Search Results (5)

Grasping objects, from simple tasks to complex fine motor skills, is a key component of our daily activities. Our approach to facilitate the development of advanced prosthetics, robotic hands and human–machine interaction systems consists of collecting and combining surface electromyography (EMG) signals and contextual data of individuals performing manipulation tasks. In this context, the identification of patterns and prediction of hand grasp types is crucial, with cylindrical grasp being one of the most common and functional. Traditional approaches to grasp prediction often rely on unimodal data sources, limiting their ability to capture the complexity of real-world scenarios. In this work, grasp prediction models that integrate both EMG signals and contextual (task- and product-related) information have been explored to improve the prediction of cylindrical grasps during reaching movements. Three model architectures are presented: an EMG processing model based on convolutions that analyzes forearm surface EMG data, a fully connected model for processing contextual information, and a hybrid architecture combining both inputs resulting in a multimodal model. The results show that context has great predictive power. Variables such as object size and weight (product-related) were found to have a greater impact on model performance than task height (task-related). Combining EMG and product context yielded better results than using each data mode separately, confirming the importance of product context in improving EMG-based models of grasping. Full article

During the interaction process of a manipulator executing a grasping task, to ensure no damage to the object, accurate force and position control of the manipulator’s end-effector must be concurrently implemented. To address the computationally intensive nature of current hybrid force/position control methods, a variable-parameter impedance control method for manipulators, utilizing a gradient descent method and Radial Basis Function Neural Network (RBFNN), is proposed. This method employs a position-based impedance control structure that integrates iterative learning control principles with a gradient descent method to dynamically adjust impedance parameters. Firstly, a sliding mode controller is designed for position control to mitigate uncertainties, including friction and unknown perturbations within the manipulator system. Secondly, the RBFNN, known for its nonlinear fitting capabilities, is employed to identify the system throughout the iterative process. Lastly, a gradient descent method adjusts the impedance parameters iteratively. Through simulation and experimentation, the efficacy of the proposed method in achieving precise force and position control is confirmed. Compared to traditional impedance control, manual adjustment of impedance parameters is unnecessary, and the method can adapt to tasks involving objects of varying stiffness, highlighting its superiority. Full article

For more than 10 years, we have been observing the Fayda Tijaniyya and its ramifications around the world. Starting in 2006 we have been conducting observations in Nigeria, Niger, Senegal and Mauritania. Between 2015 and 2017, we closely followed some developments of the Fayda in the French capital and in other European cities. In parallel to these field investigations, we have been interested in the new religious arrangements that are gradually emerging in the United Kingdom. More recently, in 2020, we benefited from a stay in the USA which allowed us to widen our observation framework. From there, we were able to collect empirical material consisting of several dozen interviews, direct observation notes, private and public documents (reports, administrative documents, correspondences, letters of recommendation, press articles, travel chronicles and private videos, among others). In the Fayda Ibrahimiyya, the global culture suggests an update of the mode of inheritance, but in addition it makes emerge a new framework of activity essentially composed of a device of formation with global character, of a hybrid diplomatic-religious space, finally of a humanitarian action which appears as a missionary presenza. We first show that the conjunction of these three registers of action has as a condition, a process of articulation and appropriation through which the actors of the Fayda manage to convince of the link of identity that prevails between their own history and that of the founder. The conclusion of the article is devoted to a critical discussion in which we postulate that the imagination of a homogeneous global community comes up against a form of local resistance that is a counterpoint and probably an anti-globalizing replica. The historical socio-anthropology of comprehensive inspiration that we favour allows us to finely approach the interdependencies between these three registers and the narrative elaborated locally by the supporters of this community. The paradigm of mobility in which we place the Fayda, allows us to grasp the scope of the globalization of practices and uses, as well as the tension that operates between a dynamic of continuity and a dynamic of rupture that crosses for some decades this religious community. Full article

Bimanual telemanipulation is vital for facilitating robots to complete complex and dexterous tasks that involve two handheld objects under teleoperation scenarios. However, the bimanual configuration introduces higher complexity, dynamics, and uncertainty, especially in those uncontrolled and unstructured environments, which require more advanced system integration. This paper presents a bimanual robotic teleoperation architecture with modular anthropomorphic hybrid grippers for the purpose of improving the telemanipulation capability under unstructured environments. Generally, there are two teleoperated subsystems within this architecture. The first one is the Leap Motion Controller and the anthropomorphic hybrid robotic grippers. Two 3D printed anthropomorphic hybrid robotic grippers with modular joints and soft layer augmentations are designed, fabricated, and equipped for telemanipulation tasks. A Leap Motion Controller is used to track the motion of two human hands, while each hand is utilized to teleoperate one robotic gripper. The second one is the haptic devices and the robotic arms. Two haptic devices are adopted as the master devices while each of them takes responsibility for one arm control. Based on such a framework, an average RMSE (root-mean-square-error) value of 0.0204 rad is obtained in joint tracking. Nine sign-language demonstrations and twelve object grasping tasks were conducted with the robotic gripper teleoperation. A challenging bimanual manipulation task for an object with 5.2 kg was well addressed using the integrated teleoperation system. Experimental results show that the proposed bimanual teleoperation system can effectively handle typical manipulation tasks, with excellent adaptabilities for a wide range of shapes, sizes, and weights, as well as grasping modes. Full article

Robot hand is the device used for robots to interact with the environments, it has many potential applications. Traditional robot hands cannot translate their finger end along a straight line, which makes them not suitable for grasping thin objects on a flat surface. In order to overcome the bottleneck of traditional hands and enlarge the application possibility of robot hands, this paper develops a novel hybrid grasping modes hand with the variable geometrical structure (called VGS hand). The hand consists of 4-DOF (degree of freedom), two actuators and two fingers. It can perform both linear-parallel and self-adaptive grasping modes. Kinematics, dynamics, and contact forces analysis are conducted to provide a theoretical reference for the design. A prototype was manufactured for grasping experiments; the results of the experiments indicate that the hand has a good grasping performance and can meet different application requirements. Full article