W. S. Howard and V. Kumar, "A minimum principle for the dynamic analysis of systems with frictional contacts," in Proc. of the 1993.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....algorithms that would accurately compute fixturing arrangements, fixture geometries, fixture reaction forces, and fixtured object deflections from CAD models, these shortcomings of the linear spring model are significant. Several researchers, such as Sinha and Abel [18] and Howard and Kumar [6] suggest an approach resembling finite elements. The contact regions are discretized into a number of small elements and elasticity theory is invoked to find the relative displacement of the contacting objects. While this approach is accurate, the complicated procedure has a number of drawbacks. ....

W. S. Howard and V. Kumar. A minimum principle for the dynamics analysis of systems with frictional contacts. In Proc. Int. Conf. on Robotics and Automation, pages 437-- 442, Atlanta, GA, May 1993.

.... and the friction forces obey Coulomb s Law, then the motion of the system cannot always be uniquely predicted (see for example see [2, 13, 24] If, on the other hand, the bodies are assumed to be compliant, then the motion of the system and the contact forces can always be uniquely predicted [11, 43]. This feature is desirable when it comes to simulation and planning. However, predictions rely on estimates of the effective compliance and friction coefficients at each contact. The compliance coefficients can be determined through finite element analyses, but due to the computational demand, ....

W. S. Howard and V. Kumar. A minimum principle for the dynamic analysis of systems with frictional contacts. In Proceedings, IEEE International Conference on Robotics and Automation, May 1993.

.... (A) that are subject to nonlinear con straints it is attractive to pursue models in which the contact forces are explicit functions of the state variables (q 0) A continuum model for modeling the deformations at each contact is described in [11] This general approach is further refined by [12]. Existence and uniqueness is shown for the special case in which the maximum tangential force at each point is a priori known. The disadvantage in this approach is the complexity of the model. The contact models lead to a high dimensional, stiff system of equations and a run time that is ....

W. S. Howard and V. Kumar, "A minimum principle for the dynamic analysis of systems with frictional contacts," in Proc. of the 1993.

....model for modeling the deformations at each contact is described in [18] Each contact is modeled as a frictional elastic or viscoelas tic contact, and the contact force distribution across the contact patch is calculated using a finite element mesh. This general approach is further refined by [19]. Existence and uniqueness is shown for the special case in which the maximum tangential force at each point is a priori known. The disadvantage in this approach is the complexity of the model. The contact models lead to a high dimensional, stiff system of equations and a run time that is ....

....of the model. The contact models lead to a high dimensional, stiff system of equations and a run time that is unacceptable for real time simulation. It turns out that simplified lumped models of com pliance at each contact (such as the one shown in Figure 1) yield reasonably accurate results [19, 20, 21] without increasing the computations significantly. They provide a framework for analyzing frictional forces for statically indeterminate systems that are otherwise intractable. Finally, as shown in the next section, the uniqueness and existence can be proved for such models. A compliant model for ....

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W. S. Howard and V. Kumar, "A minimum principle for the dynamic analysis of systems with frictional contacts," in Proc. of the i993 IEEE Izt'l Cozf. oz Robotzcs azd Automatzoz, vol. 1, pp. 437 442, 1993.

....modeled as frictional elastic or viscoelastic, and the contact force distribution across the contact patch is calculated using a finite element mesh. Wang, Kumar, and Abel [23, 25] performed a dynamic analysis of enveloping grasps using this framework. This general approach is further refined by [6]. Existence and uniqueness is shown for the special case in which the maximum tangential force at each point is a priori known. This socalled boundary element approach and its variations can also used in dynamic analysis of impacts [21, 23, 25] In contrast, Mirtich et al. 14] propose efficient, ....

W. S. Howard and V. Kumar. A minimum principle for the dynamic analysis of systems with frictional contacts. In Proc. of the

....a continuum model for modeling the deformations at each contact is described in [23] Each contact is modeled as frictional elastic or viscoelastic, and the contact force distribution across the contact patch is calculated using a finite element mesh. This general approach is further refined by [6]. Existence and uniqueness is shown for the special case in which the maximum tangential force at each point is a priori known. The empirical nature of friction models can cause additional difficulties with dynamic simulation. The most widely employed model, for example, is Coulomb friction. When ....

W. S. Howard and V. Kumar. A minimum principle for the dynamic analysis of systems with frictional contacts. In Proc. of the

....a continuum model for modeling the deformations at each contact is described in [32] Each contact is modeled as frictional elastic or viscoelastic, and the contact force distribution across the contact patch is calculated using a finite element mesh. This general approach is further refined by [12]. Existence and uniqueness is shown for the special case in which the maximum tangential force at each point is a priori known. The disadvantage in this approach is the complexity of the model. The contact models lead to a high dimensional, stiff system of equations and a run time that is ....

W. S. Howard and V. Kumar. A minimum principle for the dynamic analysis of systems with frictional contacts. In Proc. of the 1993 IEEE Int'l Conf. on Robotics and Automation, volume 1, pages 437--442, 1993.

....a continuum model for modeling the deformations at each contact is described in [32] Each contact is modeled as frictional elastic or viscoelastic, and the contact force distribution across the contact patch is calculated using a finite element mesh. This general approach is further refined by [12]. Existence and uniqueness is shown for the special case in which the maximum tangential force at each point is a priori known. The disadvantage in this approach is the complexity of the model. The contact models lead to a high dimensional, stiff system of equations and a run time that is ....

W. S. Howard and V. Kumar. A minimum principle for the dynamic analysis of systems with frictional contacts. In Proc. of the 1993 IEEE Int'l Conf. on Robotics and Automation, volume 1, pages 437--442, 1993.

....is reasonable to use rigid body models. However, if there are two or more contacts, it is necessary to consider all contacts concurrently. 3 Compliant contact models We pursue a compliant contact model that incorporates mechanisms for energy storage and for energy dissipation at the contact. In [20], the benefits of using a model with a spring in the normal direction and another in the tangential direction were demonstrated. This lumped parameter model eliminates the problems of existence and uniqueness which arise when the rigid body assumption is used in conjunction with Coulomb friction. ....

W. S. Howard and V. Kumar, "A minimum principle for the dynamic analysis of systems with frictional contacts," in Proceedings of the 1993 IEEE International Conference on Robotics and Automation, vol. 1, pp. 437--442, 1993.

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