Compliant Hand Research Articles

Design of the Passive Joints of Underactuated Modular Soft Hands for Fingertip Trajectory Tracking

In this letter, we propose a method to design tendon-driven underactuated hands whose fingertips can track a predefined trajectory, when actuated. We focus on passively compliant hands composed of deformable joints and rigid links. We first introduce a procedure to determine suitable joints stiffness and tendon routing, then a possible realization of a robotic underactuated finger is shown. The kinematic and kinetostatic analysis of a tendon-driven robotic finger is necessary to define the overall stiffness values of the finger joints. A structural analysis of the element constituting each passive joint allowed to define a relation between the stiffness and joint's main dimensional and material properties. We validated the proposed framework both in simulation and with experiments using the robotic Soft-SixthFinger as a case study. The Soft-SixthFinger is a wearable robot for grasping compensation in patients with a paretic hand. We demonstrated that different fingertip trajectories can be achieved when joint stiffness and tendon routing are properly designed. Moreover, we demonstrated that the device is able to grasp a wider set of objects when a specific finger flexion trajectory is designed. The proposed framework is general and can be applied to robotic hands with an arbitrary number of fingers and joints per finger. The modular approach furthermore allows the user to easily customize the hand according to specific tasks or trajectories.

On Grasp Quality Measures: Grasp Robustness and Contact Force Distribution in Underactuated and Compliant Robotic Hands

The availability of grasp quality measures is fundamental for grasp planning and control, and also to drive designers in the definition and optimization of robotic hands. This work investigates on grasp robustness and quality indexes that can be applied to power grasps with underactuated and compliant hands. When dealing with such types of hands, there is the need of an evaluation method that takes into account the forces that can be actually controlled by the hand, depending on its actuation system. In this paper, we study the potential contact robustness and the potential grasp robustness (PCR, PGR) indexes. They both consider main grasp properties: contact points, friction coefficient, etc., but also hand degrees of freedom and consequently, the directions of controllable contact forces. The PCR comes directly from the classical grasp theory and can be easily evaluated, but often leads to too conservative solutions, particularly when the grasp has many contacts. The PGR is more complex and computationally heavier, but gives a more realistic, even if still conservative, estimation of the overall grasp robustness, also in power grasps. We evaluated the indexes for various simulated grasps, performed with underactuated and compliant hands, and we analyzed their variations with respect to the main grasp parameters.

A Low-Cost, Open-Source, Compliant Hand for Enabling Sensorimotor Control for People with Transradial Amputations.

In this paper, we describe the design and implementation of a low-cost, open-source prosthetic hand that enables both motor control and sensory feedback for people with transradial amputations. We integrate electromyographic pattern recognition for motor control along with contact reflexes and sensory substitution to provide feedback to the user. Compliant joints allow for robustness to impacts. The entire hand can be built for around $550. This low cost makes research and development of sensorimotor prosthetic hands more accessible to researchers worldwide, while also being affordable for people with amputations in developing nations. We evaluate the sensorimotor capabilites of our hand with a subject with a transradial amputation. We show that using contact reflexes and sensory substitution, when compared to standard myoelectric prostheses that lack these features, improves grasping of delicate objects like an eggshell and a cup of water both with and without visual feedback. Our hand is easily integrated into standard sockets, facilitating long-term testing of sensorimotor capabilities.

SynGrasp: A MATLAB Toolbox for Underactuated and Compliant Hands

SynGrasp is a MATLAB toolbox for grasp analysis of fully or underactuated robotic hands with compliance. Compliance can be modeled at contact points in the joints or in the actuation system, including transmission. It is possible to use a graphical user interface (GUI) or directly assemble and modify the available functions to exploit all of the toolbox features. Grasps can be described either using the provided grasp planner or by directly defining contact points on the hand with the respective contact normal directions. Several analysis functions have been developed to investigate the main grasp properties: 1) controllable forces and object displacement, 2) manipulability analysis, and 3) grasp stiffness and quality measures. The functions for the graphical representation of the hand and object as well as the main analysis results are provided. The toolbox is freely available at http://syngrasp.dii.unisi.it.

ツイストドライブに基づく柔軟なロボットハンド

ツイストドライブに基づく柔軟なロボットハンド

MULTIBAND SLOT ANTENNAS FOR METAL BACK COVER MOBILE HANDSETS

New multiband integrated slot antennas for mobile handsets are presented for GSM, DCS, PCS and WCDMA, GPS and WIFI 2.4 GHz. Prototypes, both simulated and measured, are realised in the metal back cover away from the hand. Perturbations due to tissue proximity are simulated using a CTIA compliant hand phantom.

Graft Vasculopathy in Clinical Hand Transplantation

Allogeneic hand transplantation is now a clinical reality. While results have been encouraging, acute rejection rates are higher than in their solid-organ counterparts. In contrast, chronic rejections, as defined by vasculopathy and/or fibrosis and atrophy of skin and other tissues, as well as antibody mediated rejection, have not been reported in a compliant hand transplant recipient. Monitoring vascularized composite allograft (VCA) hand recipients for rejection has routinely involved punch skin biopsies, vascular imaging and graft appearance. Our program, which has transplanted a total of 6 hand recipients, has experience which challenges these precepts. We present evidence that the vessels, both arteries and veins may also be a primary target of rejection in the hand. Two of our recipients developed severe intimal hyperplasia and vasculopathy early post-transplant. An analysis of events and our four other patients has shown that the standard techniques used for surveillance of rejection (i.e. punch skin biopsies, DSA and conventional vascular imaging studies) are inadequate for detecting the early stages of vasculopathy. In response, we have initiated studies using ultrasound biomicroscopy (UBM) to evaluate the vessel wall thickness. These findings suggest that vasculopathy should be a focus of frequent monitoring in VCA of the hand.

A proposal for benchmark tests for underactuated or compliant hands

Abstract. There is a lack of agreement in the literature as to what exactly quantifies the performance of underactuated hands. This paper proposes two benchmark tests to measure the ability of underactuated hands to grasp different objects and the ability to hold the objects when force disturbances apply. The first test determines the smallest and largest cylindrical object which can be successfully grasped in an enveloping grasp or in a pinch grasp. The second test provides the maximal allowable force which can be applied to a grasped object without loosing it. A setup was constructed consisting of standard components. Exemplary tests were applied to the Delft Hand 2. The proposed benchmark tests are representative to quantify the performance of pick and place operations with underactuated hands. The results of the tests can be applied to evaluate, compare, and improve the performance of robotic hands. This paper was presented at the IFToMM/ASME International Workshop on Underactuated Grasping (UG2010), 19 August 2010, Montréal, Canada.

Contact sensing and grasping performance of compliant hands

Limitations in modern sensing technologies result in large errors in sensed target object geometry and location in unstructured environments. As a result, positioning a robotic end-effector includes inherent error that will often lead to unsuccessful grasps. In previous work, we demonstrated that optimized configuration, compliance, viscosity, and adaptability in the mechanical structure of a robot hand facilitates reliable grasping in unstructured environments, even with purely feedforward control of the hand. In this paper we describe the addition of a simple contact sensor to the fingerpads of the SDM Hand (Shape Deposition Manufactured Hand), which, along with a basic control algorithm, significantly expands the grasp space of the hand and reduces contact forces during the acquisition phase of the grasp. The combination of the passive mechanics of the SDM Hand along with this basic sensor suite enables positioning errors of over 5 cm in any direction. In the context of mobile manipulation, the performance demonstrated here may reduce the need for much of the complex array of sensing currently utilized on mobile platforms, greatly increase reliability, and speed task execution, which can often be prohibitively slow.

MOC-PSSM CME Article: Metacarpal Fractures

After reading this article, the participant should be able to: 1. Identify the fracture patterns and types of metacarpal fractures. 2. Recognize when surgery is indicated for a given fracture. 3. Discuss the pathophysiology of Bennett's fractures and treatment. 4. List surgical treatment options and their relative advantages and disadvantages. 5. Be familiar with pediatric metacarpal injuries and when surgery is indicated. Metacarpal fractures are among the most common injuries seen in the emergency room and a staple for the hand surgeon. Knowledge of the types of fractures that occur and the appropriate treatment options is critical core knowledge for the hand surgeon. With the advent of superior implants and intraoperative fluoroscopy, powerful treatment options exist for metacarpal fractures and are at the disposal of the informed hand surgeon. Closed reduction and cast immobilization, Kirschner wires, lag screws, plate fixation, and other techniques are all available to the hand surgeon. Bone grafting in highly comminuted fractures also deserves consideration. The majority of metacarpal fractures can be treated closed and do well with compliant hand therapy. Those fractures requiring operative intervention likewise do well, provided that the appropriate technique is used for the situation. For example, long oblique shaft fractures are optimally treated with lag screws, whereas short oblique fractures do better with Kirschner wires or plate fixation. When the correct therapy is tailored to the injury, most metacarpal fractures can be treated with predictably good outcomes. Metacarpal fractures are common occurrences in the office of the hand surgeon. The different types of injury patterns must be recognized by the surgeon and appropriate treatment then executed to serve both the patient and hand surgeon optimally.

Planning and executing navigation among movable obstacles

This paper explores autonomous locomotion, reaching, grasping and manipulation for the domain of navigation among movable obstacles (NAMO). The robot perceives and constructs a model of an environment filled with various fixed and movable obstacles, and automatically plans a navigation strategy to reach a desired goal location. The planned strategy consists of a sequence of walking and compliant manipulation operations. It is executed by the robot with online feedback. We give an overview of our NAMO system, as well as provide details of the autonomous planning, online grasping and compliant hand positioning during dynamically stable walking. Finally, we present results of a successful implementation running on the humanoid robot HRP-2.

Classification of Motion Constraints by Explorative Manipulation by a Compliant Multi-Fingered Hand

We propose acquiring several properties of an unknown manipulated object, through without using arbitrary information. It consists of explorative manipulation and observation with sensors. By observing self-motion with the target object, it acquires time series sensor data embedded in the motion constraints of the manipulated object. We assume that manipulation features are expressed as a cooperative relation between the fingers and the relation is extractable as a correlation of the time series sensor data. High-order local autocorrelation widely used in image recognition provides the feature vector from data. In feature space, contrastive motion constraints construct the axis of variance. Principal component analysis (PCA) finds the axis mapping constraints. Clustering is used to make classes corresponding to constraints in PCA space. The classes correspond to symbolic representation for the robot. The efficacy of our proposal is demonstrated through simulation and experiments in a task involving opening a screw on lid of unknown size from a bottle.

A Light Weight Compliant Hand Mechanism With High Degrees of Freedom

This paper presents the design and prototyping of an inherently compliant lightweight hand mechanism. The hand mechanism itself has 15 degrees of freedom and five fingers. Although the degrees of freedom in each finger are coupled, reducing the number of independent degrees of freedom to 5, the 15 degrees of freedom of the hand could potentially be individually actuated. Each joint consists of a novel flexing mechanism that is based on the loading of a compression spring in the axial and transverse direction via a cable and conduit system. Currently, a bench top version of the prototype is being developed; the three joints of each finger are coupled together to simplify the control system. The current control scheme under investigation simulates a control scheme where myoelectric signals in the wrist flexor and extensor muscles are converted in to x and y coordinates on a control scheme chart. Static load-deformation analysis of finger segments is studied based on a 3-dimensional model without taking the stiffener into account, and the experiment validates the simulation.

Design and prototyping of an active hand prosthetic device

PurposeThis paper presents the design and prototyping of the Inherently cOmpliant light Weight Active (IOWA) hand, an active hand prosthetic device.Design/methodology/approachThis hand prosthetic device has five actuated fingers, each with three joints. Each joint is designed using a novel, flexible mechanism based on the loading of a compression spring in both transverse and axial directions, and using cable‐conduit systems. Rotational motion is transformed into tendon‐like behavior, which enables the location of the actuators far from the arm (e.g. on a belt around the waist).FindingsIt was shown that several numerical approaches for the study of a mechanical spring undergoing loading conditions in tension, bending moment, and shear can be obtained towards analysis of motion for control of each finder segment. It was also shown that these numerical models are accurate in comparison with experimental results.Originality/valueWhile the mechanical design of the hand and associated kinematics were presented, we draw an early conclusion (without actual clinical testing) that this type of low‐cost inherently compliant hand may have a significant impact for providing added capabilities to a disabled person. It was also shown from the prototype that adequate control over the mechanical linkages leading to each segment of each digit is possible.

Hand Washing Compliance among Retail Food Establishment Workers in Minnesota

Inadequate hand washing by food workers is an important contributing factor to foodborne disease outbreaks in retail food establishments (RFEs). We conducted a survey of RFEs to investigate the effect of hand washing training, availability of hand washing facilities, and the ability of the person in charge (PIC) to describe hand washing according to the Minnesota Food Code (food code) on workers' ability to demonstrate food code–compliant hand washing. Only 52% of the PICs could describe the hand washing procedure outlined in the food code, and only 48% of workers could demonstrate code-compliant hand washing. The most common problems observed were failure to wash for 20 s and failure to use a fingernail brush. There was a strong positive association between the PIC being a certified food manager and being able to describe the food code hand washing procedure (odds ratio [OR], 5.5; 95% confidence interval [CI], 2.2 to 13.7), and there was an even stronger association between the PIC being able to describe hand washing and workers being able to demonstrate code-compliant hand washing (OR, 15; 95% CI, 6 to 37). Significant associations were detected among correct hand washing demonstration, physical infrastructure for hand washing, and the hand washing training methods used by the establishment. However, the principal determinant of successful hand washing demonstration was the PIC's ability to describe proper hand washing procedure. These results suggest that improving hand washing practices among food workers will require interventions that address PIC knowledge of hand washing requirement and procedure and the development and implementation of effective hand washing training methods.

Low-impact wheelchair propulsion: Achievable and acceptable

Incidence of upper-limb overuse injuries among the manual wheelchair population has been found to be associated with hand-rim loading characteristics such as impact and peak loading on the hand rim during propulsion. One proposed method to reduce impact and peak loading is the use of a compliant hand rim, one that can displace relative to the wheel when impacted by the hand. A Variable Compliance Hand-Rim Prototype (VCHP) was designed and used to experimentally optimize the level of compliance through subjective and qualitative propulsion outcome measures. Seventeen manual wheelchair users participated in the study. Subjects propelled their wheelchairs using the VCHP set to each of three compliance levels through a maneuverability test course, as well as on a range of grade conditions using a wheelchair treadmill. Biomechanical measures such as peak hand-rim force, rate of loading at impact, and metabolic demand were assessed during treadmill propulsion bouts. No adverse biomechanical side effects to compliance were found. As compliance was increased, user acceptance decreased. All the subjects found the lowest level of compliance (C1) to be acceptable. Use of the C1 hand rim significantly reduced the peak rate of rise in the hand-rim force on the 6% and 8% grades and significantly reduced the average rate of loading for the 2%, 4%, and 6% grades. This study showed that low-impact wheelchair propulsion is both achievable and acceptable to users.

An Analytical Approach to the Design of Compliant Hand for Assembly Operations.

An analytical method to the design of compliant hand appropriate to given assembly operations is presented. Use of passive compliance devices in mating operations is effective in order to prevent excessive contact forces and to guide an assembled part to its goal location despite of positioning errors among the parts. Methods to design passive compliance devices are thus required. First, quasistatic equilibrium conditions are established based on the kinematic and the static analysis of mechanical contacts. Second, feasible candidates for the desired end-point compliance are calculated based on the equilibrium conditions. Next, the configurations and the spring constants of virtual springs consisting of the desired compliant hand are designed through decomposing stiffness matrices. Simulation of mating operations is then introduced in order to determine the magnitude of spring constants of virtual springs and to verify whether the derived compliant hand enables the mating operations successful or not. Finally, one numerical example is shown to illustrate the process of the design of compliant hands.

Mating of Rigid Parts by a Manipulator With Its Own Compliance

In most assembly tasks involving mating of parts, industrial robots are not equipped with special compliant devices such as a remote center compliant hand. It is useful to know how the mating force and part movement are affected by assembly compliance, which depends upon robot configuration, and by other assembly parameters such as initial position errors, clearance between mating parts, etc. Such knowledge is helpful to the design of the layout of an assembly cell, specification of robot accuracy, specification of manufacturing tolerance, and so on. This paper derives the mating force and part movement in the mating of rigid cylindrical parts by an industrial manipulator with its own compliance, using a planar peg-in-hole insertion model. The derived mathematical relations are experimentally verified by performing insertion tests with a SCARA-type robot.

A compliant hand robot

The compliant hand robot was developed for metal stamping press feeding at Fisher and Paykel Ltd., home appliance manufacturer, New Zealand.