We report nano-selective area growth (NSAG) of BGaN by MOCVD on AlN/Si(111) and GaN templates res... more We report nano-selective area growth (NSAG) of BGaN by MOCVD on AlN/Si(111) and GaN templates resulting in 150 nm single crystalline nanopyramids. This is in contrast to unmasked or micro-selective area growth, which results in a multi-crystalline structure on both substrates. Various characterization techniques were used to evaluate NSAG as a viable technique to improve BGaN material quality on AlN/Si(111) using results of GaN NSAG and unmasked BGaN growth for comparison. Evaluation of BGaN nanopyramid quality, shape and size uniformity revealed that the growth mechanism is the same on both the templates. Further STEM analysis of BGaN nanopyramids on AlN/Si (111) templates confirmed that these are singlecrystalline structures without any dislocations, likely due to single nucleation occurring in the 80 nm mask opening. CL results correspond to boron content between 1.7% and 2.0% in the nanopyramids. We conclude that NSAG is promising for growth of high-quality BGaN nanostructures and complex nano-heterostructures, especially for low-cost silicon substrates
ACM SIGGRAPH 2014 Emerging Technologies on - SIGGRAPH '14, 2014
ABSTRACT Interactively articulating virtual 3D characters lies at the heart of computer animation... more ABSTRACT Interactively articulating virtual 3D characters lies at the heart of computer animation and geometric modeling. Expressive articulation requires control over many degrees of freedom: most often the joint angles of an internal skeleton. We introduce a physical input device assembled on the fly to control any character's skeleton directly. With traditional mouse and keyboard input, animators must rely on indirect methods such as inverse kinematics or decompose complex and integrated motions into smaller sequential manipulations---for example, iteratively positioning each bone of a skeleton hierarchy. While direct manipulation mouse and touch interfaces are successful in 2D [Shneiderman 1997], 3D interactions with 2D input are ill-posed and thus more challenging. Successful commercial products with 2D interfaces, e.g. Autodesk's Maya, have notoriously steep learning curves and require interface-specific training.
ABSTRACT Automatic differentiation (AD) is a useful tool for computing Jacobians of functions nee... more ABSTRACT Automatic differentiation (AD) is a useful tool for computing Jacobians of functions needed in estimation and control algorithms. However, for many inter- esting problems in robotics, state variables live on a differentiable manifold. The most common example are robot orientations that are elements of the Lie group SO(3). This causes problems for AD algorithms that only consider differentiation at the scalar level. Jacobians produced by scalar AD are correct, but scalar-focused methods are unable to apply simplifications based on the structure of the specific manifold. In this paper we extend the theory of AD to encompass handling of differ- entiable manifolds and provide a C++ library that exploits strong typing and expres- sion templates for fast, easy-to-use Jacobian evaluation. This method has a number of benefits over scalar AD. First, it allows the exploitation of algebraic simplifica- tions that make Jacobian evaluations more efficient than their scalar counterparts. Second, strong typing reduces the likelihood of programming errors arising from misinterpretation that are possible when using simple arrays of scalars. To the best of our knowledge, this is the first work to consider the structure of differentiable manifolds directly in AD.
In this paper a turtle&am... more In this paper a turtle's hydrofoil 2 DoF's mechanism (degrees of freedom) is implemented and tested in a water channel as a propulsion system for an Autonomous Underwater Vehicle (AUV). The experiments carried out showed an optimal empirical value of the angle of attack for the turtle's hydrofoil that is compared with the theoretical value. The hydrofoil path used in
2010 IEEE/RSJ International Conference on Intelligent Robots and Systems, 2010
... The authors would like to thank their colleagues for their help and support. In particular St... more ... The authors would like to thank their colleagues for their help and support. In particular Stephan Weiss and Markus Achtelik from ASL ETH for gathering the data set and Friedrich Fraundorfer for helping with the bag-of-words algorithm. ...
Emerging Trends in Mobile Robotics - Proceedings of the 13th International Conference on Climbing and Walking Robots and the Support Technologies for Mobile Machines, 2010
... C. David Remy, Oliver Baur, Martin Latta, Andi Lauber, Marco Hutter, Mark A. Hoepflinger, Céd... more ... C. David Remy, Oliver Baur, Martin Latta, Andi Lauber, Marco Hutter, Mark A. Hoepflinger, Cédric Pradalier and Roland Siegwart Autonomous Systems Lab ... it was equipped with pan-tilt cameras, lights, a dust-protection cover, and scaled plates under the shanks and the main ...
2012 IEEE/RSJ International Conference on Intelligent Robots and Systems, 2012
ABSTRACT Pseudo-omnidirectional robots with independently steerable wheels require a method to sy... more ABSTRACT Pseudo-omnidirectional robots with independently steerable wheels require a method to synchronize the steering motion of the wheels in order to keep a unique instantaneous center of rotation (ICR). For standard wheels, the instantaneous center of rotation is defined as the intersection point of all wheel axes. We present a novel approach to deal with the problem of continuously shifting the center of rotation of a pseudo-omnidirectional rover from an initial to a demanded position in the Cartesian plane. The main contribution is the consideration of substantial velocity and acceleration limits on the steering units, as well as mechanical constraints and noise affected sensor measurements. We solve this problem by deriving a relationship between the steering accelerations of the single wheels and the acceleration of the center of rotation. We furthermore provide a contribution to the tracking of the ICR in the presence of significant sensor noise. Our results are evaluated by tests on the rover breadboard developed during the activities for the ExoMars mission.
2013 IEEE/RSJ International Conference on Intelligent Robots and Systems, 2013
ABSTRACT This paper presents a novel underwater robot based on biological locomotion principle. A... more ABSTRACT This paper presents a novel underwater robot based on biological locomotion principle. A robotic platform imitating sea-turtle fin propulsion is described and tested. As fin locomotion is a novel and complex research area, basic control concepts are analyzed and implemented. Based on a simulation, a fin-trajectory morphing control strategy is developed in order to control the robots roll, pitch and yaw rates, thus allowing the robot to follow a given vector. Absolute position control or depth control, however, is not yet implemented. The paper concludes with the presentation of a working system that demonstrated motion capabilities in air as well as the first dive test in a swimming pool.
We report nano-selective area growth (NSAG) of BGaN by MOCVD on AlN/Si(111) and GaN templates res... more We report nano-selective area growth (NSAG) of BGaN by MOCVD on AlN/Si(111) and GaN templates resulting in 150 nm single crystalline nanopyramids. This is in contrast to unmasked or micro-selective area growth, which results in a multi-crystalline structure on both substrates. Various characterization techniques were used to evaluate NSAG as a viable technique to improve BGaN material quality on AlN/Si(111) using results of GaN NSAG and unmasked BGaN growth for comparison. Evaluation of BGaN nanopyramid quality, shape and size uniformity revealed that the growth mechanism is the same on both the templates. Further STEM analysis of BGaN nanopyramids on AlN/Si (111) templates confirmed that these are singlecrystalline structures without any dislocations, likely due to single nucleation occurring in the 80 nm mask opening. CL results correspond to boron content between 1.7% and 2.0% in the nanopyramids. We conclude that NSAG is promising for growth of high-quality BGaN nanostructures and complex nano-heterostructures, especially for low-cost silicon substrates
ACM SIGGRAPH 2014 Emerging Technologies on - SIGGRAPH '14, 2014
ABSTRACT Interactively articulating virtual 3D characters lies at the heart of computer animation... more ABSTRACT Interactively articulating virtual 3D characters lies at the heart of computer animation and geometric modeling. Expressive articulation requires control over many degrees of freedom: most often the joint angles of an internal skeleton. We introduce a physical input device assembled on the fly to control any character's skeleton directly. With traditional mouse and keyboard input, animators must rely on indirect methods such as inverse kinematics or decompose complex and integrated motions into smaller sequential manipulations---for example, iteratively positioning each bone of a skeleton hierarchy. While direct manipulation mouse and touch interfaces are successful in 2D [Shneiderman 1997], 3D interactions with 2D input are ill-posed and thus more challenging. Successful commercial products with 2D interfaces, e.g. Autodesk's Maya, have notoriously steep learning curves and require interface-specific training.
ABSTRACT Automatic differentiation (AD) is a useful tool for computing Jacobians of functions nee... more ABSTRACT Automatic differentiation (AD) is a useful tool for computing Jacobians of functions needed in estimation and control algorithms. However, for many inter- esting problems in robotics, state variables live on a differentiable manifold. The most common example are robot orientations that are elements of the Lie group SO(3). This causes problems for AD algorithms that only consider differentiation at the scalar level. Jacobians produced by scalar AD are correct, but scalar-focused methods are unable to apply simplifications based on the structure of the specific manifold. In this paper we extend the theory of AD to encompass handling of differ- entiable manifolds and provide a C++ library that exploits strong typing and expres- sion templates for fast, easy-to-use Jacobian evaluation. This method has a number of benefits over scalar AD. First, it allows the exploitation of algebraic simplifica- tions that make Jacobian evaluations more efficient than their scalar counterparts. Second, strong typing reduces the likelihood of programming errors arising from misinterpretation that are possible when using simple arrays of scalars. To the best of our knowledge, this is the first work to consider the structure of differentiable manifolds directly in AD.
In this paper a turtle&am... more In this paper a turtle's hydrofoil 2 DoF's mechanism (degrees of freedom) is implemented and tested in a water channel as a propulsion system for an Autonomous Underwater Vehicle (AUV). The experiments carried out showed an optimal empirical value of the angle of attack for the turtle's hydrofoil that is compared with the theoretical value. The hydrofoil path used in
2010 IEEE/RSJ International Conference on Intelligent Robots and Systems, 2010
... The authors would like to thank their colleagues for their help and support. In particular St... more ... The authors would like to thank their colleagues for their help and support. In particular Stephan Weiss and Markus Achtelik from ASL ETH for gathering the data set and Friedrich Fraundorfer for helping with the bag-of-words algorithm. ...
Emerging Trends in Mobile Robotics - Proceedings of the 13th International Conference on Climbing and Walking Robots and the Support Technologies for Mobile Machines, 2010
... C. David Remy, Oliver Baur, Martin Latta, Andi Lauber, Marco Hutter, Mark A. Hoepflinger, Céd... more ... C. David Remy, Oliver Baur, Martin Latta, Andi Lauber, Marco Hutter, Mark A. Hoepflinger, Cédric Pradalier and Roland Siegwart Autonomous Systems Lab ... it was equipped with pan-tilt cameras, lights, a dust-protection cover, and scaled plates under the shanks and the main ...
2012 IEEE/RSJ International Conference on Intelligent Robots and Systems, 2012
ABSTRACT Pseudo-omnidirectional robots with independently steerable wheels require a method to sy... more ABSTRACT Pseudo-omnidirectional robots with independently steerable wheels require a method to synchronize the steering motion of the wheels in order to keep a unique instantaneous center of rotation (ICR). For standard wheels, the instantaneous center of rotation is defined as the intersection point of all wheel axes. We present a novel approach to deal with the problem of continuously shifting the center of rotation of a pseudo-omnidirectional rover from an initial to a demanded position in the Cartesian plane. The main contribution is the consideration of substantial velocity and acceleration limits on the steering units, as well as mechanical constraints and noise affected sensor measurements. We solve this problem by deriving a relationship between the steering accelerations of the single wheels and the acceleration of the center of rotation. We furthermore provide a contribution to the tracking of the ICR in the presence of significant sensor noise. Our results are evaluated by tests on the rover breadboard developed during the activities for the ExoMars mission.
2013 IEEE/RSJ International Conference on Intelligent Robots and Systems, 2013
ABSTRACT This paper presents a novel underwater robot based on biological locomotion principle. A... more ABSTRACT This paper presents a novel underwater robot based on biological locomotion principle. A robotic platform imitating sea-turtle fin propulsion is described and tested. As fin locomotion is a novel and complex research area, basic control concepts are analyzed and implemented. Based on a simulation, a fin-trajectory morphing control strategy is developed in order to control the robots roll, pitch and yaw rates, thus allowing the robot to follow a given vector. Absolute position control or depth control, however, is not yet implemented. The paper concludes with the presentation of a working system that demonstrated motion capabilities in air as well as the first dive test in a swimming pool.
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Papers by C. Pradalier