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203
Engineering and economic applications of complementarity problems
 SIAM REVIEW
, 1997
"... This paper gives an extensive documentation of applications of finitedimensional nonlinear complementarity problems in engineering and equilibrium modeling. For most applications, we describe the problem briefly, state the defining equations of the model, and give functional expressions for the c ..."
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Cited by 195 (24 self)
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This paper gives an extensive documentation of applications of finitedimensional nonlinear complementarity problems in engineering and equilibrium modeling. For most applications, we describe the problem briefly, state the defining equations of the model, and give functional expressions for the complementarity formulations. The goal of this documentation is threefold: (i) to summarize the essential applications of the nonlinear complementarity problem known to date, (ii) to provide a basis for the continued research on the nonlinear complementarity problem, and (iii) to supply a broad collection of realistic complementarity problems for use in algorithmic experimentation and other studies.
GraspIt!  A Versatile Simulator for Robotic Grasping
, 2004
"... Research in robotic grasping has flourished in the last 25 years. A recent survey by Bicchi [1] covered over 140 papers, and many more than that have been published. Stemming from our desire to implement some of the work in grasp analysis for particular hand designs, we created an interactive graspi ..."
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Cited by 179 (20 self)
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Research in robotic grasping has flourished in the last 25 years. A recent survey by Bicchi [1] covered over 140 papers, and many more than that have been published. Stemming from our desire to implement some of the work in grasp analysis for particular hand designs, we created an interactive grasping simulator that can import a wide variety of hand and object models and can evaluate the grasps formed by these hands. This system, dubbed “GraspIt!,” has since expanded in scope to the point where we feel it could serve as a useful tool for other researchers in the field. To that end, we are making the system publicly available (GraspIt! is available for download for a variety of platforms from
Formulating Dynamic Multirigidbody Contact Problems with Friction as Solvable Linear Complementarity Problems
 NONLINEAR DYNAMICS
, 1997
"... A linear complementarity formulation for dynamic multirigidbody contact problems with Coulomb friction is presented. The formulation, based on explicit Euler integration and polygonal approximation of the friction cone, is guaranteed to have a solution for any number of contacts and contact config ..."
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Cited by 138 (22 self)
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A linear complementarity formulation for dynamic multirigidbody contact problems with Coulomb friction is presented. The formulation, based on explicit Euler integration and polygonal approximation of the friction cone, is guaranteed to have a solution for any number of contacts and contact configuration. A model with the same property is formulated for impact problems with friction and nonzero elasticity coefficient. An explicit Euler scheme based on these formulations is presented and is proved to have uniformly bounded velocities as the stepsize tends to zero for the NewtonEuler formulation in body coordinates.
RigidBody Dynamics With Friction and Impact,”
 SIAM Rev.,
, 2000
"... Abstract. Rigidbody dynamics with unilateral contact is a good approximation for a wide range of everyday phenomena, from the operation of car brakes to walking to rock slides. It is also of vital importance for simulating robots, virtual reality, and realistic animation. However, correctly modeli ..."
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Cited by 137 (1 self)
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Abstract. Rigidbody dynamics with unilateral contact is a good approximation for a wide range of everyday phenomena, from the operation of car brakes to walking to rock slides. It is also of vital importance for simulating robots, virtual reality, and realistic animation. However, correctly modeling rigidbody dynamics with friction is difficult due to a number of discontinuities in the behavior of rigid bodies and the discontinuities inherent in the Coulomb friction law. This is particularly crucial for handling situations with large coefficients of friction, which can result in paradoxical results known at least since Painlevé [C. R. Acad. Sci. Paris, 121 (1895), pp. 112115]. This single example has been a counterexample and cause of controversy ever since, and only recently have there been rigorous mathematical results that show the existence of solutions to his example. The new mathematical developments in rigidbody dynamics have come from several sources: "sweeping processes" and the measure differential inclusions of Moreau in the 1970s and 1980s, the variational inequality approaches of Duvaut and J.L. Lions in the 1970s, and the use of complementarity problems to formulate frictional contact problems by Lötstedt in the early 1980s. However, it wasn't until much more recently that these tools were finally able to produce rigorous results about rigidbody dynamics with Coulomb friction and impulses. Key words. rigidbody dynamics, Coulomb friction, contact mechanics, measuredifferential inclu sions, complementarity problems AMS subject classifications. Primary, 70E55; Secondary, 70F40, 74M PII. S0036144599360110 Rigid Bodies and Friction. Rigid bodies are bodies that cannot deform. They can translate and rotate, but they cannot change their shape. From the outset this must be understood as an approximation to reality, since no bodies are perfectly rigid. However, for a vast number of applications in robotics, manufacturing, biomechanics (such as studying how people walk), and granular materials, this is an excellent approximation. It is also convenient, since it does not require solving large, complex systems of partial differential equations, which is generally difficult to do both analytically and computationally. To see the difference, consider the problem of a bouncing ball. The rigidbody model will assume that the ball does not deform while in flight and that contacts with the ground are instantaneous, at least while the ball is not rolling. On the other hand, a full elastic model will model not only the contacts and the resulting deformation of the entire ball while in contact, but also the elastic oscillations of the ball while it is in flight. Apart from the computational complexity of all this, the analysis of even linearly elastic bodies in contact with a *
Nonconvex rigid bodies with stacking
 ACM Trans. Graph
"... We consider the simulation of nonconvex rigid bodies focusing on interactions such as collision, contact, friction (kinetic, static, rolling and spinning) and stacking. We advocate representing the geometry with both a triangulated surface and a signed distance function defined on a grid, and this d ..."
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Cited by 115 (12 self)
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We consider the simulation of nonconvex rigid bodies focusing on interactions such as collision, contact, friction (kinetic, static, rolling and spinning) and stacking. We advocate representing the geometry with both a triangulated surface and a signed distance function defined on a grid, and this dual representation is shown to have many advantages. We propose a novel approach to time integration merging it with the collision and contact processing algorithms in a fashion that obviates the need for ad hoc threshold velocities. We show that this approach matches the theoretical solution for blocks sliding and stopping on inclined planes with friction. We also present a new shock propagation algorithm that allows for efficient use of the propagation (as opposed to the simultaneous) method for treating contact. These new techniques are demonstrated on a variety of problems ranging from simple test cases to stacking problems with as many as 1000 nonconvex rigid bodies with friction as shown in Figure 1.
LINEAR COMPLEMENTARITY SYSTEMS
, 2000
"... We introduce a new class of dynamical systems called “linear complementarity systems.” The time evolution of these systems consists of a series of continuous phases separated by “events ” which cause a change in dynamics and possibly a jump in the state vector. The occurrence of events is governed ..."
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Cited by 79 (26 self)
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We introduce a new class of dynamical systems called “linear complementarity systems.” The time evolution of these systems consists of a series of continuous phases separated by “events ” which cause a change in dynamics and possibly a jump in the state vector. The occurrence of events is governed bycertain inequalities similar to those appearing in the linear complementarity problem of mathematical programming. The framework we describe is suitable for certain situations in which both differential equations and inequalities playa role; for instance, in mechanics, electrical networks, piecewise linear systems, and dynamic optimization. We present a precise definition of the solution concept of linear complementarity systems and give sufficient conditions for existence and uniqueness of solutions.
Timewarp rigid body simulation
 IN PROC. OF ACM SIGGRAPH
, 2000
"... The traditional highlevel algorithms for rigid body simulation work well for moderate numbers of bodies but scale poorly to systems of hundreds or more moving, interacting bodies. The problem is unnecessary synchronization implicit in these methods. Jefferson´s timewarp algorithm (Jefferson 85) is ..."
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Cited by 64 (0 self)
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The traditional highlevel algorithms for rigid body simulation work well for moderate numbers of bodies but scale poorly to systems of hundreds or more moving, interacting bodies. The problem is unnecessary synchronization implicit in these methods. Jefferson´s timewarp algorithm (Jefferson 85) is a technique for alleviating this problem in parallel discrete event simulation. Rigid body dynamics, though a continuous process, exhibits many aspects of a discrete one. With modification, the timewarp algorithm can be used in a uniprocessor rigid body simulator to give substantial performance improvements for simulations with large numbers of bodies. This paper describes the limitations of the traditional highlevel simulation algorithms, introduces Jefferson´s algorithm, and extends and optimizes it for the rigid body case. It addresses issues particular to rigid body simulation, such as collision detection and contact group management, and describes how to incorporate these into the timewarp framework. Quantitative experimental results indicate that the timewarp algorithm offers significant performance improvements over traditional highlevel rigid body simulation algorithms, when applied to systems with hundreds of bodies. It also helps pave the way to parallel implementations, as the paper discusses.
TimeStepping for ThreeDimensional Rigid Body Dynamics
, 1998
"... This paper considers a wide number of timestepping methods, and discusses their implications for convergence theory and the nature of the limiting solutions. ..."
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Cited by 62 (20 self)
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This paper considers a wide number of timestepping methods, and discusses their implications for convergence theory and the nature of the limiting solutions.
Contactaware nonlinear control of dynamic characters
 ACM Transactions on Graphics (Proc. SIGGRAPH
, 2009
"... Dynamically simulated characters are difficult to control because they are underactuated—they have no direct control over their global position and orientation. In order to succeed, control policies must look ahead to determine stabilizing actions, but such planning is complicated by frequent ground ..."
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Cited by 48 (7 self)
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Dynamically simulated characters are difficult to control because they are underactuated—they have no direct control over their global position and orientation. In order to succeed, control policies must look ahead to determine stabilizing actions, but such planning is complicated by frequent ground contacts that produce a discontinuous search space. This paper introduces a locomotion system that generates highquality animation of agile movements using nonlinear controllers that plan through such contact changes. We demonstrate the general applicability of this approach by emulating walking and running motions in rigidbody simulations. Then we consolidate these controllers under a higherlevel planner that interactively controls the character’s direction.