Cooperative Dynamic Manipulation of Unknown Flexible Objects

International Journal of Social Robotics, Jun 2017

Cooperative dynamic manipulation enlarges the manipulation repertoire of human–robot teams. By means of synchronized swinging motion, a human and a robot can continuously inject energy into a bulky and flexible object in order to place it onto an elevated location and outside the partners’ workspace. Here, we design leader and follower controllers based on the fundamental dynamics of simple pendulums and show that these controllers can regulate the swing energy contained in unknown objects. We consider a complex pendulum-like object controlled via acceleration, and an “arm—flexible object—arm” system controlled via shoulder torque. The derived fundamental dynamics of the desired closed-loop simple pendulum behavior are similar for both systems. We limit the information available to the robotic agent about the state of the object and the partner’s intention to the forces measured at its interaction point. In contrast to a leader, a follower does not know the desired energy level and imitates the leader’s energy flow to actively contribute to the task. Experiments with a robotic manipulator and real objects show the efficacy of our approach for human–robot dynamic cooperative object manipulation.

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Cooperative Dynamic Manipulation of Unknown Flexible Objects

Cooperative Dynamic Manipulation of Unknown Flexible Objects Joint Energy Injection Based on Simple Pendulum Fundamental Dynamics 0 1 2 Philine Donner 0 1 2 Franz Christange 0 1 2 Jing Lu 0 1 2 Martin Buss 0 1 2 0 Department of Electrical and Computer Engineering, Chair of Renewable and Sustainable Energy Systems (ENS), Technical University of Munich , Munich , Germany 1 Institute for Advanced Study, Technical University of Munich , Munich , Germany 2 Department of Electrical and Computer Engineering, Chair of Automatic Control Engineering (LSR), Technical University of Munich , Munich , Germany Cooperative dynamic manipulation enlarges the manipulation repertoire of human-robot teams. By means of synchronized swinging motion, a human and a robot can continuously inject energy into a bulky and flexible object in order to place it onto an elevated location and outside the partners' workspace. Here, we design leader and follower controllers based on the fundamental dynamics of simple pendulums and show that these controllers can regulate the swing energy contained in unknown objects. We consider a complex pendulum-like object controlled via acceleration, and an “arm-flexible object-arm” system controlled via shoulder torque. The derived fundamental dynamics of the desired closed-loop simple pendulum behavior are similar for both systems. We limit the information available to the robotic agent about the state of the object and the partner's intention to the forces measured at its interaction point. In contrast to a leader, a follower does not know the desired energy level and imitates the leader's energy flow to actively contribute to the task. Experiments with a robotic manipulator and real objects show the efficacy of our approach for human-robot dynamic cooperative object manipulation. Physical human-robot interaction; Cooperative manipulators; Adaptive control; Dynamics; Haptics; Intention estimation B Philine Donner 1 Introduction Continuous energy injection during synchronized swinging motion enables a human and a robot to lift a bulky flexible object together onto an elevated location. This example scenario is illustrated in Fig. 1a and combines the advantages of cooperative and dynamic manipulation. Cooperative manipulation allows for the manipulation of heavier and bulkier objects than one agent could manipulate on its own. A commonly addressed physical human–robot collaboration scenario is, e.g., cooperative transport of rigid bulky objects [44]. Such object transport tasks are performed by kinematic manipulation, i.e., the rigid object is rigidly grasped by the manipulators [32]. In contrast, dynamic object manipulation makes use of the object dynamics, with the advantage of an increased manipulation repertoire: simpler end effectors can handle a greater variety of objects faster and outside the workspace of the manipulator. Dynamic manipulation examples are juggling, throwing, catching [29] as well as the manipulation of underactuated mechanisms [8], such as the flexible and the pendulum-like objects in Fig. 1a, b. In this article, we take a first step towards combining the advantages of cooperative and dynamic object manipulaFig. 1 Approach overview: (1) Interpretation of flexible object swinging as a combination of pendulum swinging and rigid object swinging. (2) Approximation of pendulum swinging by the t-pendulum with 1D acceleration inputs and of flexible object swinging by the afa-system with 1D torque inputs. (3) Projection of the t-pendulum and the afation by investigating cooperative swinging of underactuated objects. The swinging motion naturally synchronizes the motion of the cooperating agents. Energy can be injected in a favorable arm configuration for a human interaction partner (stretched arm) and task effort can be shared among the agents. Moreover, the accessible workspace of the human arm and robotic manipulator is increased by the swinging motion of the object and by a possible subsequent throwing phase. In order to approach the complex task of cooperative flexible object swinging in Fig. 1a, we split it up into its two extremes, which are swinging of pendulum-like objects which oscillate themselves (b) and swinging of rigid objects, where the agents’ arms together with the rigid object form an oscillating entity (c). In our initial work, we treated pendulum-like object swinging [13] based on the assumption that all system parameters are known. This assumption was alleviated in [14] by an adaptive approach. The contribution of this work is three-fold: firstly, we experimentally verify the adaptive approach presented in [14]. Secondly, we combine our results from cooperative swinging of pendulum-like objects and human–human swinging of rigid objects in [15], towards cooperative swinging of flexible objects. Our third contribution lies in the unified presentation of modeling the desired oscillation of pendulum-like and flexible objects through simple pendulum abstractio (...truncated)


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Philine Donner, Franz Christange, Jing Lu, Martin Buss. Cooperative Dynamic Manipulation of Unknown Flexible Objects, International Journal of Social Robotics, 2017, pp. 1-25, DOI: 10.1007/s12369-017-0415-x