Video Friday: Robot Toes, Wolverine Haptic Hand, and More From IROS 2016

Kengoro humanoid with robotic toes
Image: University of Tokyo

This week we continue with our selection of awesome robot videos from IROS, which took place last week in South Korea. We’re posting the vids along with the titles, authors, and abstracts of their respective papers. If you have questions about these projects, let us know and we’ll try to get more details from the researchers.

As a reminder, we’ll return to normal Video Friday next week, so if you have video suggestions for us, send us an email or reach us on Twitter or Facebook. Enjoy Video Friday IROS 2016 Part 2!


"Human Mimetic Foot Structure With Multi-DOFs and Multi-Sensors for Musculoskeletal Humanoids," by Yuki Asano, Shinsuke Nakashima, Toyotaka Kozuki, Soichi Ookubo, Ioi Yanokura, Youhei Kakiuchi, Kei Okada, and Masayuki Inaba from the University of Tokyo.

We propose a human mimetic foot structure for musculoskeletal humanoids. We designed the foot structure by inspiring from human foot abilities of the multi-bone connected structure for flexibility and the distributed force sensor system. The foot has multi-DOFs structure including toe DOF that is composed of fingers, The distributed force sensing system is composed of 12 an axis force sensors. In order to demonstrate those effectiveness, we implement the foot into musculoskeletal humanoid Kengoro and conduct several experiments. As a result, we confirmed effectiveness of the foot from tiptoe motion and balancing behavior by utilizing the foot characteristics.


"Frontal Plane Stabilization and Hopping with a 2 DOF Tail," by Garrett Wenger, Avik De, and Daniel E. Koditschek from the University of Pennsylvania.

The Jerboa, a tailed bipedal robot with two hip-actuated, passive-compliant legs and a doubly actuated tail, has been shown both formally and empirically to exhibit a variety of stable hopping and running gaits in the sagittal plane. In this paper we take the first steps toward operating Jerboa as a fully spatial machine by addressing the predominant mode of destabilization away from the sagittal plane: body roll. We develop a provably stable controller for underactuated aerial stabilization of the coupled body roll and tail angles, that uses just the tail torques. We show that this controller is successful at reliably reorienting the Jerboa body in roughly 150 ms of freefall from a large set of initial conditions. This controller also enables (and, indeed, appears intuitively to be crucial for) sustained empirically stable hopping in the frontal plane by virtue of its substantial robustness against destabilizing perturbations and calibration errors. The controller as well as the analysis methods developed here are applicable to any robotic platform with a similar doubly-actuated spherical tail joint.


"Wolverine: A Wearable Haptic Interface for Grasping in Virtual Reality," by Inrak Choi, Elliot W. Hawkes, David L. Christensen, Christopher J. Ploch, and Sean Follmer from Stanford University.

The Wolverine is a mobile, wearable haptic device designed for simulating the grasping of rigid objects in a virtual reality interface. In contrast to prior work on wearable force feedback gloves, we focus on creating a low cost and lightweight device that renders a force directly between the thumb and three fingers to simulate objects held in pad opposition (precision) type grasps. Leveraging low-power brake-based locking sliders, the system can withstand over 100N of force between each finger and the thumb, and only consumes 0.24 mWh (0.87 joules) for each braking interaction. Integrated sensors are used both for feedback control and user input: time-of-flight sensors provide the position of each finger and an IMU provides overall orientation tracking. This paper describes the mechanical design, control strategy, and performance analysis of the Wolverine system and provides a comparison with several existing wearable haptic devices.​


"Multi-Contact Planning and Control for a Torque-Controlled Humanoid Robot," by Alexander Werner, Bernd Henze, Diego A. Rodriguez, Jonathan Gabaret, Oliver Porges, and Maximo A. Roa from the Institute of Robotics and Mechatronics, German Aerospace Center (DLR).

Humanoid robots that need to traverse constrained and uncertain environments require a suitable combination of perception, planning and con- trol. This paper presents an integrated pipeline that allows the robot to autonomously acquire visual infor- mation, define step locations, compute feasible multi- contact situations using hands and feet, and generate a motion plan to reach the desired goal even going through different contact states. The execution of the desired path is guaranteed though an optimization- based multi-contact controller. The approach is eval- uated in simulations and experiments in two different scenarios using the humanoid robot TORO.


"Design and Characterization of the EP-Face Connector," by Tarik Tosun, Jay Davey, Chao Liu, and Mark Yim from the University of Pennsylvania and Transcriptic, in Menlo Park, Calif.

We present the EP-Face connector, a novel con- nector for hybrid chain-lattice type modular robots that is high- strength (88.4N), compact, fast, power efficient, and robust to position errors.The connector consists of an array of electro-permanent magnets (EP magnets) embedded in a planar face. EP magnets are solid-state magnets that can be turned on and off and require power only when changing state.In this paper, we present the design of the connector, man- ufacturing process, detailed experimental characterization of the connector strength under different loading conditions, and compare its performance to existing magnetic and mechanical connectors. We also illustrate the functional benefits of the EP- Face by demonstrating reconfiguration with the SMORES-EP robot.


"Collaborative Navigation for Flying and Walking Robots," by Peter Fankhauser, Michael Bloesch, Philipp Krusi, Remo Diethelm, Martin Wermelinger, Thomas Schneider, Marcin Dymczyk, Marco Hutter, and Roland Siegwart from the Autonomous Systems Lab, ETH Zurich, Switzerland.

Flying and walking robots can use their complementary features in terms of viewpoint and payload capability to the best in a heterogeneous team. To this end, we present our online collaborative navigation framework for unknown and challenging terrain. The method leverages the flying robot’s onboard monocular camera to create both a map of visual features for simultaneous localization and mapping and a dense representation of the environment as an elevation map. This shared knowledge from the flying platform enables the walking robot to localize itself against the global map, and plan a global path to the goal by interpreting the elevation map in terms of traversability. While following the planned path, the absolute pose corrections are fused with the legged state estimation and the ele- vation map is continuously updated with distance measurements from an onboard laser range sensor. This allows the legged robot to safely navigate towards the goal while taking into account any changes in the environment. The presented methods are fully integrated and we demonstrate their capabilities in an experiment with a hexacopter and a quadrupedal robot.​


"Printable Programmable Viscoelastic Materials for Robots," by Robert MacCurdy, Jeffrey Lipton, Shuguang, Li and Daniela Rus from MIT.

Impact protection and vibration isolation are an important component of the mobile robot designer’s toolkit; however, current damping materials are available only in bulk or molded form, requiring manual fabrication steps and restricting material property control. In this paper we demonstrate a new method for 3D printing viscoelastic materials with specified mate- rial properties. This method allows arbitrary net-shape material geometries to be rapidly fabricated and enables continuously varying material properties throughout the finished part. This new ability allows robot designers to tailor the properties of viscoelastic damping materials in order to reduce impact forces and isolate vibrations. We present a case study for using this material to create robots with programmed levels of bouncing.​


"Synergy-based Policy Improvement with Path Integrals for Anthropomorphic Hands," by Fanny Ficuciello, Damiano Zaccara, Bruno Siciliano from the Universita degli Studi di Napoli Federico II.

In this work, a synergy-based reinforcement learn- ing algorithm has been developed to confer autonomous grasp- ing capabilities to anthropomorphic hands. In the presence of high degrees of freedom, classical machine learning techniques require a number of iterations that increases with the size of the problem, thus convergence of the solution is not ensured. The use of postural synergies determines dimensionality reduction of the search space and allows recent learning techniques, such as Policy Improvement with Path Integrals (PI2), becoming easily applicable. A key point is the adoption of a suitable reward function representing the goal of the task and ensuring one- step performance evaluation. As a cost function, force closure quality of the grasp in the synergies subspace has been chosen. The experiments conducted on the SCHUNK 5-Finger Hand demonstrate the effectiveness of the algorithm showing skills comparable to human capabilities in learning new grasps and in performing wide variety from power to high precision grasps of very small objects.​


"The Flying Anemometer: Unified Estimation of Wind Velocity from Aerodynamic Power and Wrenches," by Teodor Tomic, Korbinian Schmid, Philipp Lutz, Andrew Mathers, and Sami Haddadin from the German Aerospace Center (DLR), Roboception GmbH in Munich, Germany, WindEEE Research Institute in London, Ontario, Canada, and Leibniz Universitat Hannover.

We consider the problem of estimating the wind velocity perceived by a flying multicopter, from data acquired by onboard sensors and knowledge of its aerodynamics model only. We employ two complementary methods. The first is based on the estimation of the external wrench due to aerodynamics acting on the robot in flight. Wind velocity is obtained by inverting an identified model of the aerodynamic forces. The second method is based on the estimation of the propeller aerodynamic power, and provides an estimate independent of other sensors. We show how to calculate components of the wind velocity using multiple aerodynamic power measurements, when the poses between them are known. The method uses the motor current and angular velocity as measured by the elec- tronic speed controllers, essentially using the propellers as wind sensors. Verification of the methods and model identification were done using measurements acquired during autonomous flights in a 3D wind tunnel.​


"Development of a Spherical Tether Handling Device with a Coupled Differential Mechanism for Tethered Teleoperated Robots," by Tomoya Ichimura, Kenjiro Tadakuma, Eri Takane, Masashi Konyo, and Satoshi Tadokoro from Tohoku University.

Tethered robots often face the entangling of the cable with obstacles in uncertain disaster environments. This paper proposes a spherical tether handling device that unfastens a robot’s tether during surveys by releasing the tether and carrying it aside. The device drives the shells and rollers, that hold the tether, using a differential mechanism. On flat surfaces, the device moves forward by driving the shells. When the device climbs over steps, the rollers are driven by the differential mechanism to pull the tether automatically. After prototyping the device, we confirm the surmountability of the proposed device against the steps and gaps. The results show that the device can climb a height of 90.9% of its diameter. We also demonstrate a scenario to handle the tether and untangle multiple tangles in an environment with several obstacles.​


"Permanent Magnet-Assisted Omnidirectional Ball Drive," by Ayberk Ozgur, Wafa Johal, and Pierre Dillenbourg from the Computer-Human Interaction in Learning and Instruction Laboratory at EPFL, in Lausanne, Switzerland.

We present an omnidirectional ball wheel drive design that utilizes a permanent magnet as the drive roller to generate the contact force. Particularly interesting for novel human-mobile robot interaction scenarios where the users are expected to physically interact with many palm-sized robots, our design combines simplicity, low cost and compactness. We first detail our design and explain its key parameters. Then, we present our implementation and compare it with an omniwheel drive built with identical conditions and similar cost. Finally, we elaborate on main advantages and drawbacks of our design.​


"Decoupled Design of Controllers for Aerial Manipulation with Quadrotors," by Pedro O. Pereira, Riccardo Zanella and Dimos V. Dimarogonas from KTH Royal Institute of Technology, in Stockholm, Sweden.

In this paper, we model an aerial vehicle, specif- ically a quadrotor, and a load attached to each other by a rigid link. We assume a torque input at the joint between the aerial vehicle and the rigid link is available. After modeling, we decouple the system dynamics in two separate subsystems, one concerning the position of the center of mass, which we control independently from the chosen torque input; and a second subsystem, concerning the attitude of the rigid link, which we control by appropriately designing a torque control law. Differential flatness is used to show that controlling these two separate systems is equivalent to controlling the complete system. We design control laws for the quadrotor thrust, the quadrotor angular velocity and the torque input, and provide convergence proofs that guarantee that the quadrotor follows asymptotically a desired position trajectory while the manipu- lator follows a desired orientation. Simulation and experimental works are presented which validate the proposed algorithms.​


"Soft Robotics for the Hydraulic Atlas Arms: Joint Impedance Control with Collision Detection and Disturbance Compensation," by Jonathan Vorndamme, Moritz Schappler, Alexander Todtheide, and Sami Haddadin from the Institute of Automatic Control at Leibniz Universitat Hannover, Germany.

Soft robotics methods such as impedance control and reflexive collision handling have proven to be a valuable tool to robots acting in partially unknown and potentially unstruc- tured environments. Mainly, the schemes were developed with focus on classical electromechanically driven, torque controlled robots. There, joint friction, mostly coming from high gear- ing, is typically decoupled from link-side control via suitable rigid or elastic joint torque feedback. Extending and applying these algorithms to stiff hydraulically actuated robots poses problems regarding the strong influence of friction on joint torque estimation from pressure sensing, i.e. link-side friction is typically significantly higher than in electromechanical soft robots. In order to improve the performance of such systems, we apply state-of-the-art fault detection and estimation methods together with observer-based disturbance compensation control to the humanoid robot Atlas. With this it is possible to achieve higher tracking accuracy despite facing significant modeling errors. Compliant end-effector behavior can also be ensured by including an additional force/torque sensor into the generalized momentum-based disturbance observer algorithm from [1].


"Mass Control of Pneumatic Soft Continuum Actuators with Commodity Components," by Raphael Deimel, Marcel Radke, and Oliver Brock from the Robotics and Biology Laboratory, Technische Universitat Berlin, Germany.

Compliant actuation is the dominant paradigm for soft hands. We argue that to fully leverage the compliance available in soft pneumatic actuators, they should be controlled using air mass rather than position or force, as is customary in most soft robotics research. We propose an air-mass controller that enables setting a preset position, as in position control, but allows for the exploitation of fast, mechanical compliance without additional control burden. The proposed mass control scheme is based on discrete commodity valves and pressure sensors, filling a gap in available mass control systems for small- scale soft continuum actuators. The mass controller exhibits low drift for mass trajectories tens of seconds in duration, without requiring a precise model of the actuator. Continuous mass control opens up new applications for soft robotics in which compliance is of central importance.​


"Space CoBot: Modular Design of an Holonomic Aerial Robot for Indoor Microgravity Environments," by Pedro Roque and Rodrigo Ventura from the Universidade de Lisboa, Portugal. 

This paper presents the design of a small aerial robot for inhabited microgravity environments, such as orbiting space stations (e.g., ISS). In particular, we target a fleet of robots, called Space CoBots, for collaborative tasks with humans, such as telepresence and cooperative mobile manip- ulation. The design is modular, comprising an hexrotor based propulsion system, and a stack of modules including batteries, cameras for navigation, a screen for telepresence, a robotic arm, space for extension modules, and a pair of docking ports. These ports can be used for docking and for mechanically attaching two Space CoBots together. The kinematics is holonomic, and thus the translational and the rotational components can be fully decoupled. We employ a multi-criteria optimization approach to determine the best geometric configuration for maximum thrust and torque across all directions. We also tackle the problem of motion control: we use separate converging controllers for position and attitude control. Finally, we present simulation results using a realistic physics simulator. These experiments include a sensitivity evaluation to sensor noise and to unmodeled dynamics, namely a load transportation.​


"Toward Autonomous Aircraft Piloting by a Humanoid Robot: Hardware and Control Algorithm Design," by Hanjun Song, Heemin Shin, Haram You, and David Hyunchul Shim from KAIST, South Korea.

Although unmanned aerial vehicle technology remains as the subject of extensive research, application of this technology to existing aircraft is impossible without changes to required hardware and software. In this paper, an unmanned system in which a humanoid robot acts as the pilot is proposed for use in converting existing aircraft into unmanned aircraft with minimal modifications. A humanoid robot that can operate an aircraft autonomously can not only allow existing aircraft to operate unmanned but also carry out specific tasks in place of humans in a human-serving environment. This paper presents the results of a flight simulation conducted to verify the feasibility of humanoid robot operation of an aircraft.​


"Locomotion and Gait Analysis of Multi-Limb Soft Robots Based on Smart Actuators," by Shixin Mao, Erbao Dong, Hu Jin, Min Xu, K.H. Low from the University of Science and Technology of China, Hefei, China, and Nanyang Technological University, Singapore.

Soft animals provide various inspirations for developing soft machines in bionics, robotics research as well as potential applications. This paper presents an integrated development of locomotive soft robot platforms: starfish-inspired robots with multi-limb bodies actuated by shape memory alloys (SMAs). The designs of these robots were based on the biological specifications of the locomotion and water-vascular systems of regenerating starfish. Multi-limb robot prototypes were fabricated with soft materials and 3D printing technology, satisfying modest movement requirements with SMA spring actuators. Experimental trials of multi-limb robots were conducted in accordance with biological locomotion principles, and the robots vividly displayed typical starfish motion models. The locomotion of live starfish with different limb numbers suggests that, a correlation exists between movement and geometrical characteristics (e.g., body size) and such a correlation was also observed in the robot prototypes.​


"Position-Force Combination Control with Passive Flexibility for Versatile In-Hand Manipulation Based on Posture Interpolation," by Keung Or, Mami Tomura, Alexander Schmitz, Satoshi Funabashi, and Shigeki Sugano from Waseda University, Japan.

In-hand manipulation is needed to accomplish a practical task after grasping an object. In-hand manipulation of variously sized and shaped objects in multi-fingered hands without dropping the object is challenging. In this paper we suggest a combined strategy of force control and passive adap- tation through soft fingertips with simple interpolation control to achieve in-hand manipulation between various postures and with various objects. While passive compliance can be achieved in numerous ways, this paper uses soft skin, as it does not require complex mechanisms and was easy to integrate in the robot hand (Allegro hand). Softness has proven to significantly ease object grasping, and the current paper shows the importance of soft- ness also for in-hand manipulation. In particular, the simple interpolation strategy between various postures is successful when combined with soft fingertips, with or without force con- trol, but fails with hard fingertips. Objects of varying size, shape and hardness were manipulated. While the soft fingertips ena- bled good results in our experiments, a sufficiently precise defi- nition of the postures and object size is required. When com- bining the interpolation control with a force control strategy, bigger errors in defining the posture and object size are possible, without deforming or dropping the object, and the resultant force is lower. As a result, we achieved robust in-hand manipu- lation between various postures and with objects of different size, shape and hardness.

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