1,720,987 research outputs found
Cooperative transportation of a payload using quadrotors: a reconfigurable cable-driven parallel robot
No full textThis paper addresses the problem of cooperative aerial transportation of an object using a team of quadrotors. The approach presented to solve this problem accounts for the full dynamics of the system and it is inspired by the literature on reconfigurable cable-driven parallel robots (RCDPR). Using the modelling convention of RCDPR it is derived a direct relation between the motion of the quadrotors and the motion of the payload. This relation makes explicit the available internal motion of the system, which can be used to automatically achieve additional tasks. The proposed method does not require to specify a priory the forces in the cables and uses a tension distribution algorithm to optimally distribute them among the robots. The presented framework is also suitable for online teleoperation. Physical simulations with a human-in-the-loop validate the proposed approach
Robust adaptive sliding mode control of a redundant cable driven parallel robot
No full textIn this paper we consider the application problem of a redundant cable-driven parallel robot, tracking a reference trajectory in presence of uncertainties and disturbances. A Super Twisting controller is implemented using a recently proposed gains adaptation law [1], thus not requiring the knowledge of the upper bound of the lumped uncertainties. The controller is extended by a feedforward dynamic inversion control that reduces the effort of the sliding mode controller. Compared to a recently developed Adaptive Terminal Sliding Mode Controller for cable-driven parallel robots [2], the proposed controller manages to achieve lower tracking errors and less chattering in the actuation forces even in presence of perturbations. The system is implemented and tested in simulation using a model of a large redundant cable-driven robot and assuming noisy measurements. Simulations show the effectiveness of the proposed method
Erratum: A passivity-based decentralized strategy for generalized connectivity maintenance (International Journal of Robotics Research (2013) 32:3 (299-323) DOI:10.1177/0278364912469671)
No full textPaolo Robuffo Giordano, Antonio Franchi, Cristian Secchi and Heinrich H Bulthoff A Passivity-Based Decentralized Strategy for Generalized Connectivity Maintenance The International Journal of Robotics Research, Vol. 32(3): pp. 299-323 (2013) DOI: 10.1177/0278364912469671 Please note that several errors were introduced to this article during copy editing. These were pointed out by the authors but unfortunately due to a publisher error were not corrected. SAGE Publications would like to apologise to the authors and readers for these errors: Third author Cristian Secchi's name was incorrectly spelt Christian Seccos. In the following places pacifying' should be passifying': Page 310 right hand column, 2nd paragraph Page 310, right hand column, 2nd paragraph Page 311, right hand column, last paragraph Page 312 left hand column, 2nd paragraph In the following places ith' should be i-th': Page 302, right hand column, 3(rd) paragraph, twice on the 20(th) line Page 306, left hand column, 1st paragraph, 9(th) line after equation 12 Page 306, right hand column, 1st paragraph, 15(th) line Page 307, right hand column, 2(nd) line after Figure 7 Page 309, right hand column, 2nd paragraph, 6(th) line Page 309, right hand column, 3rd paragraph, 12(th) line Page 310, left hand column, 1(st) paragraph in numbered list, 3(rd) line Page 313, left hand column, 1(st) paragraph, 9(th) line after equation 40. In the following places kth' should be k-th': Page 307, left hand column, last line Page 308, right hand column, 2(nd) paragraph, 4(th) line In the following places hth' should be h-th': Page 308, left hand column, 1(st) line after equation 21 In the following places jth' should be j-th: Page 309, right hand column, 2(nd) paragraph, 7(th) line In the following places one-hop' should be 1-hop': Page 303, right hand column, 1(st) 3rd line from top Page 308, right hand column, 3(rd) line below equation 27 and last line Page 309, left hand column, 4(th) paragraph, last line Page 309, right hand column, 3(rd) line from top Page 309, right hand column, 1(st) paragraph, last line Page 309, right hand column, 3(rd) paragraph, 2nd lin
Interactive planning of persistent trajectories for human-assisted navigation of mobile robots
No full textThis work extends the framework of bilateral shared control of mobile robots with the aim of increasing the robot autonomy and decreasing the operator commitment. We consider persistent autonomous behaviors where a cyclic motion must be executed by the robot. The human operator is in charge of modifying online some geometric properties of the desired path. This is then autonomously processed by the robot in order to produce an actual path guaranteeing: i) tracking feasibility, ii) collision avoidance with obstacles, iii) closeness to the desired path set by the human operator, and iv) proximity to some points of interest. A force feedback is implemented to inform the human operator of the global deformation of the path rather than using the classical mismatch between desired and executed motion commands. Physically-based simulations, with human/hardware-in-the-loop and a quadrotor UAV as robotic platform, demonstrate the feasibility of the method. © 2012 IEEE
Mechanical design and control of the new 7-DOF CyberMotion Simulator
No full textThis paper describes the mechanical and control design of the new 7-DOF CyberMotion Simulator, a redundant industrial manipulator arm consisting of a standard 6-DOF anthropomorphic manipulator plus an actuated cabin attached to the end-effector. Contrarily to Stewart platforms, an industrial manipulator offers several advantages when used as motion simulator: larger motion envelope, higher dexterity, and possibility to realize any end-effector posture within the workspace. In addition to this, the new actuated cabin acts as an additional joint and provides the needed kinematic redundancy to cope with the robot actuator and joint range constraints, which in general can significantly deteriorate the desired motion cues the robot is reproducing. In particular, we will show that, by suitably exploiting the redundancy better results can be obtained in reproducing sustained acceleration cues, a relevant problem when implementing vehicle simulators. © 2011 IEEE
Application of a differentiator-based adaptive super-twisting controller for a redundant cable-driven parallel robot
Full text linkIn this paper we present preliminary, experimental results of an Adaptive Super-Twisting Sliding-Mode Controller with time-varying gains for redundant Cable-Driven Parallel Robots. The sliding-mode controller is paired with a feed-forward action based on dynamics inversion. An exact sliding-mode differentiator is implemented to retrieve the velocity of the end-effector using only encoder measurements with the properties of finite-time convergence, robustness against perturbations and noise filtering. The platform used to validate the controller is a robot with eight cables and six degrees of freedom powered by 940 W compact servo drives. The proposed experiment demonstrates the performance of the controller, finite-time convergence and robustness in tracking a trajectory while subject to external disturbances up to approximately 400% the mass of the end-effector
Adaptive super twisting controller for a quadrotor UAV
No full textIn this paper we present a robust quadrotor controller for tracking a reference trajectory in presence of uncertainties and disturbances. A Super Twisting controller is implemented using the recently proposed gain adaptation law [1], [2], which has the advantage of not requiring the knowledge of the upper bound of the lumped uncertainties. The controller design is based on the regular form of the quadrotor dynamics, without separation in two nested control loops for position and attitude. The controller is further extended by a feedforward dynamic inversion control that reduces the effort of the sliding mode controller. The higher order quadrotor dynamic model and proposed controller are validated using a SimMechanics physical simulation with initial error, parameter uncertainties, noisy measurements and external perturbations
Bilateral teleoperation of multiple UAVs with decentralized bearing-only formation control
No full textWe present a decentralized system for the bilateral teleoperation of groups of UAVs which only relies on relative bearing measurements, i.e., without the need of distance information or global localization. The properties of a 3D bearing-formation are analyzed, and a minimal set of bearings needed for its definition is provided. We also design a novel decentralized formation control almost globally convergent and able to maintain bounded and non-vanishing inter-distances among the agents despite the absence of direct distance measurements. Furthermore, we develop a multi-master/multi-slave teleoperation setup in order to control the overall behavior of the group and to convey to the human operator suitable force cues, while ensuring stability in presence of delays and packet losses over the master-slave communication channel. The theoretical framework is validated by means of extensive human/hardware in-the-loop simulations using two force-feedback devices and a group of quadrotors. © 2011 IEEE
Modeling and analysis of cable vibrations for a cable-driven parallel robot
No full textIn this paper we study if approximated linear models are accurate enough to predict the vibrations of a cable of a Cable-Driven Parallel Robot (CDPR) for different pretension levels. In two experiments we investigated the damping of a thick steel cable from the Cablerobot simulator [1] and measured the motion of the cable when a sinusoidal force is applied at one end of the cable. Using this setup and power spectral density analysis we measured the natural frequencies of the cable and compared these results to the frequencies predicted by two linear models: i) the linearization of partial differential equations of motion for a distributed cable, and ii) the discretization of the cable using a finite elements model. This comparison provides remarkable insights into the limits of approximated linear models as well as important properties of vibrating cables used in CDPR
Aerial physical interaction via IDA-PBC
No full textThis paper proposes the use of a novel control method based on interconnection and damping assignment–passivity-based control (IDA-PBC) in order to address the aerial physical interaction (APhI) problem for a quadrotor unmanned aerial vehicle (UAV). The apparent physical properties of the quadrotor are reshaped in order to achieve better APhI performances, while ensuring the stability of the interaction through passivity preservation. The robustness of the IDA-PBC method with respect to sensor noise is also analyzed. The direct measurement of the external wrench, needed to implement the control method, is compared with the use of a nonlinear Lyapunov-based wrench observer and advantages/disadvantages of both methods are discussed. The validity and practicability of the proposed APhI method is evaluated through experiments, where for the first time in the literature, a lightweight all-in-one low-cost force/torque (F/T) sensor is used onboard of a quadrotor. Two main scenarios are shown: a quadrotor responding to external disturbances while hovering (physical human–quadrotor interaction), and the same quadrotor sliding with a rigid tool along an uneven ceiling surface (inspection/painting-like task)
- …
