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This work proposes a framework that improves the dexterous manipulation capabilities of two fingered grippers by: i) optimizing the finger link dimensions and the interfinger distance for a given object and ii) analyzing the effect of finger symmetry and the distance between the finger base frames on their manipulation workspaces. The results of the workspace analysis motivate the development of a multi-modal, adaptive robotic gripper. In particular, the finger link lengths optimization problem is solved by a parallel multi-start search algorithm. The optimal link lengths are then used for the workspace analysis. The results of the analysis demonstrate that different inter-finger distances lead to completely different workspace shapes and that the ratio defined by the area of the optimized workspace (nominator) and the union of all workspaces (denominator), is always significantly less than 1. This means that the area of the union of all workspaces is always larger than the area of the “optimized” workspace. Based on these results the proposed robotic gripper is equipped with reconfigurable finger bases that vary the inter-finger distance as well as with selectively lockable robotic finger joints, offering an increased dexterous manipulation performance without sacrificing grasping efficiency. The device is considered multi-modal as it can be used both as a parallel jaw gripper and as an adaptive robotic gripper.

The increased use of Virtual and Augmented Reality based systems necessitates the development of more intuitive and unobtrusive means of interfacing. Over the last years, Electromyography (EMG) based interfaces have been employed for interaction with robotic and computer applications, but no studies have been carried out to investigate the continuous decoding of the effects of human motion (e.g., manipulated object behavior) in simulated and virtual environments. In this work, we compare the object motion decoding accuracy of an EMG based learning framework for two different dexterous manipulation scenarios: i) for simulated objects handled by a teleoperated model of a hand within a virtual environment and ii) for real, everyday life objects manipulated by the human hand. To do that, we utilize EMG activations from 16 muscle sites (9 on the hand and 7 on the forearm). The object motion decoding is formulated as a regression problem using the Random Forests methodology. A 5-fold cross validation procedure is used for model assessment purposes and the feature variable importance values are calculated for each model. The decoding accuracy for the real world is considerably higher than the virtual world. Each of the objects examined had a single manipulation motion that offered the highest estimation accuracy across both worlds. This study also shows that it is feasible to decode the object motions using just the myoelectric activations of the muscles of the forearm and the hand. This is particularly surprising since simulations lacked haptic feedback and the ability to account for other dynamic phenomena like friction and contact rolling.

Robotic hand exoskeletons have become a popular and efficient technological solution for assisting people that suffer from neurological conditions and for enhancing the capabilities of healthy individuals. This class of devices ranges from rigid and complex structures to soft, lightweight, wearable gloves. In this work, we propose a hybrid (tendon-driven and pneumatic), lightweight, affordable, easy-to-operate exoskeleton glove equipped with variable stiffness, laminar jamming structures, abduction/adduction capabilities, and a pneumatic telescopic extra thumb that increases grasp stability. The efficiency of the proposed device is experimentally validated through five different types of experiments: i) abduction/adduction tests, ii) force exertion experiments that capture the forces that can be exerted by the proposed device under different conditions, iii) bending profile experiments that evaluate the effect of the laminar jamming structures on the way the fingers bend, iv) grasp quality assessment experiments that focus on the effect of the inflatable thumb on enhancing grasp stability, and v) grasping experiments involving everyday objects and seven subjects. The hybrid assistive, exoskeleton glove considerably improves the grasping capabilities of the user, being able to exert the forces required to execute a plethora of activities of daily living. All files that allow the replication of the device are distributed in an open-source manner.

Miniature indoor robotic airship platforms offer high mobility, safety, and extended flight times. This paper focuses on the feasibility, design, development, and evaluation of such a platform for robotics education and research. Selected commercially available envelope materials were considered and tested in terms of their helium retention capability and mechanical properties. The obtained envelope properties were used in a feasibility study, demonstrating that indoor airships are environmentally and financially viable, given an appropriate material choice. The platform's mechanical design was studied in terms of gondola placement and rotor angle positioning, resulting in an unconventional, asymmetric arrangement. The developed system was finally tested in a simple path following experiment for proof-of-concept purposes, proving its efficiency in attaining the desired heading and altitude configuration. The proposed robotic airship platform can be used for a variety of education and research oriented applications. Its design is open-source, facilitating replication by others.

In this paper, we focus on the formulation of a hybrid methodology that combines analytical models, constrained optimization schemes, and machine learning techniques to simplify the execution of dexterous, in-hand manipulation tasks with adaptive robot hands. More precisely, the constrained optimization scheme is used to describe the kinematics of adaptive hands during the grasping and manipulation processes, unsupervised learning (clustering) is used to group together similar manipulation strategies, dimensionality reduction is used to either extract a set of representative motion primitives (for the identified groups of manipulation strategies) or to solve the manipulation problem in a low-d space and finally an automated experimental setup is used for unsupervised, automated collection of large data sets. We also assess the capabilities of the derived manipulation models and primitives for both model and everyday life objects, and we analyze the resulting manipulation ranges of motion (e.g., object perturbations achieved during the dexterous, in-hand manipulation). We show that the proposed methods facilitate the execution of fingertip-based, within-hand manipulation tasks while requiring minimal sensory information and control effort, and we demonstrate this experimentally on a range of adaptive hands. Finally, we introduce DexRep, an online repository for dexterous manipulation models that facilitate the execution of complex tasks with adaptive robot hands. Note to Practitioners —Robot grasping and dexterous, in-hand manipulations are typically executed with fully actuated robot hands that rely on analytical methods, computation of the hand object system Jacobians, and extensive numerical simulations for deriving optimal strategies. However, these hands require sophisticated sensing elements, complicated control laws, and are not robust to external disturbances or perception uncertainties. Recently, a new class of adaptive hands was proposed which uses structural compliance and underactuation (less motors than the available degrees of freedom) to offer increased robustness and simplicity. In this paper, we propose hybrid methodologies that blend analytical models with constrained optimization schemes and learning techniques to simplify the execution of dexterous, in-hand manipulation tasks with adaptive robot hands.

Robot grasping in unstructured and dynamic environments is heavily dependent on the object attributes. Although Deep Learning approaches have delivered exceptional performance in robot perception, human perception and reasoning are still superior in processing novel object classes. Furthermore, training such models requires large, difficult to obtain datasets. This work combines crowdsourcing and gamification to leverage human intelligence, enhancing the object recognition and attribute estimation processes of robot grasping. The framework employs an attribute matching system that encodes visual information into an online puzzle game, utilizing the collective intelligence of players to expand the attribute database and react to real-time perception conflicts. The framework is deployed and evaluated in two proof-of-concept applications: enhancing the control of a robotic exoskeleton glove and improving object identification for autonomous robot grasping. In addition, a model for estimating the framework response time is proposed. The obtained results demonstrate that the framework is capable of rapid adaptation to novel object classes, based purely on visual information and human experience.

Despite the plethora of studies focusing on the design and development of dexterous robotic grippers and hands, researchers have not been able to quantify dexterity due to the lack of well defined measures or tests. Human dexterity on the other hand, is generally measured by employing various hand function tests. This work is inspired from these tests, proposing a new modular, affordable, accessible test for evaluating the grasping and manipulation capabilities of robotic end effectors. More precisely, the test allows for a quantification of the end-effectors' ability to perform various tasks effectively and irrespectively of the individual design parameters. The test rig proposed in this study combines the features of multiple dexterity tests originally developed for humans. The test quantifies dexterity through a weighted sum of task execution success, speed, and accuracy components that results to a dexterity score ranging from 0 (simplistic, nondexterous system) to 1 (human-like system). It should also be noted that dexterity can be evaluated assessing the efficiency of either the robotic hardware or the robotic perception system.

Over the last decades, the development of aerial robots for monitoring, grasping, and package delivery applications has gained momentum in both research and industry. However, grasping capable platforms are currently limited by the payload that they can carry and their operation time, due to the weight of the grasping mechanisms, their high energy consumption, and battery limitations. In this paper, we propose two reconfigurable, lightweight, robust grasping mechanisms that can be used in aerial robotic vehicles offering them grasping capabilities. The two solutions are: i) an ultra-lightweight, net-based design that utilises twisted string actuation to pull together eight 3D printed cylinders that are connected to a net, conforming around the object and ii) a reconfigurable, slider-based grasping mechanism that works like a supersized parallel jaw gripper, employing 3D-printed pads that slide on two carbon fibre shafts with linear bearings. The second design can also be configured as a shape-shifting, grasping capable device that can act as a flying gripper. The efficiency of the proposed grasping mechanisms has been experimentally validated with a series of experiments focusing on grasping of everyday objects and assessing their force exertion capabilities and durability.

Unstructured and uncertain environments that are encountered in search and rescue applications, require complex interactions that involve a wide range of grasps. These grasps are needed in order to handle unpredictable types of objects of various shapes, stiffnesses, and dimensions. Traditionally, the robotic end-effectors used in such situations are rigid and their operation requires sophisticated sensing elements and complicated control algorithms to manipulate delicate and fragile objects. Over the last decade, considerable research effort has been put into the development of adaptive, underactuated, and soft robots that facilitate robust interactions with dynamic environments. In this paper, we propose a three-fingered robotic gripper that combines pneumatic telescopic mechanisms and rigid claws. The gripper uses three large, rigid fingers to accomplish the execution of all the tasks required by a traditional robot gripper, while three inflatable, telescopic fingers provide soft interaction with objects. This synergistic combination of soft and rigid structures allows the gripper to cage / trap and firmly hold heavy and irregular objects. The experiments demonstrate that the gripper can successfully grasp a plethora of objects exerting up to 60 N of clench force.

Unmanned Aerial Vehicles (UAV) are typically based on rotorcraft designs and have been extensively used to perform mechanical interaction tasks that could involve inspection as well as search-and-rescue operations in critical unstructured and dynamic environments. UAV based aerial manipulation has also received an increased interest and it has attracted considerable research effort in the robotics community. However, the state-of-the-art control approaches that are being applied to traditional underactuated UAVs show critical stability issues during the execution of manipulation tasks. This is due to the fact that these tasks require the exertion of significant forces with respect to the vehicle-weight ratio. Designs of fully-actuated and overactuated systems show better suitability for such tasks but are still specific to certain functions and tasks, lacking the needed agility and flexibility. In this paper, we propose a novel design of an agile, coaxial, omnidirectional rotor module that can move and exert forces in all directions, without limitations on orientation and wiring. This independent rotor unit presents high mobility and maneuverability, high fight autonomy, and offers high potential for all terrain robotic manipulation applications. In this work, the proposed rotor module has been employed to develop an unconventional, hybrid, all terrain robotic rotorcraft that can act both as a drone and as a mobile robot.

Robots use their end-effectors to grasp and manipulate objects in unstructured and dynamic environments. Robot hands and grippers can vary from rigid and complex designs to soft, inflatable, and lightweight structures. In this paper, we focus on the development of a soft, retractable, telescopic gripper that exhibits an adaptive behaviour that allows efficient and stable grasps with a wide range of objects. The efficiency of the proposed device is experimentally validated through three different types of experiments: i) grasping experiments that involve different everyday objects, ii) force exertion experiments that capture the maximum forces that can be exerted by the proposed device, and iii) grasp resistance experiments that focus on the effect of the inflatable structure on resisting environmental uncertainties and disturbances. The proposed gripper is able to grasp a plethora of everyday life objects and it can exert more than 8 N of grasping force. The design is so low-cost that the soft fingers can be used in a disposable manner, facilitating the execution of specialized tasks (e.g., grasping in sterilized environments, handling of medical waste, etc).

Although soft robots are a good alternative to rigid, traditional robots due to their intrinsic compliance and environmental adaptability, there are several drawbacks that limit their impact, such as low force exertion capability and low resistance to deformation. For this reason, soft structures of variable stiffness have become a popular solution in the field to combine the benefits of both soft and rigid designs. In this paper, we develop laminar jamming flexure joints that facilitate the development of adaptive robot grippers with variable stiffness. Initially, we propose a mathematical model of the laminar jamming structures. Then, the model is experimentally validated through bending tests using different materials, pressures, and number of layers. Finally, the soft, laminar jamming structured are employed to develop variable stiffness flexure joints for two different adaptive robot grippers. Bending profile analysis and grasping tests have demonstrated the benefits of the proposed jamming structures and the capabilities of the designed grippers.

Robots and intelligent industrial systems that focus on sorting or inspection of products require end-effectors that can grasp and manipulate the objects surrounding them. The capability of such systems largely depends on their ability to efficiently identify the objects and estimate the forces exerted on them. This paper presents an underactuated, compliant, and lightweight hyper-adaptive robot gripper that can efficiently discriminate between different everyday life objects and estimate the contact forces exerted on them during a single grasp, using vision-based techniques. The hyper-adaptive mechanism consists of an array of movable steel rods that get reconfigured conforming to the geometry of the grasped object. The proposed object identification and force estimation techniques are model-free and do not rely on time consuming object exploration. A series of experiments have been carried out to discriminate between 12 different everyday life objects and estimate the forces exerted on a dynamometer. During each grasp, a series of images are captured that detect the reconfiguration of the hyper-adaptive grasping mechanism. These images are then used by an image processing algorithm to extract the required information about the gripper reconfiguration, classify the object grasped using a Random Forests (RF) classifier, and estimate the amount of force being exerted. The employed RF classifier gives a prediction accuracy of 100%, while the results of the force estimation techniques (Neural Networks, Random Forests, and 3rd order polynomial) range from 94.7% to 99.1%.

With the emergence of agile manufacturing in highly automated industrial environments, the demand for efficient robot adaptation to dynamic task requirements is increasing. For assembly tasks in particular, classic robot programming methods tend to be rather time intensive. Thus, effectively responding to rapid production changes requires faster and more intuitive robot teaching approaches. This work focuses on combining programming by demonstration with path optimization and local replanning methods to allow for fast and intuitive programming of assembly tasks that requires minimal user expertise. Two demonstration approaches have been developed and integrated in the framework, one that relies on human to robot motion mapping (teleoperation based approach) and a kinesthetic teaching method. The two approaches have been compared with the classic, pendant based teaching. The framework optimizes the demonstrated robot trajectories with respect to the detected obstacle space and the provided task specifications and goals. The framework has also been designed to employ a local replanning scheme that adjusts the optimized robot path based on online feedback from the camera-based perception system, ensuring collision-free navigation and the execution of critical assembly motions. The efficiency of the methods has been validated through a series of experiments involving the execution of assembly tasks. Extensive comparisons of the different demonstration methods have been performed and the approaches have been evaluated in terms of teaching time, ease of use, and path length.

Over the last years, hand exoskeletons have become a popular and efficient technical solution for assisting people that suffer from neurological and musculoskeletal diseases and enhance the capabilities of healthy individuals. These devices can vary from rigid and complex structures to soft, lightweight, wearable gloves. Despite the significant progress in the field, most existing solutions do not provide the same dexterity as the healthy human hand. In this paper, we focus on the development of a hybrid (tendon-driven and pneumatic), lightweight, affordable, wearable exoskeleton glove equipped with abduction/adduction capabilities and a pneumatic telescopic extra thumb that increases grasp stability. The efficiency of the proposed device is experimentally validated through three different types of experiments: i) abduction/adduction tests, ii) force exertion experiments that capture the maximum forces that can be applied by the proposed device, and iii) grasp quality assessment experiments that focus on the effect of the inflatable thumb on enhancing grasp stability. The hybrid assistive glove considerably improves the grasping capabilities of the user, being able to exert the forces required to assist people in the execution of activities of daily living.

In this paper, we present a methodology based on constrained optimization methods for estimating and compensating for post-contact parasitic object motions for underactuated, compliant robot hands and for deriving stable, minimal effort grasps to try to minimize these movements. To do so, we compute the object motions for different hand designs, object shapes, and object sizes and we synthesize appropriate robot arm trajectories that eliminate them, even in hands with complex flexure-based compliant members. The effectiveness of the proposed methods is validated using a seven DOF robot arm (Barrett WAM) and a range of compliant underactuated robot hands (Yale OpenHand models T42PP, T42PF, and T42FF). Note to Practitioners —During precision fingertip grasps, adaptive hands tend to move the object upon contact, to an equilibrium configuration determined by the elasticity of the mechanism and the forces exerted on the hand-object system. Such a behavior may be undesired for certain tasks (e.g., when grasping a full glass of water, the in-hand object perturbations may spill the water). In this paper, we propose a methodology for adaptive hands that derives stable minimal effort grasps, computes the post-contact parasitic object motions, and eliminates them using compensatory motions of a robot arm.

In this work, a Mixed Reality (MR) system is evaluated to assess whether it can be efficiently used in teleoperation tasks that require an accurate control of the robot end-effector. The robot and its local environment are captured using multiple RGB-D cameras, and a remote user controls the robot arm motion through Virtual Reality (VR) controllers. The captured data is streamed through the network and reconstructed in 3D, allowing the remote user to monitor the state of execution in real time through a VR headset. We compared our method with two other interfaces: i) teleoperation in pure VR, with the robot model rendered with the real joint states, and ii) teleoperation in MR, with the rendered model of the robot superimposed on the actual point cloud data. Preliminary results indicate that the virtual robot visualization is better than the pure point cloud for accurate teleoperation of a robot arm.

The concept of teleoperation has been studied since the advent of robotics and has found use in a wide range of applications, including exploration of remote or dangerous environments (e.g., space missions, disaster management), telepresence based time optimisation (e.g., remote surgery) and robot learning. While a significant amount of research has been invested into the field, intricate manipulation tasks still remain challenging from the user perspective due to control complexity. In this paper, we propose an intuitive, affordances oriented telemanipulation framework for a dual robot arm hand system. An object recognition module is utilised to extract scene information and provide grasping and manipulation assistance to the user, simplifying the control of adaptive, multi-fingered hands through a commercial Virtual Reality (VR) interface. The system’s performance was experimentally validated in a remote operation setting, where the user successfully performed a set of bimanual manipulation tasks.

Current grasping methods for aerial vehicles are slow, inaccurate and they cannot adapt to any target object. Thus, they do not allow for on-the-fly, ultra-fast grasping. In this paper, we present a passive closing, adaptive robot hand design that offers ultra-fast, aerial grasping for a wide range of everyday objects. We investigate alternative uses of structural compliance for the development of simple, adaptive robot grippers and hands and we propose an appropriate quick release mechanism that facilitates an instantaneous grasping execution. The quick release mechanism is triggered by a simple distance sensor. The proposed hand utilizes only two actuators to control multiple degrees of freedom over three fingers and it retains the superior grasping capabilities of adaptive grasping mechanisms, even under significant object pose or other environmental uncertainties. The hand achieves a grasping time of 96 ms, a maximum grasping force of 56 N and it is able to secure objects of various shapes at high speeds. The proposed hand can serve as the end-effector of grasping capable Unmanned Aerial Vehicle (UAV) platforms and it can offer perching capabilities, facilitating autonomous docking.

Adaptive, underactuated and compliant robot hands have received an increased interest over the last decade. Possible applications of these systems range from the development of simple grippers for industrial automation to the creation of anthropomorphic devices that can be used as prosthetic hands. These hands are particularly capable of extracting stable grasps even under significant object pose or other environmental uncertainties, due to the underactuation and the structural compliance of their designs. Despite the increased interest and the promising performance, adaptive hands suffer from several disadvantages and drawbacks. For example, the use of underactuation can lead to a post-contact reconfiguration of the fingers that compromises the force exertion capabilities of the system during pinch grasping. In this paper, we focus on the design, modelling, development, and evaluation of an adaptive robot gripper that uses magnets to adjust the reconfiguration profile of the fingers. The effect of the magnets increases the gripper’s force exertion capabilities in pinch grasps, without compromising the full / caging grasps. The efficiency of the proposed gripper is experimentally validated through two different tests: i) a contact force test that compares the results of a theoretical model with the actual experimental results and ii) a grasping test that assesses the force exertion capabilities and the reconfiguration behaviour of the adaptive fingers for different implementations of the magnetic joints.

Adaptive, underactuated, and compliant robot hands offer a promising alternative to the fully-actuated, rigid robotic devices that are typically considered for the execution of complex tasks that require significant dexterity. The increasing popularity of adaptive hands is due to their ability to extract stable grasps even under significant object pose or other environmental uncertainties, their lightweight and affordable designs and their intuitiveness and easiness of operation. Regarding possible applications, adaptive hands have been successfully used for the execution of both robust grasping and dexterous, in-hand manipulation tasks. However, the particular class of hands also suffers from certain shortcomings and drawbacks. For example, the use of underactuation leads to a post-contact reconfiguration of the fingers that may affect the force exertion capabilities of the hands during pinch grasping. In this paper, we focus on methods to predict the contact forces exerted by adaptive hands in pinch grasps, using their postcontact reconfiguration profile. The bending profiles of the fingers are recorded using ArUco trackers and IMU sensors that are embedded on the adaptive fingers and which are used to train appropriate regression models. More precisely, we examine the efficiency of the machine learning technique (Random Forests) in predicting the exerted contact forces during the reconfiguration phase of an adaptive finger. The accuracy of the proposed method is experimentally validated for a wide range of conditions, involving different prepositionings of the robot finger with respect to the employed force sensor.

Adaptive robot hands are typically created by introducing structural compliance either in their joints (e.g., implementation of flexure joints) or in their finger-pads. In this paper, we present a series of alternative uses of structural compliance for the development of simple, adaptive, compliant and/or under-actuated robot grippers and hands that can efficiently and robustly execute a variety of grasping and dexterous, in-hand manipulation tasks. The proposed designs utilize only one actuator per finger to control multiple degrees of freedom and they retain the superior grasping capabilities of the adaptive grasping mechanisms even under significant object pose or other environmental uncertainties. More specifically, in this work, we introduce, discuss, and evaluate: a) the concept of compliance adjustable motions that can be predetermined by tuning the in-series compliance of the tendon routing system and by appropriately selecting the imposed tendon loads, b) a design paradigm of pre-shaped, compliant robot fingers that adapt / conform to the object geometry and, c) a hyper-adaptive finger-pad design that maximizes the area of the contact patches between the hand and the object, maximizing also grasp stability. The proposed hands use mechanical adaptability to facilitate and simplify the efficient execution of robust grasping and dexterous, in-hand manipulation tasks by design.

Electromyography (EMG) based interfaces are the most common solutions for the control of robotic, orthotic, prosthetic, assistive, and rehabilitation devices, translating myoelectric activations into meaningful actions. Over the last years, a lot of emphasis has been put into the EMG based decoding of human intention, but very few studies have been carried out focusing on the continuous decoding of human motion. In this work, we present a learning scheme for the EMG based decoding of object motions in dexterous, in-hand manipulation tasks. We also study the contribution of different muscles while performing these tasks and the effect of the gender and hand size in the overall decoding accuracy. To do that, we use EMG signals derived from 16 muscle sites (8 on the hand and 8 on the forearm) from 11 different subjects and an optical motion capture system that records the object motion. The object motion decoding is formulated as a regression problem using the Random Forests methodology. Regarding feature selection, we use the following time-domain features: root mean square, waveform length and zero crossings. A 10-fold cross validation procedure is used for model assessment purposes and the feature variable importance values are calculated for each feature. This study shows that subject specific, hand specific, and object specific decoding models offer better decoding accuracy that the generic models.

Adaptive, tendon-driven and affordable prosthetic devices have received an increased interest over the last decades. Prosthetic devices range from body-powered solutions to fully actuated systems. Despite the significant progress in the field, most existing solutions are expensive, heavy, and bulky, or they cannot be used for partial hand amputations. In this paper, we focus on the development of adaptive, tendon-driven, glove-based, affordable prostheses for partial hand amputations and we propose two compact and lightweight devices (a body powered and a motor driven version). The efficiency of the devices is experimentally validated and their performance is evaluated using two different types of tests: i) grasping tests that involve different everyday objects and ii) tests that assess the force exertion capabilities of the proposed prostheses.

Soft, underactuated, and wearable robotic exo-gloves have received an increased interest over the last years. These devices can be used to improve the capabilities of healthy individuals or to assist people that suffer from neurological and musculoskeletal diseases. Despite the significant progress in the field, most existing solutions are still heavy and expensive, they require an external power source to operate, and they are not wearable. In this paper, we focus on the development of an affordable, underactuated, tendon-driven, wearable exo-glove equipped with a novel four-output differential mechanism that provides grasping capabilities enhancement to the user. The device and the differential mechanism are experimentally tested and assessed using three different types of experiments: i) grasping tests that involve different everyday objects, ii) force exertion capability tests that assess the fingertip forces for different types of grasps, and iii) tendon tension tests that estimate the maximum tendon tension that can be obtained by employing the proposed differential. The device considerably improves the grasping capabilities of the user with a weight of 690 g and an operation autonomy of a whole day.

This paper presents a compliant, underactuated finger for the development of anthropomorphic robotic and prosthetic hands. The finger achieves both flexion/extension and adduction/abduction on the metacarpophalangeal joint, by using two actuators. The design employs moment arm pulleys to drive the tendon laterally and amplify the abduction motion, while also maintaining the flexion motion. Particular emphasis has been given to the analysis of the mechanism. The proposed finger has been fabricated with the hybrid deposition manufacturing technique and the actuation mechanism's efficiency has been validated with experiments that include the computation of the reachable workspace, the assessment of the exerted forces at the fingertip, the demonstration of the feasible motions, and the presentation of the grasping and manipulation capabilities. The proposed mechanism facilitates the collaboration of the two actuators to increase the exerted finger forces. Moreover, the extended workspace allows the execution of dexterous manipulation tasks.

The field of Brain Machine Interfaces (BMI) has attracted an increased interest due to its multiple applications in the health and entertainment domains. A BMI enables a direct interface between the brain and machines and is capable of translating neuronal information into meaningful actions (e.g., Electromyography based control of a prosthetic hand). One of the biggest challenges in developing a surface Electromyography (sEMG) based interface is the selection of the right muscles for the execution of a desired task. In this work, we investigate optimal muscle selections for sEMG based decoding of dexterous in-hand manipulation motions. To do that, we use EMG signals derived from 14 muscle sites of interest (7 on the hand and 7 on the forearm) and an optical motion capture system that records the object motion. The regression problem is formulated using the Random Forests methodology that is based on decision trees. Regarding features selection, we use the following time-domain features: root mean square, waveform length and zero crossings. A 5-fold cross validation procedure is used for model assessment purposes and the importance values are calculated for each feature. This pilot study shows that the muscles of the hand contribute more than the muscles of the forearm to the execution of inhand manipulation tasks and that the myoelectric activations of the hand muscles provide better estimation accuracies for the decoding of manipulation motions. These outcomes suggest that the loss of the hand muscles in certain amputations limits the amputees’ ability to perform a dexterous, EMG based control of a prosthesis in manipulation tasks. The results discussed can also be used for improving the efficiency and intuitiveness of EMG based interfaces for healthy subjects.

─Robots need to use their end-effectors not only to grasp and manipulate objects but also to understand the environment surrounding them. Object identification is of paramount importance in robotics applications, as it facilitates autonomous object handling, sorting, and quality inspection. In this paper, we present a new hyper-adaptive robot hand that is capable of discriminating between different everyday objects, as well as ‘model’ objects with the same external geometry but varying material, density, or volume, with a single grasp. This work leverages all the benefits of simple, adaptive grasping mechanisms (robustness, simplicity, low weight, adaptability), a Random Forests classifier, tactile modules based on barometric sensors, and radar technology offered by the Google Soli sensor. Unlike prior work, the method does not rely on object exploration, object release or re-grasping and works for a wide variety of everyday objects. The feature space used consists of the Google Soli readings, the motor positions and the contact forces measured at different time instances of the grasping process. The whole approach is model-free and the hand is controlled in an open-loop fashion, achieving stable grasps with minimal complexity. The efficiency of the designs, sensors, and methods has been experimentally validated with experimental paradigms involving model and everyday objects.

Adaptive, underactuated and compliant robot systems have received an increased interest over the last decade. Possible applications of these systems range from the development of adaptive robot hands to tendon-driven, soft exosuits. Despite the significant progress in the field, some basic design issues such as the tendon termination and adjustment have not yet been addressed properly. In this paper, we focus on tendon-driven, underactuated systems and we propose a compact ratchet clutch mechanism that facilitates a fine tendon termination and adjustment. The proposed mechanism is experimentally compared with six common tendon termination solutions, using two different tests: i) an accuracy test to verify how precisely each mechanism can adjust the tendon length and ii) a tensile test to derive the strength limit of each mechanism. The experiments validate that the ratchet clutch system is a precise and robust mechanism that outperforms all the solutions compared. A cable driven finger was designed and built to accommodate the proposed mechanism and test its efficiency and applicability to devices that require compactness (e.g., adaptive robot hands). The design of the mechanism is disseminated in an open-source manner.

Adaptive robot hands have changed the way we approach and think of robot grasping and manipulation. Traditionally, pinch, fingertip grasping and dexterous, in-hand manipulation tasks were executed with fully actuated, rigid robot hands and relied on analytic methods, computation of the hand object Jacobians and extensive numerical simulations for deriving optimal and minimal effort grasps. However, even insignificant uncertainties in the modeling space could render the extraction of candidate grasps or manipulation paths infeasible. Adaptive hands use underactuated mechanisms and structural compliance, facilitating by design the successful extraction of stable grasps and the robust execution of manipulation tasks, even under significant object pose or other environmental uncertainties. In this paper, we propose a methodology for the automated extraction of dexterous, in-hand manipulation strategies / primitives for adaptive hands. To do so, we use a constrained optimization scheme that describes the kinematics of adaptive hands during the grasping and manipulation processes, an automated experimental setup for data collection, a clustering technique that groups together similar manipulation strategies, and a dimensionality reduction technique that projects the robot kinematics to lower dimensional manifolds. In these manifolds, control is simplified and hand operation becomes more intuitive. In this work, we also assess the effect of the extracted manipulation primitives on the object pose perturbations. The efficiency of the proposed methods is experimentally verified for various adaptive robot hands. The extracted primitives can simplify the operation and control of the open-source robot hand designs of the Yale Open Hand project in dexterous manipulation tasks.

A new class of simple, adaptive, under-actuated and compliant robot hands has recently attracted the interest of the robotics community. The under-actuated mechanisms and the structural compliance used in these hands facilitate and robustify not only grasping but also the execution of dexterous, in-hand manipulation tasks. Another significant characteristic of the particular hands is that they are able to efficiently grasp a wide range of everyday life objects even under significant object pose uncertainties. However, these hands, are difficult to model due to kinematic constraints introduced by the underactuation and the use of complex flexure joints. Moreover, adaptive hands tend to reconfigure upon contact with the object surface, imposing certain parasitic object motions. In this paper, we propose a learning scheme that uses the contact force measurements collected from tactile sensors to estimate the post-contact reconfiguration of the hand-object system and the imposed parasitic object motion. The learning scheme's estimates are compared with “ground truth” data that describe the actual motion of the object and that are collected using a vision based motion capture system. The proposed learning scheme can be used with any type of adaptive robot hand and its efficiency is experimentally validated using extensive paradigms involving different hand designs and various everyday life objects.

Robots are rapidly becoming part of our lives, coexisting, interacting, and collaborating with humans in dynamic and unstructured environments. Mapping of human to robot motion has become increasingly important, as human demonstrations are employed in order to “teach” robots how to execute tasks both efficiently and anthropomorphically. Previous mapping approaches utilized complex analytical or numerical methods for the computation of the robot inverse kinematics (IK), without considering the humanlikeness of robot motion. The scope of this work is to synthesize humanlike robot trajectories for robot arm-hand systems with arbitrary kinematics, formulating a constrained optimization scheme with minimal design complexity and specifications (only the robot forward kinematics (FK) are used). In so doing, we capture the actual human arm-hand kinematics, and we employ specific metrics of anthropomorphism, deriving humanlike poses and trajectories for various arm-hand systems (e.g., even for redundant or hyper-redundant robot arms and multifingered robot hands). The proposed mapping scheme exhibits the following characteristics: (1) it achieves an efficient execution of specific human-imposed goals in task-space, and (2) it optimizes anthropomorphism of robot poses, minimizing the structural dissimilarity/distance between the human and the robot arm-hand systems.

Data sets are crucial not only for model learning and evaluation but also to advance knowledge on human behavior, thus fostering mutual inspiration between neuroscience and robotics. However, choosing the right data set to use or creating a new data set is not an easy task, because of the variety of data that can be found in the related literature. The first step to tackle this issue is to collect and organize those that are available. In this work, we take a significant step forward by reviewing data sets that were published in the past 10 years and that are directly related to object manipulation and grasping. We report on modalities, activities, and annotations for each individual data set and we discuss our view on its use for object manipulation. We also compare the data sets and summarize them. Finally, we conclude the survey by providing suggestions and discussing the best practices for the creation of new data sets.

In this paper, we propose a hybrid methodology based on a combination of analytical, numerical and machine learning methods for performing dexterous, in-hand manipulation with simple, adaptive robot hands. A constrained optimization scheme utilizes analytical models that describe the kinematics of adaptive hands and classic conventions for modelling quasistatically the manipulation problem, providing intuition about the problem mechanics. A machine learning (ML) scheme is used in order to split the problem space, deriving task-specific models that account for difficult to model, dynamic phenomena (e.g., slipping). In this respect, the ML scheme: 1) employs the simulation module in order to explore the feasible manipulation paths for a specific hand-object system, 2) feeds the feasible paths to an experimental setup that collects manipulation data in an automated fashion, 3) uses clustering techniques in order to group together similar manipulation trajectories, 4) trains a set of task-specific manipulation models and 5) uses classification techniques in order to trigger a task-specific model based on the user provided task specifications. The efficacy of the proposed methodology is experimentally validated using various adaptive robot hands in 2D and 3D in-hand manipulation tasks.

Classical robotic approaches to tactile object identification often involve rigid mechanical grippers, dense sensor arrays, and exploratory procedures (EPs). Though EPs are a natural method for humans to acquire object information, evidence also exists for meaningful tactile property inference from brief, non-exploratory motions (a ‘haptic glance’). In this work, we implement tactile object identification and feature extraction techniques on data acquired during a single, unplanned grasp with a simple, underactuated robot hand equipped with inexpensive barometric pressure sensors. Our methodology utilizes two cooperating schemes based on an advanced machine learning technique (random forests) and parametric methods that estimate object properties. The available data is limited to actuator positions (one per two link finger) and force sensors values (eight per finger). The schemes are able to work both independently and collaboratively, depending on the task scenario. When collaborating, the results of each method contribute to the other, improving the overall result in a synergistic fashion. Unlike prior work, the proposed approach does not require object exploration, re-grasping, grasp-release, or force modulation and works for arbitrary object start positions and orientations. Due to these factors, the technique may be integrated into practical robotic grasping scenarios without adding time or manipulation overheads.

Coupling the human upper limbs with robotic devices is gaining increasing attention in the last decade, due to the emerging applications in orthotics, prosthetics and rehabilitation devices. In the cases of every-day life tasks, force exertion and generally interaction with the environment is absolutely critical. Therefore, the decoding of the user's force exertion intention is important for the robust control of orthotic robots (e.g. arm exoskeletons). In this paper, the human arm manipulability is analyzed and its effect on the recruitment of the musculo-skeletal system is explored. It was found that the recruitment and activation of muscles is strongly affected by arm manipulability. Based on this finding, a decoding method is built in order to estimate force exerted in the three-dimensional (3D) task space from surface ElectroMyoGraphic (EMG) signals, recorded from muscles of the arm. The method is using the manipulability information for the given force task. Experimental results were verified in various arm configurations with two subjects.

Humans perform a wide range of skillful and dexterous motion by adjusting the dynamic characteristics of their musculoskeletal system during motion. This capability is based on the non-linear characteristics of the muscles and the motor control architecture that can control motion and exerted force independently. Mechanical impedance (i.e. stiffness, viscosity and inertia) constitutes the most solid characteristic for describing the dynamic behavior of human movements. This paper presents a method for estimating upper limb impedance characteristics in the three-dimensional (3D) space, covering a wide range of the arm workspace. While subjects maintained postures, a seven-degrees-of-freedom (7-DoFs) robot arm was used to produce small displacements of subjects' hands along the three Cartesian axes. The end-point dynamic behavior was modeled using a linear second-order system and the impedance characteristics in the 3D space were identified using the measured forces and motion profiles. Experimental results were confirmed with two subjects.