Geometrical Interpretation and Detection of Multiple Task Conflicts using a Coordinate Invariant Index

Schettino, Vincenzo; Fiore, Mario D.; Pecorella, Claudia; Ficuciello, Fanny; Allmendinger, Felix; Lachner, Johannes; Siciliano, Bruno

doi:10.1109/iros45743.2020.9340690

Cited by 9 publications

(8 citation statements)

References 45 publications

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“…Second, this experiment was specifically designed to make the task conflict easy to quantify. However, if more complex tasks are to be understood, alternative metrics for quantifying task conflicts may be required [89].…”

Section: Future Workmentioning

confidence: 99%

Exploiting Redundancy to Facilitate Physical Interaction

et al. 2022

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The control of kinematically redundant robots is often approached using nullspace projection, which requires precise models and can be computationally challenging. Humans have many more degrees of freedom than are required to accomplish their tasks, but given neuro-mechanical limitations, it seems unlikely that biology relies on precise models or complex computation. An alternative biologically-inspired approach leverages the compositionality of mechanical impedance. In theory, nullspace projection eliminates any conflict between two tasks. In contrast, superposition of task-space impedance and a full-rank joint-space impedance may impose a task conflict. This work compared nullspace projection with impedance superposition during unconstrained motion and forceful physical interaction. In practice, despite their theoretical differences, we did not observe a substantial influence of the nullspace projector weighting matrix. We found that nullspace projection and impedance superposition both resulted in measurable task conflict. Remarkably, when the dimensionality of the nullspace was increased, impedance superposition was comparable to nullspace projection.

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Section: Future Workmentioning

confidence: 99%

Exploiting Redundancy to Facilitate Physical Interaction

et al. 2022

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“…The choice of H in ( 16) and ( 17) is left to the programmer. However, specific metrics exist, which ensure dynamical consistency of the generated robot motion [37], [38]. Such metrics are used in Section IV-A.…”

Section: Velocity Acceleration Torquementioning

confidence: 99%

“…Proceeding with the analysis of Algorithm 1, it can be easily recognized that the second expensive operation is the update of the solution u k (lines [36][37][38][39]. This requires, at every iteration, the computation of the pseudoinverse of Ĉk = C sat 1→k P k−1 and Âk = A k P k−1 .…”

Section: Fast-esnsmentioning

confidence: 99%

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A General Framework for Hierarchical Redundancy Resolution Under Arbitrary Constraints

Fiore¹,

Meli²,

Ziese³

et al. 2022

Preprint

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The increasing interest in autonomous robots with a high number of degrees of freedom for industrial applications and service robotics demands control algorithms to handle multiple tasks as well as hard constraints efficiently. This paper presents a general framework in which both kinematic (velocity-or acceleration-based) and dynamic (torque-based) control of redundant robots are handled in a unified fashion. The framework allows for the specification of redundancy resolution problems featuring a hierarchy of arbitrary (equality and inequality) constraints, arbitrary weighting of the control effort in the cost function and an additional input used to optimize possibly remaining redundancy. To solve such problems, a generalization of the Saturation in the Null Space (SNS) algorithm is introduced, which extends the original method according to the features required by our general control framework. Variants of the developed algorithm are presented, which ensure both efficient computation and optimality of the solution. Experiments on a KUKA LBRiiwa robotic arm, as well as simulations with a highly redundant mobile manipulator are reported.

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“…For many applications, however, it is crucial that the robot indicates that not all tasks are mutually compatible. Only limited methods exist that can be used during robot operation to predict a task conflict [19].…”

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confidence: 99%

Shaping Impedances to Comply With Constrained Task Dynamics

2022

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Humans are capable of managing multiple tasks simultaneously. It is widely assumed that human motor control can be emulated by impedance control. To achieve human-like behavior, however, the impedance parameters of multiple tasks may vary during task execution. We propose an algorithm that shapes task impedance as a function of the robot's time-varying inertial properties. These properties involve virtually constrained masses and virtually constrained inertias that counteract a task in order to comply with a given constraint. In this work, we not only detect task conflicts, but also show how to handle them. Our method is able to control kinematically redundant robots. We developed a dampingdesign method that does not interfere with our desired Cartesian task-space behavior. The control approach was verified in experiments on a real robot. We compared our impedance shaping method with two alternative control approaches: simple impedance superposition and nullspace projection. Our method preserved the passivity while improving the Cartesian task performance of an impedance controller. The method has computational advantages, beneficial to control robots with many degrees of freedom.

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Geometrical Interpretation and Detection of Multiple Task Conflicts using a Coordinate Invariant Index

Cited by 9 publications

References 45 publications

Exploiting Redundancy to Facilitate Physical Interaction

Exploiting Redundancy to Facilitate Physical Interaction

A General Framework for Hierarchical Redundancy Resolution Under Arbitrary Constraints

Shaping Impedances to Comply With Constrained Task Dynamics

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