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2015


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Real-Time Object Detection, Localization and Verification for Fast Robotic Depalletizing

Holz, D., Topalidou-Kyniazopoulou, A., Stueckler, J., Behnke, S.

In IEEE International Conference on Intelligent Robots and Systems (IROS), 2015 (inproceedings)

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link (url) [BibTex]

2015


link (url) [BibTex]


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Dense Continuous-Time Tracking and Mapping with Rolling Shutter RGB-D Cameras

Kerl, C., Stueckler, J., Cremers, D.

In IEEE International Conference on Computer Vision (ICCV), Santiago, Chile, 2015, {[video][supplementary][datasets]} (inproceedings)

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[BibTex]

[BibTex]


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Perception of Deformable Objects and Compliant Manipulation for Service Robots

Stueckler, J., Behnke, S.

In Soft Robotics: From Theory to Applications, Springer, 2015 (inbook)

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link (url) [BibTex]

link (url) [BibTex]


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Large-Scale Direct SLAM with Stereo Cameras

Engel, J., Stueckler, J., Cremers, D.

In IEEE International Conference on Intelligent Robots and Systems (IROS), 2015 (inproceedings)

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[BibTex]

[BibTex]


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Exciting Engineered Passive Dynamics in a Bipedal Robot

Renjewski, D., Spröwitz, A., Peekema, A., Jones, M., Hurst, J.

{IEEE Transactions on Robotics and Automation}, 31(5):1244-1251, IEEE, New York, NY, 2015 (article)

Abstract
A common approach in designing legged robots is to build fully actuated machines and control the machine dynamics entirely in soft- ware, carefully avoiding impacts and expending a lot of energy. However, these machines are outperformed by their human and animal counterparts. Animals achieve their impressive agility, efficiency, and robustness through a close integration of passive dynamics, implemented through mechanical components, and neural control. Robots can benefit from this same integrated approach, but a strong theoretical framework is required to design the passive dynamics of a machine and exploit them for control. For this framework, we use a bipedal spring–mass model, which has been shown to approximate the dynamics of human locomotion. This paper reports the first implementation of spring–mass walking on a bipedal robot. We present the use of template dynamics as a control objective exploiting the engineered passive spring–mass dynamics of the ATRIAS robot. The results highlight the benefits of combining passive dynamics with dynamics-based control and open up a library of spring–mass model-based control strategies for dynamic gait control of robots.

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link (url) DOI Project Page [BibTex]

link (url) DOI Project Page [BibTex]


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Comparing the effect of different spine and leg designs for a small bounding quadruped robot

Eckert, P., Spröwitz, A., Witte, H., Ijspeert, A. J.

In Proceedings of ICRA, pages: 3128-3133, Seattle, Washington, USA, 2015 (inproceedings)

Abstract
We present Lynx-robot, a quadruped, modular, compliant machine. It alternately features a directly actuated, single-joint spine design, or an actively supported, passive compliant, multi-joint spine configuration. Both spine con- figurations bend in the sagittal plane. This study aims at characterizing these two, largely different spine concepts, for a bounding gait of a robot with a three segmented, pantograph leg design. An earlier, similar-sized, bounding, quadruped robot named Bobcat with a two-segment leg design and a directly actuated, single-joint spine design serves as a comparison robot, to study and compare the effect of the leg design on speed, while keeping the spine design fixed. Both proposed spine designs (single rotatory and active and multi-joint compliant) reach moderate, self-stable speeds.

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link (url) DOI Project Page [BibTex]

link (url) DOI Project Page [BibTex]


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Efficient Dense Rigid-Body Motion Segmentation and Estimation in RGB-D Video

Stueckler, J., Behnke, S.

International Journal of Computer Vision (IJCV), 113(3):233-245, 2015 (article)

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


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Motion Cooperation: Smooth Piece-Wise Rigid Scene Flow from RGB-D Images

Jaimez, M., Souiai, M., Stueckler, J., Gonzalez-Jimenez, J., Cremers, D.

In Proc. of the Int. Conference on 3D Vision (3DV), October 2015, {[video]} (inproceedings)

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[BibTex]

[BibTex]


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Super-Resolution Keyframe Fusion for 3D Modeling with High-Quality Textures

Maier, R., Stueckler, J., Cremers, D.

In International Conference on 3D Vision (3DV), October 2015, {[slides] [poster]} (inproceedings)

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[BibTex]

[BibTex]


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Reconstructing Street-Scenes in Real-Time From a Driving Car

Usenko, V., Engel, J., Stueckler, J., Cremers, D.

In Proc. of the Int. Conference on 3D Vision (3DV), October 2015 (inproceedings)

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[BibTex]

[BibTex]

2013


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Benefits of an active spine supported bounding locomotion with a small compliant quadruped robot

Khoramshahi, M., Spröwitz, A., Tuleu, A., Ahmadabadi, M. N., Ijspeert, A. J.

In Robotics and Automation (ICRA), 2013 IEEE International Conference on, pages: 3329-3334, May 2013 (inproceedings)

Abstract
We studied the effect of the control of an active spine versus a fixed spine, on a quadruped robot running in bound gait. Active spine supported actuation led to faster locomotion, with less foot sliding on the ground, and a higher stability to go straight forward. However, we did no observe an improvement of cost of transport of the spine-actuated, faster robot system compared to the rigid spine.

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Youtube DOI Project Page [BibTex]

2013


Youtube DOI Project Page [BibTex]


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Central pattern generators augmented with virtual model control for quadruped rough terrain locomotion

Ajallooeian, M., Pouya, S., Spröwitz, A., Ijspeert, A. J.

In Proceedings of the 2013 IEEE International Conference on Robotics and Automation (ICRA), pages: 3321-3328, IEEE, Karlsruhe, 2013 (inproceedings)

Abstract
We present a modular controller for quadruped locomotion over unperceived rough terrain. Our approach is based on a computational Central Pattern Generator (CPG) model implemented as coupled nonlinear oscillators. Stumbling correction reflex is implemented as a sensory feedback mechanism affecting the CPG. We augment the outputs of the CPG with virtual model control torques responsible for posture control. The control strategy is validated on a 3D forward dynamics simulated quadruped robot platform of about the size and weight of a cat. To demonstrate the capabilities of the proposed approach, we perform locomotion over unperceived uneven terrain and slopes, as well as situations facing external pushes.

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DOI [BibTex]

DOI [BibTex]


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Motor Control Adaptation to Changes in Robot Body Dynamics for a Compliant Quadruped Robot

Pouya, S., Eckert, P., Spröwitz, A., Moc̈kel, R., Ijspeert, A. J.

In Biomimetic and Biohybrid Systems, 8064, pages: 434-437, Lecture Notes in Computer Science, Springer, Heidelberg, 2013 (incollection)

Abstract
One of the major deficiencies of current robots in comparison to living beings is the ability to adapt to new conditions either resulting from environmental changes or their own dynamics. In this work we focus on situations where the robot experiences involuntary changes in its body particularly in its limbs’ inertia. Inspired from its biological counterparts we are interested in enabling the robot to adapt its motor control to the new system dynamics. To reach this goal, we propose two different control strategies and compare their performance when handling these modifications. Our results show substantial improvements in adaptivity to body changes when the robot is aware of its new dynamics and can exploit this knowledge in synthesising new motor control.

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DOI [BibTex]

DOI [BibTex]


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Towards Dynamic Trot Gait Locomotion: Design, Control, and Experiments with Cheetah-cub, a Compliant Quadruped Robot

Spröwitz, A., Tuleu, A., Vespignani, M., Ajallooeian, M., Badri, E., Ijspeert, A. J.

{The International Journal of Robotics Research}, 32(8):932-950, Sage Publications, Inc., Cambridge, MA, 2013 (article)

Abstract
We present the design of a novel compliant quadruped robot, called Cheetah-cub, and a series of locomotion experiments with fast trotting gaits. The robot’s leg configuration is based on a spring-loaded, pantograph mechanism with multiple segments. A dedicated open-loop locomotion controller was derived and implemented. Experiments were run in simulation and in hardware on flat terrain and with a step down, demonstrating the robot’s self-stabilizing properties. The robot reached a running trot with short flight phases with a maximum Froude number of FR = 1.30, or 6.9 body lengths per second. Morphological parameters such as the leg design also played a role. By adding distal in-series elasticity, self- stability and maximum robot speed improved. Our robot has several advantages, especially when compared with larger and stiffer quadruped robot designs. (1) It is, to the best of the authors’ knowledge, the fastest of all quadruped robots below 30 kg (in terms of Froude number and body lengths per second). (2) It shows self-stabilizing behavior over a large range of speeds with open-loop control. (3) It is lightweight, compact, and electrically powered. (4) It is cheap, easy to reproduce, robust, and safe to handle. This makes it an excellent tool for research of multi-segment legs in quadruped robots.

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Youtube1 Youtube2 Youtube3 Youtube4 Youtube5 DOI Project Page [BibTex]

Youtube1 Youtube2 Youtube3 Youtube4 Youtube5 DOI Project Page [BibTex]


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Gait Optimization for Roombots Modular Robots - Matching Simulation and Reality

Möckel, R., Yura, N. P., The Nguyen, A., Vespignani, M., Bonardi, S., Pouya, S., Spröwitz, A., van den Kieboom, J., Wilhelm, F., Ijspeert, A. J.

In Proceedings of the 2013 IEEE/RSJ International Conference on Intelligent Robots and Systems, pages: 3265-3272, IEEE, Tokyo, 2013 (inproceedings)

Abstract
The design of efficient locomotion gaits for robots with many degrees of freedom is challenging and time consuming even if optimization techniques are applied. Control parameters can be found through optimization in two ways: (i) through online optimization where the performance of a robot is measured while trying different control parameters on the actual hardware and (ii) through offline optimization by simulating the robot’s behavior with the help of models of the robot and its environment. In this paper, we present a hybrid optimization method that combines the best properties of online and offline optimization to efficiently find locomotion gaits for arbitrary structures. In comparison to pure online optimization, both the number of experiments using robotic hardware as well as the total time required for finding efficient locomotion gaits get highly reduced by running the major part of the optimization process in simulation using a cluster of processors. The presented example shows that even for robots with a low number of degrees of freedom the time required for optimization can be reduced by a factor of 2.5 to 30, at least, depending on how extensive the search for optimized control parameters should be. Time for hardware experiments becomes minimal. More importantly, gaits that can possibly damage the robotic hardware can be filtered before being tried in hardware. Yet in contrast to pure offline optimization, we reach well matched behavior that allows a direct transfer of locomotion gaits from simulation to hardware. This is because through a meta-optimization we adapt not only the locomotion parameters but also the parameters for simulation models of the robot and environment allowing for a good matching of the robot behavior in simulation and hardware. We validate the proposed hybrid optimization method on a structure composed of two Roombots modules with a total number of six degrees of freedom. Roombots are self-reconfigurable modular robots that can form arbitrary structures with many degrees of freedom through an integrated active connection mechanism.

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DOI [BibTex]

DOI [BibTex]


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Efficient 3D Object Perception and Grasp Planning for Mobile Manipulation in Domestic Environments

Stueckler, J., Steffens, R., Holz, D., Behnke, S.

Robotics and Autonomous Systems (RAS), 61(10):1106-1115, 2013 (article)

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


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NimbRo@Home: Winning Team of the RoboCup@Home Competition 2012

Stueckler, J., Badami, I., Droeschel, D., Gräve, K., Holz, D., McElhone, M., Nieuwenhuisen, M., Schreiber, M., Schwarz, M., Behnke, S.

In RoboCup 2012, Robot Soccer World Cup XVI, pages: 94-105, Springer, 2013 (inbook)

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


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Modular Control of Limit Cycle Locomotion over Unperceived Rough Terrain

Ajallooeian, M., Gay, S., Tuleu, A., Spröwitz, A., Ijspeert, A. J.

In Proceedings of the IEEE/RSJ International Conference on Intelligent Robots and Systems, 2013, pages: 3390-3397, Tokyo, 2013 (inproceedings)

Abstract
We present a general approach to design modular controllers for limit cycle locomotion over unperceived rough terrain. The control strategy uses a Central Pattern Generator (CPG) model implemented as coupled nonlinear oscillators as basis. Stumbling correction and leg extension reflexes are implemented as feedbacks for fast corrections, and model-based posture control mechanisms define feedbacks for continuous corrections. The control strategy is validated on a detailed physics-based simulated model of a compliant quadruped robot, the Oncilla robot. We demonstrate dynamic locomotion with a speed of more than 1.5 BodyLength/s over unperceived uneven terrains, steps, and slopes.

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DOI [BibTex]

DOI [BibTex]


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Horse-Like Walking, Trotting, and Galloping derived from Kinematic Motion Primitives (kMPs) and their Application to Walk/Trot Transitions in a Compliant Quadruped Robot

Moro, F., Spröwitz, A., Tuleu, A., Vespignani, M., Tsagakiris, N. G., Ijspeert, A. J., Caldwell, D. G.

Biological Cybernetics, 107(3):309-320, 2013 (article)

Abstract
This manuscript proposes a method to directly transfer the features of horse walking, trotting, and galloping to a quadruped robot, with the aim of creating a much more natural (horse-like) locomotion profile. A principal component analysis on horse joint trajectories shows that walk, trot, and gallop can be described by a set of four kinematic Motion Primitives (kMPs). These kMPs are used to generate valid, stable gaits that are tested on a compliant quadruped robot. Tests on the effects of gait frequency scaling as follows: results indicate a speed optimal walking frequency around 3.4 Hz, and an optimal trotting frequency around 4 Hz. Following, a criterion to synthesize gait transitions is proposed, and the walk/trot transitions are successfully tested on the robot. The performance of the robot when the transitions are scaled in frequency is evaluated by means of roll and pitch angle phase plots.

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DOI [BibTex]

DOI [BibTex]


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Efficient Dense 3D Rigid-Body Motion Segmentation in RGB-D Video

Stueckler, J., Behnke, S.

In Proc. of the British Machine Vision Conference (BMVC), 2013 (inproceedings)

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link (url) [BibTex]

link (url) [BibTex]


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Mobile bin picking with an anthropomorphic service robot

Nieuwenhuisen, M., Droeschel, D., Holz, D., Stueckler, J., Berner, A., Li, J., Klein, R., Behnke, S.

In Proc. of the IEEE International Conference on Robotics and Automation (ICRA), pages: 2327-2334, May 2013 (inproceedings)

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


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Multi-resolution surfel mapping and real-time pose tracking using a continuously rotating 2D laser scanner

Schadler, M., Stueckler, J., Behnke, S.

In Proc. of the IEEE International Symposium on Safety, Security, and Rescue Robotics (SSRR), pages: 1-6, October 2013 (inproceedings)

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


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Joint detection and pose tracking of multi-resolution surfel models in RGB-D

McElhone, M., Stueckler, J., Behnke, S.

In Proc. of the European Conference on Mobile Robots (ECMR), pages: 131-137, IEEE, 2013 (inproceedings)

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link (url) [BibTex]

link (url) [BibTex]


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Distinctive 3D surface entropy features for place recognition.

Fiolka, T., Stueckler, J., Klein, D. A., Schulz, D., Behnke, S.

In Proc. of the European Conference on Mobile Robots (ECMR), pages: 204-209, IEEE, 2013 (inproceedings)

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link (url) [BibTex]

link (url) [BibTex]


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Combining contour and shape primitives for object detection and pose estimation of prefabricated parts

Berner, A., Li, J., Holz, D., Stueckler, J., Behnke, S., Klein, R.

In Proc. of the 20th IEEE International Conference on Image Processing (ICIP), pages: 3326-3330, sep 2013 (inproceedings)

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


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Hierarchical Object Discovery and Dense Modelling From Motion Cues in RGB-D Video

Stueckler, J., Behnke, S.

In Proc. of the 23rd International Joint Conference on Artificial Intelligence (IJCAI), IJCAI/AAAI, 2013 (inproceedings)

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link (url) [BibTex]

link (url) [BibTex]

2008


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Learning to Move in Modular Robots using Central Pattern Generators and Online Optimization

Spröwitz, A., Moeckel, R., Maye, J., Ijspeert, A. J.

The International Journal of Robotics Research, 27(3-4):423-443, 2008 (article)

Abstract
This article addresses the problem of how modular robotics systems, i.e. systems composed of multiple modules that can be configured into different robotic structures, can learn to locomote. In particular, we tackle the problems of online learning, that is, learning while moving, and the problem of dealing with unknown arbitrary robotic structures. We propose a framework for learning locomotion controllers based on two components: a central pattern generator (CPG) and a gradient-free optimization algorithm referred to as Powell's method. The CPG is implemented as a system of coupled nonlinear oscillators in our YaMoR modular robotic system, with one oscillator per module. The nonlinear oscillators are coupled together across modules using Bluetooth communication to obtain specific gaits, i.e. synchronized patterns of oscillations among modules. Online learning involves running the Powell optimization algorithm in parallel with the CPG model, with the speed of locomotion being the criterion to be optimized. Interesting aspects of the optimization include the fact that it is carried out online, the robots do not require stopping or resetting and it is fast. We present results showing the interesting properties of this framework for a modular robotic system. In particular, our CPG model can readily be implemented in a distributed system, it is computationally cheap, it exhibits limit cycle behavior (temporary perturbations are rapidly forgotten), it produces smooth trajectories even when control parameters are abruptly changed and it is robust against imperfect communication among modules. We also present results of learning to move with three different robot structures. Interesting locomotion modes are obtained after running the optimization for less than 60 minutes.

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link (url) DOI [BibTex]

2008


link (url) DOI [BibTex]


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Hierarchical Reactive Control for Humanoid Soccer Robots

Behnke, S., Stueckler, J.

International Journal of Humanoid Robots (IJHR), 5(3):375-396, 2008 (article)

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link (url) [BibTex]

link (url) [BibTex]


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Passive compliant quadruped robot using central pattern generators for locomotion control

Rutishauser, S., Spröwitz, A., Righetti, L., Ijspeert, A. J.

In Proceedings of the 2008 2nd Biennial IEEE/RAS-EMBS International Conference on Biomedical Robotics and Biomechatronics, pages: 710-715, IEEE, Scottsdale, AZ, 2008 (inproceedings)

Abstract
We present a new quadruped robot, “Cheetah”, featuring three-segment pantographic legs with passive compliant knee joints. Each leg has two degrees of freedom - knee and hip joint can be actuated using proximal mounted RC servo motors, force transmission to the knee is achieved by means of a Bowden cable mechanism. Simple electronics to command the actuators from a desktop computer have been designed in order to test the robot. A Central Pattern Generator (CPG) network has been implemented to generate different gaits. A parameter space search was performed and tested on the robot to optimize forward velocity.

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DOI [BibTex]

DOI [BibTex]


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Graph signature for self-reconfiguration planning

Asadpour, M., Spröwitz, A., Billard, A., Dillenbourg, P., Ijspeert, A. J.

In Proceedings of the 2008 IEEE/RSJ International Conference on Intelligent Robots and Systems, pages: 863-869, IEEE, Nice, 2008 (inproceedings)

Abstract
This project incorporates modular robots as build- ing blocks for furniture that moves and self-reconfigures. The reconfiguration is done using dynamic connection / disconnection of modules and rotations of the degrees of freedom. This paper introduces a new approach to self-reconfiguration planning for modular robots based on the graph signature and the graph edit-distance. The method has been tested in simulation on two type of modules: YaMoR and M-TRAN. The simulation results shows interesting features of the approach, namely rapidly finding a near-optimal solution.

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DOI [BibTex]

DOI [BibTex]


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An active connection mechanism for modular self-reconfigurable robotic systems based on physical latching

Spröwitz, A., Asadpour, M., Bourquin, Y., Ijspeert, A. J.

In Proceedings on the 2008 IEEE International Conference on Robotics and Automation (ICRA), 2008, pages: 3508-3513, IEEE, Pasadena, CA, 2008 (inproceedings)

Abstract
This article presents a robust and heavy duty physical latching connection mechanism, which can be actuated with DC motors to actively connect and disconnect modular robot units. The special requirements include a lightweight and simple construction providing an active, strong, hermaphrodite, completely retractable connection mechanism with a 90 degree symmetry and a no-energy consumption in the locked state. The mechanism volume is kept small to fit multiple copies into a single modular robot unit and to be used on as many faces of the robot unit as possible. This way several different lattice like modular robot structures are possible. The large selection for dock-able connection positions will likely simplify self-reconfiguration strategies. Tests with the implemented mechanism demonstrate its applicative potential for self-reconfiguring modular robots.

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DOI [BibTex]

DOI [BibTex]


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In-lane Localization in Road Networks using Curbs Detected in Omnidirectional Height Images

Stueckler, J., Schulz, H., Behnke, S.

In Proceedings of Robotik 2008, 2008 (inproceedings)

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link (url) [BibTex]

link (url) [BibTex]


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Orthogonal wall correction for visual motion estimation

Stueckler, J., Behnke, S.

In Proc. of the IEEE Int. Conf. on Robotics and Automation (ICRA), pages: 1-6, May 2008 (inproceedings)

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link (url) DOI [BibTex]

link (url) DOI [BibTex]

2005


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Adaptation of Central Pattern Generators to Preexisting Mechanical Structure

Spröwitz, A.

Technische Universität Ilmenau, Ilmenau, 2005 (mastersthesis)

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[BibTex]

2005


[BibTex]