To precisely reach for an object with a humanoid robot, it is of central importance to have good knowledge of both end-effector, object pose and shape. In this work we propose a framework for markerless visual servoing on unknown objects, which is divided in four main parts: I) a leastsquares minimization problem is formulated to find the volume of the object graspable by the robot's hand using its stereo vision; II) a recursive Bayesian filtering technique, based on Sequential Monte Carlo (SMC) filtering, estimates the 6D pose (position and orientation) of the robot's end-effector without the use of markers; III) a nonlinear constrained optimization problem is formulated to compute the desired graspable pose about the object; IV) an image-based visual servo control commands the robot's end-effector toward the desired pose. We demonstrate effectiveness and robustness of our approach with extensive experiments on the iCub humanoid robot platform, achieving real-time computation, smooth trajectories and subpixel precisions.

This paper proposes an object modeling and grasping pipeline for humanoid robots. This work improves our previous approach based on superquadric functions. In particular, we speed up and refine the modeling process by using prior information on the object shape provided by an object classifier. We use our previous method for the computation of grasping pose to obtain pose candidates for both the robot hands and, then, we automatically choose the best candidate for grasping the object according to a given quality index. The performance of our pipeline has been assessed on a real robotic system, the iCub humanoid robot. The robot can grasp 18 objects of the YCB and iCub World datasets considerably different in terms of shape and dimensions with a high success rate.

This paper addresses the problem of grasping unknown objects with a humanoid robot. Conventional approaches fail when the shape, dimension or pose of the objects are missing. We propose a novel approach in which the grasping problem is solved by modeling the object and the volume graspable by the hand with superquadric functions. The object model is computed in real-time using stereo vision. Pose computation is formulated as a nonlinear constrained optimization problem, which is solved in real-time using the Ipopt software package. Notably, our method finds solutions in which the fingers are located on portions of the object that are occluded by vision. The performance of our approach has been assessed on a real robotic system, the iCub humanoid robot. The experiments show that the proposed method computes proper poses, suitable for grasping even small objects, while avoiding hitting the table with the fingers.

This paper addresses 6-DOF (degree-of-freedom) tactile localization, i.e., the pose estimation of tridimensional objects using tactile measurements. This estimation problem is fundamental for the operation of autonomous robots that are often required to manipulate and grasp objects whose pose is a priori unknown. The nature of tactile measurements, the strict time requirements for real-time operation, and the multimodality of the involved probability distributions pose remarkable challenges and call for advanced nonlinear filtering techniques. Following a Bayesian approach, this paper proposes a novel and effective algorithm, named memory unscented particle filter (MUPF), which solves 6-DOF localization recursively in real time by only exploiting contact point measurements. The MUPF combines a modified particle filter that incorporates a sliding memory of past measurements to better handle multimodal distributions, along with the unscented Kalman filter that moves the particles toward regions of the search space that are more likely with the measurements. The performance of the proposed MUPF algorithm has been assessed both in simulation and on a real robotic system equipped with tactile sensors (i.e., the iCub humanoid robot). The experiments show that the algorithm provides accurate and reliable localization even with a low number of particles and, hence, is compatible with real-time requirements.