In PSA Peugeot Citroen factories, high precision requirements of workstations make them being manual. One of the main goal of the car manufacturer is to minimize the pain of workers while maintaining high efficiency of production lines. Consequently, assisting operators with an exoskeleton is a potential solution for improving ergonomics of painful workstations while respecting industrial constraints. To determine ergonomic performances of an exoskeleton, human joint angles and torques, ground reaction forces, and duration of operations are analysed for eight subjects performing a representative screwing task. Experiments were performed using ABLE upper-limb exoskeleton, developed by the French Atomic Energy Commission (CEA), which has the functionality to compensate arm and tools loads. Results show a clear reduction of the sum of the joints torques, up to 38.9%, given by ABLE supply and invite to make concrete the use of exoskeletons in car assembly lines.Relevance to industry: In industries, workers performing manual operations are subjected to musculoskeletal disorders (MSD). The usage of robotic devices such as exoskeletons might then be a relevant solution to reduce workers pain and prevent-MSD. The paper describes how to assess ergonomic performances of such robotic devices for a future usage in industry. (C) 2014 Elsevier B.V. All rights reserved.

This paper focuses on the construction of a Smith predictor for network-based haptic systems. Roughly speaking, the idea is to use a predictor just on the haptic side in order to compensate the viscosity effect and to provide an accurate feeling in the case of contacts. A new approach is presented by using the available information on the distance from the virtual reality simulator and introducing it in the predictor in order to maintain the similarity between the “real” and the “predicted model”. In order to validate the approach, experimental results are presented for constant and random varying delays (normal distributed and gamma with gap distributed), for a simple virtual environment and for a virtual box.

This paper presents a Proportional Derivative (PD) controller with gain-scheduling depending on the distance for haptic interfaces and virtual environments subject to communication delays. It is well known that the presence of delays deteriorates the overall system performance. More precisely, depending on the proposed architecture as, for example, bilateral position-position coupling, time-delays introduce a feeling of viscosity in free motion and reduce the sense of stiffness in the case of hard contacts. Even in the presence of time-delays, the controller gains can be tuned in order to guarantee the desired behavior and performances for one case (free or restricted motion) with the price of the completely loss of the other case performances and behavior. To overcome this drawback, a gain-scheduling controller is designed, able to guarantee the desired behavior and performances for free and restricted motion. The experimental results obtained on a three-degree of freedom real-time experimental platform enforce the theoretical developments.

This paper focuses on the stability analysis of Proportional-Derivative (PD) controllers for Multi-Input-Multi-Output (MIMO) systems affected by distributed time-delays. The time-delays will be approximated by the most common distributions (uniform and gamma with gap distributions). In order to provide practical guidelines for the design of PD controllers we describe the stability regions in the gains-parameter space using a geometric approach. Illustrative examples complete the presentation.

The aim of this paper is to present a comparative study of control algorithms for haptic interfaces and virtual environments subject to communication delays. It is well known that the presence of delays deteriorates the overall system performance. More precisely, delays introduce a feeling of viscosity in free motion and reduce the sense of stiffness in case of hard contacts. Six methods in their basic form (classic Proportional Derivative (PD), PD with local dissipation, PD with passivity observer, PD with passive set-point modulation, wave scattering transform and Smith predictor) are analyzed and compared, using a real-time experimental platform which enables tracking the impact of delays, from the point of view of position tracking error and transparency degree.

In this paper, we propose a method to study the fragility of Smith predictor-based controllers used in haptics. Using a geometric approach, we derive a simple approach to examine the fragility of Smith predictors for two cases - constant and uncertain delays. Illustrative examples complete the presentation.

It is well-known that iff the robot with its end-effector force control is passive, the closed loop system consisting of the robot and an arbitrary passive environment is asymptotically stable. Passive robot control, however, limits the achievable robot impedance reduction. Recently, investigated what performance can be achieved with nonpassive control when uncertainty bounds for the environment are known. The question of stability margins neglected in is treated in our companion paper. In this paper we report on experiments on a full scale industrial robot in order to identify six transfer functions from the velocity reference of the inner velocity loop to the end effector force output for six different environments, from solid wall to air. It is shown how the experimental data also makes it possible to compute the impedance of the controlled robot. Two controllers are designed: one marginally stable but with nonpassive and low-gain controlled robot impedance at low frequencies, and another controller respecting the stability margin of closed loop sensitivity gain less than 6 dB, but with a passive controlled robot impedance that has higher gain for low frequencies than that of the first controller. The designs are compared experimentally by having the robot interact with environments of different impedances, and with a human operator leading the robot The paper is concluded by a short discussion of the possible need of controller adaption when a robot operates in varying impedance environments, and interacts with a human operator.

It is well-known that if the robot with its end-effector force control is passive, the closed loop system consisting of the robot and an arbitrary passive environment is asymptotically stable. Passive robot control, however, limits the achievable robot impedance reduction. Recently, [1] (Buerger and Hogan, 2007) investigated what performance can be achieved with non-passive control when uncertainty bounds for the environment are known, but unfortunately neglected stability margins. Here we present a robust force control design with stability margins for Buerger and Hogan's example.

Comanipulation (i.e. a man and a robot sharing the same task) is an emerging robotics field. Despite interesting preliminary results, there is still a number of issues to be fixed for efficient implementation of cobotics, for example in the force amplification case. We will show how to solve problems like apparent inertia limitation, passivity constraints, force transient optimization, etc. Theoretical, as well as experimental results will be presented.

In the field of comanipulation (i.e. a man and a robot sharing the same task), force amplification is an interesting function that can be achieved by using two force sensors. This technique is known in the literature but little attention has been paid so far to stability/passivity properties. We will explain how to deal with passivity based stability criteria, and point out performance limitations of such a control in case of noncollocated and bandwidth limited force sensors. Theoretical, as well as experimental results will be presented.

The everyday use of robots as collaborative assistance to human workers (cobots) will not be possible until operator safety in robot workspace is guaranteed. Because of their strength and stiffness, efficient security of industrial robots can only be obtained thanks to robotic skin technology. Such a skin must have an optimized response time, cover curved shape and large surface of robot segments, be reliable, simple to build and cost effective. We present such a skin structure with early promising experimental results.

We focus on comanipulation, i.e. manipulation of an object simultaneously held by a robot and a human operator. In this domain, a major difficulty is raised by significant variations of human dynamics, which depend not only on the arm posture, but also on the muscular activity (muscular co-contraction) and more generally on the type of task being performed: fine positioning, gross and rapid movements, repeated movements, etc. An ideal comanipulation system should be able of adapting its behavior to the operator's functional intention, resulting in an intuitive assisting device. Toward this goal, we present in this paper first results of our research aimed at developing an instrumented handle mounted on a robot end-effector and held by an operator, that can be used for estimating the grasping force and for adapting the robot controller accordingly. We show first experimental evidences that changes in the grasping force drastically affect the robot controller performances. We thus propose a handle design and a gain scheduling strategy that result in a robot behavior adequate for any kind of grasps. This solution is successfully experimented with a 1 degree of freedom robot under largely variable comanipulation conditions, exhibiting a stable and efficiently adaptive behavior.

This paper presents a new portable exoskeleton design for superior limbs by the CEA-LIST laboratories. The first model described here (4 axis) is designed to apply forces in 3 directions The first application is foreseen as an assistance device to enable a disabled person to carry an object such as a teapot or water bottle. It is designed as a base for more complete systems. A partial realization of it is presented for the first time. The high potential of the actuators used both in terms of back drivability and force capacity, allows hybrid force-position control laws making it possible to cover a broad range of applications: rehabilitation, assistance, force feedback master arm for telerobotics, sport training, and a virtual reality workbench.

A new type of input-output stability is defined, based on the use of a Sobolev space W; W is well suited, like the Lebesgue space L/sub 2/, to obtain stability characterizations in the time and frequency domains. Moreover, if compared with L/sub 2/, W has additional properties which enable one to establish "local" stability results. A local version of the small gain theorem is established in this framework, as well as some consequences of this result, in particular local versions of the passivity theorem and of the circle criterion. The relationship between "W-stability" and asymptotic stability is studied.< >

A new type of input-output stability is defined, based on the use of a Sobolev space. A local version of the Small Gain Theorem is established in this framework, as well as a local version of the Passivity Theorem.

This paper presents a new way of designing steam turbine governor for power plants. This kind of system has one well-known nonlinearity that can be cancelled with classical feedback linearization. The partially linearized system has one unknown and rapidly changing nonlinearity that requires the use of robust linear control design. The originality of the paper is to use a modified feedback linearization technique to ensure that the association of the two regulators has sufficient robustness properties with satisfying performances