[Show abstract][Hide abstract] ABSTRACT: We present a vision-based approach for navigation of humanoid robots in networks of corridors connected through curves and junctions. The objective of the humanoid is to follow the corridors, walking as close as possible to their center to maximize motion safety, and to turn at curves and junctions. Our control algorithm is inspired by a technique originally designed for unicycle robots that we have adapted to humanoid navigation and extended to cope with the presence of turns and junctions. In addition, we prove here that the corridor following control law provides asymptotic convergence of robot heading and position to the corridor bisector even when the corridor walls are not parallel. A state transition system is designed to allow navigation in mazes of corridors, curves and T-junctions. Extensive experimental validation proves the validity and robustness of the approach.
Full-text · Article · Jan 2016 · Autonomous Robots
[Show abstract][Hide abstract] ABSTRACT: We present a method for odometric localization of humanoid robots using standard sensing equipment, i.e., a monocular camera, an inertial measurement unit (IMU), joint encoders and foot pressure sensors. Data from all these sources are integrated using the prediction-correction paradigm of the Extended Kalman Filter. Position and orientation of the torso, defined as the representative body of the robot, are predicted through kinematic computations based on joint encoder readings; an asynchronous mechanism triggered by the pressure sensors is used to update the placement of the support foot. The correction step of the filter uses as measurements the torso orientation, provided by the IMU, and the head pose, reconstructed by a VSLAM algorithm. The proposed method is validated on the humanoid NAO through two sets of experiments: open-loop motions aimed at assessing the accuracy of localization with respect to a ground truth, and closed-loop motions where the humanoid pose estimates are used in real-time as feedback signals for trajectory control.
[Show abstract][Hide abstract] ABSTRACT: To achieve the complete car driving task with a humanoid robot, it is necessary to develop a set of basic action primitives, including: walking to the vehicle, manually controlling its commands (ignition, accelerator and steering), and moving with the whole-body, for car ingress/egress. In this paper, we propose an approach for realizing the central part of the complete task, consisting in driving the car along a road. The proposed method is composed of two main parts. First, a vision-based controller uses image features of the road, to provide the reference angle for the steering wheel. Second, an admittance controller allows the humanoid to safely rotate the steering wheel with its hands and realize the desired steering command. We present results from a car driving experience, by humanoid robot HRP-4, within a video game setup.
[Show abstract][Hide abstract] ABSTRACT: We address the problem of robustly tracking a desired workspace trajectory with a humanoid robot. The proposed solution is based on the suitable definition of a controlled output, which represents an averaged motion of the torso after cancellation of the sway oscillation. In particular, two different techniques are presented for extracting the averaged motion. For control design purposes, a unicycle-like model is associated to the evolution of this output. The feedback loop is then closed using a vision-based odometric localization method to estimate the torso motion. The proposed approach is validated through comparative experiments on the humanoid robot NAO.
[Show abstract][Hide abstract] ABSTRACT: This paper considers the problem of planning the motion of a humanoid robot that must execute a manipulation task, possibly requiring stepping, in environments cluttered by obstacles. The proposed method explores the submanifold of the configuration space that is admissible with respect to the assigned task and at the same time satisfies other constraints, including humanoid equilibrium. The exploration tree is expanded using a hybrid scheme that simultaneously generates footsteps and whole-body motions. The algorithm has been implemented for the humanoid robot NAO and validated through planning experiments and dynamic playback in V-REP.
[Show abstract][Hide abstract] ABSTRACT: In this paper we propose a method to perform manual guidance with humanoid robots. Manual guidance is a general model of physical interaction: here we focus on guiding a humanoid by its hands. The proposed technique can be, however, used also for joint object transportation and other tasks implying human-humanoid physical interaction. Using a measure of the Instantaneous Capture Point, we develop an equilibrium-based interaction technique that does not require force/torque or vision sensors. It is, therefore, particularly suitable for low-cost humanoids and toys. The proposed method has been experimentally validated on the small humanoid NAO.
No preview · Article · Sep 2014 · Proceedings - IEEE International Conference on Robotics and Automation
[Show abstract][Hide abstract] ABSTRACT: We consider the problem of planning the motion of redundant robotic systems subject to geometric task constraints in the presence of obstacles moving along known trajectories. Building on our previous results on task-constrained motion planning, we propose a control-based motion planner that works directly in the task-constrained configuration space extended with the time dimension. The generated trajectories are collision-free and satisfy the task constraint with arbitrary accuracy. Bounds on the achievable generalized velocities may also be taken into account. The proposed approach is validated through planning experiments on a 7-dof articulated robot and an 8-dof mobile manipulator.
[Show abstract][Hide abstract] ABSTRACT: We present a control-based approach for visual navigation of humanoid robots in office-like environments. In particular, the objective of the humanoid is to follow a maze of corridors, walking as close as possible to their center to maximize motion safety. Our control algorithm is inspired by a technique originally designed for unicycle robots and extended here to cope with the presence of turns and junctions. The feedback signals computed for the unicycle are transformed to inputs that are suited for the locomotion system of the humanoid, producing a natural, human-like behavior. Exper-imental results for the humanoid robot NAO are presented to show the validity of the approach, and in particular the successful extension of the controller to turns and junctions.
[Show abstract][Hide abstract] ABSTRACT: Minimally invasive surgery assisted by robots is characterized by the restriction of feasible motions of the manipulator link constrained to move through the entry port to the patient's body. In particular, the link is only allowed to translate along its axis and rotate about the entry point. This requires constraining the manipulator motion with respect to a point known as Remote Center of Motion (RCM). The achievement of any surgical task inside the patient's body must take into account this constraint. In this paper we provide a new, general characterization of the RCM constraint useful for task control in the minimally invasive robotic surgery context. To show the effectiveness of our formalization, we consider first a visual task for a manipulator with 6 degrees of freedom holding an endoscopic camera and derive the kinematic control law allowing to achieve the visual task while satisfying the RCM constraint. An example of application of the proposed kinematic modeling to a motion planning problem for a 9 degrees of freedom manipulator with assigned path for the surgical tool is then proposed to illustrate the generality of the approach.
[Show abstract][Hide abstract] ABSTRACT: We consider motion planning in the presence of obstacles for redundant robotic systems subject to repetitive task constraints. For this open problem, we present a novel control-based randomized planner which produces cyclic, collision-free paths in configuration space and guarantees continuous satisfaction of the task constraints. In particular, the proposed algorithm relies on bidirectional search and loop closure in the task-constrained configuration space. Planning experiments on a simple 3R planar robot and the KUKA LWR-IV 7-dof manipulator are reported to show the effectiveness of the proposed method.
[Show abstract][Hide abstract] ABSTRACT: We propose an odometric system for localizing a walking humanoid robot using standard sensory equipment, i.e., a camera, an Inertial Measurement Unit, joint encoders and foot pressure sensors. Our method has the prediction-correction structure of an Extended Kalman Filter. At each sampling instant, position and orientation of the torso are predicted on the basis of the differential kinematic map from the support foot to the torso, using encoder data from the support joints. The actual measurements coming from the camera (head position and orientation reconstructed by a V-SLAM algorithm) and the Inertial Measurement Unit (torso orientation) are then compared with their predicted values to correct the estimate. The filter is made aware of the current placement of the support foot by an asynchronous update mechanism triggered by the pressure sensors. An experimental validation on the humanoid NAO shows the satisfactory performance of the proposed method.
[Show abstract][Hide abstract] ABSTRACT: This paper addresses the path following problem for an autonomous parafoil-payload system. The actuated dynamics of the system is first detailed. Local exponential stability of an input-output feedback linearizing control is proved, achieving a stable line following in the XY plane by using only lateral directional control input.
[Show abstract][Hide abstract] ABSTRACT: This report describes a preliminary study on modeling and control of parafoil and payload systems with the twofold objective of developing tools for automatic testing and classification of parafoils and of devising autonomous paragliders able to accomplish long-range delivery or monitoring tasks. Three different models of decreasing complexity are derived and their accuracy compared by simulation.
[Show abstract][Hide abstract] ABSTRACT: Paragliders represent a light, low cost, space efficient means for autonomous transportation. They can be used for accurate delivering of payloads using inexpensive guidance and control modules. If equipped with proper sensor, it is possible to use paragliders for scientific observation during flight, such as chemical, thermal, meteorological, or biological analyses of the atmosphere. Aerial remote sensing of the surface can also be carried out, obtaining high-resolution imaging, measurements of seismic activity, and more generally collecting data on dangerous or inaccessible areas. Since they are inexpensive, light and versatile, they are interesting for planetary exploration, in particular if Mars, Venus, Titan and the Outer Planets are considered because of their atmosphere. The aim of the paper is to have a preliminary study of the behavior of a paraglider flying through the atmosphere of a planet. A scalability analysis to compare performance with results obtained when flying over Earth will be carried out, highlighting that at steady state all coordinates but the norm of velocity reach the same equilibrium point. A ratio between the velocity over the planet and over Earth will be derived as function of the gravitational acceleration and the atmosphere density. Finally, the performance of a line following algorithm developed in a previous work will be evaluated through simulations on Mars.
[Show abstract][Hide abstract] ABSTRACT: We consider the problem of planning collision-free motions for general (i.e., possibly nonholonomic) redundant robots subject to task space constraints. Previous approaches to the solution are based on the idea of sampling and inverting the task constraint to build a roadmap of task-constrained configurations which are then connected by simple local paths; hence, task tracking is not enforced during the motion between samples. Here, we present a control-based randomized approach relying on a motion generation scheme that guarantees continued satisfaction of such constraint. The resulting planner allows to achieve accurate execution of the desired task without increasing the size of the roadmap. Numerical results on a fixed-base manipulator and a free-fying mobile manipulator are presented to illustrate the performance improvement obtained with the proposed technique.
[Show abstract][Hide abstract] ABSTRACT: In this paper, we characterize the time-optimal trajectories leading a Dubins car in collision with the obstacles in its workspace. Due to the constant velocity constraint characterizing the Dubins car model, these trajectories form a sufficient set of shortest paths between any robot configuration and the obstacles in the environment. Based on these paths, we define and give the algorithm for computing a distance function that takes into account the nonholonomic constraints and captures the nonsymmetric nature of the system. The developments presented here assume that the obstacles and the robot are polygons although the methodology can be applied to different shapes.
Full-text · Article · Nov 2009 · IEEE Transactions on Robotics
[Show abstract][Hide abstract] ABSTRACT: We present a decentralized cooperative exploration strategy for a team of mobile robots equipped with range finders. A roadmap of the explored area, with the associate safe region, is built in the form of a sensor-based random graph (SRG). This is expanded by the robots by using a randomized local planner that automatically realizes a tradeoff between information gain and navigation cost. The nodes of the SRG represent view configurations that have been visited by at least one robot, and are connected by arcs that represent safe paths. These paths have been actually traveled by the robots or added to the SRG to improve its connectivity. Decentralized cooperation and coordination mechanisms are used so as to guarantee exploration efficiency and avoid conflicts. Simulations and experiments are presented to show the performance of the proposed technique.
Full-text · Article · May 2009 · IEEE/ASME Transactions on Mechatronics
[Show abstract][Hide abstract] ABSTRACT: We consider the problem of planning collision-free motions for gen-eral (i.e., possibly nonholonomic) redundant robots subject to task space constraints. Previous approaches to the solution are based on the idea of sampling and inverting the task constraint to build a roadmap of task-constrained configurations which are then connected by simple local paths; hence, task tracking is not enforced during the motion between samples. Here, we present a kinodynamic approach based on a motion generation scheme that guarantees continued satisfaction of such constraint. The resulting randomized planner allows to achieve accurate execution of the desired task without increasing the complex-ity of the roadmap. Numerical results on a fixed-base manipulator and a free-fying mobile manipulator are presented to illustrate the perfor-mance improvement obtained with the proposed technique.