Grip Configuration Research Articles

Visual information following object grasp supports digit position variability and swift anticipatory force control.

Anticipatory force control underlying dexterous manipulation has historically been understood to rely on visual object properties and on sensorimotor memories associated with previous experiences with similar objects. However, it is becoming increasingly recognized that anticipatory force control also relies on how an object is grasped. Experiments that allow unconstrained grasp contact points when preventing tilting an object with an off-centered mass show trial-to-trial variations in digit position and subsequent scaling of lift forces, all before feedback of object properties becomes available. Here, we manipulated the availability of visual information before reach onset and after grasp contact (with no vision during the reach) to determine the contribution and timing of visual information processing to the scaling of fingertip forces during dexterous manipulation at flexible contact points. Results showed that anticipatory force control was similarly successful, quantified as an appropriate compensatory torque at lift onset that counters the external torque of an object with a left and right center of mass, irrespective of the timing and availability of visual information. However, the way in which anticipatory force control was achieved varied depending on the availability of visual information. Visual information following grasp contact was associated with greater use of an asymmetric thumb and index finger grasp configuration to generate a compensatory torque and digit position variability, together with faster fingertip force scaling and sensorimotor learning. This result supports the hypothesis that visual information at a critical and functionally relevant time point following grasp contact supports variable and swift digit-based force control for dexterous object manipulation.NEW & NOTEWORTHY Humans excel in dexterous object manipulation by precisely coordinating grasp points and fingertip forces, highlighted in scenarios requiring countering object torques in advance, e.g., lifting a teacup without spilling will demand a unique digit force pattern based on the grip configuration at lift onset. Here, we show that visual information following grasp contact, a critical and functionally relevant time point, supports digit position variability and swift anticipatory force control to achieve a dexterous motor goal.

Numerical and experimental study on protective film removal towards the automation of flexible electronics assembly

Flexible electronics is one of the most promising trends in the electronics industry, with increasing implementations in several application fields. However, in industrial applications, the assembly of film-based coverlays is still performed manually, representing a bottleneck in the whole production cycle, a source of defects caused by human errors, and introducing fatiguing tasks, such as the removal of the protective film covering the base material. In a novel methodology, this latter challenge is achieved by relying on the mechanical action of a rotating tool impacting the protective film. Such a process is typically stochastic and dependent on several parameters related to the tool-coverlay interaction, and the flexibility of film-type introduces further complexity. The aim of this paper is to investigate the influence of working conditions on the reliability of the process (i.e., success rate of the removal of the protective film). Finite element method (FEM) simulations are used to investigate and assess the stiffness exhibited by the component in response to the impacting force; therefore, a favorable gripping configuration is identified. An experimental campaign of the automated process is presented, aimed at assessing the effects of process parameters (tool rotating speed, adhesive thickness, approaching speed) on the protective film detachment. The results show that the process is predominantly affected by component-specific parameters, which, in turn, are significantly dependent on material supply conditions. Finally, useful insights are drawn to optimize the process and improve the design of the gripper of the robotized workcell.

Analysis of Successful Behaviors Leading to Groundwork Scoring Skills in Elite Judo Athletes.

The present study aimed (1) to propose an approach of observational analysis of the preceding standing judo (tachi-waza (TW)) context to a groundwork (ne-waza (NW)) grappling score (NWGS), and (2) to analyze the outcomes of applying such a model in high-level judoists. We conducted an observational analysis of 176 NW scoring actions of 794 combats observed in Baku’s World Judo Championships of 2018. Women scored more NWGS, performing more corporal controls but less segmental controls compared with the men. Moreover, NWGS were scored predominately during the second and third minutes of combat, independently of the sex or the weight category. Most NWGS occurred after an asymmetrical lateral structure, without showing associations with a particular type of NWGS. The movement structure of the attacking action during TW leading to an NWGS was predominantly techniques without turn, followed closely by techniques with turn, and barely performed after supine position techniques. Data showed that NWGS occurred more frequently after a failed TW attack (68.6%) than after a scored TW attack (31.4%). The TW attacker achieved NWGS with a higher frequency (62%) than the TW defender (38%), who mainly took advantage of a failed TW attack (98.5% vs. 1.5%, after failed vs. scored TW, respectively). The grip configurations most frequently employed during TW were dorsal-sleeve and flap-sleeve; overall, frontal grips were predominant over dorsal grips. However, no specific TW grip was related to success or grip progression before an NWGS. Our results will help judo coaches understand the influence of these factors on judo performance and optimize the planning and execution of technical–tactical content.

Judo technical-tactical dynamics: analysis of attack system effectiveness in high-level athletes

ABSTRACT This study aimed to determine which attack systems resulted in higher effectiveness in judo combats. We examined 5847 attacks from 152 high-level international male medallist athletes. Both successful (score) and unsuccessful attacks (no-score) were comprehensively analysed including six variables per action: attacker/defender approach, grip, stance, final displacement and direction of attack. Logistic regression, decision tree analyses and odds ratio (OR) were calculated to determine the probability of success for a given attack system. The main results indicated that i) gripping the dorsal region was decisive for an effective attack, ii) Right-Dorsal & Left-Dorsal grip configuration was the most efficient (P < 0.01, OR = 3.08), followed by Right-Dorsal & Left-Sleeve (P < 0.01, OR = 1.79) and Right-Sleeve & Left-Dorsal (P < 0.01, OR = 1.72), iii) hierarchical technical-tactical analysis identified that scoring rates for particular grips were highly influenced by the direction of attack and stance. Since this is the largest study so far examining attack effectiveness in judo, the information herein presented may have relevant implications for coaches by providing a new and practical organisation of combat dynamics and assisting in setting offensive/defensive plans to improve judo performance.

Pneumatically Controlled Reconfigurable Bistable Bionic Flower for Robotic Gripper.

Beyond their colorful appearances and versatile geometries, flowers can self-shape-morph by adapting to environmental changes. Nature-inspired artificial systems that mimic their natural counterparts in function, flexibility, and adaptation find an emerging application in mobile robotics. In this study, a novel reconfigurable bionic flower made of petal-shaped bistable carbon fiber-reinforced composites and actuated by soft pneumatic actuators is presented. A robotic gripper based on the bionic flower was then developed for transportation tasks. First, a bionic petal based on a hybridization of bistable composites was designed and a theoretical model was established to analyze its bistable characteristic. Second, experiments and simulations were performed to analyze the out-of-plane deformation and morphing processes of the bionic petal. Curvature analysis of the closing state and blooming state shows a good match with the theoretical results. Finally, a flower-inspired robotic gripper made of the bionic petal is demonstrated to evaluate its gripping performances, including gripping force, response time, and reliability. The functional tests confirmed that the proposed soft gripper can grip objects of various shapes, sizes, and weights within milliseconds response time. The stable gripping configuration was maintained through the bistability of the bionic petal without continuous pressure consumption. The high reliability of the gripper is very useful for gripping tasks under unstructured environments, where precise control over the robot is not possible.

Price of a Finger.

Background: Traumatic loss of an index finger is offered twice the amount of compensation as compared to a loss of little finger. However, the little finger plays a pivotal role in power grip thus is underestimated in its importance. Our aim was to test our hypothesis that loss of the little finger will result in greater or equal loss of grip strength compared to loss of the index finger. Methods: Grip strength in the power grip position was measured in 12 healthy volunteers using a JAMAR hand dynamometer. Grip strength of their dominant hand was recorded as a mean kg force of three attempts in three grip configurations 1) using all fingers 2) excluding the index finger and 3) excluding the little finger. Grip strength percentage compared to the full hand was calculated and statistical significance was investigated with a two-tailed T-test. Results: Participants' age varied from 19-64 years, with 4 males and 8 females. Mean full hand grip strength was 28.3 kg force; grip strength with index finger excluded was 65.8% and with little finger excluded was 66.2%. There was no significant difference in grip strength percentage when comparing index or little finger exclusion (p = 0.92). Conclusions: We did not find a difference in power grip using a simulated model of index or little finger loss in a healthy volunteer cohort. This should be taken into account in traumatic loss and work compensation.

Modeling the Configuration of a Robotic Gripper for Handling Agricultural Products

Purpose of research. Improvement of quality and speed of harvesting agricultural products through the development of models, control algorithms and multi-criteria optimization of the robotic gripper configuration. Methods. To achieve this goal, we have used the methods of mathematical and computer modeling, multi-criteria optimization, the theory of object-oriented design and programming. The mathematical model of the kinematic scheme of the prototype of the robotic gripper, its geometric constraints and objective functions used for optimization are described. Results. It has been performed a review of approaches to robotic harvesting of agricultural products, confirming the relevance of this study of robotic gripper configurations, which provides reliable fixation of an object without causing damage. The results of experiments on evaluating the developed algorithms and a software system for optimizing the configuration of a robotic gripper are presented. The developed software system AgroGripModeling for modeling the configuration of a robotic gripper using three a posteriori algorithms NSGA-II, MOGWO and MOPSO for multicriteria optimization is tested in the design of a prototype of a four-fingered gripper with a vacuum bellows for picking tomatoes. Conclusion. When designing a robotic gripper, it is necessary to take into account the variety of manipulated objects, the complexity of their identification and guidance of the manipulator in a complex natural environment with obstacles. The task of optimizing the capture mechanism is associated with the fulfillment of a number of conflicting requirements for reliability, softness, accuracy, speed, energy efficiency, which form a complex space for finding solutions. The developed AgroGripModeling software system provides modeling of the robotic gripping configuration and its quality assessment using three a posteriori algorithms NSGA-II, MOGWO and MOPSO. The system was tested with multicriteria optimization of the configuration of a prototype of a four-fingered gripper with a vacuum bellows for picking tomatoes.

Pneumatically Actuated Soft Gripper with Bistable Structures.

This study presents the design and test of a novel self-adaptive soft gripper, integrating pneumatic actuators and bistable carbon-fiber reinforced polymer laminates. The morphology was designed using the distinct structural characteristics of bistable structures; and the stable gripping configuration of the gripper was maintained through the bistability without continuous pressure application. The sufficient compliance of bistable structures makes the gripper versatile and adaptable to gripping deformable objects. First, a pneumatic-actuated method was introduced to achieve the reversible shape transition of the bistable structure. Next, three arrangement methods for actuators were analyzed with respect to the bistable transition and curvature, where it was found that the cross-arrangement is optimal. The effects of pneumatic actuators with different geometrical parameters on the response times are discussed, and the results show that the bistable structure can achieve shape transition within milliseconds under low pressure. Furthermore, the numerical and experimental results show good agreement between critical pressures and out-of-plane deformation. Furthermore, the shape retention function of the soft gripper was studied by using it to grasp objects of various sizes even when the pressure was reduced to the initial state. The bistable laminates exhibit sufficient compliance, and the deformed laminates can automatically accommodate the deformation of objects. The relationship between the weight and size of available gripping objects was studied; functional tests confirmed that the proposed soft gripper is versatile and adaptable for gripping objects of various shapes, sizes, and weights. This gripper has immense potential to reduce energy consumption in vacuum environments such as underwater and space.

Numerical investigation on the effect of specimen gripping arrangement on dynamic shear characterization using Torsion Split Hopkinson Bar

Torsion Split Hopkinson Bar (TSHB) is widely used in the dynamic shear characterization of material under pure shear loading. In TSHB, tubular specimens with either circular or hexagonal flanges are used. The specimens with circular flanges are generally bonded using adhesive to the incident and transmission bars. The specimens with hexagonal flanges are gripped into the hexagonal holders that are fixed onto incident and transmission bars. In the current study, numerical simulations are carried out to see the effect of gripping arrangements on the dynamic shear characterization quality. Numerical experiments with three gripping configurations are studied—the first gripping configuration with a direct bond (numerically-tie) between specimen and bars. The second configuration with the specimen gripped by hexagonal holders fixed to bars. The third configuration with specimen directly gripped into the incident and transmission bars having hexagonal slots.

Assembly of film coverlays: development of a configurable gripper for process automation

Despite the widespread use of electronic devices and consumer products integrating flexible electronics, in industrial practice, the assembly process of film-based coverlays is still performed manually, and this, in turn, affects process accuracy in first place. Additionally, the related manual tasks can be troublesome for workers, causing stress and fatigue. As a result, such a process can represent a bottleneck in the fabrication of Flexible Printed Circuit Boards (FPCBs).In the present paper, the architecture of a gripper is proposed as the core device of a completely automated film-coverlay assembly process. The architecture of the gripper is vacuum-based and exploits the action of several independent valves, enabling the grip configuration according to the geometry of the component. The gripper operation is shown by implementing specific solutions related to the removal of the coverlay protective film and partial coverlay thermal bonding, thus providing also a detailed description of the phases concerning a feasible automated assembly process. The results of the tests concerning the evaluation of both solutions are reported and discussed in the paper. Finally, a simplified gripper version is prototyped to perform some of the tests, and it is also used to preliminarily assess the performance of the gripping strategy, with good results.

The development of a novel grip motion analysis technique using the Dartfish movement analysis software to evaluate hand movements during activities of daily living

Individuals with hand osteoarthritis (OA) have impairments in grip strength and range of motion (ROM). Obtaining quantitative joint angle measures of the hand is difficult. Without a complete understanding of the kinematics of the hand, the assessment of hand OA when performing activities of daily living (ADL) and recreational activities is not fully understood. The objectives of this study were to establish a simple measurement technique (Grip Configuration Model) describing an individual's grip ROM using the Dartfish Movement Analysis Software, and compare the joint angle measures during maximum flexion/extension and five ADL in people with/without hand OA. Forty participants (20 without hand OA, 20 with hand OA) thumb CMC and MCP, and index MCP and PIP joint angles were evaluated for each activity using the Dartfish Software and Grip Configuration Model. Significant limitations of 17.2% (p < 0.001) and 12.7% (p = 0.01) were seen in the group with hand OA for maximum flexion/extension, respectively. The spray bottle task demonstrated a significant difference of 14.7% (p = 0.001) between the two test groups. Measurements using the Dartfish Software were compared against a manual goniometer and electromagnetic tracking system. This study demonstrated the weakened ROM in individuals with hand OA is translated to ADL and how the Grip Configuration Model simplifies the evaluation of how people grasp objects.

State-dependent TMS of inferior frontal and parietal cortices highlights integration of grip configuration and functional goals during action recognition

Understanding the object-directed actions of conspecifics not only implies recognition of the object (e.g., a pen) and processing of the motor components (e.g., grip configuration), but also identification of the functional goal of the action (e.g., writing). Motor components and goal representations are both known to be critically involved in action recognition, but how the brain integrates these two pieces of information remains unclear. Action priming was used to tune the cognitive system to the integration of grip and goal representations. We evaluated the effect of briefly presented primes sharing grip and/or goal information with the target on recognition of action photographs. Single-pulse transcranial magnetic stimulation (TMS) was applied at target onset over the inferior frontal cortex (IFC) or the inferior parietal lobule (IPL) to evaluate their involvement in integrating grip and goal information. IFC and IPL stimulation specifically reduced integration of these two pieces of information. These results demonstrate, for the first time, the existence of specialized neuronal populations dedicated to grip/goal integration within a fronto-parietal network, supporting the importance given to this network by sensorimotor and predictive models of action recognition.

Investigating the grip forces exerted by individuals with and without hand arthritis while swinging a golf club with the use of a new wearable sensor technology

Hand arthritis is the leading cause of disability in individuals over the age of 50, causing impairments in grip strength and range of motion. Golf is often recommended to patients with hand arthritis as a low-impact sport to maintain a healthy lifestyle. As such, numerous “arthritic” golf grips have been marketed, but lack quantitative measures to justify their use. The objective of this study was to quantify the differences in total applied grip force in golfers with/without hand arthritis using several types of golf grips. Twenty-seven participants (17 without and 10 with hand arthritis) were evaluated swinging mid-iron clubs with 12 different golf grip designs (9 standard and 3 “arthritic”). The trail hand thumb, index, middle, and ring finger applied grip forces were measured using the wireless FingerTPS system. Finger grip configuration (finger joint angles) of the thumb and index were measured using the Dartfish Movement Analysis Software paired with the newly developed Grip Configuration Model to obtain grip range of motion. Results indicated that golfers with hand arthritis had a significant deficit of 45% golf grip strength (P = 0.02). In addition, individuals with hand arthritis exhibited larger forces in 11 out of 12 golf grips tested when compared with their maximum golf grip strength. Despite how these grips are marketed, there are no “savings” in finger force or grip configuration when using the “arthritic” designed golf grips. Therefore, these grips may not be beneficial for patients with hand arthritis.

Evaluation of recessed and bar handles of freezer door in refrigerator

AbstractDesign components of handles can affect the physical demands on users and their satisfaction. However, few studies have evaluated the physical usability of different handle configurations in refrigerators. The objective of this study was to evaluate the effect of the handle height, clearance, embossing, and users’ stature on their physical demands and satisfaction with two different handle types. Twenty‐eight participants were recruited, and several design components, including the handle type (recessed, bar), height (620 and 680 mm), clearance (0, 3, 5, and 7 mm), embossing (with and without), and users’ stature (short, medium, and tall) were investigated. Regardless of handle type, higher handle (680 mm) exhibited a lower flexion angle and flexion moments of the hips and back compared with lower handle (620 mm), and participants expressed greater satisfaction with embossed handles when using the recessed handle. Handle height and comfortable grip configuration were the primary components that affected physical usability. The results could be useful in designing and improving refrigerator handles.

Action preparation in grasping reveals generalization of precision between implicit and explicit motor processes

It is often claimed that merely seeing a graspable object can elicit the implicit representation of a potential grasp. But can this representation affect the explicit execution of an actual grasp, and if so, how? In an open-loop paradigm, we instructed participants to grasp small, medium, or large test disks with the appropriate grip configuration (pincer, tripod, or pentapod). Before the presentation of these tests, we presented congruent or incongruent distractors. To assess interactions between implicit (putatively elicited by the distractors) and explicit (actually executed) sensorimotor processes, we measured preview reaction times (as an index of action preparation) and grasp kinematics (as an indicator of sensorimotor representations for motor control). Results indicate that action preparation is indeed affected by the presentation of preceding distractors. However, costs in action preparation were measured only when the first, implicit process was less precise than that of the actual grasp. We suggest that an interaction occurs at the level of sensorimotor processes through a mechanism which generalizes a precision parameter. We interpret these findings in relation to processes involved in real-time motor control and within the framework of theories of motor cognition.

The impact of the 2013 rule changes on gripping configuration in high-level judo athletes

Purpose: International Judo Federation introduced a set of new rules in a short time period (2009 − 2013). The aim of this research is to determine how the rule modification influences the gripping configurations used by elite male judo athletes.&#x0D; Methods: The sample contained 280 combats from the 2011 and 2014 World Championships. All the effective and ineffective throw attempts with related gripping configurations were registered.&#x0D; The Chi-square test was used to determine the difference between frequencies, along with Z-test for calculating the partial difference.&#x0D; Results: A total of 1707 actions and gripping configurations were registered. The Chi-square test showed that there is a significant difference in the usage of gripping configurations between the two championships (χ2=32,8; sig&lt;0,001). The Z-test showed a significant increase in the usage of kenka-yotsu and ai-yotsu, and a significant decrease in the usage of central grip, cross grip and situations where only tori has established a grip. The difference in the usage of the same side grip was not detected.&#x0D; Conclusion: The recommendation for coaches is to reduce the use of all other gripping configurations except kenka-yotsu and ai-yotsu when practicing techniques, especially unorthodox gripping like the cross grip and the same side grip.

A novel hand exoskeleton with series elastic actuation for modulated torque transfer

Among wearable robotic devices, hand exoskeletons present an important and persistent challenge due to the compact dimensions and kinematic complexity of the human hand. To address these challenges, this paper introduces HandeXos-Beta (HX-β), a novel index finger-thumb exoskeleton for hand rehabilitation. The HX-β system features an innovative kinematic architecture that allows independent actuation of thumb flexion/extension and circumduction (opposition), thus enabling a variety of naturalistic and functional grip configurations. Furthermore, HX-β features a novel series-elastic actuators (SEA) architecture that directly measures externally transferred torque in real-time, and thus enables both position- and torque-controlled modes of operation, allowing implementation of both robot-in-charge and user-in-charge exercise paradigms. Finally, HX-β’s adjustable orthosis, passive degrees of freedom, and under-actuated control scheme allow for optimal comfort, robot-user joint alignment, and flexible actuation for users of various hand sizes. In addition to the mechatronic design and resulting functional capabilities of HX-β, this work presents a series of physical performance characterizations, including the position- and torque-control system performance, frequency response, end effector force, and output impedance. By each measure, the HX-β exhibited performance comparable or superior to previously reported hand exoskeletons, including position and torque step response times on the order of 0.3 s, −3 dB cut-off frequencies ranging from approximately 2.5 to 4 Hz, and fingertip output forces on the order of 4 N. During use by a healthy subject in torque-controlled transparent mode, the HX-β orthosis joints exhibited appropriately low output impedance, ranging from 0.42 to −0.042 Nm/rad at 1 Hz, over a range of functional grasps performed at real-life speeds. This combination of lab bench characterizations and functional evaluation provides a comprehensive verification of the design and performance of the HandeXos Beta exoskeleton, and its suitability for clinical application in hand rehabilitation.

Contact points determination and validation for grasping of different objects by a four-finger robotic hand

Multi-finger robotic hands are analysed in comparison with human hands in terms of stable grasping and fine manipulation of different objects. Therefore, in order to attain a stable grasp, the contact points and the grip configuration must be selected in accordance with the grasp stability. In this paper, the four-fingered tendon actuated robotic hand is simulated to grasp different objects and determine the contact points of the fingertips on the surface of these objects. MATLAB SimMechanics tool is used to perform the simulation and 3D visualisation of the robotic hand where the fingers are controlled in order to grasp objects at the contact points. The obtained contact points are validated using the kinematics and geometric collision detection. These contact points are further utilised experimentally to determine the amount of weight required by the tendon to produce the flexion motion in order to grasp the object at the contact points.

Contact points determination and validation for grasping of different objects by a four-finger robotic hand

Multi-finger robotic hands are analysed in comparison with human hands in terms of stable grasping and fine manipulation of different objects. Therefore, in order to attain a stable grasp, the contact points and the grip configuration must be selected in accordance with the grasp stability. In this paper, the four-fingered tendon actuated robotic hand is simulated to grasp different objects and determine the contact points of the fingertips on the surface of these objects. MATLAB SimMechanics tool is used to perform the simulation and 3D visualisation of the robotic hand where the fingers are controlled in order to grasp objects at the contact points. The obtained contact points are validated using the kinematics and geometric collision detection. These contact points are further utilised experimentally to determine the amount of weight required by the tendon to produce the flexion motion in order to grasp the object at the contact points.

Decoding Information for Grasping from the Macaque Dorsomedial Visual Stream

Neurodecoders have been developed by researchers mostly to control neuroprosthetic devices, but also to shed new light on neural functions. In this study, we show that signals representing grip configurations can be reliably decoded from neural data acquired from area V6A of the monkey medial posterior parietal cortex. Two Macaca fascicularis monkeys were trained to perform an instructed-delay reach-to-grasp task in the dark and in the light toward objects of different shapes. Population neural activity was extracted at various time intervals on vision of the objects, the delay before movement, and grasp execution. This activity was used to train and validate a Bayes classifier used for decoding objects and grip types. Recognition rates were well over chance level for all the epochs analyzed in this study. Furthermore, we detected slightly different decoding accuracies, depending on the task's visual condition. Generalization analysis was performed by training and testing the system during different time intervals. This analysis demonstrated that a change of code occurred during the course of the task. Our classifier was able to discriminate grasp types fairly well in advance with respect to grasping onset. This feature might be important when the timing is critical to send signals to external devices before the movement start. Our results suggest that the neural signals from the dorsomedial visual pathway can be a good substrate to feed neural prostheses for prehensile actions.SIGNIFICANCE STATEMENT Recordings of neural activity from nonhuman primate frontal and parietal cortex have led to the development of methods of decoding movement information to restore coordinated arm actions in paralyzed human beings. Our results show that the signals measured from the monkey medial posterior parietal cortex are valid for correctly decoding information relevant for grasping. Together with previous studies on decoding reach trajectories from the medial posterior parietal cortex, this highlights the medial parietal cortex as a target site for transforming neural activity into control signals to command prostheses to allow human patients to dexterously perform grasping actions.