A wireless sEMG-based body-machine interface for assistive technology devices

Assistive technology (AT) tools and appliances are being more and more widely used and developed worldwide to improve the autonomy of people living with disabilities and ease the interaction with their environment. This paper describes an intuitive and wireless surface electromyography (sEMG) based body-machine interface for AT tools. Spinal cord injuries at C5-C8 levels affect patients' arms, forearms, hands, and fingers control. Thus, using classical AT control interfaces (keypads, joysticks, etc.) is often difficult or impossible. The proposed system reads the AT users' residual functional capacities through their sEMG activity, and converts them into appropriate commands using a threshold-based control algorithm. It has proven to be suitable as a control alternative for assistive devices and has been tested with the JACO arm, an articulated assistive device of which the vocation is to help people living with upper-body disabilities in their daily life activities. The wireless prototype, the architecture of which is based on a 3-channel sEMG measurement system and a 915-MHz wireless transceiver built around a low-power microcontroller, uses low-cost off-the-shelf commercial components. The embedded controller is compared with JACO's regular joystick-based interface, using combinations of forearm, pectoral, masseter, and trapeze muscles. The measured index of performance values is 0.88, 0.51, and 0.41 bits/s, respectively, for correlation coefficients with the Fitt's model of 0.75, 0.85, and 0.67. These results demonstrate that the proposed controller offers an attractive alternative to conventional interfaces, such as joystick devices, for upper-body disabled people using ATs such as JACO

Practical considerations on proprioceptive tactile sensing for underactuated fingers

RÉSUMÉ: Les mécanismes sous-actionnés sont de plus en plus répandus dans les nouvelles mains robotisées, en raison notamment du désir de réduire la complexité et les coûts associés aux systèmes conventionnels pleinement actionnés. Avec le même objectif de réduire les coûts des composants nécessaires pour assurer un retour sensoriel, de nombreux auteurs ont travaillé sur la recherche de solutions de rechange aux capteurs tactiles externes. Cet article traite de l’une de ces méthodes, à savoir, la mesure tactile proprioceptive, spécifiquement conçue pour les doigts sous-actionnés. Une attention particulière est portée sur certaines considérations pratiques telles que l’impact de la courbure de l’objet saisi et la reconfiguration du doigt après le contact. En outre, l’analyse de leur influence sur la précision de l’algorithme est proposée. À cette fin, des simulations et des données expérimentales sont présentées pour différents scénarios de saisie. On montre que l’effet de la courbure locale reste limité par rapport à d’autres causes d’imprécision telles que le frottement dans le système. Il est également démontré que la reconfiguration, si elle se fait à l’intérieur de limites raisonnables, n’entraîne pas de variation significative sur l’estimation du point de contact. ---------- ABSTRACT: Underactuated mechanisms are becoming more prevalent in new robotic graspers, partly because of the desire to reduce the complexity and associated costs of conventional fully actuated systems. With the same objective of reducing the costs of the components needed to provide a sensory feedback, several authors have worked on finding alternatives to external tactile sensors. This paper is about one of these methods, namely proprioceptive tactile sensing, especially designed for underactuated fingers. It focuses on certain practical considerations, such as the impact of the curvature of the grasped object and the reconfiguration of the finger after the contact, and proposes the analysis of their influence on the precision of the algorithm. To this aim, simulations and experimental data are provided for different grasping scenarios. It is shown that the effect of local curvature remains limited compared with other causes of imprecision such as friction in the system. It is also demonstrated that the reconfiguration, if within reasonable limits, does not cause significant variations on the estimation of the contact location

On The Dynamic Properties of Flexible Parallel Manipulators in the Presence of Payload and Type 2 Singularities

International audienceIt is known that a parallel manipulator at a singular configuration can gain one or more degrees of freedom and become uncontrollable. In our recent work [1], the dynamic properties of rigid-link parallel manipulators, in the presence of Type 2 singularities, have been studied. It was shown that any parallel manipulator can pass through the singular positions without perturbation of motion if the wrench applied on the end-effector by the legs and external efforts is orthogonal to the twist along the direction of the uncontrollable motion. This condition was obtained using symbolic approach based on the inverse dynamics and the study of the Lagrangian of a general rigid-link parallel manipulator. It was validated by experimental tests carried out on the prototype of a four-degrees-of-freedom parallel manipulator. However, it is known that the flexibility of the mechanism may not always been neglected. Indeed, for robots, joint flexibility can be the main source contributing to overall manipulator flexibility and can lead to trajectory distortion. Therefore, in our second paper [2], the condition of passing through a Type 2 singularity for parallel manipulators with flexible joints has been studied. In the present paper, we expand information about the dynamic properties of parallel manipulators in the presence of Type 2 singularity by including in the studied problem the link flexibility and the payload. The suggested technique is illustrated by a 5R parallel manipulator with flexible elements (actuated joints and moving links) and a payload. The obtained results are validated by numerical simulations carried out using the software ADAMS

Hands in the Real World

Robots face a rapidly expanding range of potential applications beyond controlled environments, from remote exploration and search-and-rescue to household assistance and agriculture. The focus of physical interaction is typically delegated to end-effectors -- fixtures, grippers or hands -- as these machines perform manual tasks. Yet, effective deployment of versatile robot hands in the real world is still limited to few examples, despite decades of dedicated research. In this paper we review hands that found application in the field, aiming to discuss open challenges with more articulated designs, discussing novel trends and perspectives. We hope to encourage swift development of capable robotic hands for long-term use in varied real world settings. The first part of the paper centers around progress in artificial hand design, identifying key functions for a variety of environments. The final part focuses on the overall trends in hand mechanics, sensors and control, and how performance and resiliency are qualified for real world deployment

Mechanomorphosis: Science, Management, and “Human Machinery” in Industrial Canada, 1900–45

By the early 20th century, the changes taking place in western industrial capitalist nations prompted an adaptive shift in the socioeconomic delineation of human bodies, and in scientific theories about how they worked and how they could be put to work. Just as the rising social sciences borrowed from medicine to convey images of social malaise, medicine increasingly appropriated an industrial vocabulary to conceptualize bodily health. Depicted variously as a machine, a motor, a factory in itself, the human body absorbed industrial symbolism. Modern industry demanded an intensification of labour that made bodily efficiency paramount. The corresponding definition of health also shifted, from emphasis on physical endurance, which could be secured by simple replacement of outworn workers, to optimum labour efficiency, which had to be actively instilled in all workers, present and future. Scientific management programs were easily integrated with regulatory medical notions concerning the human body and human nature, as science, medicine and technology combined forces to promote a machine ethic that equated modernity, progress, efficiency, and national health. This paper considers the relationship between changing conceptualizations of the human body, developing medical influence and state regulation of health, and attempts to “Taylorize” the labour process in early 20th century Canada

Natural language processing

Beginning with the basic issues of NLP, this chapter aims to chart the major research activities in this area since the last ARIST Chapter in 1996 (Haas, 1996), including: (i) natural language text processing systems - text summarization, information extraction, information retrieval, etc., including domain-specific applications; (ii) natural language interfaces; (iii) NLP in the context of www and digital libraries ; and (iv) evaluation of NLP systems