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International audience; In this paper, we present a control strategy that enables intuitive physical human-robot collaboration with mobile manipulators equipped with an omnidirectional base. When interacting with a human operator, intuitiveness of operation is a major concern. To this end, we propose a redundancy solution that allows the mobile base to be fixed when working locally and moves it only when the robot approaches a set of constraints. These constraints include distance to singular poses, minimum of manipulability and distance to objects and angular deviation. Experimental results with a Kuka LWR4 arm mounted on a Neobotix MPO700 mobile base validate the proposed approach.

This paper presents a reactive collision avoidance algorithm for vehicles with unicycle-type nonholonomic constraints. Static and dynamic obstacles are avoided by keeping a constant avoidance angle to the obstacle. The algorithm compensates for the obstacle velocity, which can be timevarying. Conditions are derived under which successful collision avoidance is mathematically proved, and the theoretical results are supported by simulations. The proposed algorithm makes only limited sensing requirements of the vehicle. It is intuitive, has a low computational complexity and is suitable also for vehicles with a limited speed envelope or heavy linear acceleration constraints. This is demonstrated by applying the algorithm to a vehicle with a constant forward speed. © 2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.

International audience; Whether you are walking on a concrete floor, standing on a carpet, or sitting on a soft chair, your entire body continuously controls the posture and the contact forces that are produced by acting on rigid and compliant surfaces. Sometimes, like when reaching for a distant object or standing inside a moving bus that suddenly brakes, humans plan intentionally new contacts to preserve their balance and avoid falling. For humanoid robots to act in unstructured natural environments as humans do, contacts and physical interactions are necessary and unavoidable. This special issue of the Autonomous Robots journal aims at presenting the advances in whole-body control of real robots, focusing on control and learning techniques applied to estimation, control and adaptation of whole-body dynamics movement and contact forces that go beyond basic balancing abilities.

International audience; A pneumatic actuator with solenoid valves is a discontinuous-input system because each valve can be either in on or off state. For such an actuator, this paper proposes a sliding- mode control scheme that is based on an averaged continuous- input model of the discontinuous-input open-loop system. The averaged model is obtained from the nonlinear dynamics of the open-loop system undergoing pulse-width-modulation (PWM) at the input (i.e., valve open/close action). The PWM duty cycle will be regarded as a continuous input to the proposed averaged model, and thus generated by the proposed sliding- mode controller. For the sliding control design, we note that a pneumatic actu- ator has two chambers with a total of four on/off valves. Thus, there are sixteen possible combinations for valves' switching. Seven of these sixteen operating "modes" are considered both functional and unique. The proposed sliding control utilizes and switches between these seven modes of the open-loop system in order to select the ones with necessary and sufficient amounts of drive energy. In comparing the new 7-mode controller to the previous controllers, we will demonstrate reductions in the position tracking error and the number of switches made by the actuator's on/off valves. The proposed control scheme is used in both position control of a pneumatic cylinder and bilateral control of a one degree of freedom teleoperation system. Experimental results are presented to validate our theoretical findings.

International audience; A nonlinear visual servoing approach is proposed for the stabilisation of fully-actuated autonomous underwater vehicles (AUVs) by exploiting the homography matrix between the two images of a planar scene. In a cascade manner, an outer-loop control defines a reference setpoint based on the homography matrix, and an inner-loop control ensures the stabilisation of the setpoint by assigning thrust and torque controls. In contrast with conventional kinematic solution, the proposed controller deals with the high nonlinearity and coupling of the system dynamics and ensures almost-global asymptotical stability. In addition, the interactions of the AUV with the surrounding fluid (e.g., added mass and drag effects) are often difficult to model precisely whereas they may significantly perturb its motion. The proposed controller –augmented with an effective integral action– allows for the compensation of model uncertainties and for robust performance against such perturbations. Simulation results illustrating these properties on a realistic AUV model subject to sea current are reported.

ISBN : 978-2-9532965-0-1; Using computer-simulation experiments, we developed a vision-based autopilot that enables a ‘simulated bee' to travel along a tunnel by controlling both its speed and its clearance from the right wall, the left wall, the ground, and the ceiling. The flying agent can translate along three directions (surge, sway, and heave): the agent is therefore fully actuated. The visuo-motor control system, called ALIS (AutopiLot using an Insect based vision System), is a dual OF regulator consisting of two interdependent feedback loops, each of which has its own OF set-point. The experiments show that the simulated bee navigates safely along a straight tunnel, while reacting sensibly to the major OF perturbation caused by the presence of a tapered tunnel. The visual system is minimalistic (only eight pixels) and it suffices to control the clearance from the four walls and the forward speed jointly, without the need to measure any speeds and distances. The OF sensors and the simple visuo-motor control system developed here are suitable for use on MAVs with avionic payloads as small as a few grams. Besides, the ALIS autopilot accounts remarkably for the quantitative results of ethological experiments performed on honeybees flying freely in straight or tapered corridors.

The JASON remotely operated vehicle (ROV) system has been under development for the last decade. After a number of engineering test cruises, including the discovery of the R.M.S. Titanic and the German Battleship Bismarck, this ROV system is now being implemented in oceanographic investigations. This paper explains its development history and its unique ability to carry out a broad range of scientific research.