Finger Deformation Research Articles

Mechanoreception of pneumatic soft robotic finger without tactile sensor based on dual-position feature

Purpose Mechanoreception is crucial for robotic planning and control applications, and for robotic fingers, mechanoreception is generally obtained through tactile sensors. As a new type of robotic finger, the soft finger also requires mechanoreception, like contact force and object stiffness. Unlike rigid fingers, soft fingers have elastic structures, meaning there is a connection between force and deformation of the soft fingers. It allows soft fingers to achieve mechanoreception without using tactile sensors. This study aims to provide a mechanoreception sensing scheme of the soft finger without any tactile sensors. Design/methodology/approach This research uses bending sensors to measure the actual bending state under force and calculates the virtual bending state under assumed no-load conditions using pressure sensors and statics model. The difference between the virtual and actual finger states is the finger deformation under load, and its product with the finger stiffness can be used to calculate the contact force. There are distinctions between the virtual and actual finger state change rates in the pressing process. The difference caused by the stiffness of different objects is different, which can be used to identify the object stiffness. Findings Contact force perception can achieve a detection accuracy of 0.117 N root mean square error within the range of 0–6 N contact force. The contact object stiffness perception has a detection average deviation of about 15%, and the detection standard deviation is 10% for low-stiffness objects and 20% for high-stiffness objects. It performs better at detecting the stiffness of low-stiffness objects, which is consistent with the sensory ability of human fingers. Originality/value This paper proposes a universal mechanoreception method for soft fingers that only uses indispensable bending and pressure sensors without tactile sensors. It helps to reduce the hardware complexity of soft robots. Meanwhile, the soft finger no longer needs to deploy the tactile sensor at the fingertip, which can benefit the optimization design of the fingertip structure without considering the complex sensor installation. On the other hand, this approach is no longer confined to adding components needed. It can fully use the soft robot body’s physical elasticity to convert sensor signals. Essentially, It treats the soft actuators as soft sensors.

Electric discharge process modelling when piston pins recovery in internal combustion engines

Introduction. The relevance of the topic of the presented article is determined by the improvement of the technology for repairing and restoring machine parts. Currently, the technology of restoring piston pins of internal combustion engines (ICE) by a high-energy method of plastic deformation of metal using the energy of a high-voltage pulse discharge in a liquid is widely used – the electrohydraulic effect, and on its basis electrohydraulic processing. The purpose of the article is to increase the efficiency of the method of restoring piston pins of internal combustion engines due to the use of the electrohydraulic distribution method.Materials and methods. The research methods such as the analysis of the degree of influence of the electrical parameters of the electrohydraulic distribution process on the amount of deformation of the piston fingers depending on the relevant material were used. The article discusses a mathematical model of the electric discharge process when restoring piston pins. The calculation method determines the modes and parameters of the process of electrohydraulic distribution of piston pins while maintaining their fatigue life, static strength and wear resistance.Results. In this work, the degree of influence of the electrical parameters of the electrohydraulic distribution process on the amount of deformation of the piston pins, depending on the product material used, is established. A mathematical model of the electric discharge process during the restoration of piston pins has been developed, and based on them, the modes and parameters of the process of electrohydraulic distribution of piston pins have been determined while maintaining their fatigue life, static strength and wear resistance.Discussion and conclusions. The studies have shown that exploding wires made of iron, copper, and tungsten are not effective in restoring piston pins with an internal radius of up to 10 mm. The pressure in the case of their use does not exceed 100 MPa. Exploding Al wires with a diameter of less than one millimeter have the greatest effect. In this case, the inductance of the circuit should be minimal, because this provides the largest share of the energy released in the discharge channel from all stored in the capacitor. This ensures the highest pressure in the channel. Based on the same considerations, the capacity should be limited to a range of 3-12 UF. This method can be applied to the restoration of other car parts.

Parametric study of soft pneumatic robot grippers through finite element analysis

This paper investigates the gripping stress and deformation of pneumatically-actuated fluidic elastomer actuation (FEA)-based soft robotic gripper through ansys finite element analysis software. By varying gripper parameters, i.e. Input pressures and clearance to the object, simulations on the deformation of the soft fingers are performed to achieve gripping of the object. The motivation of this parametric study is to facilitate the design optimization of soft robotic grippers. Results demonstrate that grippers with lesser clearance to the object require lesser input pressure to achieve similar gripping stress on the object although it is evident that grippers with higher clearance are able to cater for wider range of object sizes.

Illusory deformation of the finger is more extensive in the distal than the lateral direction.

Previous studies have examined the rubber hand illusion with finger lengthening, but there is limited research on finger widening. This suggests a strong cognitive bias toward the illusory expansion of the finger in a distal direction rather than lateral. To test this, we compared the illusory deformability of the finger in the distal and lateral directions through the generation of illusory finger deformation using a double-touch operation, referred to as the numbness illusion. Our results showed that perceived distal distortion was wholly superior to perceived lateral distortion in terms of sense of ownership ratings. Moreover, the extent of the perceived deformation was greater in the distal than lateral direction, supporting our hypothesis that there is a distal bias. We suggest that this preference may be because the presence of multiple joints is required to create illusory deformation in the target direction.

Numerical analysis of a double interlocking padded finger seal performance based on thermo-fluid-structure coupling method

Non-contacting finger seals represent an advanced non-contacting and compliant seal in gas turbine sealing technology. This paper proposes a new structure of non-contacting finger seals with double interlocking pads. The numerical analysis model based on the thermo-fluid-structure coupling method for the new type finger seal was established. The influence of working conditions on leakage of the seal was studied and compared with the single padded non-contacting finger seal. The results show that the interface between the bottom of the finger pad and rotor surface is the main leakage path that forms the gas film with obvious variations of pressure and flow velocity. Under high temperature and high pressure operating conditions, the hydrodynamic effect of the gas film is enhanced, and lifting force is significantly improved. The deformation of fingers is composed of elastic deformation and thermal deformation. At room temperature, the deformation of fingers is mainly elastic deformation and points to the center of the rotor, which reduces the gas film clearance. The deformation of fingers at high temperature and high pressure creates a circumferentially convergent gap between the bottom of the pad and the rotor, which is beneficial to improve the loading capacity and to reduce leakage of the seal. Compared with the typical single padded non-contacting finger seal, the double interlocking padded finger seal proposed in this paper reduces the leakage factor by about 37%, which provides an advanced seal concept with the potential to improve sealing performance under high temperature and high pressure working conditions.

Effects of Individual Dimension Differences on Simulation of Finger Deformation for Tactile Distribution Display

Effects of Individual Dimension Differences on Simulation of Finger Deformation for Tactile Distribution Display

Management of Mallet Finger: Current Status (Review)

Background. Often, an incorrect treatment tactic injuries of the mallet finger can cause a pronounced dysfunction of the finger. In addition, remaining finger deformation can significantly reduce the aesthetic satisfaction of the patient. The relevance of the problem of this injury type can be mainly explained by the lack of a unified algorithm for choosing treatment tactics, and, as a result, a high percentage of unsatisfactory clinical results.
 Review purpose to assess the current state of the problem and the effectiveness of the proposed methods of treatment of mallet finger based on the analysis of the literature
 Results. The lack of a single protocol for the treatment of mallet finger leaves the question of choosing the optimal tactics open. The variability of interventions and indications for their implementation force specialists to rely on their own empirical experience when determining tactics in each clinical case. The search continues for the optimal type of suture and methods of immobilization with a closed injury in the Zone I to improve clinical results and minimize the risk of potential complications. The proposed modifications of blocked osteosynthesis have their own advantages, however, they require future studies on a larger cohort of patients to confirm their effectiveness. Various internal implants that allow to achieve anatomical reposition require additional studies due to the high risk of complications and insufficient stability of fixation. The obtained data are not enough to make a reasonable decision on the choice of the optimal method of treating the pathology in question. Along with a high percentage of complications, these factors significantly worsen the functional outcomes of treatment.
 Conclusion. Literature analysis shows that there is an active search for new surgical methods for the treatment of mallet finger injuries among both Russian and foreign specialists. The data obtained are not enough to make a reasonable decision on the choice of the optimal method of treating the pathology in question, since the results of the studies carried out are rather contradictory or require verification. This determines the need to improve treatment concepts with the elimination of existing shortcomings in order to create a well-founded algorithm for choosing a rational technique.

Apparent Randomness of the Normal-Force Dependence of the Coefficient of Friction between a Bare Finger and Artificial Skin under Active Tactile Exploration

When a finger actively slides over a surface, contact conditions including the contact area, sliding speed, and finger moisture naturally fluctuate. These random fluctuations lead to an apparent change of frictional properties and influence tactile pleasantness. Nonetheless, this probabilistic behavior has not been explicitly analyzed in previous studies on human fingertips. This study investigates the dependence of the coefficients of kinetic friction on the normal force produced by sliding a bare finger over different artificial skins with seven levels of hardness. The coefficient of friction was modeled as a power function of the normal force. An experimental study that involved sliding a finger over artificial skin surfaces was carried out under two conditions: the fingertip being wiped by a dry cloth or a cloth soaked in ethanol. Although the exponential term was assumed to be nearly constant for identical tribological conditions, we observed that the exponent varied randomly and could be negative, zero, or positive. This can be attributed to the variation of gross finger deformation that was not controlled during the observation. The probability density function of the exponent depended on the moisture content of the finger and object hardness. The variability of the exponent was higher for a soft material than it was for a harder material. In other words, for the softer materials, the exponent appears more random. Furthermore, the exponent tended to be positive and the coefficient of friction increased with the normal force when the finger was wiped with ethanol. These findings play an important role in understanding the frictional forces produced during skin–skin contact in terms of determining the root cause of random variations in the dependence of the coefficient of friction on the normal force.

Fruit Classification Utilizing a Robotic Gripper with Integrated Sensors and Adaptive Grasping

As the core component of agricultural robots, robotic grippers are widely used for plucking, picking, and harvesting fruits and vegetables. Secure grasping is a severe challenge in agricultural applications because of the variation in the shape and hardness of agricultural products during maturation, as well as their variety and delicacy. In this study, a fruit identification method utilizing an adaptive gripper with tactile sensing and machine learning algorithms is reported. An adaptive robotic gripper is designed and manufactured to perform adaptive grasping. A tactile sensing information acquisition circuit is built, and force and bending sensors are integrated into the robotic gripper to measure the contact force distribution on the contact surface and the deformation of the soft fingers. A robotic manipulator platform is developed to collect the tactile sensing data in the grasping process. The performance of the random forest (RF), k-nearest neighbor (KNN), support vector classification (SVC), naive Bayes (NB), linear discriminant analysis (LDA), and ridge regression (RR) classifiers in identifying and classifying five types of fruits using the adaptive gripper is evaluated and compared. The RF classifier achieves the highest accuracy of 98%, while the accuracies of the other classifiers vary from 74% to 97%. The experiment illustrates that efficient and accurate fruit identification can be realized with the adaptive gripper and machine learning classifiers, and that the proposed method can provide a reference for controlling the grasping force and planning the robotic motion in the plucking, picking, and harvesting of fruits and vegetables.

Structural Optimization Method of a FinRay Finger for the Best Wrapping of Object

Soft gripping, in which the gripper adapts to differently shaped objects, is in great demand for use in unknown or dynamically changing environments and is one of the main research subjects in soft robotics. Several systems have already been created, one of which is a passive shape-adaptable finger based on the FinRay effect. The geometric shape of this finger ensures that the finger wraps around the object it grips. FinRay fingers have been studied in several studies, which have changed the internal structure and examined how gripping force’s dependence on finger deformation changes. So far, however, no specific way has been determined to evaluate the proposed finger regarding its ability to wrap around the object. This work comes up with a new and simple method to evaluate the finger’s wrapping around the object mathematically. Based on this evaluation method, several different patterns of the internal structure of FinRay fingers were tested. The fingers were first tested in a simulation program, which simulated a steel roller indentation with a diameter of 20 mm in the middle of the finger’s contact surface. Based on the simulation results, selected types of structure were made by the Fused Filament Fabrication method from a flexible filament and tested on a real test rig to verify the results of the simulation and compare it with the real behaviour. According to the methodology used, the results show that the most suitable structure of the selected tested fingers from the point of view of wrapping the finger around the object is a structure without internal filling. Designers can simply use the new evaluation method to compare their designed finger variants and select the most suitable one according to the ability to wrap around the gripped object. They can also use graphs from this work’s results and determine the finger’s dimensions without internal filling according to the required forces and deflection.

Investigation of human perception of tactile graphics and its dependence on fundamental friction mechanisms

Accurate depiction of visual information presents a formidable obstacle to the inclusion of people with visual impairments in standardized educational assessment. This challenge is often addressed by using tactile graphics, such as the use of a collection of tactile patterns representing various zones similar to the use of colors to represent political boundaries on a visual map. This study investigated friction mechanisms involved during fingertip exploration of tactile graphics, as well as the role that friction played in forming perceptions. Perception experiments were run using four texture types published by the Braille Authority of North America (BANA): two parallel-ridge textures of different ridge widths and spacings, and two ordered-dot textures of different dot spacings. To minimize tactile confusion, BANA guidelines prohibit the use of similar textures adjacent to each other. In this study, texture pairs were printed adjacent to each other on thermally activated (‘swell touch’) tactile paper. Sighted human subjects participated in a blinded task of determining if the two textures in the pair were the same or different. Friction measurements of the fingertip exploration of the texture pairs was recorded using a dynamometer in a range of normal loads from 0.4 to 0.8 N. A generalized linear model (GLM) with a logistic link function was used to predict the influence of texture pair and participant on the likelihood of perceiving each texture pair as the same or different. Results showed that the particular texture pair had a strong correlation to the ability of participants to discern between textures. These quantitative results support the BANA guidelines. The friction data showed that there was not a significant amount of difference among the coefficients of friction of various textures, such that COF was not a strong predictor of perceptive ability. However, there was some evidence that penetration of the fingertip between raised texture elements, and interlocking with these elements, allowed for dissimilar dot patterns to be better discerned than dissimilar ridge patterns. The results indicate that there are other aspects, possibly still tribological in nature, that govern tactile perception when exploring tactile graphics. These phenomena may include such things as finger deformation and vibrational response produced during contact with individual texture elements.

Two-stage grasp strategy combining CNN-based classification and adaptive detection on a flexible hand

Robotic autonomous grasping of food-related objects requires a nondestructive and safe grasp system for picking up various objects. A novel underactuated flexible hand consisting of a variable palm and four soft fingers is designed and manufactured to enhance the grasp space and deformability during interaction with unknown objects. A position deviation formulation is fitted to estimate the free bend deformation of soft fingers approximately through finite element analysis. A modular convolutional neural network is presented to identify the grasp directions, shape features and anticipated input pressure levels of novel objects for achieving multitarget classification. A vision-based adaptive detection method is proposed to obtain an accurate wrist orientation and the best grasp candidate by using two means of grasp planning (i.e. cross grasp planning and equidistant optimal grasp planning). A two-stage grasp strategy combining the classification and detection methods is developed as an effective solution to estimate the grasp configuration accurately. Results show that our flexible hand achieves 91.1% success rate in a physical grasp experiment on a UR robot, thereby demonstrating the reliability and adaptability of our grasp approach. The target object can be identified and detected within 0.263 s, which indicates the suitability of our approach in real-time applications.

Wearable supercapacitor self-charged by P(VDF-TrFE) piezoelectric separator

Flexible piezoelectric self-charging supercapacitors (PSCS) are capable of converting random mechanical energy directly into electric energy and providing sustainable power source for various wearable electronic devices. In this work, using PDMS-rGO/C hybrid membrane as the positive and negative electrodes, P(VDF-TrFE) film as the piezoseparator, a flexible and ultralight PSCS was developed to harvest the mechanical energy of human finger curvature and simultaneously store as chemical energy in supercapacitors. The PSCS can be efficiently charged from finger deformation in the presence of polarized P(VDF-TrFE) separator film. When the finger was bended to 90°, the fabricated PSCS achieved a potential window of 0.45 V with the discharging time of about 18.0 s, and a stable charging current of 6.4 μA, providing a promising power solution to the next-generation self-powered wearable electronics system.

Improving the technology of part machining by surface plastic deformation

The purpose of this work is to study the technological process of strengthening hollow cylindrical parts of tractor engines using surface plastic deformation.Experimental studies in a wide range of changes in various factors have been preliminary performed on models. The data obtained were recalculated from the model to specific parts – piston fingers and bushings of the top heads of connecting rods in automotive tractor engines. The study was aimed at determining the efforts, stresses, changes in shape, the properties and structure of a parts' material. In the course of our study, the law of similarity was maintained, whereby the sample models were geometrically similar and physically identical to parts. The rational shape of machining tools was experimentally established – conical; as well as its optimum dimensions: angle of inclination, 10°30'; magnitude of the calibration belt, 6–7 mm, which provide for the magnitude of strengthening and surface quality of the machined material. We have experimentally established the effect of angle of inclination of the machining tool on the amount of a metal sticking to its working surface. The dependence of the amount of a sticking metal on its hardness and the elasticity module has been established. We have determined the impact of height of the calibration part of a machining tool on the roughness of a part's machined surface.The empirical dependence of machining allowance with a residual deformation along the outer diameter of a piston finger has been derived based on the laboratory data obtained. It has been found that the most dangerous are the tangential stresses along the outer surface of piston fingers, which were determined in the process of deformation by a strain gauge method. We have experimentally established the value of machining allowance over a single run of the working tool at vibration deformation of piston fingers, which ensures a reduction in tensile residual stresses. Our study into the static strength of piston fingers has found that the magnitude of wear depends on the following basic factors: a machining method, the material and time of operation.The research into the weight wear of piston fingers and bushings of the top heads of connecting rods has established that at vibration deformation the amount of wear is less compared to regular expansion. The magnitude of wear of the piston fingers restored by a vibration method is 1.13 times less than that in those restored by regular expansion

Bionic intelligent hydrogel actuators with multimodal deformation and locomotion

Inspired by common patterns of biological movement, a series of near-infrared (NIR) laser-driven bionic intelligent hydrogel actuators were successfully fabricated via the combination of infiltration method (entirety infiltration and locality infiltration), structure design and material characteristics. The controllable distribution of graphene oxide (GO) particles in a hydrogel matrix resulting from the infiltration method led to abundant bionic deformations with multiple degrees of freedom and flexibility. In addition to the highest response speed of 187.7°/s, the hydrogel actuators underwent accurate and repeatable static deformations and efficient and stabilized dynamic locomotion, demonstrated, for example, through the assembly of origami, the deformation of fingers and palm, the closing and blooming of a chrysanthemum and the crawling of an inchworm. This study opens a new path for practical bionic applications of NIR-triggered hydrogel actuators in self-assembly biosensor, targeted drug delivery and minimally invasive surgery.

Design, Simulation and Fabrication of a New Finger Support

This paper reports on the results of design and fabrication of a new finger support. Finger deformation is very common and has many causes and severity. Most of the available finger supports are not resizable and comfortable. They are mainly designed to fully restrict the finger’s motion when there has been any type of injury. However, for example in the case of early stages of arthritis, the patient should be able to use them whenever they want. Furthermore, the available finger supports cannot be adjusted considering various fingers’ sizes and positions. In this research, seven models of a polymer-metal composite finger support are designed. They are made of a soft polymer with inserted sheets of aluminum, steel or carbon-fiber. The optimal models are strong, and allow for size and finger position adjustments, and can be used for patients who already have distorted fingers and are working on them to regain some functions. Extensive finite element analysis of the support under the distributed loads of the finger, confirmed by the results obtained by a MATLAB program, shows that the new support tolerates the applied forces without any permanent deformation. Finally, the fabricated part using 3D printing validates the results.

Learning Object Grasping for Soft Robot Hands

We present a three-dimensional deep convolutional neural network (3D CNN) approach for grasping unknown objects with soft hands. Soft hands are compliant and capable of handling uncertainty in sensing and actuation, but come at the cost of unpredictable deformation of the soft fingers. Traditional model-driven grasping approaches, which assume known models for objects, robot hands, and stable grasps with expected contacts, are inapplicable to such soft hands, since predicting contact points between objects and soft hands is not straightforward. Our solution adopts a deep CNN approach to find good caging grasps for previously unseen objects by learning effective features and a classifier from point cloud data. Unlike recent CNN models applied to robotic grasping which have been trained on 2D or 2.5D images and limited to a fixed top grasping direction, we exploit the power of a 3D CNN model to estimate suitable grasp poses from multiple grasping directions (top and side directions) and wrist orientations, which has great potential for geometry-related robotic tasks. Our soft hands guided by the 3D CNN algorithm show 87% successful grasping on previously unseen objects. A set of comparative evaluations shows the robustness of our approach with respect to noise and occlusions.

A Common Circulatory Condition: Peripheral Arterial Disease

Figure 1: Ulcer and deformation of fingers due to peripheral arterial disease Clinical Image: Peripheral artery disease (also called peripheral arterial disease) is a common circulatory problem in which narrowed arteries reduce blood flow to your limbs. A 59 year old female admitted with history of trauma to the right foot since two days (Figure 1). This resulted in ulcer and deformation of fingers.

PACHYDERMODACTYLY IN A RHEUMATOLOGIST'S PRACTICE

Pachydermodactyly is a rare form of fibromatosis, which is characterized by an asymptomatic soft tissue enlargement around the proximal interphalangeal (PIP) joints of the hand. The etiology of the disease is unknown. Its possible triggers are recurrent minimal trauma, a habit or compulsive need to intertwine or rub the fingers. Spindle-shaped finger deformation with soft tissue thickening around the PIP joints mimics the clinical presentation of juvenile idiopathic arthritis (JIA). The distinctive features may be the absence of morning stiffness, contractures, pain, inflammatory and immunological changes in blood tests; however, it is the opinion of a number of authors that pachydermodactyly can be correctly diagnosed only after morphological examination. The paper gives the clinical manifestations of the disease and approaches to its diagnosis and differential diagnosis. It also describes the results of a retrospective study of 5 patients diagnosed as having pachydermodactyly. The final diagnosis was established after laboratory, instrumental, and morphological studies. Specific therapy has not been elaborated; however, by taking into account possible precipitating factors, excessive trauma of the affected finger bone should be avoided. The timely recognition of the disease allow to avoid administration of aggressive antirheumatic therapy required for JIA.

J2410106 3次元動作計測システムおよび3軸力センサによる引掻き動作の基礎的解析

Monitoring of scratching motion, accompany with itchiness, is important for the medical treatment of skin diseases associated with itchiness. In previous study, the sensor system for measuring human scratching by scratch sound is developed and the relationship between the scratch sounds and the mechanical characteristics of human scratch motion was investigated. However, evaluation of human scratching motion against their own skin is not enough, because it is difficult to measure the contact force against human skin during scratching human skin. Therefore, in this paper, in order to measure the contact force, such as pressing force and shearing force of human scratching motion against their own skin, a contact force estimation method using three dimensional motion measurement system is proposed. In experiment, motions of scratching weakly and strongly artificial skin placed on 3-axis force sensor were measured. And finger tip trajectories and deformation of artificial skin were analyzed and compared with contact force. From the result, it is confirmed that the proposed estimation method is available to estimate the contact force during scratching.