A Complementarity Based Contact Model for Geometrically Accurate Treatment of Polytopes in Simulation

Williams, Jedediyah; Lu, Yu; Trinkle, Jeff

doi:10.1115/detc2014-35231

Cited by 7 publications

(4 citation statements)

References 18 publications

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“…Some contact models such as those that combine minimum translational distance and point-contact produce forces that are not continuous functions of state (see, e.g., [18]). This section will show that the normal force produced by the pressure field model is a continuous function of state even in the presence of damping, discretization, and quadrature.…”

Section: Continuous Forces From Discrete Geometrymentioning

confidence: 99%

A pressure field model for fast, robust approximation of net contact force and moment between nominally rigid objects

Elandt¹,

Drumwright²,

Sherman³

et al. 2019

2019 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)

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We introduce Pressure Field Contact (PFC), an approximate model for predicting the contact surface, pressure distribution, and net contact wrench between nominally rigid objects. PFC combines and generalizes two ideas: a bed of springs (an 'elastic foundation') and hydrostatic pressure. Continuous pressure fields are computed offline for the interior of each nominally rigid object. Unlike hydrostatics or elastic foundations, the pressure fields need not satisfy mechanical equilibrium conditions. When two objects nominally overlap, a contact surface is defined where the two pressure fields are equal. This static pressure is supplemented with a dissipative rate-dependent pressure and friction to determine tractions on the contact surface. The contact wrench between pairs of objects is an integral of traction contributions over this surface. PFC evaluates much faster than elasticity-theory models, while showing the essential trends of force, moment, and stiffness increase with contact load. It yields continuous wrenches even for non-convex objects and coarse meshes. The method shows promise as sufficiently fast, accurate, physical, and robust for robotics applications including motion and tactile sensor simulation, controller learning and synthesis, state estimation, and design-in-simulation.

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Section: Continuous Forces From Discrete Geometrymentioning

confidence: 99%

A pressure field model for fast, robust approximation of net contact force and moment between nominally rigid objects

Elandt¹,

Drumwright²,

Sherman³

et al. 2019

2019 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)

View full text Add to dashboard Cite

show abstract

“…2a. The collision detection stage predicts contact points (where to contact) and time of impact (when to contact) using efficient algorithms (van den Bergen, 2003;Williams et al, 2014). When collision is predicted within a simulation time step, the collision response stage computes the impulse from the collision.…”

Section: Bullet Physics Enginementioning

confidence: 99%

Virtual Shake Robot: Simulating Dynamics of Precariously Balanced Rocks for Overturning and Large-displacement Processes

Chen,

Arrowsmith,

Das

et al. 2024

Seismica

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Understanding the dynamics of precariously balanced rocks (PBRs) is important for seismic hazard analysis and rockfall prediction. Utilizing a physics engine and robotic tools, we develop a virtual shake robot (VSR) to simulate the dynamics of PBRs during overturning and large-displacement processes. We present the background of physics engines and technical details of the VSR, including software architecture, mechanical structure, control system, and implementation procedures. Validation experiments show the median fragility contour from VSR simulation is within the 95% prediction intervals from previous physical experiments, when PGV/PGA is greater than 0.08 s. Using a physical mini shake robot, we validate the qualitative consistency of fragility anisotropy between the VSR and physical experiments. By overturning cuboids on flat terrain, the VSR reveals the relationship between fragility and geometric dimensions (e.g., aspect and scaling ratios). The ground motion orientation and lateral pedestal support affect PBR fragility. Large-displacement experiments estimate rock trajectories for different ground motions, which is useful for understanding the fate of toppled PBRs. Ground motions positively correlate with large displacement statistics such as mean trajectory length, mean largest velocity, and mean terminal distance. The overturning and large displacement processes of PBRs provide complementary methods of ground motion estimation.

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“…The latter three cases, which are fortunately rare, are not treated in the present work to avoid overly constraining the motion; these cases can at least be detected and reported, however. This issue is discussed at depth in [24].…”

Section: Computing the Contact Event Timesmentioning

confidence: 99%

True Rigidity: Interpenetration-free Multi-Body Simulation with Polytopic Contact

Drumwright

2016

Preprint

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An effective paradigm for simulating the dynamics of robots that locomote and manipulate is multi-rigid body simulation with rigid contact. This paradigm provides reasonable tradeoffs between accuracy, running time, and simplicity of parameter selection and identification. The Stewart-Trinkle/Anitescu-Potra "time stepping" approach is the basis of many existing implementations. It successfully treats inconsistent (Painlevé-type) contact configurations, efficiently handles many contact events occurring in short time intervals, and provably converges to the solution of the continuous time differential algebraic equations (DAEs) as the integration step size tends to zero. However, there is currently no means to determine when the solution has largely converged, i.e., when smaller integration steps would result in only small increases in accuracy. The present work describes an approach that computes the event times (when the set of active equations in a DAE changes) of all contact/impact events for a multi-body simulation, toward using integration techniques with error control to compute a solution with desired accuracy. We also describe a first-order, variable integration approach that ensures that rigid bodies with convex polytopic geometries never interpenetrate. This approach permits taking large steps when possible and takes small steps when contact is complex.

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A Complementarity Based Contact Model for Geometrically Accurate Treatment of Polytopes in Simulation

Cited by 7 publications

References 18 publications

A pressure field model for fast, robust approximation of net contact force and moment between nominally rigid objects

A pressure field model for fast, robust approximation of net contact force and moment between nominally rigid objects

Virtual Shake Robot: Simulating Dynamics of Precariously Balanced Rocks for Overturning and Large-displacement Processes

True Rigidity: Interpenetration-free Multi-Body Simulation with Polytopic Contact

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