The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
Laleh Makarem - One of the best experts on this subject based on the ideXlab platform.
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priority coordination of fiber Positioners in multi objects spectrographs
Ground-based and Airborne Instrumentation for Astronomy VII, 2018Co-Authors: Laleh Makarem, J P Kneib, Mohamed Bouri, Denis GilletAbstract:Projects such as "The Dark Energy Spectroscopic Instrument” (DESI) [4] or ”The Multi Object Optical and Near-infrared Spectrograph” (MOONS ) [5] are developing spectrographs, composed of more than thousand of optical fibers in a confined hexagonal focal plane, to study the evolution of the universe. Such systems allow fast reconfiguration of the fibers as they are moved simultaneously to their assigned target by a 2-arm Positioner within an short interval of time. Moreover, astronomers prioritize the observation of some objects over those that hold less information, creating a hierarchy of importances or priorities. In a scenario where not all the Positioners can reach their targets, It is important to ensure the observation of the high-priority targets. In previous works, a decentralized navigation function from the family of potential fields was used for collisionfree coordination. While it guarantees convergence of all the Positioners to their targets for DESI [1,2], it fails at planning motion for Positioners in MOONS [3]. The reason is that the second arm of the Positioners in MOONS is two times the length of the first arm. Covering a larger working space, they are prone to deadlocks, a situation where two or more Positioners are blocked by each other and so unable to reach their targets. In this paper and in the framework of MOONS project, we present our new approach to integrate assigned priorities with the decentralized navigation functions to reduce the deadlocks situations. For this purpose, we regulate the movements of the Positioners using a finite-state machine combined with distance-based heuristics. Each Positioner’s state dictates its behaviors with respect to other Positioners. Distance-based heuristics limit the states transition when a Positioner is interacting with its adjacent Positioners to localize possible deadlock situations. The advantage of this method is its simplicity as it relies on local interaction of Positioners, keeping the complexity of the algorithm quasilinear. In addition, since it does not depend on the Positioner’s geometry, it is also scalable to other Positioner kinematics. We developed a motion planning simulator with a graphic interface in python to validate the coordination of the Positioners with assigned priorities. As a result, the number of Positioners converging to their targets improve from 60-70% to 80-95%. The computation time of the trajectories increases slightly due to the new layer of algorithm added for deadlocks prevention.
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collision free coordination of fiber Positioners in multi object spectrographs
Proceedings of SPIE, 2016Co-Authors: Laleh Makarem, J P Kneib, Denis GilletAbstract:Many fiber-fed spectroscopic survey projects, such as DESI, PFS and MOONS, will use thousands of fiber Positioners packed at a focal plane. To maximize observation time, the Positioners need to move simultaneously and reach their targets swiftly. We have previously presented a motion planning method based on a decentralized navigation function for the collision-free coordination of the fiber Positioners in DESI. In MOONS, the end effector of each Positioner handling the fiber can reach the centre of its neighbours. There is therefore a risk of collision with up to 18 surrounding Positioners in the chosen dense hexagonal configuration. Moreover, the length of the second arm of the Positioner is almost twice the length of the first one. As a result, the geometry of the potential collision zone between two Positioners is not limited to the extremity of their end-effector, but surrounds the second arm. In this paper, we modify the navigation function to take into account the larger collision zone resulting from the extended geometrical shape of the Positioners. The proposed navigation function takes into account the configuration of the Positioners as well as the constraints on the actuators, such as their maximal velocity and their mechanical clearance. Considering the fact that all the Positioners' bases are fixed to the focal plane, collisions can occur locally and the risk of collision is limited to the 18 surrounding Positioners. The decentralizing motion planning and trajectory generation takes advantage of this limited number of Positioners and the locality of collisions, hence significantly reduces the complexity of the algorithm to a linear order. The linear complexity ensures short computation time. In addition, the time needed to move all the Positioners to their targets is independent of the number of Positioners. These two key advantages of the chosen decentralization approach turn this method to a promising solution for the collision-free motion-planning problem in the next- generation spectroscopic survey projects. A motion planning simulator, exploited as a software prototype, has been developed in Python. The pre-computed collision-free trajectories of the actuators of all the Positioners are fed directly from the simulator to the electronics controlling the motors. A successful demonstration of the effectiveness of these trajectories on the real Positioners as well as their simulated counterparts are put side by side in the following online video sequence (https://goo.gl/YuwwsE).
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target based fiber assignment for large survey spectrographs
Proceedings of SPIE, 2016Co-Authors: Christoph E R Schaefer, Laleh Makarem, J P KneibAbstract:Next generation massive spectroscopic survey projects have to process a massive amount of targets. The preparation of subsequent observations should be feasible in a reasonable amount of time. We present a fast algorithm for target assignment that scales as O(log(n)). Our proposed algorithm follow a target based approach, which enables to assign large number of targets to their Positioners quickly and with a very high assignment efficiency. We also discuss additional optimization of the fiber positioning problem to take into account the Positioner collision problems and how to use the algorithm for an optimal survey strategy. We apply our target-based algorithm in the context of the MOONS project.
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collision free motion planning for fiber Positioner robots discretization of velocity profiles
Proceedings of SPIE, 2014Co-Authors: Laleh Makarem, J P Kneib, Denis Gillet, Hannes Bleuler, Mohamed Bouri, Philippe Horler, Laurent Jenni, F Prada, Justo SanchezAbstract:The next generation of large-scale spectroscopic survey experiments such as DESI, will use thousands of fiber Positioner robots packed on a focal plate. In order to maximize the observing time with this robotic system we need to move in parallel the fiber-ends of all Positioners from the previous to the next target coordinates. Direct trajectories are not feasible due to collision risks that could undeniably damage the robots and impact the survey operation and performance. We have previously developed a motion planning method based on a novel decentralized navigation function for collision-free coordination of fiber Positioners. The navigation function takes into account the configuration of Positioners as well as their envelope constraints. The motion planning scheme has linear complexity and short motion duration (2.5 seconds with the maximum speed of 30 rpm for the Positioner), which is independent of the number of Positioners. These two key advantages of the decentralization designate the method as a promising solution for the collision-free motion-planning problem in the next-generation of fiber-fed spectrographs. In a framework where a centralized computer communicates with the Positioner robots, communication overhead can be reduced significantly by using velocity profiles consisting of a few bits only. We present here the discretization of velocity profiles to ensure the feasibility of a real-time coordination for a large number of Positioners. The modified motion planning method that generates piecewise linearized position profiles guarantees collision-free trajectories for all the robots. The velocity profiles fit few bits at the expense of higher computational costs.
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Collision avoidance in next-generation fiber Positioner robotic systems for large survey spectrographs
Astronomy and Astrophysics - A&A, 2014Co-Authors: Laleh Makarem, J P Kneib, Denis Gillet, Hannes Bleuler, Mohamed Bouri, Laurent Jenni, F Prada, Justo SanchezAbstract:Some of the next-generation massive spectroscopic survey projects plan to use thousands of fiber Positioner robots packed at a focal plane to quickly move the fiber ends in parallel from the previous to the next target points. The most direct trajectories are prone to collision that could damage the robots and have an impact on the survey operation. We thus present here a motion planning method based on a novel decentralized navigation function for collision-free coordination of fiber Positioners. The navigation function takes into account the configuration of Positioners as well as the actuator constraints. We provide details of the proof of convergence and collision avoidance. Decentralization results in linear complexity for the motion planning as well as no dependence of motion duration on the number of Positioners. Therefore, the coordination method is scalable for large-scale spectrograph robots. The short in-motion duration of Positioner robots will thus allow the time dedicated for observation to be maximized.
Srinivasa M. Salapaka - One of the best experts on this subject based on the ideXlab platform.
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design methodologies for robust nano positioning
IEEE Transactions on Control Systems and Technology, 2005Co-Authors: Abu Sebastian, Srinivasa M. SalapakaAbstract:In this paper, we present a systematic control design and analysis for a two-dimensional nano-Positioner. The primary emphasis of the paper is on the robustness of the closed-loop device as these flexure-stage-based, piezoactuated nano-Positioners are nonlinear and operate in diverse conditions. To this end, we have used many tools from modern control theory to model devices and to quantify device resolution, bandwidth, and robustness. The implementation of this procedure for the simultaneous achievement of the objectives of robustness, high precision and high bandwidth is presented. The merits of the paradigm are demonstrated through experimental results.
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high bandwidth nano Positioner a robust control approach
Review of Scientific Instruments, 2002Co-Authors: Srinivasa M. Salapaka, Abu Sebastian, J P Cleveland, Murti V SalapakaAbstract:This article presents the design, identification, and control of a nano-positioning device suited to image biological samples as part of an atomic force microscope. The device is actuated by a piezoelectric stack and its motion is sensed by a linear variable differential transformer. It is demonstrated that the conventional proportional-integral control architecture does not meet the bandwidth requirements for positioning. The design and implementation of an H∞ controller demonstrates substantial improvements in the positioning speed and precision, while eliminating the undesirable nonlinear effects of the actuator. The characterization of the resulting device in terms of bandwidth, resolution, and repeatability provided illustrates the effectiveness of the modern robust control paradigm.
J P Kneib - One of the best experts on this subject based on the ideXlab platform.
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supervisory coordination of robotic fiber Positioners in multi object spectrographs
IFAC-PapersOnLine, 2019Co-Authors: Matin Macktoobian, Denis Gillet, J P KneibAbstract:Abstract In this paper, we solve the complete coordination problem of robotic fiber Positioners using supervisory control theory. In particular, we model Positioners and their behavioral specifications as discrete-event systems by the discretization of their motion spaces. We synthesize a coordination supervisor associated with a specific set of Positioners. In particular, the coordination supervisor includes the solutions to the complete coordination problem of its corresponding Positioners. Then, we use the backtracking forcibility technique of supervisory control theory to present an algorithm based on a completeness condition to solve the coordination problem similar to a reconfiguration problem. We illustrate the functionality of our method using an example.
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collision free coordination of fiber Positioners in multi object spectrographs
Proceedings of SPIE, 2016Co-Authors: Laleh Makarem, J P Kneib, Denis GilletAbstract:Many fiber-fed spectroscopic survey projects, such as DESI, PFS and MOONS, will use thousands of fiber Positioners packed at a focal plane. To maximize observation time, the Positioners need to move simultaneously and reach their targets swiftly. We have previously presented a motion planning method based on a decentralized navigation function for the collision-free coordination of the fiber Positioners in DESI. In MOONS, the end effector of each Positioner handling the fiber can reach the centre of its neighbours. There is therefore a risk of collision with up to 18 surrounding Positioners in the chosen dense hexagonal configuration. Moreover, the length of the second arm of the Positioner is almost twice the length of the first one. As a result, the geometry of the potential collision zone between two Positioners is not limited to the extremity of their end-effector, but surrounds the second arm. In this paper, we modify the navigation function to take into account the larger collision zone resulting from the extended geometrical shape of the Positioners. The proposed navigation function takes into account the configuration of the Positioners as well as the constraints on the actuators, such as their maximal velocity and their mechanical clearance. Considering the fact that all the Positioners' bases are fixed to the focal plane, collisions can occur locally and the risk of collision is limited to the 18 surrounding Positioners. The decentralizing motion planning and trajectory generation takes advantage of this limited number of Positioners and the locality of collisions, hence significantly reduces the complexity of the algorithm to a linear order. The linear complexity ensures short computation time. In addition, the time needed to move all the Positioners to their targets is independent of the number of Positioners. These two key advantages of the chosen decentralization approach turn this method to a promising solution for the collision-free motion-planning problem in the next- generation spectroscopic survey projects. A motion planning simulator, exploited as a software prototype, has been developed in Python. The pre-computed collision-free trajectories of the actuators of all the Positioners are fed directly from the simulator to the electronics controlling the motors. A successful demonstration of the effectiveness of these trajectories on the real Positioners as well as their simulated counterparts are put side by side in the following online video sequence (https://goo.gl/YuwwsE).
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target based fiber assignment for large survey spectrographs
Proceedings of SPIE, 2016Co-Authors: Christoph E R Schaefer, Laleh Makarem, J P KneibAbstract:Next generation massive spectroscopic survey projects have to process a massive amount of targets. The preparation of subsequent observations should be feasible in a reasonable amount of time. We present a fast algorithm for target assignment that scales as O(log(n)). Our proposed algorithm follow a target based approach, which enables to assign large number of targets to their Positioners quickly and with a very high assignment efficiency. We also discuss additional optimization of the fiber positioning problem to take into account the Positioner collision problems and how to use the algorithm for an optimal survey strategy. We apply our target-based algorithm in the context of the MOONS project.
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An 8-mm diameter fibre robot Positioner for massive spectroscopy surveys
Monthly Notices of the Royal Astronomical Society, 2015Co-Authors: N. Fahim, J P Kneib, F. Prada, G. Glez-de-rivera, P. Hoerler, J. Sanchez, M. Azzaro, S. Becerril, H. Bleuler, M. BouriAbstract:Massive spectroscopic survey are becoming trendy in astrophysics and cosmology, as they can address new fundamental knowledge such as understanding the formation of the Milky Way and probing the nature of the mysterious dark energy. To enable massive spectroscopic surveys, new technology has been developed to place thousands of optical fibres at a given position on a focal plane. This technology needs to be: (1) accurate, with micrometer positional accuracy; (2) fast to minimize overhead; (3) robust to minimize failure; and (4) low cost. In this paper, we present the development, properties, and performance of a new single 8-mm in diameter fibre Positioner robot, using two 4-mm DC-brushless gearmotors, that allows us to achieve accuracies up to 0.07 arcsec (5 mu m). This device has been developed in the context of the Dark Energy Spectroscopic Instrument.(1)
Mohamed Bouri - One of the best experts on this subject based on the ideXlab platform.
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optical test procedure for characterization and calibration of robotic fiber Positioners for multiobject spectrographs
Journal of Astronomical Telescopes Instruments and Systems, 2020Co-Authors: Luzius Kronig, J P Kneib, Philipp Horler, Stefane Caseiro, Loic Grossen, Ricardo Araujo, Mohamed BouriAbstract:The recent burgeoning interest in massive multiobject spectroscopy has pushed the development of massive optical fiber positioning systems. These systems rely on precise fiber placement to detect the light spectra of many stars and galaxies. One successful approach is the use of robotic fiber Positioners, which allow one to automate and scale up observations. However, due to the need for high precision and accuracy, each Positioner must be calibrated and verified to comply with the requirements. The calibration measurements are nontrivial, and the large number of the robotic Positioners up to thousands can lead to a prohibitively long time for calibration. We describe and validate an optical calibration setup and procedure for robotic fiber positioning systems. Based on the measurements results, we have developed models describing the behavior of the Positioners and we introduce new performance metrics that allow one to verify the stringent Positioner specifications and furthermore help to identify and analyze design and manufacturing flaws.
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priority coordination of fiber Positioners in multi objects spectrographs
Ground-based and Airborne Instrumentation for Astronomy VII, 2018Co-Authors: Laleh Makarem, J P Kneib, Mohamed Bouri, Denis GilletAbstract:Projects such as "The Dark Energy Spectroscopic Instrument” (DESI) [4] or ”The Multi Object Optical and Near-infrared Spectrograph” (MOONS ) [5] are developing spectrographs, composed of more than thousand of optical fibers in a confined hexagonal focal plane, to study the evolution of the universe. Such systems allow fast reconfiguration of the fibers as they are moved simultaneously to their assigned target by a 2-arm Positioner within an short interval of time. Moreover, astronomers prioritize the observation of some objects over those that hold less information, creating a hierarchy of importances or priorities. In a scenario where not all the Positioners can reach their targets, It is important to ensure the observation of the high-priority targets. In previous works, a decentralized navigation function from the family of potential fields was used for collisionfree coordination. While it guarantees convergence of all the Positioners to their targets for DESI [1,2], it fails at planning motion for Positioners in MOONS [3]. The reason is that the second arm of the Positioners in MOONS is two times the length of the first arm. Covering a larger working space, they are prone to deadlocks, a situation where two or more Positioners are blocked by each other and so unable to reach their targets. In this paper and in the framework of MOONS project, we present our new approach to integrate assigned priorities with the decentralized navigation functions to reduce the deadlocks situations. For this purpose, we regulate the movements of the Positioners using a finite-state machine combined with distance-based heuristics. Each Positioner’s state dictates its behaviors with respect to other Positioners. Distance-based heuristics limit the states transition when a Positioner is interacting with its adjacent Positioners to localize possible deadlock situations. The advantage of this method is its simplicity as it relies on local interaction of Positioners, keeping the complexity of the algorithm quasilinear. In addition, since it does not depend on the Positioner’s geometry, it is also scalable to other Positioner kinematics. We developed a motion planning simulator with a graphic interface in python to validate the coordination of the Positioners with assigned priorities. As a result, the number of Positioners converging to their targets improve from 60-70% to 80-95%. The computation time of the trajectories increases slightly due to the new layer of algorithm added for deadlocks prevention.
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collision free motion planning for fiber Positioner robots discretization of velocity profiles
Proceedings of SPIE, 2014Co-Authors: Laleh Makarem, J P Kneib, Denis Gillet, Hannes Bleuler, Mohamed Bouri, Philippe Horler, Laurent Jenni, F Prada, Justo SanchezAbstract:The next generation of large-scale spectroscopic survey experiments such as DESI, will use thousands of fiber Positioner robots packed on a focal plate. In order to maximize the observing time with this robotic system we need to move in parallel the fiber-ends of all Positioners from the previous to the next target coordinates. Direct trajectories are not feasible due to collision risks that could undeniably damage the robots and impact the survey operation and performance. We have previously developed a motion planning method based on a novel decentralized navigation function for collision-free coordination of fiber Positioners. The navigation function takes into account the configuration of Positioners as well as their envelope constraints. The motion planning scheme has linear complexity and short motion duration (2.5 seconds with the maximum speed of 30 rpm for the Positioner), which is independent of the number of Positioners. These two key advantages of the decentralization designate the method as a promising solution for the collision-free motion-planning problem in the next-generation of fiber-fed spectrographs. In a framework where a centralized computer communicates with the Positioner robots, communication overhead can be reduced significantly by using velocity profiles consisting of a few bits only. We present here the discretization of velocity profiles to ensure the feasibility of a real-time coordination for a large number of Positioners. The modified motion planning method that generates piecewise linearized position profiles guarantees collision-free trajectories for all the robots. The velocity profiles fit few bits at the expense of higher computational costs.
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Collision avoidance in next-generation fiber Positioner robotic systems for large survey spectrographs
Astronomy and Astrophysics - A&A, 2014Co-Authors: Laleh Makarem, J P Kneib, Denis Gillet, Hannes Bleuler, Mohamed Bouri, Laurent Jenni, F Prada, Justo SanchezAbstract:Some of the next-generation massive spectroscopic survey projects plan to use thousands of fiber Positioner robots packed at a focal plane to quickly move the fiber ends in parallel from the previous to the next target points. The most direct trajectories are prone to collision that could damage the robots and have an impact on the survey operation. We thus present here a motion planning method based on a novel decentralized navigation function for collision-free coordination of fiber Positioners. The navigation function takes into account the configuration of Positioners as well as the actuator constraints. We provide details of the proof of convergence and collision avoidance. Decentralization results in linear complexity for the motion planning as well as no dependence of motion duration on the number of Positioners. Therefore, the coordination method is scalable for large-scale spectrograph robots. The short in-motion duration of Positioner robots will thus allow the time dedicated for observation to be maximized.
Justo Sanchez - One of the best experts on this subject based on the ideXlab platform.
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collision free motion planning for fiber Positioner robots discretization of velocity profiles
Proceedings of SPIE, 2014Co-Authors: Laleh Makarem, J P Kneib, Denis Gillet, Hannes Bleuler, Mohamed Bouri, Philippe Horler, Laurent Jenni, F Prada, Justo SanchezAbstract:The next generation of large-scale spectroscopic survey experiments such as DESI, will use thousands of fiber Positioner robots packed on a focal plate. In order to maximize the observing time with this robotic system we need to move in parallel the fiber-ends of all Positioners from the previous to the next target coordinates. Direct trajectories are not feasible due to collision risks that could undeniably damage the robots and impact the survey operation and performance. We have previously developed a motion planning method based on a novel decentralized navigation function for collision-free coordination of fiber Positioners. The navigation function takes into account the configuration of Positioners as well as their envelope constraints. The motion planning scheme has linear complexity and short motion duration (2.5 seconds with the maximum speed of 30 rpm for the Positioner), which is independent of the number of Positioners. These two key advantages of the decentralization designate the method as a promising solution for the collision-free motion-planning problem in the next-generation of fiber-fed spectrographs. In a framework where a centralized computer communicates with the Positioner robots, communication overhead can be reduced significantly by using velocity profiles consisting of a few bits only. We present here the discretization of velocity profiles to ensure the feasibility of a real-time coordination for a large number of Positioners. The modified motion planning method that generates piecewise linearized position profiles guarantees collision-free trajectories for all the robots. The velocity profiles fit few bits at the expense of higher computational costs.
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Collision avoidance in next-generation fiber Positioner robotic systems for large survey spectrographs
Astronomy and Astrophysics - A&A, 2014Co-Authors: Laleh Makarem, J P Kneib, Denis Gillet, Hannes Bleuler, Mohamed Bouri, Laurent Jenni, F Prada, Justo SanchezAbstract:Some of the next-generation massive spectroscopic survey projects plan to use thousands of fiber Positioner robots packed at a focal plane to quickly move the fiber ends in parallel from the previous to the next target points. The most direct trajectories are prone to collision that could damage the robots and have an impact on the survey operation. We thus present here a motion planning method based on a novel decentralized navigation function for collision-free coordination of fiber Positioners. The navigation function takes into account the configuration of Positioners as well as the actuator constraints. We provide details of the proof of convergence and collision avoidance. Decentralization results in linear complexity for the motion planning as well as no dependence of motion duration on the number of Positioners. Therefore, the coordination method is scalable for large-scale spectrograph robots. The short in-motion duration of Positioner robots will thus allow the time dedicated for observation to be maximized.
