Gripping Of Objects Research Articles

Tactile Sensing and Grasping Through Thin‐Shell Buckling

Soft and lightweight grippers have greatly enhanced the performance of robotic manipulators in handling complex objects with varying shape, texture, and stiffness. However, the combination of universal grasping with passive sensing capabilities still presents challenges. To overcome this limitation, a fluidic soft gripper is introduced based on the buckling of soft, thin hemispherical shells. Leveraging a single fluidic pressure input, the soft gripper can grasp slippery and delicate objects while passively providing information on this physical interaction. Guided by analytical, numerical, and experimental tools, the novel grasping principle of this mechanics‐based soft gripper is explored. First, the buckling behavior of a free hemisphere is characterized as a function of its geometric parameters. Inspired by the free hemisphere's two‐lobe mode shape ideal for grasping purposes, it is demonstrated that the gripper can perform dexterous manipulation and gentle gripping of fragile objects in confined spaces and underwater environments. Last, the soft gripper's embedded capability of detecting contact, grasping, and release conditions during the interaction with an unknown object is proved. This simple buckling‐based soft gripper opens new avenues for the design of adaptive gripper morphologies with tactile sensing capabilities for applications ranging from medical and agricultural robotics to space and underwater exploration.

Design and testing of mechanical gripping tools for On Orbit assembling

On-orbit servicing, assembly and manufacturing (OSAM) opens a new frontier for robotic systems. A gripping tool for such applications must meet several requirements of space mechanics, such as safety, precision and reliability, while functioning in space conditions. This paper presents a development cycle of such tools designed for the assembly of a small satellite antenna on the International Space Station. Two different grippers, driven by a common drive unit, are presented, conforming to a Multi-Purpose-Tool (MPT) for orbital robotic systems and meeting the requirements of a defined OSAM mission. Both design drivers and concepts and specific component selection are described. Proposed mechanical solutions for safe gripping of objects including space tribology aspects are covered. To adapted to operations not foreseen, the grippers and the drive unit can be reconfigured. The tool architecture presented promotes modularity, scalability, reusability and convertibility of designs, thus facilitating rapid integration in similar missions. A test campaign for critical requirements will be in place to ensure reliable performance of the tools for use in the space environment.

Development of a suction gripper network based on the biological role model of an octopus

The handling of fragile, sensitive or flexible components in assembly technology and production requires grippers that are designed for gentle handling of the objects to be gripped. Suction grippers are still a widespread standard solution for this purpose. However, rising energy prices are making pneumatic grippers, which work with a central upstream compressed air supply, increasingly unattractive. The generation of the compressed air itself, the mostly leaky transmission and the relatively inefficient vacuum generation are cost drivers that many users would like to avoid. Consequently, vacuum-based gripper means are required for industrial production, which work without externally generated compressed air. At the Fraunhofer IWU, a compressed-air-free suction pad composite has been developed that enables gripping of components with a wide variety of shapes. The underlying concept is inspired by the function of the suction arms (tentacles) of an octopus. By evacuating several small volume areas, which can be individually mechanically actuated, safe and sensitive gripping of objects is possible. For the generation of the vacuum, a piston system and a principle of an artificial muscle were developed, which is controlled based on shape memory alloys.

Dual-vat photopolymerization 3D printing of vitrimers

Herein, the processing of multi-material vitrimers with heterogenous properties along their x-,y- and z-axis is demonstrated using dual-vat digital light processing (DLP) 3D printing. The printer is based on a conventional vat exchange set-up containing two vats and a cleaning station, which are positioned on a linearly moving platform, and are exchanged automatically during the layer-by-layer build-up of the object. Two thiol-acrylate resins are selected bearing ample -OH and ester moieties, which undergo thermo-activated transesterification in the presence of an organic phosphate as catalyst. Based on the functionality of the acrylate monomers, printing of multi-material structures with flexible (σ = 1.1 MPa, ε = 14.0%) and rigid (σ = 33.3 MPa, ε = 4.4%) domains is feasible. A good interlayer adhesion between the soft and hard domains is evidenced by uniaxial tensile tests, whilst optical microscopy is used to study the interface. Dynamic mechanical analysis further shows that the stiffness of the photopolymers varies over several orders of magnitude (E’23 °C = 209 kPa - 507 MPa). Jacobs working curves of the two different resins reveal comparable printing parameters at higher exposure doses, which do not only facilitate the printing of multiple materials between individual layers (z-heterogeneity) but also within the same layer (x,y-heterogeneity). This is confirmed by the printing of a multi-material gripper as “proof of concept” demonstrator, which contains soft inner teeth and a stiff outer core. Gripping and releasing of objects is shown by exploiting the glass transition-based shape memory properties of the stiff domains. Moreover, due to the dynamic nature of the covalent bonds, damages inserted into the gripper are intrinsically repairable due to a thermo-activated macroscopic reflow. Shape memory experiments further confirmed that the multi-material gripper fully regains its function after the thermal mending process. Thus, the results clearly show that objects with a high degree of functionality can be realized by combining multi-material 3D printing with the chemistry of vitrimers. This is of particular interest for future soft robotic applications and for mimicking biological composite structures.

The effect of type 2 diabetes and diabetic peripheral neuropathy on predictive grip force control.

This study investigated the impact of type 2 diabetes and diabetic peripheral neuropathy on grip force control during object manipulation. The study included three age-matched groups: type 2 diabetes alone (n = 11), type 2 diabetes with neuropathy (n = 13), and healthy controls (n = 12). Grip force control variables derived from lifting and holding an experimental cup were the ratio between grip force and load forces during lifting (GFR), latency 1 and latency 2, which represented the time between the object's grip and its lift-off from the table, and the period between object's lift-off and the grip force peak, respectively; time lag, which denoted the time difference between the grip and load force peaks during the lifting phase, and finally static force, which was the grip force average during the holding phase. Grip force control variables were compared between groups using one-way ANOVA and Kruskal-Wallis test. Post-hoc analysis was used to compare differences between groups. GFR and latency 1 showed significant differences between groups; the type 2 diabetes with neuropathy group showed larger GFR than the type 2 diabetes alone and healthy control groups. The latency 1was longer for the group with neuropathy in comparison with the health control group. There were no significant differences between groups for latency 2, time lag, and static force. Our results showed impaired GFR and latency 1 in participants with type 2 diabetes with neuropathy while the time lag was preserved. People with type 2 diabetes alone might not have any deficits in grip force control. Higher grip forces might expose people with type 2 diabetes and diabetic peripheral neuropathy to the risk of fatigue and injuring their hands. Future studies should investigate strategies to help people with type 2 diabetes with neuropathy adjust grip forces during object manipulation.

Origami Chomper‐Based Flexible Gripper with Superior Gripping Performances

Flexible grippers with superior gripping capabilities are essential for carrying objects. Herein, an origami chomper‐based flexible gripper is designed using a combination of the origami technique and a newly developed nonlinear topology optimization method. This novel origami chomper‐based flexible gripper exhibits superior gripping performance, as revealed by a series of experiments, including gripping range capability under an identical input load, maximum gripping ratio, gripping adaptability, and achieving richer gripping characteristics by size scaling. The origami chomper‐based flexible gripper can handle a wide range of object irregularities in textures and uneven shapes and can enable effective gripping of objects across scales from millimeters to centimeters to decimeters through size scaling. This study paves the way for innovative high‐performance designs of flexible grippers.

High-performance triboelectric nanogenerators based on TPU/mica nanofiber with enhanced tribo-positivity

As a promising energy harvesting technology, triboelectric nanogenerator (TENG) has brought a leap forward to the development of self-powered systems. Many materials, especially inorganic non-metallic materials, proved to possess excellent triboelectric property, have rarely been practically used due to their fragility and rigidity. Here, fragile and rigid mica with strong triboelectric positivity is exfoliated into 2D nanosheets and electrospun into flexible and stretchable thermoplastic polyurethane (TPU) nanofibers for high-performance TENGs. Paired with polyvinylidene fluoride/MXene (PVDF/MXene) nanofibers, the transferred charge of the TENG with TPU/mica nanofibers significantly enhanced to 82.4 nC from 38.6 nC due to the enhanced tribo-positivity. Kelvin probe force microscopy (KPFM) measurements of single pure TPU and TPU/mica nanofibers showed mica apparently enhanced the positive electrostatic surface potential (ESP) of TPU. The mean peak ESP of pure TPU nanofiber was about 194 mV, while it was increased to 218 mV on the regions of TPU/mica nanofiber without mica nanosheets aggregation and 305 mV on the regions where mica nanosheets aggregated. The power density of the TENG with TPU/mica nanofiber reached 1458 mW/m2, exhibiting a 16-fold enhancement compared with the one based on pure TPU nanofiber. A thin and flexible TENG was fabricated and conformally worn on a wrist and palm for body motion monition and object gripping sorting. This work proposed high-performance triboelectric nanogenerators based on TPU/mica nanofibers and a general approach to effectively utilize rigid and fragile materials with excellent triboelectric property for making triboelectric layers.

Design of a Liquid Jamming Gripper

We present the design of a universal gripper based on the principle of liquid jamming. The phase change behavior of a mineral oil subjected to cooling is used for adaptive gripping and release of objects. The mineral oil is enclosed in a soft, compliant membrane molded into a spherical shape. The membrane with the liquid easily adapts to the shape of the object to be picked up. A thermoelectric cooling system is designed with a conductive spreader immersed in the oil to quickly cool the liquid held in a membrane. Once the membrane gripper conforms to the shape of the object partially enclosing it, the liquid is cooled below the phase change temperature, thus freezing the liquid and hardening the gripper around the object and effectively gripping it. We describe the design methodology of the gripper, part selection, and mechanical design. A proprietary controller developed by Venture Corporation is used for controlling the TEC module and the controller is based on a simple PID optimized using Ziegler–Nichols tuning for the P, I, and D values. The hardware is evaluated and the basic gripping functions on different odd-shaped objects are demonstrated. An invention disclosure has been submitted to the NUS IP office (ILO).

A Switched Adaptive Controller for Robotic Gripping of Novel Objects With Minimal Force

We present the design and implementation of an algorithm, equipped with a switched adaptive controller, for grasping unknown objects using a robot gripper. A Lyapunov-based analysis demonstrates that the switching controller is indeed asymptotically stable with both the translational and rotational slip velocities converging to the origin. Experimental results using a novel sensorized gripper prototype and objects of different sizes, shapes, and weights show that the proposed algorithm not only ensures the prevention of slippage of the grasped objects, but is also able to apply the minimal force needed to safely grasp these objects without causing excessive deformation.

Gripping adhesive principles in the design of effectors

This article presents a basic study of knowledge in the research and development of specific gripping elements based on the principle of adhesion. It summarizes the use of materials with a high degree of surface adhesion in the design of gripping elements usable in industry to provide stable gripping of objects during automatic manipulation. The principle of a combined element proposed by the authors, where the gripping force is derived through both vacuum and adhesion, is presented. The conditions of operation in an active or completely passive mode without the need to connect an energy source are discussed in detail. In the active mode, a significant increase in gripping forces is demonstrated compared to standard vacuum elements, which has a positive effect on the amounts of compressed air consumed and the level of grip safety in production processes. To ensure the optimal function of the adhesive gripping elements, the design of a specifically designed fluid position compensator and an active system for disturbing the adhesive gripping forces is presented. The functionality of the designed element is demonstrated through several laboratory tests under various conditions, and the results clearly confirm an increase in gripping forces in the axial and in particular the radial direction of the load. The research includes the design of a computer model of deformation-adhesive contact, respecting the time dependence of the deformation of the adhesive layer and the gradual loss of contact with the object.Article highlights:Experimental study presents use of PU materials in adhesive and combined gripping elements.Adhesive contact theory is applied for a numerical simulation and prepared computer model is subsequently verified.Authors present new proprietary solution of gripping element applicable in industrial robotics.

Sensor evaluation for hand grip strength

<p>This paper discusses the evaluation of the sensors used in the hand grip strength glove. The glove comprises of flex and force resisting sensors. Force resisting sensor determines the force applied by various parts of the palm, while the flex sensor determines the flexion of the fingers. These sensors are placed in a specific position on the glove to obtain correct data when the glove is used. The glove has two modes, which are pencil grip mode and object grip mode. The sensors determine which mode the glove is in depending on the gesture made. The glove is examined using a pencil and a cylindrical object to evaluate the strength of the grip. After gripping the object or pencil, the system evaluates the force applied using the sensors. This data is transferred to a computer for further analysis using a trained model. The model was able to achieve an accuracy of 90.8%.</p>

Associations of grip strength, walking pace, and the risk of incident dementia: A prospective cohort study of 340212 participants.

Grip strength and walking pace have been linked to cognitive dysfunction. Their relationships, however, demand further clarification as the evidence is derived primarily from less-comprehensive investigations. A total of 340212 UK Biobank participants without dementia and cardiovascular diseases at baseline were analyzed. Cox proportional hazard models assessed the longitudinal associations. Over a mean follow-up of 8.51 ± 2.68 years, 2424 incident dementia cases were documented. A 5 kg increment of absolute grip strength was associated with lower risks of all-cause dementia (hazard ratio [HR] 0.857), Alzheimer's disease (HR 0.874), and vascular dementia (HR 0.788). The patterns of associations remained similar when grip strength was expressed in relative terms and quintiles. A slow walking pace demonstrated consistent associations with increased risks of all dementia types. Our findings provide amplified evidence and suggest that muscle fitness, reflected by objective grip strength measures and self-reported walking pace, may be imperative for estimating the risks of dementia.

Dynamically Tunable Dry Adhesion through a Subsurface Thin Layer with Tunable Stiffness

AbstractRecently, a novel concept to realize dynamically tunable dry adhesion via subsurface stiffness modulation (SSM) in a composite core–shell structure has been introduced and demonstrated for gripping and release of objects. Here, a variant form of the composite core–shell design is proposed to significantly improve the performance of dynamically tunable dry adhesion in terms of activation time and activation voltage. Specifically, composite pillars with an embedded microfluidic channel filled with a low melting point alloy (LMPA) are fabricated, and the adhesion of the pillars is characterized as a function of LMPA state: either melted or solid. The effects of the thickness and in‐plane pattern of the LMPA channel, as well as the depth at which it is embedded on tunable adhesion are investigated. Experiments show that the effective adhesion strength can be reduced up to 50%, equivalent to a 2× change in dry adhesion when the LMPA is melted. Finite element analysis of the stress distribution change under SSM shows that the experimentally observed tunable adhesion is primarily due to stiffness change close to the interface. In addition, two technology demonstrations of composite pillars picking and releasing objects with fast activation (≈1 s) and low activation voltages (≈1 V) are included.

Position/force modeling and analysis of a piezo-driven compliant micro-gripper considering the dynamic impacts of gripping objects

The compliant micro-gripper driven by piezo actuator has emerged as a representative end-effector in micro-manipulations. To achieve high performance gripping of tiny and fragile objects, the switched position/force modeling approach has been well explored for such systems. In the present work, we investigate a lever-bridge-lever type piezo-driven compliant micro-gripper and develop a new position/force model to describe both kineto-statics and dynamics of the micro-gripper, where the free motion and gripping motion states in the manipulation process are unified in the modeling approach. In particular, the impacts of gripping objects on the dynamic properties of the gripper (in gripping motion state) are incorporated by considering the gripping object as a spring-damper system with a characteristic length. With this, the dynamic model can better predict the position of the gripping jaw and the contact position of the object, as well as the force applied on the object, which also offers the capability to estimate the stiffness of unknown objects in manipulations. Various gripping experiments with soft and stiff objects of different dimensions are conducted, which demonstrate the effectiveness and accuracy of the proposed modeling approach.

Parameter estimation and object gripping based on fingertip force/torque sensors

Object parameters, like the mass and barycenter, are significant for the stability of object gripping. This study proposes a novel method to estimate the mass and barycenter coordinate of the task object based on the fingertip force/torque sensor. The equilibrium conditions of force and torque are deduced, and the estimation models are built for mass and barycenter coordinate. In particular, the principal component analysis (PCA) method is used to reduce inter-dimensional coupling and extract principal components for the multi-dimensional and multi-redundant signals of the fingertip force/torque sensor. Furthermore, an object parameter-based method is proposed for the task object gripping. Finally, we conduct a set of experiments to validate the effectiveness and generalization of the proposed method. The experiment results show that the parameter estimation method is effective to estimate the mass and barycenter coordinate, and the object parameter-based method can be generalized to grip irregular objects with varying gripping points.

Classification and Grip of Occluded Objects

The present paper exposes a system for detection, classification, and grip of occluded objects by machine vision, artificial intelligence, and an anthropomorphic robot, to generate a solution for the subjection of elements that present occlusions. The deep learning algorithm used is based on Convolutional Neural Networks (CNN), specifically Fast R-CNN (Fast Region-Based CNN) and DAG-CNN (Directed Acyclic Graph CNN) for pattern recognition, the three-dimensional information of the environment was collected through Kinect V1, and tests simulations by the tool VRML. A sequence of detection, classification, and grip was programmed to determine which elements present occlusions and which type of tool generates the occlusion. According to the user's requirements, the desired elements are delivered (occluded or not), and the unwanted elements are removed. It was possible to develop a program with 88.89% accuracy in gripping and delivering occluded objects using networks Fast R-CNN and DAG-CNN with achieving of 70.9% and 96.2% accuracy respectively, detecting elements without occlusions for the first net and classifying the objects into five tools (Scalpel, Scissor, Screwdriver, Spanner, and Pliers), with the second net. The grip of occluded objects requires accurate detection of the element located at the top of the pile of objects to remove it without affecting the rest of the environment. Additionally, the detection process requires that a part of the occluded tool be visible to determine the existence of occlusions in the stack

Classification and Grip of Occluded Objects

The present paper exposes a system for detection, classification, and grip of occluded objects by machine vision, artificial intelligence, and an anthropomorphic robot, to generate a solution for the subjection of elements that present occlusions. The deep learning algorithm used is based on Convolutional Neural Networks (CNN), specifically Fast R-CNN (Fast Region-Based CNN) and DAG-CNN (Directed Acyclic Graph CNN) for pattern recognition, the three-dimensional information of the environment was collected through Kinect V1, and tests simulations by the tool VRML. A sequence of detection, classification, and grip was programmed to determine which elements present occlusions and which type of tool generates the occlusion. According to the user's requirements, the desired elements are delivered (occluded or not), and the unwanted elements are removed. It was possible to develop a program with 88.89% accuracy in gripping and delivering occluded objects using networks Fast R-CNN and DAG-CNN with achieving of 70.9% and 96.2% accuracy respectively, detecting elements without occlusions for the first net and classifying the objects into five tools (Scalpel, Scissor, Screwdriver, Spanner, and Pliers), with the second net. The grip of occluded objects requires accurate detection of the element located at the top of the pile of objects to remove it without affecting the rest of the environment. Additionally, the detection process requires that a part of the occluded tool be visible to determine the existence of occlusions in the stack

Comparative Evaluation of Approaches for Determination of Grasp Points on Objects, Manipulated by Robotic Systems

This paper considers comparative evaluation of recent methods for grip point determination for manipulations with objects in the scene. This research is aimed to compare and evaluate the modern approaches of grip point determination, when this process is aided by computer vision. The methods of object gripping, considered in this paper, are employed in connection with depth map composition, backed by neural network model ResNet-50, which allowed to omit application of specific depth sensors in the course of experiments. This research shows dependencies of successful grip probability from the things being manipulated. Probability scores, averaged over different types of objects for the methods GPD, 6-DOF GraspNet, VPG, were, accordingly, 0.690, 0.741, 0.613. The paper also considers dependencies of successful grip probability from object sizes, distances from the capturing camera and target objects in the scene, luminosity levels, as well from the angles of scene inspection along the vertical axis. In terms of the considered methods GPD, 6-DOF GraspNet, VPG, non-linear increasing dependencies are revealed for object type-averaged probabilities of successful grip from luminosity level of the scene. It was also discovered, that the dependencies of successful grip for all the other parameters are non-linear and non-monotonic. The ranges of the values for scene parameters under consideration are defined in this paper, which ensure the highest probability values for object grip in these approaches. Upon the results of the performed experimental evaluation, the 6-DOF GraspNet solution showed the best performance for the vast majority of the considered parameters of the scene. The approach, presented in this paper, is the preferable way for solution of grip point problem, in context of methods, which assume depth map reconstruction without specific equipment.

Does a Modified Technique to Achieve Arthrodesis of the Wrist After Resection of the Distal Radius and Translocating the Ipsilateral Ulna as a Vascularized Graft to Reconstruct the Defect Improve Grip Strength and Outcomes Scores?

Ten years ago, we reported the results of a procedure in which we translocated the ipsilateral ulna as a vascularized autograft to reconstruct defects of the distal radius after tumor resection, with excellent functional results. At that time, wrist arthrodesis was achieved by aligning the translocated ulna with the scapholunate area of the carpus and usually the third metacarpal. This resulted in wrist narrowing. We then wondered if aligning the translocated ulna with the scaphoid and the second metacarpal would result in ulnar deviation and thereby improve grip strength. We believed lateralization would reduce the wrist narrowing that occurs with fusion to the third metacarpal and would make the cosmesis more acceptable. We also modified the incision to dororadial to make the scar less visible and thus improve the cosmesis. (1) Is there an objective improvement in grip strength and functional scores (Musculoskeletal Tumor Society [MSTS] and Mayo wrist) when the translocated ulna is lateralized and the wrist is fused with the translocated ulna and aligned with the second metacarpal versus when the translocated ulna is aligned with the third metacarpal? (2) Did lateralization caused by the wrist fusion aligned with the second metacarpal minimize wrist narrowing as measured by the circumference compared with the fusion aligned with the third metacarpal? From 2010 and 2018, we treated 40 patients with distal radius tumors at our institution, 30 of whom had a distal radius enbloc resection. Twenty-eight patients had an ipsilateral ulna translocation and wrist arthrodesis in which the radius and translocated ulna were aligned with either the second (n = 15) or the third (n = 13) metacarpals. Two patients in the second metacarpal group and three patients in the third metacarpal group were lost to follow-up before 24 months after surgery and were excluded. A retrospective analysis of 23 patients (20 with giant cell tumors and three with malignant bone tumors) included a review of radiographs and institutional tumor database for surgical and follow-up records to study oncologic (local disease recurrence), reconstruction (union of osteotomy junctions, implant breakage or graft fracture, and wrist circumference), and functional outcomes (MSTS and Mayo wrist scores and objective grip strength assessment compared with the contralateral side). The results were compared for each study group (second metacarpal versus third metacarpal). There was no difference in the incidence of local recurrence or the time to union between the two groups. There were no implant breakages or graft fractures noted in either group. Patients in the second metacarpal group lost less grip strength compared with the unoperated side in the third metacarpal group (median 12% [range -30% to 35%] versus median 28% [15% to 42%], difference of medians 16%; p = 0.006). There were no between-group differences in terms of MSTS (median 30 [24 to 30] versus median 26.5 [22 to 30], difference of medians 3.5; p = 0.21) or Mayo wrist scores (median 83 [65 to 100] versus median 72 [50 to 90], difference of medians 11; p = 0.10). The second metacarpal group also had less wrist narrowing as seen from the median difference in circumference between the operated and unoperated wrists (median narrowing 10 mm [3 to 35 mm] in the second metacarpal group versus median 30 mm [15 to 35 mm] in the third metacarpal group, difference of medians 20 mm; p = 0.04). Wrist arthrodesis after ulna translocation with alignment of the translocated ulna and the second metacarpal provides a functional position with ulnar deviation that offers some improvement in grip strength but no improvement in the MSTS or Mayo scores. Radialization/lateralization of the translocated ulna achieved from the alignment with the second metacarpal decreases the reduction in the wrist circumference and therefore reduces wrist narrowing. Level III, therapeutic study.

Challenging the relationship of grip strength with cognitive status in older adults.

Grip strength is a widely used motor assessment in ageing research and has repeatedly been shown to be associated with cognition. It has been proposed that grip strength could enhance cognitive screening in experimental or clinical research, but this study uses multiple data-driven approaches to caution against this interpretation. Furthermore, we introduce an alternative motor assessment, comparable to grip dynamometry, but has a more robust relationship with cognition among older adults. Associations between grip strength and cognition (measured with the Montreal Cognitive Assessment) were analysed cross sectionally using multivariate regression in two datasets: (1) The Irish LongituDinal Study on Ageing (TILDA; N = 5,980, community-dwelling adults ages 49-80) and (2) an experimental dataset (N = 250, community-dwelling adults aged 39-98). Additional statistical simulations on TILDA tested how ceiling effects or skewness in these variables influenced these associations for quality control. Grip strength was significantly but weakly associated with cognition, consistent with previous studies. Simulations revealed this was not due to skewness/ceiling effects. Conversely, a new alternative motor assessment (functional reaching [FR]) had a stronger, more robust and more sensitive relationship with cognition compared to grip strength. Grip strength should be cautiously interpreted as being associated with cognition. However, FR may have a stronger and clinically useful relationship with cognition.