🤖 AI Summary
This study addresses the challenge of dynamic modeling for mechanisms with variable topology, particularly when constraints such as joint locking, static friction, or ideal contact lead to abrupt changes in degrees of freedom. To ensure physically consistent and continuous dynamic behavior during topological transitions, the work proposes a set of physically coherent switching conditions. Building upon this foundation, two nonsmooth dynamics frameworks are developed: one based on redundant coordinates employing projected equations of motion, and another using minimal coordinates formulated via Voronets equations. The computational characteristics of both approaches are systematically compared. The proposed methodology is successfully validated on a planar 3R mechanism and a 6-DOF industrial manipulator under joint-locking scenarios, significantly enhancing the accuracy and feasibility of forward dynamics simulations for complex systems with varying topology.
📝 Abstract
Many mechanical systems exhibit changes in their kinematic topology altering the mobility. Ideal contact is the best known cause, but also stiction and controlled locking of parts of a mechanism lead to topology changes. The latter is becoming an important issue in human-machine interaction. Anticipating the dynamic behavior of variable topology mechanisms requires solving a non-smooth dynamic problem. The core challenge is a physically meaningful transition condition at the topology switching events. Such a condition is presented in this paper. Two versions are reported, one using projected motion equations in terms of redundant coordinates, and another one using the Voronets equations in terms of minimal coordinates. Their computational properties are discussed. Results are shown for joint locking of a planar 3R mechanisms and a 6DOF industrial manipulator.