A cable-suspended intelligent crane assist device for the intuitive manipulation of large payloads

This paper presents a cable-suspended crane system to assist operators in moving and lifting large payloads. The main objective of this work is to develop a simple and reliable system to help operators in industry to be more productive while preventing injuries. The system is based on the development of a precise and reliable cable angle sensor and a complete dynamic model of the system. Adaptive horizontal and vertical controllers designed for direct physical human-robot interaction are then proposed. Different techniques are then proposed to estimate the payload acceleration in order to increase the controller performances. Finally, experiments performed on a full-scale industrial system are presented

An articulated assistive robot for intuitive hands-on-payload manipulation

This paper presents an intelligent assistive robot designed to help operators in lifting and moving large payloads through direct physical contact (hands-on-payload mode). The mechanical design of the robot is first presented. Although its kinematics are similar to that of a cable-suspended system, the proposed mechanism is based on articulated linkages, thereby allowing the payload to be offset from the rail support on which it is suspended. A dynamic model of the robot is then developed. It is shown that a simplified dynamic model can be obtained using geometric assumptions. Based on the simplified dynamic model, a controller is then presented that handles the physical human-robot interaction and that provides the operator with an intuitive direct control of the payload. Experimental validation on a full-scale prototype is presented in order to demonstrate the effectiveness of the proposed robot and controller

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In this paper, the singularity loci of the Gough-Stewart platform are studied and a graphical representation of these loci in the manipulator’s workspace is obtained. The algorithm presented is based on analytical expressions of the determinant of the Jacobian matrix, using two different approaches, namely, linear decomposition and cofactor expansion. The first approach is used to assess the effect of the architecture parameters on the nature of the singularity loci, while the second approach leads to a significant reduction of the computational complexity of the determinant. It is shown that, for a given orientation of the platform, the singularity locus in the Cartesian space is represented by a polynomial of degree three. Moreover, this polynomial equation is applied to several simplified Gough-Stewart architectures and it is shown that the expression is reduced when the base of the mechanism is coplanar and for other special geometries

Variable admittance control of a four-degree-of-freedom intelligent assist device

Robots are currently used in some applications to enhance human performance and it is expected that human/robot interactions will become more frequent in the future. In order to achieve effective human augmentation, the cooperation must be very intuitive to the human operator. This paper presents a variable admittance control approach to improve system intuitivity. The proposed variable admittance law is based on the inference of human intentions using desired velocity and acceleration. Stability issues are discussed and a controller design example is given. Finally, experimental results obtained with a full-scale prototype of an intelligent assist device are presented in order to demonstrate the performance of the algorithm

A Friendly beast of burden : a human-assistive robot for handling large payloads

This article presents a novel robotic assistive device for the handling of large payloads. The design of the robot is based on the application of the following fundamental mechanical principles: inertia is minimized, a parallel closed-loop cable/belt routing system is used to kinematically decouple the transmission from fixed actuators and to the end-effector, and variable static balancing is used to minimize the actuation forces required for vertical motion. As a result, the device requires only low power, thereby improving safety, and can be operated manually, even in the event of a power failure (with minimum backup power for brake release). A novel force/torque sensor is also introduced along with a control algorithm based on variable admittance that provides a very intuitive interface for physical human-robot cooperation. Finally, a full-scale prototype integrating all of the above concepts is presented

Insulin Resistance in Adolescents with Type 2 Diabetes Is Associated with Impaired Exercise Capacity

Context: The incidence of pediatric type 2 diabetes (T2D) is rising, with unclear effects on the cardiovascular system. Cardiopulmonary fitness, a marker of morbidity and mortality, is abnormal in adults with T2D, yet the mechanisms are incompletely understood