators for robotic manipulation

The emergence of actuators with controllable compliance, such as soft fluidic actuators, has been indispensable for complex robotic manipulation and human-robot interaction research. In this work, we develop novel modular soft robotic pneumatic actuator arrays capable of carrying out complex motions and manipulation tasks. First, the design and manufacturing of a soft bi-directional pneumatic bellows actuator module, which can contract in vacuum and extend in positive pressure, is outlined. To sense motions and achieve closed loop control of orientation and actuator array length, inertial measurement units and custom soft wire potentiometers are used. Then, three bi-directional pneumatic bellows actuators are combined with sensors into modular arrays that can extend, contract, bend, and twist depending on the amount of pressure applied to each module. These arrays can be stacked in series to achieve even more complex motions and to complete unique manipulation tasks. To showcase the versatility of the soft robotic manipulator, several peripheral mechanisms are also developed including a particle jamming gripper that is used to grip and unscrew items, a center contraction module to promote buckling for twisting, and contraction-based foam plates for gripping. For this system, simulation environments, kinematic models, and multi-actuator multi-axis control strategies are developed. Demonstrations are shown to illustrate the manipulation capabilities of this system. Additionally, the use of magnetorheological fluid for soft hydraulic actuation is also explored. For these soft actuation mechanisms, the use of magnetorheological fluids, liquid metal coils, compliant magnetic composites, and silicone flexures are tested. Magnetic field models and fluid scaling laws are outlined. Finally, these actuators are used to demonstrate the operation of compliant bistable valves, soft multi-fingered PneuNets, and a new force-amplified magnetorheological fluid gripper.M.S

On the Use of Magnets to Robustify the Motion Control of Soft Hands

In this letter, we propose a physics-based framework to exploit magnets in robotic manipulation. More specifically, we suggest equipping soft and underactuated hands with magnetic elements, which can generate a magnetic actuation able to synergistically interact with tendon-driven and pneumatic actuations, engendering a complementarity that enriches the capabilities of the actuation system. Magnetic elements can act as additional Degrees of Actuation (DoAs), robustifying the motion control of the device and augmenting the hand manipulation capabilities. We investigate the interaction of a soft hand with itself for enriching possible hand shaping, and the interaction of the hand with the environment for enriching possible grasping capabilities. Physics laws and notions reported in the manuscript can be used as a guidance for DoAs augmentation and can provide tools for the design of novel soft hands

Development of a Novel Impedance-Controlled Quasi-Direct-Drive Robot Hand

Most robotic hands and grippers rely on actuators with large gearboxes and force sensors for controlling gripping force. However, this might not be ideal for tasks which require the robot to interact with an unstructured and/or unknown environment. We propose a novel quasi-direct-drive two-fingered robotic hand with variable impedance control in the joint space and Cartesian space. The hand has a total of four degrees of freedom, a backdrivable gear train, and four brushless direct current (BLDC) motors. Field-Oriented Control (FOC) with current sensing is used to control motor torques. Variable impedance control allows the hand to perform dexterous manipulation tasks while being safe during human-robot interaction. The quasi-direct-drive actuators enable the fingers to handle contact with the environment without the need for complicated tactile or force sensors. A majority 3D printed assembly makes this a low-cost research platform built with affordable off-the-shelf components. The hand demonstrates grasping with force-closure and form-closure, stable grasps in response to disturbances, tasks exploiting contact with the environment, simple in-hand manipulation, and a light touch for handling fragile objects.Comment: 75 pages, A Thesis in Partial Fulfillment of the Requirements for the Degree of Master of Science in Mechanical Engineering at Stony Brook Universit

Robotic Actuation and Control with Programmable, Field-Activated Material Systems

This dissertation presents novel, field-activated smart material systems for the actuation and control of autonomous robots. Smart materials, a type of material whose properties can be changed with an external stimuli, represent a promising direction to expand upon existing robotic control and actuation methods, particularly in the sub-fields of soft robotics and robotic grasping. Specifically, this work makes the following contributions: i) a literature review that synthesizes recent work on field-activated smart materials and their use in soft robotics; ii) an electrorheological fluid (ERF) valve to control soft actuators; iii) magnetic elastomers (MEs) to increase the grip strength of soft grippers; and iv) a low-power method for torque transmission enabled by magnetorheological fluid (MRF) and electropermanent magnet arrays. After the introduction, this dissertation presents a comprehensive literature review paper (Chapter 2) regarding the use of field-activated materials in soft robotics, with an emphasis on magnetic elastomers. The second paper (Chapter 3) describes the development of a 3D-printed pressure valve intended to leverage the pressuring-holding properties of ERF when under the influence of a high voltage field to actuate soft actuators. The third paper (Chapter 4) demonstrates how magnetic elastomers and magnetic fields can enhance soft robotic grip strength and versatility. The fourth paper (Chapter 5) models, fabricates, and characterizes a MRF-containing clutch device able to rapidly and reversibly module the amount of torque transmitted from an input shaft to an output by leveraging low-power electropermanent magnet arrays. Each work focuses on a field-activated smart material to perform a specific robotic function, with particular emphasis given to compliant mechanisms and soft robotics, as well as to reducing cost and improving ease of fabrication with the use of modern fabrication techniques. In these described papers, field-activated materials are first modeled and then deployed in functional prototypes, and their robotic utility is described in detail after extensive experimental characterization