A Transition-Aware Method for the Simulation of Compliant Contact With Regularized Friction

Castro, Alejandro; Qu, Ante; Kuppuswamy, Naveen; Alspach, Alex; Sherman, Michael

doi:10.1109/lra.2020.2969933

Cited by 19 publications

(11 citation statements)

References 21 publications

(27 reference statements)

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“…The formulation of (5) naturally induces a fix point algorithm to solve for λ t+1 t and λ t+1 n . Finally, by fixing the number of fix point iterations to n step (a convergence analysis similar to [15] finds n step ∈ [3,10] to have reasonable computation time and a precision sufficient for most of applications) , λ t+1 t and λ t+1 n can be computed by solving a sequence of optimization problems alternating between a QP and a QCQP (at lines 8 and 10 of Algo. 1).…”

Section: A Solving the Frictional Contact Problemmentioning

confidence: 99%

“…Modeling frictional contacts is one of the most challenging aspect of physical simulations given the non-linearity and non-convexity of complementarity constraint and the maximum dissipation principle. These underlying physical laws of rigid contact dynamics are typically simplified (springdamper [10]), approximated [11] or relaxed [12] in classic physics engines. These choices aim to increase computational efficiency but may also result in non-realistic behaviors in simulation [13].…”

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confidence: 99%

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Differentiable Simulation for Physical System Identification

Lidec

Kalevatykh

Laptev

et al. 2021

IEEE Robot. Autom. Lett.

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Section: A Solving the Frictional Contact Problemmentioning

confidence: 99%

mentioning

confidence: 99%

Differentiable Simulation for Physical System Identification

Lidec

Kalevatykh

Laptev

et al. 2021

IEEE Robot. Autom. Lett.

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show abstract

“…With implicit integration, stability theory says we should be able to take large time steps even for very stiff ODEs. However, doing so in practice has proven difficult [14].…”

Section: Introductionmentioning

confidence: 99%

Discrete Approximation of Pressure Field Contact Patches

Masterjohn¹,

Guoy²,

Shepherd³

et al. 2021

Preprint

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Rich interaction with the world requires extensive contact between robots and the objects in their environment. Most such contacts involve significant compliance between the contacting surfaces due to rubber pads or inflated grippers, soft objects to be manipulated, and soft surfaces for safe human-robot interaction. Accurate simulation of these contacts is critical for meaningful sim-to-real transfer. Compliant contact interactions generate contact surfaces of considerable extent, over which contact forces are distributed with varying pressure. Finite element methods can capture these effects but are too slow for most robotics applications. Consequently, in order to enable real-time simulation rates, most current simulation tools model contact as occurring between rigid bodies at a point or set of points using ad hoc methods to incorporate localized compliance. However, point contact is non-smooth, hard to extend to arbitrary geometry, and often introduces nonphysical artifacts. Moreover, point contact misses important area-dependent phenomena critical for robust manipulation, such as net contact moment and slip control. Pressure Field Contact (PFC) was recently introduced as a method for detailed modeling of contact interface regions at rates much faster than elasticity-theory models, while at the same time predicting essential trends and capturing rich contact behavior. PFC was designed to work with coarsely-meshed objects while preserving continuity to permit use with error-controlled integrators. Here we introduce a discrete approximation of PFC suitable for use with velocity-level time steppers that enables execution at realtime rates. We evaluate the accuracy and performance gains of our approach and demonstrate its effectiveness in simulation of relevant manipulation tasks. The method is available in open source as part of Drake's Hydroelastic Contact model.

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“…modelling. A number of contact models are established [3,4], and rigid-body contact can typically be simulated with the help of special integrators [5,6]. Methods for model-based trajectory planning over contact continue to improve, both optimization- [7] and particle-based [8].…”

Section: Introductionmentioning

confidence: 99%

Contact Information Flow and Design of Compliance

Haninger¹,

Radke²,

Hartisch³

et al. 2021

Preprint

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e objective of many contact-rich manipulation tasks can be expressed as desired contacts between environmental objects. Simulation and planning for rigid-body contact continues to advance, but the achievable performance is signi cantly impacted by hardware design, such as physical compliance and sensor placement. Much of mechatronic design for contact is done from a continuous controls perspective (e.g. peak collision force, contact stability), but hardware also a ects the ability to infer discrete changes in contact. Robustly detecting contact state can support the correction of errors, both online and in trial-and-error learning.Here, discrete contact states are considered as changes in environmental dynamics, and the ability to infer this with proprioception (motor position and force sensors) is investigated. A metric of information gain is proposed, measuring the reduction in contact belief uncertainty from force/position measurements, and developed for fully-and partially-observed systems. e information gain depends on the coupled robot/environment dynamics and sensor placement, especially the location and degree of compliance. Hardware experiments over a range of physical compliance conditions validate that information gain predicts the speed and certainty with which contact is detected in (i) monitoring of contact-rich assembly and (ii) collision detection. Compliant environmental structures are then optimized to allow industrial robots to achieve safe, higher-speed contact.

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A Transition-Aware Method for the Simulation of Compliant Contact With Regularized Friction

Cited by 19 publications

References 21 publications

Differentiable Simulation for Physical System Identification

Differentiable Simulation for Physical System Identification

Discrete Approximation of Pressure Field Contact Patches

Contact Information Flow and Design of Compliance

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