Robust trajectory design for object throwing based on sensitivity for model uncertainties

Okada, Masafumi; Pekarovskiy, Alexander; Buss, Martin

doi:10.1109/icra.2015.7139623

Cited by 8 publications

(7 citation statements)

References 7 publications

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“…• optimizing the robot trajectory in order to reduce the discontinuity (in the rigid-body model) of cable tensions at the launch instant, which may cause oscillations after launch; • studying tension fluctuations that are triggered, in the elastic model, even before the launch (see Figure 6); • analyzing the sensitivity of the final position of the launched object to errors in the actual launch position and velocity with respect to their ideal values, similarly to the works presented in [11,27]; • considering the effect of air drag; the trajectory of a point-mass object in free-flight through a viscous medium is described by differential equations that generally do not allow closed-form solutions, but some authors [29] propose tractable models that approximate the real solution; • experimentally validating our results by tests on a prototype (currently under development).…”

Section: Discussionmentioning

confidence: 99%

“…The trajectory planning of the launched mass requires some simplifying assumptions. Most authors [13][14][15][16][17]19,21,[25][26][27][31][32][33][34][36][37][38][39] consider a simplified model where, during the free-flight phase, the only force acting is gravity; under these assumptions, it can be readily shown that the center of mass of the launched object will move along a parabolic arc in a vertical plane. Considering the effect of air drag leads to a more realistic model; however, the dynamic problem including the air-drag model does not have a closed-form solution.…”

Section: Launch Trajectory Planningmentioning

confidence: 99%

“…A more general trajectory design approach for n-link manipulators was introduced in [26]: the algorithm considers both kinematic and dynamic constraints, and finds a solution (if any) with a known probability. Finally, the sensitivity of the launch trajectory was considered in [27], where the authors showed how to find the optimal launch trajectory in order to minimize the variance of the landing-point position.…”

Section: Introductionmentioning

confidence: 99%

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Modeling and Control of a Cable-Suspended Sling-Like Parallel Robot for Throwing Operations

et al. 2020

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Cable-driven parallel robots can provide interesting advantages over conventional robots with rigid links; in particular, robots with a cable-suspended architecture can have very large workspaces. Recent research has shown that dynamic trajectories allow the robot to further increase its workspace by taking advantage of inertial effects. In our work, we consider a three-degrees-of-freedom parallel robot suspended by three cables, with a point-mass end-effector. This model was considered in previous works to analyze the conditions for dynamical feasibility of a trajectory. Here, we enhance the robot’s capabilities by using it as a sling, that is, by throwing a mass at a suitable time. The mass is carried at the end-effector by a gripper, which releases the mass so that it can reach a given target point. Mathematical models are presented that provide guidelines for planning the trajectory. Moreover, results are shown from simulations that include the effect of cable elasticity. Finally, suggestions are offered regarding how such a trajectory can be optimized.

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Section: Discussionmentioning

confidence: 99%

Section: Launch Trajectory Planningmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Modeling and Control of a Cable-Suspended Sling-Like Parallel Robot for Throwing Operations

et al. 2020

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“…2) Throw specific objects vs. throw generic objects: The majority of previous approaches to throwing were limited to throwing one specific object type ( [1]: a wooden block; [2]- [4], [6], [13], [18]- [20]: a ball; [5]: a square plastic plate; [15], [17]: heavy boxes). In contrast, two recent approaches targeted throwing of a variety of generic objects [8], [9], We review these next.…”

Section: Specific Objectmentioning

confidence: 99%

Tube Acceleration: Robust Dexterous Throwing Against Release Uncertainty

Liu,

Billard

2024

IEEE Trans. Robot.

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In robotic throwing, the release phase involves complex dynamic interactions due to object deformation and limited gripper opening speed, often resulting in inaccurate and nonrepeatable throws. While data-driven methods can be employed to compensate for the release uncertainty, the generalizability of learned models to unseen objects is not guaranteed, and object-specific fine-tuning with new data may be required. This fine-tuning process raises concerns about the scalability of such methods for dexterous throwing, where the robot needs to execute diverse motions for throwing various objects. Instead of case-bycase fine-tuning, we aim at designing throwing motion robust against release uncertainty. We encapsulate all uncertainties resulting from complex contact dynamics in a surrogate model of their resulting effect on gripper opening delay. We introduce the notion of tube acceleration to model the class of constantacceleration motion in joint space that guarantees a release within the set of valid throwing configurations. We propose a convex relaxation of the primal optimization problem with a tight error bound and evaluate its performance in terms of reliability and efficiency. Results show that the approach offers run-time performance to allow online computation of throws on a 7-DoF robot arm. It achieves a high accuracy and success rate (97% for planar throws) at throwing a variety of complex objects, even when using a simple ballistic model for the object's flying dynamics.

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“…On the other hand, Okada (Okada et al, 2015) has proposed sensitivity analysis for a dynamical system, and designed a robust throwing motion with small sensitivity. Moreover, their method has been experimentally evaluated (Okada et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Throwing motion design based on minimum sensitivity with respect to error covariance of robot dynamic parameters

Okada

Sekiguchi

2021

Mechanical Engineering Journal

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Throwing by a powered manipulator is an effective way for wide range transportation of an object and carrying an object in unmanned environments. The main problems of throwing are (i) how far the manipulator can throw the object and (ii) the accuracy of the landing position. Focusing on (ii), this paper proposes sensitivity analysis of the landing position with respect to the error covariance of dynamic parameters. Focusing on a planar 3-DOF manipulator, (1) the minimum set of dynamic parameters is introduced and identified based on a frequency weighted method for a nonlinear system, and its error covariance is also identified. (2) The calculation algorithm for sensitivity of landing position with respect to the minimum set of dynamic parameters is proposed. (3) By considering the error covariance of identification, an optimal throwing is designed and evaluated by simulations and/or experiments. Moreover, (4) the principal of sensitivity analysis is discussed from error ellipsoid point of view, and zero error throwing is designed.

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Robust trajectory design for object throwing based on sensitivity for model uncertainties

Cited by 8 publications

References 7 publications

Modeling and Control of a Cable-Suspended Sling-Like Parallel Robot for Throwing Operations

Modeling and Control of a Cable-Suspended Sling-Like Parallel Robot for Throwing Operations

Tube Acceleration: Robust Dexterous Throwing Against Release Uncertainty

Throwing motion design based on minimum sensitivity with respect to error covariance of robot dynamic parameters

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