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Robots with whole-body sensitive skins
While for humans, touch is the first sense to develop and most of the time, we are barely aware of it, robots were lacking this sense until recently. Matej's group studies how robots can exploit large area sensitive skin arrays on their bodies. Robot skin can be instrumental in haptic exploration using whole-body contact (see below) or for in safe and effective human-robot interaction (see the Co-bots and physical HRI tab).
Bartunek, K., Rustler, L. and Hoffmann, M. (2026), No Need to Look! Locating and Grasping Objects by a Robot Arm Covered with Sensitive Skin, in 'IEEE International Conference on Robotics and Automation (ICRA)'. [to appear] [pdf-arxiv] [youtube-video]
Automatic self-contained robot calibration
Nowadays, humanoid but also other robots come with a rich set of powerful yet inexpensive sensors like cameras, RGB-D cameras, inertial, tactile or force sensors. This opens up the possibility for calibration approaches that are more “self-contained”, can be performed autonomously and repeatedly by the robot, and that simultaneously estimate the position of the sensors with respect to the robot. The robot model itself can be simultaneously calibrated as well.
We have demonstrated the potential of this approach on a number of robots and developed also a multisensorial robot calibration toolbox: https://github.com/ctu-vras/multirobot-calibration.
This invited entry to the Encyclopedia of Robotics provides an overview of the related work: Hoffmann, M. (2022), Biologically inspired robot body models and self-calibration, in Marcelo Ang; Oussama Khatib & Bruno Siciliano, ed., 'Encyclopedia of Robotics', Springer. [Springer][pdf - please find it as Appendix C, from pg. 80 in my habilitation thesis or send me an email]
The key to self-calibration is redundancy. The kinematic chain can be closed exploiting physical contact (aka closed-loop calibration approaches) or by observing the robot pose using visual sensors (open-loop calibration approaches). Next to traditional methods exploiting contact with the environment (e.g. robot touching a planar surface - panel (B) below) or external metrology systems (e.g. laser trackers - panel (D) below), we have added self-contact (panel A) and self-observation (panel C) as methods that are suited for automatic self-contained calibration.
We show how the different calibration approaches can be combined in a single cost function. Thorough experimental validation of the methods in isolation and in combination is shown on the iCub humanoid (left, self-touch and self-observation) and an industrial dual-arm manipulator (right, self-contact, self-observation, planar constraints, external laser tracker).
Stepanova, K.; Pajdla, T. & Hoffmann, M. (2019), 'Robot self-calibration using multiple kinematic chains – a simulation study on the iCub humanoid robot', IEEE Robotics and Automation Letters 4(2), 1900-1907. [IEEE Xplore] [publication webpage] [arxiv]
Stepanova, K.; Rozlivek, J.; Puciow, F.; Krsek, P.; Pajdla, T. & Hoffmann, M. (2022), 'Automatic self-contained calibration of an industrial dual-arm robot with cameras using self-contact, planar constraints, and self-observation', Robotics and Computer-Integrated Manufacturing 73, 102250. [DOI][Elsevier - OPEN ACCESS pdf]
Self-contact or self-touch can be employed in different ways. Contact can be exploited as a constraint (top right) or, if the robot is covered with sensitive skin, one can use the skin to calibrate the robot kinematics (bottom left), or, the robot kinematics can be used to spatially calibrate the skin (bottom right).
Roncone, A.; Hoffmann, M.; Pattacini, U. & Metta, G. (2014), Automatic kinematic chain calibration using artificial skin: self-touch in the iCub humanoid robot, in 'Robotics and Automation (ICRA), 2014 IEEE International Conference on', pp. 2305-2312. [IEEE Xplore] [postprint]
Rustler, L.; Potocna, B.; Polic, M.; Stepanova, K. & Hoffmann, M. (2021), Spatial calibration of whole-body artificial skin on a humanoid robot: comparing self-contact, 3D reconstruction, and CAD-based calibration, in 'Humanoid Robots (Humanoids), IEEE-RAS International Conference on', pp. 445-452. [IEEE Xplore][preprint-pdf]
An overview of the multisensorial and multirobot calibration toolbox (https://github.com/ctu-vras/multirobot-calibration) is shown below.
Rozlivek, J.; Rustler, L.; Stepanova, K. & Hoffmann, M. (2021), Multisensorial robot calibration framework and toolbox, in 'Humanoid Robots (Humanoids), IEEE-RAS International Conference on', pp. 459-466. [IEEE Xplore][preprint-pdf]
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