Stiction modeling: first order differential equation approximation for nonholonomic inequality constraint

Current trends in computational multibody dynamics address stiction between rigid bodies by using the complementarity conditions of optimization theory to develop the unilateral constraint. This paper presents an alternative Newtonian approach employing a nonhomogenous first order differential equation to approximate joint kinematics of a nonholonomic inequality constraint. A stiction algorithm is developed as a function of joint displacement, velocity and a kinematic state variable defined by the first order dynamic equation. System topology remains constant during stiction as the formulation computes proper stick-slip reaction loads. The technique is demonstrated for contacting bodies in lateral motion and offers a smooth approximation for stiction in mechanical systems analyzed by standard ODE and DAE stiff integrators.