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2010 IEEE/RSJ International Conference on intelligent Robots and systems

作者： Marco Hutter C. David Remy Mark A. Höpflinger Roland Siegwart Autonomous Systems Laboratory Institute of Robotics and Intelligent Systems Swiss Federal Institute of Technology Zurich Switzerland Autonomous Systems Lab Swiss Federal Institute of Technology (ETHZ) Zurich Switzerland

SLIP models are generally known as one of the best and simplest abstractions describing the spring-like leg behavior found in human and animal running, and have thus been subject to exhaustive investigation. To exploit these findings in real robots, we utilize an operational space controller that projects the behavior of the SLIP model onto the dynamics of an actual segmented robotic leg. Additionally, we introduce a method to compensate for the energetic losses at the impact collisions, which are not accounted for in the simplified SLIP assumptions. This allows the direct application of existing dead-beat control strategies to arbitrary robotic legs, for which we can show that the collision and compensation effects in the actual leg enlarge the regions of stable running and reduce the minimally required locomotion speed. The necessary joint torque profiles can be generated in large part passively, for example by using high compliance series elastic actuators.

关键词： Leg Legged locomotion Springs Joints Aerospace electronics Dynamics

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Ensemble usage for more reliable policy identification in reinforcement learning

Ensemble usage for more reliable policy identification in re...

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作者： Hans, Alexander Udluft, Steffen Ilmenau University of Technology Neuroinformatics and Cognitive Robotics Lab P.O. Box 100565 D-98684 Ilmenau Germany Siemens AG Corporate Technology Intelligent Systems and Control Otto-Hahn-Ring 6 D-81739 Munich Germany

ISBN: (纸本)9782874190445

Reinforcement learning (RL) methods employing powerful function approximators like neural networks have become an interesting approach for optimal control. Since they learn a policy from observations, they are also applicable when no analytical description of the system is available. Although impressive results have been reported, their handling in practice is still hard, as they can fail at reliably determining a good policy. In previous work, we used ensembles of policies from independent runs of neural fitted Q-iteration (NFQ) to produce successful policies more reliably. In this paper we evaluate the approach on more problems and propose to form ensembles from successive iterations of a single NFQ run as a computationally cheap alternative to completely independent runs.

关键词： Iterative methods

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A tendon-based parallel robot applied to motor learning in sports

A tendon-based parallel robot applied to motor learning in s...

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IEEE/RAS-EMBS International Conference on Biomedical robotics and Biomechatronics (BioRob)

作者： Georg Rauter Joachim von Zitzewitz Alexander Duschau-Wicke Heike Vallery Robert Riener Sensory-Motor Systems SMS Lab Institute of Robotics and Intelligent Systems Zurich Switzerland Hocoma AG Volketswil Switzerland Medical Faculty University of Zurich Zurich Switzerland

Research in multimodal motor learning in sports is highly demanding with respect to the equipment, especially when the same equipment has to be reconfigured for different applications. In our multimodal motion synthesis lab (M 3 -lab) we apply visual, auditory, and haptic displays as well as feedback to enhance human motor learning. The demands on our haptic display, a tendon-based parallel robot (TBPR), are particularly high: a large workspace needs to be covered, the robotic device must be versatile, the visual and auditory modality should not be affected, high velocities and forces have to be realizable to render different sports applications, and user-cooperative control strategies should be applicable. In a first sports application, the TBPR is used as a haptic display for a rowing simulator. Until now, the TBPR could only display horizontal forces at the oar blade of the rowing simulator. In this paper, the rowing forces are extended to all three directions. To realize this extension of force directions over the entire workspace, the TBPR has to be actuated redundantly. This redundancy poses additional challenges for the implementation of assistive control strategies presented in this paper: a position control strategy and the Generalized Elastic Path Control strategy (a passive strategy using a potential field to compliantly keep the user on a path). These two control strategies have been successfully evaluated with respect to our requirements in terms of accuracy and stability. The presented TBPR can now be used to investigate the impact of different haptic feedbacks on rowing performance.

关键词： Robots Force Humans Rendering (computer graphics) Haptic interfaces Blades Adaptation model

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MULTI-CAMERA POSITIONING FOR AUTOMATED TRACKING systems IN DYNAMIC ENVIRONMENTS

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International Journal of Information Acquisition 2010年第3期7卷 225-242页

作者： YI YAO CHUNG-HAO CHEN BESMA ABIDI DAVID PAGE ANDREAS KOSCHAN MONGI ABIDI Visualization and Computer Vision Lab GE Global Research USA Department of Mathematics and Computer Science North Carolina Central University USA Imaging Robotics and Intelligent Systems Lab University of Tennessee Knoxville USA

Most existing camera placement algorithms focus on coverage and/or visibility analysis, which ensures that the object of interest is visible in the camera's field of view (FOV). According to recent literature, handoff safety margin is introduced to sensor planning so that sufficient overlapped FOVs among adjacent cameras are reserved for successful and smooth target transition. In this paper, we investigate the sensor planning problem when considering the dynamic interactions between moving targets and observing cameras. The probability of camera overload is explored to model the aforementioned interactions. The introduction of the probability of camera overload also considers the limitation that a given camera can simultaneously monitor or track a fixed number of targets and incorporates the target's dynamics into sensor planning. The resulting camera placement not only achieves the optimal balance between coverage and handoff success rate but also maintains the optimal balance in environments with various target densities. The proposed camera placement method is compared with a reference algorithm by Erdem and Sclaroff. Consistently improved handoff success rate is illustrated via experiments using typical office floor plans with various target densities.

关键词： Sensor planning visual surveillance multiple camera systems camera handoff

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Hiding robot inertia using resonance

Hiding robot inertia using resonance

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Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC)

作者： Heike Vallery Alexander Duschau-Wicke Robert Riener Medical Faculty University of Zurich Switzerland Sensory-Motor Systems SMS Lab Institute of Robotics and Intelligent Systems IRIS ETH Zurich Switzerland Hocoma AG Volketswil Switzerland

To enable compliant training modes with a rehabilitation robot, an important prerequisite is that any undesired human-robot interaction forces caused by robot dynamics must be avoided, either by an appropriate mechanical design or by compensating control strategies. Our recently proposed control scheme of “Generalized Elasticities” employs potential fields to compensate for robot dynamics, including inertia, beyond what can be done using closed-loop force control. In this paper, we give a simple mechanical equivalent using the example of the gait rehabilitation robot Lokomat. The robot consists of an exoskeleton that is attached to a frame around the patient's pelvis. This frame is suspended by a springloaded parallelogram structure. The mechanism allows vertical displacement while providing almost constant robot gravity compensation. However, inertia of the device when the patient's pelvis moves up and down remains a source of large interaction forces, which are reflected in increased ground reaction forces. Here, we investigate an alternative suspension: To hide not only gravity, but also robot inertia during vertical pelvis motion, we suspend the robot frame by a stiff linear spring that allows the robot to oscillate vertically at an eigenfrequency close to the natural gait frequency. This mechanism reduces human-robot interaction forces, which is demonstrated in pilot experimental results.

关键词： Legged locomotion Springs Gravity Humans Suspensions

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Psychological state estimation during robot assisted gait training

Psychological state estimation during robot assisted gait tr...

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4th International Conference on Cognitive systems, CogSys 2010

作者： Koenig, A. Omlin, X. Bolliger, M. Zimmerli, L. Krewer, C. Sapa, M. Müller, F. Riener, R. Sensory-Motor Systems Lab. Inst. for Robotics and Intelligent Systems Dept. of Mechanical and Process Eng. Tannenstrasse 1 CH-8092 Zurich Switzerland Spinal Cord Injury Center University Hospital Balgrist University of Zurich Switzerland Hocoma Inc. Industriestrasse 4 CH-8604 Volketswil Switzerland Neurologische Klinik Bad Aibling Kolbermoorer Str. 72 D-83043 Bad Aibling Germany

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Adaptive predictive control of a class of discrete-time MIMO nonlinear systems with uncertain couplings

Adaptive predictive control of a class of discrete-time MIMO...

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作者： Yang, Chenguang Li, Yanan Ge, Shuzhi Sam Lee, Tong Heng Department of Bioengineering Imperial College London London SW7 2AZ United Kingdom Social Robotics Lab Interactive Digital Media Institute and Department of Electrical and Computer Engineering National University of Singapore Singapore 117576 Singapore Institute of Intelligent Systems University of Electronic Science and Technology of China Chengdu 610054 China

ISBN: (纸本)9781424474264

In this paper, a novel adaptive predictive control is presented for a class of multi-input-multi-output (MIMO) nonlinear systems in block-triangular form with uncertain couplings of states/delayed states as well as inputs among subsystems. For each subsystem of the MIMO system, future states prediction is developed and using the predicted future states, adaptive predictive control is designed under certainty equivalence principal to compensate the parametric uncertainties in the couplings. To eliminate the functional uncertainties in the couplings, a novel compensation mechanism is developed for each subsystem. Under the proposed adaptive controls, all the signals in the closed-loop MIMO systems are guaranteed to be globally bounded. In addition, all the output tracking errors are guaranteed to converge to zeros. The effectiveness of the proposed control is demonstrated in the simulation. © 2010 AACC.

关键词： Couplings

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Learning compliance control of robot manipulators in contact with the unknown environment

Learning compliance control of robot manipulators in contact...

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2010 IEEE International Conference on Automation Science and Engineering, CASE 2010

作者： Li, Yanan Yang, Chenguang Ge, Shuzhi Sam Social Robotics Lab. NUS Graduate School for Integrative Sciences and Engineering National University of Singapore Singapore 119613 Singapore Department of Bioengineering Imperial College London London SW7 2AZ United Kingdom Department of Electrical and Computer Engineering Interactive Digital Media Institute National University of Singapore Singapore 117576 Singapore Institute of Intelligent Systems University of Electronic Science and Technology of China Chengdu 610054 China

ISBN: (纸本)9781424454471

In this paper, a control mechanism is presented to improve the compliance performance of the robot manipulator when it is in contact with the unknown environment. This mechanism guarantees that the dynamics of the whole system follows a target impedance model so that the desired compliance performance is obtained. In particular, under the assumption that the dynamics is periodic, a learning law is developed to estimate the unknown dynamics parameters. Besides, the proposed systematic learning control does not require the accurate force measurement. Its performance and robustness are discussed in details by the rigorous analysis. At last, the validity of the proposed method is verified by simulation. © 2010 IEEE.

关键词： Modular robots

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High-fidelity device for online recording of foot-stretcher forces during rowing

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Procedia Engineering 2010年第2期2卷 2721-2726页

作者： Dominik Krumm Martin Simnacher Georg Rauter Andreas Brunschweiler Stephan Odenwald Robert Riener Peter Wolf Sensory-Motor Systems Lab Institute of Robotics and Intelligent Systems Department of Mechanical and Process Engineering ETH Zurich Tannenstrasse 1 CH-8092 Zurich Switzerland Sports Equipment and Technology Institute of Mechanical and Polymer Engineering Chemnitz University of Technology Reichenhainer Strasse 70 D-09126 Chemnitz Germany Spinal Injury Center Balgrist University Hospital University of Zurich Forchstrasse 340 CH-8008 Zurich Switzerland

Foot-stretcher forces have been identified as key variables determining rowing performance. The aim of this study was to develop an instrumented foot-stretcher. Under each forefoot, a six degrees of freedom sensor was mounted on an adjustable frame. Under each rearfoot, a one degree of freedom sensor was placed. Validation resulted in an accuracy of vertical forces of about 1% full scale. Sensor’s crosstalk was up to 11% of vertical load. The instrumented foot-stretcher was integrated into a high-level rowing simulator. Propulsive foot-stretcher forces were displayed online and could be used as concurrent feedback about rowing performance.

关键词： Instrumented foot-stretcher Engineering design 3D Kinetics Concurrent feedback Rowing simulator

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Assessment of lower extremity motor adaptation via an extension of the Force Field Adaptation Paradigm

Assessment of lower extremity motor adaptation via an extens...

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Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC)

作者： Iahn Cajigas Mary T. Goldsmith Alexander Duschau-Wicke Robert Riener Maurice A. Smith Emery N. Brown Paolo Bonato Department of Physical Medicine and Rehabilitation Harvard Medical School and Spaulding RehabilitationHospital Boston MA USA Department of Biomedical Engineering Boston University USA Sensory-Motor Systems (SMS) Lab Institute of Robotics and Intelligent System (IRIS) University of Zurich Switzerland Harvard-MIT Department Health Sciences and Technology USA Spaulding Rehabilitation Hospital Charlestown MA US

Lower extremity rehabilitation has seen recent increased interest. New tools are available to improve gait retraining in both adults and children. However, it remains difficult to determine optimal ways to plan interventions due to difficulties in continuously monitoring outcomes in patients undergoing rehabilitation. In this paper, we introduce an extension of the Force Field Adaptation Paradigm, used to quantitatively assess upper extremity motor adaptation, to the lower extremity. The algorithm is implemented on the Lokomat lower extremity gait orthosis and utilized to assess short-term motor adaptation. Establishing an understanding of how healthy adults' motor systems adapt to external perturbations will be important to understanding how the adaptive mechanisms involved in gait are altered by disease.

关键词： Force Extremities Robots Trajectory Joints Training Force measurement

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